1. Effect of Iodination on the Photophysics of the Laser Borane anti-B18H22: Generation of Efficient Photosensitizers of Oxygen
- Author
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Lenka Slusna, Daniel Roca-Sanjuán, Jiří Dolanský, Antonio Francés-Monerris, Jonathan Bould, Kaplan Kirakci, Pavel Kubát, Dusan Lorenc, Ivana Císařová, Eva Noskovicova, Kamil Lang, Michael G. S. Londesborough, and Jakub Braborec
- Subjects
010405 organic chemistry ,Singlet oxygen ,Nuclear magnetic resonance spectroscopy ,Borane ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Yield (chemistry) ,Physical and Theoretical Chemistry ,Spectroscopy ,Phosphorescence ,Derivative (chemistry) ,Dichloromethane - Abstract
Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both compounds 2 and 3 give strong green phosphorescent emissions (λmax = 525 nm, ΦL = 0.41 and λmax = 545 nm, ΦL = 0.71 respectively) that are quenched by dioxygen to produce O2(1Δg) singlet oxygen with quantum yields of ΦΔ = 0.52 and 0.36 respectively. Similarly strong emissions can be stimulated via the nonlinear process of two-photon absorption when exciting with 720 or 800 nm light. The high quantum yields of singlet-oxygen production, coupled with the option of two-photon excitation, make compounds 2 and 3 promising O2(1Δg) photosensitizers. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray crystallographic studies as well as multinuclear NMR spectroscopy and mass spectrometry. Time-resolved UV-vis spectroscopy was used to delineate their photophysical properties, and the electronic-structure properties of the emitting species were determined by means of multiconfigurational quantum-chemistry computations.
- Published
- 2019