Planar Viologen-Based Crystalline Compounds Showing Heat-Induced Electron Transfer and Thermochromism

Abstract

Heat-induced electron transfer (ET) is desirable for some applications, such as thermal/photothermal catalysis, thermochromic antifake, and thermal control of molecular recognition, but needs to be avoided for photochromic or electrochromic windows and other devices. However, to date, the key structural factors of heat-induced ET for viologen compounds are still unclear. This work reveals that the planar structures of viologen moiety may be an important factor for heat-induced ET and thermochromism, through the summarization of a structural law from established thermochromic viologen compounds and the experimental verification using three known compounds with near-planar viologen moieties. Hence, this work contributes to enhance the probability of finding thermochromic viologen compounds with heat-induced electron transfer process.

Three Semiconductive 1D Naphthalene Diimide/Iodoplumbate Perovskites with High Moisture Tolerance and Long-Lived Charge Separation States

“…This value is comparable to the reported values for one-dimensional lead iodide perovskites. − The thermal conductivity behavior of hybrid 3 can be attributed to its infinite [Pb 2 I 6 2– ] n chains, two-dimensional organic networks, and the electron transfer from [Pb 2 I 6 2– ] n chains to organic networks . As shown in Figure S6, the intensity of free radical signal of hybrid 3 was also significantly enhanced after heating, indicating that thermoinduced electron transfer occurred in hybrid 3 , which has been reported in similar donor–acceptor hybrids. − The thermal switching of electrical conductivities of 3 could be cycled at least five times (Figure e). Meanwhile, PXRD confirmed the good agreement of the peaks in the diagrams of hybrid 3 after heating at 240 °C (Figure S9).…”

Four POM-Viologen Color-Changing Materials with Fast Color Response under Various External Stimuli

“…However, after heating, an obvious EPR signal ( g = 2.003) was observed. This result also proved that the thermochromic behavior of compounds 3 - 4 was related to the [1–cby] •+ and [1,1′–bcby] •+ radicals formed after heating …”

“…This result also proved that the thermochromic behavior of compounds 3-4 was related to the [1−cby] •+ and [1,1′−bcby] •+ radicals formed after heating. 44 For the sake of researching the electron transfer mechanism of compounds 3-4, we selected compound 4 as a representative example for XPS testing. The spectra of the C 1s, Co 2p, P 2p, and W 4f nuclear energy levels were nearly identical before and after heating, but the nuclear energy levels of N 1s and O 1s changed (Figure S17).…”

Three-Dimensional Viologen-Based Lanthanide–Organic Frameworks: Photochromism and Fluorescence Detection of Quinolone Antibiotics

“…Multifunctional stimulus-responsive materials are a category of materials that can change their color or properties in response to external stimuli and have attracted widespread attention owing to their wide application in smart windows, information storage, energy conversion, and inkless printing. − Viologen-functionalized complexes are typically multifunctional materials that can respond to external stimuli (such as UV light, X-rays, heat, and electropotential) and exhibit color changes discerned with the naked eye. − Nevertheless, as a branch of metal–organic frameworks (MOFs), viologen-based complexes are more widely studied for their photochromic properties due to their unique electron-deficient property, whereas the fluorescence sensing aspect is rarely studied. On the other hand, lanthanide MOFs (Ln-MOFs) for their unique luminescent properties (such as high quantum yield, long-lived emission, and large Stokes shifts) have been widely studied in the field of detection. − Up to now, some MOF materials for detecting antibiotics have been reported. ,,− However, the integration of photochromic and fluorescent probes to detect NORF and CIP in viologen-based Ln-MOFs has not been investigated. Thus, it is important to design and synthesize multifunctional viologen-based Ln-MOFs.…”