Exploring conformationally flexible hydrogen-bond-functionalized ligand and counter anions in metal-organic frameworks of Cu(II)

Single crystal structures of six metal-organic frameworks (MOFs) derived from N,N'-bis(3-pyridyl) urea L1 and Cu(II) salts having different counter ions have been investigated to study the plausible role of conformationally flexible hydrogen-bond-functionalized ligand L1 and counter ions on the resultant topologies of the MOFs. The ligand adopts the energetically least stable syn-syn conformation in most of the MOFs. The 1 : 2 metal-ligand coordination polymers display looped chain topologies with square-pyramidal metal center whereas 1 : 1 metal-ligand coordination polymers show 1D zigzag infinite chain. Although the urea functionality of the ligand does recognize the anions via various N-H center dot center dot center dot O/F interactions, the counter anions do not influence the primary framework structures.