Synergistically Boosting the Circularly Polarized Luminescence of Functionalized Pillar[5]arenes by Polymerization and Aggregation

Abstract Supramolecular polymers based on chiral macrocycles have attracted increasing attention in the field of circularly polarized luminescence (CPL) owing to their unique properties. However, the construction of macrocyclic supramolecular polymers with highly efficient CPL properties in aggregate states still remains challenging. Herein, w e constructed a class of macrocycle‐based coordination polymers by combining the planar chiral properties of pillar[5]arene with the excellent fluorescence properties of aggregation‐induced emission luminogens. The formation of polymers enhances both the fluorescence and chiral properties, resulting in chiral supramolecular polymers with remarkable CPL properties. Increasing the aggregation degree of the polymers can further improve their CPL properties, as evidenced by a 21‐fold increase in the dissymmetry factor and an over 25‐fold increase in the fluorescence quantum yield in the aggregate state compared to the solution state. Such a synergistic effect of polymerization‐ and aggregation‐enhanced CPL can be explained by the restriction of intramolecular motions and aggregation‐induced conformation confinement. This work provides a promising method for developing highly efficient CPL supramolecular polymers.


Instruments
1 H NMR and 13 C NMR spectra were recorded on Bruker AVANCE III 600 MHz, AVANCE III HD 500 MHZ and AVANCE NEO 400MHZ at 298 K using CDCl3 as the solvent.
Chemical shifts (δ/ppm) were calibrated using the residual solvent peak as the internal standard (CDCl3: δ = 7.26 ppm for 1 H NMR spectra and 77.16 ppm for 13 C NMR spectra).wafer followed by natural evaporation for 24 h and then plating with gold via Leica EM ACE600.

Synthesis and characterization of compound 2:
Compound 1 was synthesized according to the reported procedures in literature. [1]Compound 1 (1 g, 1.33 mmol) was first added to 60 mL dichloromethane (DCM) in a 150 mL flask, into which the aqueous solution of ammonium ceric nitrate (2.92 g, 5.33 mmol) was then added dropwise at room temperature under stirring.After reacting for 1 h, 100 mL H2O was added to the mixture and the resulting mixture was extracted with DCM for 3 times.The organic phase was collected and then dried over anhydrous Na2SO4.After removing the solvent by rotary evaporation and further purification by the silica gel column chromatography (eluent: petroleum ether (PE)/ethyl acetate (EA) = 5/1, v/v), compound 2 (750 mg, yield = 78%) was finally obtained as red powder.

Synthesis and characterization of OTf-P5:
OTf-P5 was synthesized according to the reported procedures in literature [1] .Compound 2 (0.75 g, 1.04 mmol) was dissolved in 15 mL DCM in a 50 mL flask.Under N2 atmosphere, then the aqueous solution of Na2S2O4 (1.81 g, 10.4 mmol) was added into the above mixture dropwise under stirring and under N2 atmosphere.When the mixture changed from red to colorless, the reaction was stopped by adding 100 mL H2O to the mixture.The mixture was then extracted with DCM for 3 times.The organic phase was collected and then dried over anhydrous Na2SO4.After removing the solvent by rotary evaporation, the crude product was processed to the next step without further purification.The crude product and pyridine (1 mL) were added to 15 mL anhydrous DCM, and then trifluoromethanesulfonic anhydride (2 mL) was added dropwise to the mixture at 0 o C. Next, the reaction was allowed to stir for 12 h at room temperature.The reaction was quenched by adding water followed by extracting the mixture with DCM for 3 times.After drying the mixture over anhydrous Na2SO4, the solvent of the organic phase was removed by rotary evaporation.OTf-P5 was eventually obtained as white powder (550 mg, yield = 54%) after further purification by the silica gel column chromatography (eluent: PE/EA = 10/1, v/v). 1

