Polyacenes

Polyacenes are a class of organic molecules consisting of fused benzene rings arranged linearly. They can be viewed as an extended version of anthracene, which is a tricyclic polyacene. The general formula for a polyacene with n fused rings is C(4n+2)H(2n+4). The simplest polyacene is benzene (n=1), followed by naphthalene (n=2), anthracene (n=3), and tetracene (n=4). As the number of fused rings increases, the polyacene becomes larger and more conjugated.

These molecules are characterized by their extended pi-electron systems, which lead to interesting optical and electronic properties. Polyacenes are often colored, with the color becoming deeper as the number of rings increases, shifting towards longer wavelengths. They are also semiconductors, and their conductivity generally increases with chain length. Due to their planar structure and delocalized electrons, polyacenes are of interest in organic electronics, particularly in applications such as organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs).

The synthesis of larger polyacenes can be challenging, and they are often prone to oxidation, especially those with more than four or five rings. Research continues to explore new synthetic routes and methods to stabilize these fascinating molecules for technological applications. The linear arrangement of fused rings distinguishes them from other polycyclic aromatic hydrocarbons like coronene or ovalene, which have more complex, non-linear structures.