Shaukat Shujah

Syntheses, structural characteristics, and antimicrobial activities of new organotin(IV) 3-(4-bromophenyl)-2-ethylacrylates

New organotin(IV) carboxylates, [n-Bu2SnL2] (1), [Et2SnL2] (2), [Me2SnL2] (3), [n-Oct2SnL2] (4), [n-Bu3SnL] n (5), [Me3SnL] n (6), and [Ph3SnL] n (7), where L = 3-(4-bromophenyl)-2-ethylacrylate, were synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR (1H, 13C, and 119Sn). Spectroscopic studies confirm coordination of L to the organotin moiety via COO group. Single-crystal X-ray analysis reveals bridging mode of coordination in 6. Packing diagram established a supramolecular cage-like structure for 6 due to Sn–O interactions (3.287 Å). Subsequent antimicrobial activities proved them to be active biologically.

pH-dependent redox mechanism and evaluation of kinetic and thermodynamic parameters of a novel anthraquinone

The redox behavior of 1,4-dihydroxy-2-(3-hydroxy-3-(trichloromethyl)pentyl)-8-methoxyanthracene-9,10-dione (HCAQ) was investigated at a glassy carbon electrode over a wide pH range of 3–12 by using cyclic, square wave and differential pulse voltammetry (CV, SWV and DPV). CV results of HCAQ obtained at different temperatures were used for the evaluation of thermodynamic parameters like ΔG#, ΔH# and ΔS#. The values of diffusion coefficient and heterogeneous electron transfer rate constant were also determined by CV. Limits of detection and quantification were determined by SWV. The numbers of electrons and protons involved in the oxidation processes were evaluated by DPV. The value of apparent acid dissociation constant (pKa) was obtained from the intersection of two linear segments of the Ep vs. pH plot. The effect of pH on the UV-visible spectral response was also monitored which allowed the determination of pKa of HCAQ. The values of apparent acid dissociation constant obtained from electrochemical techniques and electronic absorption spectroscopy were found to be in very good agreement. On the basis of experimental results, a pH-dependent oxidation mechanism was proposed in order to provide useful insights into the unexplored pathways by which anthraquinones exert their biochemical action.

Synthesis and structural characterization of monomeric and polymeric supramolecular organotin(IV) 4-chlorophenylethanoates

Four monomeric [n-Bu2SnL2 (1), Et2SnL2 (2), Me2SnL2 (3), and n-Oct2SnL2 (7)] and three polymeric {[n-Bu3SnL]n (4), [Me3SnL]n (5), and [Ph3SnL]n (6)} organotin(IV) carboxylates, where L = 4-chlorophenylethanoate, were synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR (1H, 13C, and 119Sn). Compounds 2 and 5 were also analyzed by X-ray single-crystal analysis showing monomeric and zigzag structures, respectively. Two types of O…H (2.641 Å) and Cl…H (2.943 Å) non-covalent interactions generate a 2-D supramolecular structure for 2. Layer-by-layer supramolecular structure was observed for 5 in which polymeric chains are connected via non-covalent interactions {Cl…H (2.869 Å), H…π (2.899 Å)}, and unconventional dihydrogen {H…H (2.381 Å)} interactions. Four monomeric and three polymeric organotin(IV) carboxylates have been synthesized and characterized by elemental analysis, FT-IR, multinuclear NMR (1H, 13C, and 119Sn), and X-ray single-crystal analysis. The latter technique revealed the monomeric 2-D supramolecular structure for Et2Sn(IV) derivative and polmeric nature which form layer-by-layer supramolecular structure in case of Me3Sn(IV) derivative.

Synthesis, crystal structure, DNA binding and molecular docking studies of zinc(II) carboxylates

New zinc(II) carboxylate complexes [Zn(3-F-C6H4CH2COO)2]n (1), [Zn3(3-F-C6H4CH2COO)6(Phen)2] (2) and [Zn3(3-F-C6H4CH2COO)6(bipy)2] (3) were synthesized and characterized by atomic absorption, single crystal structural analysis and IR studies. Complex 1 crystallizes as a coordination polymer constituting a web of μ-η1,η1 carboxylate bridged tetrahedral zinc centers. Complexes 2 and 3 comprise trinuclear zinc centers with two terminal fivefold coordinated slightly distorted square-pyramidal and central sixfold coordinated octahedral zinc centers. The complexes were also assessed for their DNA binding ability by UV/-Vis spectroscopy and their behavior rationalized theoretically by molecular docking studies. A DNA binding study has shown groove binding interactions with the complexes.

Antimicrobial efficiency of diorganotin(IV) bis-[3-(4-chlorophenyl)-2-methylacrylate]

Abstract Four new diorganotin(IV) carboxylates, [n-Bu2SnL2] (1), [Et2SnL2] (2), [Me2SnL2] (3) and [n-Oct2SnL2] (4), where L = 3-(4-chlorophenyl)-2-methylacrylate, were synthesized and characterized by elemental analysis, FT-IR, multinuclear NMR (1H, 13C, and 119Sn) and X-ray single crystal analysis for 1. A chelating bidentate ligand and six-coordinate tin centers were confirmed in the solid state by IR for all complexes and for 1 by X-ray single crystal analysis. The NMR study has shown a decrease in the coordination number of tin in solution. The complexes were screened for their in vitro antibacterial and antifungal activities. A compromised lipo/hydrophilicity and a diffusion controlled antimicrobial activity was shown by the complexes in the order 1 > 2>3 > 4. Molecular docking studies have shown hydrogen bonding and hydrophobic interactions for 1 with the target proteins of the antimicrobial strains. Graphical Abstract

Supramolecular homobimetallic bis-diorganotin(IV) complexes of ditopic oxygen nitrogen donor ligand: synthesis, spectroscopic characterization, crystal structure and biological screening

Six new homobimetallic bis-diorganotin(IV) complexes: [Me2Sn]2L (1), [Et2Sn]2L (2), [n-Bu2Sn]2L (3), [Ph2Sn]2L (4), [Oct2Sn]2L (5) and [n-BuClSn]2L (6) (H4L=N1′, N6′-bis(2-hydroxybenzylidene)adipodihydrazide) have been synthesized and structurally characterized by means of elemental analysis, mass spectroscopy, FT-IR, NMR (1H, 13C{1H}, 119Sn) and single-crystal X-ray diffraction. Spectroscopic studies indicate coordination of the ligand to the diorganotin(IV) moieties via iminolic oxygen, nitrogen and phenolic oxygen atoms generating pentacoordinated tin centers. Single-crystal X-ray analysis of (1) revealed homobimetallic nature of complex with dimethyltin moieties oriented in trans-conformation. The ligand is non-planar with each Sn atom in a distorted square pyramidal coordination geometry. Packing diagrams suggest the essential role of C–H…N and C–H…O interactions in generating supramolecular assembly. The ligand and complexes were screened for in vitro antimicrobial activity and cytotoxicity. Compound (4) exhibits highest cytotoxicity.

6-[(2,4-Di-methyl-anilino)methyl-idene]-2-hy-droxy-cyclo-hexa-2,4-dienone.

In the title compound, C15H15NO2, the dihedral angle between the aromatic rings is 5.86 (6)°, and an intramolecular N—H⋯O hydrogen bond generates an S(6) motif, which helps to stabilize the enamine–keto tautomer. An intramolecular O—H⋯O hydrogen bond also occurs. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds generate R 2 2(10) loops. A C—H⋯O interaction links the dimers into [010] chains and aromatic π–π stacking [centroid–centroid separation = 3.6131 (9) Å] also occurs.