The photochemical reaction of piperazine with C-70 produces a mono-adduct (N(CH2CH2)(2)NC70) in high yield (67) along with three bis-adducts. These piperazine adducts can combine with various Lewis acids to form crystalline supramolecular aggregates suitable for X-ray diffraction. The structure of the mono-adduct was determined from examination of the adduct I2N(CH2CH2)(2)NI2C70 that was formed by reaction of N(CH2CH2)(2)NC70 with I-2. Crystals of polymeric {Rh-2(O2CCF3)(4)N(CH2CH2)(2)NC70}(n).nC(6)H(6) that formed from reaction of the mono-adduct with Rh-2(O2CCF3)(4) contain a sinusoidal strand of alternating molecules of N(CH2CH2)(2)NC70 and Rh-2(O2CCF3)(4) connected through Rh-N bonds. Silver nitrate reacts with N(CH2CH2)(2)NC70 to form black crystals of {(Ag(NO3))(4)(N(CH2CH2)(2)NC70)(4)}(n).7nCH(2)Cl(2) that contain parallel, nearly linear chains of alternating (N(CH2CH2)(2)NC70 molecules and silver ions. Four of these {Ag(NO3)N(CH2CH2)(2)NC70}n chains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non-polar C-70 cages encircling that core. Of the three bis-adducts, one was definitively identified through crystallization in the presence of I-2 as (12){N(CH2CH2)(2)N}(2)C-70 with addends on opposite poles of the C-70 cage and a structure with C-2v symmetry. In (12){I2N(CH2CH2)(2)N}(2)C-70, individual (12){I2N(CH2CH2)(2)N}(2)C-70 units are further connected by secondary I2...N2 interactions to form chains that occur in layers within the crystal. Halogen bond formation between a Lewis base such as a tertiary amine and I-2 is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize.
展开▼
