Carbolong complexes: an emerging class of metallaaromatics for next-generation functional materials

Aromaticity and antiaromaticity represent fundamental pillars of chemical stability, reactivity, and performance. As distinctive aromatic complexes with metallaaromaticity, carbolong complexes featuring metal-carbon conjugated polycyclic metallacycles have emerged as an intriguing class of compounds in organometallic chemistry, biomedical science, and materials science. Characterized by a long carbon chain chelated to a metal center via multiple metal-carbon bonds, these complexes exhibit rare Craig aromaticity in addition to Hückel topologies. This unique electronic structure confers exceptional stability, extensive electron delocalization, and highly tunable optoelectronic properties. This review provides a comprehensive analysis of the synthetic strategies and design principles governing carbolong chemistry. We have highlighted recent advances in the single-molecule charge transport of carbolong molecules, the integration of carbolong complexes into high-efficiency solar cells, and their burgeoning potential in photothermal therapy and molecular optoelectronics. By bridging the gap between fundamental metallaaromaticity and functional materials science, this work serves as a strategic roadmap for researchers leveraging carbolong chemistry and related design principles to drive the development of next-generation optoelectronic, energy conversion, and biomedical technologies.