Kazi Sabnam Banu

Mono- and dinuclear Zn(II) complexes of Schiff-base ligands: syntheses, characterization and studies of photoluminescence

Six Schiff-bases HL1-HL4, L5 and L6 [HL1 = 2,6-bis[1-(2-aminoethyl)pyrolidine-iminomethyl]-4-methyl-phenol, HL2 = 2,6-bis[1-(2-aminoethyl)piperidine-iminomethyl]-4-methyl-phenol, HL3 = N-{1-(2-aminoethyl)pyrolidine}salicylideneimine, HL4 = N-{1-(2-aminoethyl)piperidine}salicylideneimine, L5 = 2-benzoyl pyridine-N-{1-(2-aminoethyl)pyrolidine}, L6 = 2-benzoylpyridine-N-{1-(2-aminoethyl)piperidine}] have been synthesized and characterized. Zn(II) complexes of those ligands have been prepared by conventional sequential route as well as by template synthesis. The same complexes are obtained from the two routes as evident from routine physicochemical characterizations. All the Schiff-bases exhibit photoluminescence originating from intraligand (π–π*) transitions. Metal mediated fluorescence enhancement is observed on complexation of HL1-HL4 with Zn(II), whereas metal mediated fluorescence quenching occurs in Zn(II) complexes of L5 and L6.

Metal-Assisted Oxazolidine/Oxazine Ring Formation in Dinuclear Zinc(II) Complexes: Synthesis, Structural Aspects, and Bioactivity

Three novel dinuclear Zn(II) complexes of phenol-based compartmental macrocyclic ligands have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis. The dinuclear macrocyclic complexes 1, 2, and 3 were obtained through a 1:2 condensation reaction of 2,6-diformyl-4-methylphenol and N-(hydroxyalkyl) ethylenediamine (L(1), L(2), and L(3), respectively) in the presence of zinc(II) acetate, followed by the addition of thiocyanate anion [L(1) = N-(2-hydroxyethyl)ethylenediamine, L(2) = N-(3-hydroxypropyl)ethylenediamine, and L(3) = N-(2-hydroxypropyl)ethylenediamine]. The synthesized 18-membered macrocycles are noted to be structurally unique, and their formation proceeds with the generation of two oxazolidine side rings in complexes 1 and 3 and two oxazine side rings in 2, along with the creation of four new chiral centers in each case. Complexes 1 and 2 are characterized by a butterfly-like arrangement with the SCN ligands situated on the same side with respect to the Zn(2)O(2) moiety, whereas the centrosymmetric complex 3 exhibits a stepped arrangement with parallel methyl-phenoxy fragments (spaced at ca. 1.5 A) and trans located SCN ligands with respect to the Zn(2)O(2) core. The formation of these unusual macrocycles is considered to be zinc-mediated. Preliminary studies with the complexes show that all of them exhibit an inhibitory effect, on the cell proliferation of human stomach cancer cell line AGS, though with different degrees, where complex 3 shows the highest efficiency.

Structure and luminescence of a nitrate-bridged heterotrinuclear Cu2-Pr complex with compartmental Schiff base ligand

A unique heterotrinuclear nitrate-bridged complex of hexanitrate praseodymium(III) and dicopper(II) compartmental species has been synthesized and characterized by X-ray single crystal structure analysis. The structure determination indicates that the dinuclear copper moiety undergoes a tilted deformation (with respect to the dicopper complex) upon connection to the lanthanide species via a rare nitrate bridge. The trinuclear species is highly fluorescent owing to the presence of praseodymium.