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Romero AH, Romero IE, Piro OE, Echeverría GA, Gotopo LA, Moller MN, Rodríguez GA, Cabrera GJ, Castro ER, López SE, Cerecetto HE. Photo-Induced Partially Aromatized Intramolecular Charge Transfer. J Phys Chem B 2021; 125:9268-9285. [PMID: 34357778 DOI: 10.1021/acs.jpcb.1c03747] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Diverse models of intramolecular charge transfer (ICT) have been proposed for interpreting the origin of the charge-transfer (CT) state in donor-acceptor (D-A) dyes. However, a large variety of fused-heterocyclic dyes containing a pseudo-aromatic ring in the rigid structure have shown to be incompatible with them. To approximate a solution within the ICT concept, we reported a novel ICT model called partially aromatized intramolecular charge transfer (PAICT). PAICT involves the generation of a CT state from an ICT that occurred within a pre-excited D-A fused-heterocyclic structure possessing a pseudo-aromatic or unstable aromatic ring as the acceptor moiety. The model was proposed from the multiple-emissive mesomeric D-A N1-aryl-2-(trifluoromethyl)benzo[b][1,8]naphthyridin-4(1H)-one, whose excited mesomeric states, which are defined by the aromatic and pseudo-aromatic forms of the pyrindin-4(1H)-one ring, led to a common partial aromatized CT state upon excitation via PAICT. The latter was supported through theoretical calculations on the excited mesomeric states, one-dimensional (1D) and two-dimensional (2D) excitation-emission measurements in different solvents, and the detection of three excited states by lifetime measurements upon 370 nm excitation. The existence of mesomerism was supposed from: (i) two overlapping bands at 370-390 (or 400-420 nm) in UV-vis spectra, (ii) the direct interaction between the pyridinic nitrogen of one molecule and the carbonylic oxygen of the other found in the solid state and, (iii) the detection of three excited states by lifetime measurements. The PAICT opens new perspectives for interpreting the charge-transfer phenomenon in fused-heterocyclic dyes, in particular, those containing a pseudo-aromatic or unstable aromatic ring as an acceptor moiety.
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Affiliation(s)
- Angel H Romero
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay
| | - Ivan E Romero
- Laboratorio de Síntesis Orgánica, Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1040, Venezuela
| | - Oscar E Piro
- Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de la Plata, La Plata 1900, Argentina
| | - Gustavo A Echeverría
- Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de la Plata, La Plata 1900, Argentina
| | - Lourdes A Gotopo
- Laboratorio de Síntesis Orgánica, Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1040, Venezuela
| | - Matías N Moller
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay
| | - Gonzalo A Rodríguez
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay
| | - Gustavo J Cabrera
- Laboratorio de Síntesis Orgánica, Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1040, Venezuela
| | - Erick R Castro
- Instituto de Física da UFRGS, Av. Bento Gonçalves, Porto Alegre 9500, RS, Brazil
| | - Simón E López
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Hugo E Cerecetto
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.,Área de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Mataojo 2055, Montevideo 11400, Uruguay
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