Design And Synthesis Of Stimuli-responsive Phenothiazine Derivatives And Their Optoelectronic Properties

Stimuli-responsive organic light-emitting materials are a class of advanced smart materials that can respond to different external stimuli and then adjust their physicochemical properties.They are widely used in smart switches,digital technology,biomedicine,sensors,and light-emitting devices,and have attracted the attention of more and more researchers.In this thesis,a series of organic light-emitting materials with stimuli-responsive properties were designed and synthesized based on phenothiazine group,phenothiazine dioxide group and N-phenyl-2-naphthylamine group.By changing theπ-conjugation length between the donors and acceptors and optimizing the structures of acceptor,the electronic structures of emitters are adjusted,and the components of the local state and charge transfer state of the emitters are changed,their photoelectric properties are regulated.Finally,we have a new understanding of the stimuli-responsive fluorescence and room temperature phosphorescence properties and luminous mechanium by the analysis of the photophysical properties,theoretical calculations,single crystal structure and electroluminescence properties of the emitters.The main research contents are as follows:(1)Two twisted D-π-A-typed luminescent materials with photostimulation-responsive characteristic,named PTZ-PNA and PTZ-BP-PNA,were designed and synthesized using N-Phenyl-2-naphthylamine groups and phenothiazine groups with different electron-donating abilities connected by benzene or biphenyl ring.Both compounds have obvious photoresponsive phenomenon in dimethyl sulfoxide solution.With the prolonged UV excitation time,the intensity of blue emission(417 and 439 nm)of PTZ-PNA and PTZ-BP-PNA gradually increased,while the intensity of green emission(492 and 509 nm)gradually decreased,and their emission peaks were blue-shifted by 75 and 70 nm,respectively.Both compounds exhibited obvious photoresponsive phenomena in spin-coated PMMA-doped films.With the prolonged UV excitation time,the intensity of blue emission(417 and 404 nm)of PTZ-PNA and PTZ-BP-PNA gradually weakened,and the intensity of green emission(494and 493 nm)gradually increased.The results indicate that a photochemical reaction occurs under the long-time UV excitation.Interestingly,in the PMMA-doped films prepared by the drop coating method,both compounds exhibited photoactivated room temperature phosphorescence.The phosphorescence emission bands of PTZ-PNA and PTZ-BP-PNA at500-550 nm gradually increased with the prolonged UV excitation time,and the longest phosphorescence lifetimes after completed excitation were 12.72 and 15.35 ms,respectively.It can be attributed to continuously consuming residual oxygen in the rigid matrix of PMMA under continuous UV irradiation.(2)The oxidized phenothiazine group can introduce the d-pπbond that will enhance the room temperature phosphorescence,on the other hand,it can adjust the intramolecular charge transfer state due to the weakened electron donating ability.Two distorted D-π-A-typed photostimulation-responsive luminescent materials,named 2OPTZ-PNA and 2OPTZ-BP-PNA,were designed and synthesized using 10H-phenothiazine 5,5-dioxide group as acceptor,N-phenyl-2-naphthylamine group as donor,and benzene and biphenyl asπbridge.The two compounds exhibited weak photochromism in the spin-coated PMMA-doped films,further confirming that the photochromism originates from the phenothiazine group.In drop-coated PMMA-doped films,the two compounds exhibited reversible photo-activated room temperature phosphorescence.With the prolonged UV excitation time,phosphorescence emission intensity of 2OPTZ-PNA and 2OPTZ-BP-PNA at 500-550 nm gradually increased,and the longest emission lifetimes after completed excitation were 624 and 29 ms,respectively.Both 2OPTZ-PNA and 2OPTZ-BP-PNA-based non-doped devices achieved violet-blue emission,and their emission peaks were located at 424 and 436 nm,respectively,and the corresponding CIE coordinates were at(0.164,0.060)and(0.155,0.046).In particular,the non-doped device based on 2OPTZ-BP-PNA exhibited excellent EL performance,with the maximum external quantum efficiency and maximum brightness reaching 4.1%and 2602 cd/m~2,respectively.(3)The carbonyl group with strong electron-withdrawing ability can not only enhance the room temperature phosphorescence,but also regulate the intramolecular and intermolecular charge transfer state.A distorted D-π-A-typed stimuli-responsive luminescent material was designed and synthesized,named 2OPTZ-CO-PNA,using 10H-phenothiazine 5,5-dioxide and carbonyl as the acceptor and N-phenyl-2-naphthylamine as the donor.Due to the more distorted spatial structure,aggregation-induced luminescence and mechanochromic properties are simultaneously obtained and its solid powder obtained a high PLQY of 81%.When the crystalline powder of the compound is stimulated by external mechanical force,the emission peak exhibited an obvious red-shift of 64 nm from 445 nm to 509 nm.The luminescence properties can be restored to the crystalline state under the stimulation of solvent and temperature.In the drop-coated PMMA-doped films,phosphorescence emission peak at 510nm gradually increased with the prolonged UV excitation time,and a phosphorescence lifetime of 612 ms was found with the excitation time of 80 s.Based on 2OPTZ-CO-PNA,non-doped and doped devices were prepared.The non-doped device achieved green emission with a CIE coordinate of(0.26,0.48),and the maximum external quantum efficiency and maximum brightness reached 3.9%and 8520 cd/m~2,respectively.The doped device achieved sky-blue emission with the CIE color coordinate of(0.17,0.23),and the maximum external quantum efficiency and maximum brightness reach 3.4%and 5856 cd/m~2,respectively.