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 the P2(1)/a space group with the following unit-cell dimensions: a=17.192(5), b= 15.593(2) and c=18.178(4) Angstrom, beta=91.27(2)degrees, V=4879(3) Angstrom(3), Z=8. R=0.031, (R(w)=0.028) for 8573 unique reflections. There are two molecules, Ia and Ib, in the asymmetric unit. Compound 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 phosphorus 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 absorption spectra of I and II have been assigned to metal-to-ligand charge transfer (MLCT) transitions, while higher energy bands have been assigned to ligand-centered (LC) transitions. Compound II shows strong emission in solution at room temperature. The presence of the large phosphorus 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 type of electronic structure of the complexes both in solution and in the solid state.