Design,Synthesis And Photochemical Properties Study Of Donor-acceptor Type Inorganic-organic Hybrid Materials

Donor-acceptor type inorganic-organic hybrid crystalline materials have received extensive attention of researchers for their high research value and widely potential application in photo sensitive devices.The exploitation of these kinds of compound become a focal point of research in the field of inorganic optical functional materials,including the photochromic,thermochromic and photochromic-fluorescent effect induced by electron transfer reaction between the structural groups,the facile possesses of synthesising crystalline phase materials,the good thermotolerance and responsive character.In this thesis,the rational design of crystalline structure and the modulation of photo sensitivity and performance of luminescence are realized by the combination of electron donor/acceptor and luminophore.This text effectively expand structural diversity of photochromic materials,thermochromic materials and photochromic-fluorescent materials,and improve the application of these materials.Using electron deficiency viologen species as electron acceptor,benzenecarboxylic acid as electron donor and luminescence centre,series of photosensitive and thermosensitive hybrid crystalline materials have been synthesized.Photochemical properties,the effect on the photochromic rate with respect to the distance of electron transfer path,structure of viologen and framework and the design principle of photochromic-fluorescent material have been discussed.By the investigation of the specific research,results obtained are as follows:1.Using BTEC?1,2,4,5-benzenetetracarboxylic acid?as electron donor,PV²⁺?phenyl viologen?as electron acceptor,and by introducing PV²⁺ into a closly packed structure under solvothermal condition,a metal-organic framework [Zn₃?BTEC?₂·H₂O]·?PV?·H₂O with multi-site electron transfer character has been constructed,which possesses photochromism and thermochromism bifunctionality.Structural analysis of the single crystal before and after color change indicate that the distance between nitrogen-oxygen of the donor/acceptor motif is responsible for the reversible photochromism and irreversible thermochromism.Related discusses provided idea to further improve the performance of these kinds of material and design novel material,and at the same time clarified the structure-function-relationship of electron transfer type of hybrid materials.2.By insertting PV²⁺ into a two-dimension metal-organic framework,a photochromic super molecular [Zn₃?m-BDC?₄]·?PV?·H₂O?m-BDC: benzene-1,3-dicarboxylic acid?,responsing to both ultraviolet and visible light,has been synthesized.Using p-CPBPY,with good light sensitivity,as electron acceptor and BTC?1,3,5-benzenetricarboxylic acid?as electron donor,a selectively UV-induced photochromic compound [Zn?p-CPBPY?·?HBTC?] with two-fold penetrated structure has been constructed.Structure analysis and physical-chemical characterization results of these two complexes show that the electron deficience of viologen,the stablility of viologen radical and the reasonable arrangement of the crystal structure are the main reasons of their rapid photo response capability.The study of the structure provides the way to modulate photochromic property,design and synthesis of photosensitive crystalline materials with narrow-band absorption band.3.A three-dimensional motif Zn-MOF constructed by BTC and zinc ion has an electronagative porous framework.With introducing MV²⁺ cation into the channel equilibrium charge,it constructs a photochromic compound [MV][Zn₃?BTEC?₂?H₂O?₂]·H₂O.Before irradiation,the original crystal emits strong pale beige luminescent,with a main emission peak at 534 nm and a shoulder peak at 476 nm.After coloration,the ultraviolet spectra and fluorescence spectra are partialy overlaped.Energy transfer between the photoactive molecules modulate the emission intensity.And the intensity at 534 nm decline more obviously,which results blue shift of the fluorescence spectrum.Finally,the pale beige emission color of the crystal changes into dark green.This compound may find potential application at no-distructive storage and fluorescence switch.4.Under solvothermal condition,the connection between BTEC and p-CPBPY and zinc ions forms a three-dimensional framework [Zn2?BTEC??p-CPBPY??H₂O?2]·4H₂O with two-fold penetrated motif.This structure possesses photochromic ability.It is worth noting that stable water radicals have been produced accompany with the electron transfer process.In situ single crystal structural analysis,ESR and IR variation after photochromism indicate the existence of water radical.It is known that water radical is a highly oxidized specie which is e xtremely unstable with lifetime of only 200 fs.The generation of water radical in viologen compound possess the possibility in photocatalytic degradation of polluctant.Different from traditional semiconductor catalyst,the mechanism of the catalyst is derived from photoinduced charge separation.This research result may provide experimental data and possibility for developing novel viologen-based photocatalyst.