Synthesis, X-ray Structure, and Electrochemical and Excited-State Properties of Multicomponent Complexes Made of a [Ru(Tpy)2]2+ Unit Covalently Linked to a -Catenate Moiety. Controlling the Energy-Transfer Direction by Changing the Catenate Metal Ion
1999-05-27T00:00:00Z (GMT) by
New multicomponent species consisting of -catenates incorporating the [Ru(tpy)2]2+ moiety (tpy = 2,2‘:6‘,2‘ ‘-terpyridine) within their framework have been prepared, and their electrochemical and photophysical properties have been studied. The parent compound of the investigated species is a previously described Cu(I) catenate (RuCu) containing a [Cu(dap)2]+ fragment (dap = 2,9-dianisyl-1,10-phenanthroline) used as a template and a [Ru(tpy)2]2+ unit integrating one of the interlocked rings. Selective demetalation of the Cu(I) catenate moiety of RuCu afforded a catenand (Ru) containing the [Ru(tpy)2]2+-type component and a free tetrahedral coordination site. Reaction of this catenand with Ag+ and Zn2+ ions yielded two new bimetallic catenates (RuAg and RuZn, respectively). The solid-state structure of complexes RuCu and RuAg has been determined by X-ray diffraction. Electrochemical experiments have shown that the two moieties of the RuCu and RuAg catenates undergo independent redox processes. The photophysical properties of Ru, RuCu, RuZn, and RuAg have been investigated by steady-state and time-resolved techniques, and compared with those of appropriate model compounds. The absorption spectra do not show any appreciable ground-state electronic interactions between the -catM (cat = catenand, catM = catenate) and [Ru(tpy)2]2+-type moieties, whereas luminescence properties reveal the occurrence of efficient photoinduced intercomponent energy- and/or electron-transfer processes, whose direction depends on the presence or on the nature of the metal ion in the -cat-type moiety. In Ru, RuZn, and RuAg such a moiety is quenched by the [Ru(tpy)2]2+ unit, whereas for RuCu the opposite behavior is observed. The rate constant of intercomponent processes are determined via time-resolved nano- and picosecond luminescence spectroscopy.