The terpyridine isomer game: from chelate to coordination network building block

Abstract

The first 4,2′:6′,4′′-terpyridine (4,2′:6′,4′′-tpy) containing coordination polymer was reported over 20 years ago and in the last decade, there has been increased interest in the use of ditopic 4,2′:6′,4′′-tpy ligands as linkers in coordination polymers and 2D-networks. Functionalization in the 4′-position of 4,2′:6′,4′′-tpy is synthetically straightforward, giving access to a large suite of building blocks. Less well explored is the coordination chemistry of 3,2′:6′,3′′-tpy ligands which exhibit greater conformational flexibility than 4,2′:6′,4′′-tpy. One approach to making the transition from 2D- to 3D-networks is to utilize tetratopic bis(4,2′:6′,4′′-tpy) and bis(3,2′:6′,3′′-tpy) ligands which act as 4-connecting nodes. In this highlight, we survey recent progress towards a better understanding of the design principles associated with the use of ditopic and tetratopic 4,2′:6′,4′′-tpy and 3,2′:6′,3′′-tpy containing ligands and their roles both as linkers and nodes in coordination assemblies.