کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1407201 1501874 2008 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Preparation and characterization of new Mn6 and Mn8 clusters obtained from the in situ formation of an unprecedented octadentate ligand
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Preparation and characterization of new Mn6 and Mn8 clusters obtained from the in situ formation of an unprecedented octadentate ligand
چکیده انگلیسی

The use of 1,3,5-trihydroxybenzene (thbH3) in manganese carboxylate chemistry has been investigated. The reactions of thbH3 with 4 and 6 equivalents of Mn(O2CEt)2 in MeOH afford the complexes [Mn6(O2CEt)8(L)(MeOH)4(H2O)2] (1) and [Mn8O2(O2CEt)14(MeOH)4] (2), respectively. In the case of complex 1, the product of the in situ organic ligand transformation has been observed, namely the conversion of the tridentate thbH3 group to a new octadentate ligand L4−; the latter has never been previously reported. Both complexes possess rare topologies, with 1 containing 6MnII ions, whereas 2 is mixed-valent 6MnII, 2MnIII. The core of 1 consists of two [Mn3(μ3-OR)]5+ triangles linked by the bulky octadentate ligand L. The [Mn8(μ4-O)2(μ-OR)8]6+ core of 2 can be considered an extension of the common [Mn6(μ4-O)2]10+ (4MnII, 2MnIII) core, comprising two edge-sharing tetrahedra, with two additional Mn atoms at one end. Peripheral ligation in both 1 and 2 is provided by eight and fourteen bridging EtCO2- groups, respectively. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1 and 2 in the 1.8–300 K range. The magnetic susceptibility data for 1 were fit to the theoretical χM vs T expression, derived by the use of an isotropic Heisenberg spin Hamiltonian and the Van Vleck equation, for two essentially non-interacting triangular [Mn3(μ3-OR)(μ-OR)2]3+ units. The fitting procedure revealed the two pairwise exchange parameters to be weakly ferromagnetic (Jbasal = J′ = + 0.79(3) cm−1) and antiferromagnetic (Jside = J = −2.04(3) cm−1), respectively, resulting in an S = 5/2 spin ground state. In contrast, the data for 2 revealed dominant antiferromagnetic interactions and a resulting S = 0 ground state; the latter value is rationalized in terms of the strong antiferromagnetic coupling within the central Mn2IIIO2 unit.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Structure - Volume 890, Issues 1–3, 12 November 2008, Pages 263–271
نویسندگان
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