title: Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride.
abstract: The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray structures are reproduced very well by DFT calculations. Similar endo,endo conformations are calculated for the bisamide crown ether derivatives 7, where two proximate and nearly parallel crown ether units endow the molecules with a claw-like molecular cleft or tweezer structure as evidenced by an enhanced ability to extract some alkali, alkaline earth and rare earth metal ions.
authors: Institute of Chemistry, Karl-Franzens University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
authors: Gert
authors: G
authors: Kollenz
authors: Institute of Chemistry, Karl-Franzens University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
authors: Ralf
authors: R
authors: Smounig
authors: Institute of Chemistry, Karl-Franzens University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
authors: Ferdinand
authors: F
authors: Belaj
authors: School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
authors: David
authors: D
authors: Kvaskoff
authors: School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
authors: Curt
authors: C
authors: Wentrup
keywords: carbamates; crown ethers; diisocyanate; isocyanate; ureas