Theoretical studies of a singlet oxygen-releasing dioxapaddlane (1,4-diicosa naphthalene-1,4-endoperoxide)

Abstract

Theoretical calculations have been used to examine singlet oxygen release from a naphthalene endoperoxide which bears a flexible (CH2)22 polymethylene “lid”. Monte Carlo and ONIOM calculations that incorporated semi-empirical and density functional theory predicted the conformational influence of the polymethylene chain in the cycloreversion of dioxapaddlane, 1,4-diicosa naphthalene-1,4-endoperoxide, to 1O2 and 1,4-diicosa naphthalene. This study attempts to build a connection between 1O2 generation and “jump rope” dynamics of the dioxapaddlane. The polymethylene chain appears to function as a gatekeeper for the oxygen. Instead of coming full circle, a semi-circle rotation of the polymethylene bridge protected the peroxide group, limiting the dissociation of 1O2 from the naphthalene site.

Internal and External Stereoisomers of Squaraine Rotaxane Endoperoxide: Synthesis, Chemical Differences, and Structural Revision

“…The relative strain was analyzed by comparing the dihedral angle (φ) formed by the planes of the two aryl rings in the anthracene-9,10-endoperoxide moieties. In the case of the two int stereoisomers, the φ values of 124.1° for SREP-int and 120.2° for 1EP are quite similar and correlate with a relatively unstrained anthracene-9,10-endoperoxide system. , With the two ext stereoisomers, the φ value of 136.3° for 1EP reflects moderate strain of the anthracene-9,10-endoperoxide section, and the φ value of 152.4° for SREP-ext indicates significantly higher strain induced by the encapsulated squaraine dye . These results are consistent with the finding that the endoperoxide carbon–oxygen bonds are elongated by 0.2 Å in SREP-ext compared to SREP-int .…”

Probing the reactivity of singlet oxygen with purines

“…Downhill, our calculations confirm the experimental fact that the degradation cascade which starts from the endoperoxide 3 is most likely to continue the 4-hydroxy-8-oxo-2′-deoxyguanosine 4 . Stabilization energy accounts for 86.4 kcal mol −1 (Figure 2 ), a considerable exothermicity due to a release of the conformational strain of the endoperoxide ( 33 ), reflected in the lenghtening of the C8-O1 bond from 1.35 to 1.44 Å, and an increase of conjugation along the π-system. The rate-limiting step is found to be the opening of the endoperoxide (Figure 6 ) that implies a high-energy transition state situated at ca.…”