Accepted Manuscript Synthesis, characterization, molecular modeling and antioxidant activity of Girard′s T thiosemicarbazide and its complexes with some transition metal ions O.A. El-Gammal, M.M. Mostafa PII: DOI: Reference:

S1386-1425(14)00165-6 http://dx.doi.org/10.1016/j.saa.2014.02.001 SAA 11620

To appear in:

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Received Date: Revised Date: Accepted Date:

5 December 2012 29 November 2013 2 February 2014

Please cite this article as: O.A. El-Gammal, M.M. Mostafa, Synthesis, characterization, molecular modeling and antioxidant activity of Girard′s T thiosemicarbazide and its complexes with some transition metal ions, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http://dx.doi.org/10.1016/j.saa. 2014.02.001

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Synthesis, characterization, molecular modeling and antioxidant activity of Girard′s T thiosemicarbazide and its complexes with some transition metal ions O. A. El-Gammal*and M. M. Mostafa Department of Chemistry, Faculty of Science, Mansoura University, Mansoura,35566, P.O.Box 70, Mansoura- Egypt Abstract The chelation behavior of N-{[(allylamino) thiomethyl] hydrazinocarbonylmethyl} trimethylammonium chloride (H3ATHC) towards VO2+, Co 2+, Ni2+, Cu2+, Zn2+ and UO22+ ions have been studied. The structures of the complexes were elucidated using elemental analyses, spectral (IR, UV-visible, 1H-NMR and ESR and mass) as well as magnetic and thermal measurements. The ligand acted as ON bidentate, ONS tridentate donor forming mononuclear complexes. A tetrahedral geometry for Co2+, square-planar for Ni2+ and Cu2+, an octahedral for Zn2+ and a square-pyramidal arrangement for VO2+ complexes were proposed, respectively. The EPR spectra of Cu2+ and VO2+ complexes confirmed the suggested geometries with values of α 2 and β

2

indicating that the in-plane σ-

bonding and in-plane π-bonding are appreciably covalent, and were consistent with very strong in-plane σ−bonding in the complexes. Also, the bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated. Also, the thermal behavior and kinetic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. Furthermore, the synthesized compounds were screened for their superoxide-scavenging activity in the PMS/NADH-NBT system as well as their scavenging effect on ABTS (2,2′-azino-bis(3-ethyl benzthiazoline-6-sulfonic acid) and 2,2- diphenyl-1-picrylhydrazyl(DPPH) radicals. Among these compounds, the ligand and Zn2+ complex, exhibited the potent ABTS (2,2′-azino-bis(3-ethyl benzthiazoline-6sulfonic acid) radical scavenging activity, comparable to that of vitamin C. e-mail: [email protected]

Tel: 002-0126712958

Keywords: G.T thiosemicarbazide, thermal, modeling, DPPH, ABTS and superoxide dismutase.

1.Introduction Over the last decades, Girard′s T and P reagents as well as their Schiff -bases have been extensively studied owing to their numerous applications in pharmacy, analytical

and applied chemistry. The reagents were used for

isolation

and

identification of hormones in applied chemistry. The reagents were used for isolation and identification of hormones, ketosteroids in urine and blood [1], pre-concentration and separation of ketones from essential [2] and crude oils [3]. Also, they were utilized in chromatographic determination of several metal [4] and facilitated the cathodic deposition of zirconium [5]. Moreover, the reagents and their hydrazones were widely used as corrosion inhibitors of some metals [6,7]. Finally, in view of the fact that these reagents as well as their Schiff-bases possess ligation atoms that many reports concerning their coordination behavior were published [8-10]. On continuation of our work [11], we describe herein the synthesis, spectral and thermal studies of new series of transition metal complexes of some N-{[(allylamino) thiomethyl] hydrazinocarbonylmethyl}

trimethyl

ammonium

chloride

(H3ATHC).

The

degradation kinetics have been studied by Coats-Redfern and Horowitz-Metzger methods. Thermodynamic parameters (∆S, ∆H and ∆G), have been evaluated using the standard equations. Finally, the scavenging effects of all compounds on free radical are evaluated. Recently, antioxidants that exhibit ABTS radical scavenging activity are increasingly receiving attention. Literature survey shows no studies of the radical scavenging of the thiosemicarbazide under investigation has yet been undertaken. Accordingly, a study of new thiosemicarbazide derivative with antioxidant activity would support the development of new drugs and improve the treatment of various diseases.

2. Experimental 2.1. Instrumentation and materials All the chemicals were purchased from Aldrich and Fluka and used without further purification. Elemental analyses (C, H, N) were performed with a Perkin-Elmer 2400 series II analyzer. Molar conductance values (10-3 mol L-1) of the complexes in DMF were measured using a Tacussel conductivity bridge model CD6NG. IR spectra (4000400 cm-1) in KBr discs were recorded on a Mattson 5000 FTIR spectrometer. Electronic spectra were recorded on a Unicam UV-Vis spectrophotometer UV2. Magnetic

susceptibilities were measured with a Sherwood scientific magnetic susceptibility balance at 298 K. 1H-NMR measurements in d 6-DMSO were carried out on a Varian Gemini WM-200 MHz spectrometer at the Micro Analytical Unit, Cairo University. Mass spectra were recorded on a Varian Mat 311 at the National Research Center, Cairo. Thermal measurements (TGA, DTA, 20-1000 oC) were recorded on a DTG-50 Shimadzu thermogravimetric analyzer at a heating rate of 10oC/min and nitrogen flow rate of 20 ml/min. ESR spectra were obtained on a Brucker EMX spectrometer working in the X-band (9.78 GHz) with 100 kHz modulation frequency. The microwave power and modulation amplitudes were set at 1 mW and 4 Gauss, respectively. The low field signal was obtained after 4 scans with 10 fold increase in the receiver again. A powder spectrum was obtained in a 2 mm quartz capillary at room temperature.

2.2. Synthesis of H3ATHC H3ATHC was synthesized as reported earlier [11]. The compound checked by its m.p., 205-210 oC, IR and 1H-NMR spectra.

2.3. Synthesis of complexes Ethanolic or aqueous-ethanolic solution of H3ATHC (0.266 g, 1.0 mmol) and hydrated metal acetate salts (Co, Ni, Cu, Zn and uranyl) and vanadyl sulphate (1.0 mmol) were heated under reflux for 2-3 h. The precipitates formed were filtered off, washed with ethanol followed by diethyl ether and dried in a vacuum desiccator over anhydrous CaCl2. 2.4.Antioxidant Studies The antioxidant activity assay[12] employed is a technique depending on measuring the consumption of stable free radicals i.e.evaluate the free radical scavenging acvtivity of the investigated component. The methodology assumes that the consumption of the stable free radical (X') will be determined by reactions as follows: X' + YH→ XH + Y' The rate and / or the extent of the process measured in terms of the decrease in X' concentration, would be related to the ability of the added compounds to trap free radicals. The decrease in color intensity of the free radical solution due to scavenging of the free radical by the antioxidant material is

measured spectrometric at a specific wavelength. The assay employs the radical cation

derived

from

2,

2-

Azino-bis(3-ethylBenzthiazoline-6-sulfonic

acid)(ABTS)ordiphenylpicrylhydrazyl (DPPH) as stable free radical to assess antioxidant and extracts. Inhibition free radical DPPH or ABTS in percent (I %) was calculated as in Eq: I% = (Ablank – Asample) / (Ablank) ×100 Where Ablank is the absorbance of the control reaction (containing all reagents except the test compound), and Asampleis the absorbance of the test sample. 2.4.1.DPPH free radical scavenging activity. Different concentrations of the chemical compounds were dissolved in methanol to obtain final concentration ranged from 6.25 to 200 mg/mL to determine IC50 (concentration make 50% inhibition of DPPH color). 50 µl of various sample concentrations were added to 5 mL of 0.004% methanolic solution of DPPH. After a 60 min of incubation at dark, the absorbance was read against a blank at 517 nm. 2.4.2.ABTS free radical scavenging activity The reaction mixture consists of 2 ml of 2,2′-azino-bis-(3-ethyl benzthiazoline-6-sulfonic acid) (ABTS) solution (60 µl) and 3 ml of MnO2 solution (25 mg/ml), all prepared in phosphate buffer (pH = 7). The mixture was shaken, centrifuged and decanted. The absorbance (A control) of the resulting greenblue solution (ABTS+ radical solution) was recorded at λmax = 734 nm. The absorbance (Atest) was measured upon the addition of 20 µl of 1 mg/ml solution of the tested compounds sample in MeOH /buffer (1:1 v/v) to the ABTS solution. The decrease in absorbance is expressed as % inhibition. L-ascorbic acid was used as standard antioxidant (positive control). Blank sample was run without ABTS and using MeOH/phosphate buffer (1:1) instead of tested compounds.

