Design,Synthesis And Structure-properties Investigation Of Tetraphenylethene-based Molecules

With the rapid development of information technology,organic luminogens have achieved great breakthrough both in the understanding of light-emitting progress and the application of practical research in organic light-emitting devices(OLEDs)devices,bio-imaging,chemical sensors,etc.,For the vast majority of practical application,luminogens are used in the aggregate state.Mainly due to the strong ?-?stacking interactions,normal luminogens suffer badly from the aggregation-caused quenching(ACQ)effect,which directly limits their wide applications and performances in aggregate states.Since the first discovery of aggregation-induced emission(AIE)phenomenon by Benzhong Tang in 2001,nowadays,great attention has been attracted to the development of efficient luminogens with the characteristic of AIE in the opto-electric field.AIE concept provides a perfect alternative metheods to solve the aggregation-induced problems suffered in conventional luminogens.However,along with the development of functional materials in the molecular-structure designing and devices fabrication,the intermolecular packing pattern has been found out to play an important role in the performance of materials,which is represented as the whole of collective molecules.Therefore,it is meaningful to investigate the relationship of molecular structure and packing pattern,as well as the property of materials,to get a better understanding in the mechanism and figure out some rules,which can guide the molecular design and control the molecular packing pattern,thus realizing the better property or efficiency.In the first part of this thesis,the author designed and synthesized a sort of stimuli-responsive fluorescent tetraphenylethylene(TPE)derivatives and investigated the relationships between their molecular conformations,intermolecular packing patterns and distinct optical properties.In the following part,novel cathode interfacial materials constructed with TPE unit and zwitterionic groups were synthesized,and the influence of well-organized stacking structure on device performances which are induced by intermolecualr interactions were carefully investigated.In the last part,ultilizing the distinct aggregate states and the induced changes in fluorescent intensity,a novel hypochlorite probe was synthesized,and the sensing mechanism was carefully investigated.The main contents are as follows:Chapter one:The mechanism of AIE and the application of TPE derivatives were introduced.First,the discovery and mechanism of AIE phenomenon were introduced.The author focused on the designing concepts and applications of TPE derivatives in various fields.Based on these,the investigation of the relationship between molecular structure,molecular packing pattern and property was very important.Finally,the ideas of this thesis were presented.Chapter two:A series of TPE derivatives,namely TPE-C1,TPE-C2,TPE-C3,TPE-C4 and TPE-C6,with different length alkyl chains were synthesized,which exhibited distinct piezochromic luminescent(PCL)properties.Based on the crystalline structures,the molecular conformations and intermolecular packing patterns were investigated and compared.The relationship between intermolecular packing,emission and PCL property was presented.Meanwhile,the theoretical model and mechanism for the PCL property of twisted non-planar molecules were built up.The PCL property was badly affected by the tightness of molecular packing in crystal.The most compact packing mode would induce a better co-planarity of molecular conformation in crystalline state,hence resulting a smaller alteration upon external force,which contributes a weaker PCL property.Chapter three:Two crystalline polymorphs can be prepared from TPE-C1,which exhibit different mechanoluminescent(ML)activity.Careful investigation of their crystal structures and analogues demonstrates that the abundant and intense intermolecular interactions attributed to the special molecule packing of TPE-C1 in the Cp-form crystal,account for the distinct compressive resistance and exciting efficient ML performance.The block-like Cp-form one exhibited highly bright blue emission upon grinding,due to the more and stronger intermolecular C-H…O hydrogen bonds and C-H…? interactions,which largely reduced the possible energy loss via non-radiative relaxation channels by decreasing the molecules slippage under the stimulus of the force.These results provided some information to understand the structure-property relationship of organic ML materials,which will give some guidance for the design of efficient organic ML materials.Chapter four:A new kind of interfacial material consisting of TPE units were synthesized for the first time,with an efficiency of 8.94%achieved by inserting TPE-2 as cathode interlayer,which was a relatively high PCE for PC71BM:PTB7-based conventional PSCs with the single-junction structure.In contrast to the random aggregate state of TPE-1,TPE-2 could form an orderly aggregated structure by the electrostatic attraction of the zwitterionic groups in adjacent molecules.The well-organized structure induced the lamellar stacking pattern of TPE-2 along the vertical orientation,which was beneficial for the electron transporting,resulting in a largely enhancement in Jsc and FF.Chapter five:Based on the good interfacial modification performance of TPE-2,a series of interfacial material constructed with TPE units and different water soluble polar groups,namely TPE-3,TPE-4,TPE-5 and TPE-6,were designed and synthesized.By inserting these four molecules as cathode interlayers in PC71BM:PTB7-based conventional PSCs,relatively high PCEs of 9.21%,9.15%,8.89%and 9.12%were achieved,respectively.The influence of different polar groups on the devices efficiencies and process abilities were also investigated carefully.Chapter six:Based on the restriction of intramolecular motion(RIM)principle and the reliable reactivity between boron esters and hypochlorite(OCl-),a highly sensitive and selective probe TPE2B have been successfully designed and synthesized.Due to the distinct increase in water solubility of TPE20H,which was generated from the reaction between TPE2B and OCl-,the strong emission of TPE2B was quenched dramatically.The response speed was as fast as 30 seconds with a detection limit as low as 28 nM.Additionally,test papers were also fabricated and exhibited a highly sensitive response to 0.1 mM OCl-.Additional,TPE20H,TPEB and TPEOH were synthesized to investigate the sensing mechanism.