Circularly polarized luminescence from a common alkoxy pillar[5]arene and its co-aggregates withπ-conjugated rods

Cylinder-shaped macrocycles composed ofπ-panels have attracted special attention as one of the best platforms for the development of organic molecule-based chi-roptical materials.Pillar[n]arenes are a class of macrocycles with the advantage of easy preparation but have not been extensively investigated from the perspective of luminescent molecules.However,common alkoxy pillar[n]arenes arefluorescent in non-haloalkane solvents,showing potential to be used for molecule-based chi-roptical materials.In this work,circularly polarized luminescence(CPL)spectra are reported for a pillar[5]arene with stable planar chirality using tetrahydrofu-ran(THF)and cyclohexane as solvents,which has been missing for many years.The pillar[5]arene also forms co-aggregates with 1,4-bis(phenylethynyl)benzene and 1,4-bis[(pentafluorophenyl)ethynyl]benzene in THF/H2O mixtures,owing to a hydrophobic effect.The co-aggregates with thefluorinatedπ-rod display a new low-energy absorption peak and broad emission band as well as intense circular dichroism and CPL signals.Chiral information from the enantiopure pillar[5]arene core is efficiently transmitted to the co-aggregates with theπ-conjugated rod,lead-ing to the highest dissymmetry factor for CPL(2.9×10-2 at 472 nm)among pillar[n]arene-based CPL materials.

Dynamic properties of a flexible metal-organic framework exhibiting a unique"picture frame"-like crystal morphology

The precise control of the crystal morphology of metal-organic frameworks(MOFs)enables optimization of its adsorptive properties,as well as enables better integration within functional devices.However,the influence of such modifications on the dynamic properties of flexible MOFs is poorly understood Here,we report the synthesis of a series of Cu_(2)(bdc)_(2)(bpy)(bdc^(2-)=1,4-benzenedicarboxylate;bpy=4,4,-bipyridine)crystals having an unusual picture frame-like morphology that results from a restriction in the quantity of bpy pillars added to the reaction mixture during the intercalation of the Cu_(2)(bdc)_(2)(MeOH)_(2)layers.The width of the frames is found to correlate with the quantity of bpy,and importantly,causes the dynamic properties of the resulting Cu_(2)(bdc)_(2)(bpy)material to vary between rigid,elastic,and shape memory modes.In all,the results demonstrate the potential for the properties of MOFs to be optimized via subtle manipulations in the crystal morphology rather than changes in the overall material composition.