Cobalt(II), copper(II), and zinc(II) framework systems derived from ditopic pyridyl-acetylacetone and pyridyl-pyrazole ligands

Won, Tae-Jin, Clegg, Jack K., Lindoy, Leonard F. and McMurtrie, John C. (2007) Cobalt(II), copper(II), and zinc(II) framework systems derived from ditopic pyridyl-acetylacetone and pyridyl-pyrazole ligands. Crystal Growth and Design, 7 5: 972-979. doi:10.1021/cg0700317

Author Won, Tae-Jin
Clegg, Jack K.
Lindoy, Leonard F.
McMurtrie, John C.
Title Cobalt(II), copper(II), and zinc(II) framework systems derived from ditopic pyridyl-acetylacetone and pyridyl-pyrazole ligands
Journal name Crystal Growth and Design   Check publisher's open access policy
ISSN 1528-7483
Publication date 2007-05
Sub-type Article (original research)
DOI 10.1021/cg0700317
Volume 7
Issue 5
Start page 972
End page 979
Total pages 8
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Formatted abstract
The synthesis of two new bifuctional ligand sytems incorporating two different "classical" coordination units connected by a bent (but flexible) thioether linkage is reported. The new systems are the 3-diketone-pyridyl derivative, β-(pyridin-4-ylthio)-pentane-2,4-dione (L 1), and its hydrazine condensation product, the pyridyl-pyrazole species 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)-pyridine (L 2). Both systems were designed for use in metal-organic framework studies. With L 1, four metal-containing products were crystallized, [Cu(L 1-H) 2] n (1), {[Cu(L 1-H) 2]·0.5H 2O·CHCl 3} n (2), {[Zn(L 1-H) 2]·2H 2O} n (3), and [Zn(L 1-H) 2]·2MeOH} n (4); these display three different array types. Compound 1 incorporates 5-coordinate Cu(II) ions with square pyramidal stereochemistry. The β-diketonato groups from two ligands coordinate in the basal plane with the apical position occupied by a pyridyl nitrogen from a third ligand that bridges to an adjacent copper center. Propagation of this coordination motif produces a ID chain. In 2, which is a pseudo-polymorphic phase of 1, each Cu(II) ion is 6-coordinate with each metal center being bound by two bidentate β-diketonato groups and two pyridyl donors from four different ligands in a cis configuration. The ligand arrangement bridges each metal to four others producing an infinite 2D rhombic grid [(4,4) net]. The grids stack to form channels containing disordered water and chloroform molecules; the solvent-accessible space is 33% of the crystal volume. Crystals of 3 are isostructural with 2, except that they incorporate water as the only solvate in the channels. The solvent-accessible voids constitute 22% of the crystal volume, reflecting closer packing of adjacent grids. A TGA study showed that the water molecules are removed by 375 K and that the resulting desolvated complex is stable up to 573 K. Compound 4 is a pseudo-polymorph of 3 in which the 6-coordinate Zn(II) coordination is similar to that in 3 but with polymeric connectivity producing a chiral [8,4] type 3D network (space group P4 12 12). Helical channels corresponding to 25% of the crystal volume run parallel to the 4-fold axes and are occupied by methanol guests. With 4-(3,5-dimethyl-1H-pyrazol-4-ylthio) pyridine (L 2), an extended array consisting of zwitterionic [Co(L 2+H)Cl 3] n (5) units linked by hydrogen bonds and the metal-linked molecular framework species{[Zn(L 2)Cl 2]·0.5H 2O} n (6) were obtained. The cobalt center in 5 is tetrahedrally coordinated by three chloride ions and a pyrazole nitrogen from (L 2+H); the protonation is present at the pyridyl nitrogen atom. This protonated pyridyl nitrogen forms a charge-assisted hydrogen bond of type N-H +⋯Cl with a coordinated chloride from an adjacent complex to yield a hydrogen-bonded chainlike array. Intermolecular N-H⋯C1 hydrogen bonds also exist between the non-deprotonated pyrazole nitrogen and adjacent chloro ligands. Each tetrahedral Zn(II) center in 6 is coordinated to two chloride ions, a pyridyl nitrogen from one L 2 ligand and a pyrazole nitrogen from another. Each L 2 thus bridges adjacent Zn(II) centers, forming 1D polymeric chains that aggregate in the crystal to produce narrow channels occupied by water molecules.
Keyword Metal organic frameworks
Secondary building units
Coordination polymers
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Publication Date (Web): April 4, 2007.

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
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