title: Spectroscopic studies, cyclic voltammetry and synthesis of nickel(II) complexes with N(4), N(2)O(2) and N(4)S(2) donor macrocyclic ligands.
abstract: Nickel(II) complexes of the general composition Ni(L)X(2) (where X=SCN, NO(3) and 1/2SO(4) and ligands=L(1) L(2) and L(3)) have been synthesized and characterized by elemental analyses, magnetic moments, IR, (1)H NMR, (13)C NMR and electronic spectral studies. Nickel(II) ions, such as nitrates, thiocyantes and sulphates were found to act as templates for the cyclic condensations [1+1] and [2+2] of NH(2--)C(6)H(4)--O--CH(2)--CH(2)--O--C(6)H(4)--NH(2), NH(2)--(CH(2))(2)--NH(2) and NH(2)--CH(CH(3))--CH(2)--NH(2) with C(6)H(5)--CO--CO--C(6)H(5), C(6)H(5)--CO--CH(2)--CO--C(6)H(5) and (COOH--CH(2)--CH(2))(2)S. All the complexes show magnetic moments corresponding to two unpaired electrons except [Ni(L(1))](NO(3))(2) and [Ni(L(2))](NO(3))(2) complexes which are diamagnetic. Electronic spectroscopy was used to analyse the differences between the paramagnetic and diamagnetic forms. Electrochemical properties have been studied extensively for Ni(III/II) and Ni(II/I) couples. The equilibrium between the paramagnetic and diamagnetic forms and the nickel(III/II) couple are strongly dependent on the electrolyte. It has been observed that the sulphate group coordinated selectively on the apical position of the nickel(II) centers of the compounds. The structural and electrochemical studies suggest that cooperative effects, involving coordination of sulphate to one nickel center, is responsible for the recognition of this anion. Various ligand field parameters have been calculated and discussed.
authors.affiliation: Department of Chemistry, Zakir Husain College, University of Delhi, Jawahar Lal Nehru Marg, New Delhi 110002, India. schandra_00@yahoo.com
authors.forename: Sulekh
authors.initials: S
authors.lastname: Chandra
authors.forename: Rajiv
authors.initials: R
authors.lastname: Kumar
mesh_terms: D004563:Electrochemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006575:Heterocyclic Compounds, 3-Ring / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D017672:Nitrogen Compounds / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013457:Sulfur Compounds / Q000737:chemistry*
chemical_list: C510112:2,3-diphenyl-1,4-diaza-7,10-dioxa-5,6-11,12-dibenzocyclododeca-1,3-diene; C510113:8,17-dimethyl-1,7,10,16-tetraaza-4,13-dithiacyclooctadeca-2,6,11,15-tetraone; D006573:Heterocyclic Compounds, 1-Ring; D006575:Heterocyclic Compounds, 3-Ring; D008024:Ligands; D017672:Nitrogen Compounds; D009589:Nitrogen Oxides; D013457:Sulfur Compounds; D009532:Nickel; D009584:Nitrogen