Pagoda[5]arene with Large and Rigid Cavity for the Formation of 1∶2 Host-Guest Complexes and Acid/Base-Responsive Crystalline Vapochromic Properties

Pagoda[5]arene(P5),which is composed of five 2,6-dimethoxylanthracene(2,6-DMA)subunits bridged by methylene groups at 1,5 positions,was conveniently synthesized in 43%by trifluoroacetic acid(TFA)-catalyzed one-pot condensation of commercially available 2,6-DMA and paraformaldehyde in 1,2-dichlorobenzene(o-DCB)at room temperature.P5 showed a highly symmetrical pentagonal structure with a large and deep electron-rich cavity,which made it form stable 1∶2 host–guest complexes with various aryl-pyridinium,bipyridinium,and stilbazolium salts in solution.Interestingly,P5 could complex two or even three guests with its intrinsic cavity and the pseudocavity formed by the adjacent macrocycles in solid states.Moreover,the strong intermolecular charge-transfer(ICT)interactions between P5 and the guests were observed.Especially,the complexes formed by P5 and the protonated pyridinium or bipyridinium salts showed acid/base-responsive color changes in solution and remarkable crystalline vapochromic properties by two kinds of processes:from ICT to no ICT and from ICT to enhanced ICT interaction or vice versa.We believe that the easily available P5 with the specific structure and intriguing 1∶2 host–guest complexation can find wide application in supramolecular assemblies and functional materials.

Julolidine-labelled fluorinated block copolymers for the development of two-layer films with highly sensitive vapochromic response

Fluorinated block copolymers composed of a polystyrene(Sx) first block and a polyacrylate second block carrying hydrophobic/lipophobic perfluorohexyl side chains(AF) were prepared by atom transfer radical polymerization(ATRP). Fluorescence emission properties were imparted to the copolymers by incorporation in the second block of a julolidine-based fluorescent molecular rotor(JCBF). The synthesized block copolymers were used as the fluorescent low-surface energy thin top-layer onto a polystyrene bottom-layer to produce novel two-layer film vapochromic sensors. Contact angle and X-ray photoelectron spectroscopy(XPS) measurements revealed that the two-layer film surfaces were hydrophobic and lipophobic at the same time and highly enriched in fluorine content as a result of the effective segregation of the perfluorinated tails to the polymer-air interface.The fluorescence intensity of the two-layer films decreased significantly when they were exposed to vapours of organic solvents,including tetrahydrofurane, chloroform, and trifluorotoluene. However, an AF content-dependent sensing behaviour was also observed, with the two-layer films containing the copolymer with the shorter fluorinated block giving a more rapid and almost quantitative decrease in fluorescence variation. Fluorescence emission of the films was also proved to vary with temperature.Both the vapochromic and thermochromic responses were reversible after successive solicitation cycles. The fluorescence variation of the two-layer films was much more marked than that of the corresponding PS/JCBF blend, thus providing a system potentially applicable as highly sensitive volatile organic compound(VOC) sensor, thanks to the active role of the fluorinated block in promoting the migration of the fluorophore to the outermost surface layers.

A novel conformationally adaptive macrocyclic tetramaleimide with flipping pyrene sidewalls

The synthesis,structure,and properties of pyrene-based conformationally adaptive macrocycles are described.This new type of conformationally adaptive macrocycle was constructed through Perkin reaction,followed by imidization.By changing the condensation partner as the linking unit,a family of conjugated macrocycles with different sizes of the cavity was synthesized,which provide a simple and modular synthetic strategy towards the conformationally adaptive macrocycles.Furthermore,the macrocycles provide two well-defined conformations through flipping pyrene subunit,which were unambiguously determined by single-crystal X-ray diffraction analysis.The conformational interconversion barrier was determined by density functional theory(DFT)calculations.This new macrocycle also demonstrated unique properties,such as vapochromic behavior and aggregation emission enhancement effect.Furthermore,we have also investigated the effect of the linker on the shape and photophysical properties of the resulting macrocyclic products.

Methanol-induced luminescence vapochromism based on a Sb^(3+)-doped organic indium halide hybrid

Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids.The asformed doping species show great potential in optoelectronic applications due to their high photoluminescence quantum yield(PLQY)and excellent stability.Herein,we report highly emissive Sb^(3+)-doped indium halides(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb(C_(6)H_(18)N_(2)^(2+)=N,N,N',N'-tetramethylethane-1,2-diammonium)prepared by solution evaporation methods with an emission that peaked at 565 nm and a PLQY of 74.6%.Photophysical characterizations and density functional theory computational studies verify the broadband emission originating from a self-trapped exciton.Interestingly,a drastic red shift of the emission peak from 565 to 663 nm with yellow luminescence turning to red is observed once the(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb hybrid is exposed to methanol vapor.Moreover,when the methanol-exposed hybrid is put in air,the emission reverts to 565 nm in several minutes.Single-crystal X-ray diffraction studies show a subsequent structure distortion upon the coordination of methanol to the Sb(III)center,which is responsible for the drastic red shift of the emission.Encouragingly,we found that(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb exhibits a specific response to methanol vapor after screening a series of volatile organic compounds with different polarities.Besides,a negligible change of the emission intensity is observed after several cycles of uptaking and releasing methanol.The high fatigue resistance and specific solvent response of the Sb^(3+)-doped indium halide make it a very promising methanol detector.

Development of Dual Phosphorescent Materials Based on Multiple Stimuli-Responsive Ir(Ⅲ)Acyclic Carbene Complexes

A new series of Ir(Ⅲ)carbene complexes with luminescent mechanochromism derived from trans-cis isomerization has been developed.Through the introduction of π-conjugating groups into the acyclic carbene ligand,the mechanochromic trans-and cisconfigurations can be readily interconverted,leading to dual emissive properties in the solid state.Moreover,the solid-or film-forming solvent system can control the dual emission and mechanoresponsive properties in the solid state.The potential uses of a single emissive complex to develop multicolor emissive and multiple stimuli-responsive films have been studied.