Metalloradical and photoredox manifolds in manganese photocatalysis.

Visible-light-driven manganese catalysis has emerged as a powerful and sustainable alternative to noble-metal-based photoredox systems. Owing to its abundance on Earth, low toxicity, and rich redox flexibility, manganese enables a wide range of bond-forming reactions under mild conditions. This review summarizes recent advances (2020-2025) in manganese photocatalysis through a unified mechanistic lens, highlighting two fundamentally distinct yet interconnected activation manifolds: metalloradical pathways initiated via Mn-Mn bond homolysis and photoredox processes proceeding through single-electron transfer. Emphasis is placed on mechanistic principles governing atom-transfer and redox-mediated transformations, reaction scope, and synthetic applications, including C-C and C-X bond formation, carbonylation, and late-stage functionalization. By comparing these mechanistic regimes, this review provides a conceptual framework that distinguishes manganese photocatalysis from conventional noble-metal systems and underscores its growing role in sustainable light-mediated organic synthesis.