Formation of antiferromagnetically coupled C-60(center dot-) and diamagnetic (C-70(-))(2) dimers in ionic complexes of fullerenes with (MDABCO(+))(2)center dot(MTPP)-T-II (M = Zn, Co, Mn, and Fe) assemblies

摘要

A series of ionic multicomponent complexes comprising C-60 and C-70 anions and coordinating assemblies of methyldiazabicyclooctane cations with metal tetraphenylporphyrins, (MDABCO(+))(2)center dot(MTPP)-T-II center dot(C-60(70)(-))(2)center dot Sol. (C-60, M = Zn (1); C-60, M = Co (2); C-60, M = Mn (3); C-60, M = Fe (4); C-70, M = Mn (5); and C-70, M = Fe (6)) has been obtained. IR- and UV-vis-NIR spectra of 1-6 justified the formation of C-60(center dot-) in 1-4 and single-bonded (C-70(-))(2) dimers in 5 and 6. Co and Mn atoms are six-coordinated in the (MDABCO(+))(2)center dot(MTPP)-T-II units with relatively long M-N bonds of 2.475(2), 2.553(2), and 2.511(3) angstrom for 2, 3, and 5, respectively. Isostructural complexes 2, and 3 contain C-60(center dot-) zigzag chains separated by the (MDABCO(+))(2)center dot(MTPP)-T-II units, whereas in 5 the layers formed by the (C-70(-))(2) dimers alternate with those composed of the (MDABCO(+))(2)center dot(MnTPP)-T-II units and noncoordinating MDABCO(+) cations. Negative Weiss constants of -13 (1), -2 (3), and -2 (4) K indicate the antiferromagnetic interaction of spins, which decreases the magnetic moment of the complexes below 70-120 K. The EPR signals of 1 and 4 attributed to C-60(center dot-) are split into two components at the same temperatures, which broaden and shift to higher and lower magnetic fields with the temperature decrease. Complexes 2 and 3 show single EPR signals with g-factors equal to 2.1082 and similar to 2.4 at 293 K, respectively. These values are mean between those characteristic of (MTPP)-T-II and C-60(center dot-), and, consequently, the signals appear due to exchange coupling between these paramagnetic species. The antiferromagnetic ordering of C-60(center dot-) spins below 70-100 K shifts g-factor values closer to those characteristic of individual (MTPP)-T-II (g = 2.1907 (2) and similar to 4.9 (3) at 4 K). In contrast to 1-4, complex 5 shows paramagnetic behavior with Weiss constant close to 0.