Cationic chromium urea complex as potential anion binder for nitro substituted-phenolates

Abstract

Three new complexes, [Cr(CO(NH2)2)6](PNP)3(1), [Cr(CO(NH2)2)6](DNP)3·3H2O (2), [Cr(CO(NH2)2)6](TNP)3·3DMSO (3) (where PNP: 4-nitrophenolate, DNP: 2,4-dinitrophenolate, TNP: 2,4,6-trinitrophenolate) have been synthesized by reacting [Cr(CO(NH2)2)6]Cl3.3H2O with sodium salts of nitro substituted-phenolates (in 1:3 molar ratio) in aqueous medium. The new complexes have been characterized by analytical and spectroscopic studies (FT-IR, UV-Vis). The thermal stability of the complexes has also been determined using thermogravimetric analysis (TGA). The binding property of complex cation, [Cr(CO(NH2)2)6]3+ with nitrophenolates have been studied using standard UV–vis spectroscopic titrations method in aqueous medium (log β for PNP:11.9409, DNP:11.3102 and TNP:11.5077). The crystal structure of 3 was determined and it revealed the presence of one cation, three anions and three DMSO molecules. This complex is stabilized by intra-((urea) O…H-NH (urea)) and intermolecular H-bonding ((urea) NH…OC/ONO (picrate)/ OS (DMSO)) interactions apart from electrostatic forces of attractions. Further, antimicrobial activity of all the complexes has been tested using strain of Gram negative (E. coli, K. pneumoniae, S. typhi), strain of Gram positive bacteria (S. epidermidis, B. subtilis) and fungus (F. moniliforme, A. alternata). Complex 3 shows maximum activity against S. epidermidis and K. pneumoniae although all the compounds are inactive against fungus.