Gryl Marlena, Ostrowska Katarzyna, Barquera-Lozada Jose Enrique, Stadnicka Katarzyna M
Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland.
Instituto de Química, Universidad Nacional Autónoma de México, Circuito exterior, Ciudad Universitaria Coyoacán, México, DF 04510, Mexico.
J Phys Chem A. 2020 Apr 16;124(15):2931-2941. doi: 10.1021/acs.jpca.9b10651. Epub 2020 Apr 6.
Triazaacephenanthrylene (TAAP) triclinic single crystals show substantial optical anisotropy of absorption and fluorescence. The maximum effect can be correlated with the direction perpendicular to the plane of chromophores connected in a head-to-tail manner via weak dispersive interactions. This phenomenon is uncommon as usually the existence of postulated π···π interactions between the molecules forming dimers or stacks cause quenching of fluorescence. Herein we present a comprehensive study of inter- and intramolecular interactions in the crystal of TAAP enriched with the investigation of aromaticity. Our results show that intramolecular interactions stabilize the overall conformation of the molecule whereas dispersive forces determine the aggregation between TAAP molecules. In fact, there is no conventional π···π interaction between the molecules in the dimer. Instead, we observed a close contact between the lone pair of the bridgehead N10B atom and π-deficient pyrazine ring from an adjacent molecule. Optical anisotropy in TAAP crystals was directly correlated with the alignment of the molecular transition dipole moments caused by specific molecular self-assembly.
三氮杂菲蒽（TAAP）三斜单晶表现出显著的吸收和荧光光学各向异性。最大效应与通过弱色散相互作用以头对头方式连接的发色团平面垂直方向相关。这种现象并不常见，因为通常形成二聚体或堆积的分子之间假定的π···π相互作用会导致荧光猝灭。在此，我们通过对芳香性的研究，对富含TAAP的晶体中的分子间和分子内相互作用进行了全面研究。我们的结果表明，分子内相互作用稳定了分子的整体构象，而色散力决定了TAAP分子之间的聚集。实际上，二聚体中的分子之间不存在传统的π···π相互作用。相反，我们观察到桥头N10B原子的孤对与相邻分子中缺π的吡嗪环之间存在紧密接触。TAAP晶体中的光学各向异性与由特定分子自组装引起的分子跃迁偶极矩的排列直接相关。
