73605-96-6Relevant academic research and scientific papers
Photoredox Reactions in Functional Micellar Assemblies. Use of Amphiphilic Redox Relays To Achieve Light Energy Conversion and Charge Separation
Brugger, Pierre-Alain,Infelta, Pierre P.,Braun, Andre M.,Graetzel, Michael
, p. 320 - 326 (1981)
The photoreduction of a homologous series of amphiphilic viologens (CnMV2+) using Ru(bpy)32+ and zinc tetrakis(N-methylpyridyl)porphyrin (ZnTMPyP4+) as sensitizers (S) was studied in water and aqueous solution containing cationic micelles.S + CnMV2+ (*) S+ + CnMV+ Here, CnMV2+ stands for N-alkyl-N'-methyl-4,4'-dipyridinium dichloride (alkyl = dodecyl (C12MV2+), tetradecyl (C14MV2+), hexadecyl(C16MV2+), and octadecyl (C18MV2+)).The forward electron transfer occurs with the viologen present in the aqueous phase.Upon reduction the relay acquires hydrophobic properties leading to rapid solubilization in the micelles.The subsequent thermal back-reaction is impaired by the positive surface potential of the aggregates.This decreases the rate constant for the electron back-transfer at least 500-fold.The stabilization and yield of redox products are optimal in a system containing ZnTMPyP4+ as the sensitizer, C14MV2+ as a relay, and cetyltrimethylammonium chloride micelles.A kinetic model is presented to explain the effects observed, and implications for energy conversion systems are discussed.
The Role of Chain Length in Cucurbit[8]uril Complexation of Methyl Alkyl Viologens
Pedrini, Alessandro,Devi Das, Anjali,Pinalli, Roberta,Hickey, Neal,Geremia, Silvano,Dalcanale, Enrico
, p. 1547 - 1552 (2021)
Viologens are among the most studied guests for cucurbit[8]uril (CB[8]) and their complexation is usually driven by bipyridyl core inclusion inside the cavity to maximize both hydrophobic and cation-dipole interactions. The presence of alkyl substituents on the guest alters this complexation mode, switching to aliphatic chain inclusion in U-folded conformation. Herein, we report a thorough study of the influence of the alkyl chain length on the binding mode of methyl alkyl viologens. The chain length of the studied guests was increased by two methylene groups starting from methyl dodecyl viologen (MVC12) to the octadecyl analogue (MVC18). Complexation in water, investigated by NMR spectroscopy and ITC, revealed a clear switch from 1 : 1 to 2 : 1 host/guest stoichiometry moving from 12 to 16 carbon atoms, as a consequence of the chain folding of the major portion of the longer alkyl chain in one CB[8] cavity and the inclusion of the full viologen unit by another host molecule. The CB[8]2.MVC18 complex crystal structure evidences the unprecedented 2 : 1 stoichiometry and quantified in 12 the number of carbon atoms necessary to fill the CB[8] cavity in U-shaped conformation.
