Zero-phonon and vibronic structure of [Os(bpy)₃]²⁺ doped into single-crystal [Ru(bpy)₃])ClO₄)₂

Abstract

Highly resolved emission and absorption spectra of [Os(bpy)₃]²⁺, doped into single-crystal [Ru(bpy)₃](C1O₄)₂, are reported. Our investigations, at low temperatures (2 <= T <= 50 K) and high magnetic fields (0 <= H <= 6 T), lead to the following results: The three lowest excited states of [Os(bpy)₃]²⁺ in this matrix are identified from zero-phonon transitions lying at 14 169 ± 2 cm⁻¹ (line I), 14230 ± 2 cm⁻¹ (line II), and 14380 ± 2 cm⁻¹ (line III). These transitions are found at the same energies (within the experimental error of ± 2 cm⁻¹) in absorption and emission. The extinction coefficients of II and III are ca. 10³ l mol⁻¹ cm⁻¹ while the transition |0) —› |I) (line I) is strongly forbidden. However, under high magnetic fields this absorption line grows in due to a mixing of |I) with |II). A large number of vibronic peaks is identified in the emission spectra. The corresponding vibrational modes are compared to Raman and IR data of [Ru(bpy)₃]²⁺ and [Os(bpy)₃]²⁺. Several distinct modes couple more strongly to the transition from the lowest excited state |I), others to the transition from |II), as is shown by investigating the magnetic field dependence of the emission spectra.