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

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2022-08, Vol.10 (32), p.11775-11782
• Main Authors: Casares, Raquel, Martínez-Pinel, Álvaro, Rodríguez-González, Sandra, Márquez, Irene R., Lezama, Luis, González, M. Teresa, Leary, Edmund, Blanco, Víctor, Fallaque, Joel G., Díaz, Cristina, Martín, Fernando, Cuerva, Juan M., Millán, Alba
• Format: Article
• Language: English
• Subjects: Acetylene; Energy gap; First principles; Magnetic properties; Molecular orbitals; Optoelectronics
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D2TC02475F

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.