Density functional theory study of red-shifted hydrogen bonds of 4-pyridinemethanol with water

The hydrogen bonds of 1 : 1 and 1 : 2 complexes formed between 4-pyridinemethanol and water have been investigated using a density functional theory (DFT) method and 6-311 + +G** basis set, and three and eight stable geometries have been obtained for 1 : 1 and 1 : 2 complexes, respectively. The interaction energy is -20.536 and -44.256 kJ/mol for the most stable 1 : 1 and 1 : 2 complexes, respectively, after the basis set superposition error and zero-point corrections. The formation of O-H center dot center dot center dot N(O) hydrogen bonds makes O-H symmetric stretching modes in the complexes red-shifted relative to those of the monomer. The natural bond orbit analysis indicates that the intermolecular charge transfer between 4-pyridinemethanol and water is 0.02642 e and 0.03813 e for the most stable 1 : 1 and 1 : 2 complexes, respectively. In addition, TD-B3LYP/6-311++ G** calculations show that formation of water-OH center dot center dot center dot N and water-OH center dot center dot center dot OH hydrogen bonds makes maximum absorbance wavelength lambda(max) blue-shifted 8-16 nm and red-shifted 4-11 nm compared to that of 4-pyridinemethanol monomer molecule, respectively.