160952-96-5

Upstream product

• 75-77-4 chloro-trimethyl-silane 

Relevant academic research and scientific papers

High-spin molecules: (NB un4) [Mn8O6Cl6(O2CPh)7(H 2O)2] (S = 11) and [Mn9Na2O7(O2CPh) 15(MeCN)2] (S = 4)

The syntheses and electrochemical and magnetochemical properties of (NBun4)[Mn8O6Cl6(O 2CPh)7-(H2O)2]·xCH 2Cl2 (2·xCH2Cl2) and [Mn9Na2O7(O2CPh) 15(MeCN)2]·3MeCN (3·3MeCN) are reported. Both complexes were prepared from reactions involving (NBun4) [Mn4O2(H2O)(O2CPh)9] (1). Complex 2 was obtained in 45-60% yield on treatment of complex 1 with 4 equiv of Me3SiCl in CH2Cl2. Complex 2·3/2CH2Cl2·2H2O crystallizes in triclinic space group P1 with the following cell parameters at -169 °C: a = 16.104(4) A?, b = 21.501(6) A?, c = 14.843(4) A?, α = 94.24(1)°, β = 105.96(1)°, γ = 89.07(1)°, V = 4927.79 A?3, and Z = 2. The structure was refined by employing 10 108 unique reflections with F > 3.0σ(F) to give R = 0.0912 and Rw = 0.0944. Complex 2 contains a [MH8O6Cl4]8+ core (8MnIII) that may be conveniently described as resulting from the fusion of two [MiLtO2J butterfly units by sharing one body or hinge Mn. An eighth MnIII ion is connected to the resultant [Mn7O4] unit by two additional bridging O2- ions. Complex 3 was obtained in 31% yield from the treatment of complex 1 with 1 equiv of benzoyl peroxide in MeCN, followed by addition of NaClO4. Complex 3·3MeCN crystallizes in triclinic space group P1 with the following cell parameters at -170 °C: a = 15.116(2) A? = 27.903(4) A?, c = 15.007(2) A?, α = 102.40(1)°, β = 112.36(1)°, γ = 84.17(1)°, V = 5715.26 A?3, and Z = 2. The structure was refined by employing 12 020 unique reflections with F > 3σ(F) to give R = 0.0514 and Aw = 0.0525. Complex 3 possesses a mixed-metal undecanuclear [Mn9Na2O7]15+ core (9MnIII); the Mn9O7 subcore again comprises a [Mn7O4] unit constructed from the fusion, in the same manner as for complex 2, of two [Mn4O2] butterfly units. There are now two additional MnIII ions connected to the [Mn7O4] unit, by three additional bridging O2- ions. The Na+ ions are bound to bridging O2- ions of the [Mn9O7] core, supporting a heterometallic-aggregate description rather than an ion-pairing description. Complex 2 displays reversible redox couples when examined by cyclic voltammetry in CH2Cl2; an oxidation and a reduction are observed at 0.91 and 0.12 V, respectively, vs ferrocene. Complex 3 displays no reversible processes. Variable-temperature and variable-field dc magnetic susceptibility data were collected for polycrystalline samples of complexes 2 and 3. In a 10.0 kG field, χMT for complex 2 increases with decreasing temperature from 23.7 cm3 K mol-1 (μeff = 13.8 μB) at 300.0 K to a maximum of 53.2 cm3 K mol-1 (μeff = 20.6 μB) at 15.0 K, whereupon there is a decrease to 39.3 cm3 K mol-1 (μeff = 17.7 μB) at 5.01 K. The shape of this χMT vs emperature curve reflects the population of a S = 11 ground state at low temperature. Least-squares fitting of reduced magnetization vs H/T data for complex 2 in the 2.0-30.0 K and 5.00-50.0 kG field range confirms that complex 2 has a 5 = 11 ground state with g = 1.92 and axial zero-field splitting of D = -0.04 cm-1. The ac susceptibility data measured in zero external field for complex 2 in the 2.0-30.0 K range also indicate a 5 = 11 ground state. No out-of-phase ac magnetic susceptibility signal was observed for complex 2 in the 2.0-30.0 K range in spite of its large-spin ground state. The absence of an out-of-phase ac signal is attributable to a very small zero-field splitting in the S = 11 ground state, and the small D-value results from a near cancellation of single-ion zero-field interactions at the eight MnIII ions in complex 2. Complex 3 exhibits dc and ac magnetic susceptibility data consistent with a 5 = 4 ground state. In a 10.0 kG field μeff decreases gradually from 12.23 μB at 320 K to 6.94 μB at 5.01 K. Even though there are some similarities in molecular structure between complexes 2 and 3, differences in the nature of spin frustration result in a S = 11 ground state for complex 2 and a S = 4 ground state for complex 3.