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Issue 14, 2005
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Versatility of 2,6-diacetylpyridine (dap) hydrazones in stabilizing uncommon coordination geometries of Mn(II): synthesis, spectroscopic, magnetic and structural characterization

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Abstract

Five seven- or eight-coordinate manganese complexes of hydrazone ligands have been prepared. Three seven-coordinate neutral MnII complexes: [Mn(dapA2)]n (1), [Mn(dapB2)(H2O)2] (2), [Mn(dapS2)(H2O)2] (3) have been synthesized from the bis-Schiff bases of 2,6-diacetylpyridine: dap(AH)2, dap(BH)2 and dap(SH)2 (AH = anthraniloyl hydrazide, BH = benzoyl hydrazide, SH = salicyloyl hydrazide), respectively. Two eight-coordinate MnII complexes: [Mn(dapS)2] (4) and [Mn(dapB)2]·3H2O (5) have been synthesized from the mono-Schiff bases dapBH and dapSH, respectively. The complexes have been characterized by elemental analyses and by IR, UV-Vis., FAB mass, EI mass and EPR spectroscopy. The molecular structures of 1, 3·DMF and 4·DMF have been determined by single-crystal X-ray diffraction. The mono-Schiff bases are monoanionic and the bis-Schiff bases are dianionic. The octa-coordinated mono-Schiff base complex 4 adopts a dodecahedral geometry, while the hepta-coordinated bis-Schiff base complex 1 forms a one-dimensional linear polymeric chain. A weak antiferromagnetic exchange interaction (J = −0.15 cm−1) between the Mn(II) ions in 1 is attributed to weak Mn⋯Mn interaction through the PhNH2 moiety of the ligand, as indicated by extended-Hückel molecular orbital calculations. A good simulation of the EPR spectrum of a frozen solution (DMSO at 4 K) of compound 1 was obtained with g = 2.0, D = 0.1 cm−1, E = 0.01 cm−1. The EPR spectrum of a powdered sample of compound 1 shows a large broadening of the signal, due in part, to the important zero-field splitting of the hepta-coordinated Mn(II) ion.

Graphical abstract: Versatility of 2,6-diacetylpyridine (dap) hydrazones in stabilizing uncommon coordination geometries of Mn(ii): synthesis, spectroscopic, magnetic and structural characterization

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Publication details

The article was received on 17 Mar 2005, accepted on 03 Jun 2005 and first published on 15 Jun 2005


Article type: Paper
DOI: 10.1039/B503891J
Citation: Dalton Trans., 2005, 2428-2435
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    Versatility of 2,6-diacetylpyridine (dap) hydrazones in stabilizing uncommon coordination geometries of Mn(II): synthesis, spectroscopic, magnetic and structural characterization

    S. Naskar, D. Mishra, S. Kumar Chattopadhyay, M. Corbella and A. J. Blake, Dalton Trans., 2005, 2428
    DOI: 10.1039/B503891J

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