Engineering the metal-terpy grid with complexes containing 4′-hydroxy terpyridine

Abstract

We report and analyse the crystallisation and crystal structures of [Ni(terpyOH)₂](BF₄)₂ (1), [Fe(terpyOH)₂](BF₄)₂·H₂O (2a) isomorphous with [Ru(terpyOH)₂](BF₄)₂·H₂O (2b), [Cu(terpyOH)₂](BF₄)₂·H₂O (3a) isomorphous with [Ru(terpyOH)(terpy)](BF₄)₂·H₂O (3b) and with [Co(terpyOH)₂](ClO₄)₂·H₂O already published (terpyOH = 4′-hydroxy-2,2′:6′,2″-terpyridine, or 2,6-bis(2-pyridyl)-4(1H)-pyridone). All of these crystals contain the standard two-dimensional terpy embrace (2D-TE) grid of metal complexes, with secondary variations in stacking patterns and inter- and intra-layer hydrogen bonding connectivities. There is no hydrogen bonding between the 4′-OH groups of opposing layers (which would require large and potentially unstable separation of layers). Instead the 4′-OH groups are located in the deep grooves of the surface of the opposing layer, where the anions and water (when present) are located. Crystal structure types 2 and 3 contain alternating hydrated and anhydrous interlayer domains. All evidence points to stability and reproducibility for this general class of 2D-TE grid network.