Low-Dimensional Organometallic Electron-Transfer Complexes. X-ray Structures and Magnetic Properties of α- and β-[Cr(C6Me3H3)2]+[TCNQ]

Dermot O’Hare, Michael D. Ward, Joel S. Miller

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Abstract

The reaction of donor, Cr(arene)2 (arene = C6Me6 and C6Me3H3), D, with the acceptor TCNQ, A, results in formation of electron-transfer salts of [D]•+[A]•− composition. Two phases of [Cr(C6Me3H3)2]•+[TCNQ]•− have been structurally characterized. The α-phase belongs to the centrosymmetric C2/c space group [α = 14.014 (4) Å, b = 16.347 (4) Å, c = 22.964 (6) Å, β = 107.44 (2)°, Z = 8, V = 5019 (5) Å3, T = 23 °C, R = 0.082] with the solid-state structure consisting of •••D•+D•+A22−D•+D•+••• linear chains. Each [TCNQ] in the [TCNQ]22− dimer is planar, and the intradimer separation is 3.47 Å. The anion-anion overlap is unusual as the dihedral angle between the planes normal to the long molecular axes is 31°. The β-phase crystallizes in the P21/c space group [a = 9.588 (5) Å, b = 16.390 (3) Å, c = 8.419 (6) Å, β = 106.84 (6)°, Z = 2, V = 1266 (9) Å3, T = 23 °C, R = 0.044] with the solid-state structure consisting of •••D•+A•−D•+A•−••• linear chains. The magnetic susceptibility of α-[Cr(C6Me6)2] [TCNQ] obeys the Curie-Weiss law with an effective moment, μeff, of 1.77 μB and θ of −0.1 K. This is consistent with the presence of a diamagnetic [TCNQ]22− dimer (v(C≡N) = 2156 m, 2175 s, and 2182 s cm−1). In contrast, [Cr(C6Me3H3)2] [TCNQ] does not obey the Curie-Weiss law but can be fit to an expression that accounts for contributions from independent Curie spins for the cation and a thermally activated triplet state for the dimerized anions [ΔE = 315 K, 0.027 eV, 219 cm−1, 0.44 kcal/mol].

Original languageEnglish (US)
Pages (from-to)758-763
Number of pages6
JournalChemistry of Materials
Volume2
Issue number6
DOIs
StatePublished - Nov 1 1990

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ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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