Negative control was run with ABTS and MeOH/phosphate buffer (1:1) only [13-15].

2.4.3.Superoxide dismutase (SOD)scavenging activity

SOD activity of the investigated compounds was assayed by using phenazen methosulfate (PMS) to photogenerate a reproducible and constant flux of superoxide anion radicals at pH=8.3 (phosphate buffer). Reduction of nitroblue tetrazolium(NBT) to blue formazan was used as an indicator of O 2production and followed spectrophotometrically at 560 nm. The addition of PMS (9.3 x 10-4M) to an aqueous solution of NBT (3.0x 105 M), NADH (nicotine amide adinine dinucloted, 4.7x 10 -4M) and phosphate buffer (final volume of 2 ml) caused a OD(∆

560)/

min change. The reaction in blank

samples and in presence of the compounds under study was measured for 3 minutes. 2.5. Molecular modeling

An attempt to gain a better insight on the molecular structure of the ligand and its complexes, geometric optimization and conformational analysis has been performed using using the programDMOL3[16-20] in Materials Studio package [21] which is designed for the realization of large scale density functional theory (DFT) calculations. DFT semi-core pseudopods calculations (dspp) were performed with the double numerica basis sets plus polarization functional (DNP). The DNP basis sets are of comparable

quality to 6-31G Gaussian basis sets [22] Delley et al. showed that the DNP basis sets are more accurate than Gaussian basissets of the same size [1620]. The RPBE functional [23] is so far the best exchange-correlation functional [24] based on the generalized gradient approximation(GGA), is employed to take account of the exchange and correlation effects of electrons. The geometric optimization is performed without any symmetry restriction. 3. Results and discussion

The formulae of the complexes, physical properties, elemental analysis and formula weights obtained for some complexes from mass spectra are listed

in Table 1. The isolated complexes, except [VO(H 3ATHC)(SO4)]2H 2O complex, are quite stable in air, non-hygroscopic and insoluble in water and most organic solvents but soluble in DMF and DMSO. The molar conductivity in DMF solution at 25 °C for all complexes in general are in the 11-20 ohm-1 cm2 mol-1 range indicating non-electrolytic nature [25].

3.Results and Discussion 3.1. Molecular modeling The molecular structure along with atom membering of H 3ATHC and its metal complexes are shown in structures (I-VI). The obtained data are calculated using quantum mechanics for the complexes, except VO2+ complex, Semi-emperical Molecular Mechanics Optimization method is used. A glance at data in Tables S1-S15 indicates the following remarks: 1- The bond angles of the thiosemicarbazide moiety are altered somewhat upon coordination, the largest change affects S5-C6-N7 and N1-C6-S5 angles which are either increased from 123.9° in metal free ligand to 126.3° or reduced from121.4° to 100° in complexes as a consequence of bonding. 2- The bond angles within the thiosemicarbazone backbone do not change significantly but the angles around the metal undergo appreciable variations upon changing the metal center. 3- N4-N1-C6 and O2-C3-N4 angles changes from 117.8°, 120.7° to (113°-130.5°) and (122.9°-115°) in complexes due to formation of N2M-O3 chelate ring [26]. 4-

All

bond

angles

in

[Co(HATHC)(H 2O]H2O

and

[Ni(H2ATHC)(OAc)(H2O)]H2O complexes are quite near to a tetrahedral geometry predicting sp3 hybridization. On the other hand, [Cu(H 2ATHC)(OAc)(H2O)]H 2O complex afforded a square-planar geometry

predicting

dsp2

hybridization

while

[Zn(H2ATHC)(EtOH)(OH)]

and

[UO2(H2ATHC)(OAc)]2H2O

complexes assigned an octahedral geometry. 5- All of the coordinating bonds are as expected, longer than that in the ligand. C7-N2 bond length is more shortened as a result of double bond formation [27]. Coordination slightly shortness C6-S5 bond length in [Zn(H 2ATHC)(EtOH)(OH)] and [UO 2(H2ATHC)(OAc)]2H 2O complexes on coordination via thione S atom revealing the weakness of Zn-S (2.352Ǻ)and U-S (2.508 Ǻ) bonds. 6- There is a large variation in N5-N2 bond lengths on complexation. It becomes slightly longer as the coordination takes place via N atoms of (–C=N-C=N-) group that is formed on deprotonation of the enolized (C=O) and thiol C=S groups in [Cu(H2ATHC)(OAc)(H 2O)]H2O and [Ni(H2ATHC)(OAc)(H 2O)]H2O complexes. 7-The lower HOMO energy values shows that molecules donating electron ability is the weaker. On contrary, the higher HOMO energy implies that the molecule is a good electron donor. LUMO energy presents the ability of a molecule receiving electron [27].

3.2. IR Spectra The most important IR bands of H 3ATHC (Structure I) and its complexes with probable assignments are given in Table 2. A comparison of the spectra of H3ATHC and its complexes reveals that the ligand coordinates in thione and thiol forms. H 3ATHC shows bands at 3210, 3164, 3100, and 1706 cm-1 assigned to ν(N 1H), ν(N2H), ν(N4H) and ν(C=O)stretching vibration modes, respectively. The two strong bands assignable to ν(C=S) and combination of ν(CS-CN) appear at 1222 and 730 cm-1 [28, 29]. The

medium intensity band at 964 cm-1 referred to ν(N-N) vibration [29]. The doublets at 2900 and 2970 cm-1 are attributed to symmetric and asymmetric stretching vibrations of S-CH2-CH=CH2 group. The absence of any bands in 1900-2100 cm-1 and 2300-2500 cm-1 region suggests the obscure of intramolecular hydrogen bonding N-H---O [30].The possibility of thione/thiol tautomerism in the solid state is ruled out, since no characteristic for thiol group (2500-2650 cm-1) is observed in the spectrum of the ligand [31].

Structure I: H 3ATHC In

[Ni(H2ATHC)(OAc)]2H2O

and

[Cu(H2ATHC)(OAc)(H2O)]H 2O

complexes (structures II and III), H 3ATHC behaves as NO mononegative bidentate coordinating via the deprotonated enolic carbonyl (C-O) and (N2H) centers. This is confirmed by the disappearance of the (C=O) and (N2H) bands with simultaneous appearance of new bands at 1123, 1575 and 1124 , 1557 cm-1 in the IR spectra of the first and second complexes assigned to ν(C-O) and ν(C=N)*, respectively [32]. The appearance of new bands at 491, 500 and 451, 450 cm-1 assignable to ν(M-O) and ν(M-N) vibrations supports the mode of chelation [30]. Finally, the broad band appeared at 1557 cm-1 in the spectrum of Cu2+ complex which may be considered as an overlap of ν(C=N)* with νas(OCO) and 1394 cm-1 assignable to νs(OCO) affording wave-number separation value (∆ = 163 cm-1) characteristic for monodentate acetate anion [33]. On the other hand,

the appearance of two new bands at ≈ 1549 and ≈ 1442 cm-1 (∆ = 107 cm-1) in the IR spectrum of Ni2+ complex is characteristic of bidentate acetate group [34].

Structure II: [Ni (H2ATHC)(OAc)]2H2O

Structure III: [Cu(H 2ATHC)(OAc)(H2O)]H 2O The IR spectrum of [Co(HATHC)(H2O)]H2O complex (structure IV) shows that the ligand coordinates in the thiol-enol form νia (C-O), (C=N*) and (C-S) groups. This is revealed by the disappearance of (C=O), (N 1H), (C=S) and (N 2H) bands with the appearance of new bands at 1124, 1571 and 664 cm-1 attributed to ν(C=N*-N=C), ν(C-O) [35] and ν(C-S) vibrations, respectively. Moreover, the presence of new bands at 485 and 446 cm-1

due to ν(Co-O) and ν(Co-N) vibrations confirm the proposed mode of coordination.

