Author, as appears in the article.: Reguero, M; Mireia Segado Centelles; Isabel Gomez

Department: Química Física i Inorgànica

URV's Author/s: REGUERO DE LA POZA, MARIA DEL MAR; Mireia Segado Centelles; Isabel Gomez

Abstract: Recent theoretical and experimental studies on the Intramolecular Charge Transfer (ICT) reaction of some members of the aminobezonitrile family (ABN) suggest the involvement of a (π–σ*) excited state (called ICT(CN) in this work) in the ICT process and the existence of a partially twisted ICT species that could be responsible for the anomalous fluorescence observed. These suggestions made us to revise our previous study on the photophysics of ABN and dimethyl-ABN (DMABN), based on the analysis of the potential energy surfaces of the low-lying excited states by means of ab initio calculations, using the CASSCF/CASPT2 protocol. We have first focused our attention to ABN. We have found that the (π–σ*) excited state can be in fact an intermediary state in the path to populate the ICT bright state, although its involvement in the process is not very probable. Our results suggest that the ICT most stable species is the twisted ICT(TICT) and that the partially twisted ICT minimum found in previous studies could be an artefact of the computational method. We have also found that radiationless deactivation is a competitive reaction that must be taken into account to explain the fluorescence patterns of these systems. To confirm our theories, we have also studied other systems with a similar architecture but with a very different luminescence behaviour: dimethyl-ABN, and the 2,3,4,5-tetrafluoro derivatives of ABN and DMABN (ABN-4F and DMABN-4F). The extension of the work and the different approaches in the study of the parent system and of the derivatives make the division of the work in two parts advisable. Part I collects the characterization of the minima and reaction paths connecting the critical points of the potential energy surfaces of the states involved in the ICT reaction of ABN. We have obtained, for the first time, the pathways of radiationless deactivation for this compound. We have also computed transition energies from the excited minima, to interpret the excited state absorption (ESA) spectra obtained experimentally. This information helps in the elucidation of the mechanism of ICT. In Part II we show an analoguous study for DMABN and ABN-4F and DMABN-4F and analyse and compare these results and those of Part I to explain different luminescence behaviours of the four systems studied.

Research group: Química Quàntica

Thematic Areas: Chemistry Química Química

licence for use: https://creativecommons.org/licenses/by/3.0/es/

ISSN: 1463-9076

Author identifier: 0000-0001-9668-8265; ;

Record's date: 2019-01-11

Last page: 6874

Journal volume: 18

Papper version: info:eu-repo/semantics/publishedVersion

Link to the original source: https://pubs.rsc.org/en/content/articlelanding/2016/CP/C5CP04690D#!divAbstract

Article's DOI: 10.1039/c5cp04690d

Entity: Universitat Rovira i Virgili

Journal publication year: 2016

First page: 6861

Publication Type: Article Artículo Article