Syntheses of two new hybrid metal-organic polymers using flexible aliphatic dicarboxylates and pyrazine: Crystal structures and magnetic studies

Abstract

The reaction of metal ions, flexible aliphatic dicarboxylates and pyrazine in aqueous solution afford two new metal-organic coordination polymers, {[Cu 2( μ 2- η 2-O 2C(CH 2) 2CO 2- η 2- μ 2) 2(H 2O) 2]·2H 2O} n ( 1) and [Eu 2( μ 2- η 2-O 2CCH 2CO 2- η 1- μ 1) 2( μ 2- η 2-O 2CCH 2CO 2- η 2- μ 2)(H 2O) 6] n ( 2). Polymer 1 contains the paddle-wheel cage dicopper(II) units, forming a one-dimensional (1D) double-stranded chain structure along the a-axis, in which the copper(II) atoms are bridged by the carboxylate groups of four succinates. The intradimer Cu–Cu distance is 2.613(2) Å; the interdimer Cu⋯Cu distance is 6.473 Å. To our knowledge, compound 1 represents the first example of a double-stranded chain structure containing dinuclear paddle-wheel type cage. In the three-dimensional (3D) compound 2, each central Eu(III) ion have a distorted monocapped square antiprism coordination geometry. The structure is built up from two types of polymeric chains with [EuO 6(H 2O) 3] n units as tethers, resulting in microporous framework. The magnetic behavior of 1 shows that the occurrence of a strong antiferromagnetic coupling between the copper(II) ions through the short bridges via the carboxyl groups can be obtained; the best fittings to the experimental magnetic susceptibilities gave −2 J=314 cm −1.