The gas‐phase‐optimized geometry of newly synthesized and characterized diorganotin(IV) 2‐chloridophenylacetohydroxamate complexes of composition [Me2Sn(HL)2] (I) and [n‐Bu2Sn(HL)2] (II) (where KHL = potassium 2‐chloridophenylacetohydroxamate (2‐ClPhAHK); [Me2Sn(2‐ClC6H4CH2CONHO)2] (I) and [n‐Bu2Sn(2‐ClC6H4CH2CONHO)2] (II) computed by B3LYP/6‐311++G(d,p) method has shown these to be distorted octahedral. Bonding through carbonyl and hydroxamic oxygen atoms (O, O coordination) has been inferred from a comparison of computed important bond lengths (CO, CN, and NO) of complexes with that of free ligand. The SnO bond lengths in complexes are suggestive of weak coordinate (through carbonyl CO) and strong covalent (through hydroxamic NO) bonding of the ligand. The magnitude of CSnC bond angles involving two methyl/n‐butyl groups is suggestive of cis‐conformation at tin metal. The thermodynamic parameters (G, H, S, E, Cv, and U) of complexes have been computed. From the energies of frontier molecular orbitals (HOMO–LUMO), the reactivity descriptors, namely, ionization potential, electron affinity, chemical potential (μ), hardness (η), softness (S), electronegativity (χ), and electrophilicity index (ω) have been calculated. The computed vibrational frequencies and 1H NMR chemical shifts have substantiated the molecular structure of complexes. © 2019 Wiley Periodicals, Inc.

The new diorganotin (IV) complexes of composition [Me2SnCl(3,5‐(NO2)2C6H2(OH)CONHO)] (I) and [n‐Bu2SnCl(3,5‐(NO2)2C6H2(OH)CONHO)] (II) have been synthesized by the reactions of Me2SnCl2 and n‐Bu2SnCl2 with potassium 3,5‐dinitrosalicylhydroxamate [3,5‐(NO2)2C6H2(OH)CONHOK]‐ a ligand of biological significance bearing –NO2 and –OH substituents presumed to yield complexes with efficient bioactivity. The complexes have been characterized by elemental analyses, IR, 1H, 13C and 119Sn NMR and mass spectrometry in order to study the ligational behavior and probale geometry around tin as the ligand might show different bonding modes and geometry in complexes. The geometries of (I) and (II) have been computed using B3LYP/6–31 + G(d,p) set by DFT method and the vibrational frequencies, 1H and 13C NMR spectra compared with the experimental data. A comparison of computed bond lengths (C=O, C‐N, and N‐O) of (I) and (II) with that of free ligand, the Sn‐O bond lengths, bond angles coupled with 119Sn NMR and IR spectral data have suggested coordination through carbonyl and hydroxamic oxygens (O, O coordination) displaying five‐coordinate distorted trigonal‐bipyramidal geometry around tin. The thermal behavior of (I) and (II) has been studied by thermogravimetric techniques (TGA, DTG, DTA) and various kinetic parameters have been calculated. The electrochemical behavior of ligand, (I) and (II) studied by cyclic voltammetric technique has shown ligand centered redection. The HOMO‐LUMO energies and orbitals, global reactivity descriptors, various thermodynamic parameters and dipole moment (μ) have been computed to determin the molecular properties of complexes. The in vitro antimicrobial activity assay against bacteria and fungi by MIC method has indicated higher potency of (I) than (II). The in vitro cytotoxicity on human muscle rhabdomyosarcoma (RD) by MTT method and the antioxidant potential by DPPH free radical scavenging showed higher inhibitory effect of complexes than ligand.

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Conformationally flexible ligands of appropriate size and denticity can wrap to a metal ion with high stability. In this perspective, a new tripodal siderophore‐mimic hexadentate chelator, N‐[3,5‐bis[(1‐hydroxy‐6‐oxo‐pyridine‐2‐carbonyl)amino]cyclohexyl]‐1‐hydroxy‐6‐oxo‐pyridine‐2‐carboxamide, (TACH‐1,2‐HOPO), which contains three 1,2‐hydroxypyridinone units attached to a cyclohexane ring through amide linkage at 1,3 and 5 positions, has been designed and synthesized. The characterization of the ligand was carried out through various techniques like FT‐IR, 1H NMR, 13C NMR, ESI‐MS, and electronic spectroscopy. In an aqueous medium, the solution thermodynamics and photophysical properties of the chelator and its La3+, Gd3+, and Lu3+ complexes were determined experimentally as well as theoretically. The pKa values for the ligand were found to be 8.40, 5.74, and 5.39. Formation of lanthanide complexes of type MLH3, MLH2, MLH, ML, and ML.(H2O)x (x=1,2 and 3) was perceived, and the log βmlh for various partially and fully protonated and hydrated lanthanide complexes are reported. Theoretical calculations by DFT supported the experimental results. The experimentally determined protonation constants gave the same trend of ΔG0 values obtained by DFT; also, the theoretically calculated FT‐IR, 1H, 13C NMR, electronic, and excitation spectral data are in covenant with experimental findings. The bonding behavior between the lanthanide ions and the TACH‐1,2‐HOPO explicated by implication of NBO, Morokuma Ziegler energy decomposition analysis (ETS‐NOCV), propose the Ln−L bonds are less covalent with the trend Lu>Gd>La.