Dipyridocatecholate-Bridged Complexes of Platinum and Ruthenium Diimine Chromophores

New Ru-Pt heterometallic complexes have been prepared and their electrochemical and luminescence properties characterized. One series of complexes contains a tris diimine-chelated Ru(II) center linked to one, two, or three Pt(II) diimine moieties via a dipyridocatecholate (dpcat; 1,10-phenanthroline-5,6-diolate) bridging ligand, as indicated by the general formula [(dbbpy)(3)(-)(n)()Ru((&mgr;-dpcat)Pt(dbbpy))(n)()](PF(6))(2) (n = 1-3) where dbbpy = di-tert-butylbipyridine. A different dinuclear complex has a tetrapyridophenazine (tppz) bridge connecting a Ru(diimine)(3)(2+) chromophore with a Pt diimine dithiolate center and has the formula [(dbbpy)(2)Ru(&mgr;-tppz)Pt(tdt)](2+) where tdt = toluene-3,4-dithiolate. The dpcat-bridged complexes exhibit numerous redox processes that are assigned on the basis of comparison of those shown by mononuclear precursors and analogues, i.e., Ru(diimine)(3)(2+) and Pt(dbbpy)(dpcat). The dpcat-bridged complexes display distinct absorption bands due to Ru(diimine)(3)(2+) and Pt(diimine)(diolate) chromophores at ca. 450 and 540 nm, respectively. Emission from the Pt center is observed at 77 K (but not at room temperature in fluid solution) upon direct irradiation of this center as well as excitation of the Ru center. The latter suggests the occurrence of energy transfer between Ru- and Pt-based components. The energy transfer appears to be efficient, but not complete for the dinuclear species [(dbbpy)(2)Ru(&mgr;-dpcat)Pt(dbbpy)](PF(6))(2), as indicated by residual Ru emission from this complex. In contrast with the observation of a Pt-based emission from the bridged dinuclear complexes, the mononuclear complex Pt(dbbpy)(dpcat) does not luminesce, even in rigid media at low temperature. The spectroscopic properties of the tppz-bridged complex [(dbbpy)(2)Ru(&mgr;-tppz)Pt(tdt)](2+) are very similar to those of [(dbbpy)(2)Ru(&mgr;-dpcat)Pt(dbbpy)](2+).