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Micro properties such as ICT and ESIHT / ESIPT of bio-organic molecules require the theoretical study in addition to the experimental analysis. We adopted DFT / TDDFT along with PCM and EFP1 for the investigation of ground (S0) and excited (S1 )state properties of 2,2'-dihydroxychalcone (DH) and its water complex DH+(H2O)4- [DHH]. An intramolecular hydrogen bond exists between hydroxyl hydrogen and carbonyl oxygen in both DH and DHH molecules. Besides the intra-molecular hydrogen bond, in DHH four inter-molecular hydrogen bonds exist between DH and water molecules. The study of UV-Vis spectra both experimentally and theoretically reveals the S1 state is predominant in both the gas and solvent phase. The optimization of molecules in the S1 state resulted that the hydrogen atom transfuses from hydroxyl group to carbonyl group in DH molecule. The NBO analysis and potential energy scans confirm the hydrogen transfer at S1 state of DH molecule. The hydrogen transfer is not observed in the excited state of DHH molecule due to the effect of intermolecular hydrogen bond between water molecules and DH molecule.

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The exact eigenvalues and eigenfunctions of a spinless relativistic charged particle are obtained here. The results are compared with those from classical mechanics.

Excited state intramolecular hydrogen transfer (ESIHT) reaction of 8-formyl-7-hydroxy-4-methyl coumarin (FC) in its pure and hydrated state FC-(H2O)4 (FCH) has been studied by implementing state specific time dependent density functional theory (SS-TDDFT) along with the effective fragment potential (EFP1) method for solvation with discrete water molecules. The intramolecular hydrogen bond formed between hydroxyl hydrogen (H18) and formyl oxygen (O15) and intermolecular hydrogen bonds formed due to microsolvation were explored. The studies of electrostatic potential, natural charge analysis, difference electron density map and UV-Vis spectra of both FC and FCH molecules establish the intramolecular charge transfer (ICT) states of the molecules. The vertical excitation from S0 to S1 state causes the transfer of hydroxyl hydrogen to formyl oxygen and from S1 to S3 causes the transfer of the hydrogen atom back to hydroxyl oxygen. Potential energy surface scans along intramolecular hydrogen bonding at the ground and excited states confirm the state specific ESIHT reaction in both FC and FCH molecules.