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A series of compounds of the type [(bpy) 2 Ru(3,3′-XX-2,2′-bpy)] 2+ or [(dmb) 2 Ru(3,3′-XX-2,2′-bpy)] 2+ , where X is CH 2 OH, COOH, COOCH 3 , COOC 2 H 5 , and COOCH 2 C 6 H 5 and bpy and dmb are 2,2′-bipyridine and 4,4′-dimethyl-2,2′-bipyridine, respectively, have been synthesized. [Ru(bpy) 2 ((COOCH 3 ) 2 bpy)](PF 6 ) 2 ·2CH 3 CN crystallized in the monoclinic space group P 2 1 / c with a =15.347 (3), b =22.767 (4), c =12.971 (3) A, and Z =4. 1 H-NMR spectra were assigned. The proton on the carbon atom neighboring the nitrogen coordination site shifts upfield upon coordination to ruthenium(II). Electronic absorptions occur over the visible region from 550 to 400 nm, which are attributed to metal-to-ligand charge transfer and in the UV region from 250 to 350 nm, which are associated with intraligand processes. The absorbance in the visible region of the spectrum displays two components, Ru(dπ)→π*(bpy) and Ru(dπ)→π*((COOR) 2 bpy) for R=CH 3 , C 2 H 5 and CH 2 C 6 H 5 , in the other cases the Ru(dπ)→π* transitions to the three bipyridine ligands overlap. Reduction potentials attributed to the Ru(III/II) couple range from 1.22 V for the CH 2 OH derivative to 1.40 V versus SSCE for the COOC 2 H 5 derivative. Reductions attributed to the first reduction of the coordinated (3,3′-XX-2,2′-bpy) ligand occur over the range −0.88 to −1.36 V versus SSCE. Emission maxima at room temperature in acetonitrile range from 614 nm for the CH 2 OH derivative to 711 nm for the ester derivatives; their emission lifetimes at room temperature in acetonitrile vary from 940 to 258 ns, respectively. |
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