Microhydration of 2-Naphthol at Ground, First Excited Triplet, and First Excited Singlet States: A Case Study on Photo Acids.

Molecular interactions of 2-naphthol (nap) with water molecules are studied at the ground, first excited triplet and first excited singlet states, applying DFT and TD-DFT methods. The minimum energy structure of hydrated clusters of 2-naphthol up to four water molecules are selected from several possible input geometries. It is observed that the minimum energy conformer of the tetra-hydrate of 2-naphthol has proton transfer occurring from nap to solvent water molecules, in its first excited singlet state.

Microhydration of Neutral and Charged Acetic Acid.

A systematic theoretical study has been carried out on the effect of sequential addition of water molecules to neutral and mono positively charged acetic acid molecules by applying first principle based electronic structure theory. Geometry, dipole moment, and polarizability of hydrated clusters of neutral and mono positively charged acetic acid of the type CHCOOH·nHO (n = 1-8) and [CHCOOH·nHO] (n = 1, 2) are calculated at the ωB97X-D/aug-cc-pVDZ level of theory. Free energies of formation of the hydrated acid clusters, at different temperatures and pressures are determined.

Supramolecularly Assisted Modulation of Optical Properties of BODIPY-Benzimidazole Conjugates.

Supramolecular host-guest interaction of neutral and cationic (protonated) forms of two boron-dipyromethane (BODIPY)-benzimidazole (mono- and di-benzimidazole) conjugate dyes with the macrocyclic host cucurbit[7]uril (CB7) has been investigated using photophysical and density functional theory studies. Expectedly, cationic forms of the dyes show exceptionally stronger binding than that of the neutral forms with CB7, which can be ascribed to the strong ion-dipole interaction between the positive charge of the dye and the highly polarizable carbonyl portals of the host. The formation of dye-host inclusion complexes is supported by the significant changes in the photophysical properties and longer rotational relaxation times of the dye in the presence of CB7.

Effect of microhydration on dissociation of trifluoroacetic acid.

First-principle-based electronic structure calculations were carried out on microhydrated trifluoroacetic acid clusters (CF3COOH, tfa) to understand its molecular level interaction with water and subsequent ionic dissociation to form CF3COO(-) ion. From several geometrical inputs, the global minimum energy structure of hydrated cluster, tfa · nH2O (n = 1-7), was obtained adopting dispersion-corrected density functional, namely, ωB97X-D, and a set of correlated atomic basis function, aug-cc-pVDZ. It was predicted that tfa requires at least six H2O molecules to dissociate.