SYNTHESIS, SPECTRAL AND ANTIMICROBIAL PROPERTIES OF BINUCLEAR COMPLEXES OF COPPER SCHIFF BASE WITH ALKALI METALS
Creators: name: Kumar, Chandan
name: Deo, Rabindra Kumar
Publisher: name: Zenodo
Year: 2020

description: <strong>SYNTHESIS, SPECTRAL AND ANTIMICROBIAL PROPERTIES OF BINUCLEAR COMPLEXES OF COPPER SCHIFF BASE WITH ALKALI METALS</strong> <strong><em>Chandan Kumar, Rabindra Kumar Deo</em></strong> Department of Chemistry, S.P. College, S.K.M. University, Dumka-814101, Jharkhand, India <strong>Introduction </strong> Schiff base posses strong ability to form metal complexes and they deserve a proper attention because of their biological properties. Binucleating Schiff bases have been extensively used for the preparation of homo and heterobinuclear complexes [1,2]. Schiff base complexes show biological activities and they have been found antibacterial [3] and antifungal [4] activities. Schiff base and the relevant transition metal complexes are still found to be of great interest in the inorganic chemistry. Binuclear complexes, in which ligand structures capable to holding two metal centers in close proximity, one of the metal is transition metal and other one is alkali metal. In the continuation of earlier work [5,6] we report here the synthesis and characterizations of heterobinuclear alkali metal complexes of Cu<sup>II</sup>. <strong>Synthesis</strong> The Schiff base of OHAP and 1,2-propylenediamine were prepared by the refluxing these in 2:1 molar proportion respectively in ethanol for 10 min. The yellow Schiff base was filtered off, washed with ethanol and dried. An ethanolic solution of copper acetate hydrate (2.0g) added slowly with stirring to a hot solution of the Schiff base (3.1g). The solution, upon cooling, deposited purple copper complex which was filtered off, washed with ethanol and dried. <strong><em>Heterobinuclear complexes containing Cu(II) metal and alkali metal:</em></strong> N,N′-1,2-propylene-bis(2-hydroxyacetophenoniminato)copper(II) [CuPA] was taken in absolute alcohol in a conical flask and alkali metal salts of o-nitrophenol, dinitrophenol, trinitrophenol or were added to it in 1:1 molar proportion. The mixture was refluxed with stirring for 1-1½ hours. The characteristic colour adducts were precipitated in hot condition, which was filtered, washed with absolute ethanol, dried. <strong>Result and Discussion</strong> The Cu(II) chelate, and their alkali metal adducts are coloured solid (Table1) &amp; stable at room temp. The adducts are generally soluble in MeOH, acetone, benzene and DMF but insoluble in water. Molar conductivities of complexes in DMF at 30(+0.5) <sup>0</sup>C at conc. of 10<sup>-3</sup>M (Table 1) show low value (0.8-6.2 Ω<sup>-1</sup>cm<sup>2</sup>mol<sup>-1</sup>). This suggests the non-electrolytic [6] nature. <strong><em>Table 1.</em></strong><em> Analytical, magnetic and molar conductance data of the complexes</em> <strong> </strong> <strong> Melt.(m)/ Analysis (%) Yield<sub> </sub>(%)</strong> <strong>Compounds Colour Dec.(d) Molar μ<sub>eff.</sub> Found (Calcd.) </strong> <strong>M<sub>a</sub>PA.M<sub>b</sub>L temp. cond. C H N M<sub>a</sub> M<sub>b </sub></strong> CuPA.LiONP Mercedes red 295m 0.9 - 57.90 4.58 8.07 12.19 1.31 75.02 (58.08) (4.65) (8.13) (12.29) (1.36) CuPA.NaONP Mercedes red 296m 1.0 - 56.25 4.43 7.74 11.85 4.28 76.02 (56.34) (4.51) (7.89) (11.92) (4.32) CuPA.KONP Mercedes red 298m 0.8 1.78 54.56 4.31 7.55 11.52 7.06 75.21 (54.69) (4.38) (7.66) (11.58) (7.11) CuPA.LiDNP Purple 280d 3.4 1.76 53.35 4.01 9.89 11.25 1.19 75.69 (53.43) (4.10) (9.97) (11.31) (1.25) CuPA.NaDNP Greenish 251m 3.6 - 51.82 3.83 9.65 10.98 3.92 71.43 brown (51.95) (3.98) (9.70) (11.00) (3.98) CuPA.KDNP Brown 253m 5.5 - 50.50 3.82 9.38 10.62 6.51 68.24 (50.55) (3.88) (9.44) (10.70) (6.57) CuPA.LiTNP Golden brown 205m 5.6 - 49.36 3.54 11.46 10.42 1.11 74.20 (49.46) (3.63) (11.54) (10.47) (1.15) CuPA.NaTNP Golden brown 258m 6.0 1.73 48.12 3.47 11.11 10.13 3.62 74.70 (48.19) (3.53) (11.24) (10.20) (3.69) CuPA.KTNP Orange yellow 255m 6.2 - 46.85 3.37 10.88 9.91 6.02 72.44 (46.99) (3.45) (10.96) (9.95) (6.11) <strong> </strong> <em>IR and Electronic spectra</em> The disappearance in the spectra of metal complex as ligand of very sharp absorption peak (3500 cm<sup>-1</sup>, u<sub>OH</sub>), indicate the deprotonation of phenolic proton on complex formation. The metal complex as ligand (CuPA) exhibits the u<sub>C-O </sub>(phenolic) at 1530 cm<sup>-1</sup>, which shifts towards higher energy side (Table 2) on complexation, indicating the coordination through the phenolic O-atom [7]. The shift is expected due to maintenance of a ring current rising from electron delocalisation in chelating ring. The major shift of u<sub>C-O</sub> (phenolic) to higher frequency by ~60 cm<sup>-1</sup> in complexes indicate the presence of phenoxobridge. It is therefore suggestive that the phenolic C-O link attached a considerable amount of partial double bond character in these complexes. The bands in the far IR i.e.,463-480cm<sup>-1</sup> and 527-593cm<sup>-1</sup> in the binuclear complexes tentatively assigned by u<sub>M-O</sub> and u<sub>M-N </sub>modes respectively. These bands are not present in the Schiff base, while in metal chelates (CuPA) at region 462cm<sup>-1</sup> and 523cm<sup>-1</sup>. These assignments are based on the assumption [8] that since oxygen atom is more electronegative than nitrogen, the M-O bond tends to be more ionic than the M-N bond. Consequently M-O vibrations are expected to appear at lower frequencies. The above data confirm the coordination of oxygen atom of phenolic group and nitrogen atom of NO<sub>2 </sub>to alkali metals in all the binuclear complexes. <strong>Table 2.</strong> <em>Spectral data of metal chelate and their metal complexes</em> <em> Infrared spectra (cm<sup>-1</sup>) UV-Vis spectra</em> <em>Compound υ(C-O)( Phenolic) υ(M-N) υ(M-O) λ( nm) </em> <em> </em> CuPA 1530 523 462 230, 266, 347, 653 CuPA.KONP 1531 593 463 232, 266, 347, 653 CuPA.LiDNP 1531 527 470 219, 239, 264, 348, 653 CuPA.NaTNP 1590 565 480 231, 266, 348, 653 <em>Electronic Spectra and magnetic studies:</em> Electronic absorption bands (Table 2) for the metal chelate and their binuclear complexes are observed between 230-266 nm indicating the formation of p-p<sup>*</sup> transition in aromatic ring and C=N chromophore. The bands appearing near 348 nm due to ligand to metal charge transfer transition and band appearing near ~653 shows that there is d-d transition [9]. The magnetic moment value of CuPA is found to be 1.61 BM that correspond to the presence of one unpaired electron and square planar geometry with coordination number 4 and their adducts show <strong>μ<sub>eff. </sub></strong>values between 1.73 to 1.98 BM. This suggest that the stereochemistry of CuPA unit in the adducts almost remains same. <em>Antimicrobial activity:</em> The heterobinuclear complexes were tested for their antibacterial activity against bacteria viz., <em>E. coli</em>, <em>S. aureus</em> and fungus viz., <em>C. albicans</em> in DMF in the conc. range 25-200µgml<sup>-1</sup>. The minimum inhibitory concentration (MIC) results of the some of the complexes are shown in Fig.1.The observations show that most of adducts have great degree of activity at higher concentration against test organism and also as the concentration of these adducts increases antimicrobial activity increase gradually [10]. References: [1] Fenton, D. E.; Casellato, U.; Vigato, P. A.; Vidali, M. <em>Inrog. Chim. Acta</em> 1984, <em>95</em>, 187. [2]