Solvent-Driven Structural Diversities in ZnII Coordination Polymers and Complexes Derived from Bis-pyridyl Ligands Equipped with a Hydrogen-Bond-Capable Urea Backbone

A new series Zn-II metal-organic compounds [both coordination complexes (CCs) and coordination polymers (CPs)] derived from bis-pyridyl ligands equipped with hydrogen-bonding functionality such as urea have been synthesized and characterized by single crystal X-ray crystallography. Out of the six compounds reported herein, [{Zn(mu-3bpmu)Cl-2}] (CP1), [{Zn(mu-3bpmu)Cl-2}center dot benzene] (CP2), [{Zn(mu-3bpmu)C12}center dot p-xylene] (CP3), and [(Zn(mu-4bpmu)Cl-2}center dot p-xylene] (CP4) are coordination polymers, whereas [{Zn-2(mu-3bpu)(2)Cl-4}center dot p-xylene] (CC1) and [{Zn-2(mu-3bpu)(2)Cl-4}center dot benzene] (CC2) are coordination complexes. The solvent of crystallization has profound effect on the supramolecular architecture of the resultant coordination compounds; while crystallization in the presence of aromatic solvents resulted in guest occluded crystals (CP2-CP4, CC1, and CC2), crystallization using only polar solvents produced crystals devoid of guests. Aromatic solvents appear to have induced the formation of metallamacrocycle in CC1 and CC2.