SOLVATION OF CHROMONE USING COMBINED DISCRETE SCRF MODELS

The solvation of chromone has been investigated using three different combined Discrete/SCRF models. Four chromone-H2O complexes and one chr omone-4H(2)O complex were obtained from geometry optimizations at the HF/6-31G(d) lever. Three SCRF methods (PCM/6-31G(d), PCM/AM1 and SM2/A M1) were applied to such complexes in order to: (1) evaluate the relia bility of the combined Discrete/SCRF models; (2) investigate the effec ts of the explicit water molecules on the free energy of solvation; an d (3) analyze the characteristics of the different solvation sites of chromone. The results show that explicit solvent molecules exert a lar ge influence on the free energy of solvation of a given molecular syst em providing some information about the solvation sites. Thus, the int eraction of the carbonyl oxygen of chromone with the explicit water mo lecules is stronger than interaction provided by the ether oxygen, pro viding the complexes with the former interaction a more hydrophobic fr ee energy of solvation than those with the latter. On the other hand, the comparison of the free energies of solvation for solutes with expl icit water molecules in the first hydration shell and the free energie s of solvation of the molecular system computed in an all-continuum ap proach reveals that the combined Discrete/SCRF models constitute a ver y reasonable strategy. (C) 1998 Elsevier Science B.V. All rights reser ved.