Modulation of the carboxamidine redox potential through photoinduced spiropyran or fulgimide isomerisation,Photochemical & Photobiological Sciences

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Modulation of the carboxamidine redox potential through photoinduced spiropyran or fulgimide isomerisation
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2018-03-12 , DOI: 10.1039/c7pp00347a
M. Crawford Andrews _{1,

2,

3,

4} , Ping Peng _{1,

2,

3,

4} , Amit Rajput _{1,

2,

3,

4} , Anthony F. Cozzolino _{1,

2,

3,

4}

Affiliation

Carboxamidines functionalized with either a spiropyran or fulgimide photoswitch were prepared on multigram scales. The thermal, electrochemical, and photochemical ring isomerizations of these compounds were studied and the results compared with related systems. The photochemical isomerisations were found to be reversible and could be followed by ¹H NMR and UV-vis spectroscopy. The spiropyran/merocyanine couple was thermally active and an activation enthalpy of 116 kJ mol⁻¹ was measured for ring-opening. These measurements yielded an enthalpy difference of 25 kJ mol⁻¹ between the open and closed states which is consistent with DFT calculations. DFT calculations predicted a charge transfer to the carboxamidine group upon ring closure in the fulgimide and a charge transfer from the carboxamidine group upon switching the spiropyran to the merocyanine form. This was confirmed experimentally by monitoring the change in the oxidation potential assigned to the carboxamidine group. The potential of these molecules to therefore act as a new class of photoresponsive ligands that can modulate the ligand field of a complex is discussed.

中文翻译：

通过光诱导的螺吡喃或灭酰亚胺异构化对羧am氧化还原电位的调节

以数克规模制备用螺吡喃或or灭酰亚胺光敏开关官能化的羧s。对这些化合物的热，电化学和光化学环异构化进行了研究，并将结果与相关系统进行了比较。发现光化学异构化是可逆的，并且可以随后进行¹ H NMR和UV-可见光谱。螺吡喃/花菁对是热活性的，开环的活化焓为116 kJ mol ^-1。这些测量产生的焓差为25 kJ mol ^-1在打开状态和关闭状态之间，这与DFT计算一致。DFT计算预测，当在ful灭酰亚胺中闭环时，电荷转移至羧am基团，而在将螺吡喃转变为部花青形式时，从羧am基团转移电荷。通过监测分配给羧am基团的氧化电位的变化，通过实验证实了这一点。因此，讨论了这些分子作为新型光响应配体的潜能，这些配体可以调节复合物的配体场。

更新日期：2018-04-18

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