Photoreduction of 3-Phenylquinoxalin-2-ones by Amines:  Transient-Absorption and Semiempirical Quantum-Chemical Studies

Abstract

Photoreduction of 3-phenylquinoxalin-2-ones, XNQ, by triethylamine, TEA, gives a metastable semireduced quinoxalin-2-one via an electron-proton-electron transfer, with unit quantum yields at high amine concentrations. During the photoreduction, an ion-radical pair, XNQ -• /TEA +• , a neutral-radical pair, XNQH • / TEA-H • , and an ion-pair, XNQH -/TEA-H + , are formed. We present time-resolved spectroscopic data and quantum mechanical semiempirical AM1, PM3, and ZINDO/S results for the transient species formed during the flash photolysis of quinoxalin-2-ones in the presence of amines. These calculations show that the neutralradical pair and the ion-pair are similar in energy, and that the calculated spectra of all the transient species should have similar absorption bands near 400 nm in agreement with experimental results. The ZINDO/S calculated spectra of the XNQH -/iminium ion pair fit the experimental spectra and explain the lack of visible or near-IR absorption of the metastable compound. Energy changes between the species involved are of interest with regard to the possible use of quinoxalin-2-one/amine systems for light to chemical energy conversion or as temporal data storage devices.

Radiation-induced reduction of quinoxalin-2-one derivatives in aqueous solutions

“…Spectral and kinetic characteristics of the intermediate species: triplet ion-radical pairs (Q  /amine  ) and hydrogenated neutral radicals (QH  ) have been obtained by laser flash photolysis (De la Fuente et al, 2002). Calculated spectra using quantum mechanical semiempirical AM1, PM3, and ZINDO/S approach were found to be in agreement with the experimental spectra (De la Fuente et al, 2002).…”

“…The photophysical and photochemical behavior of 1-methyl-3-phenyl-quinoxalin-2-one and 3-phenyl-quinoxalin-2-one in the presence of amines has been reported in some selected organic solvents (acetonitrile, methanol and hexane) (De la Fuente et al, 2002;De la Fuente et al, 2000). Spectral and kinetic characteristics of the intermediate species: triplet ion-radical pairs (Q  /amine  ) and hydrogenated neutral radicals (QH  ) have been obtained by laser flash photolysis (De la Fuente et al, 2002).…”

“…Spectral and kinetic characteristics of the intermediate species: triplet ion-radical pairs (Q  /amine  ) and hydrogenated neutral radicals (QH  ) have been obtained by laser flash photolysis (De la Fuente et al, 2002). Calculated spectra using quantum mechanical semiempirical AM1, PM3, and ZINDO/S approach were found to be in agreement with the experimental spectra (De la Fuente et al, 2002). Recently, the stable products resulting from the photoreduction of six 7-substituted-3-methyl-quinoxalin-2(1H)-one derivatives The electrochemical studies of three 3-methyl-quinoxalin-2(1H)-ones: 3-methylquinoxalin-2(1H)-one, 3,6,7-trimethylquinoxalin-2(1H)-one and 7-amino-3-methylquinoxalin-2(1H)-one showed that the pyrazine ring is the electroactive center undergoing two-electron reduction (Zimpl et al, 2012).…”

Photoreduction of Oxoisoaporphine Dyes by Amines: Transient-Absorption and Semiempirical Quantum-Chemical Studies

“…Semiempirical quantum mechanical calculations have been used successfully for electronic spectral prediction of neutral molecules, cation-radicals and dications of carotenoids, 19 butadiene derivatives, 20 and, more recently, for phthalocyanines; 21 also we have used this methods to calculate spectroscopic transitions for transient species of 3-phenylquinoxalin-2-ones. 6 In the present work, our interest is to verify how simple semiempirical quantum mechanical calculations can account for the observed UV-visible spectral changes in the photoreduction of the studied oxoisoaporphines.…”

QSPR Study of Fluorescence Wavelengths (λex/λem) Based on the Heuristic Method and Radial Basis Function Neural Networks

“…The traditional computational approaches used to predict fluorescence wavelengths involve quantum chemistry methods such as density functional methods [7], ab initio [8], and semi-empirical methods (such as INDO and ZIN-DO) [9]. The accurate estimation of the fluorescence wavelengths from theoretical calculations is still a challenging task, since high levels of calculations are necessary for taking into account the effect of both the dynamical and nondynamical part of electron correlation, which is very difficult for a large size of the substituted fluorescence compounds.…”