Synthesis and characterization of compound 5:
Compound 4 (2 g, 4.08 mmol), K2CO3 (1.41 g, 10.20 mmol), Pd(PPh3)2Cl2 (143 mg, 204 μmol) and pyridine-4-boronic (476 mg, 3.88 mmol) were sequentially added into a 100 mL flask equipped with a magnetic stir bar under N2 atmosphere.Then the solvent mixture of THF/H2O (v/v = 4:1, 50 mL) was added into the reaction system.Next, the temperature was raised to 80 o C and the mixture was reacted for 72 h.Afterward, the reaction was cooled to room temperature and quenched by adding water into the mixture.After being extracted with DCM following by drying over anhydrous Na2SO4, the organic phase was collected and the solvent was removed by rotary evaporation.With further purification by the silica gel column chromatography (eluent: PE/EA = 10/1, v/v), compound 5 (1.1 g, yield = 55%) was obtained as white powder.

Synthesis and characterization of Py-TPE:
Compound 5 (1.1 g, 2.25 mmol), CH3COOK (1.33 g, 13.51 mmol), Pd(dppf)Cl2 (165 mg, 225 μmol) and bis(pinacolato)diboron (1.72 g, 6.76 mmol) were sequentially added into 30 mL anhydrous DMSO in a 100 mL flask equipped with a magnetic stir bar under N2 atmosphere.After raising the temperature to 100 o C, the mixture was allowed to react for 24 h.Then the reaction was cooled to room temperature and quenched by adding water into the mixture.After the mixture was extracted with DCM and dried over anhydrous Na2SO4, the organic phase was collected and the solvent was removed by rotary evaporation.Py-TPE (1.05 g, yield = 87%) was finally obtained as yellow soild by further purification using the silica gel column chromatography (eluent: PE/EA = 10/1, v/v). 1          The resolution of pR/pS-TPE-P5 was performed by Daicel Chiral Technologies (China) Co., Ltd. on a chiral HPLC equipped with a CHIRALPAK IG preparation column using DCM:MeOH = 1:1 as the eluent. [2]Flow rate: 1.0 mL/min.Temperature: 25 o C. The chromatograms before resolving are shown below.48.89%
Synthesis and characterization of pS-polymer: pS-TPE-P5 (10 mg, 6.64 µM) and silver nitrate (112 mg, 664 µM) were added to a single-neck flask with a volume of 50 mL.Then 10 mL of a mixed solution of THF/H2O (1:1) was added, and the mixture is stirred thoroughly at room temperature for 24 hours.After removing the solvent using a rotary evaporator, an appropriate amount of dichloromethane was added to flask.The mixture was washed with distilled water to remove excess inorganic salts.The organic phases were combined and anhydrous sodium sulfate was added for drying.After solvent removal, vacuum drying was performed, resulting in 7.7 mg of yellow solid pS-polymer (yeild 72%).

Theoretical Calculations of the Ground States
Density functional theory (DFT) calculations of pR-and pS-TPE-P5 were carried out by using Gaussian 16 program package . [3]The DFT calculations on the geometrical properties of the ground state were performed based on B3LYP density functional method including Grimme's dispersion correction with def2-SVP basis set.The UV-vis absorption and CD spectra were simulated with the optimized S0 geometries by the time-dependent DFT (TD-DFT) calculations at the wB97XD/def2-SVP level of theory.To provide an immediate and integrated view of the main photophysical parameters determining the total amount of circularly polarized photons emitted by a material, a parameter of brightness for CPL (BCPL) was recently proposed following the concept of fluorescence brightness, and the value of BCPL is defined by the following equation. [4,5]PL = εabs ×  × |glum|/2 where εabs denotes the molar extinction coefficient of the sample at the maximum absorption wavelength measured with an integrating sphere (Figure S24),  denotes the fluorescence quantum yield, and |glum| denotes the luminescence dissymmetry factor.

