4,4‘-Dipyridyl-N,N‘-dioxide Complexes of Metal-Thiocyanate/Selenocyanate:  π-Stacked Molecular Rods as Three-Dimensional Support for Two-Dimensional Polymeric Sheets and Intra/Interchain S···S Interaction Dependent Architecture of the (8) Synthon Driven Assembly of One-Dimensional Polymeric Chains

Three supramolecular complexes of Co(II) using SCN - /SeCN - in combination with 4,4‘-dipyridyl- N, N ‘-dioxide (dpyo), i.e., {[Co(SCN) 2 (dpyo) 2 ]·(dpyo)} n ( 1 ), {[Co(SCN) 2 (dpyo)(H 2 O) 2 ]·(H 2 O)} n ( 2 ), {[Co(SeCN) 2 (dpyo)(H 2 O) 2 ]·(H 2 O)} n ( 3 ), have been synthesized and characterized by single-crystal X-ray analysis. Complex 1 is a rare example of a dpyo bridged two-dimensional (2D) coordination polymer, and π-stacked dpyo supramolecular rods are generated by the lattice dpyo, passing through the rhombic grid of stacked layers, resulting in a three-dimensional (3D) superstructure. Complexes 2 and 3 are isomorphous one-dimensional (1D) coordination polymers [-Co-dpyo-Co-] that undergo self-assembly leading to a bilayer architecture derived through an (8) H-bonding synthon between coordinated water and dpyo oxygen. A reinvestigation of coordination polymers [Mn(SCN) 2 (dpyo)(H 2 O)(MeOH)] n ( 4 ) and {[Fe(SCN) 2 (dpyo)(H 2 O) 2 ]·(H 2 O)} n ( 5 ) reported recently by our group [Manna et al. Indian J. Chem. 2006, 45A, 1813] reveals brick wall topology rather than bilayer architecture is due to the decisive role of S···S/Se···Se interactions in determining the helical nature in 4 and 5 as compared to zigzag polymeric chains in 2 and 3, although the same (8) synthon is responsible for supramolecular assembly in these complexes.