Theoretical modulation of singlet/triplet chemiexcitation of chemiluminescent imidazopyrazinone dioxetanone via C8-substitution

Author(s): L. Pinto da Silva ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , C. M. Magalhães ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , D. M. A. Crista ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , J. C. G. Esteves da Silva ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵

Publication date (Electronic): 2017

Journal: Photochemical & Photobiological Sciences

Publisher: Royal Society of Chemistry (RSC)

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Abstract

DFT analysis of the thermolysis of C ₈-substituted imidazopyrazinone dioxetanone allows the rational tuning of the activation barrier and singlet/triplet chemiexcitation.

Abstract

Coelenterazine, a member of the imidazopyrazinone class of chemiluminescent substrates, presents significant potential as a dynamic probe of reactive oxygen species in a biological environment, such as a superoxide anion, in which these species are important in cellular biology and pathology. The objective of the current study was to understand in what way the efficiency of singlet and triplet chemiexcitation could be modulated, towards a more efficient use of imidazopyrazinone-based compounds as dynamic chemiluminescent probes. To this end the thermolysis of imidazopyrazinone dioxetanone, substituted at the C ₈-position with electron-donating or electron-withdrawing groups, was characterized with a theoretical approach based on density functional theory. Substituents with different electron-donating/withdrawing characters have only a limited effect on the singlet chemiexcitation of anionic dioxetanone. For neutral dioxetanone, both electron-withdrawing and weak electron-donating substituents increase singlet chemiexcitation, to the contrary of strong electron-donating groups. During their thermolysis reaction, all molecules presented regions of degeneracy with triplet states, thereby indicating the possibility of triplet chemiexcitation.

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The calculations of excited-state properties with Time-Dependent Density Functional Theory.

Carlo Adamo, Denis Jacquemin (2013)

In this tutorial review, we show how Time-Dependent Density Functional Theory (TD-DFT) has become a popular tool for computing the signatures of electronically excited states, and more specifically, the properties directly related to the optical (absorption and emission) spectra of molecules. We discuss the properties that can be obtained with widely available programs as well as how to account for the environmental effects (solvent and surfaces) and present recent applications in these fields. We next expose the transformation of the TD-DFT results into chemically intuitive parameters (colours as well as charge-transfer distances). Eventually, the non-specialised reader will find a series of advices and warnings necessary to perform her/his first TD-DFT calculations.