Anchoring a helical handle across a cavity:: the first 2,2′-bipyridyl-capped α-cyclodextrin capable of encapsulating transition metals

The reaction of 6,6 ' -bis(chlorocarbonyl)-2,2 ' -bipyridine with 6A,6D-diamino-6A,6D-dideoxy-2(A),2(B),2(C),2(D),2(E),2(F),3(A),3(B), 3(C),3(D),3(E),3(F),6(B),6(C),6(E),6(F)-hexadeca-O-methylcyclo maltohexaose (1) afforded the corresponding capped cyclodextrin derivative (LH) in which the nitrogen atoms are forced to point towards the cavity interior. As shown by a single crystal X-ray diffraction study, the capping handle adopts a helical shape. In silver(I) and palladium(II) complexes derived from LH, the metal centre is encapsulated and positioned at the entrance of the CD receptor. (C) 2001 Elsevier Science B.V. All rights reserved.