caa a22 4500 605488428 CHVBK 20210128100455.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s00214-015-1619-5 doi (NATIONALLICENCE)springer-10.1007/s00214-015-1619-5 Triplet-singlet gap in structurally flexible organic diradicals [Elektronische Daten] [Daniel Reta Mañeru, Ibério de Moreira, Francesc Illas] A key factor in the search of high-spin ground state purely organic molecules concerns the effect of the inherent non-rigid structures on the magnetic and optical properties. This structural feature has not been properly addressed in previous theoretical works. Here, based on the experimentally characterized high-spin ground state of dendritic and star-branched polyradicals, we study four alternant hydrocarbon biradicals that intend to model these effects and, at the same time, provide a first step toward understanding more extended experimental structures. A series of density functional theory (DFT) and of wave function-based methods have been used to explore the richness of structural minima in the corresponding potential energy surfaces and to discuss its effect on the triplet-singlet gap of the proposed model systems. For a given model, the DFT-based B3LYP, M06-2X and MN-12SX methods provide a consistent description. Likewise, a multiconfigurational quasi-degenerate perturbation theory approach with the minimal π space as CASSCF reference is found to provide unbiased results. Despite the conformational richness found for these systems, they all can be described by a reduced set of values referred to only two structural parameters, being those the dihedral angles between the phenyl rings. For a given model, there is no significant change in the triplet-singlet gap depending on the chosen local minima. Springer-Verlag Berlin Heidelberg, 2015 Diradicals nationallicence Triplet-singlet gap nationallicence CASSCF nationallicence MRQDPT nationallicence DFT nationallicence Reta Mañeru Daniel Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut Moreira Ibério de Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut Illas Francesc Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut Theoretical Chemistry Accounts Springer Berlin Heidelberg 134/2(2015-02-01), 1-10 1432-881X 134:2<1 2015 134 214 https://doi.org/10.1007/s00214-015-1619-5 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00214-015-1619-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Reta Mañeru Daniel Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut NATIONALLICENCE 700 1- Moreira Ibério de Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut NATIONALLICENCE 700 1- Illas Francesc Departament de Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain aut NATIONALLICENCE 773 0- Theoretical Chemistry Accounts Springer Berlin Heidelberg 134/2(2015-02-01), 1-10 1432-881X 134:2<1 2015 134 214