Multifunctional Viologen-Derived Supramolecular Network with Photo/Vapochromic and Proton Conduction Properties

Abstract

A supramolecular network [H4bdcbpy(NO3)2·H2O] (H4bdcbpy = 1,1′-Bis(3,5-dicarboxybenzyl)-4,4′-bipyridinium) (1) was prepared by a zwitterionic viologen carboxylate ligand in hydrothermal synthesis conditions. The as-synthesized (1) has been well characterized by means of single-crystal/powder X-ray diffraction, elemental analysis, thermogravimetric analysis and infrared and UV-vis spectroscopy. This compound possesses a three-dimensional supramolecular structure, formed by the hydrogen bond and π–π interaction between the organic ligands. This compound shows photochromic properties under UV light, as well as vapochromic behavior upon exposure to volatile amines and ammonia, in which the electron transfer from electron-rich parts to the electron-deficient viologen unit gives rise to colored radicals. Moreover, the intensive intermolecular H-bonding networks in 1 endows it with a proton conductivity of 1.06 × 10−3 S cm−1 in water at 90 °C.

Recent progress in polyoxometalate–viologen photochromic hybrids: structural design, photochromic mechanism, and applications

“…Nowadays POM-viologen hybrid crystalline photochromic materials combining multiple color-changing capabilities and exploring multifunction applications have become a research hotspot. [98][99][100][101][102][103] For example, Guo et al successfully prepared a new two-dimensional hybrid material EV[Mo 9 O 28 ] (EV 2+ = ethyl viologen cation) by introducing the ethyl viologen, a wellknown electron acceptor, into the polyoxomolybdate layered structure. 98 As shown in Fig.…”

One-Dimensional Chain Viologen-Based Lanthanide Multistimulus-Responsive Materials with Photochromism, Photoluminescence, Photomagnetism, and Ammonia/Amine Vapor Sensing

“…In consideration of the intrinsic electron-deficient viologen complexes, which normally respond actively to inorganic ammonia/organic amines that are rich in electrons. ,,,− As expected, 1-Dy displayed distinctly different color responses under different ammonia/amine vapor atmospheres in the presence of inorganic ammonia: NH 3 , hydrazine hydrate (N 2 H 4 ·H 2 O), primary amine: ethylamine (EA), ethylenediamine (EDA), and secondary amine: diethylamine (DEA), exhibiting cyan, light-green, navy blue, dark blue, and yellow (Figure a), respectively. This reflects the discrimination on the primary amines and secondary amines, while neither tertiary amine: triethylamine (TEA) vapor nor the TEA aqueous solutions make 1-Dy change color.…”

“…It is also worth noting that after a long continuous fumigation period of about 30 min under an ammonia/amine vapor atmosphere except DEA and TEA, all colored samples eventually turn black, and this process is accompanied by crystal phase collapse, which is irreversible damage. Moreover, the UV–vis spectrum of all black samples showed that they absorb almost completely in the visible region (Figure S19), which is in accord with some viologen amine vapor response substances. , …”

“…Moreover, the UV−vis spectrum of all black samples showed that they absorb almost completely in the visible region (Figure S19), which is in accord with some viologen amine vapor response substances. 59,65 After exposure to different ammonia/amine vapors, the UV−vis spectra showed a gradual broadening of the absorption band in the 450−800 nm range assigned to the viologen free radical (Figure 6b). 29 The ESR spectrum of colored samples showed significant signal responses at g = 2.004, respectively, which are indicative of the generation of free radicals in 1-Dy.…”

Proton–electron-coupled functionalities of conductivity, magnetism, and optical properties in molecular crystals

“…[94][95][96][97][98][99][100][101][102] Although many vapochromic materials bearing H-bonds have been reported to date, they have also been understood merely by structural changes. 62,63,[103][104][105][106][107][108][109][110][111][112][113][114][115][116] The mechanisms reported thus far have only considered the electronic states of an isolated complex, ignoring intermolecular interactions. Thus, to the best of our knowledge, there have been no reports on vapochromism based only on proton-electron coupling in the solid state.…”