Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain.
Angew Chem Int Ed Engl. 2021 Apr 6;60(15):8095-8103. doi: 10.1002/anie.202014780. Epub 2021 Feb 19.
Photochemical electrocyclization of poly(phenylacetylene)s (PPAs) is used for the structural elucidation of a polyene backbone. This method not only allows classification of PPAs in cis-cisoidal (ω <90°) or cis-transoidal structures (ω >90°), but also approximating ω . A PPA solution is illuminated with visible light and monitoring the photochemical electrocyclization of the PPA helix by measuring the ECD spectra at different times. PPAs with a cis-cisoidal structure show a reduction of the ECD signal of at least 50 % before 30 min of irradiation, while cis-transoidal helices need much longer time because the transoidal bond must be isomerized. The different cis-cisoidal and cis-transoidal helices require different times to decrease their ECD signal by 50 % (t ), depending on the degree of compression or stretching of the helix, establishing a relationship between the secondary structure adopted by PPA (ω ) and the time required to lose the ECD vinylic signal by light irradiation.
聚乙炔（PPAs）的光化学电环化用于聚烯主链的结构阐明。该方法不仅可以将 PPAs 分类为顺式顺式（ω <90°）或顺式反式结构（ω >90°），还可以近似ω。将 PPA 溶液用可见光照射，并通过在不同时间测量 ECD 光谱来监测 PPA 螺旋的光化学电环化。在照射 30 分钟之前，具有顺式顺式结构的 PPAs 的 ECD 信号至少降低 50％，而顺式反式螺旋需要更长的时间，因为反式键必须异构化。不同的顺式顺式和顺式反式螺旋需要不同的时间来降低其 ECD 信号的 50％（t），这取决于螺旋的压缩或拉伸程度，从而建立了 PPA 所采用的二级结构（ω）与通过光照失去 ECD 乙烯基信号所需的时间之间的关系。
