Kinetic Characteristic Of Photoisomerization For A Ruthenium Complex

Ruthenium complex, are among the most investigated in fields that include solar energy conversion, photocatalysis, nonlinear optical materials, electrochemical, electron transfer and molecular recognition etc., owing to their favorable photophysical and photochemical properties as well as ground state and excited state reactivity. The photo-induced isomerization reaction of ruthenium complex changes in a variety of forms, and the reaction mechanism is complicated. Molecular materials based on isomerization have potential application value in optoelectronic and photonic devices technology. The study for photo isomerization is of great significance for the light energy conversion, information storage, as well as the design for "molecular switch" and "molecular motor",In this degree thesis, two geometric isomer of one kind of nitrosylruthenium complex were successfully synthesized and isolated, and the reaction kinetic was studied at different wavelengths, rate constant and quantum yields for reaction was calculated. Furthermore, the molecular orbital and spectral characteristics of two isomers were calculated and analyzed, which provides an important basis to investigate the mechanism for the photo isomerization.The main works of this thesis are as follows:First, the significant characteristic and progress of photo-induced isomerization reaction of ruthenium compounds were introduced and analyzed.Secondly, two geometric isomer of one kind of nitrosylruthenium complex were successfully synthesized and isolated, their structure was determined using high resolution nuclear magnetic resonance spectra. Ultraviolet-visible absorption spectra of the two isomers, cis-1and cis-2, in DMSO solution was determinated, and it showed that the visible absorption peak is at410nm and420nm, respectively, which provides an experimental basis for studying molecular orbital and excited energy level of these complex.Thirdly, photo isomerization from cis-2[Ru(OAc)(2CQN)2NO] to cis-1[Ru(OAc)(2CQN)2NO] was monitored using600M’H NMR spectrum. Three wavelengths:420nm,475nm and550nm, were selected to study the kinetic process of the isomerization. From the evolution of1H NMR spectrum vs time, the rate constant (k) for the reaction from cis-2isomer to cis-1isomer was calculated. The k is0.00712(min-1),0.00557(min-1) and0.00493(min-1), respectively; and the quantum yields of reaction are φ1=4.145×10-3,φ2=3.018×10-3and φ3=1.985×10-3, respectively. Experimental results showed that the rate constant is maximal with the photoirradiation near to the absorption peak.Last, molecule orbital, electronic absorption spectroscopy, infrared spectroscopy and1H NMR of two isomers were calculated, using density functional theory (DFT) methods, at B3LYP/Lanl2dz+6311++g**level. The calculation values of electronic spectrum, molecular vibration frequency, and chemical shift of H atomic spin coupling are in consistent with those from experimental measurements. The calculation provided a reasonable explanation for the molecular orbital, electron transitions and molecular vibrational modes, and provided important information to explore the reaction mechanism of photo isomerization.