Unexpected Coordination Behaviour of 3,5-Di(2-pyridyl)-1,2,4-oxadiazole.

The coordination behaviour of 3,5-di(2-pyridyl)-1,2,4-oxadiazole ( L′) has been studied and compared with that of the 2,5-di(2-pyridyl)-1,3,4-chalcadiazoles LO, LS and LSe [ LO = 2,5-di(2-pyridyl)-1,3,4-oxadiazole, LS = 2,5-di(2-pyridyl)-1,3,4-thiadiazole, LSe = 2,5-di(2-pyridyl)-1,3,4-selenadiazole]. Ligand L′ and the new complexes [CuII( L′)3](ClO4)2 ·1.5MeOH ·H2O ( 1·1.5MeOH ·H2O), 1·MeCN, [CoII( L′)2(MeOH)2](ClO4)2 ( 2), [CoII( LO)2(MeOH)2](ClO4)2 ( 3), [CuII( L′)2Cl2] ( 4), [CuII( L′)2Br2] ( 5) and [CuII( LSe)2Cl2] ·MeOH ( 6·MeOH) have been structurally characterised by single-crystal X-ray diffraction analyses. With the help of DFT calculations and the analyses of metal-ligand bond lengths of similar complexes of L′, LO, LS and LSe the binding capacities have been determined as L′ << LO < LS < LSe. [ABSTRACT FROM AUTHOR]