Spiro-Conjugation Of Diarylethene Derivatives And Resulting Properties Regulation

Light is a non-invasive external stimulus,which can be used to alter the molecular conformation and electronic structure characteristics.Photochromic materials have attracted much attention in the field of molecular switches and optoelectronic devices because they can undergo reversible configuration isomerization under the light stimulation.Among them,diarylethene are one of the most representative photochromic materials.Upon exposure to specific wavelength light,diarylethene will undergo intramolecular electrocyclization reaction.The reaction process mainly involves the reconstruction of chemical bonds in the light-excited state,but now it is still challenging to regulate the chemical reaction under the light-excitation.Therefore,the structural design of the novel diarylethene molecule is also crucial to optimize the performance of photoisomerization reaction.It is worth noting that spiro compounds have attracted much attention due to their unique steric hindrance and electronic structure effects.Currently,the spiro-conjugated?system has been widely used to disigned novel organic photoelectric functional molecules.However,the influence of the spatial electronic effect on the photoisomerization of diarylethylene is less studied.In this work,we intend to explore the design,synthesize and performance of spiro-diarylethylene molecule.The main contents of this article are as follows:(1)We designed and synthesized two novel diarylethylene molecules(SFI-Th/SFI-Sul),which are based on spiro[fluorene-9,1'-indene](SFI)as the central ethene bridge.X-ray crystal structure indicate that spiro structure influnced their three-dimensional electronic configuration.At the same time,the hydrogen atom(H~a)in the heterocyclic aromatic hydrocarbon is shielded by the s pirofluorene unit,showing an independent single peak in ~1H Nuclear Magnetic Resonance Spectra.(2)Based on the photochemical reaction of compound SFI-Th/SFI-Sul,We have explored the effects of steric hindrance and electronic structure on the photoisomerization reaction.The experimental results showed that SFI-Th displays good photochromic properties,while SFI-Sul exhibits higher photocyclization quantum yield and lower photocycloreversion quantum yield,both of which are good photochromic materials.What's more,SFI-Sul's ring-closing reaction process exhibits light-up fluorescence emission.Detailed experimental and theoretical results reveal that the electron effect of the spiro-conjugation plays a role in regulating the energy attenuation mode of the excited state.This research can provide new insights for the application of spiro-conjugation in photochromic functional materials.(3)Boron atom was introduced into the spiro-conjugated diarylethylene system,we designed and synthesized a spiro-diarylethylene functional molecule(SOB-DE),whose photoisomerization reaction is driven by visible light.The molecule exhibits high thermal stability and good photochromic properties without using ultraviolet light.We have further expanded the spiro-conjugated diarylethylene family by boron-doping,making it widely applicable in the fields of optoelectronic materials,bioimaging and photopharmacology.