Synthesis and Structure of Heterospin Compounds Based on the [Mn6(O)2Piv10]-Cluster Unit and Nitroxide

Овчаренко, В. И.; Fursova, E. Yu.; Романенко, Г. В.; Ikorskiǐ, V. N.

doi:10.1021/ic049859y

Cited by 57 publications

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“…201 -209 This situation was found for the [Mn 6 (O) 2 Piv 10 (Thf) 2 (NIT-Me)Mn 6 (O) 2 Piv 10 (Thf)(CH 2 Cl 2 )(NIT-Me)] heterospin chain polymer complex, for which antiferromagnetic ordering was recorded below 3.5 K, and at 2 K, the spontaneous magnetic moment reached ∼ 2800 G·cm 3 /mol. 190,192 However, the bridging coordination of nitroxide sets strict requirements in terms of the spatial complementarity of the polymetallic nuclei and the bridging paramagnetic ligand. Of the whole class of 2-imidazoline nitronyl nitroxides, only L 20 , which contains a CH 3 (L 7 ), makes the bridging coordination mode of the O • -N-C=N→O fragment impossible because of the steric requirements of the tert-butyl pivalate groups with the atoms of the R group.…”

Section: Reactions Whose Products Retain Both the Multinuclear Fragmementioning

confidence: 99%

Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Овчаренко¹

2010

Stable Radicals

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IntroductionInteractions between the paramagnetic ions of transition metals and stable radicals are convenient and effective methods for the synthesis of multispin molecules. These metal-nitroxide systems are often called heterospin systems because they contain paramagnetic centers with both d (or f) odd electrons and centers with p electrons. Paramagnetic centers can differ in the electron spin, g factor, the character of electron spin density delocalization, and heat capacity. The presence of several paramagnetic centers in heterospin molecules has stirred growing interest in their magnetic properties because these compounds are convenient objects for studying the subtle peculiarities of exchange interactions and revealing valuable magnetostructural correlations. That is why coordination chemistry of transition metals with stable nitroxides is an actively developing direction in modern chemistry that contributes to problem solving in the field of molecular magnetism. The results of studies on the synthesis and properties of metal complexes with nitroxides have been considered from different viewpoints and at different times in many monographs and reviews. 1 -19 Importantly, this approach offers the potential for control over the structure of the designed heterospin molecule and the character of interactions between the odd electrons of paramagnetic centers, which is necessary for constructing justifiable magnetostructural correlations. This is one of the factors responsible for the continuous growth of the number of new metal-nitroxide complexes. The Cambridge Structural Database alone contains more than one thousand structurally defined metal-nitroxide systems. 20 Therefore, currently it is impossible and not necessary to collect all available literature data on the synthesis and properties of metal-nitroxide systems in one publication. In any account, a comprehensive review of this kind will already have become incomplete by the time of its publication because new heterospin compounds based on transition metal compounds with nitroxides are being added daily to the list. However, the Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron CompoundsEdited by Robin G. Hicks

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Section: Reactions Whose Products Retain Both the Multinuclear Fragmementioning

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Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Овчаренко¹

2010

Stable Radicals

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“…[1][2][3][4][5] In solid phases, some of these compounds exhibit bulk magnetization. 1, 4 However, what often complicates implementation of this synthetic ap proach is poor solubility of the starting polynuclear com plexes in organic solvents, due to which they cannot be introduced into reactions with nitroxides.…”

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Heterospin complexes of polynuclear NiII compounds containing hexafluoroacetylacetonate and pivalate ligands with nitroxides

