Contrasting Effect of Additives on Photoinduced Reactions of SmI2. Issue 44 (8th July 2019)

• Record Type: Journal Article
• Authors: Nimkar, Amey; Maity, Sandeepan; Flowers, Robert A; Hoz, Shmaryahu
• Is Part Of: Chemistry. Volume 25:Issue 44(2019)
• Page Start: 10499
• Page End: 10504
• Publication Date: 2019-07-08
• Subjects: electron transfer -- kinetics -- reaction mechanism -- reduction -- samarium; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201901997
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N ‐methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI2 ). In thermal reactions, additives that coordinate to SmI2 induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of Sm II by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism. Abstract : A diversified effect of coordinating additives was observed in photoinduced reductions mediated by SmI2 . Mechanistic studies indicated that inner sphere versus outer sphere electron transfer determines critical role of additives on the photoinduced reactions.