Macrocyclic metal complexes: Part XX-Studies on nickel(II) macrocyclic complexes with cyclic ligands [Ph₄[13]tetraene N₄(N₂)], [Ph₄ [14]tetraene N₄(N₂)], [MePh4[13)tetraene N₄(N₂)] and [Ph₄bzo[13]pentacne N₄(N₂)]

Abstract

A series of macrocyclic complexes of nickel(II) has been synthesised by the action of formaldehyde on {bis(benzilmonohydrazone)diimine} nickel(II) complexes. The macrocycles and the precursors have the spin singlet ground state, are square planar in structure and show one ligand field band near 19,000 cm^-1. The complexes show one electron reduction in two discrete steps with <i>E </i><img src='http://www.niscair.res.in/jinfo/equation58.gif' border=0> values in the ranges - 0.33 to - 0.55 V and - 1.53 V to -1.63 V respectively. The ∆<i>E </i>_1/2 values have been examined thermodynamically for each macrocycle and the precursor, and ∆<i>E </i><img src='http://www.niscair.res.in/jinfo/equation59.gif' border=0> values between the macrocyc1e (Cy') and its corresponding precursor (L). The analysis suggests formation of ligand anion radical in the first step and a reduced metal-ligand anion radical complex in the second step.