Incorporation of photochromic spiropyran compounds and spiropyran modified substrates into flow micro-systems

Spiropyran is a well known family of photochromic compounds presenting the peculiar feature of being able to change their physical and chemical properties under external light modulation [1]. It has been demonstrated that even low-power light sources such as light emitting diodes (LEDs) can switch spiropyran molecules between an non-polar, uncoloured spiro form (SP) and a strongly coloured, zwitterionic merocyanine form (MC), which also possesses a phenolate binding site for metal guest species such as Cu2+ [2] and Co2+ [3], using white or UV light, respectively. MC-bound metal ions can be subsequently released using a green LED light source which converts the binding-MC back to the passive SP form [4]. The incorporation of spiropyran derivatives or spiro-modified substrates into flow micro-systems opens up intriguing possibilities for creating stationary phases whose binding behaviour can be externally modulated using light. We investigated this idea using two approaches. In one case, the stationary phases were generated by packing spiropyran functionalised silica and polystyrene microspheres [5] into polytetrafluoroethylene (PTFE)-coated fused silica capillaries (100 μm inner diameter). In the second, spiropyran compounds were used to create new monolithic stationary phases, using both a spiropyran monomer to synthesise a SP-derivatised monolith directly in silica capillaries, and a post-synthesis functionalisation strategy wherein the spiropyran is immobilised on the monolith’s inner surface after it has been formed in-situ. These SP-modified stationary phases have indeed shown light-induced reversible ion-binding capability (functionalised microspheres) and light-modulated electroosmotic nanoflow (spiropyran monoliths). In this talk the creation of these stationary phases and their light-modulated behaviour will be discussed. References [1] Durr, H.; Bouas-Laurent, H. Eds, Photochromism: Molecules and Systems, Elsevier, Amsterdam, 2003 [2] Shao, N.; Zhang, Y.; Cheung, S.; Yang, R.; Chan, W.; Mo, T.; Li, K.; Liu, F. Anal. Chem., 2005, 77, 7294-7303. [3]. Byrne, R.; Stitzel, S.; Diamond, D. Mat. Chem., 2006, 16, 1332-1337 [4]. Radu, A.; Scarmagnani, S.; Byrne, R.; Slater, C.; Lau, K. T.; Diamond, D., J. Physics D: Applied Physics 2007, 23, 7238-7244 [5] Scarmagnani S.; Walsh Z.; Slater C.; Alhashimy N.; Paull B.; Macka M.; Diamond D., J. Mat. Chem., 2008, 18, 5063 – 5071.