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

The reaction of metal ions, flexible aliphatic dicarboxylates and pyrazine in aqueous solution afford two new metal-organic coordination 2 polymers, {[Cu2(mu(2)-eta(2)-O2C(CH2)(2)CO2-eta(2)-mu(2))(2)(H2O)(2)]center dot 2H(2)O}(n) (1) and [Eu-2(mu(2)-eta(2)-O2CCH2CO2-eta(1)-mu(1))(2)(mu(2)-eta(2)- O2CCH2CO2-eta(2)-mu(2))(H2O)(6)](n) (2). Polymer 1 contains the paddle-wheel cage dicopper(II) units, forming a one-dimensional (ID) 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) angstrom; the interdirner Cu center dot center dot center dot Cu distance is 6.473 angstrom. To our knowledge, compound I 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 [EuO6(H2O)(3)](n) units as tethers, resulting in microporous framework. The magnetic behavior of I 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 -2J = 314 cm(-1). (c) 2006 Elsevier Ltd. All rights reserved.