Theoretical Calculations of the Singlet Excited States
Time-dependent DFT (TD-DFT) calculations on the geometrical properties and electronic properties of singlet excited states of pR-TPE-P5, pS-TPE-P5 and pR-TPE-P5 dimer were performed at the wB97XD/Def2-SVP level using the Gaussian 16 program package. [3]The optimized S1 geometries of the dimer was obtained by conditionally optimizing the S1 configuration of pR-TPE-P5.The CPL-relevant parameters, including the electric transition dipole moment (μ), the magnetic transition dipole moment (m), and the vector angle between μ and m (θμ,m) were calculated from the optimized S1 geometries of the monomers and the dimer during the S1 → S0 transitions.The calculated dissymmetry factor (glum) of CPL is estimated according to the following formula [6] :
Electrospray ionization mass spectrometry (ESI-MS) was performed by a DFS high resolution FD-MS (Thermo Fisher Scientific, Bremen, Germany) operating in the positive ion mode.MALDI-TOF-MS results were recorded on a Bruker autoflex speed.The resolution of pR/pS-TPE-P5 was performed by the Daicel Chiral Technologies (China) Co., Ltd.Circular dichroism (CD) spectra were measured on Bio-Logic MOS-450.Fourier transform infrared (FTIR) spectra were obtained on a Nicolet 6700 spectrometer in the range of 4000-525 cm -1 over 128 scans.X-ray photoelectron spectroscopy (XPS) spectra were recorded on a VG Scientific X-ray photoelectron spectrometer (Model ESCALab220i-XL).UV-visible absorption spectra were recorded on a SHIMADZU UV-2600i UV-Vis spectrophotometer.The photoluminescence (PL) spectra and lifetime data were measured on an Edinburgh Instruments FLS1000 spectrophotometer.Fluorescence quantum yields were determined using a Hamamatsu C11347 spectrometer.Circularly polarized luminescence spectra were obtained on JASCO CPL300.The scanning electron microscope(SEM)images were recorded on a Thermo APREO S microscope, and the sample used for SEM imaging was prepared by dripping the solution (1 µM) onto a silicon

Figure S23 .
Figure S23.(a) The CPL spectra and (b) the glum spectra of pR-polymer and pS-polymer in solutions.Solution concentration: 10 µM.The scattered data represents the raw data and the solid lines are the fitting curve obtained by the Gaussian algorithm.

Figure S24 .
Figure S24.The glum value of pR-polymer in solutions measured for different times.Group 1, group 2, group 3 and group 4 represents the sample used for the measurement at each time under the same conditions.Solution concentration: 10 µM.

Figure S25 .
Figure S25.The UV-vis absorption spectra of pR-polymer, pS-polymer and pR/pS-polymer in DMSO/water mixture with a water content of 90% measured with an integrating sphere.Concentration: 10 μM.

Figure S26 .
Figure S26.(a) PL spectra of pR/pS-TPE-P5 in DMSO/water mixtures with different water fractions (fw).Concentration: 10 μM.Excitation wavelength = 298 nm.(b) Plot of the relative PL intensity (I/I0) values of pR/pS-TPE-P5 versus the water fraction.Inset: fluorescent photographs of pR/pS-TPE-P5 in pure DMSO solution and DMSO/water mixture with a fw of 90% taken under 365 nm UV irradiation.

Figure S27 .
Figure S27.(a) PL spectra of pS-TPE-P5 in DMSO/water mixtures with different water fractions (fw).Concentration: 10 μM.Excitation wavelength = 298 nm.(b) Plot of the relative PL intensity (I/I0) values of pS-TPE-P5 versus the water fraction.Inset: fluorescent photographs of pS-TPE-P5 in pure DMSO solution and DMSO/water mixture with a fw of 90% taken under 365 nm UV irradiation.

Figure S28 .
Figure S28.(a) PL spectra of pR/pS-polymer in DMSO/water mixtures with different water fractions (fw).Concentration: 10 μM.Excitation wavelength = 298 nm.(b) Plot of the relative PL intensity (I/I0) values of pR/pS-polymer versus the water fraction.Inset: fluorescent photographs of pR/pS-polymer in pure DMSO solution and DMSO/water mixture with a fw of 90% taken under 365 nm UV irradiation.

