Low and High Z′Polymorphs of Dibenzyldiphenylsilane: A Hydrocarbon-Patterned Molecular Crystalline System

Studying weak intermolecular interactions in molecular crystals is key to a better understanding of crystalline polymorphism and structure formation principles. Dibenzyldiphenylsilane (1) was synthesized as a hydrocarbon-patterned molecular model compound. Three polymorphic crystal structures, one with Z′= 1 (1-t, triclinic, P1̅), one with Z′= 2 (1-o, orthorhombic, Pna21), and another with Z′= 4 (1-m, monoclinic, Pc), were analyzed by single-crystal X-ray diffraction analysis. Subtle differences in the weak intermolecular interactions between the three polymorphic crystal packing arrangements were thoroughly investigated by Hirshfeld surface analysis along with two-dimensional fingerprint plots. The highest Z′polymorph (1-m) has the lowest packing density but exhibits the shortest intermolecular H···H and C–H···π contacts. Conformational differences and the contribution of dispersion interactions to the stability of the three polymorphic crystal structures were investigated by means of density functional theory (DFT) calculations, comparing different functionals. The Z′> 1 polymorphs undergo phase transitions into the triclinic form 1-t(Z′= 1) at room temperature.