Syntheses, Characterization, and Microbial Activity of Some Transition Metal Complexes Involving Potentially Active 0 and N Donor Heterocyclic Ligands Rajesh Nagar Department
of Chemistry,
Institute
of Basic Sciences,
Agra University,
Khandari,
India.
ABSTRACT The formation of binary as well as ternary metal complexes of type MLL’ (where M(II) = Cu(II), Ni(II), Co@), and Zn(II); L = 8-hydroxyquinoline, and L’ = 2-furoic acid) has been studied. The complexes were synthesized and characterized by elemental analyses, molecular weight determination, the IR and electronic spectra, conductivity, and magnetic measurements. The presence of coordinated water molecules was demonstrated by thermogravimetric analysis. The microbial activity of these ligands and their metal complexes was determined on gram positive (Stuphylococcus aureus) and gram negative (Escherichiu coli) bacteria, the antifungal activity on some common fungi, viz. Aspergillus niger , Aspergillus nidulense, and PeniciNium citrinum.
INTRODUCTION The metal complexes have been found to be more biologically active in comparison to either the free ligands or the involved metal ions [l-6] and attempts have been made to correlate the stability of the metal-ligand complexes with their microbial activity [7- 101. An interesting fact in the study of mixed complexes concerns the relationship between the properties of a ternary complex and those of the two ligands, and binary complexes from which it is derived. One approach to such information involves measurement and comparison of formation constants. These type of studies have been well summarized by Marcus and Eliezer [ 111. During this study the particular interest is the mixing constant, which reveals any “excess Address reprint requests and correspondence Agra-282 010, India.
to: Dr. Rajesh Nagar, 32 Keshav Kunj II, Pratap Nagar C,
Journal of Inorganic Biochemisfry, 40,349-356 (1990) 0 1990 Elsevier Science Publishing Co., Inc., 655 Avenue of the Americas,
349 NY, NY 10010
0162-0134/90/%3.50
350
R. Nagar
stability” or “instability” associated with the mixed complex in comparison with the binary species. In this paper, an attempt has been made to study the formation and characterization of the binary and ternary complexes of Cu(II), Ni(II), Co(II), and Zn(I1) with oxine (OX) and 2-furoic acid (FA). The formation constants thus obtained are critically compared with their antimicrobial activity.
MATERIALS
AND METHODS
All chemicals ity water.
used were of Analar grade. All solutions
Syntheses of Metal Complexes. method of Musumeci
All complexes
were prepared
in conductiv-
were prepared by the improved
[4]
et al. 1121.
Physical Measurements. A Toshinwal CL-46 digital pH meter (accuracy 10.01 pH unit) was used for all pH measurements. It was calibrated by buffers of pH 4.00 and 9.20 (at 25°C) before each titration. Due to the low solubility of the chelates in water, 75% ethanol was employed as a solvent. Because the reading given by pH meter is true hydrogen activity when the solvent is water, to get correct hydrogen ion concentration calibration of glass electrodes were done [ 131. Dissociation constants of used ligands have been calculated by the method of Chaberek and Martell [14]. The stability constants of binary and ternary complexes were computed by the reported method [IS] in the case of simultaneous addition of ligands to the metal ion and by the method of Thompson and Loraas [16] in the case of stepwise chelation of the ligands . All the synthesized metal complexes were analyzed for C, H, and N by microanalytical techniques; metal contents in the complexes were estimated by the standard methods [ 171. Molecular weight of the complexes was determined by a cryscopic method in DMSO. The molar conductance of the metal complexes was measured in DMSO on a Toshniwal conductivity bridge. IR spectra were recorded on a PerkinElmer spectrophotometer, model 521. in the range 4CKW,200 cm ’ The electronic spectral measurements were made on DMSO solution in a Carl-Zeiss DMR spectrophotometer. Magnetic measurements were carried out at room temperature by Gouy’s method using CuS0,.5H20 as calibrant. Simultaneous DTA and TG analysis of the complexes were carried out to confirm the presence of water molecules. To study the microbial properties of the potentially active substance in vitro, the serial broth dilution method [18] is employed and minimum inhibitory concentration (MIC) is reported. For the most satisfactory growth of microorganisms, the proper temperature, pH, necessary nutrients, and growth media free from other microorganisms have been provided for the preparation of the culture of pathogenic bacteria and fungi using aseptic techniques [19]. The culture media used for the slant and broth was sterilized by the moist heat sterilization method [20]. All utensils used were sterilized by a suitable method [20]. The incubating period for bacteria was kept 24 hr at 37°C and for fungi, 96 hr at 28°C. During the present studies the antimicrobial studies of some synthesized binary and ternary complexes involving ligands and metal ions have been tested on some pathogenic bacteria and fungi using propylene glycol as a solvent.
