Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

© The Royal Society of Chemistry 2018. Recent developments in super-resolution microscopy have significantly expanded the requirements for switchable dyes, leading to demand for specially designed molecular switches. We report the synthesis and characterization of a spironaphthoxazine photochromic switch (a derivative of palatinate purple) displaying high photoconversion (85-95%) under readily accessible 405 nm light, broad absorption in the visible, and excellent fatigue resistance. The indole substituent on this spironaphthoxazine is twisted out of conjugation with the naphthalene unit, yet it is crucial for activation with visible light. The open colored merocyanine form of the spironaphthoxazine reverts to the closed form with a lifetime of 4.7 s in dichloromethane at 20 °C; this thermal reversion is even faster in more polar solvents. The photochemical quantum yields for ring-opening and ring-closing are approximately 8% and 1%, respectively, in dichloromethane. The ring-opening and ring-closing reactions have been characterized by time-resolved infrared and transient absorption spectroscopies. Ring opening occurs rapidly (τ = 2.1 ns) and efficiently (∼90%) from the singlet excited state to form an intermediate (assigned as a cisoid merocyanine), which returns to the closed ground state (τ = 4.5 ns) in competition with relaxation to the transoid open form (τ = 40 ns). Photochemical ring closing is a faster and simpler process: the excited state proceeds to the closed spirooxazine with a time constant of 0.28 ns. This photochromic switch can be used in conjunction with commercial fluorescent dyes to create a small-molecule switchable fluorescent dyad that shows high contrast and good fatigue resistance in living cells. These properties make the dyads suitable for application in RESOLFT microscopy.

Original publication

DOI

10.1039/c8sc00130h

Type

Journal article

Journal

Chemical Science

Publication Date

20/02/2018

Volume

9

Pages

3029 - 3040