Interplay of bipyridine and 4,4′-diaminodiphenylmethane ligands in crystal design of cadmium-based coordination polymers: Structures and unusual photoluminescence quenching

Starting from Cd(ClO4)(2)& sdot;2H(2)O, four positively charged coordination polymers were prepared and characterized by IR spectroscopic and single-crystal X-ray diffraction methods. The obtained crystalline solids included one- dimensional coordination polymers, {[Cd(dadpm)(2,2 '-bpy)2](ClO4)2}n (1), and {[Cd(dadpm)(2,2 '-bpy)2] (ClO4)(2 & sdot;0.5)(H2O)}n (2), and two-dimensional coordination polymers, {[Cd(4,4 '-bpy)(2)(H2O)(2)](ClO4)(2)(dadpm)(2)}(n) (3), and {[Cd(4,4 '-bpy)2(H2O)(2)](ClO4)2(4,4 '-bpy)(0.5)(dadpm)& sdot;EtOH}n (4) (dadpm =4,4 '-diaminodiphenyl-methane, 2,2 '-bpy =2,2 '-bipyridine; 4,4 '-bpy =4,4 '-bipyridine). The similar one-dimensional coordination backbones in 1 and 2 were originated from the mononuclear Cd(II) coordination cores with the N6 distorted octahedral geometries going from two terminal bidentate-chelate 2,2 '-bpy and two bidentate-bridging dadpm ligands that mediated the successive metal atoms in coordination chains. The charge-balanced perchlorate anions were located in the interchain space complemented by water molecules in 2. The coordination chains were interconnected into H-bonded networks via NH(NH2)& ctdot;O hydrogen bonds. The 2D coordination polymers 3 and 4 comprised the same positively charged square-grid infinite networks {[Cd(4,4 '-bpy)2(H2O)2](2+)}n with sql to-pology and with cadmium atom in the N4O2 tetragonally distorted octahedral coordination geometry as a single node. The charge-compensated ClO(4)anions and the dadpm molecules were located in the interlayer space in 3 being complemented by the 4,4 '-bpy and EtOH molecules in 4. The solid-state photoluminescence in all reported coordination polymers was significantly attenuated and redistributed along the spectrum in comparison with the pure dadpm which revealed the dual emission in the form of a strong narrow signal in the ultraviolet and a weak signal in the yellow regions of spectrum.