Engineering the HOMO–LUMO gap of indeno[1,2- b]fluorene Casares López, Raquel Martínez Pinel, Álvaro Rodríguez Márquez, Irene Blanco Suárez, Víctor Cuerva Carvajal, Juan Manuel Millán Delgado, Alba 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 (lmax 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. 2022-09-13T11:05:38Z 2022-09-13T11:05:38Z 2022-07-28 info:eu-repo/semantics/article J. Mater. Chem. C, 2022, 10, 11775. DOI: [10.1039/d2tc02475f] http://hdl.handle.net/10481/76679 10.1039/d2tc02475f eng http://creativecommons.org/licenses/by-nc/4.0/ info:eu-repo/semantics/openAccess Atribución-NoComercial 4.0 Internacional Royal Society of Chemistry