title: Self-assembly of metal-organic coordination polymers constructed from a bent dicarboxylate ligand: diversity of coordination modes, structures, and gas adsorption.
abstract: We have synthesized five new metal-organic coordination polymers incorporating the bent ligand H(2)hfipbb [4,4'-(hexafluoroisopropylidene)bis(benzoic acid)] with different transition metal ions and co-ligands via solvothermal reactions to give [Zn(2)(hfipbb)(2)(py)(2)] x DMF (1), [Zn(2)(hfipbb)(2)(4,4'-bipy)(H(2)O)] (2), [Zn(2)(hfipbb)(2)(bpdab)].2DMF (3), [Cd(2)(hfipbb)(2)(DMF)(2)] x 2 DMF (4), and [Co(hfipbb)(dpp)] x MeOH (5) (py = pyridine, 4,4'-bipy = 4,4'-bipyridine, bpdab = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, dpp = 1,3-di(4-pyridyl)propane). Compound 1 displays a 2-fold 2D-->2D parallel interpenetrated layer network with one-dimensional (1D) helical channels, while 3 exhibits a three-dimensional pillared helical-layer open framework of alpha-Po topology based upon binuclear paddlewheel units. In compounds 2 and 5, binuclear motifs with double carboxylate bridges are linked by hfipbb(2-) ligands into a 1D ribbon, which are further assembled into two-dimensional non-interpenetrated (4,4) layers via bipyridyl co-ligands. However, the different bridging modes of hfipbb(2-) ligands and the different disposition of the coordinated co-ligands around metal ions result in subtle differences in the final architecture. Thus, 2 is based on a binuclear cluster node, double-stranded hfipbb(2-) linkers, and single-stranded 4,4'-bipy linkers, while 5 is based on a binuclear cluster node and hfipbb(2-) and dpp linkers which are both double-stranded. Among these compounds, the Cd(II) complex 4 is possibly the most interesting because it represents a rare example in which metal centers are linked by carboxylate groups into infinite chains further joined together by hfipbb(2-) spacers to form a 2D network with tubular helical channels. All these coordination polymers exhibit low solvent-accessible volumes. Both 3 and 4 retain structural integrity and permanent microporosity upon evacuation of guest molecules, with hydrogen uptakes of 0.57 and 0.78 wt %, respectively, at 20 bar and 77 K.
authors: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
authors: Wenbin
authors: W
authors: Yang
authors: Xiang
authors: X
authors: Lin
authors: Alexander J
authors: AJ
authors: Blake
authors: Claire
authors: C
authors: Wilson
authors: Peter
authors: P
authors: Hubberstey
authors: Neil R
authors: NR
authors: Champness
authors: Martin
authors: M
authors: Schröder
mesh_terms: D000327:Adsorption; D018360:Crystallography, X-Ray; D003998:Dicarboxylic Acids / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D003998:Dicarboxylic Acids; D005740:Gases; D008024:Ligands; D009942:Organometallic Compounds; D011108:Polymers; D028561:Transition Elements