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

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 (P2(1)/n), we observed CH-pi interactions, while Br center dot center dot center dot Br interactions are absent. Conversely, the Br center dot center dot center dot Br interactions are an apparent factor in the formation of the monoclinic crystal system of 1 B (R (3) over bar). We compare our findings with 1,3,5,7-tetraphenyladamantane (2), characterized by numerous CH-pi 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 center dot center dot center dot Br contacts. In contrast, the crystals of 2 are exclusively held together by CH-pi 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-pi stacking interactions between the dimers of 1 causes a small red-shift in the emission spectrum.