Preparation and ionicity of C60 charge transfer complexes

Development of Conductive Organic Molecular Assemblies: Organic Metals, Superconductors, and Exotic Functional Materials

“…4,4 0 -dinitrobiphenyl complexes with benzidines, biphenyls, etc. 429,430 and C 60 complexes with OMTTF, 246 ET, 431 etc. ).…”

“…This finding is mainly associated with the isolated structure of C 60 À due to the presence of neutral donor molecules, which was confirmed by structural refinement of the TBPDA complexes (Chart 19). tures that C 60 has a fairly weak electron-accepting ability 246 and the molecular symmetry of the organic donors is low, turn down the electronic structure similar to that of A 3 C 60 . However, some CT complexes with donors containing transition-metals have shown a semiconductive behavior with relatively high RT conductivities; 1030 Also, it has been reported that the C 60 -based salt with organic dye cations shows an increase in conductivity as temperature decreases in the temperature range of 100-150 K. 1083 …”

“…The CT complex OMTTF Á C 60Á PhH has a neutral character with 2D C 60 layers sandwiched by the other components (Fig. 149b), 246 and the K-and Rb-dopings give rise to the appearance of superconductivity below 17-19 and 23-26 K, respectively. 1072,1073 Both temperatures are less than those of corresponding A 3 C 60 superconductors (19 K for A ¼ K and 29 K for A ¼ Rb), and the Raman spectrum of the Rbdoped compound shows a downshift of tangential A g (2) mode (1468 cm À1 for neutral C 60 ) to 1453 cm À1 , indicating the reduction to C 60 2À instead of C 60 3À .…”

“…148b). 246 Owing to the spherical shape of fullerenes, it is commonly observed that flat donor molecules are deformed and/or solvent molecules are accommodated in CT solids, such as (C 2 TET-TTF)(C 60 ) 2 , 1012 (ET) 2 C 60 ( Fig. 149a), 1013 and OMTTF Á C 60Á PhH (Fig.…”

“…149b). 246 Besides the monomeric form, a large variety of dimeric and polymeric fullerenes have so far been prepared as summarized in Table 34. The fullerenes exhibit a reversible phase transition attributable to the dissociation from polymeric (or dimeric) to monomeric phase in a certain temperature range.…”