Photo-sensitive complexes based on azobenzene, Physical Sciences Reviews

Identifier:  imarina:5132474

Handle: https://hdl.handle.net/20.500.11797/imarina5132474

Authors:  Tylkowski, B; Jastrzab, R; Skrobanska, M

Abstract:
In the last few decades, the development of photo-responsive materials has become an intensive area of research. These substances are intended for the production of "smart chemical systems", whose properties - and eventually functionality - are controlled by changes in the environment (light irradiation) [1]. These systems have already been implemented in a wide range of modern materials and devices for daily applications such as sunglass lenses, memory devices, photochromic inks, etc. [2]. Light offers unparalleled opportunities as a non-invasive regulatory element for biological applications. First, it shows a great degree of orthogonality toward most elements of chemical and biochemical systems. In contrast to chemicals, which are used for regulating biological processes, photons do not cause contamination of the studied object and have low or negligible toxicity. Second, light can be delivered with very high spatial and temporal precision, which is of paramount importance for controlling the action of bioactive compounds. Finally, light can be regulated in a qualitative and quantitative manner by adjusting wavelength and intensity [3]. Despite the importance and versatility of transition metal complexes, smart photo-responsive examples remain rather unexplored in comparison with the large number of well-known light-triggered organic switches. In principle, photo-responsive metal complexes can be obtained by incorporation of organic photochromic units in the structure of their ligands. These photo-sensitive ligands, rather than acting as conventional spectators that tune the properties of their complexes, transform them into dynamic smart entities able to offer a functional response to an external stimulus. This chapter is divided into two parts. In the first part we discuss the photoisomerisation processes of azobenzene molecules as organic photochromic units, while in the second part we describe selected examples of complexes containing these UV-sensitive moieties in their structures.