SYNTHESES, MICROBIAL ACTIVITY OF METAL
351
RESULTS AND DISCUSSION Elemental Analyses, Molecular Weight Determination, Electronic Spectra, and Magnetic Moment Data
Conductance
Measurement,
Elemental analyses data and molecular weight determination of metal complexes (Table 1) indicate 1: 1: 1 (MLL’) type stoichiometry. These data also show the presence of two water molecules which is also confirmed by thermal studies and IR spectra of the complexes. The low conductance values (0.5-2.0 ohm-’ cm2 mol-‘) indicate their nonelectrolytic nature due to charge neutralization of the metal ion with the ligands. The value of magnetic moment and electronic spectra (Table 1) show octahedral geometry for all the complexes. Thermal Analysis. On gradual heating from room temperature the hydrated metal complexes dehydrated completely within the temperature range 120”C- 190°C. The corresponding weight loss, resulted by the dehydration and decomposition process (Table 2), are well in agreement with the calculated values. The complexes were found thermally stable and undergo decomposition within the temperature range 33O”C-510°C. The final products were the metal oxides in all cases. IR Spectral Studies. A comparative study of the IR spectra of the complexes with those of involved ligands has been given in Table 3. The appearance of new bands at 3550-3480 cm- 1 and around 1570 cm- ’ indicates the antisymmetric and symmetric OH stretching and H-OH bending modes. The OH (phenolic) stretching frequency at 3270 cm-’ observed in free 8-hydroxyquinoline (oxine) is absent in the spectra of the complexes, indicating the involvement of the phenolic group in complex formation. A strong band at 1500 cm-’ in the free oxine may be assigned to C=N bond. In complexes, this band is shifted to a lower wave number, indicating the coordination through nitrogen of the ligand [22]. Further, the strong bands in the region 1170-l 120 cm-’ probably depict the presence of coordinated oxine 1231. The IR spectra of the free ligand (2-furoic acid) show a band at 1680 cm- ’ which is shifted to the lower frequency region in the metal complexes confirming the coordination of the ligand to the metal ion through the carboxylic ion moeity [24]. The medium to strong bands in the 1110-1040 cm-’ region are assigned to C-O-C (furan ring) vibrations [25]. These bands show a considerable negative shift with splitting on complex formation. This suggests the coordination through furan ring oxygen. Some new bands were also observed in the spectra of metal complexes in the region 500-480 cm-’ and 440-400 cm-’ which are probably due to the formation of M-O and M-N bond respectively [26,27]. Formation Constant. Formation of binary as well as ternary complexes have been studied potentiometrically . The values of formation constants are given in Table 4. The log K$$,,, ’ slightly ’ IS greater than log K&r*, but considerably greater than M(FA) .This suggests that the reaction of 2-furoic acid anion with 1: 1, M-FA log K,(,,,, . is less favorable than 8-hydroxyquinoline-metal cation. The very high value of log K ;(pox and log K s(Ox) (oxj(r,@omplexes may be best explained in terms of da --) p7r back donation between metal and oxine. Oxine is a much better ‘K accepter than 2-furoic acid due to differences in bonding properties of heterocyclic nitrogen and the carboxylic group. When oxine is coordinated with metal ion, electron transfer from the occupied metal “d” orbitals to unoccupied p7r orbitals of oxine occur reinforcing the u electron transfer from ligand to metal.
_
--- -...--
Co complexes
Cu complexes Ni complexes
.._x--.----
Ln(C)X)(FAj 2HZ0
Co(OX)(FA).2H>O
Ni(OX)(FA).2H,O
Cu(OX)(FA),2H20
%n(FA): .2H,O
CO(FA)~.~H,O
Ni(FA),.2H,O
Cu(FA), .2H,O
Zn(OX), .2HZ0
Co(OX), .2Hz0
._
h. zg m+‘T,,(P) 4T,g “T,,(F) ‘Tlg “AZ,(F) 4T,g +4T,,(P)
-
_ _ -.
~__._.__~__._
>Azp *‘T,,(F)
-- 16350
Assignmeru y------i----. E, ---T,, ‘.41E -“‘T,,(F)
-.. .~
-
- .-....
”
ohm
__._.._~-~___-.....-
0.89
i.31
1.92
1.47
0.78
1.09
1.52
I,87
0.56
0.92
1.19
1.90
‘cm2 mol-’
.- -
--
~._--.__.----.. ---...
16.49 (16,831 17.93 ! 18.33)
17.46 (17.91) 16.63 116.77)
18.55 (18.58) 20.22 (20.20)
18.49 (18.52)
19.79 (19.75)
16.81 ’ 16.77)
15.29 (15.37)
^.______ _.-._.
(4-W) 3.83 (3.99) 4.02 13 93)
4.01 (3.95) 4.05
16.31 (16.38)
7.19 (7.22) 7.28 (7.31) 1.32 (7.30) 7.20 17.19) _.
4.18 (4.16) 4.17 (4.21) 4.22 (4.20) 4.15 14.14) 3.10 13.13) 3.21 (3.18) 3.19 (3.17) 3.13 !3 11) 3.71 (3.69) 3.63 13.74) 3.66 13.74) 3.71 11.67) 15.35 (15.33)
M
N
H
-- 25000 - 7000 - 15350 -20000
.I 14000 ‘-’ 1OOOfl
Band Maxima (cm_ ‘)
_---
55.79 (55.74) 56.49 (56.44) 56.35 (56.40) 55.52 155.47) 37.38 (37.33) 37.95 (37.90) 37.83 r37.87) 37.09 (37.12) 47.20 (47.39) 48.21 148.05) 47.68 (48.02) 46.85 (47.15)
CU(OX)~.ZH,O
Ni(OX),.2H,O
C
Metal Complex
Molar Conductance
Molecular Weight, Electronic Spectra, and Magnetic Moment Data -^---
Analyses (Found/Calculated)
TABLE 1. Analytical, Molar Conductance. .__--
diam.
4 95
3.17
1.89
diam
5.02
3.22
2.01
diam.
5.05
3.20
1.92
303 K
peff. B.M. at
_.
._________..
