Role of ligand conformation in the structural diversity of copper(II) and silver(I) coordination polymers containing the angular dipyridyl ligand bearing amide spacer

The new dipyridyl ligands N,N'-(methylenedi-p-phenylene)bis(pyridine-4-carboxamide), L1, and N,PP(methylenedi-p-phenylene)bis(pyridine-3-carboxamide), 12, incorporating amide spacers have been synthesized and reacted with metal salts to give complexes of the types [Cu(L1)(2)X-2](infinity)(X = Cl, 1 and X = Br, 2), ([Cu(L1)(2)(DMF)](NO3)(2)}(infinity), 3, ([Ag-2(L1)(2)](SO4))(infinity), 4, and {[Cu(L2)(DMSO)(2)(NO3)](NO3)}(infinity). All compounds have been characterized by spectroscopic methods and their structures determined by X-ray crystallography. Complexes 1, 2 and 3 form 1-D double-stranded polymeric chains showing rhombic molecular squares with approximate dimensions of 16.95 x 19.13 angstrom(2) for 1, 17.03 x 19.06 angstrom(2) for 2 and 16.66 x 19.94 angstrom(2) for 3. Complex 4 forms infinite 1-D zigzag polymeric chains, which are interlinked through a series of Ag-O interactions to form wavy 1-D ladder like chains, and complex 5 forms I-D sinusoidal chains. While the L1 ligands in complexes 1, 2 and 3 adopt the cis conformation and that in complex 4 adopts trans conformation, the L2 ligand in complex 5 adopts the trans-anti conformation. The ligand conformations also differ in the dihedral angles between the pyridyl and ppenyl rings. All complexes exhibit emissions which may be tentatively assigned as intraligand (IL) pi --> pi* transition. (C) 2008 Elsevier Ltd. All rights reserved.