Effect of Crown Ethers on the Ground and Excited State Reactivity of Samarium Diiodide in Acetonitrile

Abstract

Electron transfer from the ground and excited states of Sm[15-crown-5](2)I(2) complex to a series of electron acceptors (benzaldehyde, acetophenone, benzophenone, nitrobenzene, benzyl bromide, benzyl chloride, 1-iodohexane, and 1,4-dinitrobenzene) was investigated in acetonitrile. Electron transfer from the ground state of the Sm(II)-crown system to aldehydes and ketones has a significant inner sphere component indicating that the oxophilic nature of Sm(II) prevails in the system even in the presence of bulky ligands such as 15-crown-5 ether. Activation parameters for the ground state electron transfer were determined, and the values were consistent with the proposed mechanistic models. Since crown ethers stabilize the photoexcited states of Sm(II), the photochemistry of Sm[15-crown-5](2)I(2) system in solution state has been investigated in detail. The results suggest that photoinduced electron transfer from Sm(II)-crown systems to a wide variety of substrates is feasible with rate constant values as high as 10(7) M(-1) s(-1). The results described herein imply that the present difficulty of manipulating the extremely reactive excited state of Sm(II) in solution phase can be overcome through stabilizing the excited state of the divalent metal ion by careful design of the ligand systems.

Reversed Electron Apportionment in Mesolytic Cleavage: The Reduction of Benzyl Halides by SmI2

“…In most of the papers reporting the reaction of SmI 2 with benzyl halides, the benzylic system was used as a model or a vehicle to explore the landscape of SmI 2 capabilities. A number of examples of these are the lifetime of excited SmI 2 ,6 the issue of inner sphere versus outer sphere electron transfer,7 as a mechanistic probe for the reactions of SmI 2 –water,8 the effect of crown ethers on SmI 2 reactions,9 the effect of water,10 glyme,11 hexamethylphosphoramide (HMPA)12 and so on.…”

Tools and techniques for solution‐phase structural understanding of SmI2–additive complexes

“…Indeed, more recent studies indicated that crown ethers have preferences for +2 state over +3 and, as a result, these ligands act as a stabilizer to divalent state. [ 16 ]…”

Multifunctional membranes based on photosensitive crown-ether derivatives with advanced properties

“…Moreover, the numerous works concerning self-assembled monolayers of macrocyclic complexes with inorganic and organic molecules and ions have been published recently by various research groups worldwide [38][39][40][41]. The numerous crown-containing compounds with various substituents are promissing for application in molecular devices [42], chromatography [43], catalysis [44,45], biomedical fields [46,47], photovoltaics [48,49], hybrids [50,51] and special [52][53][54] materials. …”