Porous Polyrotaxane Coordination Networks Containing Two Distinct Conformers of a Discontinuously Flexible Ligand.
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 2.69topology 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 CO2capacity 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 H2and CH4within the material.
School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
Chris S
CS
Hawes
School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
Gregory P
GP
Knowles
School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
Alan L
AL
Chaffee
School of Chemistry, The University of Melbourne , Melbourne, Victoria 3010, Australia.
Keith F
KF
White
School of Chemistry, The University of Melbourne , Melbourne, Victoria 3010, Australia.
Brendan F
BF
Abrahams
School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
Stuart R
SR
Batten
School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
David R
DR
Turner