Experimental Electron Density Analysis of the Reaction Steps Leading to Coordination of 1-Phenyl-1H-1,2,3-Triazole-4-Carboxylic Acid to Copper(II).

The coordination along a reaction sequence from a triazole precursor to a copper(II) complex was investigated with accurate electron density by means of high-resolution X-ray diffraction experiments and density functional theory calculations. The analysis of electron density distributions enables visualization of the electron polarization occurring upon the oxidation of the triazole alcohol and subsequently induced by coordination of the triazole carboxylic acid to the metal. This series of experimental measurements allows the direct visualization of the modified properties, with implications for molecular recognition and crystal engineering purposes.