Alternative two-dimensional embrace nets formed by metal complexes of 4′-phenylterpyridine crystallised with hydrophilic anions

Abstract

Previously we reported that complexes [M(Phterpy)₂]²⁺ (Phterpy = 4′-phenyl-2,2′:6′,2″-terpyridine) when crystallised with PF₆⁻ generally form the standard two-dimensional terpy embrace (2D-TE) grid, except in one crystal where the 4′-phenyl substituents intercalate the 2D-TE, partially decomposing it to one-dimensional terpy embraces (1D-TE). Here we report that when crystallised instead with the hydrophilic anions Cl⁻, SO₄²⁻, tosylate, and [Ni(dipic)₂]²⁻ (dipic = pyridine-2,6-dicarboxylate) these complexes form a different class of layered structure. One layer contains the [M(Phterpy)₂]²⁺ complexes, while in the other layer the anions are associated with aggregates of large numbers of water molecules and in some cases solvent alcohol molecules. Further, the [M(Phterpy)₂]²⁺ complexes generally form longitudinal embraces, propagated in a direction parallel to the pseudo-S₄ axes of the complexes, in contrast to the lateral embraces of the 2D-TE and 1D-TE motifs. The total numbers of offset-face-to-face and edge-to-face local interactions are similar for longitudinal and lateral embrace motifs. The crystals described are [Ru(Phterpy)₂]Cl₂(H₂O)₁₀1, [Ru(Phterpy)₂]Cl₂(MeOH)₄(H₂O) 2, [Fe(Phterpy)₂]SO₄(ⁱBuOH)_0.5(H₂O)_7.53, [Ru(Phterpy)₂][Ni(dipic)₂](H₂O)₁₅4, and [Ru(Phterpy)₂](tosylate)₂(H₂O)₄5. Features of the hydrophilic domains in these crystals are sheets of {(Cl⁻)(H₂O)₅}_∞ in 1, a chain of {(SO₄²⁻)(H₂O)₇}_∞ in 3, and chains of beads (H₂O)₃₀ in 4. We conclude that the crystal engineering of extended embrace motifs for hydrophobic [M(Phterpy)₂]²⁺ complexes is anion-dominated, through the degree of anion conscription of hydrogen-bonding solvent during crystallisation.