Synthesis And Photoelectric Properties Of Hybrid Metal Halides Based On 1-(2,3-Dihydroxypropyl)-4,4’-Bipyridine

Hybrid metal halides are a class of materials composed of organic cations and metal halide anions through intermolecular interactions.Due to the rich crystal structures and excellent photoelectric properties,hybrid metal halides have been the frontier materials in the field of optical and electrical materials in recent years.Usually,the structures and properties of the hybrid metal halides are adjusted by choosing different organic cations or inorganic anions.Among the most widely studied photochromic materials,electron deficient viologen cations can accept the single electron from electron donors to form viologen free radicals,so as to realize the reversible change of color.Therefore,they are widely used to construct photo/electric/thermo-chromic materials.Based on the above considerations,a pair of chiral viologen derivatives 1-(S/R-2,3-dihydroxy-propyl)-4,4’-bipyridinium chloride(S/R-L·Cl,L=C13H15N2O2)was designed and synthesized in this paper,which was constructed with different metal halides to obtain a series of zero-dimensional hybrid metal halides,and their photo/electric properties were studied.The details are listed as follows:1.A novel Indium-based metal halide hybrid(C13H16N2O2)2InCl6·Cl(1)has been obtained by integrating the mono-viologen derivative S-L·Cl with InCl3 by solvent volatilization.Compound 1 exhibits fast and reversible photochromic properties induced by UV and sunlight,as well as selective response to soft/hard X-rays.Under external light stimulation,electrons in compound 1 were rapidly transferred from the electron-rich[InCl6]3-octahedron to[HL]2+pyridine ring to generate viologen free radicals,which makes the crystal color change from light yellow to dark blue rapidly,and its light response time is only 0.1 s.In addition,it also shows reversible electrochromic properties.By applying the cyclic voltage,the color of the film of compound 1 can be rapidly switched between white and purplish red.The fast and reversible photo/electro-chromic response properties of compound 1 not only enrich the types of stimuli-responsive materials,but also provide the possibility for the application of metal halides in inkless erasable printing and smart devices.2.Using bismuth chloride and chiral viologen derivatives S/R-L·Cl,a pair of chiral bismuth-based hybrid metal halides,S-(C13H16N2O2)2Bi2Cl10(2)and R-(C13H16N2O2)2Bi2Cl10(3),were successfully obtained by solvent-layering method.Compounds 2 and 3 combine the advantages of chiral viologen cations and halide anions.They not only have reversible photochromic properties from white to light green and electrochromic properties from white to blue black,but also have obvious mirror symmetrical CD signals.By introducing chiral ligands to induce chirality in metal halides,making it possible to detect circularly polarized light with metal halides.3.A Cadmium-based hybrid metal halide(C13H16N2O2)CdCl4(4)was prepared by solvent volatilization with CdCl2 and viologen derivative S-L·Cl.Compound 4 also has reversible photochromic and electrochromic properties,with color changes from yellow to dark green and white to purple respectively,due to the electron transfer to produce viologen radical.In addition,compound 4 also has photoluminescence properties.Due to the partial overlap between UV absorption spectrum and fluorescence spectrum,electron transfers and energy transfers occur simultaneously.At the same time as photochromism,its fluorescence intensity decreases gradually.The reversible photo/electro-chromic response and light-modulated luminescence properties of compound 4 expand the application of hybrid metal halides in multiple detection and encryption materials.