Effect of N,N,N$\prime$-trimethylpiperazinium (TMP$\mathplus$) cations on magnetic properties and dimerization of fullerenes in the (TMP$\mathplus$)(CoIIporphyrin)(C60-) saltsстатья
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Аннотация:New salts of fullerene C60(•-) radical anions with N,N,N′ -trimethylpiperazinium cations (TMP+) containing neutral cobalt(II) porphyrin molecules: {(TMP+)⋅Co(II)OEP}⋅(C60(•-))⋅2C6H4Cl2⋅C6H5CN (1) and (TMP+)3{Co(II)TMPP⋅(C60(-))}2(C60(•-))⋅C6H4Cl2⋅C6H5CN (2) have been obtained (OEP and TMPP are octaethyl- or tetrakis(4-methoxyphenyl)porphyrins, respectively). In these salts the C60(•-) radical anions or the TMP+ cations with free nitrogen atom can coordinate to cobalt(II) porphyrinsand form Co-C(C60(-)) or Co-N(TMP+) bonds. The properties of these salts and the possibility of fullerene dimerization depend on type of bonds formed. For example, TMP+ cations in 1 form coordination (TMP+)⋅Co(II)OEP assemblies preserving free non-bonded C60(•-) radical anions. They are effectively coupled with S = 1/2spins localized on Co(II)OEP (Weiss temperature is 27 K and decrease of magnetic moment of 1 is observed below 150 K). Previously the {(MDABCO+)⋅CoIITMPP}2⋅(C60(-))2⋅(C6H4Cl2)2.5⋅(C6H5CN)1.5 salt was obtained in which doubly-bonded (C60(-))2 dimers were found. In contrast to this salt, TMP+ cations in 2 preserved uncoordinated allowing the formation of the Co-C(C60(-)) bond of 2.273(3) Å length in the diamagnetic σ-bonded Co(II)TMPP⋅(C60 (-)) anions. In coordinated state, fullereneanions cannot dimerize in 2 in spite of that their mutual arrangement and short interfullerene distances are favorable for such dimerization. Thus, variation of cations in the (Cation+)(Co(II)porphytin)(C60(-)) salts drastically affects their properties and allows one to control dimerization of fullerene anions.