| In recent years,phosphorescent Ir(III)complexes have attracted much attention due to their high luminescence efficiencies,rather short phosphorescence lifetimes and luminescent stabilities.Therefore,they have been widely investigated for their emerging applications in organic light emitting devices(OLEDs),cell imaging and photocatalysis.However,traditional transitional phosphorescent materials usually show strong emission in delute solution but suffer from phosphorescence quenching at a high concentration or in the solid state.The phenomenon of aggregation caused quenching(ACQ)has troubled scientists for more than half a century since F?rster's discovery of the concentration quenching effect in 1954,herein,how to solve the problem of ACQ and achieve high efficient luminescent materials have been the focus work.In 2001,Tang et al.reported a new concept of aggregation induced emission(AIE).For AIE-active materials,emission intensities are weak when dispersed in dilute solution but show strong emission when aggregated.The attractive properties of AIE-active materials gave a tremendous push for the development of phosphorescent luminescent materials,especially as candidates for applications in biological probes,chemical sensing and stimuliresponsive materials.The emission color or intensity of stimuli-responsive materials can be changed in response to external stimuli such as pressure,light,electricity and temperature.Piezochromic luminescence(PCL)materials are a class of smart materials which change colour or emission in the solid state in response to external pressure or mechanical grinding.They are widely studied in optical recording,anti-counterfeiting,strain-or pressure-sensing and data encryption due to their easy operation and fast response.However,up to now,phosphorescent Ir(III)complexes with AIE and PCL are relative rare.Herein,the study of their phosphorescent performances are significant to expand the application prospect of highly efficient luminescent materials.In this paper,we design and synthesize two Schiff-based ligands,and two neutral dinuclear Ir(III)complexes are achieved by simple reaction.Their AIE and PCL properties have been investigated in detail.The outline of these studies is as follows:1.Ligand 1 is a kind of Schiff-base which prepared by a simple and mild reaction,and a new neutral dinuclear Ir(III)complex 1 was achieved by 2-phenylpyridine cyclometalated iridium chloro-bridged dimer reacting with Schiff-based ligand 1.The photophysical properties demonstrate that complex 1 is highly efficient orange emitter with AIE property.At the same time,complex 1 shows reversible PCL property which is clearly visible to the naked eye.This is the first neutral dinuclear Ir(III)complex which exhibits both PCL and AIE characteristics.NMR spectra,powder X-ray diffraction(PXRD)and differential scanning calorimetric(DSC)data of different states of complex 1 are presented.The result indicates that the variation in phosphoresecent luminescence properties is associated with alteration in the solid-state molecular packing and/or the intramolecular interactions.An efficient second-level anticounterfeit trademark and a data encryption device were fabricated using complex 1 as the active material.2.Based on our pervious work,we introduced t-butyl substituents as steric repulsion into Ligand 1 to obtain Ligand 2 and enhance the solubility of complex 1.A new neutral dinuclear Ir(III)complex 2 was achieved by the similar routine with complex 1.The photophysical properties demonstrate that complex 2 is highly efficient orange-red emitters with AIE property.Compared with complex 1,complex 2 exhibits longer wavelength,more evident PCL and AIE properties,better solubility in organic solvents and thereby extending the application of vapochromic.Herein,a simple and efficient volatile organic compounds sensor has been fabricated in which can respond to relatively high polarity solvents with different response times.The sensor developed in this work extends the current PCL and AIE applications. |
PDF Full Text Request