Solvent-Driven Structural Diversities in Zn^II 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(μ-3bpmu)­Cl₂}] (<b>CP1</b>), [{Zn­(μ-3bpmu)­Cl₂}·benzene] (<b>CP2</b>), [{Zn­(μ-3bpmu)­Cl₂}·<i>p</i>-xylene] (<b>CP3</b>), and [{Zn­(μ-4bpmu)­Cl₂}·<i>p</i>-xylene] (<b>CP4</b>) are coordination polymers, whereas [{Zn₂(μ-3bpu)₂Cl₄}·<i>p</i>-xylene] (<b>CC1</b>) and [{Zn₂(μ-3bpu)₂Cl₄}·benzene] (<b>CC2</b>) 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 (<b>CP2</b>–<b>CP4</b>, <b>CC1</b>, and <b>CC2</b>), crystallization using only polar solvents produced crystals devoid of guests. Aromatic solvents appear to have induced the formation of metallamacrocycle in <b>CC1</b> and <b>CC2