ESR spectroscopy of some dicyano‐, pyrazino‐ and quinoxalino‐1,3,2‐dithiazolyl radicals

Abstract

Several symmetrical 1,3,2dithiazoI-2-yl radicals have been examined that have in common nitrogen-containing substituents a t the 4-and 5-positions, namely 4,5-dicyano-l,3,2-dithiazol-2-yl, 1 "N, I-l,3,2-dithiazolo [4,5-61 pyrazin-2-yl and 1,3,2-dithiazoleo 14,541 quinoxalin-2-yl. The ESR spectrum of the 4,Sdicyano radical does not reveal any "N splittings from the cyanide groups; however, the pyrazine and the quinoxaline derivatives do have multi-lined well resolved spectra arising from substantial hypefine interactions with these nuclei. The interactions are sufficiently large to be observed in the powder spectra of the latter. The presence of proton hyperfine interactions shows that unpaired-electron spin density is delocalized over all the rings. It has been found that the radicals attached to pyrazine and quinoxaline can be incorporated into single crystals of naphthalene and phenazine, respectively.

Theoretical Analysis of Heteroaromatic Thioaminyl Radicals. Part 1: A Comparison of Ab Initio and Density Functional Methods in Calculations of Molecular Geometry and Isotropic Hyperfine Coupling Constants

“…The generally excellent performance of the DFT methods in reproducing experimental hfcc allows for critical examination of some cases where either the hfcc or structural assignments are ambiguous. For instance, the DFT calculations consistently indicate that the 1 H hfcc in 9i might be misassigned, as is shown in Figure . Simply switching the positions of the hydrogen atoms gives a much better correspondence between the experimental and calculated values.…”

“…In almost all heterocyclic radicals studied to date, the thioaminyl fragment is a part of a longer, three- or four-membered array of heteroatoms such as −N−S−S−N− ( 1a , 1b , 1c , 1d , 1e , , 1g , ), −N−S−N−S− ( 2d , ), −N−S−N− ( 4c , 4e , 4g , 5 , 10 ), −S−N−S− ( 3a , , 3e , 3f , , 5 , 6h , , 6i , 9h , 9i , 10 64 ), and −N−S−S− ( 7h , , 7i , 11 6 ), as shown in Figure . Radicals containing the −S−N− fragment connected directly to the carbon framework are rare, and 8 as well as two compounds recently reported by us 23 are the only examples.…”

Poly-sulfur-nitrogen heterocycles via sulfur chlorides and nitrogen reagents

“…Reaction of 51 with ammonia, followed by treatment with potassium ferricyanide, gave the quinoxaline-1,3,2-dithiazolyl radical 52 [35]. Its ESR spectrum was studied [36]. The air stable radical 52 did not dimerise; nor did the air unstable 2,3-naphthalene-1,3,2-dithiazolyl radical 53, prepared from naphthalene-2,3-bis(sulfenyl chloride) in the usual manner [37].…”

A multinuclear NMR study of the cycloaddition reaction of SNSAsF6withtert-butylphosphaacetyline (CH3)3CCP leading to the 5-tert-butyl-1,3,2,4-dithiazaphospholium cation; a preliminary account of the novel exchange of a cyclic phosphorus by nitrogen in the reaction of with azide N3−leading to 5-tert-butyl-1,3,2,4-dithiadiazolyl

“…However, reactions of SNS' with double bonds may be expected to be more complex than those with triple bonds, as the reactions of SNS' with olefins form a mixture of 1:l and 2: 1 olefin-SNS' cycloadducts in liquid SO, at room temperature or lower (lc, 2). In addition, the claim has been made (4) n for the preparation of (CH3),CCPSNSAsF6 on the basis that a radical was produced on the reduction of the isolated salt, n which was attributed to (CH,),CCPSNS'. However, no direct -evidence was given for the ( C H~) , C~P S N~?…”

“…+ 0.03 mT) of the nonconjugated radicals in which the two sulfurs are bonded to a saturated moiety (Table 1). Therefore, n the identity of this radical is very likely not (CH,),CCPSNS' as proposed (4). In this work, an attempted generation of the 5-n tert-butyl-l,3,2,4-dithiazaphospholyl (CH,),CCPSNS' radical was carried out by in situ reduction of ( c H ,…”