Discrete Ti-O-Ti Complexes: Visible-Light-Activated, Homogeneous Alternative to TiO 2 Photosensitisers.

Autor: Behm K; Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK., Fazekas E; Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK., Paterson MJ; Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK., Vilela F; Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK., McIntosh RD; Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
Jazyk: angličtina
Zdroj: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2020 Aug 03; Vol. 26 (43), pp. 9486-9494. Date of Electronic Publication: 2020 Jul 09.
DOI: 10.1002/chem.202001678
Abstrakt: A series of novel bimetallic Ti IV amine bis(phenolate) complexes was synthesised and fully characterised. X-ray crystallography studies revealed distorted octahedral geometries around the Ti centres with single or double oxo-bridges connecting the two metals. These robust, air- and moisture-stable complexes were employed as photosensitisers generating singlet oxygen following irradiation with visible light (420 nm) LED module in a commercial flow reactor. All five complexes showed high activity in the photo-oxygenation of α-terpinene and achieved complete conversion to ascaridole in four hours at ambient temperature. The excellent selectivity of these photosensitisers towards ascaridole (vs. transformation to p-cymene) was demonstrated with control experiments using a traditional TiO 2 catalyst. Further comparative studies employing the free pro-ligands as well as a monometallic analogue highlighted the importance of the 'TiO 2 -like' moiety in the polymetallic catalysts. Computational studies were used to determine the nature of the ligand to metal charge transfer (LMCT) states and singlet-triplet gaps for each complex, the calculated trends in the UV-vis absorption spectra across the series agreed well with the experimental results.
(© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)
Databáze: MEDLINE
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