(350) 343 (356)
(354) 334 (349) 336
(323) 340
(317) 313
(316) 311
(321) 309
(383) 381 (389) 318
(383) 373
(388) 375
371
Calculated)
Molecular weight (Found/
-
SYNTHESES,
TABLE
MICROBIAL
ACTIVITY
2. Thermal Studies for Dehydration and Decomposition
353
OF METAL
Process of
Metal Complexes % Weight Loss Found (Calculated)
Reaction CU(OX)~.~H,O
+ 2H,O -+CIlO + proclucts -+ Ni(OX), + 2H,O + NiO + products + Co(OX), + 2H,O -+ co,o, + products --t Zn(OX), + 2H,O + ZnO + products -+ Cu(FA), + 2H,O -+ cue + products -+ Ni(FA), + 2H,O * NiO + products + Co(FA), + 2H,O + co,o, + products * Zn(FA), + 2H,O + zno + products + Cu(OX)(FA) + 2H,O + cue + products -+ Ni(OX)(FA) + 2H,O + NiO + products -+ Co(OX)(FA) + 2H,O -+ Co,O, + products -+ Zn(OX)(FA) + 2H,O + ZnO + products
Cu(OX), Ni(OX), .2H,O Ni(OX), Co(OX), .2H 2O Co(OX), Zn(OX),.2H,O Zn(OX), Cu(FA),.2H,O Cu(FA), Ni(FA), .2H *O Ni(FA), Co(FA), .2H *O Co(FA), Zn(FA),.2H,O Zn(FA), Cu(OX)(FA).2H,O Cu(OX)(FA) Ni(OX)(FA).W,O Ni(OX)(FA) Co(OX)(FA).2H,O Co(OX)(FA) Zn(OX)(FA).2H20 Zn(OX)(FA)
-
9.32(9.28) 20.56(20.50) 9.35(9.44-t) 19.59(19.51) 9.45(9.40) 43.25(43.31) 9.21(9.25) 20.83(20.92) ll.ll(11.19) 24.72(24.78) 11.31(11.37) 23.70(23.64) 11.42(11.36) 52.38(52.33) 11.23(11.13) 25.26(25.19) 10.23(10.15) 22.51(22.42) 10.12(10.29) 21.28(21.35) 10.37(10.28) 47.44(47.36) 9.98(10.10) 22.%(22.81)
+ Cu(OX),
TABLE 3. Characterization and Assignments of the Infrared Spectral Bands of 8-Hydroxyquinoline, 2-furoic Acid and Their Binary and Ternary Complexes Frequency (cm- ‘) Compound ox
FA Cu(OX), .2H,O Ni(OX), .2H ,O Co(OX),.2H,O Zn(OX),.2H,O Cu(FA),.2H,O Ni(FA),.2H,O Co(FA),.2H,O Zn(FA),.2H,O Cu(OX)(FA).2H,O Ni(OX)(FA).ZH,O Co(OX)(FA).2H *O Zn(OX)(FA).2H,O
“OH
3270 3480 3520 3500 3495 3490 3492 3510 3550 3545 3530 3520 3515
“C=N
1500 1490 1485 1480 1490 1475 1470 1465 1463
&OH
1380 1565 1568 1570 1575 1560 1568 1575 1582 1580 1560 1573 1578
“C-N
1330 1325 1320 1320 1315 1310 1313 1320 1315
“c-o
1095 1120 1125 1135 1140 1125 1129 1135 1130
*ring
1110 1040 1042 1080 1070 1050 1090 1085 1075
“c=o
1680 1650 1655 1658 1660 1640 1635 1645 1638
“M-N
405 410 413 422 440 425 435 400
“M-O
480 485 488 495 486 490 500 495
354
R. Nagar
TABLE 4. Formation
Constants of Metal Complexes
at 25 “C i 0.5”C and Ionic
Strength 0.1 mol dm _ 3 (KNO,) Formation Constant
CuOI)
Ni(II)
Co(U)
ZnW)
1%K $ox>
11.86
il.67
II 52
II 34
log K$%i,
11.68
II.38
i I .30
11.10
@K:,,,;
4.35
4. lb
3.92
3.79
log K $$,
4.28
7.93
3.71
.%.57
hKk’%;,,,, iog 0
4.56
4.38
-t.lE
3.x9
16.42
16.05
15.66
15.23
From examination of Table 4, the mixed complex formation takes place even though log KM,;O,;&,) is lower than log KEig&. This may be explained on the basis of the disproportionation concept given by Sigel [ZS] Microbial Activity. A closed and comparative study of Table 5 reveals that the Iigands are active against the bacteria and fungi studied. In these investigations it is found that, in general, the antimicrobial activity of oxine is intensified when it is chelated with metal ion; L-furoic acid and even its metal chelates possess very little activity against the growth of bacteria and fungi which may be due to its lower lipid solubility. However, the ternary complexes are found to possess very effective toxic action against some organisms, whereas in some cases. they have comparable activity as that of bis-(X-hydroxyquinolinato) metal complexes even though the former are less lipid soluble than the latter. It has been reported 1291 that 112 chelate of M(II)-oxine penetrates the cell and dissociates into 111. half chelate and free oxine. It indicates that the antimicrobial activity of M(U)-oxine is not due to the release of oxine within the cell but due to the dissociated 1: 1 complex such as that reported, TABLE 5. Antimicrobial Activity of Ligands/Metal Ions/Metal of Minimum Inhibitory Concentration (&ml) ____l____l__ _.._ --. --_--. iVzq------Bacteria Ligand j Metal Complex ----.-
CWO,),
NKNOd2 Co(NQ,
_.__________S. aureus 6Q.i:! 58.27 61.23 .._.
Complexes
in Terms
_-----I_--Fungi --
__I----.-.
A
nrdulenw
E. co/i
A. niger
“_
_^
6634
I 70.15
68 67 _._
P. citrinum ---
_.
69.29 .-.
