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Rates of Ring Opening of Radical Cation Intermediates Govern Differences in Thermoluminescence between 1‐ and 2‐Naphthyl‐Substituted Methylenecyclopropanes
Author(s) -
Matsui Yasunori,
Shimono Kazuki,
Takae Kosuke,
Namai Hayato,
Sera Toshiki,
Ogaki Takuya,
Ohta Eisuke,
Mizuno Kazuhiko,
Ikeda Hiroshi
Publication year - 2020
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201900230
Subject(s) - methylenecyclopropane , chemistry , phosphorescence , trimethylenemethane , ring (chemistry) , thermoluminescence , fluorescence , photochemistry , geminal , crystallography , stereochemistry , cycloaddition , catalysis , materials science , luminescence , physics , optoelectronics , organic chemistry , biochemistry , quantum mechanics
In this study, we observed that methylenecyclopropane 1 c , possessing geminal phenyl and 1‐naphthyl groups at C‐2 of the three membered ring, emits green thermoluminescence (TL) in a low temperature matrix, associated with two sets of bands in the 480–600 and 600–700 nm regions. The bands are assigned to phosphorescence from 3 1 c * and triplet‐triplet (T−T) fluorescence (FL) from the corresponding trimethylenemethane biradical 3 2 c .. *, respectively. In contrast, as previously reported, the analogous 2‐naphthyl derivative 1 b emits red TL associated with two bands in the 350–450 and 600–700 nm regions, which are assigned to FL from 1 1 b * and T−T FL from 3 2 b .. *. The results of spectroscopic studies and density functional theory calculations show that the observed dissimilarity in the TL properties of 1 b and 1 c is a consequence of differences in the rate of methylenecyclopropane ring opening of 1 b .+ and 1 c .+ associated with stereoelectronic effects of the naphthyl groups.