Munirathinam Nethaji

Synthesis, crystal structures and properties of ternary copper(II) complexes having 2,2′-bipyridine and α-amino acid salicylaldiminates as models for the type-2 sites in copper oxidases

Abstract Ternary copper(II) complexes [Cu(salgly)(bpy)]·4H 2 O ( 1 ·4H 2 O), [Cu(salala)(bpy)]·4H 2 O·( 2 ·4H 2 O) and [Cu(salphe)(bpy)] ( 3 ), where salgly, salala and salphe are tridentate Schiff base ligands derived from the condensation of salicylaldehyde with glycine, l -alanine and l -phenylalanine, respectively, and bpy is 2,2′-bipyridine, are prepared and structurally characterized. Crystal structures of the complexes display a distorted square-pyramidal (4+1) coordination geometry in which the ONO-donor Schiff base is bonded to the metal in the basal plane. The chelating bpy ligand displays axial-equatorial mode of bonding. Complexes 1 and 2 show chemically significant hydrogen bonding interactions. In addition, complex 2 exhibits π–π stacking, while complex 3 shows attractive CH(imine)–π (phenyl) non-covalent interactions. The one-electron paramagnetic complexes display axial EPR spectra in DMF-glass at 77 K indicating a {d x 2 − y 2 } 1 ground state. The complexes show a d–d band near 670 nm and a charge transfer band near 440 nm in methanol. The complexes are redox active and exhibit a quasi-reversible Cu(II)–Cu(I) couple in DMF-0.1 M TBAP near −0.8 V versus SCE. The complexes are catalytically active in the oxidation of ascorbic acid by dioxygen. The process which is effective with a mole ratio of ascorbic acid to complex as approximately 30, models the ascorbate oxidation property of the type 2 sites in ascorbate oxidase and dopamine β-hydroxylase. The complexes with a N 3 O 2 coordination environment model the active site structure in amine oxidase and mediate deamination reactions in which benzylamine gets oxidized to benzaldehyde in the presence of hydrogen peroxide.

Iron(III) Schiff base complexes of arginine and lysine as netropsin mimics showing AT-selective DNA binding and photonuclease activity

Iron(III) complexes [Fe(L)(2)]Cl (1-3), where L is monoanionic N-salicylidene-arginine (sal-argH for 1), hydroxynaphthylidene-arginine (nap-argH for 2) and N-salicylidene-lysine (sal-lysH for 3), were prepared and their DNA binding and photo-induced DNA cleavage activity studied. Complex 3 as its hexafluorophosphate salt [Fe(sal-lysH)(2)](PF(6)).6H(2)O (3a) was structurally characterized by single crystal X-ray crystallography. The crystals belonged to the triclinic space group P-1. The complex has two tridentate ligands in FeN(2)O(4) coordination geometry with two pendant cationic amine moieties. Complexes 1 and 2 with two pendant cationic guanidinium moieties are the structural models for the antitumor antibiotics netropsin. The complexes are stable and soluble in water. They showed quasi-reversible Fe(III)/Fe(II) redox couple near 0.6V in H(2)O-0.1M KCl. The high-spin 3d(5)-iron(III) complexes with mu(eff) value of approximately 5.9 mu(B) displayed ligand-to-metal charge transfer electronic band near 500nm in Tris-HCl buffer. The complexes show binding to Calf Thymus (CT) DNA. Complex 2 showed better binding propensity to the synthetic oligomer poly(dA).poly(dT) than to CT-DNA or poly(dG).poly(dC). All the complexes displayed chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent and cleaved supercoiled pUC19 DNA to its nicked circular form. They exhibited photo-induced DNA cleavage activity in UV-A light and visible light via a mechanistic pathway that involves the formation of reactive hydroxyl radical species.

Pillar height dependent formation of unprecedented Pd8 molecular swing and Pd6 molecular boat via multicomponent self-assembly

Three-component self-assembly of a cis-blocked 90° Pd(II) acceptor with a mixture of a tetraimidazole and a linear dipyridyl donor self-discriminated into unusual Pd(8) molecular swing (1) and Pd(6) molecular boat (2), which are characterized by single-crystal X-ray diffraction analysis; their ability to bind C(60) in solution is established by fluorescence titration.

Transition metal complexes of 3-aryl-2-substituted 1,2-dihydroquinazolin-4(3H)-one derivatives: new class of analgesic and anti-inflammatory agents.

Five-coordinate, neutral transition metal complexes of newly designed pyridine-2-ethyl-(3-carboxylideneamino)-3-(2-phenyl)-1,2-dihydroquinazolin-4(3H)-one (L) were synthesized and characterized. The structure of ligand is confirmed by single crystal X-ray diffraction studies. The compounds were evaluated for the anti-inflammatory activity by carrageenan-induced rat paw edema model while their analgesic activity was determined by acetic acid-induced writhing test in mice wherein the transition metal complexes were found to be more active than the free ligand.

Transfer hydrogenation of acetophenone promoted by (arene)ruthenium(II) reduced Schiff base complexes: an X-ray structure of [(η6-p-cymene)RuCl(OC6H4-2-CH2NHC6H4-p-Me)]

Arene ruthenium(II) reduced Schiff base complexes of formulation

Short-bite chiral diphosphazanes derived from (S)-α-methyl benzyl amine and their Pd, Pt and Rh metal complexes

[(\eta^6-p-cymene)RuCl(L^n)]

A facile entry into a new class of spiroheterocycles: synthesis of dispiro[oxindolechromanone/flavanone/tetralone]pyrroloisoquinoline ring systems

(1–5, n=1–5) were prepared by reacting

Synthesis, crystal structure and catalytic properties of (p-cymene)ruthenium(II) azophenol complexes: azophenyl to azophenol conversion by oxygen insertion to a ruthenium---carbon bond

[(\eta^6-p-cymene)RuCl_2]_2

SYNTHETIC, SPECTROSCOPIC AND CRYSTALLOGRAPHIC STUDIES OF HETEROFUNCTIONAL DIPHOSPHAZANE LIGANDS

with

Late transition metal complexes derived from diphosphazane monosulfide ligands: X-ray crystal structures of [Ru3(μ-CO)(CO)7(μ3-S){Ph2PN((S)-*CHMePh)PPh2-κ2P,P}] and [Rh(CO)Cl{Ph2PN((S)-*CHMePh)P(S)Ph2}-κ2P,S] ☆: Part 16. Organometallic chemistry of diphosphazanes

HL^n