Synthesis and Structural Studies of Antimicrobially Active
Cr(III) Macrocyclic Complexes
Anupa K. Dubey, V. K. Tiwari and S. N. Dikshit
Department of Chemistry,
S.M.S Govt. Model Science College, Gwalior, M.P., INDIA. email:[email protected].
(Received on: July 22, 2015)
ABSTRACT
A new series of two Cr(III) Macrocyclic complexes have been synthesized and formulated as: M(III)[DPTPH](BF4)2, M(III)[DCTPH](BF4)2 where, (DPTPH) = diacetyl pyridine-N, N’- thiodipropionoyl dihydrazone, (DCTPH) = 2,6-pyridine dicarbonyl dichloride-N,N’- thiodipropionoyl dihydrazone and (BF4)= Tetrafluoroborate The newly synthesized metal complexes were characterized with the help of various physico-chemical techniques like Infra-red, elemental analyses, electronic spectra, conductance. The results of analysis show the complexes to be of octahedral geometry and of electrolytic nature. The complexes were proved to be coordinated with donor atoms and show coordination with chromium metal. The Ligand and complexes were also screened for their in-vitro antimicrobial activities against gram negative bacterial strain [E. coli (ATCC 8739) and S. typhi (ATCC 9150)] and gram positive bacterial strain [S. aureus (ATCC 6538)]. The fungal activities screened by [A. brasiliensis (ATCC 6404) and C. albicans (ATCC 10231)]. The complexes have been found to be more active than ligand.
Keywords: Macrocyclic complexes, Elemental analysis, Infra-red, Electronic
spectra, Antimicrobial activity.
INTRODUCTION
its wider application in all the field, particularly antibiotic, transport of ion and unusual binding properties8. The aim of the present work is to report synthesis, characterization and antimicrobial studies of a TDPDH ligand and its transition metal macrocyclic complexes which show antifungal and antibacterial activities.
EXPERIMENTAL
Materials
All the chemicals and solvents used of A.R, grade purchased from Aldrich, Himedia, Merck and CDH and have been used as received.
Synthesis of Ligand
The ligand, thiodipropionic acid dihydrazide was formed by mixing 1:2 stoichiometric quantities of transparent thiodipropionic acid ester (2.06 gm, 0.01M) solution and hydrazine hydrate (0.83cm3, 0.02M) were mixed in 20ml ethyl alcohol with continuous stirring. The obtained solution was refluxed over a water bath at 40-50 °C for around 5-6 hours. The obtained off-white crystal in bottom round flask was concentrated and cooled overnight and were filtered, washed with alcohol and ether then dried in vacuum over anhydrous CaCl2 in a desicator.
Synthesis of Metal Complex I
1:1:1 stoichiometric quantities of ligand (2.04 gm, 0.01M), Chromium Acetate (2.42 gm., 0.01M) and 2,6-diacetyl pyridine (1.63gm., 0.01M) were mixed in 20 ml. ethanol with continuous stirring. The obtained solution was refluxed over a water-bath for around 6-7 hours and concentrated. Then a little of sodiumtetrafluoroborate was added and the solution was cooled overnight, crystals separated out. These dark-yellow crystals were filtered, washed with alcohol and then dried in vacuum over anhydrous CaCl2 in a desicator.
Synthesis of Metal Complex II
1:1:1 stoichiometric quantities of ligand (2.04gm, 0.01M), chromium acetate (2.42 gm, 0.01M) and 2, 6-pyridine dicarbonyldichloride (1.90 gm., 0.01M) were mixed in 20 ml. ethanol with continuous stirring. The obtained solution was refluxed over a water-bath for around 6-7 hours and concentrated. Then a little of sodiumtetrafluoroborate was added and the solution was cooled overnight, crystals separated out. These light-yellow crystals were filtered, washed with alcohol and then dried in vacuum over anhydrous CaCl2 in a desicator.
ANALYTICAL AND PHYSICAL MEASUREMENTS
by (Make-VEEGO, Model- VMP-PM). For metal estimation, using gravimetric method of analysis Vogel’s Quantitative Inorganic Analysis (seventh edition) revised by G.SVEHLA. Infra-red spectra of synthesized compounds were recorded on (Perkin-Elemer- Model No.-
C91158) in the range 4000-400 cm-1. The electronic spectra of complexes i n DM SO wer e
recorded on a UV-VIS-NIR (Cary5E) spectrophotometer at room temperature.
TABLE: 1 ELEMENTAL ANALYSIS AND MOLAR CONDUCTIVITY DATA OF THE LIGAND AND NEWLY SYNTHESIZED Cr(III) MACROCYCLIC COMPLEXES
COMPOUND M.P.
