화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.114, No.45, 14408-14419, 2010
Convergent Synthesis and Photoinduced Processes in Multi-Chromophoric Rotaxanes
A series of [2]rotaxane materials, in which [60]fullerene is linked to a macrocycle and ferrocene (Fc) moieties are placed at the termini of a thread, both of which possess a central Cu(I)-1,10-phenanthroline [Cu(phen)(2)](+) complex, were synthesized by self-assembly using Sauvage metal template methodology Two types of threads were constructed one with terminal ester linkages and a second with terminal 1,2,3-triazole linkages derived from Cu(I)-catalyzed "click' 1,3-cycloaddition reactions Model compounds lacking the fullerene moiety were prepared in an analogous manner The ability of the interlocked Fc-[Cu(phen)(2)](+)-C-60 hybrids to undergo electron transfer upon photoexcitation in benzonitrile, dichloromethane, and ortho-dichlorobenzene was investigated by means of time-resolved fluorescence and transient absorption spectroscopy, using excitation wavelengths directed at the fullerene and [Cu(phen)(2)](+) subunits The energies of the electronic excited states and charge separated (CS) states that might be formed upon photoexcitation were determined from spectroscopic and electrochemical data These studies showed that MLCT excited states of the copper complex in the fullerenerotaxanes were quenched by electron transfer to the fullerene in benzonitrile, resulting in charge separated states with oxidized copper and reduced fullerene moieties, (Fc)(2)-[Cu(phen)(2)](2+)-C-60 (-) Even though electron transfer from Fe to the oxidized copper complex is predicted to be exergonic by 0 16 to 0 20 eV, no unequivocal evidence in support of such a process was obtained The conclusion that Fe plays no role in the photoinduced processes in our systems rests on the lack of enhancement of the lifetime of the charge separated state, as measured by decay of C-60 (-) at similar to 1000 nm, since one-electron oxidized Fe is very difficult to detect spectroscopically in the 500-800 nm spectral region