Structure IV: [Co(HATHC)(H2O)]H 2O In [UO2(H2ATHC)(OAc)]2H2O

and

[Zn(H 2ATHC)(H2O)(EtOH)

(OH)]H 2O complexes, (structures V, VI), H3APTHC behaves as NOS mononegative tridentate coordinating through (C-O), (N 2H) and S atom of C=S groups. Strong evidence arises from the following observations: i) the disappearance of (C=O) and (N2H) bands with the appearance of new bands at 1590, 1598 and 1120, 1125cm-1 assignable to (C=N*) and ν(C-O) in the spectra of the first and second complexes, respectively. ii) the shift of the band due to (N2H) in both complexes to lower wave-number; iii) the weakness of ν(C=S) band.; iv) the IR spectrum of UO 22+ exhibits two new bands at 1527 and 1348 cm-1 with (∆ = 99 cm-1) suggesting a bidentate nature of acetate group.; v) the appearance of new bands at 522,485 and 476, 445 cm-1 assignable to of ν(M-O) and ν(M-N) vibrations. Moreover, the IR spectrum of UO22+ complex displays bands at 932 and 856 cm-1 assigned to ν3 and ν1 vibrations, respectively of the dioxo-uranium [36]. The ν3 value was used to calculate the force constant (F) of (U=O) [37] by the following equation: (ν3)2= (1307)2(FU-O) ⁄ 14.103

(1)

Which was then substituted into the Jones relation [32]:

RU-O = 1.08(FU-O)1/3 + 1.17

(2)

The calculated FU-O and RU-O were 7.171mdynesẪ-1 and 1.730 Ẫ, respectively, failing within the usual range for uranyl complexes [37] and extremely in accordance with the bond length calculated by the use of MM+ force field (as implemented in DFT molecular modeling ) .

Structure V: [Zn(H2ATHC)(H2O)(EtOH) (OH)]H2O

Finally, H3ATHC coordinates as a neutral molecule in thione-keto form νia (C=O) and (N2H) groups (structure VI). This behavior is found in [VO(H3ATHC)(SO4)]2H2O complex. This mode of complexation is supported by the following remarks: i) the weakness of bands due to the (N2H) and (C=O) bands, respectively.; ii) the bands located at 1198, 1040, 976 and 441 cm-1 are due to ν3 ,ν1, ν4 and ν2 of the sulphate ion suggesting a bidentate nature [34]. In addition, the band at 976 cm-1 in the spectrum is characteristic for ν(V=O) stretching vibration [38] which overlapped with ν2 of SO42- group.

Structure VI: [UO2(H2ATHC)(OAc)]2H2O

Structure VII: [VO(H2ATHC)(SO 4)]2H 2O The broad bands at ≈ 3399-3454, 868-850, and at ≈ 567cm-1 in the IR spectra of the investigated complexes are referred to ν(OH), ∆(H2O), pr (H2O) and Pw (H2O) vibrations for the coordinated water. The broad band centered at 3500 cm-1 in the spectra of the studied complexes may be due to hydrated water.

This notification will be supported by thermal

analysis. 3.3. 1H-NMR The 1H-NMR spectrum of H 3ATHC in d6-DMSO shows two singlet signals at δ=10.87and 9.43ppm, are assignable to N 1H and N 4H protons,

respectively. The signals due to N2H appears as a triplet signal centered at 8.54ppm.The two signals at 3.26 and 3.43ppm with ratio 3:2 are attributable to the protons of CH 3 and CH 2 (N.CH2), respectively. In addition, the quartet signal at 5.05 ppm and the doublet at 4.27 ppm are assignable to the protons of CH 2 (-NH- CH2) and CH 2(CH=CH 2), respectively. Moreover, the sexet signal centered at 5.8 ppm is assigned to the protons of the allyl CH group. Finally, the absence of SH signal in the downfield region confirms the existence of H3ATHC in solution in thione form [32].

In case of Zn(II) complex, the proposed mode of coordination is further supported by the 1H-NMR spectrum of the Zn2+ complex recorded in d6DMSO. It showed no signal due to N1H proton suggesting deprotonation of C-OH group that is formed on enolization. Also, the shift of signals due to N2H and N 4H protons to upfield confirms the coordination via N2H and C=S groups.

3.4. Electronic spectra and magnetic moments The magnetic moments and the significant electronic absorption bands of H3ATHC and its complexes, in DMF and Nujol mull, are given in Table 3. The electronic spectra of the complexes are dominated by intense intraligand charge-transfer bands. The ligand shows two broad bands at 36764 and 34246 cm-1, presumably arising for π → π* and n → π* transitions [37,39]. Large change is observed on the spectra of its complexes with a new n→ π* band at 33112-32467 cm-1. Another n → π* band in the spectrum is also observed in the spectra of its complexes at 26316-28089 cm-1. The electronic spectrum of [Co(HATHC)(H2O)] exhibits a well defined bands at 14705 and 16556 cm-1. The second band is assigned to 4A2(F) → 4

T1(F)(ν3) transition characteristic for tetrahedral geometry. The band in the

region 4500-7500 cm-1 cannot be observed due to restriction of our equipment. The dark green color is an additional evidence for this structure. The values of ligand field parameters (D q, B and β) are 302 cm-1, 712 cm-1 and 0.73 which are typical for tetrahedral Co 2+ [39]. The value of β indicates the covalent character for the Co(II) ligand bonds [41]. On the other hand, the spectrum of [Ni(H 2ATHC)OAc]2H2O shows a little change in the band energies. The bands at 18382 and 15625 cm-1 are assigned to 3T1→3T1(P) transition, indicating a tetrahedral geometry.The violet color as well as the magnetic moment of 4.08 B.M.are a further support for the tetrahedral structure. The electronic spectrum of [Cu(H 2ATHC)(OAc)H 2O]H2O exhibits two bands, one centered at 14492 cm-1 and a more intense band at 27778 cm-1, respectively. The first band is due to 2B1g → 2A1g and 2B1g → 2Eg transitions appears as broad or weak shoulders and the second band is assignable to a symmetric forbidden ligand-metal charge-transfer [41,42]. Also, the µeff value (1.78 B.M.) with the position of bands in the electronic spectrum is consistent with monomeric square planar Cu(II) complexes [43]. The spectrum of [UO 2(H2ATHC)(OAc)]2H 2O complex exhibits two bands in its spectrum, the first one at 29239 cm-1 due to charge transfer, probably H3ATHC

O=U=O, while the second band at 23696 cm-1 can be

definitely assigned to the 1Σ+g

2π4

transition [44]. This is in

accordance with an octahedral geometry [45].

Finally, the electronic spectrum of [VO(H 3ATHC)(SO4)]2H 2O exhibits a band at 13157 cm-1 assignable to 2B2 → 2E(ν1) transition in a square-pyramid configuration [46]. The existence of the band at 976 cm-1 in the IR spectrum of VO2+ complex and the color (dark green) are good evidence for the proposed structure. The magnetic moment (1.87 B.M.) fall within the range reported

for

mono-nuclear

complex.

The

structures

of

[Cu(H 2ATHC)(OAc)H 2O]H2O and [VO(H 3ATHC)(SO4)]2H 2O complexes will be further confirmed by EPR measurement.

3.5. Electron spin resonance ESR spectra of Cu2+ and VO2+ complexes were recorded in the solid state. The spin Hamiltonian parameters of the complexes were calculated and summarized in Table 4. The room temperature solid state ESR of the [Cu(H 2ATHC)(OAc)(H2O)]H 2O complex exhibits an axially symmetric g-tensor parameters with g|| > g⊥>2.0023 indicating that the copper site has dx2-y2 ground state characteristic of square-planar, or octahedral stereochemistry [47]. In axial symmetry the g-values are related by the expression, G= (g|| -2/ g⊥-2) = 4. The calculated G value for the present Cu2+ complex is less than 4 suggesting copper-copper interactions [48]. A forbidden magnetic dipolar transition for [Cu(H 2ATHC)(OAc)H 2O]H2O complex is not observed at half-field (ca. 1600 G, g≈ 4.0) confirming the uni-molecular nature of the complex [48]. The EPR spectrum of the complex exhibits a broad single line, nearly isotropic signal centered at g=2.06 (Fig.1) which is attributable to dipolar broadening and enhanced spin lattice relaxation [49]. This line broadening is probably due to insufficient spin-exchange narrowing toward the coalescence of four copper hyperfine lines to a single line. Note that, the same kind of powder EPR line shapes, have also been observed for many distortedtetragonal Cu2+ complexes [50]. An index of the increase of the tetrahedral distortion in the coordination sphere is the decrease of A|| with an increase of g|| [51]. To quantify the degree of distortion of the Cu2+ complexes, the f-factor g|| /A|| was calculated which is considered as an empirical index of tetrahedral distortion [51]. Its value ranges between 105 and 135 for square-planar complexes, depending on the nature of the coordinated atoms. In the

presence of a distorted-tetrahedral structure, the values can be much larger [52]. For the studied complex the factor was 157 demonstrating the existence of significant dihedral angle distortion in the xy-plane and indicating a tetrahedral distortion from square-planar geometry. The results are consistent with distorted-tetragonal geometry around the copper site. Molecular orbital coefficients, α2 (a measure of the covalency of the in-plane σ-bonding between a copper 3d orbital and the ligand orbitals) and β2 (covalent in-plane π-bonding), were calculated by using the following equations [53-56]:

