Siang Guan Teoh

Synthesis, characterization and biological properties of cobalt(II) complexes of 1,10-phenanthroline and maltol

The synthesis and characterization of two cobalt(II) complexes, Co(phen)(ma)Cl 1 and Co(ma)(2)(phen) 2, (phen=1,10-phenanthroline, ma(-)=maltolate or 2-methyl-4-oxo-4H-pyran-3-olate) are reported herein. The complexes have been characterized by FTIR, CHN analysis, fluorescence spectroscopy, UV-visible spectroscopy, conductivity measurement and X-ray crystallography. The number of chelated maltolate ligands seems to influence their DNA recognition, topoisomerase I inhibition and antiproliferative properties.

Synthesis of isatin thiosemicarbazones derivatives: in vitro anti-cancer, DNA binding and cleavage activities.

New derivatives of thiosemicarbazone Schiff base with isatin moiety were synthesized L1-L6. The structures of these compounds were characterized based on the spectroscopic techniques. Compound L6 was further characterized by XRD single crystal. The interaction of these compounds with calf thymus (CT-DNA) exhibited high intrinsic binding constant (k(b)=5.03-33.00×10(5) M(-1)) for L1-L3 and L5 and (6.14-9.47×10(4) M(-1)) for L4 and L6 which reflect intercalative activity of these compounds toward CT-DNA. This result was also confirmed by the viscosity data. The electrophoresis studies reveal the higher cleavage activity of L1-L3 than L4-L6. The in vitro anti-proliferative activity of these compounds against human colon cancer cell line (HCT 116) revealed that the synthesized compounds (L3, L6 and L2) exhibited good anticancer potency.

Synthesis of nickel(II) complexes of isatin thiosemicarbazone derivatives: in vitro anti-cancer, DNA binding, and cleavage activities

Six new nickel(II) complexes of thiosemicarbazone Schiff base with isatin moiety [Ni(L1)2–Ni(L6)2] were synthesized through reaction of Ni(II) with (Z)-2-(2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide (L1H), (Z)-2-(5-methyl-2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide (L2H), (Z)-2-(5-fluoro-2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide (L3H), (Z)-N-methyl-2-(5-nitro-2-oxoindolin-3-ylidene)hydrazinecarbothioamide (L4H), (Z)-N-methyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide (L5H), and (Z)-N-ethyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide (L6H). The structures of the Ni complexes were characterized through elemental analysis, infrared, and mass spectral data. The structure of the NiL2 complex was further characterized through single-crystal X-ray diffraction. The interaction of these complexes with calf thymus (CT-DNA) exhibited high intrinsic binding constants (Kb = 1.4 × 105–2.4 × 106 M−1), which reflected their intercalative activity toward CT-DNA. This result was also confirmed by viscosity data. Electrophoresis studies revealed that these complexes could cleave the DNA through the oxidative pathway. The in vitro anti-proliferative study establishes the anticancer potency of these compounds against human colorectal carcinoma cell line. Graphical Abstract

4,4',6,6'-Tetra-tert-butyl-2,2'-[1,2-phenyl-enebis(nitrilo-methyl-idyne)]diphenol acetone solvate.

In the Schiff base molecule of the title compound, C36H48N2O2·C3H6O, the central benzene ring makes dihedral angles of 46.64 (10) and 49.34 (10)° with the two outer benzene rings, and the two outer benzene rings form an angle of 39.13 (8)°. There are two intramolecular O—H⋯N hydrogen bonds involving the two hydroxy groups, which generate S(6) ring motifs. In the crystal structure, the Schiff base molecules are linked into a chain along the a axis by C—H⋯π interactions. The acetone solvent molecules are attached to the chain via C—H⋯O hydrogen bonds.

