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Porous Polyrotaxane Coordination Networks Containing Two Distinct Conformers of a Discontinuously Flexible Ligand

Hawes, Chris S.; Knowles, Gregory P.; Chaffee, Alan L.; White, Keith F.; Abrahams, Brendan F.; Batten, Stuart R.; Turner, David R.

Authors

Gregory P. Knowles

Alan L. Chaffee

Keith F. White

Brendan F. Abrahams

Stuart R. Batten

David R. Turner



Abstract

A new divergent homopiperazine-derived ligand N,N'-bis(4-carboxyphenyl)-1,4-diazacycloheptane H2L has been prepared, containing a semirigid saturated heterocyclic core which is capable of providing multiple distinct bridging geometries. Reaction of H2L with zinc acetate in DMSO gives a two-dimensional parallel interpenetrated polyrotaxane structure 1 in which the loops and rods are formed by the bent cis-(eq,ax) twist boat and trans-(ax,ax) twist chair conformers, respectively. By matching the distances between the solvated metal sites in the structure of 1, a related material 2 can be prepared incorporating the pillaring ligand trans-1,2-bis(4-pyridyl)ethylene bpe. Compound 2 displays a similar polyrotaxane interpenetration mode, permitted by the presence of both cis and trans ligand conformers, but displays a three-dimensional 2.69 topology related to the dia diamondoid network. The guest exchange and gas adsorption properties of both materials were investigated; while compound 1 displays poor stability to guest exchange and negligible gas uptake, the higher connectivity microporous compound 2 shows facile guest exchange and a surprisingly high CO2 capacity of 12 wt % at 1 bar and 273 K, and a zero-loading enthalpy of adsorption of -32 kJ mol-1 . High-pressure adsorption isotherms also show moderate physisorption of H2 and CH4 within the material.

Citation

Hawes, C. S., Knowles, G. P., Chaffee, A. L., White, K. F., Abrahams, B. F., Batten, S. R., & Turner, D. R. (2016). Porous Polyrotaxane Coordination Networks Containing Two Distinct Conformers of a Discontinuously Flexible Ligand. Inorganic Chemistry, 10467 -10474. https://doi.org/10.1021/acs.inorgchem.6b01713

Acceptance Date Sep 26, 2016
Publication Date Sep 26, 2016
Journal Inorganic Chemistry
Print ISSN 0020-1669
Publisher American Chemical Society
Pages 10467 -10474
DOI https://doi.org/10.1021/acs.inorgchem.6b01713
Publisher URL http://doi.org/10.1021/acs.inorgchem.6b01713