Cyclacene tubes having silaannulenic peripheries—AM1 treatment Original Research Article

The cyclacene tubes T(R,r) consisting of the Hückel type intermolecularly unioned (r=6) cyclacenes having R arenoid rings (R=3−6) and a single silaannulenic periphery are considered for AM1 type semiempirical molecular orbital calculations. The cases in which the silaannulenic periphery occupies different locations (layers A–D from top to middle) along the tube axis are investigated. It has been found that doping of silicon atoms in the top (or bottom) periphery of the cyclacene tubes has a stabilizing effect irrespective of 4m or 4m+2 type character and thus no cryptoannulenic effect is exhibited. The silicon doping in every case is characterized with endothermic heats of formation with local minima for tubes with R=4.