Physico-Chemical nanomaterials science

Excited state dynamics of photochromic dimethyldihydropyrene derivatives in solutions
Ignas Čiplys1, Irena Kulszewicz-Bajer2, Renata Karpicz1
1 Center for Physical Sciences and Technology, Saulėtekio al. 3, LT-10257 Vilnius, Lithuania. 
E-mail: ignas.ciplys@gmail.com 
2 Warsaw University of Technology, Poland.

Molecular switches can be commonly applied to control different functions and properties of materials which can be used in organic electronics (as for example in new memory elements based on single molecule) or in biology to manipulate the biological systems. Photochromism of dimethyldihydropyrene derivatives is a reversible transformation under UV and visible light irradiation between two, open-ring hexatriene and closed-ring cyclohexadiene, isomers with different spectroscopic properties. Usually, the optical-active derivatives of diarylethene were fluorescent in the open-ring state and non-fluorescent in the closed-ring form.
New dimethyldihydropyrene derivatives were synthesized, and their optical properties as well as excited state dynamics were investigated in the solutions. We focus on the emissive properties of dimethyldihydropyrene derivatives with the possibility to switch them between fluorescent and non-fluorescent states. During the first 100-300 ps after excitation under visible light the closed-ring cyclohexadiene isomer were opened. Reverse transformation took place through intermediate stage during several picoseconds.