Several 2- and 3-(phenylazo)pyridine derivatives were prepared. Most of their trans isomers have a large absorption band (∼2 × 104 M−1 cm−1 (1 M = 1 mol dm−3)) around 320 nm and a small absorption band (∼400 M−1 cm−1) around 450 nm. All of these compounds photoisomerize upon irradiation of the shorter (trans-to-cis) and longer (cis-to-trans) wavelength absorption bands. trans Isomers of 3-(phenylazo)pyridines axially coordinate more strongly to Zn–porphyrins than cis isomers, while the opposite is the case for 2-(phenylazo)pyridines, due to steric reasons. These phenylazopyridines quench the fluorescence of Zn–porphyrin upon coordination. These properties were exploited for the light-triggered fluorescence modulation of Zn–porphyrins. Light was irradiated to a mixed solution of phenylazopyridine and Zn–porphyrin to induce photoisomerization of the phenylazopyridine, which underwent association with, or dissociation from, the Zn–porphyrin, resulting in a decrease or increase of Zn–porphyrin fluorescence. For example, the fluorescence intensity of Zn–tetraphenylporphyrin reversibly changed by up to 50%, when 4-methoxy-2-(phenylazo)pyridine was employed.
制备了几种2-和3-(苯基偶氮)
吡啶衍生物。它们的大多数反式异构体在 320 nm 附近有一个大吸收带 (∼2 × 104 M−1 cm−1 (1 M = 1 mol dm−3)) 和一个小吸收带 (∼400 M−1 cm−1)约450纳米。所有这些化合物在较短(反式至顺式)和较长(顺式至反式)波长吸收带的照射下都会发生光致异构化。 3-(苯基偶氮)
吡啶的反式异构体比顺式异构体与
锌卟啉的轴向配位更强,而由于空间原因,2-(苯基偶氮)
吡啶的情况相反。这些苯基偶氮
吡啶在配位后会猝灭
锌卟啉的荧光。这些特性被用于
锌卟啉的光触发荧光调制。将光照射到苯基偶氮
吡啶和
锌卟啉的混合溶液中,引起苯基偶氮
吡啶的光异构化,其与
锌卟啉发生缔合或解离,导致
锌卟啉荧光的减弱或增强。例如,当使用 4-甲氧基-2-(苯基偶氮)
吡啶时,Zn-
四苯基卟啉的荧光强度可逆地改变高达 50%。