_-
67.76
60.69
62.53
ox
42.10
40.28
42.52
45.79
48.16
FA Cu(OX),.2H,O Ni(OX),.2H,O Co(OX),.2H,O
74.83 38.70 30.52 25.67
70.15 37.59 31.87 20.13
69.29 21.36 20.87 15.15
72.52 32.13 75.32 20.81
69.87 34.59 28.i? 22.21
Zn(OX),.2H,O Cu(FA),.2H,O Ni(FA)2.2H,0
39.96 60.12 55.29
40.12 57.83 52.51
35.56 53 53
3x.2.3 52 is
37 27 54.56
Co(FA),.2H,O Zn(FA),.2H,O Cu(OX)(FA).2H,O Ni(OX)(FA).2H,O
52.10 63.35 19.28 15 39 k2.20 22.03
48.21 61.73 18.27 14.13 11.09 24.03
51.02 45.39 56.87 20.15 15.44 IO..23 24.83
49.19 47.23 s’i.64 I’). ;9 15. Ih 1’.15 ‘SC 2 1 07
52 43 46.27 57 21 17.23 14.14 II 39
Zn(NO,h
Co(OX)(FA).2H *O Zn(OX)(FA).2H,O
_,_l______~_
-.-~-.-..-----._--..--~.~.-----.-.II---~-
22.51 I---___-
SYNTHESES,
MICROBIAL
ACTIVITY
OF METAL
355
The comparable activity of the mixed ligand complexes to that of bis-(&hydroxyquinolinato) metal complex, even though the former possess less lipophilic character may be due to the dissociation of the mixed complexes at the site of action as shown below: 2M(OX)(FA)+M(OX)++ where
M(FA)++
OX-+
FA-
M = Cu(II), Ni(II), Co(n) and Zn(I1); OX = oxine, and FA = 2-furoic acid
Both the 1: 1 cationic complexes thus formed may be acting as toxic moities at the site of action reinforcing the total activity. Thus, in the mixed complexes in addition to 1: 1 Metal-oxinate, 1: 1 Metal-furoate may also be acting as a toxic agent which increases the activity. The binary Metal-furoate complexes individually show low activity due to their low lipid solubility which will not permit a considerable amount of cationic complex to go to the site of action. Apart from this, a comparable faster diffusion of the complex as a whole through the cells of fungi may be one of the important factors. It is evident that these complexes are stable and chemically inert, having no specific active centers. Such compounds can exert a powerful inhibitory effect on an intracellular biological process by concentrating at the susceptible site from which it dissolutes slowly. If we examine log K$oXj, log K&+), and log K $&+,, values of these complexes and their corresponding antimicrobial activity, it appears that the activity is not dependent of either of these values. This further confirms the role of cationic complex in the mechanism of antimicrobial activity of the mixed complexes. These investigations further confirm that chelation alone is not sufficient for enhancing the activity of a compound; it must be accompanied by lipid solubility also. The growth inhibition capacity of the metal complexes follow the order Co(n) > Ni(II) > CL@) > Zn(II) and the metal complexes follow the stability order [30, 311 Cu(I1) > Ni@) > Co(II) > Zn(II). The author is thankful to Professor K. N. Mehrotra and Dr. R. C. Sharma of Agra University for their interest and valuable suggestions during the investigations. The author would like to acknowledge Dr. M. N. Jha, F. R. I., and Colleges, Dehradun, and Mr. S. D. Jha for useful discussions on the subject in the initial phase of this work. Financial assistance by Council of Scientific and Industrial Research, New Delhi, under “Scientist Pool Scheme” is acknowledged.
REFERENCES 1. 2. 3. 4. 5.
R. Nagar and R. C. Sharma, J. Indian Chem. Sot. 65, 240 (1988). R. Nagar, R. K. Parashar, R. S. Shamra, and R. C. Sharma, Curr. Sci. 56, 518 (1987). R. Nagar, R. B. Johari, and R. C. Sharma, Indian J. Chem. 26, 962 (1987). R. Nagar and R. C. Sharma, Croatica Chem. Acta 61, 849 (1988). A. Albert, S. D. Rubbo, R. J. Goldacre, and B. G. Balfour, Brit. J. Exptl. Pathol. 28, 69 (1947). 6. J. R. J. Sorenson, J. Med. Chem. 19 135 (1976). 7. D. P. Meller and L. Maley, Nature (London) 161, 436 (1948).
356
R. Nagar
8. G. Anderegg, Helv. Chim. Actu 57. 1340 (1965). 9. S. S. Block, J. Agric. Food Chem. 3, 229 (1955). 10. G. J. Horsfall, Principles of Fungicidul Action, Chronica Botanica Co.. Walthan, 1956. 11. Y. Marcus and 1. Eliezer, Coord. Chem. Rev. 4, 273 (1969). 12. S. Musumeci, S. Gurrierie, E. Rizzarille, and A. Seminara. .I. Inorg. NW!. Chem. 38. 12 (1976). 13. L. G. Van Uitert and W. C. Fernelius, J. Am. Chem. Sot. 75. 3577 (1963). 14. S. Chaberek and A. E. Mar-tell, J. Am. Chem. Sot. 74, 5052 (1952). 15. S. Ramamoorthy and M. Santappa, J. Inorg. Nucl. Chem. 33, 1775 (197 1). 16. L. C. Thompson and J. A. Loraas, Inorg. Chem. 2, 89 ( 1963). 17. A. I. Vogel, A Text Book of Quantitative Inorganic .4na/vsis, Longmans Green, London, 1971. 18. C. G. Donald and A. R. Williams, Assa_v Methods o-f Antibiotics. A Laboratory Manual, Medical Encyclopedia Inc.. 19S5. 19. E. R. Rawlins, Bentley’s Text Book of Pharmaceutics, 8th Ed., Bailliere. Tindall, London, 1977. 20. Robert Cruichank et al., Medical Microbiology, The Practice of Microbiology, 12th Ed., Churchill Livingstone, Edinburgh, 1975. 21. B. N. Figgis, Introduction to Ligand Fields, Interscience, New York, 1966. 22. A. K. Sharma, G. S. Sodhi, and N. K. Kaushik, Bull. Sot. Chim. Fr., 152 (l983) 23. A. R. Katritzky and A. J. Boulton, J. Chem. Sot., 3500 (1959). 24. L. J. Bellamy, The Infrared Spectra of Complex Molecules, Chapman and Hall, London, 1975, 25. K. V. Joseph and V. V. Somayajulu, J. Indian Chem. Sot. 56, 505 i 1979). 26. K. Zofia and L. Pajdowshi, Polish J. Chem. 52, 2053 (1978). 27. J. R. Ferraro, Low Frequency Vibrations of Inorganic and Coordination Compounds, John Wiley; New York, 1971. 28. H. Sigcl, Agnew. Chem., Int. Ed. Engl. 14, 394 (1975). 29. A. Albert, M. I. Gibson, and S. D. Rubbo, Brit. J. Exptl. Pathol. 34. 119 (1953). 30. D. P. Mellor and L. Maley, Nature flondonj 159. 370 (1947). 31. H. M. Irving and R. J. P. Williams. J. Chem. So
of Chemistry,
Institute
of Basic Sciences,
Agra University,
Khandari,
India.