α2 = (A|| /0.036) + (g|| – 2.0023) + 3/7(g⊥ – 2.0023) + 0.04 β 2 = (g|| – 2.0023) E/ –8λα 2

(4) (5)

Where λ = -828 cm–1 for the free copper ion and E is the electronic transition energy. The covalency of the in-plane σ-bonding, α2= 1 indicates complete ionic character, whereas α2 = 0.5 denotes 100% covalent bonding, with the assumption of negligibly small values of the overlap integral. The β 2 parameter gives an indication of the covalency of the in-plane π-bonding. The smaller the β 2 the larger is the covalency of the bonding. The values of α2 and β 2 for the complex indicates that the in-plane σ-bonding and in-plane π-bonding are appreciably covalent, and are consistent with very strong in-plane σ−bonding in this complex. For the Cu(II) complexes, the high values of β 2 compared to α2 indicate that the inplane π-bonding is less covalent than the in-plane σ-bonding. These data are well consistent with other reported values [54-57]. On the other hand, the room temperature EPR spectrum of [VO(H 3ATHC)(SO4)]2H 2O complex shows a typical eight-line pattern (Fig.1) similar to those reported for mononuclear vanadyl molecule. Also, the spectrum shows the parallel and the perpendicular features which indicates axially symmetric anisotropy with

well resolved sixteen-lines hyperfine splitting characteristic for the interaction between the electron and the vanadium nuclear spin (I=7/2). The spin Hamiltonian parameters are calculated and given in Table 4. A glance at this table indicates that the unpaired electron (d1) of the investigated complex is present in the dxy with square-pyramidal or octahedral geometry [58, 59]. The values obtained agree well with the g-tensor parameters reported for square-based pyramidal complexes [60]. The molecular orbital coefficient α 2 and β 2 for [VO(H3ATHC)(SO 4)]2H2O complex was calculated using the following equations [61]: A|| = – pk –4 β 2p/7– (ge – g|| )p– 3(ge – g⊥ )p/7

(6)

A|| =–pk–2β 2p/7–11(g e –g||) p/14

(7)

(ge – g||)=8α 2β 2λ/Ε

(8)

Neglecting the second order effects and taking the negative values for A|| and A⊥ and solving the last equation to obtain α 2 and β 2, where the dipolar interaction constant "p" between magnetic moment of the electron and vanadium nucleus can be calculated from the following equation [62]: p=7/6[(A|| –A⊥)]

(9)

The spin-orbit coupling coefficient, λ, is assumed to be 170 cm-1for VO2+ ion and E is the electronic transition energy of 2B2 → 2E and k is the Fermi contact term which is directly related to the isotropic hyperfine coupling and represents the amount of unpaired electron density at the nucleus. The lower values of β 2 compared to α2 indicate that in-plane σ-bonding is less covalent. The values of α2 and β 2 or most of the oxovanadium complex indicates that the in-plane and π-bonding are appreciably ionic. These data are well consistent with other reported data [59].

3.6. Mass spectral studies The mass spectra of some complexes and the molecular ion peaks that confirms the proposed formulae are listed in Table 1. As a typical example, the mass spectrum of [Ni(H 2ATHC)(OAc)]2H 2O (Fig. 2) which showed peaks corresponding to the successive degradation of the molecule. The appearance of a molecular ion peak at m ⁄ e =400.80 is in accordance with the molecular mass of the present compound excluding two water molecules present herein, which are supposed to be lost before ionization [63]. The second peak at m /e = 326.45 is corresponding to the removal of H2O and CH 3COO after which multi peaks are observed. The peak at m⁄e =284 (Calcd. 283.4) represents the removal of C3H 5 fragment. The base peak at m ⁄ e =58.05 represents Ni isotope. 3.7. Thermogravimetric studies The stages of decomposition, temperature range, decomposition product as well as the weight loss percentages of complexes are given in Table 5. One of the features in TGA data concerning the associated water and/or ethanol molecules within the complexes supports the elemental analyses. Water of crystallization was lost within the temperature range 38-132 oC whereas the coordinated water molecules were lost in the range135-197 oC. Figure 3 shows the TGA curves of [Co(HATHC)(H2O)], [Ni(H 2ATHC)(OAc)]2H2O, [Cu(H 2ATHC)(OAc)(H2O)]H 2O, [Zn(H2ATHC)(OH)(H2O)(EtOH)]H 2O and [VO(H 2ATHC)(SO4)]2H 2O

complexes.

TG

curve

of

[Co(HATHC)(H2O)]2H2O as a representative example displays four degradation steps. The first step at 19-113 oC with weight loss of 10.10 (Calcd. 10.01 %) is attributed to the loss of the two lattice water molecules. The second step with weight loss of 26.80 (Calcd. 26.29 %) at 114-138 oC is corresponding to the removal of (CH3)3N+ + Cl. The third step at 139-293 o

C with weight loss of 23.00 (Calcd. 22.81 %) is referring to the removal of

CH 2CO + 2CN. The fourth step (294-750 oC) can be ascribed to elimination of C3H 6N fragment with weight loss of 15.50 (Calcd. 15.59 %). The residual part is CoS (Found 24.41, Calcd. 25.29 %).

3.8. Kinetic data The kinetic and thermodynamic parameters of thermal degradation process using Coats-Redfern and Horowitz-Metzger models [64, 65] have been evaluated (Tables 6& 7) and the data represented graphically in Figs 4 &5. A number of pyrolysis processes can be represented as a first order reaction. The enthalpy of activation, ∆H*, entropy of activation, ∆S* and free energy of activation, ∆G* (Tables 6&7) were calculated by Eyring equation [66]: ∆H*= Ea - RT

∆S = R ln

hA k BT

∆G* = ∆H* - T∆S*

(10)

(11) (12)

The high values of the energy of activation, Ea of the complexes reveal the high stability of such chelates due to their covalent bond character [67] and the positive sign of ∆G* for the investigated complexes indicates that the free energy of the final residue is higher than that of the initial compound, and all the decomposition steps are non-spontaneous processes. Also, the values of the activation, ∆G* increases significantly for the subsequent decomposition stages of a given complex. This is due to increasing the values of T∆S* significantly from one step to another which overrides the values of ∆H* [68]. The entropy of activation, ∆S* has negative values indicating more ordered activated complex than the reactants or the reaction is slow [69].

3.9.Biological studies 3.9.1.DPPH free radical scavenging activity.

In this study, The compounds, H3ATHC, Zn(II), Co(II) and Cu(II) complexes were found to be much better DPPH radical scavenger with IC50: 5.33, 5.35 and 6.46 mg/ml respectively. The Ni(II) complex showed moderate activity with IC50of 11.01 while U(VI)O2 complex showed very weak activity with IC50of 23.15 mg/ml. . The IC50 values were determined for all compounds and reported in Fig. 6a. The variation of %DPPH radical scavenging activity with concentration of test compounds was showed in Fig.6b. 3.9.2.Antioxidant activity using ABTS inhibition

The assay employs the radical cation derived from 2,2′-azino-bis (3ethyl benzthiazoline-6-sulfonic acid) (ABTS) as stable free radical that can accept an electron or hydrogen radical thus be converted into a stable diamagnetic molecule. ABTS+ has an odd electron and a strong absorption band at 734 nm. When the electron becomes paired off the absorption decreases stoichiometrically with respect to the number of electrons taken up. Such a change in the absorbance produced in this reaction has been widely applied to test the capacity of numerous molecules to act as free radical scavengers. Vitamin C was used as a reference compound. All tests were undertaken on three replicates and the results averaged. An insight on and Table 8 (Fig.7) reveals that Zn(II) complex , H3ATHC and Co(II) complex exhibited a potent radical scavenging activity (88.1, 87.0 and 86.1%) that is comparable to that of vitamin C (standard drug). On the other hand, Ni(II) and Cu(II) complexes showed moderate antioxidant activity while UO22+ complex had the lowest antioxidant activity.

