Fabrication Of Pillar[n]arene-Based Supramolecular Coordination Hybrid Materials And Their Luminescent Properties

Fluorescent materials fabricated via supramolecular assembly,possessing both inherent reversibility/stimuli-responsiveness and controllable fluorescence properties,have attracted much attention in the field of luminescent materials and have proved to be significant candidates in terms of organic light-emitting devices and chemical sensing.The assembly patterns dominated by non-covalent interactions will affect the properties of organic chromophores,because the aggregation state and energy transfer behaviors between chromophores can be dynamically adjusted by the assembly-disassembly processes,so that the fluorescence properties of the material can be effectively regulated.Therefore,supramolecular systems with adjustable fluorescent properties hold great promise in the scope of scientific research and real-world applications of smart materials.However,although researchers have made tremendous efforts in the research of fluorescent supramolecular materials,most of the reported supramolecular systems still remain in their infancy.Key challenges in this field mainly involve unsettled fluorescence mechanisms,sophisticated components in one system,elusive achievement in multicolor emission,and limited application range.Therefore,to construct supramolecular-assembled fluorescent materials with simpler components,well-defined morphologies,optimized luminescent properties and highly adjustable fluorescence properties through elaborate molecular and materials design,is the primary solution to most of the above problems,by which the interacting modes between components can be comprehensively studied to verify how the supramolecular assembly further affects and regulates the fluorescence properties of the materials.This essay demonstrates the construction of novel fluorescent supramolecular hybrid materials with adjustable luminescence properties using pillar[n]arenes as the supramolecular building blocks,and the exploration of the influence of the macrocycle structures of pillar[n]arenes on the overall luminescent properties of the material within the confined space generated by the formation of metal-organic supramolecular framework driven by coordination.Particularly,the roles of“luminescence regulator”and“morphology/function modulator”played by pillar[n]arenes are investigated for the purposes of novel material construction protocols,mechanism exploration,multicolor fluorescence emission,and broader applications,can be achieved based on the construction and characterization of the materials.Accordingly,we have accomplished three main sections of relative research:（1）We have successfully constructed a pillar[5]arene-based hybrid material with stimuli-responsive luminescent properties and ion-sensing abilities from a pyridine-modified conjugated pillar[5]arene and a planar chromophore oligo（phenylenevinylene）upon coordination of Cd（II）metal cores.This new material not only shows an optimized luminescence due to the minimizedπ–πstacking and efficient charge transfer properties benefitting from the existence of pillar[5]arene rings,but also exhibits tunable multicolor emission induced by different external stimuli including solvent,ions and acid,indicating great application potential as a fluorescent sensory material,especially for Fe³⁺.With this pillar[5]arene-based dual-ligand hybrid material,valid optimization and regulation on the fluorescence of the original chromophore have been achieved,which demonstrates a plausible strategy for the design of tunable solid-state luminescent materials and also a prototypical model for the effective regulation of fluorescent properties of planarπsystems using synthetic macrocycle-based building blocks.（2）We have concurrently achieved both luminescent molecular crystals and coordination luminescent nanocrystals via facile supramolecular self-assembly processes using a conjugated pillar[5]arene,P5bipy.The molecular crystals of P5bipy exhibited enhanced blue luminescence attributed to theπ-conjugated dual-pyridine axle and the unique packing fashion in its crystal structure.Furthermore,the nanocrystals with well-ordered crystalline structures and remarkable long lifetime luminescence were obtained via coordination to Cu（I）,which also exhibited tunable emission properties under varied solvent conditions.This work provides a new strategy for developing supramolecular crystal materials with optimized luminescent features,enriching the studies of both supramolecular self-assembly and solid-state light-emitting materials.（3）we have fabricated an innovative type of macrocycle-strutted coordination microparticles（MSCM）using pillararenes as the struts and“pockets”,which performs unique activities of fluorescence-monitored photosensitization and substrate-selective photocatalytic degradation.Prepared via a convenient one-step solvothermal method,MSCM showcases the incorporation of supramolecular hybridization and macrocycles,being endowed with well-ordered spherical architectures,superior photophysical properties,and photosensitizing capacity,where self-reporting fluorescence response is exhibited upon photo-induced generation of multiple reactive oxygen species.Importantly,photocatalytic behaviors of MSCM show marked divergence toward three different substrates and reveal pronounced substrate-selective catalytic mechanisms,attributing to the variety in the affinity of substrates toward MSCM surfaces and pillararene cavities.This study brings new insight into the design of supramolecular hybrid systems with integrated properties and further exploration of functional macrocycle-based materials.