Bis(m-phenylene)-32-crown-10-based cryptands, powerful hosts for paraquat derivatives.
Four new bis(m-phenylene)-32-crown-10-based cryptands with different third bridges were prepared. Their complexes with paraquat derivatives were studied by proton NMR spectroscopy, mass spectrometry, and X-ray analysis. It was found that these cryptands bind paraquat derivatives very strongly. Specifically, a diester cryptand with a pyridyl nitrogen atom located at a site occupied by either water or a PF(6) anion in analogous complexes exhibited the highest association constant K(a) = 5.0 x 10(6) M(-1) in acetone with paraquat, 9000 times greater than the crown ether system. X-ray structures of this and analogous complexes demonstrate that improved complexation with this host is a consequence of preorganization, adequate ring size for occupation by the guest, and the proper location of the pyridyl N-atom for binding to the beta-pyridinium hydrogens of the paraquat guests. This readily accessible cryptand is one of the most powerful hosts reported for paraquats.
Huang
Feihe
F
Department of Chemistry, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA.
Switek
Karen A
KA
Zakharov
Lev N
LN
Fronczek
Frank R
FR
Slebodnick
Carla
C
Lam
Matthew
M
Golen
James A
JA
Bryant
William S
WS
Mason
Philip E
PE
Rheingold
Arnold L
AL
Ashraf-Khorassani
Mehdi
M
Gibson
Harry W
HW
D018360:Crystallography, X-Ray; D004988:Ethers, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008968:Molecular Conformation; D015394:Molecular Structure; D010269:Paraquat / Q000031:analogs & derivatives* / Q000737:chemistry*; D012545:Schiff Bases / Q000138:chemical synthesis* / Q000737:chemistry
D004988:Ethers, Cyclic; D012545:Schiff Bases; C444241:cryptand; D010269:Paraquat