HIGHLY RESOLVED OPTICAL-SPECTRA OF PD(2-THPY)(2) IN A SHPOLSKII MATRIX

Pd(2-thpy)(2) is a representative of the interesting new class of ortho-metalated compounds. For the first time, we present highly resolved emission and excitation spectra. This could be achieved by using the Shpol'skii matrix isolation technique. From the intensity distribution of the highly resolved vibrational satellite structures and the corresponding vibrational energies it is concluded that the excited triplet lying at 18 418 +/- 1 cm(-1) and the singlet ground state exhibit nearly the same force constants and equilibrium positions of the potential hypersurfaces. The type of the electronic transition is assigned as being ligand centered with a relatively small MLCT admixture. The zero-field splitting of the triplet could not be resolved (experimental resolution 1 cm(-1)), but at T = 1.3 K the three sublevels emit independently with tau(1) = 155 +/- 20 mu s, tau(2) approximate to 200 mu s, and tau(3) = 1200 +/- 100 mu s, respectively. With increasing temperature and thus increasing spin-lattice relaxation the emission lifetime becomes monoexponential with tau(4.2 K) = 235 +/- 10 mu s.