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Design of Molecular and Ionic Complexes of Fullerene C60 with Metal(II) Octaethylporphyrins, MIIOEP (M = Zn, Co, Fe, and Mn) Containing Coordination M−N(ligand) and M−C(C60) Bonds

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posted on 2009-02-04, 00:00 authored by Dmitri V. Konarev, Salavat S. Khasanov, Gunzi Saito, Rimma N. Lyubovskaya
The formation of coordination bonds between metalloporphyrins and N-containing ligands or C60•− was used to prepare molecular and ionic complexes of C60 with metal(II) octaethylporphyrins: {MIIOEP·DABCO}·C60·(Solvent) (M = Zn (4) and Co (5)); {(MDABCO+)·MIIOEP}·(C60•−)·(Solvent) (M = Zn (6), Fe (8), and Mn (9)), (MQ+)·{CoIIOEP·(C60)}·C6H4Cl2 (10) and {(DMETEP+)·ZnIIOEP}·(C60•−)·(C60)0.5·C6H4Cl2 (12). New molecular complexes of C60 with ligand free metalloporphyrins MIIOEP·C60·(Solvent)1.5 (M = Zn (1), Co (2), and Fe (3)) were also obtained for comparison. Complexes 13 contain alternating pairs of C60 and MIIOEP molecules, whereas isostructural complexes 410 contain porphyrin channels accommodating zigzag fullerene chains. Complex 12 is a first example of fullerene complex containing simultaneously charged and neutral fullerene species arranged in zigzag chains and cavities formed by two (DMETEP+)·ZnOEP units. The coordination of DABCO, MDABCO+, DMETEP+, C60, and C60•− to MIIOEP was studied and their coordination abilities were compared. C60 weakly coordinates to FeIIOEP and CoIIOEP porphyrins with rather short M···C(C60) distances of 2.622 Å (3) and 2.685 Å (2). Only one N-containing ligand (L or L+) coordinates to MIIOEP in 49 and 12 to form five-coordinated L(L+)·MIIOEP species with the M···N(L or L+) bond lengths of 2.18−2.39 Å. These bonds are shorter by 0.049−0.055 Å for DABCO than for the MDABCO+ cation, and by 0.214 Å than for the DMETEP+ cation. Fullerenes are located from the opposite side of the porphyrin macrocycle relative to L (L+). They are essentially weaker ligands than L (L+) and form M···C(C60 or C60•−) distances longer than 2.84 Å. Neutral complex 3 with FeIIOEP in intermediate (S = 1) spin state manifests a Weiss temperature of 2.6 K. C60•− coexists with diamagnetic ZnIIOEP in 6 and high-spin FeIIOEP and MnIIOEP in 8 and 9. The Weiss temperatures of −17.8, −42.0, and −2.5 K, respectively, indicate antiferromagnetic coupling of spins in these complexes. The MQ+ cation is not coordinated to CoIIOEP in 10 providing the formation of stable Co−C(C60) coordination bonds of 2.266(3) Å length and diamagnetism of the complex.

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