Valence tautomerism of a novel polymeric Mn(II) species (original) (raw)
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Preparation and crystal structures of MnII, mixed-valent MnII/MnIII, and MnIII polymeric compounds
Polyhedron, 2003
The preparation and crystal structures of three polymeric Mn compounds are reported. The comproportionation reaction between Mn(OAc) 2 ×/4H 2 O and KMnO 4 in MeOH Á/AcOH (2:3) leads to isolation of {[Mn(OH)(OAc) 2 ] ×/AcOH ×/H 2 O} n (1). The structure consists of chains of [Mn(m-OH)(m-OAc) 2 Mn] triply-bridged units. The chains are linked into 3D networks by hydrogenbonding interactions involving the AcOH and H 2 O molecules of crystallization. Oxidation of [Mn 12 O 12 (O 2 CPh) 16 (H 2 O) 4 ] by controlled potential electrolysis in CH 2 Cl 2 with NBu n 4 PF 6 as supporting electrolyte yields a brown solution which slowly turns purple and then pale yellow. Deep purple crystals, obtained by addition of hexanes, were identified crystallographically as {(NBu n 4)[Mn 2 (O 2 PF 2) 6 ]×/2/3CH 2 Cl 2 } n (2), which is mixed-valent and consists of a chain of [Mn II (m-O 2 PF 2) 3 Mn III ] triply-bridged units. Bond distances, bond valence sum calculations, and a Jahn Á/Teller (JT) axial elongation at the Mn III sites confirm a trappedvalence situation. Dissolution of Mn(OAc) 2 ×/4H 2 O in EtOH results in a subsequent crystallization of a white solid analyzing as [Mn(OAc) 2 ×/3/8H 2 O] (3a). Crystals grown from MeOH Á/Et 2 O were structurally identified as [Mn 4 (OAc) 8 (MeOH) 2 ] n (3b), and consist of Y-shaped Mn 4 units bridged by AcO (groups to give a 3D network. Variable-temperature, solid-state magnetic susceptibility studies establish that 1, 3a and 3b are antiferromagnetically coupled to give diamagnetic ground states.
Polyhedron, 2014
Five polymeric Mn(II) complexes with bridging carboxylato groups were prepared and structurally characterized. The bridging carboxylato ligand in double-chain coordination polymeric structures of [Mn(l-3-NO 2 bz) 2 (bipy)] n ÁnH 2 O, [Mn(l-3,5-(NO 2 ) 2 bz) 2 (bipy)] n , [Mn(l-5-(NO 2 )sal) 2 (bipy)] n , and [Mn(l-5-(NO 2 )sal) 2 (phen)] n , where 3-NO 2 bz À = 3-nitrobenzoate, 3,5-(NO 2 ) 2 bz À = 3,5-dinitrobenzoate, 5-(NO 2 )sal À = 5-nitrosalicylate, bipy = 2,2 0 -bipyridine and phen = 1,10-phenanthroline, exhibits the syn-anti bidentate bridging mode. The Mn(II) atom in the coordination polymer [Mn(l-4-NO 2 bz)(4-NO 2 bz)(phen)(H 2 O)] n , where 4-NO 2 bz = 3-nitrobenzoate, is coordinated by terminal carboxylato groups in the syn monodentate mode but two Mn(II) atoms are connected with bridging 4-nitrobenzoate ligands in the anti-anti bidentate bridging mode. The magnetic susceptibility and magnetization data confirm that weak exchange interactions of an antiferromagnetic nature apply in these complexes.
