Synthesis And Properties Of Organic Photofunctional Materials Based On Carbazole Derivatives

Organic photofunctional materials had a wide range of applications in sensors,anti-counterfeiting,illumination and displays.Among them,carbazole derivatives were of great interest due to their excellent photophysical properties.Carbazole groups were often used as electron giving groups for the design of photofunctional materials.Therefore,it was of research significance to further modify carbazole based on its properties to design and prepare novel photofunctional materials.In this thesis,D-A-A type dual-acceptor small molecule stimuli-responsive luminescent materials ware firstly designed and synthesized using carbazole as the donor unit and bipyridine as the acceptor unit.Then,multiple benzophenone groups with non-planar structures were introduced at different positions using carbazole as the parent unit to form a multi-branched molecule with spatial site resistance.In addition,three-dimensional type donor units were designed and synthesised using carbazole as the main chain group,pyrene and other assembly groups,and applied to the preparation of three-dimensional type conjugated polymers.The photophysical properties of these materials were also investigated.Details were as follows:In Chapter 2,two pyridine groups were introduced as electron pulling groups on the carbazole to form a D-A₁-A₂type structure,which facilitates a more completely charge separated state.Four compounds,24P,24M,26P and 26M,with different positions of the pyridine N atom were designed and synthesized.Emission spectra in different solutions showed that these materials exhibit a large red shift of the emission peaks with increasing solution polarity,all exhibiting intramolecular charge transfer（ICT）characteristics.In comparison,24P had a stronger ICT signature.In addition,compounds 24P,25P and 26P had an acid-stimulated response.Their solids exhibited a clear response with a red shift in both absorption and emission spectra after acid stimulation.Both absorption and emission spectra recovered after acid-stimulated solids were subjected to reduced fumigation.To understand the stacking characteristics and molecular configuration of the compounds,single crystal structure analysis was carried out for 24P and 26P.Crystal information showed that the molecules of 24P were more loosely stacked,which facilitated the embedding of hydron into the molecules,resulting in a more pronounced acid-stimulated response in the 24P solid.In Chapter 3,several benzophenone groups with non-planar structures were introduced using carbazole as the parent,and molecules with multi-branched structures were designed and synthesized:the double-branched molecules,D2Z and D3Z,and the triple-branched molecules,T2O and T4O.The effect of different numbers of benzophenone substituents on the luminescence properties of the materials was investigated.Theoretical calculations showed that D3Z and T2O had a more complete charge separation.The emission spectra showed a more pronounced red shift of the D2Z emission peak with increasing solvent polarity,indicating that D2Z had a strong ICT character.The emission spectra before and after solid grinding showed that the molecules of the three-branched structure changed considerably before and after grinding,with the emission peak of T4O redshifted by 20 nm after grinding,and the relative intensity of the shoulder peak of T2O changed considerably after grinding,indicating that the molecules of the three-branched structure were loosely packed,suggesting that the introduction of benzophenone groups could enhance the non-planarity of the molecules and effectively suppress the strong intermolecular interactions.In Chapter 4,two 3D units,PZ and CZ,were designed and synthesised using a carbazole unit as the main chain group and a unit such as pyrene as the assembly group.two groups of conjugated polymers containing 3D units were synthesized by Still coupling using the 3D units as monomers,and the effects of the 3D units on the intermolecular interactions and photophysical properties of the polymers were investigated.The spectroscopic properties showed that of the two sets of 3D polymers,the polymer with pyrene as the assembled unit（PZ group polymer）,was able to effectively tune the intermolecular interactions.The PZ group polymers were selected as the donor material for the preparation of photovoltaic devices.The device performance showed that the open-circuit voltage of the corresponding photovoltaic devices gradually increased with increasing the content of PZ units,indicating that the addition of an appropriate amount of PZ units was beneficial to adjust the arrangement pattern between the chain segments,thus increasing the open-circuit voltage of the devices.