Abstract
A series of novel bimetallic TiIV 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 in a commercial flow reactor. All five complexes showed high activity in the photooxygenation of α -terpinene and achieved complete conversion to ascaridole in four hours at ambient temperature. The excellent selectivity of these photosensitisers towards ascaridole ( vs. isomerisation to p -cymene) was demonstrated with control experiments using traditional a TiO2 catalyst. Further comparative studies employing the free pro-ligands as well as a monometallic analogue highlighted the importance of the 'TiO2 -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.
Original language | English |
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Pages (from-to) | 9486-9494 |
Number of pages | 9 |
Journal | Chemistry - A European Journal |
Volume | 26 |
Issue number | 43 |
Early online date | 19 May 2020 |
DOIs | |
Publication status | Published - 3 Aug 2020 |
Keywords
- amine bis(phenolate)
- flow chemistry
- photosensitiser
- singlet oxygen
- titanium
ASJC Scopus subject areas
- Catalysis
- Organic Chemistry
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Ruaraidh D. McIntosh
- School of Engineering & Physical Sciences - Assistant Professor
- School of Engineering & Physical Sciences, Institute of Chemical Sciences - Assistant Professor
Person: Academic (Research & Teaching)