Related Experiment Video
Updated: Jun 10, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Excited-state intramolecular proton transfer (ESIPT) fine tuned by quinoline-pyrazole isomerism: pi-conjugation
Min-Wen Chung1, Tsung-Yi Lin, Cheng-Chih Hsieh
1Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
Abstract:
A series of quinoline/isoquinoline-pyrazole isomers (I-III), in which the pyrazole moiety is in a different substitution position, was strategically designed and synthesized, showing a system with five-membered intramolecular hydrogen bonding. Despite the similarity in molecular structure, however, only I undergoes excited-state intramolecular proton transfer, as evidenced by the distinct 560 nm proton-transfer emission and its associated relaxation dynamics. The experimental results support a recent theoretical approach regarding the conjugation effect on a proton (or hydrogen atom) transfer reaction (J. Phys. Chem. A 2009, 113, 4862-4867). The concept simply predicts that more extended pi conjugation, i.e., resonance, for proton-transfer tautomer species could allow for efficient delocalization of excess charge in the reaction center, resulting in a larger thermodynamic driving force for proton transfer.
More Related Videos
10:03Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
12:19Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
Related Concept Videos
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
π Electron Effects on Chemical Shift: Overview