Ionic and neutral C60 complexes with coordination assemblies of metal tetraphenylporphyrins, MIITPP2.DMP (M=Mn, Zn). Coexistence of (C60-)2 dimers bonded by one and two single bonds in the same compound.
Coordination assemblies of metal tetraphenylporphyrins, MIITPP2.DMP (M=Mn, Zn) were shown to form ionic multicomponent and neutral complexes with fullerene, {(MnIITPP)2.DMP}.(C60-)2.(DMETEP+)2.(C6H4Cl2)5 (1) and {(ZnTPP)2.DMP}.(C60)2.(C6H5Cl)4 (2), where DMP=N,N'-dimethylpiperazine and DMETEP+=the cation of N,N'-dimethyl-N'-ethylthioethylpiperazine. The crystal structure of 1 contains zigzag chains of the (C60-)2 dimers alternating with the DMETEP+ cations in the channels formed by the (MnIITPP)2.DMP units, whereas in 2 zigzag chains of the C60 molecules are separated by the (ZnTPP)2.DMP units and C6H5Cl molecules. The (MIITPP)2.DMP assemblies (M=Mn, Zn) have axial M-N(DMP) bonds of 2.315(2) and 2.250(2) A length, average equatorial M-N(DMP) bonds elongated to 2.141(3) and 2.077(2) A, and MII atoms displaced from the porphyrin plane toward the ligand by 0.677 and 0.485 A, respectively. The single-bonded sigma-(C60-)2 dimer coexists in 1 with the (C60-)2 dimer bonded by two single bonds with 86/14 occupancy factors. The sigma-(C60-)2 dimers are unusually stable and begin to dissociate only above a temperature of 320-330 K that results in the increase of the magnetic moment of 1 from 8.33 microB (320 K) to 8.66 microB (360 K). The electron paramagnetic resonance (EPR) signal of the dimeric phase (T<320 K) with the features spread over the range of 0-0.7 T was attributed to the interacting Mn2+ centers in the (MnIITPP)2.DMP units. The dissociation of the sigma-(C60-)2 dimers to the EPR-active C60*- radical anions manifests a new broad Lorenz signal above 320 K with g=2.0179 and DeltaH=65.5 mT. This signal can appear due to the exchange coupling between paramagnetic (MnIITPP)2.DMP and C60*- species. The vis-NIR spectrum of the sigma-(C60-)2 dimers is discussed.
Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. konarev@icp.ac.ru
Dmitri V
DV
Konarev
Salavat S
SS
Khasanov
Gunzi
G
Saito
Akihiro
A
Otsuka
Rimma N
RN
Lyubovskaya