Self-assembly of a Mixed-valence Cu(I)/Cu(II) Coordination Polymer Derived from a Conformationally Flexible Tripodal Phosphoric Trimide Ligand

Reaction of a tripodal ligand, N, N', N ''-tris(3-pyridinyl) phosphoric trimide (TPPA) and CuBr2 center dot 2H(2)O result in the assembly of a new polymeric copper coordination polymer, which was characterized by single-crystal diffraction, infrared spectroscopy and elemental analysis. The polymer crystallizes in the triclinic system, space group P (1) over bar with a = 9.0964(5), b = 10.2592, c = 10.5822(8) angstrom, V = 933.01(9) angstrom(3), Z = 2, C30H24Br4Cu3N12O2P2, M-r = 985.02, D-c = 1.753 g/cm(3), F(000) = 4072 and mu(MoK alpha) = 0.746 mm(-1). The final R and wR are 0.0588 and 0.1329 for 4260 observed reflections with I > 2 sigma(I). Cu(I) is tetrahedrally coordinated and Cu(II) center adopts square planar coordination geometry. Because of the flexibility of the TPPA ligands, the pyridyl rings rotate though a certain angle and three pyridyl rings on the same TPPA rotate by about 45 degrees with respect to the central P=O groups. TPPA ligand acts as a tridentate ligand and is coordinated with three metal centers with its pyridyl donors to form a 2D-sheet like structure, and it is further connected by N-H center dot center dot center dot O and N-H center dot center dot center dot Br, resulting in a 3D network packing. Oxidation states of the metal center have been determined by bond valence sum calculation.