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 intra-molecular 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 inter-molecular hydrogen bond between water molecules and DH molecule.