Synthesis and Characterization of Optically Active and Racemic Forms of Cyclometalated Rh(lll) Complexes. An Experimental and Theoretical Emission Study

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