Water square (uudd) in novel CuII framework structures built from isomeric (aminomethyl)pyridines and oxalate: Synthesis, structure, spectral and DFT studies

A perfect water square in uudd configuration, built from solvent waters has been isolated from a hybrid metal-organic host [Cu(3-aminomethyl)pyridine oxalateOH2·2H2O]n under self assembly conditions, stabilizing the supramolecular framework through cooperative hydrogen bonding interactions, a rare occurrence among water clusters. We report the synthesis, single crystal structure and spectral (IR & UV) studies for the supramolecular systems, viz., [Cu(2-aminomethyl)pyridine oxalateH2O]n (1) and [Cu(3-aminomethyl)pyridine oxalateOH2·2H2O]n (2) along with DFT & TD-DFT calculations using Gaussian-03 program for understanding the geometry and analysis of spectral results. As small water clusters are particularly significant in unraveling the mysteries of solid state water, the present example adds to the library of water tetramer formation and their hydrogen bonding ability under restricted environments.