Tuning Excited State Isomerization Dynamics through Ground State Structural Changes in Analogous Ruthenium and Osmium Sulfoxide Complexes

摘要: The complexes [Ru(bpy)2(pyESO)](PF6)2 and [Os(bpy)2(pyESO)](PF6)2, in which bpy is 2,2'-bipyridine pyESO 2-((isopropylsulfinyl)ethyl)pyridine, were prepared studied by (1)H NMR, UV-visible ultrafast transient absorption spectroscopy, as well electrochemical methods. Crystals suitable for X-ray structural analysis grown [Ru(bpy)2(pyESO)](PF6)2. Cyclic voltammograms of both provide evidence S→O O→S isomerization these are described an ECEC (electrochemical-chemical electrochemical-chemical) mechanism follows Ru(2+) oxidation Ru(3+) reduction. S- O-bonded Ru(3+/2+) couples appear at 1.30 0.76 V versus Ag/AgCl propylene carbonate. For 0.97 0.32 V acetonitrile, respectively. Charge-transfer excitation results a significant change the spectrum. S-bonded isomer [Ru(bpy)2(pyESO)](2+) features lowest energy maximum 390 nm absorbs 480 nm. quantum yield was found to be 0.58 carbonate 0.86 dichloroethane solution. Femtosecond spectroscopic measurements collected complexes, revealing time constants isomerizations 81 ps (propylene carbonate) 47 ps (dichloroethane) [Ru(bpy)2(pyESO)](2+). These data model isomerizing complex presented. A striking conclusion from this that expansion chelate ring single methylene leads increase constant nearly two orders magnitude.