Programming the assembly of carboxylic acid-functionalised hybrid polyoxometalates

Abstract

We report here the straightforward synthesis and characterisation of a series Anderson-type hybrid polyoxometalates in high yield, functionalised with carboxylic acid following the reaction of anhydride precursors with the starting hybrid cluster ([n-N(C 4 H 9) 4 ] 3 [MnMo 6 O 18 ((OCH 2) 3 CNH 2) 2 ]). Seven new structures have been obtained, five of which have acid-terminated ligands. Six of these structures have been isolated with a yield higher than 80% with high purity. This reaction is limited by the bulkiness of the anhydride used; this effect can be employed to selectively synthesise one isomer out of three other possibilities. The acid groups and aromatic platforms attached to the clusters can act as building tools to bridge several length scales and engineer molecular packing within the crystal structure. The presence of acids should also change the hydrophilicity of the clusters, and therefore the way they interact with hydrophilic surfaces. We also show a potential relationship between the acid group interaction in the packing diagram and the cluster's tendency to interact with a hydrophilic surface. In addition to reporting a derived synthetic path to new acid-terminated Mn-Anderson-type hybrids, we describe here a new way to program self-assembly motifs of these compounds in the crystal structure and at interfaces.

Synthesis and biological activity of an Anderson polyoxometalate bis‐functionalized with a Bombesin‐analog peptide

“…The Anderson POM 1 has been initially bis‐functionalized with TRIS to obtain [(C 4 H 9 ) 4 N] 3 [MnMo 6 O 18 ((OCH 2 ) 3 CNH 2 ) 2 ] ( 2 ) . The amino groups on 2 were then reacted with excess succinic anhydride (20 folds), in DMF at 50°C, for 24 h . The product 3 , obtained with 90% yield, displays spaced carboxylic groups, which can be available for the reaction with the terminal amino groups of the peptide upon activation with NHS .…”

“…[(C 4 H 9 ) 4 N] 3 [MnMo 6 O 18 ((OCH 2 ) 3 CNH 2 ) 2 ] ( 2 ) (268.35 mg 0.143 mmol) and succinic anhydride (286.90 mg, 2.87 mmol) were dissolved in 5.2 mL of DMF in a 10 mL flask . The solution was stirred for 24 h at 50°C.…”

Polyoxometalate Clusters Integrated into Peptide Chains and as Inorganic Amino Acids: Solution‐ and Solid‐Phase Approaches

“…The Fmoc strategy was favored for the very mild conditions that can be used for the removal of this protecting group (20 % piperidine in DMF), which we recently demonstrated to be compatible with these clusters 14. Activation of the amino acids by the reaction with a carbodiimide was considered as many POMs are stable to this reagent type,19 and amidations were recently performed on the TRIS‐Mn‐Anderson cluster ([MnMo 6 O 18 ((OCH 2 ) 3 CNH 2 ) 2 ] 3− ) through reactions with anhydrides 7d. As a solid support, we selected a polyethylene glycol (PEG) grafted polystyrene (PS) resin, which is suitable for a broader range of reactions than standard PS resins because of reduced steric hindrance and its amphiphilic character 20.…”

The Anderson–Evans polyoxometalate: From inorganic building blocks via hybrid organic–inorganic structures to tomorrows “Bio-POM”

“…However, it is not only the cation linker that determines the geometrical and physical properties of the compounds but also the geometry of organic ligands that are post-functionalized. When anhydride precursors are used to post-functionalize the hybrid anion [MnMo 6 O 18 ((OCH 2 ) 3 CNH 2 ) 2 ] 3-the reaction can be selective by the bulkiness of the anhydride used leading to the isolation of specific isomers[274]. If aromatic ligands are attached instead as in [MnMo 6 O 18 {(OCH 2 ) 3 CNH-CH 2 -C 16 H 9 } 2 ] 3-that contains pyrene ligands(Figure 11C), nanoscale butterfly shaped channels in the crystal structure can be formed approximately 1 nm wide and 2 nm long.…”