Steady-state spectra (fluorescence, excitation, and absorption) and fluorescence decay of several substituted alkoxysilanes were measured in a broad range of temperatures, -100 to 50 degrees C. Special emphasis was put on compounds which are potential models for the repeat unit in poly(methylphenylsiloxane). In the absorption spectra, the vibrational resolution and the molar absorptivity (at maximum absorbance) depend very much on the type of groups joined to the silicon atom. Fluorescence decays were monoexponential at any temperature. Both the lifetime and the fluorescence intensity show a non-Arrhenius dependence at the low temperatures. Some conclusions were derived on the choice of a proper monochromophoric model compound for a polychromophoric chain.