3.9.3. Scavenging activity of superoxide radicals

Even under optimal circumstances, reactive oxygen species (ROS), including the superoxide radical (O.-2, the hydroxyl radical (.OH) and hydrogen peroxide (H2O2) produced as a byproduct of normal metabolism in different subcelluar compartments [70]. The ROS can damage DNA, proteins, memberane functions,generate lipid peroxidation and have been implicated in the pathology of a vast variety of human diseases like cancer diabetes, hypertension and aging [71]. To mitigate and repair damage of DNA initiated by ROS, cells have developed a complex antioxidant system. Superoxide dismutase (SOD) is the first line of defense against injury caused by ROS, catalyzing the dismulation of O.-2 to H2O2, and molecular oxygen [72]. Fe(II), Mn(II), Cu(II), Zn(II) and Ni(II) acted as metal co-SOD enzyme factors, which are located in different compartments of the cell [73].SOD or the metal complexes catalyze the dismulation of superoxide according to the following equations: Mn+ +O2. →M(n-1)+ +O2

(i)

M(n-1)+ +O2. +2H+ →Mn++H2O2 (ii) 2O2. + 2 H+→ H2O2+ O2

(iii)

H3ATHC and its metal complexes were screened for their superoxide – scavenging activity in the PMS/NADH-NBT system and the results are listed in Table 9.In this system, superoxide anion derived from dissolved oxygen by PMS/NADH coupling reaction reduces NBT. The decrease of absorbance at 560 nm with antioxidant activity of the complexes indicates the consumption of superoxide anion in the reaction mixture. A glance at Table 9 indicates the apparent variation in the overall scavenging ability among the ligand and its metal complexes. The ligand and U(VI)O2 complex displayed scavenging activity lower than 50% comparable to ascorbic acid but still higher than that of the other complexes.

3.9.4. Structuree activity relationship (SAR) studies In this study four parameters, namely the steric hinderence, the

extent of availability of NH groups as electron donner or hydrogen radical, the number of OH or acetate groups and LUMO (the energy of the lowest unoccupied molecular orbital of radical) were responsible for antioxidant activity. So, Zn 2+

exhibited the potent scavenging activity

as the steric effects of the three methyl groups N+(CH3)3), one NH and one OH, two C=N groups free contribute to increase the antioxidant activity. In case of the thiosemicarbazide derivative(H3ATHC), the high antioxidant activity is owing to the steric effect of the three methyl groups (N+(CH3)3), presence of two free NH ( N2H and N4H ) and C=S that can donate hydrogen atoms to ABTS+ radical or DPPH [74]. In Co2+ complex there are only two free NH groups (N2H and N4H). On the other hand, the moderate activity of Cu2+ and Ni2+ complexes is referred to the existence of only one free NH group (N4H) and C=S that can be available as electron donner or hydrogen radical. Finally, the lowest scavenging activity of UO22+ complex perhaps the compound has oriented itself in a manner that prevents the NH (N4H)group to be an electron donating group.

Conclusion H3ATHC forms mononuclear complexes with Co2+, Ni2+, Cu2+, Zn2+ and VO2+. All the measurements confirmed tetrahedral geometry for Co2+, square-planar for Cu2+, an octahedral for Zn2+ and a square-pyramidal for VO2+ complexes. Also, the ESR spectral data of Cu2+ and VO2+ complexes are in accordance with the proposed structures. The higher values of α2 and

β 2 in case of copper complex revealed appreciable covalency in the metalligand bonding, presumably arising out of Cu2+-thione/thiol coordination. On contrast the lower values of α2 and β 2 of the investigated vanadyl

complex revealed that the in-plane σ-bonding is less covalent and in plane πbonding are appreciably ionic. The TG analysis for the investigated complexes displayed high residual part indicating high stability of the formed chelates. Moreover, H3ATHC, Zn(II), Co(II) and Cu(II) complexes were found to be much better DPPH

and ABTS radical scavenger

comparable to that of vitamin C. On the other hand, H3ATHC and U(VI)O2 complex displayed higher SOD scavenging activity than the other metal complexes. References

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Figure 1. ESR spectra of [Cu(H2ATHC)(OAc)(H2O)].H2O

58

100

80

60 42

40

20 99 72

0 0

50

11 2

100

139

156

150

211 185

200

240

327

250

300

369

350

Figure 2. Mass spectra of [Ni(H2ATHC)(OAc)].2H2O

401

400

Figure3.TGA curves of (i) [[Co(HATHC)(H2O)], (ii) [Cu(H2ATHC)(OAc)(H2O)] H2O, (iii) [Ni(H2ATHC)(OAc)].2H2O, (iv) [VO(H2ATHC)(SO4)] and [Zn(H2ATHC)(EtOH)(OH)(H2O)].H2O

lnX n=1 lnX n=0.66 lnX n=0.33 lnX n=0 lnX n = 0.5

(a)

-10.6 -10.8 -11.0

(b) -10.8

lnX lnX lnX lnX lnX

n=1 n=0.66 n=0.33 n=0 n = 0.5

lnX lnX lnX lnX lnX

n=1 n=0.66 n=0.33 n=0 n = 0.5

-11.2 -11.4

lnX n=1

lnX n=1

-11.6 -11.8 -12.0

-11.4

-12.2 -12.4 -12.6

-12.0

-12.8 -13.0 0.0025

0.0026

0.0027

0.0028

0.0029

0.0030

0.0031

0.0024

1000/T

0.00 26

0 .0028

0.0030

1000/T

-10.5

(c)

-11.0

lnX lnX lnX lnX lnX

n=1 n=0.66 n=0.33 n=0 n = 0.5

-11.5

(d)

-12.0

-11.5

lnX n=1

-12.5 -13.0

-12.5

-13.0 -13.5 -14.0

-13.5 -14.5 0.002600.002650.002700.002750.002800.002850.002900.002950.003000.00305

0.00174

1000/T

0.00176

0.00178

0.00180

0.00182

0.00184

0.00186

1000/T

-11 .5

(e )

ln X ln X ln X ln X ln X

n= 1 n = 0 .6 6 n = 0 .3 3 n= 0 n = 0 .5

-12 .0

-12 .5

lnX n=1

lnX n=1

-12.0

-13 .0

-13 .5

-14 .0 0 .00 2 50 0 .0 02 55 0 .0 02 60 0 .0 0 26 5 0 .0 0 27 0 0 .0 0 27 5 0 .0 0 28 0 0 .00 28 5 0 .00 29 0

1 0 0 0 /T

Figure 4: Coats-Redfern plots [a, b, c, d and e] of the first peak for (i) [Co(HATCH) H2O].2H2O, (ii) [Cu(H2ATHC)(OAc)(H2O)].H2O, (iii) [Ni(H2ATHC)(OAc)].2H2O, (iv) [Zn(H2ATHC)(OH)(H2O)(EtOH)].H2O and (v)[VO((H3ATHC)(SO4)].2H2O

1.5

ln x n=1 ln x n=0.66 ln x n=0.33 ln x n=0 ln x n=0.5

(a)

1.0

1.2

ln x n=1 ln x n=0.66 ln x n=0.33 ln x n=0 ln x n=0.5

(b)

1.0 0.8 0.6

ln x n=1

ln x n=1

0.5

0.0

0.4 0.2 0.0

-0.5 -0.2 -0.4

-1.0

-0.6 -40

-30

-20

-10

0

-1.5

10

20

30

T-Ts -30

-20

-10

0

10

20

30

40

50

T-Ts

1.0

ln ln ln ln ln

(c)

x n=1 x n=0.66 x n=0.33 x n=0 x n=0.5

ln x n=1 ln x n=0.66 ln x n=0.33 ln x n=0 ln x n=0.5

(d)

1.0 0.8

0.5

0.6 0.4

0.0

ln x n=1

-1.0

0.0 -0.2 -0.4

-1.5

-0.6 -0.8

-2.0

-1.0

-2.5

-1.2 -20

-30

-20

-10

0

10

20

-15

-10

30

0

ln x n=1 ln x n=0.66 ln x n=0.33 ln x n=0 ln x n=0.5

(e)

0.5

-5

T-Ts

T-Ts

0.0

-0.5

ln x n=1

ln x n=1

0.2

-0.5

-1.0

-1.5

-2.0

-2.5 -30

-20

-10

0

T-Ts

10

20

30

5

10

15

20

40

Figure 5. Horowitz-Metzger plots [a, b, c, d and e ] of the first peak for (i) [Co(HATCH)H2O].2H2O, (ii) [Cu(H2ATHC)(OAc)(H2O)], (iii) [Ni(H2ATHC)(OAc)].H2O, (iv) [Zn(H2ATHC)(EtOH)(H2O)(OH)].H2O and (v)[VO(H3ATHC)(SO4)].2H2O

Fig. 6a. DPPH scavenging capacities (IC50) of H3ATHC and its metal complexes.

