Multistate Switching of Some Ruthenium Alkynyl and Vinyl Spiropyran Complexes

To study the switching properties of photochromes, weundertookthe synthesis and characterization of several ruthenium organometalliccomplexes of the type [Ru(Cp*)(dppe)(C VC-SP)] or [Ru(CO)(dppe)(PPh3)Cl(CH UCH-SP)], where SP = spiropyran. The spectroscopicand electrochemical properties of the complexes were determined bycareful cyclic voltammetric and spectroelectrochemical experiments.Whereas the mononuclear alkynyl ruthenium complexes undergo one-electronoxidations localized over the metal alkynyl moiety, the oxidationof the mononuclear vinyl ruthenium complexes is centered on the indolinemoiety of the spiropyran. Through these studies, we demonstrate accessto several stable redox states, in addition to switching states attainedvia acidochromism and/or photoisomerization. Ruthenium alkynyl and alkenyl complexesdisplay a wide varietyof switching states when addressed electrochemically, photochemically,and chemically. The various isomeric forms were investigated by acombination of spectroscopic, spectroelectrochemical, and X-ray crystallographicstudies. We found that the alkynyl complexes exhibited more accessibleswitching states than the analogous vinyl complexes.