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In this study, we performed a detailed investigation of the S 1 potential energy surface (PES) of o -carborane–anthracene ( o -CB– Ant ) with respect to the C–C bond length on o -CB and the dihedral angle between o -CB and Ant moieties. The effects of different substituents (F, Cl, CN, and OH) on carbon- or boron-substituted o -CB, along with a π-extended acene-based fluorophore, pentacene, on the nature and energetics of S 1 → S 0 transitions are evaluated. Our results show the presence of a non-emissive S 1 state with an almost pure charge transfer (CT) character for all systems as a result of significant C–C bond elongation (C–C = 2.50–2.56 Å) on o -CB. In the case of unsubstituted o -CB– Ant , the adiabatic energy of this CT state corresponds to the global minimum on the S 1 PES, which suggests that the CT state could be involved in emission quenching. Despite large deformations on the o -CB geometry, predicted energy barriers are quite reasonable (0.3–0.4 eV), and the C–C bond elongation can even occur without a noticeable energy penalty for certain conformations. With substitution, it is shown that the dark CT state becomes even more energetically favorable when the substituent shows −M effects (e.g., −CN), whereas substituents showing +M effects (e.g., −OH) can result in an energy increase for the CT state, especially for partially stretched C–C bond lengths. It is also shown that the relative energy of the CT state on the PES depends strongly on the LUMO level of the fluorophore as this state is found to be energetically less favorable compared to other conformations when anthracene is replaced with π-extended pentacene. To our knowledge, this study shows a unique example of a detailed theoretical analysis on the PES of the S 1 state in o -CB– fluorophore systems with respect to substituents or fluorophore energy levels. Our findings could guide future experimental work in emissive o -CB– fluorophore systems and their sensing/optoelectronic applications.

Triarylboranes containing linear or angular benzodithiophene moieties and bearing one or two dimesitylboron units were synthesized. The electrochemical and optical features of these compounds were investigated by cyclic voltammetry, UV/Vis and fluorescence spectroscopy while DFT calculations were run to analyze the energetic landscape of these systems. For both linear and angular benzodithiophenes, symmetrical disubstitu-tion leads to the highest photoluminescence yields. The linear benzodithiophene disubstituted with two dimesitylboron units proved to be the most interesting and promising molecule as an electron-transport material for organic electronics owing to its LUMO energy level of À 2.84 eV which is close to those of commonly used electron transport materials like bathocuproine or bathophenantroline.

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