Engineering the HOMO–LUMO gap of indeno[1,2-b]fluorene

Raquel Casares; Álvaro Martínez-Pinel; Sandra Rodríguez-González; Irene R. Márquez; Luis Lezama; M. Teresa González; Edmund Leary; Víctor Blanco; Joel G. Fallaque; Cristina Díaz; Fernando Martín; Juan M. Cuerva; Alba Millán

doi:10.1039/D2TC02475F

Engineering the HOMO–LUMO gap of indeno[1,2-b]fluorene†‡

Raquel Casares,

^a Álvaro Martínez-Pinel,

^a Sandra Rodríguez-González,

^b Irene R. Márquez,

^c Luis Lezama,

^d M. Teresa González,

^e Edmund Leary,

^e Víctor Blanco,

^a Joel G. Fallaque,

^ef Cristina Díaz,

^g Fernando Martín,

^efh Juan M. Cuerva

*^a and Alba Millán

*^a

Author affiliations

* Corresponding authors

^a Departamento de Química Orgánica, Facultad de Ciencias, Unidad de Excelencia de Química Aplicada a Biomedicina y Medioambiente (UEQ), Universidad de Granada, 18071 Granada, Spain
E-mail: jmcuerva@ugr.es, amillan@ugr.es

^b Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid, Spain

^c Centro de Instrumentación Científica, Universidad de Granada, 18071 Granada, Spain

^d Departamento de Química Orgánica e Inorgánica, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Leioa, Spain

^e Fundación IMDEA Nanociencia, Madrid, Spain

^f Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Madrid, Spain

^g Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain

^h Condensed Matter Physics Center (IFIMAC), Madrid, Spain

Abstract

A direct, efficient and versatile strategy for the modulation of optoelectronic and magnetic properties of indeno[1,2-b]fluorene has been developed. 4-Substituted-2,6-dimethylphenyl acetylene groups placed in the apical carbon of the five-membered rings lead to redshifted absorption maxima (λ_max ranging from 600–700 nm) and considerable narrowing of the HOMO–LUMO energy gap (down to 1.5 eV). Experimental and theoretical data show an increase in the diradical character (y) and a decrease of the singlet-triplet energy gap. Moreover, we have investigated the single-molecule conductance of the antiaromatic indeno[1,2-b]fluorene for the first time by including thiomethyl (-SMe) anchor groups on the phenylacetylene moiety. Conductance values one order of magnitude higher than those of a reference linear 3-ring para-phenylene ethylene have been found, despite the longer length of the S-to-S molecular junction. First principles transport calculations support this high conductance value.

Journal of Materials Chemistry C

Engineering the HOMO–LUMO gap of indeno[1,2-b]fluorene†‡

Abstract

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Engineering the HOMO–LUMO gap of indeno[1,2-b]fluorene

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