Density functional theory (DFT) and natural bond orbital (NBO) investigation of intramolecular hydrogen bond interaction and excited-state intramolecular proton transfer (ESIPT) reaction in a five-membered hydrogen-bonding system 2-(1H-pyrazol-5-yl)pyridine: On the possibility of solvent (water)-assisted ESPT

摘要: Abstract The present work aims at exploring the excited-state intramolecular proton transfer (ESIPT) reaction in a five-member hydrogen bonding ring system, viz., 2-(1 H -pyrazol-5-yl)pyridine (2Pz–5Py), which ESIPT process is found to be associated with an appreciably large barrier, on lexicon of Density Functional Theory (DFT)-based computational approach. Nevertheless feasibility has been argued from changeover relative stability patterns enol (E) and proton-transferred (PT) forms photoexcitation S 0 -PES 1 -PES. Critical evaluation modulations geometrical parameters other than PT coordinate also undertaken. (I ra MHB) interaction 2Pz–5Py explored by calculation hyperconjugative charge lone electron pair nitrogen atom σ ∗ orbital N–H bond, under provision Natural Bond Orbital (NBO) analysis. Further, we have endeavoured cast light important issue water-mediated ESPT 2Pz–5Py. Apart examining impact water mediacy barrier for process, substantial influence solvent (water) field energetic geometric aspects molecule are through calculations based polarizable continuum model (PCM). Again applicability NBO analysis extended characterize nature strength IMHB hydrated cluster directional unveiled this juncture.