Structure, Optical, and Magnetic Properties of (PPN~+)_2(C_(70)~(2-))·2C_6H_4Cl_2, which Contains Dianionic Polymeric (C_(70)~(2-))_n Chains

摘要

A new salt, (PPN~+)_2 (C_(70)~(2-))·2C_6H_4Cl_2 (1), which contains C_(70)~(2-) dianions, has been obtained as single crystals (PPN~+ = bis(triphenylphosphine) iminium cation). The C_(70)~(2-) dianions form polymeric zigzag (C_(70)~(2-))_n chains, in which the fullerene units are bonded through single C-C bonds of length 1.581(5)-1.586(6) A. The distance between the centers of neighboring C_(70)~(2-) units is 10.441 A. The optical and magnetic properties of (C_(70)~(2-))_n have also been studied. Decreasing the symmetry of C_(70) in the polymer activate about 20 new IR bands in addition to the 10 IR-active bands of the starting C_(70). The polymeric structure shows absorptions in the visible and NIR regions, with three main bands at 890, 1200, and 1550 nm, instead of one band of isolated C_(70)~(2-) dianions at 1165-1184 nm. We concluded that the (C_(70)~(2-))_n polymer was diamagnetic, with a negative molar magnetic susceptibility of -3.82×10~(-4) emumol~(-1) per C_(70)~(2-) dianion. The polymer is EPR silent and a weak narrow EPR signal in salt 1 is due to impurities, which only constitute 0.84% of spin S = 1/2 of the total amount of fullerene C_(70).