Synthetic approaches and supramolecular properties of 2,2′:n′,m"-terpyridine domains (n=3,4,5,6; m=2,3,4) based on the 2,2′-bipyridine core as ligands with k2N-bidentate coordination mode

Despite almost a century-long history of studying the potential of 2,2':6',2 ''-terpyridine in various fields, the development of synthetic atom-economic "one-pot" approaches/techniques/methods (meeting the requirements of "green chemistry") of the "parent" 2,2':6',2"-tpy domain and its derivatives remains a strategic challenge for synthetic chemists. However, considering modern requirements for ligands in supramolecular chemistry, the development of alternative 2,2':n',m ''-terpyridine domains (n = 3,4,5,6; m = 2,3,4) based on the 2,2'-bipyridine core, sometimes representing "competitive" minor products of the "parent" tpy synthesis, is dictated by time itself as well as the systematization of such information. The transition metal complexes with 2,2':6',2 ''-tpy and the related tpy ligands in the bidentate coordination modes of k(2)N,N' and k(2)N,N '' have attracted much attention as promising photoluminescent materials and photocatalysts. In this review article we analyzed classical and modern methods for the synthesis and functionalization of both the terpyridine prototypes and other 2,2':n',m ''-terpyridines and their supramolecular properties as ligands with the k(2)N-bidentate coordination mode as non-classical hypodentate coordination mode. Also, most significant examples of terpyridine-based metallocomplexes as well as biologically active terpyridines/metallocomplexes have been presented. (C) 2021 Elsevier B.V. All rights reserved.