Recognition Properties and Self‐assembly of Planar [M(2‐pyridyl‐1,2,3‐triazole)₂]²⁺ Metallo‐ligands

Abstract

Molecular recognition continues to be an area of keen interest for supramolecular chemists. The investigated [M(L) ] metallo-ligands (M=Pd , Pt , L=2-(1-(pyridine-4-methyl)-1 H-1,2,3-triazol-4-yl)pyridine) form a planar cationic panel with vacant pyridyl binding sites. They interact with planar neutral aromatic guests through π-π and/or metallophilic interactions. In some cases, the metallo-ligands also interacted in the solid state with Ag either through coordination to the pendant pyridyl arms, or through metal-metal interactions, forming coordination polymers. We have therefore developed a system that reliably recognises a planar electron-rich guest in solution and in the solid state, and shows the potential to link the resultant host-guest adducts into extended solid-state structures. The facile synthesis and ready functionalisation of 2-pyridyl-1,2,3-triazole ligands through copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry should allow for ready tuning of the electronic properties of adducts formed from these systems.

Self‐assembly and Cycling of a Three‐state PdxLy Metallosupramolecular System

“…In addition to the purported [Pd 9 L 12 ] 18+ species, the ESI‐MS of this mixture indicated the existence of mono‐ and di‐palladium(II) species, [Pd L 2 ] 2+ ( Pd 1 ) and [Pd 2 L 2 ] 4+ ( Pd 2 ) . We have previously reported the formation of Pd 1 , from a 2:1 combination of L and Pd II . The complex forms with 2 ligands both coordinated to the Pd II metal cation through the bidentate 2‐pyridyl‐1,2,3‐triazole binding sites leaving the pyridyl “arms” uncomplexed (Figure ).…”

“…While these remain unidentified, they are presumably larger macrocycles/ oligomers. There was no concentration dependencei n [D 6 ]DMSO,p robablyb ecause the higher dielectric constant of this solvent better masks the cationic charges of the two [17] Pd 2 and Pd 9 . [16] Colours: carbon grey,nitrogen light blue, palladium blue.…”

“…Pd II source is [Pd(CH 3 CN) 4 ](BF 4 ) 2 , solvent [D 3 ]acetonitrile. Below: key, showing X‐ray crystal structures of Pd 1 , Pd 2 and Pd 9 . Colours: carbon grey, nitrogen light blue, palladium blue.…”

“…We have previously reported the formation of Pd 1 ,f rom a2:1 combination of L and Pd II . [17] The complex forms with 2l igands both coordinated to the Pd II metal cation throught he bidentate 2-pyridyl-1,2,3-triazole binding sites leaving the pyridyl "arms" uncomplexed ( Figure 1). This Pd 1 species forms from this ratio of componentsr egardless of the concentration (within the solubility limits of the system, [L] 25 mm).…”

Planar 2‐Pyridyl‐1,2,3‐triazole Derived Metallo‐ligands: Self‐assembly with PdCl2 and Photocatalysis

“…[12] The platinum(II) metallo-ligands and the [Pd 3 Pt 6 L 12 ] 18 + ring were shown to act as photosensitisers for generation of singlet oxygen. [13] This observation combined with the interaction of electron rich planar guests (such as anthracene) [14] with the electron deficient metallo-ligands in the architecture resulted in a synergistic scenario where the increased local concentration of guest and singlet oxygen ( 1 O 2 ) in the vicinity of the cage was suggested to have led to the increased rate of photocatalytic anthracenyl endoperoxide production. Unfortunately, the cage was found to eventually decompose under the condition of the catalysis, which was partially attributed to the instability of the methylene linker in the metallo-ligands.…”