Doane Tennyson, Cheng Yu, Sodhi Nipun, Burda Clemens
Center for Chemical Dynamics, Department of Chemistry, Case Western Reserve University , Cleveland, Ohio 44106, United States.
J Phys Chem A. 2014 Nov 13;118(45):10587-95. doi: 10.1021/jp505656e. Epub 2014 Sep 4.
The use of light-triggered photolysis provides a powerful tool for unique syntheses and for applications that require remote operation such as drug delivery or molecular switches. Here, we describe the photochemistry of a recently developed alkylsilicon phthalocyanine Pc 227, which undergoes an exchange of the alkyl ligand for a ligand derived from the solvent when the axial Si-C bond is photolyzed in a solvent with low-energy visible light. In this work with methanol as the solvent, we investigate the formation of the methoxy analogue of the therapeutic drug Pc 4, (termed Pc 233) upon irradiation. Using steady-state spectroscopy and characterization of the photoproducts, the competing pathways between direct ligand exchange on the central silicon atom and delocalization of the radical produced by homolysis on the phthalocyanine ring is observed. The delocalized radical intermediate is quite long-lived. At long times this intermediate decomposes without significant formation of Pc 233. The results of this investigation provide insights into recent work utilizing Pc 227 for drug delivery applications and for future work on the use of phthalocyanines as long-wavelength phototriggers.
光触发光解的应用为独特的合成方法以及诸如药物递送或分子开关等需要远程操作的应用提供了一个强大的工具。在此，我们描述了一种最近开发的烷基硅酞菁Pc 227的光化学性质，当轴向Si-C键在低能量可见光的溶剂中发生光解时，其烷基配体可与来自溶剂的配体发生交换。在以甲醇为溶剂的这项工作中，我们研究了辐照后治疗药物Pc 4的甲氧基类似物（称为Pc 233）的形成。通过稳态光谱和光产物的表征，观察到了中心硅原子上直接配体交换与酞菁环上均裂产生的自由基离域之间的竞争途径。离域自由基中间体寿命相当长。长时间后，该中间体分解，没有大量形成Pc 233。这项研究结果为近期利用Pc 227进行药物递送应用的工作以及未来将酞菁用作长波长光触发器的工作提供了见解。
