Tetratopic bis(4,2′:6′,4′′-terpyridine) and bis(3,2′:6′,3′′-terpyridine) Ligands as 4-Connecting Nodes in 2D-Coordination Networks and 3D-Frameworks

Abstract

Ditopic, 4,2':6',4''-terpyridine (4,2':6',4''-tpy) and 3,2':6',3''-terpyridine (3,2':6',3''-tpy) present a divergent N,N'-donor set (the central N atom typically being non-coordinated) and are ideal building blocks for the assembly of coordination polymers and networks. The step from ditopic to tetratopic ligands which contain two interconnected 4,2':6',4''-tpy or 3,2':6',3''-tpy metal-binding domains renders the ligand capable of acting as a 4-connecting node and is a successful route to increasing the dimensionality of the assembly. In this short overview, we illustrate the recent development of the use of bis(4,2':6',4''-tpy) and bis(3,2':6',3''-tpy) ligands and compare strategies using either ditopic or tetratopic ligands.

Trinodal Self-Penetrating Nets from Reactions of 1,4-Bis(alkoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene Ligands with Cobalt(II) Thiocyanate

“…The coordination chemistry of 2,2':6',2"-terpyridine (2,2':6',2"-tpy, preferred IUPAC name 1 2 ,2 2 :2 6 ,3 2 -terpyridine) is well established and is dominated by chelation to a single metal centre [1,2], with mono or bidentate modes being less common [3]. As Scheme 1 shows, tridentate bonding by 2,2':6',2"-tpy is synonymous with binding one metal ion and the ligand is classed as monotopic (having a single metal-binding domain) [4]. The incorporation of two or more 2,2':6',2"-tpy units into a single organic molecule leads to a multitopic ligand [2,[5][6][7] and is a design strategy that has been used to access high nuclearity coordination assemblies [8][9][10].…”

“…The incorporation of two or more 2,2':6',2"-tpy units into a single organic molecule leads to a multitopic ligand [2,[5][6][7] and is a design strategy that has been used to access high nuclearity coordination assemblies [8][9][10]. An alternative approach is to use isomers of terpyridine, such as 3,2':6',3"-tpy (PIN 1 3 ,2 2 :2 6 ,3 3 -terpyridine) and 4,2':6',4"-tpy (PIN 1 4 ,2 2 :2 6 ,3 4 -terpyridine), in which chelation is not possible (Scheme 1). Both 3,2':6',3"-tpy and 4,2':6',4"-tpy coordinate to metal ions through only the outer nitrogen atoms and are therefore ditopic ligands [4] with two discrete pyridine metal-binding domains.…”

“…An alternative approach is to use isomers of terpyridine, such as 3,2':6',3"-tpy (PIN 1 3 ,2 2 :2 6 ,3 3 -terpyridine) and 4,2':6',4"-tpy (PIN 1 4 ,2 2 :2 6 ,3 4 -terpyridine), in which chelation is not possible (Scheme 1). Both 3,2':6',3"-tpy and 4,2':6',4"-tpy coordinate to metal ions through only the outer nitrogen atoms and are therefore ditopic ligands [4] with two discrete pyridine metal-binding domains. Connection of two 3,2':6',3"-tpy or 4,2':6',4"-tpy domains through a spacer leads to tetratopic ligands with four discrete pyridine metal-binding domains (Scheme 2), which are suitable as building blocks for 2D-and 3D-coordination networks [4,[11][12][13][14][15][16][17][18].…”

“…Both 3,2':6',3"-tpy and 4,2':6',4"-tpy coordinate to metal ions through only the outer nitrogen atoms and are therefore ditopic ligands [4] with two discrete pyridine metal-binding domains. Connection of two 3,2':6',3"-tpy or 4,2':6',4"-tpy domains through a spacer leads to tetratopic ligands with four discrete pyridine metal-binding domains (Scheme 2), which are suitable as building blocks for 2D-and 3D-coordination networks [4,[11][12][13][14][15][16][17][18]. Despite the fact that Cave and Raston reported the synthesis of bis(4,2':6',4''-terpyridin-4'-yl)benzene in 2001 [19], the coordination chemistry of bis(4,2':6',4''-tpy) ligands has only developed significantly in the last few years.…”

Substituent Effects in the Crystal Packing of Derivatives of 4′-Phenyl-2,2′:6′,2″-Terpyridine

“…Over the last four decades, we have been particularly interested in the use of terpyridine ligands, principally 2,2':6',2"-terpyridine (tpy) and its derivatives [16,17] and 3,2':6',3"-and 4,2':6',4"-terpyridines [18,19]. Crystal packing in tpys and tpy-containing metal coordination compounds is frequently dictated by face-to-face (π…π) and edge-to-face interactions (CH…π) between aromatic rings.…”