Novel Supramolecular Isomerism in Coordination Polymer Synthesis from Unsymmetrical Bridging Ligands: Solvent Influence on the Ligand Placement Orientation and Final Network Structure

The assembly of Co(NCS) 2 with 1‐methyl‐1′‐(3‐pyridyl)‐2‐(4‐pyridyl)ethene ( L 1 ) exhibits a novel supramolecular isomerism of [Co( L 1 ) 2 (NCS) 2 ] ∞ caused by different placement orientation of L 1 around metal centers. The reaction in MeOH/H 2 O and EtOH/H 2 O resulted in a double chain structure of 1, and that in EtOH/CH 3 NO 2 led to an open framework structure of 2 . The reaction in MeOH/CH 3 NO 2 solvent system concomitantly afforded 1 and 2 . The assemblies of 1‐(3‐pyridyl)‐2‐(4‐pyrimidyl)ethene ( L 2 ) with Co(NCS) 2 created the water‐coordinated complexes of Co( L 2 ) 2 (H 2 O) 2 (NCS) 2 ( 3 and 4 ), an MeOH coordinated complex of Co( L 2 ) 2 (H 2 O) 2 (NCS) 2 ( 5 ), and an open framework coordination polymer of [Co( L 1 ) 2 (NCS) 2 ] ∞ ( 6 ) depending on the reaction solvent system. From these observations, it is suggested that in the formation of 1 , the solvent‐coordinated intermediate species would be generated first and its trans coordination configuration should define the placement orientation of L 1 in the resulting polymer of 1 . On the other hand, it is presumed that the solvent‐coordinated intermediate would not be produced during the formation of 2 due to the weaker coordination ability of EtOH and CH 3 NO 2 molecules. The open framework coordination polymers of 2 and 6 are converted in the solid state into the isomeric coordination polymer of 1 and hydrogen bonded network structure of 3 , respectively.