title: Piperazine Functionalization of C70for Incorporation into Supramolecular Assemblies.
abstract: The photochemical reaction of piperazine with C70produces a mono-adduct (N(CH2CH2)2NC70) 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)2NI2C70that was formed by reaction of N(CH2CH2)2NC70with I2. Crystals of polymeric {Rh2(O2CCF3)4N(CH2CH2)2NC70}n⋅nC6H6that formed from reaction of the mono-adduct with Rh2(O2CCF3)4contain a sinusoidal strand of alternating molecules of N(CH2CH2)2NC70and Rh2(O2CCF3)4connected through Rh-N bonds. Silver nitrate reacts with N(CH2CH2)2NC70to form black crystals of {(Ag(NO3))4(N(CH2CH2)2NC70)4}n⋅7nCH2Cl2that contain parallel, nearly linear chains of alternating (N(CH2CH2)2NC70molecules and silver ions. Four of these {Ag(NO3)N(CH2CH2)2NC70}nchains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non-polar C70cages encircling that core. Of the three bis-adducts, one was definitively identified through crystallization in the presence of I2as12{N(CH2CH2)2N}2C70with addends on opposite poles of the C70cage and a structure with C2vsymmetry. In12{I2N(CH2CH2)2N}2C70, individual12{I2N(CH2CH2)2N}2C70units 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 I2is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize.
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Amineh
authors.initials: A
authors.lastname: Aghabali
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Jun
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.affiliation: Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Balch
keywords: X-ray crystallography; crystalline polymer; fullerenes; iodine; piperazine