Figure S31 .
Figure S31.(a) Fluorescence lifetime of the DMSO solution of pR/pS-TPE-P5, the DMSO solution of pR/pS-polymer, pR/pS-TPE-P5 aggregates in the DMSO/water mixture with 90% water and pR/pS-polymer aggregates in the DMSO/water mixture with 90% water.(b) Fluorescence lifetime of the DMSO solution of pR-TPE-P5, the DMSO solution of pRpolymer, pR-TPE-P5 aggregates in the DMSO/water mixture with 90% water and pRpolymer aggregates in the DMSO/water mixture with 90% water.(c) Fluorescence lifetime of the DMSO solution of pS-TPE-P5, the DMSO solution of pS-polymer, pS-TPE-P5aggregates in the DMSO/water mixture with 90% H2O and pS-polymer aggregates in the DMSO/water mixture with 90% water.Concentration adopted for the measurements is 10 μM.

Figure S32 .
Figure S32.(a and c) SEM images of (a) pR-polymer and (c) pS-polymer samples prepared in solutions.(b and d) SEM images of (b) pR-polymer and (d) pS-polymer aggregates in in aggregate states (fw = 90%) with 90% water.Solution concentration: 1 µM.

Figure S33 .
Figure S33.(a) The CPL spectra of pR-TPE-P5 and pS-TPE-P5 in solution and aggregate states (fw = 90%).(b) The glum spectra of pR-TPE-P5 and pS-TPE-P5 aggregates in aggregate states with 90% water.Solution concentration: 10 µM.The scattered data represents the raw data and the solid lines are the fitting curves obtained by the Gaussian algorithm.

Figure S34 .
Figure S34.(a) The CPL spectra of pR-polymer and pS-polymer in solution and aggregate states (fw = 90%).(b) The glum spectra of pR-polymer and pS-polymer aggregates in solution and aggregate states (fw = 90%).Solution concentration: 10 µM.The scattered data represents the raw data and the solid lines are the fitting curves obtained by the Gaussian algorithm.

Figure S35 .
Figure S35.(a) The CPL spectra and (b) the glum spectra of pR-polymer film and pSpolymer film.The scattered data represents the raw data and the solid lines are the fitting curves obtained by the Gaussian algorithm.Films for the measurement were prepared by drop-casting the DCE solution of the polymers (concentration: 0.5 wt%) onto quartz plates.

Figure S36 .
Figure S36.CD spectra of pR-polymer in solution state (10 μM) and aggregate state in aqueous media with different water fractions.

Figure S37 .
Figure S37.Transition dipole moments of (a) pR-TPE-P5 and (b) pS-TPE-P5 for the S1 → S0 transition.The electric transition dipole moment vectors (μ) are shown in green, and the magnetic transition dipole moment vectors (m) are shown in blue.The length of the μ vector is amplified 4 times for charity.

Figure S38 .
Figure S38.Natural transition orbitals of pS-TPE-P5 calculated with the optimized S1 geometry by TD-DFT at the wB97XD/def2-SVP level.The percentage refers to the proportion of the dominant particle-to-hole transition.

Figure S39 .
Figure S39.(a) Transition dipole moments of pR-TPE-P5 dimer for the S1 → S0 transition.The electric transition dipole moment vectors (μ) are shown in green, and the magnetic transition dipole moment vectors (m) are shown in blue.The length of the μ and m vector is amplified 5 times for charity.(b) The optimized S1 geometries of pR-TPE-P5 dimer obtained by conditionally optimizing the S1 configuration of pR-TPE-P5 and its calculated transition dipole moments for the S1 → S0 transition.The unit for |μ| and |m| is esu cm and erg G -1 , respectively.

Table S2
Statistical table of fluorescence lifetime (τ)