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 orth o-metalated compounds. For the first time, we present highly resolved emission and excitation spectra. This could be achieved by using the S hpol'skii matrix isolation technique. From the intensity distribution of the highly resolved vibrational satellite structures and the corres ponding vibrational energies it is concluded that the excited triplet lying at 18 418 +/- 1 cm(-1) and the singlet ground state exhibit near ly the same force constants and equilibrium positions of the potential hypersurfaces. The type of the electronic transition is assigned as b eing ligand centered with a relatively small MLCT admixture. The zero- field splitting of the triplet could not be resolved (experimental res olution 1 cm(-1)), but at T = 1.3 K the three sublevels emit independe ntly with tau(1) = 155 +/- 20 mu s, tau(2) approximate to 200 mu s, an d tau(3) = 1200 +/- 100 mu s, respectively. With increasing temperatur e and thus increasing spin-lattice relaxation the emission lifetime be comes monoexponential with tau(4.2 K) = 235 +/- 10 mu s.