Template synthesis of 1-(8 '-amino-alpha-naphthyl)-4-(8 '-amino-alpha-naphthylamine)-1-azabuta-1,3-diene, a tetraaza half-cyclised ligand, and characterisation of its copper(II) complexes.
INDIAN J CHEM A
400 - 406.
Reaction of 1,1,3,3-tetramethoxypropane with 1,8-diaminonaphthalene in presence of a nickel(II) template in aqueous medium generates the free acyclic ligand 1-(8'-amino-alpha -naphthyl)-4-(8'-amino-alpha -naphthylamine)-1-azabuta-1,3-diene (LH; H: dissociable proton) as a 1.5 hydrate. The ligand undergoes acid dissociation in non-aqueous solvents which is reflected in its C-13 NMR spectrum in deuteriated dimethyl sulphoxide (DMSO). Its pK(a) value determined in DMSO from conductivity data is 5.18. With copper(II) perchlorate, LH forms. air sensitive complexes of type CuL(ClO4). 3H(2)O and CuL(ClO4). DMF (DMF: dimethylformamide). In both the complexes, the perchlorate anion is weakly bound to the metal as revealed by their conductivity in DMF suggesting a CuN4O2+ chromophore. Their EPR spectra in DMF-toluene glass at 77 K are almost identical and have rhombic features (<g(3)>, 2.40; <g(2)>, 2.08; <g(1)>, 2.01; <A(3)>, 137x10(-4) cm(-1); <A(2)>, 18x10(-4) cm(-1)) indicating that the coordination sphere around the copper ion is of distorted square-pyramidal type. ZINDO calculations show that the CuL+ fragment has a butterfly like shape with the naphthalene fragments spanning like two wings and the metal in the N-4 plane. In cyclic voltammetric experiments in DMF at a platinum electrode, the complexes show a quasireversible two-electron ligand oxidation with an E-1/2 of 0.12 V vs saturated calomel electrode (SCE) and an irreversible metal oxidation process at a low potential (< 0.5 V vs SCE).
|Title:||Template synthesis of 1-(8 '-amino-alpha-naphthyl)-4-(8 '-amino-alpha-naphthylamine)-1-azabuta-1,3-diene, a tetraaza half-cyclised ligand, and characterisation of its copper(II) complexes|
|Open access status:||An open access publication|
|Keywords:||MACROCYCLIC COMPLEXES, METAL, REACTIVITY, CHEMISTRY|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
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