Nizamuddin Shaikh

Synthesis, crystal structures and magnetic properties of 1D polymeric [MnIII(salen)N3] and [MnIII(salen)Ag(CN)2] complexes

The syntheses, crystal structures and variable temperature (5–300 K) magnetic susceptibility measurements of two salen complexes of manganese(III) [where H2salen = N,N′-bis(salicylidene)-1,2-diaminoethane] having azido and dicyano argentate(I) as bridging ligands are reported. Both complexes belong to one-dimensional systems in which the azido functions as μ-(1,3) and Ag(CN)2− as ⋯NC– Ag–CN⋯ bridging ligands. The azido-bridged compound is antiferromagnetic with an intrachain interaction constant J = −4.52(4) cm−1 (Weng model) or J = −5.19(8) cm−1 (Fisher model), and it is a candidate to observe the Haldane gap in a S = 2 system. The silver cyanide bridged complex shows single ion behaviour of the Mn(III) ion, perhaps in combination with a very weak antiferromagnetic interaction.

Oxygenation of 4-tert-butylcatechol catalysed by a manganese(II) complex: implications for extradiol catechol dioxygenases

An N donor tetradentate manganese complex, [MnII(bispicen)Cl2] (A) [bispicen = N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine)] catalyses the oxidative cleavage of 4-tert-butylcatechol (1) in the presence of O2. The oxygenated products were isolated by t.l.c. and column chromatography and characterised by 1H-, 13C-n.m.r., DEPT, i.r. and u.v.–vis. spectroscopy. The oxygenated products as well as other spectral evidence suggest that the oxygenation occurs via a 4-tert-butylsemiquinone bound complex, [MnII(bispicen)(4-sq)]+ (4-sq = 4-tert-butylsemiquinone). 1H-n.m.r. spectroscopy suggests that the oxygenation follows multiple pathways. Isolation of the products suggests that the oxygenations proceed in an extradiol fashion and a probable mechanism is suggested. Some intradiol cleaved products have also been detected. E.s.r. spectroscopy suggests that manganese(II) is ultimately converted into the manganese(IV) species.

Synthesis and characterization of new manganese(III) complexes having N4O2 donor sets: Study of the X-ray crystal structure of [Mn(5-Br-sal-N-1,4,7,10)]ClO4 and its electron transfer kinetics with sulfur(IV)

A series of manganese(III) complexes with hexadentate Schiff base ligand having N 4 O 2 donor sets have been synthesized. One of them, [Mn(5-Br-sal-N-1,4,7,10)]ClO 4 ( 1 ), has been characterized through X-ray crystallography. In the complex cation of 1 , the manganese is coordinated by the hexadentate 5-Br-sal-N-1,4,7,10 ligand producing a distorted octahedral MnN 4 O 2 geometry with average MnO and MnN (imine), MnN (amine) bond lengths of 1.952(4), 1.988(5) and 2.244(5) A, respectively. The presence of two long MnO and MnN bonds are consistent with Jahn–Teller effects. The electron transfer reactivity of 1 with sulfur(IV) has been studied over a range of pH 2.60–6.00.