100 90 80 70 60

Ascorbic acid

50 40

Ligand

30

Co- complex

20

Zn- complex

10

Ni- complex

0

UO2- complex 0

100

200

500

1000

Concentration (μg/ml)

Fig.6b.DPPH scavenging activity spectrophotometric concentrations of H3ATHC and its complexes.

assay

of

various

Table 1 . Physical properties and elemental analyses of H3ATHC and its complexes. Compound, Formula

H3ATHC

F.Wt Found (Calcd.) (267.76)

[Ni(H2ATHC)(OAc)] 2H2O,

419.02

NiC11 H25N4O5SCl

(419.45)

[Co(HATHC) (OAc)(H2O)],

329.75

C13H16N4O4SClCo

(341.69)

[Cu(H2ATHC)(H2O)],

424.90

C11H25N4O5SClCu

(424.33)

[Zn(H2ATHC)(EtOH)(OH)(H2O)].H2O

429.00

C11H29N4O5SClZn

(430.23)

[UO2(H2ATHC)(OAc)].2H2O,

(647.87)

C11H25N4O7SClU [VO (H3ATHC)(SO4)(H2O)] C9H23N4O8S2ClV

Colour

White

Yield %

85

Dark violet

92

Dark green

90

olive Green

85

White

80

Yellowish

70

o

C

205-210

Yellowish green

85

C 40.52 (40.21)

H

7.00 (7.29)

N 20.99 (21.03)

---

5.76

(31.49)

(6.01)

31.49

4.50

(31.63)

(5.60)

31.08

3.69

(31.14)

(5.94)

Decompose at

30.46

6.23

280

(30.70)

(6.79)

>300

33.81

3.69

17.12

15.50

(34.21)

(4.10)

(17.43)

(16.20)

22.65

5.44

10.38

17.00

(22.90)

(4.70)

(9.70)

(17.66)

Char at 170

Char at 160

Char at 190

--------

M

32.20

Char at 165

brown (465.79)

Found (Calcd.) %

M.P.,

14.12 (13.99)

--------

--------------

16.94 (17.25) 15.00 (14.97) 14.88 (15.19)

Table 2. I.R. absorption spectral bands of H3ATHC and its metal complexes. Compound

ν(N4H)

ν(N1H)

Ν(N2H) ν C=O)

ν(C=S)

Ν(C-O)

ν(C-S)

ν(C=N*)

ν(M-O)

H3ATHC

3164s

3210m

3100 m

1222s,710 s

-------

------

--------

-------

[Co(HATHC) H2O]

3184m

--------

--------

-----------

1124m

664s

1571s

485s

[Ni(H2ATHC)OAc].2H2O

3150w

--------

3062 w

1220s,710 s

1123s

1575b

491s

[Cu((H2ATHC)OAc.H2O].H2O

3124w

3275s

3097 w

---------

1218s,715 b

1124s

------

1557s

500s

[Zn(H2ATHC)(OH)(EtOH)].H2O

3259w

--------

3086 m

---------

1207w,715w

1125s

------

1590b

544s

[UO2 (H2ATHC)OAc.H2O].H2O

3182m

--------

--------

---------

1228w,709w

1120m

------

1608s

549s

[(VO)2 (H2AHC)SO4(OH)EtOH]

--------

3215m

--------

1716w

-------------

-------

649s

1591m

506s

1706s -----------------

------

S=strong, m=medium ,b=broad and W=weak Table 3. Magnetic moments and electronic spectral data of metal complexes. Complex State

µ eff. (B.M.)

d-d transition Charge transfer bands (cm-1)

(cm-1) 32467,28089, 22624

[Co(HATHC)(H2O)]

Nujol

4.87

14705, 6556

[Ni(H2ATHC)OAc].2H2O

Nujol

4.08

18382,15625 32679,26455

[Cu((H2ATHC)(OAc)(H2O)].H2O

Nujol

1.79

14492

33112,27778

[UO2 (HATHC)(OAc)(H2O)].H2O

Nujol

------

21008

34246,29239,23696

[(VO)2(H2AHC)(SO4)].2H2O

Nujol

1.47

13151

36764,28653,26316

Table 4. ESR data of the some Cu II) and (VO)+2 complexes at room temperature. Complex

g//

A//× 10-4

g⊥

G

g/// A//

α2

β2

cm-1 [Cu((H2ATHC)OAc.H2O].H2O

2.20

2.06

140

3.3

157

0.74

0.66

[VO(H3ATHC)(SO4)].2H2O

1.92

1.96

200

60

2.0

----

0.97

Table 5.Decomposition steps with the temperature range and weight loss for H3ATHC complexes. Temperature range (oC)

Complex

[Co(HATHC)(H2O)]

[Ni(H2ATHC)(OAc].2H2O

[Cu(H 2ATHC)(OAc)(H 2O)].H2 O

[Zn(H2ATHC)(OH)(H2O)(EtOH)].H 2O

[VO(H3ATHC)(SO 4)].2H 2O

.

312-415

Species Removed

Found (calcd.) %

-2H2O

5.28(5.23) +

416-573

- (CH3)N +Cl

26.80(26.29)

574-801

- CH2CO+2CN

23.00(22.81)

801-1034

-

C 3H6N

5.00(15.59)

1034-1073

-

CoS

24.41(25.29)

58-138

- 2H2O

8.56(8.59)

172-317

- (CH3)N++Cl

22.93(22.82)

318-459

- C 3H6N+ C2H 3O

26.59(27.21)

460-550

-C3H 2N2

16.25(34.07)

551-800

-NiO+S

25.67(25.45)

39-139

-H2O

4.07(4.18)

140-180

- H2 O

4.29(4.00)

198-349

-(CH 3)N+ +CH3COO+ C2H3 N2

41.34(40.82)

350-500

-Cl+ C4H 6N

24.00(24.40)

505-800

-CuO+S

24.41(24.48)

37-139

- H2 O

4.02 (4.18) +

236-320

-H2O+C 2H5 OH+(CH3)N +OH

31.75(32.58)

431-521

-C2H 2

5.75(6.05)

596-784

-Cl+N2+C 3H6N

19.00(19.64)

784-900

ZnO+S

26.10(26.36) +

246-334

-(CH 3)N +C 2H5OH+H2O

21.00(21.36)

335-424

-OH + C 3H4N 3O

18.95(19.95)

499-658

-Cl+C 3H5

21.81(22.20)

686-730

-SO 4+S

23.15 (23.21)

731-800

2VO

13.69(13.26)

Table 6. Kinetic parameters evaluated by Coats-Redfern equation. Complex

[Cu(H2ATHC)(OAc)(H2O)].H2O

[Co(HATHC)(H2O)]

[Ni(H2ATHC)(OAc].2H2O [Zn(H2ATHC)(OH)(H2O)(EtOH)].H2O

[VO(H3ATHC)(SO4)].2H2O

Peaks

Mid Temp (K)

Ea KJ\mol

A (S-1)

∆H KJ\mol

∆S KJ\mol.K

∆G KJ\mol

1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st

356 439 540 871 362 493 711 933 359 516 662 526 550 748 970 1063

15.96 67.39 59.3 20.90 28.26 58.44 46.02 120.67 69.17 51.11 120.84 62.90 157.60 229.50 145.87 1862.33

13.00 63.73 54.83 13.65 25.25 54.33 40.10 112.91 66.18 46.82 115.33 58.53 153.02 223.28 137.80 1853.49

-0.1626

-0.1438 -0.1302 -0.1146

70.94 128.54 138.46 140.78 82.92 128.7692 145.14 240.13 120.66 124.93 211.29 131.61 225.76 331.00 264.24 1975.39

340 553 633 826

50.30 98.26 170.55 206.07

2.35x104 1.82 x10 5 9.45 x10 4 4.35 x10 5 3.63 x10 4 1.34 x10 5 2.87 x10 5 1.48 x10 6 9.32 x10 4 1.33 x10 5 3.76 x10 5 6.08 x10 5 1.44 x10 6 4.78 x10 5 3.18 x10 6 2.28 x10 7 1.37 x105 5.34 x105

-0.1476 -0.1404 -0.1360 -0.1386

97.74 171.36 251.51 313.82

2nd 3rd 4

th

1.0306x106 9.86 x105

47.46 93.65 165.29 199.20

-0.1474 -0.1546 -0.1458 -0.1592

-0.1508 -0.1476 -0.1362 -0.1513

-0.1513 -0.1448 -0.1389 -0.1320

Table 7. Kinetic parameters evaluated by Horowitz-Metzger equation.

