CRYSTAL-STRUCTURES AND SPECTROSCOPIC PROPERTIES OF TRANS-N,P-[PT(PPY)(PMOR(3))CL] AND TRANS-N,P-[PT(TPY)(PMOR(3))CL]CENTER-DOT-CH3CN [PPY=N,C'-CHELATED 2-PHENYLPYRIDINATE, TPY=N,C'-CHELATED 2-(2'-THIENYL)PYRIDINATE, PMOR(3)=TRIS(MORPHOLINO)PHOSPHINE]

The crystal structures of [Pt(ppy) (Pmor(3))Cl], I, and [Pt(tpy)-(Pmor (3))Cl]. CH3CN, II, have been determined at 93 K. I crystallizes in th e P2(1)/a space group with the following unit-cell dimensions: a=17.19 2(5), b= 15.593(2) and c=18.178(4) Angstrom, beta=91.27(2)degrees, V=4 879(3) Angstrom(3), Z=8. R=0.031, (R(w)=0.028) for 8573 unique reflect ions. There are two molecules, Ia and Ib, in the asymmetric unit. Comp ound II crystallizes in the same space group, a= 12.415(4), b=12.731(4 ) and c=16.702(6) Angstrom, beta=105.42(2)degrees, V=2543(2) Angstrom( 3), Z=4. R=0.026 (R(w)=0.033) for 6396 unique reflections. The phospho rus ligand is located trans to the nitrogen atom of the cyclometalated ligand with a Pt-N bond length of 2.106(5) Angstrom in Ia 2.111(5) in Ib and 2.134(3) Angstrom in II. Long-wave absorption bands in the abs orption spectra of I and II have been assigned to metal-to-ligand char ge transfer (MLCT) transitions, while higher energy bands have been as signed to ligand-centered (LC) transitions. Compound II shows strong e mission in solution at room temperature. The presence of the large pho sphorus ligand leads to long Pt-Pt distances, the shortest being 5.988 (5) Angstrom in I and 7.777(4) Angstrom in II, preserving monomeric ty pe of electronic structure of the complexes both in solution and in th e solid state.