Synthesis And Preparation Of Organic Conjugated Compounds And Organic/Inorganic Composites,and Their Electrochromic Properties

Oligothiophenes and their derivatives,viologens and their derivatives with optical and electrical properties can be used as active materials for organic electrochromic devices.Electrochromic devices have wide application prospects in smart windows,automotive and information field,et al.In this paper,the author have designed and synthesized a series of organic conjugated compounds,tri(4-(2?-thienyl))phenylamine(3TPA),1,1?-bis(ethyl)-4,4?-bipyridinium dihexafluorophosphate([BP2E]2+2PF6-),1,1?-bis(n-octyl)-4,4?-bipyridinium dihexafluorophosphate([BP2O]2+2PF6-),1,1?-bis(4-vinylbenzyl)-4,4?-bipyridinium dihexafluorophosphate([BP2VB]2+2PF6-),2,7-bis(4-pyridyl)fluorine(FR2P),2,7-bis((1-ethyl)-4-pyridinium)fluorine dihexafluorophosphate([FR2PE]2+2PF6-),2,7-bis(4-pyridyl)-9-fluorenone(FN2P)and 2,7-bis-((1-ethyl)-4-pyridinium)-9-fluorenone dihexafluorophosphate([FN2PE]2+2PF6-).Their chemical structures were characterized and confirmed by mass spectra(MS),nuclear magnetic resonance(NMR)and infrared spectrum(IR).Their molecular structures are shown as follows: The optical and electrical properties of all the organic conjugated compounds were investigated by UV-vis absorption spectra(UV-vis),fluorescence spectra(FL)and cyclic voltammetry(CV).The maximum absorption wavelength,edge wavelength,redox potentials and fluorescence emission wavelength were determined.The molar absorption coefficient,energy gap,HOMO/LUMO levels and fluorescence quantum efficiency were calculated.The results showed that the maximum absorption wavelength of conjugated compound films exhibited red shift relative to their solutions,and the fluorescence quantum efficiency of the viologen derivative containing fluorine group was higher than that of the viologen derivative containing fluorenone group.The organic/inorganic composite membrane(P3TPA/WO3)was prepared by vacuum evaporation and electrochemical polymerization.The electrochromic device was fabricated with the P3TPA/WO3 composite membrane as active material.The device structure was ITO/ active layer/electrolyte/Pt.P3TPA/WO3 composite film showed reversible,clear color change from yellow to gray-green on electrochemical doping and dedoping.Compared with WO3 film,the coloring and bleaching switching time of P3TPA/WO3 composite film decreased by 18.52% and 25.71% respectively,and the coloration efficiency increased from 43.45 cm2/C to 52.89 cm2/C.The electrochromic properties of [BP2E]2+2PF6-,[BP2O]2+2PF6-,[BP2VB]2+2PF6-,FR2 P,[FR2PE]2+2PF6-,FN2 P and [FN2PE]2+2PF6-were studied by UV-vis,CV and the cyclic test instrument of electrochromic.Reversible changes in color can be observed in both electrochemical doping and dedoping.Among them,[BP2E]2+2PF6-,[BP2O]2+2PF6-and [BP2VB]2+2PF6-exhibited reversible color change from colorless to blue.FR2 P and [FR2PE]2+2PF6-exhibited reversible color change from colorless to brown yellow.FN2 P and [FN2PE]2+2PF6-exhibited reversible color change from light yellow to gray.The introduction of the conjugated substituent to the viologen is beneficial to improve the optical contrast,the cycle life and the coloration efficiency,and reduce the loss of electricity,while the introduction of alkyl is beneficial to improve its optical contrast and coloration efficiency.Compared to [BP2E]2+2PF6-and [BP2O]2+2PF6-,the optical contrast of [BP2VB]2+2PF6-at 620 nm is increased by 5.49% and 5.54%,the cycle life is increased by 15.87% and 7.35%,the coloration efficiency is increased by 13.75% and 6.91%,and the loss rate of electricity is reduced by 3.60% and 2.10%,respectively.The optical contrast and coloration efficiency of viologen derivatives with fluorene and fluorenone groups are lower than those of the viologen,but the cycle stability is better than that of the viologen.Compared to FR2 P and FN2 P,the optical contrast of [FR2PE]2+2PF6-and [FN2PE]2+2PF6-at 600 nm is increased by 27.99% and 16.91%,the cycle life is increased by 3.60% and 1.65%,the coloration efficiency is increased by 23.89% and 14.03%,and the loss rate of electricity is reduced by 11.69% and 41.46%,respectively.