Abhijit Pal

Chiral synthesis of a mononuclear nickel(II) complex formed from an achiral tripodal amine ligand: spontaneous resolution.

A neutral chiral mononuclear Ni(II) complex cis-[Ni(NCS)(2)(tren)] (1) [tren = tris(2-aminoethyl)amine] has been isolated in a reaction of nickel(II) salt with an achiral ligand tren and NH(4)SCN in a MeOH-H(2)O (1:1) mixture. The crystal structure of 1 reveals the encapsulation of Ni(II) ions in a facial {NiN(6)} coordination environment that includes four nitrogen donors from the tetradentate chelate tren and two nitrogen donors from two cis-NCS (monodentate) ligands. The chirality of 1 arises from symmetry breaking of the cis-(NCS)(2)-Ni(II) octahedral complex by the tetradentate chelate tren. Compound 1 exhibits both its enantiomers in a DMF solution through a Pfeiffer effect when l- and d-arabinose are used as environment substances. The particular synthesis, described herein, offers total spontaneous resolution, as is evidenced from crystal structure and circular dichroism spectral studies.

Structural systematics of some metal complexes with 4,5-diazafluoren-9-one

AbstractSynthesis and X-ray structural characterization of three complexes of type cis-[M(dafone)2(NCS)2] (M = Co(II), 1; Ni(II), 2; Zn(II), 3; dafone = 4,5-diazafluoren-9-one) and a polymer cis-[Cd(dafone)(NCS)2]n (4) have been reported. Each of the four complexes is crystallized in orthorhombic crystal system. Structural study reveals that each metal(II) centre in the four complexes adopts distorted octahedral geometry with MN6 chromophore in 1-3 and MN4S2 chromophore in 4. The room temperature steady-state fluorescent intensity of dafone in dimethyl formamide at 402 nm is found to be quenched in these reported dafone complexes (1-4). Graphical AbstractSynthesis and X-ray structural characterization of three complexes of type cis-[M(dafone)2(NCS)2] (M = Co(II), 1; Ni(II), 2; Zn(II), 3; dafone = 4,5-diazafluoren-9-one) and a polymer cis-[Cd(dafone)(NCS)2]n (4) have been reported. The fluorescent intensity of dafone in DMF is found to be quenched in these reported dafone complexes (1-4).

Synthesis, spectroscopic, and crystallographic characterizations of an antiferromagnetically coupled, oxobridged trinuclear manganese(IV) cluster [Mn3O4(H2O)2(phen)4](NO3)4 · 3H2O [phen = 1,10-phenanthroline]

Design and synthesis of a triangular manganese compound, [Mn3O4(H2O)2(phen)4](NO3)4 · 3H2O (1) with mono-µ-oxo and di-µ-oxo, is described. The complex has been characterized by elemental analysis, spectroscopy, single crystal and powder diffraction measurements, thermogravimetric analysis, etc. Bond Valence Sum calculations and X-ray photoelectron spectroscopy reveal that each manganese at each vertex of the triangle is +IV oxidation state. Variable temperature magnetic measurements show strong antiferromagnetic coupling between metal ions with the following set of parameters: g = 1.99, J 1 = −50.0 cm−1, and J 2 = −90.2 cm−1 (where J 1 describes the interaction across the two mono-µ-oxo bridges and J 2 is the exchange coupling across the di-µ-oxo bridge). The compound breaks down in three steps when heated from room temperature to 900°C. The final ash of the compound is confirmed by infrared spectrum with standard MnO2.

DNA binding and cleavage activity of a structurally characterized Ni(II) Schiff base complex

AbstractSynthesis and characterization of a mononuclear Ni(II) compound [Ni(L)(H2O)2](NO3)2 [L = N,N’-bis((pyridine-2-yl)phenylidene)-1,3-diaminopropan-2-ol] (1) is reported. 1 crystallizes in triclinic P-1 space group with a = 8.1911(2) Å, b = 11.6624(3) Å, c = 16.5356(4) Å and α = 108.8120(10)°, β = 91.2010(10)°, γ = 91.1500(10)°. The binding property of the complex with DNA has been investigated using absorption and emission studies, and viscosity experiment. The binding constant (Kb) and the linear Stern-Volmer quenching constant (Ksv) of the complex have been determined as 9.23 × 104 M−1 and 2.0 × 104 M−1, respectively. Spectroscopic and hydrodynamic investigations revealed groove or electrostatic nature of binding of 1 with DNA. 1 is also found to induce oxidative cleavage of the supercoiled pUC 18 DNA to its nicked circular form in a concentration dependent manner. Graphical AbstractSynthesis and characterization of a mononuclear Ni(II) complex [Ni(L)2(H2O)2](NO3)2 [L = N,N′-bis((pyridine-2-yl)phenylidene)-1,3-diaminopropan-2-ol] (1) is reported. 1 crystallizes in P-1 space group. Spectroscopic and hydrodynamic investigations on the binding property of the complex with DNA have been revealed groove or electrostatic nature of binding of 1 with DNA. 1 is also found to induce oxidative cleavage of the supercoiled pUC 18 DNA to its nicked circular form in a concentration dependent manner.