Nijhuma Mondal

Synthesis and structural characterization of mixed ligand η1-2-hydroxyacetophenone complexes of cobalt(III)

Abstract A tridentate Schiff base ligand [(CH3)2NCH2CH2NC(CH3)C6H4OH)] (LH) has been synthesized from 2-hydroxyacetophenone and 2-dimethylaminoethylamine. This ligand forms the neutral complexes [Co(L)(N3){o-(CH3CO)C6H4O}] (1) and [Co(L)(SCN){o-(CH3CO)C6H4O}]·1/2H2O (2) in presence of equivalent amount of Co(II) acetate, and sodium azide for 1 and sodium thiocyanate for 2. The complexes have been characterized by spectroscopic and crystallographic methods. The coordination geometry around Co(III) in both the complexes is distorted octahedral with one tridentate ligand L, one bidentate 2-hydroxyacetophenone and one monodentate azide for 1 and thiocyanate for 2. The azide and thiocyanate ligands in the two complexes occupy different positions relative to the coordination sites of L.

Synthesis, characterization and crystal structures of some four coordinated nickel(II) complexes with tridentate Schiff base ligands

Abstract A number of Ni(II) complexes with tridentate Schiff base ligands with a N2O donor set and coordinating NNN− and SCN− anions have been synthesized and characterized by analytical, spectroscopic and electrochemical techniques. X-ray structure analyses of three of these complexes [L1Ni(NNN)] (1), [L2Ni(NNN)] (2) and [L3Ni(NCS)] (6) [HL1=Me2NCH2CH2N(Me)C6H4OH, HL2=Et2NCH2CH2N(H)C6H4OH, HL3=Et2NCH2CH2N(H)C6H3BrOH] show that the nickel atom has a square planar geometry. Thermogravimetric studies show multiple step decomposition, and electrochemical studies indicate that the complexes are irreversibly oxidized to Ni(III) species, which are unstable and undergo rapid decomposition.

Synthesis and characterization of cyano-bridged polynuclear [Cu(dmpn)2]3[Co(CN)6]2·12H2O and trinuclear [Cu(dmpn)2]2[Co(CN)6]·ClO4·3H2O complexes

Abstract Two new heteronuclear bimetallic assemblies [Cu(dmpn)2]3[Co(CN)6]2·12H2O (1) and [Cu(dmpn)2]2[Co(CN)6]·ClO4·3H2O (2) have been prepared and crystal structures have been solved. The one-dimensional (1D) polymeric chain of 1 extended through Co–CN–Cu–NC–Co linkages. The chains are finally linked by hydrogen bonds giving rise to a unique step shaped two-dimensional (2D) network. In the crystal of 1, all the copper(II) and cobalt(III) ions have distorted octahedral geometry. In the complex 2, the copper(II) and cobalt(III) centres are linked together through cyano-bridges and both the copper(II) ions have a distorted square pyramidal geometry. Of the six CN− groups around the cobalt atom in complex 2, two coordinate to copper atoms of adjacent [Cu(dmpn)2]2+ moieties leading a non-linear trinuclear unit, of the remaining four CN− groups two are free and the other two interact through hydrogen bonds with water molecules present in each asymmetric unit. The presence of water molecules gives rise to an extensive H-bonded molecular assembly.

Synthesis and structural characterization of [Ni(Me2NCH2CH2CH2N=CHC6H4O)2]

The synthesis, properties, and X-ray crystal structure of a Ni(II) complex of the tridentate Schiff base ligand Me2NCH2CH2CH2N=CHC6H4OH(LH) are described. The complex crystallizes in the monoclinic space group P21/c, with a = 10.180(2), b = 15.169(3), c = 15.293(4) Å, β = 106.69(2)°, and Z = 4. The Ni atom shows a distorted fac-octahedral geometry, with the two Ni—N(Me2) bonds being significantly longer than the two Ni—N(imino) bonds, 2.284(9), 2.310(9) vs. 2.051(2), 2.055(2) Å.

Synthesis, characterization and crystal structure of cyano-bridged dinuclear copper–iron complexes

Abstract Two new cyano-bridged dinuclear complexes [Cu(dmen)2Fe(CN)5(NO)] (1) and [Cu(dmpn)2Fe(CN)5(NO)] (2) (where dmen=2-dimethylaminoethylamine and dmpn=1 dimethylamino-2-propylamine) have been synthesized. The complexes have been characterized by elemental analyses, spectroscopic studies and magnetic moment measurements, and the structures were determined using single-crystal X-ray diffraction. In both complexes the copper(II) ion is coordinated by five nitrogen atoms and has distorted square-pyramidal geometry. The iron(II) center is in a distorted octahedral environment and is linked to copper(II) through a cyano-bridge.

