Researchers have suggested that the reason behind infertility is pernicious effect of broad spectrum pesticides on non target, beneficial microorganism of soil. Here, studying the chelating effect of selective organophosphate and carbamate pesticides with essential metal ions, at all possible combinations of three different pH (4 ± 0.05, 7 ± 0.05 and 9 ± 0.05) and three different temperatures (15 ± 0.5°C, 30 ± 0.5°C and 45 ± 0.5°C), shows very fast rate of reaction which further increases with increase of pH and temperature. Carbonyl oxygen of carbamate and phosphate oxygen of organophosphate were found to be common ligating sites among all the complexes. Formed metal complexes were found to be highly stable and water insoluble on interaction with essential metal ions in solvent medium as well as over silica. Density functional theory (DFT) calculations not only reinforced the experimental observations, but, after a wide computational conformational analysis, unraveled the nature of the high stable undesired species that consist of pesticides complexed by metal ions from the soil. All in all, apart from the direct toxicity of pesticides, the indirect effect by means of complexation of free metal ions impoverishes the soil.

By the nucleophilic attack of phenylhydrazine on acephate in aqueous medium, a stable product N′-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester (1) was obtained and characterized by elemental, spectral and thermal analysis. Thermodynamic parameters, Ea, ΔH°, ΔS° and ΔG°, have found to be 62.15, −67.95, −0.068 and −20.05 kJ mol−1 according to the Coats–Redfern equation. Analysis of interaction of 1 with BSA protein was done by using the UV–Vis and FTIR spectroscopic methods. The observed binding constants was 1.12 (±0.09) × 104 M−1. The biological effect of 1 was checked on different plant growth-promoting (PGPR) strains such as Rhizobium leguminosarum, Pseudomonas fluorescens, Arthrobacter citreus, Bacillus brevis and Salmonella typhimurium and compared with parent molecule acephate where 1 has shown less toxicity against PGPRs as compared to acephate. The experimental results for geometric parameters and values of peak position in IR spectra have found to match excellently with the computational studies performed by GAMESS software package. Theoretically, twelve new analogs of 1 were prepared and their comparative reactivity (HOMO–LUMO energy) and biodecomposition (on the basis of polarizability) is discussed.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-015-0313-6) contains supplementary material, which is available to authorized users.

CitationKumar V, Chawla M, Cavallo L, Basit Wani A, Manhas A, et al. (2017) Complexation of trichlorosalicylic acids by alkaline and first row transition metals as a switch for their antibacterial activity. Inorganica Chimica Acta. Available: http:// dx.NirajUpadhyay, Complexation of trichlorosalicylic acids by alkaline and first row transition metals as a switch for their antibacterial activity, Inorganica Chimica Acta (2017), doi: http://dx. Abstract:3,5,6-trichlorosalicylic acid (TCSA) does not show a good antibacterial activity. In contrast, here metal complexes with TCSA have shown better antibacterial activity for selected bacterial strains with a good degree of selectivity. Amongst the eight synthesized essential metal complexes complexed with TCSA, Mn(II)-TCSA and Ni(II)-TCSA have been found to be more effective with MIC range 20-50 µg/L as compared to control (chloramphenicol). The activity of an individual complex against different microbes was not found to be identical, indicating the usage of an individual metal chelate against a targeted bacterial strain. Further, the protein (BSA) binding constant of TCSA and its metal complexes were determined and ordered as Ca(II)-TCSA > Cu(II)-TCSA > Mg(II)-TCSA >> Mn(II)-TCSA >> Zn(II)-TCSA >>> Ni(II)-TCSA >>> Co(II)-TCSA > Fe(II)-TCSA > TCSA. The present study has confirmed enhanced antibacterial activities and binding constants for metal chelates of TCSA as compared to free TCSA, which seems directly related with the antioxidant activities of these complexes. Further, bearing the ambiguity related to the structural characterization of the metal complexed with TCSA ligands, DFT calculations have been used as the tool to unravel the right environment around the metals, studying basically the relative stability of square planar and octahedral metal complexes with TCSA.

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