The photophysics of naphthalene dimers controlled by sulfur bridge oxidation
Résumé
In this study we investigate in detail the photophysics of naphthalene dimers covalently linked by a sulfur atom. We explore and rationalize how the oxidation state of the sulfur-bridging atom directly influences the photoluminescence of the dimer by enhancing or depriving radiative and non-radiative relaxation pathways. In particular, we discuss how oxidation controls the amount of electronic transfer between naphthalene moieties and the participation of the SO n bridge in the low-lying electronic transitions. We identify the sulfur electron lone-pairs as crucial actors in the non-radiative decay of the excited sulfide and sulfoxide dimers, which are predicted to go via a conical intersection (CI). Concretely, two types of CI have been identified for these dimers, which we associate with photo-induced pyramidal inversion and reverse fragmentation mechanisms in aryl sulfoxide dimers. The obtained results and conclusion are general enough to be extrapolated to other sulfur-bridged conjugated dimers, therefore proportionating novel strategies in the design of strong photoluminescence organic molecules with controlled charge transfer.
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