Synthesis And Properties Of A Novel Photochromic Silver Complex With Diarylethene

Dithienylethene is recognized as the most likely practical optical storage material because of the excellent photochromic properties,characteristic thermal stability,sensitive response and good fatigue resistance.From the perspective of crystal engineering,when the metal ions are coordinated to photochromic compounds,the interactions between metal ions can be photoexcited by the bridgeding dithienylethene.While maintaining the original photochromic properties,complexes can also possess new photophysical and photochemical properties due to the introduction of metal ions and the resulted coordinated structural features.Therefore,construction of photochromic metal complexes is one of the effective strategies to construct multifunctional photochromic materials.In this paper,a photochromic dithienylethene containning cyano groups,i.e.1,2-bis-[2'-methy-5'-(4"-cyanophenyl)-3'-thiehyl]perfluorocyolopentene(BM-4-CP-3-TP)was designed,synthesized and used as ligand to reacted with AgCF3COO to synthesize a new complex single crystal by diffusion method.The structures of BM-4-CP-3-TP and its complex were characterized by Infrared Spectra,Mass Spectrometry and Nuclear Magnetic Resonance,and X-ray single crystal diffraction.Their photochromic properties and fatigue resistances were studied in silicon gel plate,solution and PMMA films,respectively,by UV-Vis spectrometry.The guest desorption and re-adsorption properties were analyzed by nuclear magnetic resonance.The photochromic properties of guest-free complex before and after the photo-isomerization were investigated by UV-Vis spectrometry.The main conclusions are concluded as follows:(1)With 2-methyl thiophene as starting materials,the single crystal of BM-4-CP-3-TP was synthesized successfully by bromination with NBS and suzuki-coupling reaction.X-ray single crystal diffraction showed that the crystal is a new structure with monoclinic system and its reactive carbon distance is 3.6509A.The dihedral angle of two thiophene rings is 58.861?reflecting an anti-parallel conformation.(2)X-ray single crystal diffraction analysis show that the complex is a novel 2D planar with benzene filled in the channel fromed between planes.In a unit cell,there are two crystallographically independent Ag centers forming[N101]linear configuration and[N103]tetrahedron,respectively.The distance between reactive carbons is 3.5909A and the dihedral angle of two thiophene rings is 61.230° showing anti-parallel conformation.(3)The UV-vis spectra show that BM-4-CP-3-TP and its complex occured reversible photochromic properties both in TLC,solution and PMMA films.The maximum absorption wavelength of the respective closed-form is 605nm no matter what the situation.(4)The nuclear magnetic resonance of complex show that the guest benzene could be liberated by heating complex to 190? and the benzene could be recovered by exposing complex to benzene vapor at 50? for 24 hours.This complex is the first example of photochromic complex possessing reversible guest desorption and re-adsorption properties.(5)The photo-isomerization of guest-free complex remains unchanged.This complex represents the fist dithienylethene complex with reversible photochromic properties after liberation of guest.