5,6-Dihydroxyindole Chemistry: Unexplored Opportunities Beyond Eumelanin

5,6-Dihydroxyindoles, the key building blocks of eumelanin biopolymers, hold promise as versatile molecular systems for the design and development of new functional aromatic scaffolds, biomimetic polymers, and nanomaterials with tailored optical and electronic properties. During the past decade, research into the photophysics, synthesis, pi electron manipulation, and reaction behavior of 5,6-dihydroxyindoles has expanded beyond the traditional boundaries of biology and medicine to involve physicists, organic chemists, and materials scientists. This review presents the latest advances in 5,6-dihydroxyindole chemistry from a new perspective. Touching only upon themes at the periphery of eumelanin research, it seeks rather to throw light on the chemical and photophysical features of this peculiar pi electron system as an unexplored conceptual and practical platform on which synthetic creativity and rational design might generate a range of chemically diverse molecular scaffolds.