ABSTRACT The formation of binary as well as ternary metal complexes of type MLL’ (where M(II) = Cu(II), Ni(II), Co@), and Zn(II); L = 8-hydroxyquinoline, and L’ = 2-furoic acid) has been studied. The complexes were synthesized and characterized by elemental analyses, molecular weight determination, the IR and electronic spectra, conductivity, and magnetic measurements. The presence of coordinated water molecules was demonstrated by thermogravimetric analysis. The microbial activity of these ligands and their metal complexes was determined on gram positive (Stuphylococcus aureus) and gram negative (Escherichiu coli) bacteria, the antifungal activity on some common fungi, viz. Aspergillus niger , Aspergillus nidulense, and PeniciNium citrinum.
INTRODUCTION The metal complexes have been found to be more biologically active in comparison to either the free ligands or the involved metal ions [l-6] and attempts have been made to correlate the stability of the metal-ligand complexes with their microbial activity [7- 101. An interesting fact in the study of mixed complexes concerns the relationship between the properties of a ternary complex and those of the two ligands, and binary complexes from which it is derived. One approach to such information involves measurement and comparison of formation constants. These type of studies have been well summarized by Marcus and Eliezer [ 111. During this study the particular interest is the mixing constant, which reveals any “excess Address reprint requests and correspondence Agra-282 010, India.
to: Dr. Rajesh Nagar, 32 Keshav Kunj II, Pratap Nagar C,
Journal of Inorganic Biochemisfry, 40,349-356 (1990) 0 1990 Elsevier Science Publishing Co., Inc., 655 Avenue of the Americas,
349 NY, NY 10010
0162-0134/90/%3.50
350
R. Nagar
stability” or “instability” associated with the mixed complex in comparison with the binary species. In this paper, an attempt has been made to study the formation and characterization of the binary and ternary complexes of Cu(II), Ni(II), Co(II), and Zn(I1) with oxine (OX) and 2-furoic acid (FA). The formation constants thus obtained are critically compared with their antimicrobial activity.
MATERIALS
AND METHODS
All chemicals ity water.
used were of Analar grade. All solutions
Syntheses of Metal Complexes. method of Musumeci
All complexes
were prepared
in conductiv-
were prepared by the improved
[4]
et al. 1121.
Physical Measurements. A Toshinwal CL-46 digital pH meter (accuracy 10.01 pH unit) was used for all pH measurements. It was calibrated by buffers of pH 4.00 and 9.20 (at 25°C) before each titration. Due to the low solubility of the chelates in water, 75% ethanol was employed as a solvent. Because the reading given by pH meter is true hydrogen activity when the solvent is water, to get correct hydrogen ion concentration calibration of glass electrodes were done [ 131. Dissociation constants of used ligands have been calculated by the method of Chaberek and Martell [14]. The stability constants of binary and ternary complexes were computed by the reported method [IS] in the case of simultaneous addition of ligands to the metal ion and by the method of Thompson and Loraas [16] in the case of stepwise chelation of the ligands . All the synthesized metal complexes were analyzed for C, H, and N by microanalytical techniques; metal contents in the complexes were estimated by the standard methods [ 171. Molecular weight of the complexes was determined by a cryscopic method in DMSO. The molar conductance of the metal complexes was measured in DMSO on a Toshniwal conductivity bridge. IR spectra were recorded on a PerkinElmer spectrophotometer, model 521. in the range 4CKW,200 cm ’ The electronic spectral measurements were made on DMSO solution in a Carl-Zeiss DMR spectrophotometer. Magnetic measurements were carried out at room temperature by Gouy’s method using CuS0,.5H20 as calibrant. Simultaneous DTA and TG analysis of the complexes were carried out to confirm the presence of water molecules. To study the microbial properties of the potentially active substance in vitro, the serial broth dilution method [18] is employed and minimum inhibitory concentration (MIC) is reported. For the most satisfactory growth of microorganisms, the proper temperature, pH, necessary nutrients, and growth media free from other microorganisms have been provided for the preparation of the culture of pathogenic bacteria and fungi using aseptic techniques [19]. The culture media used for the slant and broth was sterilized by the moist heat sterilization method [20]. All utensils used were sterilized by a suitable method [20]. The incubating period for bacteria was kept 24 hr at 37°C and for fungi, 96 hr at 28°C. During the present studies the antimicrobial studies of some synthesized binary and ternary complexes involving ligands and metal ions have been tested on some pathogenic bacteria and fungi using propylene glycol as a solvent.
