Building hydrogen-bonded networks from metal complexes containing the heterotopic (N or O) ligand 4,4′-bipyridine-N-monoxide

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The heterotopic ligand 4,4′-bipyridine-N-monoxide (BIPYMO) has a rigid, linear structure and contains both a pyridine N-donor and a pyridine-N-oxide O-donor which are capable of coordinating to a metal centre or alternatively acting as a hydrogen bond acceptor. The hydrogen bonding capacity of BIPYMO is first demonstrated by the formation of hydrogen-bonded networks with water and some simple dicarboxylic acids (fumaric = FUM, terephthalic = TPA). It is then shown that BIPYMO can coordinate through the pyridine N-donor to Pd(II) and through the pyridine-N-oxide O-donor to Fe(II), Co(II) and Mn(II). In each case, the peripheral, uncoordinated N- or O-atoms act as a hydrogen bond acceptors and interact with a metal-bound and hydrogen bond donor (H2O, fumarate = FUM, malonate = MAL, isophthalate = IPA) to form a solid-state, network through a combination of metal–ligand coordination and hydrogen bonding. Single-crystal X-ray structures of {(BIPYMO)(H2O)2}n, {(BIPYMO)(FUM)}n, {(BIPYMO)(TPA)}n, {[Pd(BIPYMO)2(MAL)2](H2O)}n, {[Pd(BIPYMO)2(IPA)2](H2O)2}n and {[M(BIPYMO)2(FUM)2(H2O)2]}n (M = Mn, Fe, Co), show how the individual building blocks are organised via hydrogen bonding through uncoordinated pyridine N-atoms or pyridine-N-oxide O-atoms to form supramolecular networks.