Synthesis and characterization of optically active and racemic forms of cyclometalated Rh(III) complexes. An experimental and theoretical emission study

The optically active cyclometalated Rh(III) complexes, Delta[Rh(thpy4,5p(RR)PY)(2)TAP]CI, Lambda[Rh(thpy4,5p(S,S)py)(2)TAP]-Cl, and Delta[Rh(phpy4,5p(RR)py)(2)TAP]CI (where TAP = 1,4,5,8-tetraazaphenanthrene, thpy4,5p(RR)py = (8R,10R)-2-(2'-thienyl)-4,5-pinenopyridine and phpy4,5p(RR)py = (8R,10R)-2-(2'-phenyl)-4,5-pinenopyridine) have been prepared and characterized. Their photophysics has been examined in parallel with that of rac[Rh(thPY)(2)TAP]CI and rac[Rh(phpy)(2)TAP]Cl. Their behaviors have been rationalized from results of TD-DFT calculations. The complexes with thienylpyridine (thpy) as cyclometalating ligands exhibit (CT)-C-3 (from thpy to TAP) and (LCpi-pi)-L-3 (centered on thpy) emissions in a solvent matrix at 77 K and one (CT)-C-3 luminescence at room temperature. In contrast, with phenylpyridine (phpy), the complexes show only one (CT)-C-3 emission (from phpy to TAP) at both temperatures.