SYNTHESES, MICROBIAL ACTIVITY OF METAL
351
RESULTS AND DISCUSSION Elemental Analyses, Molecular Weight Determination, Electronic Spectra, and Magnetic Moment Data
Conductance
Measurement,
Elemental analyses data and molecular weight determination of metal complexes (Table 1) indicate 1: 1: 1 (MLL’) type stoichiometry. These data also show the presence of two water molecules which is also confirmed by thermal studies and IR spectra of the complexes. The low conductance values (0.5-2.0 ohm-’ cm2 mol-‘) indicate their nonelectrolytic nature due to charge neutralization of the metal ion with the ligands. The value of magnetic moment and electronic spectra (Table 1) show octahedral geometry for all the complexes. Thermal Analysis. On gradual heating from room temperature the hydrated metal complexes dehydrated completely within the temperature range 120”C- 190°C. The corresponding weight loss, resulted by the dehydration and decomposition process (Table 2), are well in agreement with the calculated values. The complexes were found thermally stable and undergo decomposition within the temperature range 33O”C-510°C. The final products were the metal oxides in all cases. IR Spectral Studies. A comparative study of the IR spectra of the complexes with those of involved ligands has been given in Table 3. The appearance of new bands at 3550-3480 cm- 1 and around 1570 cm- ’ indicates the antisymmetric and symmetric OH stretching and H-OH bending modes. The OH (phenolic) stretching frequency at 3270 cm-’ observed in free 8-hydroxyquinoline (oxine) is absent in the spectra of the complexes, indicating the involvement of the phenolic group in complex formation. A strong band at 1500 cm-’ in the free oxine may be assigned to C=N bond. In complexes, this band is shifted to a lower wave number, indicating the coordination through nitrogen of the ligand [22]. Further, the strong bands in the region 1170-l 120 cm-’ probably depict the presence of coordinated oxine 1231. The IR spectra of the free ligand (2-furoic acid) show a band at 1680 cm- ’ which is shifted to the lower frequency region in the metal complexes confirming the coordination of the ligand to the metal ion through the carboxylic ion moeity [24]. The medium to strong bands in the 1110-1040 cm-’ region are assigned to C-O-C (furan ring) vibrations [25]. These bands show a considerable negative shift with splitting on complex formation. This suggests the coordination through furan ring oxygen. Some new bands were also observed in the spectra of metal complexes in the region 500-480 cm-’ and 440-400 cm-’ which are probably due to the formation of M-O and M-N bond respectively [26,27]. Formation Constant. Formation of binary as well as ternary complexes have been studied potentiometrically . The values of formation constants are given in Table 4. The log K$$,,, ’ slightly ’ IS greater than log K&r*, but considerably greater than M(FA) .This suggests that the reaction of 2-furoic acid anion with 1: 1, M-FA log K,(,,,, . is less favorable than 8-hydroxyquinoline-metal cation. The very high value of log K ;(pox and log K s(Ox) (oxj(r,@omplexes may be best explained in terms of da --) p7r back donation between metal and oxine. Oxine is a much better ‘K accepter than 2-furoic acid due to differences in bonding properties of heterocyclic nitrogen and the carboxylic group. When oxine is coordinated with metal ion, electron transfer from the occupied metal “d” orbitals to unoccupied p7r orbitals of oxine occur reinforcing the u electron transfer from ligand to metal.
_
--- -...--
Co complexes
Cu complexes Ni complexes
.._x--.----
Ln(C)X)(FAj 2HZ0
Co(OX)(FA).2H>O
Ni(OX)(FA).2H,O
Cu(OX)(FA),2H20
%n(FA): .2H,O
CO(FA)~.~H,O
Ni(FA),.2H,O
Cu(FA), .2H,O
Zn(OX), .2HZ0
Co(OX), .2Hz0
._
h. zg m+‘T,,(P) 4T,g “T,,(F) ‘Tlg “AZ,(F) 4T,g +4T,,(P)
-
_ _ -.
~__._.__~__._
>Azp *‘T,,(F)
-- 16350
Assignmeru y------i----. E, ---T,, ‘.41E -“‘T,,(F)
-.. .~
-
- .-....
”
ohm
__._.._~-~___-.....-
0.89
i.31
1.92
1.47
0.78
1.09
1.52
I,87
0.56
0.92
1.19
1.90
‘cm2 mol-’
.- -
--
~._--.__.----.. ---...
16.49 (16,831 17.93 ! 18.33)
17.46 (17.91) 16.63 116.77)
18.55 (18.58) 20.22 (20.20)
18.49 (18.52)
19.79 (19.75)
16.81 ’ 16.77)
15.29 (15.37)
^.______ _.-._.
(4-W) 3.83 (3.99) 4.02 13 93)
4.01 (3.95) 4.05
16.31 (16.38)
7.19 (7.22) 7.28 (7.31) 1.32 (7.30) 7.20 17.19) _.
4.18 (4.16) 4.17 (4.21) 4.22 (4.20) 4.15 14.14) 3.10 13.13) 3.21 (3.18) 3.19 (3.17) 3.13 !3 11) 3.71 (3.69) 3.63 13.74) 3.66 13.74) 3.71 11.67) 15.35 (15.33)
M
N
H
-- 25000 - 7000 - 15350 -20000
.I 14000 ‘-’ 1OOOfl
Band Maxima (cm_ ‘)
_---
55.79 (55.74) 56.49 (56.44) 56.35 (56.40) 55.52 155.47) 37.38 (37.33) 37.95 (37.90) 37.83 r37.87) 37.09 (37.12) 47.20 (47.39) 48.21 148.05) 47.68 (48.02) 46.85 (47.15)
CU(OX)~.ZH,O
Ni(OX),.2H,O
C
Metal Complex
Molar Conductance
Molecular Weight, Electronic Spectra, and Magnetic Moment Data -^---
Analyses (Found/Calculated)
TABLE 1. Analytical, Molar Conductance. .__--
diam.
4 95
3.17
1.89
diam
5.02
3.22
2.01
diam.
5.05
3.20
1.92
303 K
peff. B.M. at
_.
._________..
