Thiahelicenes: from basic knowledge to applications

Thiahelicenes are helical-shaped polyaromatic conjugated molecules which, in the majority of cases, alternate benzene and thiophene rings. Examples in which only thiophene rings are present are also known. Both types of thiahelicenes are intrinsically chiral molecules and the configurationally stable M and P enantiomers can be separated using different techniques. Thiahelicenes ending with thiophene rings can be easily and regioselectively functionalized by direct electrophilic substitution or through generation of α-anions on the terminal thiophene rings, followed by reaction with electrophiles.Substitution on inner benzene rings can best be achieved by starting from properly functionalized precursors. Hence, steric and electronic properties of thiahelicenes can be modulated by introducing substituents of different nature and size on the helical scaffold. The theoretical investigation of these systems allows prediction of thiahelicenes' physical and optical properties.Applications of thiahelicenes span many different field such as material science, optoelectronics, catalysis, polymers, biology, and others.Despite the already acquired knowledge on thiahelicenes, several aspects must still be addressed, such as the establishment of efficient synthetic methodologies for obtaining pure enantiomers for the abovementioned applications.The authors believe that the investigation of thiahelicenes potential in biology deserves greater attention, because this topic is still in its infancy stage. Preliminary studies show interaction of thiahelicenes with DNA and can be the starting point for wider investigations of unusual biological applications.We hope this chapter will stimulate the interest of researchers not only in the field of chemistry but also in biology and physics.