Molina-Osorio Andrés F, Yamamoto Sho, Robayo-Molina Iván, Gamero-Quijano Alonso, Nagatani Hirohisa, Scanlon Micheál D
The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL) Limerick V94 T9PX Ireland
Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University Kakuma Kanazawa 920-1192 Japan.
Chem Sci. 2021 Jul 1;12(30):10227-10232. doi: 10.1039/d0sc05786j. eCollection 2021 Aug 4.
Soft molecular assemblies that respond reversibly to external stimuli are attractive materials as on/off switches, in optoelectronic, memory and sensor technologies. In this Edge Article, we present the reversible structural rearrangement of a soft porphyrin membrane under an electrical potential stimulus in the absence of solid-state architectures. The free-floating porphyrin membrane lies at the interface between immiscible aqueous and organic electrolyte solutions and is formed through interfacial self-assembly of zinc(ii) -tetrakis(4-carboxyphenyl)porphyrins (ZnPor). A potential difference between the two immiscible electrolyte solutions induces the intercalation of bis(triphenylphosphoranylidene)ammonium cations from the organic electrolyte that exchange with protons in the porphyrin membrane. UV/vis absorbance spectroscopy shows that this ionic intercalation and exchange induces a structural interconversion of the individual porphyrin molecules in the membrane from an H- to a J-type molecular configuration. These structural rearrangements are reversible over 30 potential cycles. polarisation-modulation fluorescence spectroscopy further provides clear evidence of structural interconversion of the porphyrin membrane, as intercalation of the organic electrolyte cations significantly affects the latter's emissive properties. By adjusting the pH of the aqueous phase, additional control of the electrochemically reversible structural interconversion can be achieved, with total suppression at pH 3.
对外部刺激具有可逆响应的软分子组装体作为光电子、记忆和传感器技术中的开/关开关，是很有吸引力的材料。在这篇前沿文章中，我们展示了在没有固态结构的情况下，软卟啉膜在电势刺激下的可逆结构重排。自由漂浮的卟啉膜位于不混溶的水相和有机电解质溶液的界面处，由锌（II）-四（4-羧基苯基）卟啉（ZnPor）通过界面自组装形成。两种不混溶电解质溶液之间的电势差会诱导有机电解质中的双（三苯基磷亚基）铵阳离子插入，这些阳离子会与卟啉膜中的质子发生交换。紫外/可见吸收光谱表明，这种离子插入和交换会诱导膜中单个卟啉分子从H型分子构型向J型分子构型发生结构互变。这些结构重排在30个电势循环内是可逆的。偏振调制荧光光谱进一步为卟啉膜的结构互变提供了明确证据，因为有机电解质阳离子的插入会显著影响后者的发射特性。通过调节水相的pH值，可以实现对电化学可逆结构互变的额外控制，在pH值为3时完全抑制。
