Aqueous microsolvation of HgClOH. A systematic MP2 study of the HgClOH–(H2O)n species with n = 1–4

We report a systematic study of aqueous microsolvation of HgClOH. The optimized structures, harmonic vibrational frequencies and binding energies of one to four water molecules coordinated with HgClOH have been computed with 2nd order Möller–Plesset perturbation theory. Accurate incremental water binding energies have been obtained at the complete basis set (CBS) limit using sequences of augmented correlation-consistent basis sets including the counterpoise correction. The main water-solute interactions arise from hydrogen bonding and hydrogen–halogen bonds. Although mercury establishes two direct orbital-driven interactions with water oxygens for n = 3 and n = 4, the intramolecular geometry of HgClOH is barely modified by the microsolvation environment. The CP-corrected MP2/CBS incremental binding energies are 5.20, 11.49, 6.63 and 10.00 kcal/mol for n = 1–4. The structural and vibrational analysis reveal that the strongest water-solute interaction appears for n = 3.