Study of the Relation existing between Photoresistivity and Substituents Characteristics of some Coumarin Derivatives

Abstract

Coumarins has served as the prototype scaffold for the synthesis of a wide variety of analogues in order to investigate their biological activity as well as their use as additives (levelers or/and brightners) in metal electroplating industrial processes. Several synthetic coumarin derivatives have important pharmacological potential as they proved to be efficient inhibitors of a variety of enzymes. Moreover, coumarin and its derivatives, might also present interesting physical and chemical properties that, in many cases, could be attributed to the development of a p-conjugated system in their molecules. In the present work, a series of coumarin analogues, bearing a substituted phenyl ring on position 3, synthesized via a novel methodology, have been studied as far as concerns their photoconductivity. Specifically, the effect of the nature, the number and the position of substituents, have been investigated. The structure of the molecules was studied by X-ray crystallography. The photoelectrical behavior of the substances was detected using a photoelectrochemical cell (PEC) under a white illumination generated by a halogen lamp and focused in front of the quartz window of the cell. Illumination intensity was approx. 1,000 and 10,000 W/m2. It was found that a relation exists between the photoresistivity of the compounds, their molecular structure andthe orientation of their crystallites in thin films prepared from them.