Change of Connectivity on Catenane Ring: Ring Expansion by Annulation−Ring Scission Sequence
摘要:
[GRAPHICS]Ring expansion of a catenane without destruction of the interlocked structure was attained by Diels-Alder reaction followed by ozonolysis. Annulation by Diels-Alder reaction introduced a C4 fragment onto the ring, and the ozonolysis scissored the resulting double bond to expand the catenane ring. The annulation-ring scission sequence provides a general approach for changing the connectivity on a catenane ring without destroying the interlocked structure.
Change of Connectivity on Catenane Ring: Ring Expansion by Annulation−Ring Scission Sequence
摘要:
[GRAPHICS]Ring expansion of a catenane without destruction of the interlocked structure was attained by Diels-Alder reaction followed by ozonolysis. Annulation by Diels-Alder reaction introduced a C4 fragment onto the ring, and the ozonolysis scissored the resulting double bond to expand the catenane ring. The annulation-ring scission sequence provides a general approach for changing the connectivity on a catenane ring without destroying the interlocked structure.
Synthesis of [60]fullerene (C60)-functionalized rotaxanes via Diels–Alder reactions with C60 is described. Diels–Alder reaction of C60 and sulfolene moiety as masked diene attached on the wheels of rotaxanes results in high yields of C60 incorporation. Rotaxanes are prepared by tin-catalyzed urethane-forming end-capping reaction with isocyanate of pseudorotaxane having the wheel carrying C60 functionality
Syntheses of [60]Fullerene and<i>N,N</i>-Bis(4-biphenyl)aniline-Tethered Rotaxane: Photoinduced Electron-Transfer Processes via Singlet and Triplet States of [60]Fullerene
作者:Atula S. D. Sandanayaka、Kei-ichiro Ikeshita、Nobuhiro Watanabe、Yasuyuki Araki、Yoshio Furusho、Nobuhiro Kihara、Toshikazu Takata、Osamu Ito
DOI:10.1246/bcsj.78.1008
日期:2005.6
A rotaxane containing [60]fullerene (C60) and N,N-bis(4-biphenyl)aniline (BBA) moieties was synthesized. In this structure, C60 acting as an electron acceptor, is attached to the crown-ether ring through which the axle with terminal BBA moieties acting as electron donors on both ends is penetrating. This rotaxane had a neutral amide moiety in the center of the axle in which two BBA moieties act as stoppers. The intra-rotaxane photoinduced electron-transfer processes of the C60 and BBA moieties were investigated by time-resolved transient absorption and fluorescence measurements while changing solvent polarity and temperature. Time-resolved transient absorption measurements of the rotaxanes confirmed that the long-lived charge-separated state (C60•−; BBA•+)rotaxane was formed via both the excited singlet and triplet states of C60 (1C60* and 3C60*, respectively) in polar solvents. The rate constants for charge-separation process were evaluated to be in the range of (3.6–3.7) × 108 s−1 via 1C60* and (5.1–5.6) × 107 s−1 via 3C60* in the ratio of (0.36–0.38):(0.43–0.51). The rate constants of charge recombination were 2.5 × 106 s−1 and 4.4 × 106 s−1, corresponding to the lifetimes of the charge-separated states of 400 ns and 230 ns in THF and benzonitrile, respectively. By the temperature dependences, the activation free-energy changes of charge-separation process via 3C60* were evaluated to be 0.10 eV, while those of the charge-recombination process were estimated to be 0.03 eV in THF and benzonitrile. These low activation energies are one of the characteristics of through-space electron transfer in the rotaxanes.
[GRAPHICS]Ring expansion of a catenane without destruction of the interlocked structure was attained by Diels-Alder reaction followed by ozonolysis. Annulation by Diels-Alder reaction introduced a C4 fragment onto the ring, and the ozonolysis scissored the resulting double bond to expand the catenane ring. The annulation-ring scission sequence provides a general approach for changing the connectivity on a catenane ring without destroying the interlocked structure.