Coordinating and hydrogen bonding ability of a bifunctional 2D paddle-wheel copper(II) coordination polymer

A new copper(II) complex of formula {[Cu2(H2btc)2(dmf)2]·4dmf}n (1) [H4btc = 1,2,4,5-benzenetetracarboxylic acid, dmf = dimethylformamide] has been synthesised and its structure determined by X-ray diffraction. The structure displays a new square grid of “paddle-wheel” tetracarboxylate-bridged dicopper(II) units with an intradimer copper–copper separation of 2.619(2) Å. The dmf molecules are retained through weak axial coordinative bonds and hydrogen bonding interactions with the carboxylic groups of the porous neutral network of 44 net topology. The magnetic behaviour of 1 corresponds to a strong antiferromagnetic coupling within each dicopper(II) unit (J = −343 cm−1 with the Hamiltonian being defined by H = −JS1·S2). Complex 1 does not adsorb N2 but it exhibits certain absorption of CO2 with a hysteretic desorption behaviour typical of flexible MOFs.

A novel 2D copper(II) bifunctional MOF has been prepared from the assembly of strong antiferromagnetically coupled, paddle-wheel dicopper(II) building blocks with doubly protonated H2btc2− ligands. The presence of pore spaces with both open metal sites and hydrogen-donor carboxylic groups offers possibilities in host–guest chemistry.Figure optionsDownload as PowerPoint slide