et al. 2010

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The heterospin mixed ligand complex [Ni 6 (OH) 4 Piv 4 (hfac) 4 (NIT Ph) 2 ] (1) (NIT Ph is 4,4,5,5 tetramethyl 2 phenyl 4,5 dihydro 1H imidazol 1 oxyl 3 oxide, hfac is hexafluoro acetylacetonate, and Piv is pivalate) was synthesized. The method for the synthesis of complex 1 is based on the replacement of acetone molecules in the hexanuclear complex containing the hexafluoroacetylacetonate and pivalate ligands [Ni 6 (OH) 4 Piv 4 (hfac) 4 (Me 2 CO) 4 ] by NIT Ph molecules. Two monodentate NIT Ph molecules replace four acetone molecules, because the coordination of the O atom of the nitroxide group results in the blocking of one of the positions in the coordination environment of Ni II the access to which is hindered by the phenyl ring of NIT Ph. As a result, these ions are in a square pyramidal environment unusual of Ni II . In the low temperature range, the dependence of the magnetization of 1 on the magnetic field is described by the Brillouin function. The reaction of [Ni 6 Piv 4 (hfac) 4 (OH) 4 (Me 2 CO) 4 ] with the nitronyl nitroxide radicals 4,4,5,5 tetramethyl 2 (4 pyridyl) 4,5 dihydro 1H imidazol 1 oxyl 3 oxide (NIT p Py) or 4,4,5,5 tetramethyl 2 (1 methyl 1H imidazol 5 yl) 4,5 dihydro 1H imidazol 1 oxyl 3 oxide (NIT Iz) containing the pyridine or 1 methylimidazol 5 yl substituent, respectively, in the side chain is accompanied by the decomposition of the polynuclear frag ment and affords the mononuclear complexes Ni(hfac) 2 (NIT p Py) 2 and Ni(hfac) 2 (NIT Iz) 2 , respectively. The reaction of 4,4,5,5 tetramethyl 2 (1 methyl 1H imidazol 5 yl) 4,5 dihyd ro 1H imidazol 1 oxyl (Im Iz), which is the imine analog of NIT Iz, with [Ni 6 Piv 4 (hfac) 4 (OH) 4 (Me 2 CO) 4 ] afforded the decanuclear complex [Ni 10 (OH) 8 Piv 4 (hfac) 8 (Im Iz) 2 (H 2 O) 6 ]. The molecular and crystal structures of all heterospin compounds were determined, and the magnetic properties of all compounds were investigated in the 2-300 K temperature range.The interactions of polynuclear metal compounds with nitroxides serve as an efficient method for the synthesis of multispin compounds. 1-5 In solid phases, some of these compounds exhibit bulk magnetization. 1,4 However, what often complicates implementation of this synthetic ap proach is poor solubility of the starting polynuclear com plexes in organic solvents, due to which they cannot be introduced into reactions with nitroxides. In addi tion, the metal ions of the polynuclear fragment should possess high electron withdrawing ability to coordi nate weak donors such as the O atoms of the nitrox ide groups. Finally, the starting polynuclear fragment should contain easily replaceable terminal ligands. The recently described 6 mixed ligand hexanuclear complex [Ni 6 (OH) 4 Piv 4 (hfac) 4 (Me 2 CO) 4 ], meets theses require ments. Thus the pivalate anions (Piv) that are present in this complex provide the solubility in organic solvents, the hexafluoroacetylacetonate anions (hfac) enhance the elec tron withdrawing properties of the Ni II ions, and acetone molecules serve as easily replace...

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“…[1][2][3][4][5] The reactions of polynuclear metal trimethylacetates with paramagnetic organic compounds can initiate self assem bly of magnetoactive heterospin high dimensional struc tures. [6][7][8][9][10][11] The trimethylacetate anion is widely used as a ligand for the synthesis of polynuclear transition metal compounds. 12, 13 The Cambridge Structural Database con tains hundreds of structures of such compounds, includ ing heterometallic complexes.…”

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“…55, No. 11, November, 2006 metals (chain (1)(2)(3)(4)(5)(6)(7)(8), layer (9-11), or framework (5)). This tendency is indirectly associated with the fact that an increase in the ionic radius leads to an increase in the number of donor atoms, which can surround the metal ion and, consequently, to an increase in the number of the adjacent ions, to which the metal ion can be linked through bridging coordination of ligands.…”

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New type of compounds based on s-and d-block metal trimethylacetates

et al. 2006

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Heterometallic compounds based on alkali (Li, Na, K, Rb, or Cs) trimethylacetates and transition metal (Cu or Co) trimethylacetates were synthesized. These compounds are charac terized by a larger number of s block atoms compared to d block atoms. An excess alkali metal trimethylacetate in the reaction system leads to the formation of unusual polymeric systems containing alternating s and d block atoms.

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Synthesis and Structure of Heterospin Compounds Based on the [Mn₆(O)₂Piv₁₀]-Cluster Unit and Nitroxide

Cited by 57 publications

References 11 publications

Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Heterospin complexes of polynuclear NiII compounds containing hexafluoroacetylacetonate and pivalate ligands with nitroxides

New type of compounds based on s-and d-block metal trimethylacetates

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