Polymorphism and White Light Emission of 1-Bromo-3,5,7-triphenyladamantane Compared with 1,3,5,7-Tetraphenyladamantane

Abstract

Here we report our investigation of 1-bromo-3,5,7-triphenyladamantane (1) and the elucidation of polymorphic crystals (1 A and 1 B) using single crystal X-ray diffraction. In the monoclinic crystal system of 1 A (P21/n), we observed CH–π interactions, while Br⋅⋅⋅Br interactions are absent. Conversely, the Br⋅⋅⋅Br interactions are an apparent factor in the formation of the monoclinic crystal system of 1 B (Rmathematical equation ). We compare our findings with 1,3,5,7-tetraphenyladamantane (2), characterized by numerous CH–π interactions in the solid. Computational analyses were employed to investigate the interactions within the characteristic dimers present in the unit cells of 1 A and 1 B, including visualization of noncovalent interactions and the use of the atoms-in-molecules approach as well as MO analyses. These support the notion of London dispersion (LD) dimer-dimer interactions in 1 A between the phenyl moieties, whereas 1 B exhibits additional dimer-dimer Br⋅⋅⋅Br contacts. In contrast, the crystals of 2 are exclusively held together by CH–π stacking LD interactions, a feature absent in the polymorphs of 1. Both polymorphic forms of 1 emit white light when subjected to 900 nm continuous wave laser irradiation, displaying a subtle blue shift compared to 2. The absence of CH–π stacking interactions between the dimers of 1 causes a small red-shift in the emission spectrum.