Synthesis And Self-assembly Behavior Of Novel Low Molecular Organogelators Based On Carbazole

Low molecular weight organogels,one type of soft matter with three-dimensional?3D?scaffold,are formed by the intermolecular non-covalent interactions,such as H-bonding,?-?interaction,van der Waals and coordination interactions.The initial formed nanofibers could intertwine a 3D network,which endows the gels with strong ability to immobilize solvent molecules.Due to the susceptible nature of the non-covalent interactions,significant changes could happen in the gel system towards external stimulus?temperature,pH,mechanical forces,UV light,ions?.Thus,the organogels have a wide application in smart materials.While designing gelators,some auxiliary groups?such as amide,hydroxyl,urea,cholesterol and sugar,et al.?are often incorporated in order to enhance the noncovalent interactions.However,the organogelators without common auxiliary groups is rarely reported until now.Recently,some groups have demonstrated that tert-butyl,cyano and trifluoromethyl could be seen as“non-traditional auxiliary groups”facilitating the formation of organogels.In general,the organogelators without common auxiliary groups is rarely reported until now,especially the molecules without“non-traditional auxiliary groups”meanwhile.The exploration of the non-traditional organogelators could broaden the scope of gels to some extent and provide a new way for devising organogelators.Furthermore,it could bring a better understanding of intermolecular non-covalent interactions.So it is extremely necessary to study these materials.In our work,we design and synthesis two new organogelators without any common and“non-traditional”auxiliary groups.The results show that both of them have the ability to undergo gelatinization in several solvents.And the SY1 gels formed in ethyl acetate?EA?could further assembled into a macroscopic solid structure spontaneously.1.In this work,we find that a‘‘butterfly”-shaped?-conjugated molecule SY1.In SY1,benzophenone is designed to be the core structure with dimethoxydiphenylamine-substituted carbazole units as periphery groups.SY1 is able to gelatinize 6 kinds of solvents among the investigated solvents with the gelation-induced emission enhancement?GIEE?character.Many long entangled nanofibers are clearly observed in the SEM and AFM images.UV-Vis absorption spectra,¹H NMR spectra,XRD and electrostatic potential surface demonstrate the formation of J-type aggregates and the?-?interaction and dipole-dipole interaction play vital roles during gelation process.More excitingly,the gels of SY1 show reversible response upon acid/base treatment.2.In order to adjust the photoluminescence,we design a?-conjugated molecule SYW without methoxy group.SYW shows excellent gelation ability and the formed gel in toluene could emit strong yellow fluorescence.Using the similar research methods as SY1,the?-?interaction and dipole-dipole interaction are demonstrated to play important roles in the process of forming gel.In addition,the xerogel film of SYW exhibits bright orange emission and possesses 3D structure with a high surface area.We measure its fluorescence in the presence and absence of TFA vapour.The detection limit is estimated at a low level of 3.2 ppb,representing a high value among organogels system reported.3.The SY1 gels formed in EA could undergo a secondary self-assembly process,and bright yellow solid balls?SY1-balls?with uniform size?ca.0.5 mm?and regular morphology are obtained.SEM images show the SY1-balls are assembled by rod-like fibers and could emit strong yellow luminescence.XRD results demonstrate the molecular arrangement of SY1-balls is the most ordered compared with the as-prepared SY1 powder and gels formed from EA.By analysing ¹H NMR spectroscopy,XRD and electrostatic potential surface,the self-assembly process of SY1-balls was speculated.More interestingly,the Fe³⁺and Hg²⁺could quench the emission of SY1-balls,and in the meantime,the color of SY1-balls changes from yellow to black.Moreover,when we add a triphenylamine derivative?TPA1?into SY1 system,a two-component organogels could be obtained.Excitingly,small spherical particles could be found in the initial formed two-component organogels when the SY1 and TPA1 are in certain ratios.With increased aging time,the system could also undergo a secondary self-assembly process.Finally,some hierarchical self-assembly spherical solid with core-shell structure,named ST-balls,could be obtained.According to the cross-sectional morphology by SEM and elemental distribution by EDS,the formation process of the ST-balls was proposed.It is the first report on the organogels spontaneously self-assembled into the macroscopic structures.