Electronic spectra of cyclotrisilane (Si3) and disilene (Si=Si) frameworks.

Photolyses of a series of octaalkylcyclotetrasilanes (1) in a hydrocarbon solvent successively afforded hexaalkylcyclotrisilanes (2) and tetraalkyldisilenes (3). Compounds 2 and 3 were found to exhibit their absorption bands corresponding to the lowest energy transitions at λmax 300–330 and 390–440 nm, respectively.