(0C)
COLOR YIELD
(%)
ELEMENTAL ANALYSIS (%) (F/c)
MOLAR CONDUCTIVITY
(ohm-1cm2mol-1)
C H N M
TDPDH 181 Off-white 2.29 gm. 33.99 (34.90) 6.38 (6.78) 31..32 (31.42) - -
Cr(III)[DPTPH](BF4)2 273 Dark -yellow 2.70 gm. 31.98 (32.08) 3..03 (3.78) 13.11 (13.13) 9.1 (9.2) 112.75
Cr(III)[DCTPH](BF4)2 283 Light -yellow 2.91 gm. 24.99 (25.91) 2.16 (2.49) 12.04 (12.19) 8.60 (8.63) 112.62 INFRA-RED DATA
The band due to the -NH2 group disappeared completely in the complexes. The band
due to the -NH group did not show any change in the spectra of complexes, confirming that the Nitrogen of -NH group did not take part in reaction whereas a sharp band was seen in the range of 1370cm-1 proving that -NH2 group is present in the ligand. Some entirely new
absorption band appeared in the spectra of complexes viz. band around 560-550cm-1 due to M-N group, a band around 460-450cm-1 due to M-O group and a band around 360-350cm-1 due to presence of M-S group. These new band confirmed the coordination of nitrogen, oxygen and sulphur with the metal atom in the complexes.
TABLE- 2 INFRA-RED SPECTRAL DATA OF LIGAND AND NEWLY SYNTHESIZED Cr(III) MACROCYCLIC COMPLEXES
S. NO. FUNCTIONAL GROUPS [TDPDH] Cr(III)[DPTPH](BF4)2 Cr(III)[DCTPH](BF4)2
1. -CH2 2900 2860 2850
2. -NH2 1370 - -
3. -NH 3330 3300 3300
4. N-N 950 940 930
5. C-H 780 740 730
6. >C=N - 1610 1600
7. >C=O 1680 1630 1640
8. M-N - 560 550
9. M-O - 450 460
ELECTRONIC DATA
The synthesized macrocyclic complexes are stable in air, completely insoluble in water and common organic solvents, but they are soluble in DMSO. The electronic spectra of the complexes recorded in DMSO (HPLC grade). All the absorption bands in electronic spectra were found for complexes in the range of 11,550-11,500 cm-1 attributed to 2Eg→2T2g
transition and in the range of 24,300-24,200cm-1 attributed to L→M charge transfer
transition. These transition confirmed the octahedral geometric of the complexes.
TABLE - 3 ABSORPTION BANDS (in cm-1) OF MACROCYCLIC COMPLEXES IN
ELECTRONIC SPECTRA
S. NO.
COMPLEXES
TRANSITION (cm-1)
2
Eg→ 2
T2g L→M
1. Cr(III)[DPTPH](BF4)2 11550 24200
2. Cr(III)[DCTPH](BF4)2 11500 24300
MINIMUM INHIBITORY CONCENTRATION (MIC)
The antibacterial activity of ligand and its newly synthesized complexes determined by following methods, successive ten sterilized tubes filled with 2 ml. nutrient broth (8 gm. in 1000 ml. distilled water) containing 500µg/ml., 250µg/ml., and 100µg/ml., 50µg/ml. and
25µg/ml. respective concentrations of test compounds were inoculated with 100 µl of the
bacterial suspension. The tubes were incubated at 370C in a BOD incubator and observed for change in turbidity after 24 hours. A tube containing nutrient broth without sample was taken as control. The least sample concentration which inhibited the growth of the test organisms was taken as MIC.
TABLE-4 MINIMUM INHIBITORY CONCENTRATION (MIC) VALUE IN MOLAR CONCn. [X10-4] OF LIGAND AND NEWLY SYNTHESIZED Cr(III) MACROCYCLIC COMPLEXES
Compounds Activity against bacterial strain
Activity against fungal strain E. coli
(Gram-Negative)
Salmonella (Gram-Negative)
S. aureus (Gram-Positive)
A. brasiliensis C. albicans
TDPDH 0.590 0.584 0.617 0.575 0.575
Cr(III)[DPTPH](BF4)2 0.245 0.211 0.251 0.210 0.230
Cr(III)[DCTPH](BF4)2 0.241 0.210 0.249 0.208 0.220
RESULTS AND DISCUSSION
The ligand and macrocyclic complexes are solid, coloured and stable at room temperature and formulated as Cr (III)[DPTPH](BF4)2, Cr(III)[DCTPH](BF4)2.Ligand and
spectral data Table-2 of nitrogen and sulphur are suitably placed for coordination toward the metal ion, has been proposed for both complexes, whereas absent in ligand confirm an octahedral geometry of complex I and complex II. Electronic spectral data of ligand and Cr(III) macrocyclic complexes shown in Table-3. The Minimum inhibitory concentration (MIC) value in molar concn shown in Table-4 of ligand and complexes compared, where complexes showed good antimicrobial activities than ligand.
ACKNOWLEDGEMENT
We are thankful to the Department of Chemistry, S.M.S Govt. Model Science College, Gwalior, for laboratory facilities. Our special thanks to the esteemed institutions IIT- Roorkee, [Department of Biotechnology and Nanotechnology] and IIT-Saharanpur-UP. [Department of Polymer Science and Technology] for technical data analysis through sophisticated instrumentation relevant with research paper.
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