Role of 4,4’-bipyridine versus longer spacers 4,4’- azobipyridine, 1,2-bis(4-pyridyl)ethylene, and 1,2- bis(pyridin-3-ylmethylene)hydrazine in the formation of thermally labile metallophosphate coordination polymers

摘要

One dimensional metallophosphate coordination polymers {[M(dtbp)2(azopy)(H2O)2]·(azopy)}x (M = Mn (1); Co (2); Cu (3); Cd (4)) have been synthesized from the reaction of a suitable metal precursor with di-tert-butylphosphate (dtbp-H) in the presence of ditopic linker 4,4’-azobipyridine (azopy) in a 1 : 2 : 2 stoichiometric ratio. Isostructural compounds 1-4 have been characterized by analytical and spectroscopic methods and single crystal X-ray diffraction studies. Single crystal X-ray diffraction measurements further reveal that compounds 1-3 (all C2/c) and 4 (P1) are linear 1D coordination polymers. The uncoordinated 4,4’-azobipyridine in the lattice is responsible for the conversion of these 1D coordination polymers into 3D supramolecular assemblies through O-H · · · N hydrogen bonding interactions between coordinated water and N-centers of an azopy ligand. Similar reactions carried out using 1,2-bis(4-pyridyl)- ethylene (bpe) as the linker yielded compounds having the formula {[M(dtbp)2(bpe)(H2O)2]·(bpe)}x (M = Mn (5); Co (6); Cu (7); Ni (8)). Compounds 5-8 have been characterized by analytical and spectroscopic methods. Preliminary single crystal X-ray diffraction studies carried out on poorly diffracting crystals of 5 and 6 establish their isostructural nature to 1-4, also displaying a similar supramolecular aggregation behaviour. A longer ditopic N,N’-donor ligand, 1,2-bis(pyridin-3-ylmethylene)hydrazine (bph), has been used in place of bpe/azoby to synthesize 1-dimensional coordination polymers [{M(bph)(H2O)4}{(dtbp)2}] (M = Ni (9) and M = Co (10)) and [Cd(bph)3(dtbp)2]n (11) which have completely different structural motifs when compared to 1-4.