High Reactivity of Heterocoerdianthrones (HCDs) in Photoperoxidation and Thermal Stability of Their Endoperoxides. Use of HCD as a Photosensitizer under Sunlight

Abstract

The measured reactivity indices (β-values) of heterocoerdianthrones (HCDs) in self-sensitized photoperoxidation indicate a high reactivity toward singlet-oxygen. Such a high reactivity is not only due to an effective singlet-oxygen production due to the highly fluorescent character, but also due to a strained structure, as predicted by a molecular calculation. On the other hand, the large thermal stability of their endoperoxides (POs), revealed by the large activation energy in thermal decomposition, is also explained by considering the strained structure of the parent HCDs. As a prospect of solar synthesis, one of the HCD derivatives was applied to a photosensitizer for singlet-oxygen oxidation.

Tetraphenylporphine-Sensitized Photooxygenation of (E,E)- and (E,Z)-1-Aryl-1,3-pentadienes Generating cis-Endoperoxides

“…Chemically generated singlet oxygen from (PhO) 3 P−O 3 complex or hypochlorite−hydrogen peroxide partially led to isomerization of 1a , decreasing the ( E,Z )/( E,E ) ratio of 86/14 to 60/40 and 62/38, respectively, with loss of a certain amount of the diene. On the other hand, quinonoid sensitizers such as rose bengal and a heterocoerdianthrone having lower oxidation potentials rapidly decreased the ratio to 20/80 and 22/78, respectively, under a nitrogen atmosphere (for 1 h), but TPP did not change the ratio for itself . No mechanistic conclusion can be drawn from these experiments at present but some comments can be given that rapid photoinduced isomerization is induced in the presence of both TPP and singlet oxygen or sensitizers with low oxidation potentials.…”

Transient Formation of Hydrogen Tetraoxide from Hydrogen Peroxide with Bis(trifluoroacetoxyiodo)benzene: A Chemical Generator of Singlet Oxygen for Organic Synthesis.

“…In view of the product selectivity and discrimination between aromatization and peroxidation of a given substrate with this present system a-terpinene 1 serves as a diagnostic tool. The 1 H NMR spectrum recorded after the oxidation of aterpinene 1 with PIFA-H 2 O 2 proves the disappearance 1 and confirms the formation of ascaridole 2 9 and p-cymene 3. In view of the solvent effect, four different solvents were selected for a screening of the product distribution: THF, acetone, dichloromethane and carbon tetrachloride.…”

Photo-induced Aggregation of Single-walled Carbon Nanotubes from Dispersion by Using a Photochromic Dispersant

“…1. The twisted angle between the moieties in HCDPO has been estimated to be about 55.5˚, in contrast to the 19.2˚ angle in HCD [18]. The bent structure and reduced π-conjugation are expected to induce a break of π-π stacking between HCD derivatives and CNTs or graphenes.…”

“…The DPHCD (dipropyldibenzo[a,j]perylene-8,16diones) was prepared from anthraquinone-1, 5dicarbonyl dichloride and the propylbenzene with aluminum chloride in nitrobenzene in accordance with the literature [18,19,23]. The product was purified as follows.…”

“…Heterocoerdianthrone (dibenzo[a,j]perylene-8,16 -dione) (HCD) and its derivatives are well known as components in photo-reversible systems between the visible and ultraviolet regions. They are capable of forming endoperoxides (HCDPOs), which have significant thermal stability [18,19]. In this photochromic reaction, singlet oxygen ( 1 O 2 ) is initially generated by the triplet sensitization reaction of HCD [20].…”