Novel self-assembled supramolecular architectures of Mn(ii) ions with a hybrid pyrazine-bipyridine ligand

Abstract

A new hybrid pyrazine-bipyridine ligand L (C 26 H 20 N 6) and its complexes with Mn(NO 3) 2, Mn(ClO 4) 2, MnCl 2 and MnBr 2 have been synthesised. By the self-assembly of L and Mn(ii) ions three different kinds of supramolecular complexes have been obtained: binuclear baguette complex [Mn 2 L(H 2 O) 6 ](NO 3) 4 ·2.5H 2 O 1 and tetranuclear [2 × 2] grid-type complex [Mn 4 L 4 ](ClO 4) 8 ·2.5(CH 3 CN)·2CH 3 OH 2 and mononuclear complexes [MnL 2 ]X 2 (where X = Cl - 3 and X = Br - 4). Crystal structures and magnetic properties of Mn(ii) complexes 1 and 2 have been also investigated. The crystal structures reveal that in both 1 and 2 complexes the Mn(ii) ions have coordination number 6 and distorted octahedral coordination geometry. In 2 four metal cations and four ligands have assembled into a grid-type [2 × 2] array, with a perchlorate anion occupying the central cavity, with clearly a good fit for the center of the cavity. The perchlorate anion, in contrast to the nitrate anion, probably acts as a template in the formation of tetranuclear grid-type complexes. Magnetic susceptibility measurements indicate that the Mn(ii) ions are all high spin, and in both 1 and 2 complexes there are weak antiferromagnetic interactions between Mn(ii) ions. © The Royal Society of Chemistry 2013.