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)(H₂O)₂]·(H₂O)}_n (2), {[Co(SeCN)₂(dpyo)(H₂O)₂]·(H₂O)}_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)(H₂O)(MeOH)]_n (4) and {[Fe(SCN)₂(dpyo)(H₂O)₂]·(H₂O)}_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.