Author, as appears in the article.: Josep Casellas; Gerard Alcover-Fortuny; Coen de Graaf ; Mar Reguero
Department: Química Física i Inorgànica
e-ISSN: 1996-1944
URV's Author/s: De Graaf, Cornelis / Reguero de la Poza, Maria del Mar
Keywords: Thermal relicts Reaction mechanism Photochemistry Phenylazopyridine Pannonian region Mechanism of reaction Holocene thermal maximum Excited states Disjunction Casscf/caspt2 photoisomerization photochromism phenylazopyridine casscf/caspt2
Abstract: Azo compounds are organic photochromic systems that have the possibility of switching between cis and trans isomers under irradiation. The different photochemical properties of these isomers make azo compounds into good light-triggered switches, and their significantly different geometries make them very interesting as components in molecular engines or mechanical switches. For instance, azo ligands are used in coordination complexes to trigger photoresponsive properties. The light-induced trans-to-cis isomerization of phenylazopyridine (PAPy) plays a fundamental role in the room-temperature switchable spin crossover of Ni-porphyrin derivatives. In this work, we present a computational study developed at the SA-CASSCF/CASPT2 level (State Averaged Complete Active Space Self Consistent Field/CAS second order Perturbation Theory) to elucidate the mechanism, up to now unknown, of the cis-trans photoisomerization of 3-PAPy. We have analyzed the possible reaction pathways along its lowest excited states, generated by excitation of one or two electrons from the lone pairs of the N atoms of the azo group (nazo pi*2 and nazo2 pi*2 states), from a pi delocalized molecular orbital (pi pi* state), or from the lone pair of the N atom of the pyridine moiety (npy pi* state). Our results show that the mechanism proceeds mainly along the rotation coordinate in both the nazo pi* and pi pi* excited states, although the nazo2 pi*2 state can also be populated temporarily, whilethe npy pi* does not intervene in the reaction. For rotationally constrained systems, accessible paths to reach the cis minimum along planar geometries have also been located, again on the nazo pi* and pi pi* potential energy surfaces, while the nazo 2 pi*2 and npy pi* states are not involved in the reaction. The relative energies of the different paths differ from those found for azobenzene in a previous work, so our results predict some differences between the reactivities of both compounds.
Thematic Areas: Química Odontología Medicina veterinaria Medicina i Materials science, multidisciplinary Materiais Interdisciplinar General materials science Engenharias iv Engenharias iii Engenharias ii Engenharias i Condensed matter physics Ciências biológicas ii Ciências biológicas i Ciências agrárias i Ciência de alimentos Ciência da computação Biotecnología Astronomia / física Arquitetura, urbanismo e design
licence for use: https://creativecommons.org/licenses/by/3.0/es/
ISSN: 19961944
Author's mail: coen.degraaf@urv.cat mar.reguero@urv.cat
Author identifier: 0000-0001-8114-6658 0000-0001-9668-8265
Record's date: 2023-02-22
Journal volume: 10
Papper version: info:eu-repo/semantics/publishedVersion
Papper original source: Materials. 10 (12): 1342-
APA: Josep Casellas; Gerard Alcover-Fortuny; Coen de Graaf ; Mar Reguero (2017). Phenylazopyridine as switch in photochemical reactions. A detailed computational description of the mechanism of its Photoisomerization. Materials, 10(12), 1342-. DOI: 10.3390/ma10121342
Licence document URL: https://repositori.urv.cat/ca/proteccio-de-dades/
Entity: Universitat Rovira i Virgili
Journal publication year: 2017
Publication Type: Journal Publications
Repositori URV