Quantitative Supramolecular Heterodimerization for Efficient Energy Transfer

Abstract The challenge of quantitatively forming self‐assembled heterodimers without other equilibrium by‐products is overcome through self‐sorting favored by the introduction of designed shape‐complementary moieties. Such a supramolecular strategy based on cucurbit[8]uril‐directed dimerization is further applied to generate hetero‐chromophore dimers quantitatively, leading to efficient energy transfer (>85 %) upon photoexcitation.


High Pressure Liquid Chromatography (HPLC).
HPLC was employed to purify and collect dicationic species by using a 150 x 21.2 mm Phenomenex C18 Kinetic-Evo column with a 5 micron pore size and a 110 Å particle size. A gradient from 5% acetonitrile 95% water to 100% acetonitrile was used with 0.1% TFA. 1 H NMR, 13 C NMR, COSY, DOSY, ROESY, and NOESY spectra were acquired in heavy water (D2O) and recorded on a Bruker AVANCE 500 with TCI Cryoprobe system (500 MHz) being controlled by TopSpin2. NOESY experiments were carried out using a standard pulse sequence 'noesygpphpp' with a 2 s relaxation delay and a 1000 ms mixing time. The concentration of CB[8] or CB [7] deuterated aqueous solution was calibrated by an internal standard: DSS sodium salt. ROESY experiments were carried out using a modified EASY ROESY pulse sequence 'roesyadjsphpr' with a 2 s relaxation delay and 200 ms mixing time. 1 H NMR spectra with variable temperature were recorded by a Bruker AVANCE 500 with TCI Cryoprobe system (500 MHz).

Diffusion Ordered Spectroscopy (DOSY).
The 1 H DOSY experiments were carried out using a modified version of the Bruker sequence ledbpgp2s involving, typically, 32 scans over 16 steps of gradient variation from 10% to 80% of the maximum gradient. Diffusion coefficients were evaluated in Dynamic Centre (a standard Bruker software) and determined by fitting the intensity decays according to the following equation: where I and Io represent the signal intensities in the presence and absence of gradient pulses respectively, D is the diffusion coefficient, = 26753 rad/s/Gauss is the 1 H gyromagnetic ratio, δ = 2.4 ms is duration of the gradient pulse, Δ = 100 ms is the total diffusion time and g is the applied gradient strength. The Monte Carlo simulation method was used for the error estimation of fitting parameters with a confidence level of 95%.

UV/Vis Spectroscopy and Fluorescence Spectroscopy.
UV/Vis and fluorescence spectra were recorded on a Varian Cary 400 UV/Vis spectrophotometer and Varian Cary Eclipse fluorescence spectrophotometer, respectively, using a Hellma 114F-QS cuvette with 10x4 mm path length at 298 K.

Electrospray Ionization Mass Spectrometry (ESI-MS).
ESI-MS spectra were acquired on a Thermo Fisher Q Exactive Orbitrap mass spectrometer with a nanospraying ion source. Positive mode was chosen for all the experiments with the working temperature of 320 °C and the capillary voltage of 1.5 kV. All the sample solutions were prepared in pure water.
Scheme S1. Molecules related to this work (Counter anion is Cl -).