Alkali metal ion mediated self-assembly of vanadium(V) ions and pyrazole based polydentate ligands leading to the formation of helix, double helix and supramolecular cage-like structures

The anionic cis-dioxovanadium(V) complex species LVO2− and L1VO2− of two tridentate ONO ligands (H2L and H2L1) can bind alkali metal ions in a bis-monodentate fashion like a bridging carboxylate group. Here H2L (N′-[(E)-(2-hydroxyphenyl)methylidene]-3-methyl-1H-pyrazole-5-carbohydrazide) and H2L1 (N′-[(1E)-1-(2-hydroxyphenyl) ethylidene]-3-methyl-1H-pyrazole-5-carbohydrazide) are Schiff base ligands generated by the condensation of 5-methyl 3-pyrazole carbohydrazide with salicylaldehyde and o-hydroxy acetophenone. The six products thus obtained are water soluble polymeric compounds in which the complementary units are held together by the simultaneous use of hydrogen bonding and coulombic interactions. [L1VO2Li(H2O)2]∞ (2), [LVO2Na(H2O)2]∞ (3) and [LVO2K(H2O)2]∞ (5) have been crystallographically characterized. Crystallographic characterization reveals that 2 and 3 are polymeric helicates and 5 is a polymeric cluster with L1VO2− or LVO2− units bridging the labile alkali metal ions which occupy positions on the axis of the polymeric chain.

The anionic cis-dioxovanadium(V) complex species LVO2− and L1VO2− of two tridentate ONO ligands (H2L and H2L1) can bind alkali metal ions in a bis-monodentate fashion like a bridging carboxylate group. The six products thus obtained are water soluble polymeric compounds in which the complementary units are held together by the simultaneous use of hydrogen bonding and coulombic interactions. [L1VO2Li(H2O)2]∞ (2), [LVO2Na(H2O)2]∞ (3) and [LVO2K(H2O)2]∞ (5) have been crystallographically characterized. Crystallographic characterization reveals that 2 and 3 are polymeric helicates and 5 is a polymeric cluster with L1VO2− and LVO2− units bridging the labile alkali metal ions which occupy positions on the axis of the polymeric chain.Figure optionsDownload as PowerPoint slideResearch highlights
► V(V) complexes, heterocycle based Schiff based ligands, heterometallic coordination polymer.
► Ligands derived from pyrazole used for complexation of oxovanadium ion.
► Polymeric complexes of ligated oxovanadium anion woven by labile alkali metal ions.
► Structures of resulting polymeric clusters dependent on the alkali metal ion chosen.