Vermellogens and the Development of CB[8]-Based Supramolecular Switches Using pH-Responsive and Non-Toxic Viologen Analogues

[Abstract] We present herein the “vermellogens”, a new class of pH-responsive viologen analogues, which replace the direct linking between para-substituted pyridinium moieties within those by a hydrazone functional group. A series of such compounds have been efficiently synthesized in aqueous media by hydrazone exchange reactions, displaying a marked pH-responsivity. Furthermore, the parent N,N′-dimethylated “vermellogen”: the “red thread”, an analogue of the herbicide paraquat and used herein as a representative model of the series, showed anion-recognition abilities, non-reversible electrochemical behavior, and non-toxicity of the modified bis-pyridinium core. The host–guest chemistry for the “red thread” with the CB[7,8] macrocyclic receptors has been extensively studied experimentally and by dispersion corrected density functional theory methods, showing a parallel behavior to that previously described for the herbicide but, crucially, swapping the well-known redox reactive capabilities of the viologen-based inclusion complexes by acid–base supramolecular responsiveness.This work is supported by Grants PID2019-105272GB-I00 and CTQ2017-89166-R funded by MCIN/AEI/10.13039/501100011033 and the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39 and 508/2020). A.B.-G., I.N., and R.S. thank, respectively, Xunta de Galicia (ED481B-2021-099), the MECD (FPU program), and Erasmus+ program for financial support. We are very grateful for helpful discussions with Professors Hao Li (Zhejiang University), Patrice Woisel (Université de Lille) and José Luis Barriada (Universidade da Coruña). We also acknowledge the use of RIAIDT-USC analytical facilities, and CESGA (Xunta de Galicia) for computational time.Xunta de Galicia; ED431C 2018/39Xunta de Galicia; ED431C 508/2020Xunta de Galicia; ED481B-2021-09

Tuning structural isomers of phenylenediammonium to afford efficient and stable perovskite solar cells and modules

Salt passivation of perovskite often results in formation of 2D perovskite layers, which impaired charge transport behaviour. Here, the authors study the energy barrier of 2D perovskite formation upon passivation by different iodide salt, and provide insight how to manipulate this to maximise device performance.Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI(2)) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 h). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm(2) was achieved