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Updated: Jun 14, 2026
Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
Magnetic and structural transitions at dimerization of C(60)(*-) in ionic fullerene complexes with metalloporphyrins:
Dmitri V Konarev1, Salavat S Khasanov, Guzeliya R Mukhamadieva
1Institute of Problems of Chemical Physics RAS, Chernogolovka, Moscow region 142432, Russia. konarev@icp.ac.ru
Abstract:
Ionic complexes containing C(60)(*-) radical anions and metalloporphyrins coordinatively bound to N,N',N'-trimethylpiperazinium cations {(TMP(+))(2).M(II)TPP}.(C(60)(-))(2).(C(6)H(4)Cl(2))(2).(C(6)H(5)CN)(2) [M = Zn (1) and Mn (2)] have been obtained. The crystal structures of 1 and 2 solved at 250 and 270 K, respectively, show layered packing in which fullerene layers alternate with the (TMP(+))(2).M(II)TPP ones. Fullerenes form pairs in the layer with short center-to-center distances of 10.044 and 10.077 A, respectively. The structures of 1 and 2 solved at 100 K indicate the formation of singly bonded (C(60)(-))(2) dimers. That results in the transition of 1 from the paramagnetic to diamagnetic state accompanied by the disappearance of the electron paramagnetic resonance (EPR) signal of C(60)(*-) at 220-150 K. Dimerization in 2 results in a decrease in the magnetic moment from 6.36 to 6.00 mu(B) at 200-150 K and a change in the shape of EPR signal. The room-temperature EPR signal shows a major broad component at g = 2.0678 (DeltaH = 111.6 mT) attributed to both paramagnetic C(60)(*-) and high-spin (TMP(+))(2).Mn(II)TPP species having strong exchange interaction. After dimerization, the signal is characteristic of isolated high-spin Mn(II)TPP (g( perpendicular) = 6 with |A| = 7.3 mT and g(||) approximately 2). Two TMP(+) cations can coordinate to M(II) in (TMP(+))(2).M(II)TPP. However, a weak coordination bond is formed only with one cation with the M(II)...N(TMP(+)) distances of 2.489(2)-2.688(3) A. As a result, metal atoms displace by +/-0.232(3) A (1, 250 K), +/-0.231(1) A (1, 100 K) and +/-0.4684(7) A (2, 270 K) out of the porphyrin plane to be located above and below the porphyrin plane with equal occupancies for both positions. The symmetry of the crystal structure of 2 decreases from monoclinic to triclinic under cooling. That results in unequal 0.85/0.15 occupation of the Mn(II) positions at 100 K with displacement of the metal by 0.391(2) and 0.554(4) A, respectively.
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