Bambusuril as a One-Electron Donor for Photoinduced Electron Transfer to Methyl Viologen in Mixed Crystals

Abstract

Methyl viologen hexafluorophosphate (MV·2PF) and dodecamethylbambus[6]uril (BU6) form crystals in which the layers of viologen dications alternate with those of a 1:2 supramolecular complex of BU6 and PF. This arrangement allows for a one-electron reduction of MV ions upon UV irradiation to form MV radical cations within the crystal structure with half-lives of several hours in air. The mechanism of this photoinduced electron transfer in the solid state and the origin of the long-lived charge-separated state were studied by steady-state and transient spectroscopies, cyclic voltammetry, and electron paramagnetic resonance spectroscopy. Our experiments are supported by quantum-chemical calculations showing that BU6 acts as a reductant. In addition, analogous photochemical behavior is also demonstrated on other MV/BU6 crystals containing either BF or Br counterions.

Bambusuril Anion Receptors

“…Figure 7. [43] A similar type of complex was also described for (Bn)BU [6] and benzoate and tosylate anions ( Figure 8C). [30] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 (Bn)BU [6] and chloride, [27] (Bn)BU [6] and dialkyl phosphate, [26] and between (Me)BU [6] and PF 6 À .…”

Photoinduced Electron Transfer Switching Mechanism of a Naphthalimide Derivative with its Solvatochromic Behaviour: An Experimental and Theoretical Study with In Cell Investigations

“…However, in the presence of the guest ion, the lone pair of the donor amine group is engaged, which leads to considerable enhancement in the emission intensity of the fluorophore by turning off the photoinduced electron transfer (PET) process. This property constitutes the actuating mechanism of these molecules to be functioning as sensors . Panchenko et al.…”

Size‐Control by Anion Templating in Mechanochemical Synthesis of Hemicucurbiturils in the Solid State

“…While mechanosynthesis of self-assembled coordination and covalent rings and cages has been reported, [6] so far there has been no investigation on how such transformations might be facilitated or directed by molecular templates. [13] Thesynthesis of cyclohexanohemicucurbiturils (cycHC[n]) [10a,b] is based on reversible formation of methylene linkages between ethylene urea monomers and formaldehyde under highly acidic conditions,a nd has emerged as ar obust thermodynamically driven anion-templated reaction of dynamic covalent chemistry (DCC) [14] in solution. [13] Thesynthesis of cyclohexanohemicucurbiturils (cycHC[n]) [10a,b] is based on reversible formation of methylene linkages between ethylene urea monomers and formaldehyde under highly acidic conditions,a nd has emerged as ar obust thermodynamically driven anion-templated reaction of dynamic covalent chemistry (DCC) [14] in solution.…”

“…Attempts to follow solid-state formation of cycHC[6] and cycHC[8] in situ by PXRD were not successful because of the difficulty in maintaining ac ontrolled environment of acid, temperature,a nd humidity.I nstead, real-time monitoring [21] was conducted by 13 Ccross-polarization magic angle spinning (CP-MAS) solid-state NMR (SSNMR) spectroscopy.F or this purpose,s olid powders obtained by 30 minute milling of equimolar amounts of 1 and (CH 2 O) n with either aqueous HCl or HClO 4 were packed into SSNMR zirconia rotors,and spectra acquired at fixed time intervals:every 30 minutes for the synthesis of cycHC[6] and every 3.75 minutes for cycHC[8] (see Figures S18 and S19).…”

“…[22] As ar esult, no signal was observed at the outset of CP-MAS monitoring,b ut as the aging proceeded 13 Therate of formation of cycHC[8] is k = 1.47 AE 0.38 10 À3 s À1 , an order of magnitude higher than that for cycHC [6]. [22] As ar esult, no signal was observed at the outset of CP-MAS monitoring,b ut as the aging proceeded 13 Therate of formation of cycHC[8] is k = 1.47 AE 0.38 10 À3 s À1 , an order of magnitude higher than that for cycHC [6].…”