Base Properties of H2CO in the Excited 1N->pi* State

DelBene, J. E., Gwaltney, S. R., & Bartlett, R. J. (1998). Base Properties of H2CO in the Excited 1N->pi* State. Journal of Physical Chemistry A. 102, 5124-5127.

CCSD and EOM-CCSD calculations with the aug‘-cc-pVDZ basis set have been carried out to investigate the structures, energies, and vibrational spectra of H2CO, protonated H2CO, and hydrogen-bonded HF:H2CO complexes in ground and excited 1n→π* states. The computed structures, vibrational spectra, and excitation energies of H2CO are in agreement with experimental data. In the 1n→π* state two protonated isomers, H2COH+ and H3CO+, exist. These differ in stability by 14 kcal/mol, with H2COH+ being more stable. The proton affinity of excited H2CO is 17 kcal/mol less than the ground-state proton affinity. Two hydrogen-bonded complexes HF:H2CO also exist in the excited 1n→π* state. The more stable complex has hydrogen bond formation occurring at the oxygen and is approximately 2 kcal/mol less stable than the corresponding ground-state complex. The complex with hydrogen bonding at the carbon is only a weakly bound, Born−Oppenheimer minimum.