SPECTROSCOPIC STUDIES OF CYCLOMETALATED PLATINUM(II) COMPLEXES - SUPERPOSITION OF 2 DIFFERENT SPECTROSCOPIC SPECIES IN THE ELECTRONIC-SPECTRA OF A SINGLE-CRYSTAL OF [PT(2,2'-BIPYRIMIDINE)(CN)2]

The influence of temperature (1.9 ≤ T ≤ 80 K) and applied magnetic fields (0 ≤ H ≤ 6 T) on the optical properties of a single crystal of [Pt(bpm)(CN)2] (bpm = 2,2′-bipyrimidine) is reported. These properties are due to two different kinds of chains (α and β) in the crystal. Chain α consists of quasi-isolated complexes with alternating Pt-Pt distances of 4.178 and 3.438 Å; chain β has a dimeric structure with Pt-Pt distances of 4.581 and 3.269 Å. At T = 1.9 K a luminescence exhibiting a sharp-line structure in the high-energy range and a broad weakly structured band in the low-energy range has been observed. The emission indicates a superposition of the electronic transitions in the α and β chains. When a magnetic field H‖a is raised from H = 0 to 6 T, the intensity of the E‖a polarized fine-structure lines increases by a factor of ~ 70. An applied magnetic field H ⊥ a La provides an increase of the H ⊥ a and H ‖ a polarized dimer emission by factors of 5 and 4, respectively. Both effects are explained by a magnetic field induced mixing of the lowest excited state with higher states. Crystallographic data for [Pt(bpm)(CN)2]: triclinic, space group @@Pl̄, a = 7.261 (1) Å, b = 10.828 (1) A, c = 14.387 (1) Å, α = 88.54 (1)°, β = 82.78 (1)°, γ = 74.07 (1)°, V= 1072.34 Å3, Z = 4, Dx = 2.51 g.cm−3, μ(Cu Kα) = 249.0 cm−1, R = 0.025 and Rw = 0.033 for 344 variables and 4411 reflections with I > 3σ(I). © 1990, American Chemical Society. All rights reserved.