Photochemistry of selected blebbistatin derivatives and arylphosphirane derivatives

Abstract

In previous study, it was demonstrated that blebbistatin can release hydroxyl radicals under one-photon blue light or two-photon near-infrared light excitation, indicating that blebbistatin derivatives may be able to deliver molecules of interest with temporal and spatial control. However, the mechanism of photocleavage of blebbistatin derivatives remains unclear, which hindered further development of blebbistatin derivatives as photoremovable protecting groups (PPGs) for various applications. In this thesis, five blebbistatin derivatives with different leaving groups were synthesized and studied. With combined methods, including femtosecond transient absorption spectroscopy, density functional theory calculation, hydroxyl radicals detection and photoproducts analysis, photocleavage mechanism of blebbistatin derivatives and effect of leaving groups on the reaction pathways were revealed. Based on the study, a strategy for improving blebbistatin-derived PPGs was proposed. Arylphosphiranes is a kind of molecules with the formula ArPC2H4, containing a three-membered ring with a phosphorus atom. Since the three-membered rings are highly strained, arylphosphiranes tend to release ethylene under irradiation or heat. Generally, it was proposed that arylphosphinidenes will be generated after photocleavage of arylphosphiranes. In previous studies, intramolecular reactions were employed to trap the transient arylphosphinidene species. In 2005, triplet mesitylphosphinidene was first detected by nanosecond transient spectroscopic in cyclohexane at room temperature. However, singlet arylphosphinidene and early events after excitation of aryphosphiranes have not been observed and studied. In this thesis, two naphthylphosphirane derivatives were studied by transient spectroscopy, density functional theory calculation and photoproducts analysis. The photochemistry of arylphosphiranes were better understood and the resulted new knowledge may provide fundamental insight for further application development.