Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

Herein, we have designed and fabricated a simple and efficient supramolecular self-assembled nanosystem based on host–guest interactions between water-soluble tetraphenylethylene-embedded pillar[5]arene (m-TPEWP5) and ammonium benzoyl-ʟ-alaninate (G) in an aqueous medium. The obtained assembly of m-TPEWP5 and G showed aggregation-induced emission (AIE) via the blocking of intramolecular phenyl-ring rotations and functioned as an ideal donor. After the loading of eosin Y (EsY) as acceptor on the surface of the assembly of m-TPEWP5 and G, the worm-like nanostructures changed into nanorods, which facilitates a Förster resonance energy transfer (FRET) from the m-TPEWP5 and G assembled donor to the EsY acceptor present in the nanorod assembly. The system comprising m-TPEWP5, G and EsY displayed moderate FRET efficiency (31%) at a 2:1 molar ratio of donor-to-acceptor. Moreover, the obtained supramolecular nanorod assembly could act as a nanoreactor mimicking natural photosynthesis and exhibited a high catalytic efficiency for the photocatalytic dehalogenation reaction of various bromoketone derivatives with good yields in short reaction time in water.


General information and experimental procedure
All common available reagents and solvents were purchased from Energy Chemical Reagent Co., Ltd. and used without further purification. Column chromatography was performed with silica gel (200-300 mesh) produced by Shanghai Titan Scientific Co., Ltd. Yields were given as isolated or calculated yields. NMR spectra were recorded with a Bruker 400 MHz spectrometer. UV-vis absorption and fluorescence spectra were taken on a SHIMADZU UV-1700 UV and Angdong F-380 Spectrometer, respectively. Transmission electron microscope (TEM) analysis was performed on a JEM-2100 instrument.
Experimental procedure: The detailed synthetic routes of the host molecule m-TPEWP5 and guest molecule G are shown in Scheme S1 and Scheme S2.

Synthesis of m-TPEWP5.
m-TPEWP5 was synthesized according to our previously reported procedures (Scheme S1).
The characterization data can be found in our previous work. [S1] Scheme S1: Synthetic route of m-TPEWP5

Synthesis of compound G [S2]
A mixture of benzoyl-L-alanine (100 mg, 0.00241 mmol) and excess NH 3 ·H 2 O (25.0 mL, 7.0 mol) was stirred at room temperature for 6 h. The solvent was evaporated under reduced pressure and the residue was dried in vacuum. The product was obtained as a white solid

Determination of the association constant (Ka) for m-TPEWP5  G
To determine the association constant between m-TPEWP5 and G, UV-vis measurements were carried out in solutions, which had a constant concentration of m-TPEWP5 (0.1 mM) and varying concentrations of G. By a linear curve-fitting method, the association constant between the G and m-TPEWP5 was calculated. The linear curve-fitting was based on the following equation [S3] Benesi-Hildebrand equation for the 1:1 stoichiometric ratio Here, A 0 , A, and A′ are represented as the absence, presence and saturated absorption of guest

Investigation of the FRET efficiency in m-TPEWP5⊃G assembly Energy-transfer efficiency calculation
The energy-transfer efficiency (Ф ET ) was calculated from excitation fluorescence spectra

Photocatalytic debromination reactions based on m-TPEWP5⊃G+EsY
assembly Method 1: Since the formed nanorod assembly is water-soluble, hence, CDCl 3 was selected to extract the product and substrate from the reaction solution after the completion of reaction. In this way, it contains the characteristic peaks of Hantzsch ester and DIPEA, but we only selected the -CH 3 of the product and the -CH 2 of the substrate for calibration. And relative measurements were used to calculate yields: = 1 1 1 1 + 2 2 % Here, A 1 is the integral area of the product -CH 3 , n 1 is the number of protons in the characteristic peak of the product, A 2 is the integral area of the substrate -CH 2 , n 2 is the number of protons in the characteristic peak of the substrate.

Method 2:
Since the formed nanorod assembly is water-soluble, hence, CDCl 3 was selected to extract the product and substrate from the reaction solution after the completion of reaction. The signal peaks of 1,3,5-trimethoxybenzene in 1 H NMR are strong and do not overlap with the product peaks. Therefore, this compound was selected as an internal standard and added into the reaction mixture. We only selected the -CH 3 of the product and the -OCH 3 of the internal standard for calibration. The ratio between product and internal standard: r A/Is = 1 1 2 2 , n IS = can be obtained by weighing a certain amount of internal standard. Then, the following equation was used to calculate the exact data. n A = n IS ⋅r A/IS Finally, the yield of the product was obtained by using the following equation: η= ℎ % Here, B 1 is the integral area of the product -CH 3 , m 1 is the number of protons in the S9 characteristic peak of the product, B 2 is the integral area of the internal standard -OCH 3 , m 2 is the number of protons in the characteristic peak of the internal standard. m IS is the weight of internal standard, M IS is the relative molecular mass of internal standard, n th is theoretical yield of product 2a (0.1 mmol).