The structure of closo-Si12C12 is unique among stable SinCm isomers (n, m > 4) because of its high symmetry, π–π stacking of C6 rings and unsaturated silicon atoms at symmetrical peripheral positions. Dimerization potential surfaces reveal various dimerization reactions that form between two closo-Si12C12 molecules through Si–Si bonds at unsaturated Si atoms. As a result the closo-Si12C12 molecule is capable of polymerization to form stable 1D polymer chains, 2D crystal layers, and 3D crystals. 2D crystal structures formed by side-side polymerization satisfy eight Si valences on each monomer without large distortion of the monomer structure. 3D crystals are formed by stacking 2D structures in the Z direction, preserving registry of C6 rings in monomer moiety.
Journal of Chemical Physics
Xiaofeng F. Duan, Larry W. Burggraf; The closo-Si12C12 molecule from cluster to crystal: A theoretical prediction. J. Chem. Phys. 21 March 2016; 144 (11): 114309. https://doi.org/10.1063/1.4943957