Complex

[Cu(H2ATHC)(OAc)(H2O)].H2O

[Co(HATHC)(H2O)]

[Ni(H2ATHC)(OAc)].2H2O

[Zn(H2ATHC)(OH)(H2O)(EtOH)].H2O [VO(H3ATHC)(SO4)].2H2O

peaks

Mid Temp (K)

Ea KJ\mol

A (S-1)

∆H KJ\mol

∆S KJ\mol.K

∆G KJ\mol

1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th

356 439 540 871 362 493 711 933 359 516 662 526 550 748 970 1063 340 553 633 826

15.35 67.97 58.88 21.15 28.10 58.66 46.24 121.73 69.60 50.81 121.87 62.66 158.83 228.61 144.92 1862.55 51.36 98.98 170.58 204.58

2.23x104 9.79 x105 2.72 x103 5.43 x105 3.59 x104 1.44 x105 4.10 x105 1.83 x106 6.82 x104 1.59 x105 4.00 x105 4.75 x105 1.46 x106 5.79 x105 2.89 x106 2.28 x107 1.37 x105 6.44 x105 1.05x106 9.25x105

12.39 64.31 54.39 13.91 25.09 54.56 40.33 113.97 66.61 46.52 116.36 58.29 154.25 222.38 136.85 1853.70 48.53 94.38 165.31 197.70

-0.1631 -0.1334 -0.1557 -0.1440 -0.1593 -0.1503 -0.1446 -0.1345 -0.1539 -0.1498 -0.1442 -0.1409 -0.1319 -0.1422 -0.1310 -0.1139 -0.1476 -0.1388 -0.1359 -0.1391

70.49 122.97 138.65 139.45 82.79 128.72 143.27 239.55 122.02 123.85 211.99 132.45 226.93 328.92 264.06 1974.88 98.80 171.22 251.43 312.77

Table8. Antioxidant assay for the prepared ligand and its metal complexes. Compound

ABTS Inhibition (%)

Control of ABTS Ascorbic acid [Cu(H2ATHC)(OAc)(H2O)].H2O

0% 89.38% 63.32%

[UO2 (H2ATHC)(OAc)(H2O)].H2O

19.11%

[Zn(H2ATHC)(OH)(H2O)(EtOH)].H2O [Ni(H2ATHC)(OAc].2H2O H3ATHC

88.61% 44.01% 87.83%

Table 9. Effect of ligand and its metal complexes on superoxide radicals generated by PMS/NADH-NBT system. Compound

% inhibition

L-ascorbic acid

89.60

H3ATHC

28.40

[Co(HATHC) H2O]

1.70

[Zn(H2ATHC)(OH)(EtOH)].H2O 10.30 [Ni(H2ATHC)OAc].2H2O

12.10

[Cu((H2ATHC)OAc.H2O].H2O

2.60

[UO2 (H2ATHC)OAc.H2O].H2O

23.30

6

Table S1. Selected calculations Bond C(10)-H(22) C(10)-H(21) C(9)-C(10) C(9)-H(20) C(8)-H(18) C(8)-H(19) C(3)-O(2)

bond lengths (Å) of H3ATHC in gaseous state from PM3 Length (Ǻ) 1.0880 1.0870 1.3280 1.0978 1.1125 1.1147 1.2107

Bond C(8)- N(7) H(17)-N(7) N(7)- C(6) C(6)- S(5) N(1)- H(16) N(1)- N(4) C(3)-N(4)

Length (Ǻ) 1.4860 0.9977 1.3592 1.6970 0.9994 1.4398 1.4520

Table S2. Selected bond angles (°) of H3ATHC in gaseous state from PM3 calculations Angle ° Angle ° C(11)-C(3)-O(2) 122.5 N(1)-C(6)-N(7) 116.6 O (2)-C (3)- N(4) 121.3 C(6)- N(7)-C(8) 125.5 C(3)- N(4)- N(1) 121.0 C(11)-C(3)-C(8) 122.5 N(4)- N(1)- C(6) 119.4 C(11)-C(3)-O(2) 116.0 N(1)- N(6)- S(5) 117.0

Table S3. Selected bond lengths (Å) of [Cu(H2ATHC)(OAc)(H2O)].H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) Cu(1)-O(36) 1.8559 N(8)-C(9) 1.4814 O(3)-Cu(1) 1.8689 N(8)-C(7) 1.3752 Cu(1)-O(41) 1.9455 N(5)-N(2) 1.4523 Cu(1)-N(2) 1.9310 C(4)-N(5) 1.3210 O(41)-H(43) 0.9665 C(7)-N(2) 1.5301 O(41)-H(42) 0.9679 N(2)-H(35) 1.0025 C(9)- H(19) 1.1146 C(9)-H(18) 1.1146 C(4)- O(3) 1.3326 N(5)-N(2) 1.4523 Table S4. Selected bond angles (°) of [Cu(H2ATHC)(OAc)(H2O)].H2O in gaseous state from PM3 calculations Angle ° Angle ° O(3)-Cu(1)- N(2) 93.81 C(37)-O(36)-Cu(1) 106.07 N(2)-Cu(1)-O(36) 93.99 C(12)-C(4)-O(3) 117.83 O(36)-Cu(1)-O(41) 88.13 Cu(1)-N(2)-C(7) 126.62 O(36)-Cu(1)-O(3) 88.86 C(4)-N(2)-Cu(1) 98.47 C(37)-O(36)-Cu(1) 106.07 Cu(1)-O(41)-H(43) 99.47 N(5)-N(2)-Cu(1) 98.47 Cu(1)-O(41)-H(42) 101.59 O(3)-C(4)- N(5) 125.50 N(2)-C(7)-S(6) 118.96 C(4)-N(5)-N(2) 117.76 C(38)-C(37)-O(34) 123.52 C(12)-C(4)-O(3) 117.83 O(36)-C(37)-C(38) 120.34 C(12)-C(4)-N(5) 116.62 C(4)-O(3)-Cu(1) 101.41

O(3)-C(4)-N(5) 125.50 C(7)-N(2)-Cu(1) 126.62 N(2)-C(7)-N(5) 105.12 H(35)-N(2)-N(5) 105.12 Table S5. Selected bond lengths (Å) of [Co(HATHC)(H2O)].H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) C(8)-H(17) 0..9957 C(4)-C(12) 1.5042 C(8)-C(7) 1.3315 Co(1)-N(2) 1.8559 C(7)-S(6) 1.7843 Co(1)-S(6) 2.2277 C(7)-N(2) 1.4433 Co(1)-O(3) 1.8951 N(2)-N(5) 1.4246 Co(1)-O(34) 2.0035 N(5)-C(4) 1.3250 O(34)-H(35) 0.9641 C(4)-O(3) 1.3478 O(34)-H(36) 0.9632 Table S6. Selected bond angles (°) of [Co(HATHC)(H2O)].H2O in gaseous state from PM3 calculations Angle ° Angle ° O(3)-Co(1)- N(2) 89.29 Co(1)-O(3)-C(4) 100.54 N(2)-Co(1)-S(6) 77.36 Co(1)-S(6)-C(7) 74.89 O(34)-Co(1)-O(3) 87.80 S(6)-Co(1)-O(34) 102.57 O(36)-Co(1)-N(2) 93.000 C(4)-N(5)-N(2) 112.72 O(3)-Co(1)-O(41) 90.000 O(3)-C(4)-C(12) 116.00 C(9)-N(8)-C(7) 122.29 C(9)-N(8)-H(17) 117.20 C(7)-N(8)-H(17) 120.31 N(8)-C(7)-S(6) 131.41 N(8)-C(7)-N(2) 123.59 S(6)-C(7)-N(2) 104.99 C(7)-N(2)-Co(1) 95.86 O(3)-C(4)-N(5) 123.94 Table S7. Selected bond lengths (Å) of [Ni(H2ATHC)(OAc)(H2O)]H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) N(8)-H(17) 0.9961 C(4)-O(3) 1.3174 N(8)-C(7) 1.3911 C(4)-C(12) 1.5053 C(7)-S(6) 1.7573 N(13)-C(16) 1.5158 C(7)-N(2) 1.4747 N(13)-C(14) 1.5204 N(2)-H(35) 0.9925 Ni(1)-N(2) 1.8432 N(2)-N(5) 1.4564 Ni(1)-O(3) 1.8339 C(5)- C(4) 1.3253 Ni(1)-O(34) 1.8683 C(37)- O(34) 1.3101 Ni(1)-O(36) 1.8580 C(37)- C(38) 1.4757 C(38)-C(41) 1.0987 C(38)- H(40) 1.1008 C(38)-H(39) 1.0983 Table S8. Selected bond angles (°) of [Ni(H2ATHC)(OAc)(H2O)].H2O in gaseous state from PM3 calculations Angle ° Angle ° O(3)-Ni(1)- N(2) 91.86 O(34)-Ni(1)-O(3) 95.36 O(36)-Ni(1)-N(2) 102.37 O(34)-Ni(1)-O(36) 70.31 Ni(1)-N(2)-N(5) 102.85 Ni(1)-N(2)-C(7) 97.71 O(36)-Cu(1)-N(2) 93.000 H(35)-N(2)-C(7) 114.38 H(35)-N(2)-N(5) 106.93 O(3)-C(4)-C(12) 117.87 C(4)-O(3)-Ni(1) 104.67 C(4)-N(5)-N(2) 114.72 O(3)-C(4)- N(5) 122.08 N(5)-C(4)-C(12) 180.03 N(2)-C(7)-S(6) 110.29

