The formation equilibria of complexes of Pb(II), Cd(II) and Hg(II) with glycylglycine were investigated pH-metrically in propylene glycol-water mixtures (0-60 % v/v) at 303 K and an ionic strength of 0.16 mol L-1. The dominant species detected were ML+ and ML2H22+ for Pb(II); MLH2+ and ML2H+ for Cd(II) and ML+, ML2 and ML2H+ are for Hg(II). The appropriateness of the experimental conditions was verified by introducing errors deliberately in the concentrations of ingredients and volume of the solution. The models containing different numbers of species were refined by using the computer program MINIQUAD75. Selection of the best fit chemical models was based on statistical parameters. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed to electrostatic and non-electrostatic forces. Distribution diagrams and plausible equilibria for the formation and possible structures of the complex species are presented.
Two new supermolecular polymers of the formula [Pb4L8(2,2'-bipy)4] 1 and [MnL2(4,4'-bipy)] 2 [HL = (4-chlorophenyloxy) acetic acid] have been synthesized and characterized by X-ray single crystal diffraction analysis, elemental analysis, fluorescence spectroscopy method and electrochemical analysis. Complex 1 is a multinuclear dimmer in which four Pb ions are linked together by the L ligands. In complex 2, each carboxyl of L bridges two Mn ions to form infinite Mn-O-C-O rods. Both in complex 1 and complex 2, π-π stacking and van der Waals' interactions make the two complexes stable, 3-D, supermolecular polymers. This work will contribute to the design and synthesis of fluorescent, supramolecular polymers.
A known synthetic route was used to prepare two known hydrazine-bridged phosphine ligands and four new ligands with variable groups on the hydrazine bridge (methyl and ethyl), as well as positions on the aryl phosphine groups (phenyl, methoxyphenyl, dimethylaminophenyl). A range of gold(I) and silver(I) complexes were synthesized utilizing these phosphine ligands. Both the phosphine-bridged dimetal and cationic bis(diphosphine) metal complexes were isolated. An interesting phenomenon of the spontaneous oxidation of gold(I) to gold(III) (and reduction of gold(IIII) to gold(I)) upon complexation with ((N,N-dimethyl)-4-aminophenyl)dialkylhydrazine ligands is described. Thirteen of the synthesized complexes were subjected to anticancer activity screening against HeLa, Jurkat, A2780, cisplatin-resistant A2780, CoLo 320 DM and MCF7. Most of the complexes were found to inhibit the cancerous cells at low µM concentrations and in some cases nM concentrations. Two of the complexes were tested for their ability to reduce the mitochondrial membrane potential of PBMC cells as a possible mechanism of action of anticancer activity.
Magnetic nano-Fe3O4 was applied in the presence of atmospheric air as a green, efficient, heterogeneous and reusable catalytic system for the synthesis of benzimidazoles via the reactions of o-phenylenediamine (1 eq) with aryl aldehydes (1 eq) in excellent yields (85-97 %) and short reaction times (30-100 min) with a proposed mechanism.