Full- or half-encapsulation of sulfate anion by a tris(3-pyridylurea) receptor: effect of the secondary coordination sphere

Fuyu Zhuge, Biao Wu*, Jianjun Liang, Jin Yang, Yanyan Liu, Chuandong Jia, Christoph Janiak, Ning Tang, Xiao Juan Yang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

107 Citations (Scopus)

Abstract

Self-assembly of the [Fe(DABP)3]SO4 (DABP = 5,5′-diamino-2,2′-bipyridine) or [Fe(bipy)3]SO 4 (bipy = 2,2′-bipyridine) complex with a tripodal tris(3-pyridyiurea) 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][SO4CL] · 10H2O (2) and [Fe(bipy) 3][SO4CL] · 9H2O (3), show very similar sheets formed by the anionic units [SO4CL]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][SO4CL2] (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 NaCI-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 [SO4CL]2- anion allows for a closer approach of the [Fe(DABP)3]2+ or [Fe(bipy)3]2+ cations than the [SO4CL 2]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-.

Original languageEnglish
Pages (from-to)10249-10256
Number of pages8
JournalInorganic Chemistry
Volume48
Issue number21
DOIs
Publication statusPublished - 2 Nov 2009
Externally publishedYes

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