(350) 343 (356)
(354) 334 (349) 336
(323) 340
(317) 313
(316) 311
(321) 309
(383) 381 (389) 318
(383) 373
(388) 375
371
Calculated)
Molecular weight (Found/
-
SYNTHESES,
TABLE
MICROBIAL
ACTIVITY
2. Thermal Studies for Dehydration and Decomposition
353
OF METAL
Process of
Metal Complexes % Weight Loss Found (Calculated)
Reaction CU(OX)~.~H,O
+ 2H,O -+CIlO + proclucts -+ Ni(OX), + 2H,O + NiO + products + Co(OX), + 2H,O -+ co,o, + products --t Zn(OX), + 2H,O + ZnO + products -+ Cu(FA), + 2H,O -+ cue + products -+ Ni(FA), + 2H,O * NiO + products + Co(FA), + 2H,O + co,o, + products * Zn(FA), + 2H,O + zno + products + Cu(OX)(FA) + 2H,O + cue + products -+ Ni(OX)(FA) + 2H,O + NiO + products -+ Co(OX)(FA) + 2H,O -+ Co,O, + products -+ Zn(OX)(FA) + 2H,O + ZnO + products
Cu(OX), Ni(OX), .2H,O Ni(OX), Co(OX), .2H 2O Co(OX), Zn(OX),.2H,O Zn(OX), Cu(FA),.2H,O Cu(FA), Ni(FA), .2H *O Ni(FA), Co(FA), .2H *O Co(FA), Zn(FA),.2H,O Zn(FA), Cu(OX)(FA).2H,O Cu(OX)(FA) Ni(OX)(FA).W,O Ni(OX)(FA) Co(OX)(FA).2H,O Co(OX)(FA) Zn(OX)(FA).2H20 Zn(OX)(FA)
-
9.32(9.28) 20.56(20.50) 9.35(9.44-t) 19.59(19.51) 9.45(9.40) 43.25(43.31) 9.21(9.25) 20.83(20.92) ll.ll(11.19) 24.72(24.78) 11.31(11.37) 23.70(23.64) 11.42(11.36) 52.38(52.33) 11.23(11.13) 25.26(25.19) 10.23(10.15) 22.51(22.42) 10.12(10.29) 21.28(21.35) 10.37(10.28) 47.44(47.36) 9.98(10.10) 22.%(22.81)
+ Cu(OX),
TABLE 3. Characterization and Assignments of the Infrared Spectral Bands of 8-Hydroxyquinoline, 2-furoic Acid and Their Binary and Ternary Complexes Frequency (cm- ‘) Compound ox
FA Cu(OX), .2H,O Ni(OX), .2H ,O Co(OX),.2H,O Zn(OX),.2H,O Cu(FA),.2H,O Ni(FA),.2H,O Co(FA),.2H,O Zn(FA),.2H,O Cu(OX)(FA).2H,O Ni(OX)(FA).ZH,O Co(OX)(FA).2H *O Zn(OX)(FA).2H,O
“OH
3270 3480 3520 3500 3495 3490 3492 3510 3550 3545 3530 3520 3515
“C=N
1500 1490 1485 1480 1490 1475 1470 1465 1463
&OH
1380 1565 1568 1570 1575 1560 1568 1575 1582 1580 1560 1573 1578
“C-N
1330 1325 1320 1320 1315 1310 1313 1320 1315
“c-o
1095 1120 1125 1135 1140 1125 1129 1135 1130
*ring
1110 1040 1042 1080 1070 1050 1090 1085 1075
“c=o
1680 1650 1655 1658 1660 1640 1635 1645 1638
“M-N
405 410 413 422 440 425 435 400
“M-O
480 485 488 495 486 490 500 495
354
R. Nagar
TABLE 4. Formation
Constants of Metal Complexes
at 25 “C i 0.5”C and Ionic
Strength 0.1 mol dm _ 3 (KNO,) Formation Constant
CuOI)
Ni(II)
Co(U)
ZnW)
1%K $ox>
11.86
il.67
II 52
II 34
log K$%i,
11.68
II.38
i I .30
11.10
@K:,,,;
4.35
4. lb
3.92
3.79
log K $$,
4.28
7.93
3.71
.%.57
hKk’%;,,,, iog 0
4.56
4.38
-t.lE
3.x9
16.42
16.05
15.66
15.23
From examination of Table 4, the mixed complex formation takes place even though log KM,;O,;&,) is lower than log KEig&. This may be explained on the basis of the disproportionation concept given by Sigel [ZS] Microbial Activity. A closed and comparative study of Table 5 reveals that the Iigands are active against the bacteria and fungi studied. In these investigations it is found that, in general, the antimicrobial activity of oxine is intensified when it is chelated with metal ion; L-furoic acid and even its metal chelates possess very little activity against the growth of bacteria and fungi which may be due to its lower lipid solubility. However, the ternary complexes are found to possess very effective toxic action against some organisms, whereas in some cases. they have comparable activity as that of bis-(X-hydroxyquinolinato) metal complexes even though the former are less lipid soluble than the latter. It has been reported 1291 that 112 chelate of M(II)-oxine penetrates the cell and dissociates into 111. half chelate and free oxine. It indicates that the antimicrobial activity of M(U)-oxine is not due to the release of oxine within the cell but due to the dissociated 1: 1 complex such as that reported, TABLE 5. Antimicrobial Activity of Ligands/Metal Ions/Metal of Minimum Inhibitory Concentration (&ml) ____l____l__ _.._ --. --_--. iVzq------Bacteria Ligand j Metal Complex ----.-
CWO,),
NKNOd2 Co(NQ,
_.__________S. aureus 6Q.i:! 58.27 61.23 .._.
Complexes
in Terms
_-----I_--Fungi --
__I----.-.
A
nrdulenw
E. co/i
A. niger
“_
_^
6634
I 70.15
68 67 _._
P. citrinum ---
_.
69.29 .-.
