Over the last 10 years we have serendipitously made several interesting discoveries which have been fully studied in the following cases, especially within the photochemistry area.
Electrocylisation / oxidative aromatisation: Stoichiometric intermolecular Pauson-Khand reactions of 4-(phenylethynyl)-6-methyl-2-pyrones with norbornene and dicobalt(0) octacarbonyl provide cyclopentenone products that undergo a facile 6pi-electrocyclisation / oxidative aromatisation transformation in the presence of natural light and oxygen, affording functionalised benzoindeno [1,2-f]isochromene type products.
The experimental results were rationalised by theoretical studies, which confirm that the electrocyclisation process is favoured at C3 in the 2-pyrone ring system.
The identity and precise arrangement of the ‘trienyl’ substituents controls whether the electrocyclisation occurs in natural light.
Figure: Electrocyclisation and oxidative aromatisation of a Pauson-Khand product containing a 2-pyrone motif.
Figure: The highest occupied molecular orbital (HOMO) of the conformer leading to the C3-electrocyclisation product.
Atropisomerisation: Whilst studying PK reactions of a variety of push-pull internal alkynes we noted that sterically hindered alpha,beta-(2,3-) disubstituted cyclopentenone regioisomeric products exhibit pronounced atropisomerisation - the magnitude of the energetic barrier to interconversion between these atropisomers is dependent on the relative position of the coumarin moieties.
Figure: Atropisomerisation in Pauson-Khand products.
Figure: Variable temperature 1H NMR spectroscopy reveals the presence of two atropisomers for the beta-cycloadduct.
Nitrite-Nitro metal complexes: In collaboration with Paul Raithby (Bath) we have discovered the first 'Pd-NO2' to 'PdONO' linkage isomerisation, which is affect both photochemically and thermally.
Solid-state cycloaddition chemistry: We have become aware of [2+2] cycloaddition chemistry in the solid-state involving substituted dibenzidence acetone compounds containing phosphine sulphide moieties.
CO-releasing molecules requiring photochemical irradiation: We have developed two manganese(I) carbonyl systems as potential photo-CORMs. Both photo-CORMs exhibit useful CO-release profiles and excellent cell viability.
Chemical structure of JW-2.
Graph showing photochemical irradiation (LED) of JW-2, and subsequent uptake of CO by deoxy-myoglobin, switching through on-off cycles.
Graph showing photochemical irradiation (LED) of Trypto-CORM, and subsequent uptake of CO by deoxy-myoglobin.