Synthesis and crystal structure of mononuclear copper (II) complex of tridentate Schiff base ligand and its ferrocyanide-bridged pentanuclear complex

Abstract The compound [Cu(L)(OAc)H2O] (1) (HL is a tridentate Schiff base derived from 2-hydroxyacetophenone and 2-dimethylaminoethylamine) has been synthesized and its crystal structure has been determined. The addition of [Fe(CN)6]4− to [Cu(L)(OAc)H2O] gives the pentanuclear complex [(CuL)4Fe(CN)6]·16H2O (2). Four Cu(II) centres are joined to a single Fe(II) centre via cyanide bridges. The two remaining cyanide groups on the iron are terminal. The presence of sixteen water molecules per pentanuclear complex has been confirmed by thermogravimetric analysis and the activation energy for the elimination of water has been computed and found to be 57 kJ mol−1.

Synthesis, crystal structure and magnetic properties of a new oxalato-bridged binuclear copper(II) complex with a tridentate Schiff base ligand

Abstract A new oxalato-bridged binuclear copper(II) complex, [{Cu(L)} 2 OX] ( 1 ) (L=2- N -(2′-pyridylimine)benzoic acid) has been synthesised and characterised by ESR and IR spectra and variable temperature magnetic susceptibility measurements. The single crystal X-ray diffraction reveals that, both the copper(II) ions have distorted square pyramidal geometry with the coordination of the tridentate Schiff base ligand and the oxalate group. The copper(II) centres are separated by 5.4 A and antiferromagnetically coupled with a singlet–triplet separation of −12.4 cm −1 .

Synthesis and structural studies of selenocyanato-bridged polymeric and molecular complexes of cadmium(II): presence of both end-to-end and end-on coordination

Abstract Two new complexes, having one two-dimensional zig–zag polymeric network [Cd2(dmen)2(SeCN)4]n (1) and one molecular packing structure [Cd(dmen)2(SeCN)2] (2) (where dmen=N,N-dimethyl ethylenediamine), have been synthesised and characterised by infrared spectra and single crystal X-ray diffraction study. The different arrangements of selenocyanate anions result in two dimensional zig–zag polymeric sheet with the formation of two different rings, one having an eight-membered nearly hexagonal ring and another having a pseudo 16-membered ring for 1 and a molecular complex 2 with four independent molecules, having a total of 16 molecules per cell. The coordination environment in both the complexes is distorted octahedral. In the selenocyanato-bridged polymeric complex the cadmium(II) ions are linked by end-to-end coordination whereas in the molecular complex the cadmium(II) ions are bridged by end-on coordination only.

Synthesis and structural characterisation of a cyano-bridged trinuclear complex [(CuL)2Fe(CN)6][ClO4]·2CH3OH·H2O

The trinuclear complex [(CuL) 2 Fe(CN) 6 ][ClO 4 ]·2CH 3 OH·H 2 O [L= N , N ′-bis(2-pyridyl imine)propane-1,3-diamine] has been prepared and characterised by spectroscopic, elemental analysis, room temperature magnetic moment and single crystal X-ray analysis. Both copper(II) ions have a distorted square pyramidal geometry and are trans to each other, linked via cyanide bridges to the iron(III) centre. At the Cu(1) copper centre there is disorder between flattened chair and boat conformations in the saturated chelate ring. Of the six CN − groups around the octahedral iron(III) centre, four are terminal and the remaining two are coordinated to the [Cu(L)] 2+ moieties, giving nonlinear Fe–CN–Cu linkages.

A new cyanato-bridged polymeric complex [Cd3(NCO)6(NH2CH2C5H4N)3]n with a zig–zag ladder shaped structure

Abstract A new cyanato-bridged polymeric complex [Cd3(NCO)6(NH2CH2C5H4N)3]n has been synthesized and characterized by X-ray crystallography. There are three cadmium atoms, three chelated 2-(aminomethyl)pyridine and six end-on bridging cyanato groups in the asymmetric unit. Each Cd atom is bonded to one chelated C5H4NCH2NH2 base and four μ2-NCO groups in a distorted octahedral environment. Three such independent CdN6 octahedra share their bridging edges to produce a zig–zag ladder shaped polymeric network extending along a.