Robust recognition of malonate and 2-amino-4-picolinium in conjunction with M(ii) as a triad (M = Ni/Co/Mn): role of this highly stable hydrogen-bonded motif in driving supramolecular self-assembly

Abstract

The crystal lattice of the three isostructural compounds 1–3, (C₆H₈N₂H)₂[M(C₃H₂O₄)₂(H₂O)₂]·4H₂O (C₆H₈N₂H = protonated 2-amino-4-picoline, M = Ni/Co/Mn, C₃H₄O₄ = malonate dianion; hereafter, malonate) is formed by supramolecular 2D layers. Hydrogen-bonding, π⋯π and lone pair⋯π interactions play crucial role in organizing monomeric [M^II(mal)₂(H₂O)₂] units into 2D sheets along the ab plane, through the self-association between two different supramolecular building blocks, namely a tetrameric water cluster including metal-coordinated water molecules, and R₂²(8) and R₂²(7) hydrogen-bonded recognition synthons between 2-amino-4-picolinium and malonate. DFT calculations clearly show that the robust 2-amino-4-picolinium/malonate hydrogen-bonded motif drives the self-assembly of the supramolecular network observed.