Structures and Electronic Properties of Si-Substituted Benzenes and Their Transition-Metal Complexes

Structural and electronic properties for a series of silicon-substituted benzenes (C n Si m H 6, where n = 0−6, m = 0−6, and n + m = 6) are studied through density functional theory calculations. Benzene is found to sustain its planarity up to two Si substitutions for all isomers. For three Si substitutions, only the 1,3,5-alternate structure ( 6 ) is planar, while for four Si substitution, only the 2,3,5,6 structure ( 10 ) is planar. Further Si substitution makes all the isomers for the rings nonplanar, which eventually leads to the fully puckered C 3 v structure for hexasilabenzene ( 13 ). The reorganization energies for these molecules are sufficiently low to be favorably utilized for hole conduction. All the molecules form very stable full-sandwich and half-sandwich complexes of the type η 6 -(C n Si m H 6 ) 2 Cr and η 6 -(C n Si m H 6 )Cr(CO) 3 . The binding energies for these complexes increase with increase in the number of Si atoms in the rings. Strategies are proposed for experimental design of extended sheets of silicenes and mixed C/Si graphenes through transition-metal complexation of the six-membered rings.