Construction And Photochromic Performance Research Of Naphthalene Diimide Based Electron Donor-acceptor Systems

Photochromic materials composed of electron donor-acceptor units possess excellent naked-eye detectable performance,which exhibit high potential and practical applications in a range of sensors,displays,data storage,energy conversion and so forth.In order to successfully construct electron donor-acceptor systems with excellent photochromic properties,two matching rules of electron donating-accepting abilities and the interfacial relationship(the position relationship)between the potential electron donors and acceptors should be explored in depth.Up to now,scientists at home and abroad have reached a basic agreement on the matching of electron donating-accepting abilities of electron donors/acceptors,namely“strong-strong matching”and“weak-weak matching”.Although the interfacial relationship matching of electron donors/acceptors plays an important role in photoinduced intermolecular electron transfer(ET)and photochromism,the research is still in its infancy.Therefore,rational regulation of interfacial relationship between electron donors and acceptors have been the key scientific issues to be addressed for optimizing the properties of photochromic materials.Naphthalene diimides(NDIs)possess a large positivequadrupole moment,good modifiable properties and high redox activity,and it is a class of aromatic compounds,which can be used to construct excellent photochromic materials.The NDIs electron-deficient acceptors have low?-electron density,which are easy to interact with electron-rich donors forming flexible and diverse intermolecular ET channels through different weak interactions(lone pair-?,?-?and C-H···?interactions).Meanwhile,the pyridine groups at both ends of the dipyridyl naphthalene diimide(DPNDI)can coordinate with different types of metals,which can regulate the interfacial relationship between electron donors and acceptors to a certain extent.Based on above consideration,11 examples of 3-DPNDI based photochromic compounds 3-DPNDI(1),[3-DPNDI]·2DMF(2),[3-DPNDI]·2NMP(3),[3-DPNDI]·4DMSO(4),[Cd(3-DPNDI)(o-BDC)](5),[Cd(3-DPNDI)₂(p-BDC)(NO₃)](6),[Cd(3-DPNDI)(NDC)(H₂O)₂](7),[Cd(3-DPNDI)(BPC)(H₂O)](8),[Cd(3-DPNDI)(m-BDC)]·H₂O(9),[Co(3-DPNDI)(m-BDC)](10)and[Zn(3-DPNDI)_0.5(m-BDC)(H₂O)]·2H₂O(11),bytheassemblyof N,N?-di(3-pyridyl)-1,4,5,8-naphthalene diimide(3-DPNDI)as the electron acceptors and different types of electron-rich donors(electron-rich solvent molecules/aromatic carboxylic acids)at room temperature solvent diffusion/solvothermal conditions.In order to realize the effective regulation of photo-induced intermolecular ET and photochromism,the effects of electron rich solvents,auxiliary ligands and different types of metal on the interfacial relationship of electron donors/acceptors were systematically analyzed.The relationship of the composition,structure and photochromism of 3-DPNDI based electron donor-acceptor systems was preliminarily established.The main results of this thesis are as follows:(1)Three solvates 2-4 were prepared by introducing electron-rich solvents(DMF/NMP/DMSO)of different size,shape and charge density into 3-DPNDI(1)crystal lattices.Different electron-rich solvent molecules and 3-DPNDI through lone pair-?interactions give rise to different supramolecular frameworks of 2-4,and further lead to the different intermolecular ET and photochromic properties,which is mainly due to the delicate modulating effect of the different electron-rich solvent molecules on the interfacial contacts of electron donors/acceptors.(2)Four different frameworks of 3-DPNDI based coordination polymers 5-8 were constructed from the assembly of 3-DPNDI and auxiliary ligands with different size,shapes and charge density through coordination of cadmium,which show unique photochromic properties with discriminative photoresponsive rate and coloration contrast.This shows that the types of auxiliary ligands play an important role in regulating the interfacial relationship between electron donors and acceptors.(3)Three examples of 3-DPNDI based coordination polymers 9-11 were prepared by assembling 3-DPNDI,isophthalic acid and metals with different coordination modes,which show that the disctint electronegativity and coordination modes of metal ions can affect crystal structure stacking and interfacial relationship of the electron donors/acceptor to a certain extent,which can exert an effective modulating effect on the photoinduced intermolecular ET and photochromic properties.