New Tetraazaannulene Hosts for Fullerenes

Two modifications to the doubly concaved host molecules based on well-known nickel tetraazaannulene complexes have resulted in the preparation of the compounds Ni(NapTMTAA)center dot 2benzene, 1,6,8,15,17-tetramethyldinapthalene-5,9,14,18-tetraazacyclotetradecinatonickel(II), and Ni(Cl(4)TMTAA)center dot CH2Cl2, 2,3,11,12-tetrachloro-6,8,15,17-tetramethyldibenzo-5,9,14,18-tetraazacyclotetradecinatonickel(II). When crystallized with C-60 in carbon disulfide, the crystalline, well-ordered, host-guest compounds Ni(NapTMTAA)center dot C-60 center dot 2CS(2) and Ni(Cl(4)TMTAA)center dot C-60 center dot 2CS(2) were formed. The compounds were characterized by X-ray crystallography. The crystal structures of the precursor host molecules showed very strong host-host interactions, particularly in the case of Ni(Cl(4)TMTAA), which had short Ni center dot center dot center dot Ni interactions of 3.3860(11) and 3.5888(11) angstrom in the two different dimers in the asymmetric unit; yet, these host-host interactions were entirely destroyed in the resultant host-guest compounds, and C-60 molecules were shown to make use of both cusps of the host macrocycle in the formation of a shape-selective arrangement.