New Persistent Radicals:  Synthesis and Electronic Spin Structure of 2,5-Di-tert-butyl-6- Oxophenalenoxyl Derivatives

New Stable Neutral Radical with Intramolecular Hydrogen Bonding: Synthesis and Characterization of 2,5,8-Tri-tert-butyl-7-hydroxy-6-oxophenalenoxyl

“…First, Figure 3 shows the π-spin density distribution of the two possible tautomeric isomers correlated with 2ba, 2ab, as well as 2 •• and 6-oxophenalenoxyl 1. 4 In the case of 2aa, the calculated result gave the same π-spin density distribution as that of 2ba. The relative signs of the π-spin densities on C3, C4, and C9 in 2ba, 2ab, and 2 •• are equal in accord with the experimental result, which does not serve to distinguish between the structures.…”

“…Such an extensively delocalized nature of the unpaired electron over the phenalenyl skeleton and two oxygen atoms contributes to the stability of this radical in addition to the steric effect of tert-butyl substituents. 4,14,15 In conclusion, we have efficiently synthesized and characterized a new type of neutral radical 2. The crystalline solid of 2 can survive for a few weeks under atmospheric oxygen at room temperature.…”

“…In the 1 H NMR spectrum in CDCl 3 measured at room temperature, dihydroxyphenalenone 3 shows only three C-H broad signals in the aromatic region, indicating the reversible exchange of the O-H protons by the tautomeric behavior, which was also observed in 6-hydroxyphenalenone derivatives. 4 In the IR spectra, compound 3 shows absorption bands at nearly the same frequencies within a resolution of 4.0 cm -1 in the solid (KBr) state (1629 and 1589 cm -1 ) and in a dilute solution (CCl 2 CCl 2 , 1 × 10 -3 M, 1629 and 1589 cm -1 ) (Figure 1 A,B). These absorption bands are assigned to Cd O and CdC stretching vibrations, respectively.…”

Phenalenyls, Cyclopentadienyls, and Other Carbon‐Centered Radicals

“…42 The tert-butyl group, sterically more congested group than methyl group, greatly improves the stabilities of 4OPO and 6OPO, enabling them to be handled in air. 35,43 Taking advantage of this strategy, 7-hydroxy-TB6OPO was also designed and synthesized as the first neutral radical having an intramolecular hydrogen bond coupled with an extremely delocalized spin system. 44 These neutral radicals were prepared by the methods depicted in Scheme 3.10.…”

Spin–spin interaction between phenoxyl radicals through σ–π system

“…3,5-Di-tert -butyl-4-trimethylsiloxyphenyllithium and 3-and 4-(3,5-di-tertbutyl-4-trimethylsiloxyphenyl)phenyllithium were prepared by treating the corresponding aryl bromides with one equivalent of n -butyllithium. For oxidation of precursors leading to phenoxyl radicals, freshly prepared PbO 2 must be used [10]. Commercially available PbO 2 did not react with the precursors at all.…”