Synthesis And Properties Of A Novel Photochromic Diarylethene With 4-Cyanophenyl Groups

Photochromic compounds show reversible color,and structure changes as well as the photochemical and photophysical properties changes under the irradiation of light with defferent wavelengths.They have aroused intensive of study and been considered as one of the most promising application in optical information storage and molecular switches,due to their excellent thermal stability,high fatigue resistance and rapid response time.Thiophene is proved to possess the lowest aromatic stabilization energy;cyanophenyl shows a remarkable fluorescence signal when excited at a appropriate wavelength;diarylethene with Octafluorocyclopentene show good thermal stability and thermal fatigue resistance.So we has designed and synthesized a new type of bithienylethene photochromic molecule and two new thiophene benzylcyanide,2-bromo-3-methyl-5(4'-benzenenitile)thiophene and 3-bromo-2-methyl-5(3'-benzenenitrile)thiophene,were synthesized by C-C coupling of 2-bromo-3-methyl thiophene and 3-bromo-2-methyl thiophene,then a new thiophene benzylcyanide-diarylethene(1,2-bis-[2-methyl-5-(4'-cyanophenyl)-3-thienylperfluorocyclopentene),was synthesized by reation with octafluorocyclopentene.The 3,5-dibromo-2-methylthiophene was characterized by IR,BM-4-CPT was characterized by ~1HNMR and MS,the crystal structure of BM-3-CPT was characterized by X-ray crystallography and the BM-3-CP-3-TP was characterized by ~1HNMR.The BM-3-CP-3-TP was characterized by ~1HNMR and the photochromic properties and nondestructive read out of BM-3-CP-3-TP were investigated in silica gel plate,solutions and polymer films,respectively,by UV spectra and photoluminescence.And the changes in surface morphology from open-form to closed-form were investigated by laser scanning confocal microscopy and contact angle tester.The main conclusions are showed as follows:(1)The analysis of BM-3-CP-3-TP by UV-visible spectroscopy shows that it has excellent photochromic performance in silica plate,liquid phase and PMMA film.The maximum absorption wavelength of BM-3-CP-3-TP in hexane solution is 580 nm,appearring a red shift,which compare with the THFsolution.The maximum absorption of PMMA film at 580 nm exhibits a blue shift when compared with the THF solution.(2)The fluorescence spectrum analysis of BM-3-CP-3-TP shows that there is a small difference in fluorescence emission in low polar solution at open-form and closed-form under711 nm and 762 nm excitation,however,there is an obvious difference in PMMA film only under excitation with 762 nm light(3)The BM-3-CP-3-TP shows great thermal stability and fatigue resistance,which is valuable for the practical application.(4)The contact angle of BM-3-CP-3-TP film in open-form is 73.51°,indicating the hydrophilic surface.However,it changes to be 108.00° after irradiated with 254 nm light,indicating the hydrophobic surface.The surface morphology changes of BM-3-CP-3-TP from rough to smooth can be explained by the accumulated effect of the changes in molecular structure.