| The design and synthesis of novel π-conjugated systems with uniqueoptic-electronic properties have attracted increasing attention due to their potentialapplications in sensors, organic light-emitting diodes (OLEDs), field-effect transistors,solar cell, etc. It is well-known that heterocyclic compound bearing electron-richnitrogen heteroatom, such as triphenylamine, phenothiazine, carbazole devivants canbe acted as building blocks of self-assemblies with appealing optical andoptoelectronic properties. They have been used as luminescence and seneory materials.Herein, we have synthesized a series of novel azahetero compounds. Theirself-assembled behaviors and photophysical properties have been studied. Somecreative results have been obtained, and are outlined as follows:(1) A novel rigid π-gelator without alkyl chain and H-bonding unit has beensynthesized. Based on the excellent self-assembled ability of π-gelator, we have alsoconstructed nanofibrils with strong red emission via solution dispersion approach. Itwas found that the nanofibrils-based film exhibited high selectivity and highsensitivity to gaseous amines and pyridine.Firstly, a series of rigid β-diketone-boron difluoride derivatives had beensynthesized, and it was found that only the boomerang-shaped compound1exhibitedgood gelation ability in some mixed solvents. It suggests that the balanced π-πinteraction, which can be tuned by the molecular conjugation, can promote rigidπ-conjugated molecules without alkyl chain and H-bonding unit to gelatinize solvents.This strategy provides a new perspective in design of new rigid π-gelators from thepoint of view of atomic economy.Secondly, we have constructed nanofibrils with strong red emission from theboomerang-shaped π-gelator via solution dispersion approach. It was found that thefluorescence of the nanofibrils-based film could be quenched efficiently and rapidlyafter being exposed to gaseous amines (such as n-butylamine, dibutylamine,tributylamine, triethylamine, cyclohexylamine, hydrazine, aniline andN,N-dimethylaniline) and pyridine, while no obvious fluorescence quenching was observed for other common reagents, including hexane, toluene, methanol, ethanol,water, acetone, acetonitrile, chloroform, tetrahydrofuran, nitrobenzene, acetic acid andanisole. Therefore, the nanofibrils could selectively sense volatile organic amines andpyridine. Notably, the response time of the nanofibrils-based film to aniline was about1.06s, which was one of the fastest fluorescent respond to aniline. Morever, thedetection limit of the nanofibrils-based film for aniline vapor was as low as ca.100ppb. We deduced that the high sensitivity and fast response time of the sensorynanofibrils for gaseous amines originated from the high surface-to-volume ratio andgood porosity of the3D networks consisting lots of nanofibrils (favoring enhancedadsorption, accumulation and diffusion of gaseous molecules), as well as theamplified fluorescence quenching induced by enhanced intermolecular excitondiffusion along the long axis of1D nanostructures. In addition, the goodphotostability and reversibility of the fluorescent nanofibrils in detecting aminevapors favored the practical applications. The obtained results will be helpful fordesigning novel fluorescence chemosensors to detect trace amine vapors with highperformance.(2) We had synthesized two vinyl substituted oligophenothiazines P3and P5,which could be used as efficient fluorescence probing molecules for detection of thevapor of p-NT, DNT and TNT. Stern-Volmer plots revealed that phenothiazine-basedoligomers exhibited higher sensitivity to nitro compounds (the Ksvvalues of P3andP5for TNT were4607M-1and4149M-1, respectively) compared with other reportedpolymers (the Ksvvalues were in the range of1000-4000M-1) in solution. Notably, P3and P5films could detect the vapor-phase nitro compounds with high sensitivity andfairish reversibility. P3film gave a linear fluorescence quenching response to TNT inthe range of7-800ppb with the detection limit of4ppb, and the detection limits toDNT and p-NT was40ppb and48ppb, respectively. It was also found that theinterferents, including common organic solvents, p-nitrophenol and2,4-dinitrophenylhydrazine can not lead to obvious fluorescence quenching, meaningthat the film based on oligophenothiazines exhibited good specificity of fluorescenceresponse to explosive. Furthermore, the absorption bands for P3in the film appearedat308and426nm, which red-shifted gradually accompanying with the declining ofthe absorption intensity when prolonging the time of P3film exposed to DNT vapor.For instance, they shifted to323nm and466nm after P3film was exposed in DNT vapor for30min. Notably, the enhancement of the absorption above500nm suggestedthe formation of charge-transfer complex between P3and DNT. Therefore, aselectron-rich systems, oligophenothiazines and related compounds should be idealcandidates of sensory materials for detection of nitroaromatics.(3) We researched the synthesis and characterization of four π-extendedheteroacenes containing alternant benzene and pyrrole rings through a simpleintramolecular reductive cyclization route, and we demonstrated that the cyclizationreaction was high regioselective in this system. The regiospecificity of Cadoganreaction orients to4-position (or5-position) of carbazole in absence of sterichindrance. Photochemical and electrochemical studies had been carried out tocharacterize the energies of the HOMO and LUMO orbitals, and the wideHOMO-LUMO gap revealed that they can be applicable in organic electronics. Theobtained results will be helpful to expand the route for synthesis of other π-extendedN-fused heteroacenes.
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