A non-homoleptic Cu-9 [3 x 3] mixed ligand grid - structural and magnetic properties

摘要

The tritopic hydrazide ligand m2poap (from the reaction of 4-methoxy-2,6-dicarboxylic hydrazide and methyl imino-2-picolinate) reacted with Cu(NO3)(2) to produce a linear trinuclear diazine (N-N) bridged m2poap complex, and a nona-nuclear Cu(II)(9) mixed ligand [3 x 3] grid complex, containing two 4-chloro-2,6-pyridine dicarboxylate (Clpic(2-)) ligands, and four deprotonated m2poap ligands. The presence of Clpic(2-) arises from an impurity in the ligand, which results from hydrolysis of a starting material. Clpic(2-) connects three Cu(II) centers in an unusual oxygen bridged coordination mode. The smaller bite of this ligand leads to a contraction of the grid, compared with homoleptic [3 x 3] grid examples, and results in enhanced ferromagnetic exchange within the grid. The trinuclear complex of m2poap exhibits fairly strong antiferromagentic exchange, typical of N-N bridged systems. (C) 2002 Published by Elsevier Science Ltd. [References: 21]