_-
67.76
60.69
62.53
ox
42.10
40.28
42.52
45.79
48.16
FA Cu(OX),.2H,O Ni(OX),.2H,O Co(OX),.2H,O
74.83 38.70 30.52 25.67
70.15 37.59 31.87 20.13
69.29 21.36 20.87 15.15
72.52 32.13 75.32 20.81
69.87 34.59 28.i? 22.21
Zn(OX),.2H,O Cu(FA),.2H,O Ni(FA)2.2H,0
39.96 60.12 55.29
40.12 57.83 52.51
35.56 53 53
3x.2.3 52 is
37 27 54.56
Co(FA),.2H,O Zn(FA),.2H,O Cu(OX)(FA).2H,O Ni(OX)(FA).2H,O
52.10 63.35 19.28 15 39 k2.20 22.03
48.21 61.73 18.27 14.13 11.09 24.03
51.02 45.39 56.87 20.15 15.44 IO..23 24.83
49.19 47.23 s’i.64 I’). ;9 15. Ih 1’.15 ‘SC 2 1 07
52 43 46.27 57 21 17.23 14.14 II 39
Zn(NO,h
Co(OX)(FA).2H *O Zn(OX)(FA).2H,O
_,_l______~_
-.-~-.-..-----._--..--~.~.-----.-.II---~-
22.51 I---___-
SYNTHESES,
MICROBIAL
ACTIVITY
OF METAL
355
The comparable activity of the mixed ligand complexes to that of bis-(&hydroxyquinolinato) metal complex, even though the former possess less lipophilic character may be due to the dissociation of the mixed complexes at the site of action as shown below: 2M(OX)(FA)+M(OX)++ where
M(FA)++
OX-+
FA-
M = Cu(II), Ni(II), Co(n) and Zn(I1); OX = oxine, and FA = 2-furoic acid
Both the 1: 1 cationic complexes thus formed may be acting as toxic moities at the site of action reinforcing the total activity. Thus, in the mixed complexes in addition to 1: 1 Metal-oxinate, 1: 1 Metal-furoate may also be acting as a toxic agent which increases the activity. The binary Metal-furoate complexes individually show low activity due to their low lipid solubility which will not permit a considerable amount of cationic complex to go to the site of action. Apart from this, a comparable faster diffusion of the complex as a whole through the cells of fungi may be one of the important factors. It is evident that these complexes are stable and chemically inert, having no specific active centers. Such compounds can exert a powerful inhibitory effect on an intracellular biological process by concentrating at the susceptible site from which it dissolutes slowly. If we examine log K$oXj, log K&+), and log K $&+,, values of these complexes and their corresponding antimicrobial activity, it appears that the activity is not dependent of either of these values. This further confirms the role of cationic complex in the mechanism of antimicrobial activity of the mixed complexes. These investigations further confirm that chelation alone is not sufficient for enhancing the activity of a compound; it must be accompanied by lipid solubility also. The growth inhibition capacity of the metal complexes follow the order Co(n) > Ni(II) > CL@) > Zn(II) and the metal complexes follow the stability order [30, 311 Cu(I1) > Ni@) > Co(II) > Zn(II). The author is thankful to Professor K. N. Mehrotra and Dr. R. C. Sharma of Agra University for their interest and valuable suggestions during the investigations. The author would like to acknowledge Dr. M. N. Jha, F. R. I., and Colleges, Dehradun, and Mr. S. D. Jha for useful discussions on the subject in the initial phase of this work. Financial assistance by Council of Scientific and Industrial Research, New Delhi, under “Scientist Pool Scheme” is acknowledged.
REFERENCES 1. 2. 3. 4. 5.
R. Nagar and R. C. Sharma, J. Indian Chem. Sot. 65, 240 (1988). R. Nagar, R. K. Parashar, R. S. Shamra, and R. C. Sharma, Curr. Sci. 56, 518 (1987). R. Nagar, R. B. Johari, and R. C. Sharma, Indian J. Chem. 26, 962 (1987). R. Nagar and R. C. Sharma, Croatica Chem. Acta 61, 849 (1988). A. Albert, S. D. Rubbo, R. J. Goldacre, and B. G. Balfour, Brit. J. Exptl. Pathol. 28, 69 (1947). 6. J. R. J. Sorenson, J. Med. Chem. 19 135 (1976). 7. D. P. Meller and L. Maley, Nature (London) 161, 436 (1948).
356
R. Nagar
8. G. Anderegg, Helv. Chim. Actu 57. 1340 (1965). 9. S. S. Block, J. Agric. Food Chem. 3, 229 (1955). 10. G. J. Horsfall, Principles of Fungicidul Action, Chronica Botanica Co.. Walthan, 1956. 11. Y. Marcus and 1. Eliezer, Coord. Chem. Rev. 4, 273 (1969). 12. S. Musumeci, S. Gurrierie, E. Rizzarille, and A. Seminara. .I. Inorg. NW!. Chem. 38. 12 (1976). 13. L. G. Van Uitert and W. C. Fernelius, J. Am. Chem. Sot. 75. 3577 (1963). 14. S. Chaberek and A. E. Mar-tell, J. Am. Chem. Sot. 74, 5052 (1952). 15. S. Ramamoorthy and M. Santappa, J. Inorg. Nucl. Chem. 33, 1775 (197 1). 16. L. C. Thompson and J. A. Loraas, Inorg. Chem. 2, 89 ( 1963). 17. A. I. Vogel, A Text Book of Quantitative Inorganic .4na/vsis, Longmans Green, London, 1971. 18. C. G. Donald and A. R. Williams, Assa_v Methods o-f Antibiotics. A Laboratory Manual, Medical Encyclopedia Inc.. 19S5. 19. E. R. Rawlins, Bentley’s Text Book of Pharmaceutics, 8th Ed., Bailliere. Tindall, London, 1977. 20. Robert Cruichank et al., Medical Microbiology, The Practice of Microbiology, 12th Ed., Churchill Livingstone, Edinburgh, 1975. 21. B. N. Figgis, Introduction to Ligand Fields, Interscience, New York, 1966. 22. A. K. Sharma, G. S. Sodhi, and N. K. Kaushik, Bull. Sot. Chim. Fr., 152 (l983) 23. A. R. Katritzky and A. J. Boulton, J. Chem. Sot., 3500 (1959). 24. L. J. Bellamy, The Infrared Spectra of Complex Molecules, Chapman and Hall, London, 1975, 25. K. V. Joseph and V. V. Somayajulu, J. Indian Chem. Sot. 56, 505 i 1979). 26. K. Zofia and L. Pajdowshi, Polish J. Chem. 52, 2053 (1978). 27. J. R. Ferraro, Low Frequency Vibrations of Inorganic and Coordination Compounds, John Wiley; New York, 1971. 28. H. Sigcl, Agnew. Chem., Int. Ed. Engl. 14, 394 (1975). 29. A. Albert, M. I. Gibson, and S. D. Rubbo, Brit. J. Exptl. Pathol. 34. 119 (1953). 30. D. P. Mellor and L. Maley, Nature flondonj 159. 370 (1947). 31. H. M. Irving and R. J. P. Williams. J. Chem. So
