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Updated: Mar 28, 2026

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Interplay of Orbital Overlap and Exciton Coupling in the Optical Properties of Adamantylethynyl-Substituted Pyrene
Benedikt Herbert1, Kazutaka Shoyama1
1Center for Nanosystems Chemistry (CNC) and Institut für Organische Chemie, Universität Würzburg, Würzburg, Germany.
Abstract:
Molecular crystals of apolar π-conjugated hydrocarbons exhibit pronounced solution-to-crystal spectral shifts, yet the interplay between band formation and exciton coupling remains unclear. Adamantylethynyl-pyrene derivatives were designed to adopt unidirectional crystal packing, providing a model system to disentangle these effects. Large redshifts of up to -203 meV are observed, which cannot be explained by exciton coupling alone but require a substantial contribution from band dispersion, identified here as a narrowing of frontier crystal orbital energy levels. The remaining discrepancies between experiment and the full-coherence limit correspond to coherence lengths of four to seven molecules, consistent with literature values. These results provide a basis for interpreting more complex organic crystalline materials and highlight the need for a more comprehensive understanding of the photophysical properties of molecular crystals.
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