Full- or Half-Encapsulation of Sulfate Anion by a Tris(3-pyridylurea) Receptor: Effect of the Secondary Coordination Sphere
datasetposted on 02.11.2009 by Fuyu Zhuge, Biao Wu, Jianjun Liang, Jin Yang, Yanyan Liu, Chuandong Jia, Christoph Janiak, Ning Tang, Xiao-Juan Yang
Datasets usually provide raw data for analysis. This raw data often comes in spreadsheet form, but can be any collection of data, on which analysis can be performed.
Self-assembly of the [Fe(DABP)3]SO4 (DABP = 5,5′-diamino-2,2′-bipyridine) or [Fe(bipy)3]SO4 (bipy = 2,2′-bipyridine) complex with a tripodal tris(3-pyridylurea) ligand (L) results in a layered structure that includes a sulfate anion in the cleft of one L molecule. The two compounds, [Fe(DABP)3][SO4⊂L]·10H2O (2) and [Fe(bipy)3][SO4⊂L]·9H2O (3), show very similar sheets formed by the anionic units [SO4⊂L]2− and cationic building blocks ([Fe(DABP)3]2+ or [Fe(bipy)3]2+). However, there are different water clusters that link the adjacent layers in the two products, that is, water parallelograms and quasi “water cubes” in 2 versus single water molecules, water dimers, and hexamers in 3. The half-encapsulation of sulfate by a single L molecule contrasts with the previously reported full-encapsulation of the sulfate ion by two L molecules in [M(H2O)6][SO4⊂L2] (1). This different anion encapsulation is traced to the hydrogen-acceptor properties of the pyridyl groups of L together with the hydrogen-bonding properties of the cation secondary coordination sphere for a solid-state packing optimization. In 1 the direct hydrogen bonding from the secondary coordination sphere of octahedral [M(H2O)6]2+ to L-pyridyl helps in the formation of an octahedral cation−anion coordination in the NaCl-type structure. In 2 and 3, crystal water instead of the cations has to satisfy the hydrogen-accepting demands of L. Consequently, a non-spherical and only partly water-surrounded half-encapsulated [SO4⊂L]2− anion allows for a closer approach of the [Fe(DABP)3]2+ or [Fe(bipy)3]2+ cations than the [SO4⊂L2]2− anion. Then, the similar cation and anion size in 2 and 3 with the Coulomb attraction confined to a two-dimensional plane leads to the formation of a hexagonal BN (or graphite) lattice. Competition experiments with different anions for compound 2 reveal that SO42− can be selectively crystallized against NO3−, OAc−, or ClO4−.