TD-DFT study on the cyanide-chemosensing mechanism of 8-formyl-7-hydroxycoumarin

• Published in: Journal of computational chemistry Vol. 32; no. 4; pp. 668 - 674
• Main Authors: Li, Guang-Yue, Zhao, Guang-Jiu, Han, Ke-Li, He, Guo-Zhong
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.03.2011; Wiley Subscription Services, Inc
• Subjects: cyanide; Cyanides - analysis; Environmental Pollutants - analysis; excited-state proton transfer; Fluorescence; fluorescent chemosensor; Fluorescent Dyes - chemistry; hydrogen bond; Hydrogen Bonding; Hydrogen bonds; Models, Molecular; Molecules; proton transfer; Protons; Quantum Theory; time-dependent density functional theory; Umbelliferones - chemistry
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.21651

Proton transfer (PT) and excited-state PT process are proposed to account for the fluorescent sensing mechanism of a cyanide chemosensor, 8-formyl-7-hydroxycoumarin. The time-dependent density functional theory method has been applied to investigate the ground and the first singlet excited electronic states of this chemosensor as well as its nucleophilic addition product with cyanide, with a view to monitoring their geometries and spectrophotometrical properties. The present theoretical study indicates that phenol proton of the chemosensor transfers to the formyl group along the intramolecular hydrogen bond in the first singlet excited state. Correspondingly, the nucleophilic addition product undergoes a PT process in the ground state, and shows a similar structure in the first singlet excited state. This could explain the observed strong fluorescence upon the addition of the cyanide anion in the relevant fluorescent sensing mechanism.