2-Meth­oxy-6-(6-methyl-1H-benzimid­azol-2-yl)phenol

In the title molecule, C15H14N2O2, the substituted benzene ring forms a dihedral angle of 4.15 (1)° with the benzimidazole ring system. An intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. In the solid state, molecules are linked into chains along the [001] via intermolecular bifurcated N—H⋯(O,O) hydrogen bonds, which generate R 1 2(5) ring motifs. The crystal packing is also consolidated by C—H⋯π interactions, and π–π stacking interactions between the imidazole and substituted benzene rings [centroid–centroid distance = 3.5746 (13) Å]. The methyl group attached to the benzimidazole ring system is disordered over two positions with occupancies of 0.587 (6) and 0.413 (6), suggesting 180° rotational disorder for the benzimidazole group.

(E)-4-Allyl-2-[(2-hydroxy-phen-yl)iminiometh-yl]-6-methoxy-phenolate.

The title compound, C17H17NO3, crystallizes in a zwitterionic form with cationic iminium and anionic enolate groups. The zwitterion exists in a trans configuration about the C=N bond. The dihedral angle between the two benzene rings is 13.42 (7)°. The methoxy group is almost coplanar [C—O—C—C = 2.1 (2)°] with the attached ring whereas the allyl unit is oriented at a dihedral angle of 67.9 (1)°. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, the molecules are linked into zigzag chains along [010] by O—H⋯O hydrogen bonds. In addition, weak C—H⋯π interactions are observed.

Poly[[aquadi-μ3-malonato-hexaphenyl­ditin(IV)] acetone solvate]

The asymmetric unit of the title polymeric complex, {[Sn2=(C6H5)6(C3H2O4)(H2O)]·C3H6O}n, comprises of two Sn cations, one malonate anion and a non-coordinating acetone solvent molecule. Both crystallographically independent Sn cations are five-coordinated by two O and three C atoms in a distorted trigonal-bipyrimidal geometry. One of the Sn cations is bridged by the malonate units, affording polymeric chains which run along [001]. Weak intramolecular C—H⋯π interactions stabilize the molecular structure. In the crystal structure, adjacent chains are interconnected by intermolecular O—H⋯O and C—H⋯O hydrogen bonds into a three-dimensional supramolecular structure. A weak intermolecular C—H⋯π interaction is also observed.

[3-(Dimethyl­amino)benzoato]triphenyl­tin(IV)

In the title compound, [Sn(C6H5)3(C9H10NO2)], the Sn atom is coordinated by three phenyl groups and a carboxylate anion in a distorted tetrahedral geometry. An intramolecular C—H⋯O interaction forms an S(7) ring motif. The dihedral angles between the benzoate group and the other three phenyl rings are 76.94 (8), 66.82 (8) and 42.34 (9)°. The crystal structure is further stabilized by intermolecular C—H⋯π interactions.

(Z)-N-Methyl-2-(5-nitro-2-oxoindolin-3-yl­idene)hydrazinecarbothio­amide

In the title compound, C10H9N5O3S, an intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked via N—H⋯S hydrogen bonds into a zigzag chain along the b axis. C—H⋯O interactions are observed between the chains.

4-(5,6-Dihydro­benzimidazo[1,2-c]quinazolin-6-yl)benzene-1,3-diol dimethyl sulfoxide monosolvate

In the title solvated benzimidazole compound, C20H15N3O2·C2H6OS, both the benzimidazole fused-ring system and the complete dimethyl sulfoxide solvent molecule are disordered over two sets of sites, in 0.750 (5):0.250 (5) and 0.882 (4):0.118 (4) ratios, respectively. The conformation of the pyrimidine ring is close to a half-chair for the major disorder component, whereas for the minor component it is close to a boat. The dihydroxyphenyl ring is almost perpendicular to the mean plane of the benzimidazole ring [dihedral angle = 87.3 (2)° for the major disorder component and 88.3 (5)° for the minor disorder component]. In the crystal, molecules are linked into layers parallel to (110) by O—H⋯N and C—H⋯O hydrogen bonds. A bifurcated O—H⋯(O,S) bond links the benzimidazole and solvent molecules.