Inorganic Chemistry, 2001
The reaction of [Mn 3 O(2-X-benzoato) 6 L 3 ] (X ) Cl, Br; L ) pyridine) with 2,2′-bipyridine in CH 2 Cl 2 leads to the high-yield formation of new mixed-valence tetranuclear Mn II Mn 3 III complexes of general formulation [Mn 4 O 2 -(X-benzoato) 7 (bpy) 2 ] (1, X ) 2-chloro; 2, X ) 2-bromo). The crystal structure of 1 was determined. Complex 1 crystallizes in the monoclinic system, space group P2 1 /n with a ) 19.849(8) Å, b ) 13.908(5) Å, c ) 30.722(19) Å, ) 107.35(2)°, Z ) 4. Complex 1 is neutral, and consideration of overall charge necessitates a mixed-valence Mn II Mn III 3 description. Each manganese ion is distorted octahedral, especially the three Mn III ions, owing to a first-order Jahn-Teller effect. The Mn II is assigned on the basis of the longer metal-ligand distances. Variable temperature magnetic susceptibility studies were performed on 1 and 2 in the temperature range 2-300 K. The topology of the molecule requires three J values, J bb between the two-body Mn III ions and two J wb ("wing-body") between the Mn III ions of the "body" of the butterfly and the Mn II or Mn III of the "wing" of the butterfly. Without any simplifying assumptions, a full diagonalization matrix method is necessary to solve the problem, but assuming that both J wb are identical, it is then possible to solve the problem numerically by applying the Kambe method. With both methods, the derived J bb and J wb exchange parameters are very similar for the 2-Cl and 2-Br complexes. The best R factors [∑ i ( Mcalc -Mobs ) 2 /∑ i ( Mobs ) 2 ] (∼10 -6 ) were obtained from 300 to 40 K. The J values are, thus, as follows. For 1, J bb ) -23.2 cm -1 , J wb ) -4.9 and -4.8 cm -1 , and g ) 1.93. For 2, J bb ) -22.8 cm -1 , J wb ) -4.8 and -4.7 cm -1 , and g ) 1.92. With these values, the expected ground-state spin must be 7 / 2 , very close in energy to low-lying spin states of 9 / 2 , 5 / 2 , 3 / 2 , and 1 / 2 . They are all almost degenerate. By application of Kambe's method (with only one J wb ), the results are completely similar. Magnetization measurements at 2-30 K from 2 to 50 kG confirm that the ground state is S ) 7 / 2 for 1, with the D parameter equal to -0.60 cm -1 .
Dalton Transactions, 2011
The syntheses and characterizations are reported for six new homo-and heterovalent manganese clusters, utilizing pyridyl functionalized b-diketones ligands. The reaction of the trinuclear complex [Mn 3 O(O 2 CPh) 6 (H 2 O)(Py) 2 ] with 1,3-di(pyridine-2-yl)propane-1,3-dione (dppdH) in CH 2 Cl 2 resulted in a mixed-valence Mn 3 II Mn 6 III Mn IV decanuclear cluster of formula [Mn 10 O 7 (dppd) 3 (O 2 CPh) 11 ]· 4CH 2 Cl 2 (1). The structure of the core of 1 is based upon a centred tricapped trigonal prism. Reacting Mn(BF 4 ) 2 ·xH 2 O with dppdH and triethylamine (NEt 3 ) in CH 2 Cl 2 -MeOH gave a rare, homoleptic hexanuclear cluster of formula [Mn II 6 (dppd) 8 ][BF 4 ] 4 (2) which has a triangular based core. Reaction of Mn(Y) 2 ·xH 2 O, Y = NO 3 or BF 4 -, with dppdH or 1-phenyl-3-(2-pyridyl)propane-1,3-dione (pppdH) in the presence of triethanolamine (teaH 3 ) and NEt 3 gave a heptanuclear 'disc' like manganese core of general formula [Mn II 7 (X) 6 (tea)(OH
A new mixed ligand coordination polymer of Mn(II): structural aspect and cryomagnetic study
Structural Chemistry, 2008
A new 1-D polymeric chain complex [Mn(pydc) (1,10-phen)] n Á nH 2 O (pydc = pyridine-2,3-dicarboxylate, 1,10-phen = 1,10-phenanthroline) has been synthesised and characterised by elemental analysis, FT-IR spectrum, thermal analysis and variable temperature magnetic susceptibility studies. Single crystal X-ray diffraction study reveals that the central Mn(II) ion is in a distorted octahedral coordination geometry, and is coordinated to pydc and 1,10-phen. The complex shows interesting hydrogen bond modes involving the dicarboxylates and lattice water molecules. The presence of weak antiferromagnetic coupling with J = -0.72 cm -1 for the complex has been concluded from the cryomagnetic susceptibility studies.
Crystals, 2018
Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII MnIII MnIV(HL)2(H2L)2(H2O)4](NO3)2(H2O) 1 was obtained with the Schiff base (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl)propane-1,3-diol, (H4L), and Mn(NO3)2.4H2O. The coordination reaction was promoted by the deprotonation of the ligand by the soft base triethylamine. The paper’s main contribution is the integration of the experimental and computational studies to explain the interesting magnetic behavior that the mixed valence manganese multimetallic core shows. The results presented herein, which are rarely found for Mn(II), (III) and (IV) complexes, will contribute to the understanding of the magnetic communication generated by the valence electrons and its reper...