On the potential energy surfaces of dimers formed between trans-glyoxal, trans-acrolein and formaldehyde

Abstract

The potential energy surfaces of the six dimers formed between trans-glyoxal, trans-acrolein, and formaldehyde were investigated theoretically at the MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels. All in all thirty-five low-lying stationary points were detected. In five cases the global minimum of each dimer type has a non-planar structure. The acrolein dimer is the only case in which a planar arrangement prevails. Most dimers display geometry changes and vibrational frequency shifts characteristic for a formyl group engaged in hydrogen bonding or in more general intermolecular interactions: red shifts of CO stretches and blue shifts of CH stretches. The size of these shifts depends, however, strongly on the individual case.