Fairlamb Research Group

Catalysis, Synthetic and Mechanistic Chemistry

Photochemistry

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.

Lead reference:

Org. Biomol. Chem. 2008, 6, 4523.


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. 

Lead reference: 

Org. Biomol. Chem. 2010, 8, 5398.



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.  

Lead reference:

Chemical Science, 2012, 3, 1656-1661.


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. 

Lead reference:

CrystEngComm 2012, 14, 5564-5571.




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. 

Lead references: 

Chem. Eur. J. 2014, 20, 15061.

Dalton Trans. 2012, 41, 10514.


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.

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