Absorption spectra of quinones. I. Naphthoquinones and naphthohydroquinones

Abstract

This paper reports the ultraviolet and visible absorption spectra of a number of derivatives of 1,4-naphthoquinone and 1.4-naphthohydroquinone. A statistical analysis of the spectra shows that the absorption bands of the quinones may be divided into three groups. Two of these groups contain absorption bands, the position of which is only slightly dependent upon the nature of the substituents. and which are characteristic of the class of the naphthoquinones. The bands of the third group, situated mainly in the visible and near ultraviolet, are determined by the structure of the molecule as a whole. It is shown by several examples that the wavelengths of bands from the last group increase when negative charge is introduced into the nucleus by the attachment of substitwnts able to donate electrons, such as hydroxy groups. The reverse holds for electron-attracting groups such as the carbonyl group.

Synthesis and Photochemical Properties of Fluorescent Metabolites Generated from Fluorinated Benzoylmenadiones in Living Cells

“…, with GSH, the thioether adduct 2-methyl-3-glutathionyl-1,4-naphthoquinone is also termed thiodione, Figure ) that displays emission maxima at 480 (λ exc = 340 nm) and 420 nm (λ exc = 360 nm) for cysteine and glutathione, respectively . In the absence of biological thiols, electrochemical or photochemical reduction of menadione also generate a fluorescent dihydronaphthoquinone species emitting at much higher energies (λ em = 420 nm) upon excitation at 309 nm. , …”

“…described in the literature or in this study, the reduced naphthoquinone derivatives thus unambiguously correspond to the emitting species. 52,56,57 The peculiar emission properties of F-PDO with or without thiols could be thus attributed to an excited-state intramolecular photoinduced transfer (ESIPT) mechanism 58 (keto−enol tautomerization, Figure 9) induced by the presence of the benzoyl moiety and the formation of strong hydrogen bonding between the dihydronaphthoquinone core and the acyl residue (Figure 9). This ESIPT process can be influenced by the nature of the solvent and has been described for closely related chemical structures such as orthohydroxy-acetophenone and derivatives, 59,60 2,5-dihydroxyacetophenone, 61 or 1-hydroxy-2-acetonaphthone, 62−65 to cite a few (Figure 9).…”

“…51 In the absence of biological thiols, electrochemical or photochemical reduction of menadione also generate a fluorescent dihydronaphthoquinone species emitting at much higher energies (λ em = 420 nm) upon excitation at 309 nm. 44,52 From the viewpoint of organic synthesis, a visible-lightinduced thiolation of substituted 1,4-naphthoquinones was recently developed using various thiol derivatives and eosin as the photoredox catalyst. 53 On the other hand, α-selective Csp 3 −H bond functionalization of primary aliphatic alcohols with 1,4-naphthoquinones driven by blue LED light irradiation in the absence of a catalyst, metal, base, or reagent afforded a large series of 2-acylated-1,4-naphthohydroquinones that were shown to display a fluorescent signal in the visible region (Figure 7).…”