Functionalized aminocarboxylate moieties as linkers for coordination polymers: influence of the substituents in the dimensionality of the final structure

Abstract

The evaluation of aminocarboxylic acid derivatives as linker precursors for amine or hydroxyl tagged extended structures is described. The effect of the presence of an additional functionality in the ring is also explored. In order to analyze the influence of position or nature of this functional group, we studied the related aminocarboxylic acids: 3,4-diaminocarboxylic acid (3,4-dabaH), 3,5-diaminocarboxilic acid (3,5-dabaH), 4-amino-3-hydroxycarboxilic acid (4,3-ahbaH) and 3-amino-4-hydroxycarboxilic acid (3,4-ahbaH). Although these are very simple, commercial ligand precursors, there are very few examples reported with them coordinated. In fact, no compounds have been described with 4,3-ahba or 3,4-ahba as ligands. This work has allowed us to isolate four new compounds of diverse dimensionality, {[Zn(3,4-daba)₂(H₂O)]·3(H₂O)}_n (1), {[Zn(3,5-daba)(py)(OH₂)](NO₃)}_n (2), [Zn(4,3-ahba)₂(Py)₂] (3) and [Zn(bipy)₂(4,3-ahba)₂]₂ (4) (py = pyridine, bipy = 4,4′-bipyridine). Derivatives 1 and 2 present extended structures with uncoordinated amine groups. However in our attempt to obtain hydroxyl tagged species, we observed that the presence of the OH group hampers the possibility of generating extended structures due to the formation of strong intermolecular interaction motifs.