Table S9. Selected bond lengths (Å) of [UO2(H2ATHC)(OAc)(H2O)].H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) C(4)-O(3) 1.2308 C(7)-N(8) 1.4689 C(4)-N(5) 1.4078 N(8)-H(18) 1.0108 N(5)-H(39) 1.0100 N(8)-C(9) 1.4756 N(5)-N(2) 1.3555 C(9)-H(20) 1.0906 N(2)-H(17) 1.0105 U(1)-O(3) 2.0482 N(2)-C(7) 1.4090 U(1)-O(37) 1.9798 C(7)- S(6) 1.6879 U(1)-H(36) 2.4939 U(1)- O(38) 1.9801 U(1)-O(35) 2.0493 U(1)-O(36) 2.0494 O(35)-C(40) 1.3350 O(36)- C(40) 1.3350 C(40)-C(41) 1.4997 Table S10. Selected bond angles (°) of [UO2(H2ATHC)(OAc)(H2O)].H2O in gaseous state from PM3 calculations Angle ° Angle ° O(3)-U(1)- O(37) 77.96 U(1)-S(6)-C(7) 64.23 N(2)-C(7)-N(8) 123.59 N(2)-C(7)-S(6) 108.41 C(39)-O(36)-U(1) 99.97 S(6)-U(1)-O(3) 136.76 N(8)-C(7)-S(6) 127.16 C(7)-N(2)-N(5) 129.81 O(3)-U(1)-O(36) 51.26 O(3)-U(1)-O(35) 105.77 O(35)-C(39)-O(36) 92.15 S(6)-U(1)-O(37) 130.28 S(6)-U(1)- O(38) 114.26 S(6)-U(1)-O(36) 95.42 S(6)-U(1)-O(35) 70.31 C(12)-C(4)-O(3) 121.55 C(12)-C(4)-N(5) 117.34 N(5)-C(4)-O(3) 121.08 C(4)-N(5)-N(2) 130.45 H(17)-N(2)-N(5) 114.09 H(17)-N(2)-C(7) 103.37 Table S11. Selected bond lengths (Å) of[Zn(H2ATHC)(EtOH)(H2O)(OH)].H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) Cu(1)-O(36) 1.8559 N(8)-C(9) 1.4814 O(3)-Cu(1) 1.8689 N(8)-C(7) 1.3752 Cu(1)-O(41) 1.9455 N(5)-N(2) 1.4523 Cu(1)-N(2) 1.9310 C(4)-N(5) 1.3210 O(41)-H(43) 0.9665 C(7)-N(2) 1.5301 O(41)-H(42) 0.9679 N(2)-H(35) 1.0025 C(9)- H(19) 1.1146 C(9)-H(18) 1.1146

Table S12. Selected bond angles (°) of [Zn(H2ATHC)(EtOH)(H2O)(OH)].H2O in gaseous state from PM3 calculations Angle ° Angle ° O(3)-Zn(1)-O(40) 84.36 N(2)-Zn(1)-O(5) 80.310 N(2)-Zn(1)-S(8) 64.78 S(8)-Zn(1)-O(3) 105.32 O(40)-Zn(1)-O(4) 83.26 O(40)-Zn(1)-O(5) 80.62 H(41)-O(40)-Zn(1) 103.77 C(42)-O(40)-Zn(1) 109.33 C(42)-O(40)-H(41) 107.05 H(22)-O(3)-Zn(1) 104.40 H(21)-O(4)-Zn(1) 103.77 H(20)-O(4)-Zn(1) 104.09 H(20)-O(4)-H(21) 103.36 C(6)-)O(5)-Zn(1) 114.59 C(6)-N(7)-N(2) 115.84 O(5)-C(6)-N(7) 115.24 C(14)-C(6)-N(7) 121.66 H(19)-N(2)-Zn(1) 108.07 H(19)-N(2)-C(9) 108.63 N(7)-N(2)-Zn(1) 108.56 N(7)-N(2)-C(9) 113.93 C(9)-S(8)-Zn(1) 86.20 N(2)-C(9)-S(8) 100.04 N(10)-C(9)-S(8) 130.93 N(10)-C(9)-N(2) 128.88 Table S13. Selected bond lengths (Å) of [VO(H3ATHC)(SO4)].2H2O in gaseous state from PM3 calculations Bond Length (Ǻ) Bond Length (Ǻ) V(35)-O(41) 1.7799 V(35)-N(1) 1.9302 V(35)-O(2) 1.8458 V(35)-O(37) 1.8915 V(35)-O(36) 1.8927 O(37)-S(38) 1.6657 O(36)-S(38) 1.66570 S(38)-O(39) 1.5798 S(38)-O(40) 1.6798 C(6)-N(1) 1.4434 N(4)-H(34) 1.0096 N(4)-C(3) 1.3929 C(3)- O(2) 1.2261 C(3)-C(11) 1.5060 Table S14. Selected bond angles (°) of [VO(H3ATHC)(SO4)].2H2O in gaseous state from PM3 calculations Angle ° Angle ° O(2)-V(35)- O(36) 62.73 O(36)-V(35)-C(37) 76.94 N(1)-V(35-O(41) 121.51 N(1)-V(35)-O(2) 83.17 O(37)-V(35)-O(41) 118.11 V(35)-O(2)-C(3) 117.44 O(36)-S(38)-O(37) 89.93 O(36)-S(38)-O(39) 111.12 O(39)-S(38)-O(40) 117.92 O(40)-S(38)-O(37) 111.62 V(35)-N(1)-H(16) 108.70 V(35)-N(1)-N(4) 108.11 O(3)-C(4)- N(5) 125.00 N(4)-N(1)-C(6) 113.14 H(16)-N(1)-C(6) 109.29 N(1)-N(4)-H(34) 121.02 N(1)-N(4)-C(3) 115.09 H(34)-N(4)-C(3) 121.55 S(38)-O(37)-V(35) 96.54 S(38)-O(36)-V(35) 96.49 O(2)-C(3)-C(11) 122.60 O(2)-C(3)-C(11) 122.18 O(2)-C(3)-N(4) 115.19 H(16)-N(1)-C(6) 109.29 C(5)-C(6)-N(1) 122.26

Table S15. Some energetic properties of ligand and its complexes calculated by PM3 method Compound H3ATHC [Cu(H2ATHC) (OAc)( H2O)].H2O [Co(HATHC) ( H2O)].H2O [Ni(H2ATHC) (OAc)].H2 O [UO2 (H2ATHC)(OAc)].2H2O [Zn(H2 ATHC)(H2O)(EtOH)(OH)].H2O

Total Energy (kcal/mol) -67728.51 -11758.96 -82216.15 -25508.08 -84625.54 -79308.96

Binding Energy (kcal/mol) -2786.15 -3941.56 -3355.67 -3890.51 -4405.95 -3836.05

Electronic Energy (kcal/mol) -29156.17 -14809.97 -12177.99 -79778.90 -65555.20 -89421.21

Heat of Formation (kcal/mol) -215.56 -26.09 -87.80 -116.70 -191.13 -126.64

Dipole moment (D) 8.48 17.26 4.60 10.90 3.91 14.98

HOMO (eV)

LUMO (eV)

-12.17 -8.61 -8.35 -10.57 -9.14 -9.42

-4.67 -0.93 -0.91 -4.03 -2.26 -3.65

• Preparation of VO2+, Co2+, Ni2+, Cu2+, Zn2+ and UO22+complexes of thiosemicarbazide. • Elemental analysis, spectral characterization of the ligands and their complexes. • Thermal behavior of the solid metal complexes was studied using TGA technique. • The compounds were screened for antioxidant activity and cytotoxicity.