Spectral and theoretical studies on effective and selective non-covalent interaction between tetrahexylporphyrins and fullerenes.
The host-guest interaction of zinc(II) 5,10,15,20-tetrahexylporphyrin (Zn-THP) and its free base (H2-THP) with fullerenes (C60 and C70) has been studied in toluene medium. Binding constants (K) for H2- and Zn-THP complexes of fullerenes were determined by UV-vis, fluorescence and NMR spectroscopic techniques. Large K values of C70/THP complexes (KC70 ) were obtained in the range of 1.4-2.5 x 10(4)M(-1), while those of C60/THP complexes (KC60) were smaller (1.0-3.2 x10(3)M(-1)). These results show that the KC70 is about 10 times as large as KC60 in both THPs (KC70/KC60 = 10). Enthalpies of formation (DeltaHf degrees) for various fullerene/THP complexes were estimated by ab initio calculations; DeltaHf degrees for C60/H2-THP, C70/H2-THP, C60/Zn-THP and C70/Zn-THP complexes are 5.82, 2.80, 2.31 and 1.54 kcal mol(-1), respectively. The trends in DeltaHf degrees support the experimental results of selective complexation of THPs towards C70 over C60 and fullerenes towards Zn-THP over H2-THP.
Bhattacharya
Sumanta
S
Department of Chemistry, Shiga University of Medical Science, Seta, Otsu, Japan. sumanta@belle.shiga-med.ac.jp
Ujihashi
Naruto
N
Aonuma
Shuji
S
Kimura
Takahide
T
Komatsu
Naoki
N
D037741:Fullerenes / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D011166:Porphyrins / Q000737:chemistry*; D011522:Protons; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
D037741:Fullerenes; D011166:Porphyrins; D011522:Protons