Molecular design and structural characterization of photoresponsive azobenzene-based polyamide units
Molecular design and structural characterization of photoresponsive azobenzene-based polyamide units
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DOI：
10.1016/j.dyepig.2020.108501
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发表时间：
2020-09-01
影响因子：
4.5
通讯作者：
Matczyszyn, Katarzyna
中科院分区：
文献类型：
--
作者：
Dudek, Marta;Pokladek, Ziemowit;Matczyszyn, Katarzyna
虽然偶氮苯(ABS)作为分子开关在生物和材料科学中的应用引起了人们的极大兴趣，但从实验和理论水平上确定的它们的光物理性质仍然需要系统的合理化。本文从几何取代(间位)和取代基效应的性质(即给电子基，EDG或吸电子基，EWGs)的角度对某些AB衍生物的性质进行了(重新)评价。对它们的光物理性质、热稳定性和在还原环境中的功能的综合实验研究结果通过密度泛函理论计算得到了合理的结果。由于所研究的ABS的反式(E)和顺式(Z)异构体的n-pi*带重叠，很难获得高的顺式到反式的转化率，但我们已经证明，通过控制取代基的位置，可以将光静止状态(PSS)的顺式异构体的含量提高到30%。此外，我们还发现-NHCO-基团的存在有助于降低偶氮基团的有效键级，从而降低了转化能垒的高度，并缩短了顺式异构体的半衰期。最后发现，缺电子ABS在还原环境下更稳定。
Although there is much interest in the use of azobenzenes (ABs) as molecular switches for biological and material science applications, there is still need for systematic rationalization of their photophysical properties determined at both experimental and theoretical level. We present here the (re-) evaluation of the properties of some AB derivatives in the context of their geometrical substitution (para or meta) and nature of substituent effects (i.e. electron-donating groups, EDGs or electron-withdrawing groups, EWGs). Results of comprehensive experimental studies of their photophysical properties, thermal stabilities and functioning in reducing environments are rationalized by DFT calculations. As the associated n-pi* bands of the trans (E) and cis (Z) isomers of the studied ABs overlap, it is difficult to obtain high cis-to-trans conversion, however we have proved that by manipulation of the substituents position, the content of the cis isomer at the photostationary state (PSS) could be enhanced up to 30%. Moreover, we show that the presence of -NHCO- group at para positions contributes to reducing the effective bond order of the azo group resulting in the reduction of the height of the energy barrier for conversion and reduces the half-life of the cis isomer. Finally, electron deficient ABs are found to be more stable under reducing environments.