Chloride, Bromide, and Iodide Photooxidation in Acetonitrile/Water Mixtures Using Binuclear Iridium(III) Photosensitizers
(2023) Inorganic Chemistry — Vol. 62, n° 39, p. 16196-16202 (2023)
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- Two iridium(III) binuclear photosensitizers, [Ir(dFCF3ppy)2(N–N)Ir(dFCF3ppy)2]2+, where N–N is tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2‴,3‴-j]phenazine (Ir-TPPHZ) and 1,4,5,8-tetraazaphenanthrene[9,10-b]-1,4,5,8,9,12-hexaazatriphenylene (Ir-TAPHAT) are reported for iodide, bromide, and chloride photooxidation in acetonitrile and acetonitrile/water mixtures using blue-light irradiation. Excited-state reduction potentials Ered* of +2.02 and +2.09 V vs NHE were determined for Ir-TPPHZ and Ir-TAPHAT, respectively. Both photosensitizers’ excited states were efficiently quenched by iodide, bromide, and chloride with quenching rate constants in the (3.5–9.2) × 1010 and (0.0036–2.9) × 1010 M–1 s–1 ranges in neat acetonitrile and acetonitrile/water mixtures, respectively. Nanosecond transient absorption spectroscopy provided unambiguous evidence of reductive excited-state electron transfer, with all halides in the solvent mixtures containing up to 50% water. Cage-escape yields were large (55–96%) in acetonitrile and dropped below 32% in 50:50 acetonitrile/water mixtures.
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De Kreijger, S., Elias, B., & Troian-Gautier, L. (2023). Chloride, Bromide, and Iodide Photooxidation in Acetonitrile/Water Mixtures Using Binuclear Iridium(III) Photosensitizers. Inorganic Chemistry, 62(39), 16196-16202. https://doi.org/10.1021/acs.inorgchem.3c02648 (Original work published 2023)