LUMINESCENCE OF TRIS(2,2'-BIPYRIDINE) RUTHENIUM(II) IN SOL-GEL GLASSES

The luminescence of tris(2,2'-bipyridine)ruthenium(II) (R2+) was studied in the sol-gel reaction system of tetraethyl orthosilicate. The spectrum showed a blue shift during the sol-gel stage, indicating R2+ to be entangled by siloxane polymers and finally to become bound tightly to the sol-gel silica. Although the relative rates of the spectral shift differed depending on the preparation conditions, a very similar tendency was obtained on plotting the emission maximum against the viscosity for solutions with a different water-to-silane ratio at pH = 3.0. The relation between the emission maximum and the viscosity of a solution at pH = 1.0 differed from cases at pH = 3.0. Electrostatic interaction between the surface of the siloxane polymer and R2+ is thus essential for stabilizing R2+ on the surface with the charge varying with pH.