Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switchesElectronic supplementary information (ESI) available: Detailed synthetic, spectroscopic, photoswitching, kinetic data, X-ray structures and DFT modelling. CCDC 1839144-1839152. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc03218a

• Main Authors: Mallo, Neil, Foley, Eric D, Iranmanesh, Hasti, Kennedy, Aaron D. W, Luis, Ena T, Ho, Junming, Harper, Jason B, Beves, Jonathon E
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c8sc03218a

The first in-depth, systematic study of the photoswitching properties of Donor-Acceptor Stenhouse Adducts (DASAs) is reported. Barbituric acid derived DASAs functionalised with 14 different amines ranging from dimethylamine to 4-methoxy- N -methylaniline were structurally characterised in solution using 1 H and 13 C NMR spectroscopy and, in eight cases, in the solid state by single crystal X-ray diffraction. The distribution of coloured and colourless isomers in the dark, their photostationary states under irradiation, apparent thermal half-lives, and fatigue resistance are systematically compared. A simple kinetic model is used to characterise photoswitching behaviour and reveals that minor structural modifications can significantly improve the photoswitching properties of DASA photochromes. These modifications result in excellent photoswitching properties for '1 st generation' DASAs in chloroform, including exceptional fatigue resistance, opening the door for these photochromic molecules to find widespread applications. Surprisingly small structural changes in Donor-Acceptor Stenhouse Adducts (DASAs) result in predictable, robust and effective photochromic switches.