Positive heterotropic cooperativity for selective guest binding via electronic communications through a fused zinc porphyrin array.
Upon binding with C60 and diamines, such as 4,4'-bipyridine (bpy) and N,N,N',N'-tetramethylhexane-1,6-diamine (TMHDA), cyclic host 1 possessing two electronically coupled binding sites displays negative homotropic cooperativity and positive heterotropic cooperativity, and their ternary mixtures preferentially form inclusion complexes with hetero-guest pairs 1 supersetC60*bpy and 1 supersetC60*TMHDA under appropriate conditions. Spectroscopic titration profiles in toluene at 20 degrees C demonstrated that the association constants (Kassoc) of C60 with monodiamine complexes 1 supersetbpy (2.8 x 105 M-1) and 1 supersetTMHDA (1.5 x 105 M-1) are 8.5 and 4.5 times greater than that of C60 with guest-free 1 (3.3 x 104 M-1), respectively. On the other hand, mono-C60 complex 1 supersetC60 was 6.1 times more accessible than guest-free 1 toward TMHDA. Absorption spectroscopy in the absence of 1 indicated no direct interaction between C60 and diamines.
Sato
Hiroshi
H
Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
Tashiro
Kentaro
K
Shinmori
Hideyuki
H
Osuka
Atsuhiro
A
Murata
Yasujiro
Y
Komatsu
Koichi
K
Aida
Takuzo
T
D004553:Electric Conductivity; D008665:Metalloporphyrins / Q000737:chemistry*; D015394:Molecular Structure; D015032:Zinc / Q000737:chemistry*
D008665:Metalloporphyrins; D015032:Zinc