Tetramer Compound of Manganese Ions with Mixed Valence [MnII MnIII MnIV] and Its Spatial, Electronic, Magnetic, and Theoretical Studies (original) (raw)
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Mixed-valent tetranuclear manganese complexes with an {MnII3MnIV} core
Inorganic Chemistry Communications, 2011
Reaction of pentadentate Schiff-base ligands, 1,3bis(3-methoxysalicylideneamino)-2-propanol (H 3 msap) with manganese(II) salts afforded tetranuclear mixed-valent manganese complexes, [Mn 4 (msap) 2 (CH 3 CO 2) 3 (CH 3 O) (H 2 O)]ÁH 2 O (1) and [Mn 4 (msap) 2 (C 6 H 5 CO 2) 3 (CH 3 O)] (2), which were characterized by elemental analysis, infrared and diffused reflectance spectra and temperature dependence of magnetic susceptibilities (4.5-300 K). Single-crystal X-ray crystallography of these complexes showed that four manganese atoms are chelated by two Schiff-base ligands and further coordinated by syn-syn bridging, syn-anti bridging, and monodentate or bidentate-carboxylato groups, forming a Y-shaped cluster made up of two Mn II and two Mn III atoms. Diffused reflectance spectra are featureless, showing broad bands around at near-UV and visible regions. Magnetic moments decrease with lowering of temperature, showing an antiferromagnetic behavior of these complexes.
Mixed-valent trinuclear manganese complex with N,N'-bis(2-hydroxy-3,5-dimethylbenzyl-N,N'-dimethyl-1,2-ethanediamine (H 2 hdde), [Mn 3 (hdde) 2 (CH 3 CO 2) 2 (CH 3 O) 2 ], was synthesized. The X-ray crystal structure analysis revealed that compound is a trinuclear manganese complex with linearly arrangement of Mn III-Mn II-Mn III , where two manganese ions of each Mn II-Mn III pair are bridged by µ-phenolato-oxygen of hdde 2– ligand, µ-methanolato-oxygen, and µ-acetato ion. Temperature dependence of magnetic susceptibilities showed an increase of magnetic moment as the temperature lowers in the range of 300—6 K and a decrease below 6 K. The magnetic analysis based on Heisenberg model yielded ferromagnetic coupling (J = 2.62 cm –1) between Mn III and Mn II ions.
Dalton Trans., 2006
The reaction between MnBr 2 •4H 2 O with H 3 tmp (1,1,1-tris(hydroxymethyl)propane) in MeCN in the presence of Na(O 2 CCMe 3) and NBu 4 Br produces the complex [Mn 8 (O 2 CCMe 3) 2 (tmp) 2 (Htmp) 4 Br 4-(H 2 O) 2 ]•2MeCN (1•2MeCN) in good yield. The centrosymmetric octanuclear molecule consists of four Mn III and four Mn II ions assembled together by fourteen alkoxo bridges to give a [Mn III 4 Mn II 4 (l 3-OR) 6 (l 2-OR) 8 ] 6+ rod-like core in which the metal centres are arranged in a planar zigzag fashion. Peripheral ligation is provided by a combination of bridging pivalate ions, terminal bromides and water molecules. Dc magnetic susceptibility measurements reveal the presence of dominant antiferromagnetic interactions leading to a spin ground state of S = 0. A rationalization of this result is attempted by structural comparison with previously reported tetranuclear manganese complexes containing the [Mn III 2 Mn II 2 (l 3-OR) 2 (l 2-OR) 4 ] core in which the magnetic interactions are ferromagnetic.
Inorganic Chemistry, 1998
Aerial oxidation of Mn II /ptt 3-(ptt 3-) propane-1,2,3-trithiolate) mixtures gives [Mn 2 (pttd) 2 ] 2-, where pttd 4is the mono(disulfide) of ptt 3-. (NEt 3 Bz) 2 [Mn 2 (pttd) 2 ] (2) crystallizes in space group P2 1 /c with (at -158°C) a ) 11.540(2) Å, b ) 12.115 Å, c ) 17.478(4) Å, ) 101.78(1)°, and Z ) 2. The anion contains a doublybridged [Mn 2 S 8 ] core (Mn‚‚‚Mn ) 3.598(2) Å) with five-coordinate Mn III ions, very similar to previously reported [Mn 2 (edt) 4 ] 2-(anion of 1; edt 2-) ethane-1,2-dithiolate). Aerial oxidation of Mn II /pdt 2-(pdt 2-) propane-1,3dithiolate) mixtures gives [Mn 3 (pdt) 5 ] 2-, which is mixed valent (Mn II , 2Mn III ). (PPh 4 ) 2 [Mn 3 (pdt) 5 ] (3) crystallizes in space group P1 h with (at -161°C) a ) 14.385(6) Å, b ) 23.734(11) Å, and Z ) 2. The anion contains a near-linear Mn III Mn II Mn III unit with five-coordinate Mn III , six-coordinate Mn II , and three thiolate bridges between each Mn 2 pair; Mn‚‚‚Mn separations are 3.123(3) and 3.101(3) Å. Aerial oxidation of Mn II /edt 2-/ImH (ImH ) imidazole) mixtures gives [Mn(edt) 2 (ImH)] -. (NEt 4 )[Mn(edt) 2 (ImH)] (4) crystallizes in space group P2 1 /n with (at -72°C) a ) 13.974(5) Å, b ) 14.317(5) Å, c ) 10.564(3) Å, ) 90.13(2)°, and Z ) 4. The anion is five-coordinate and square-pyramidal. Aerial oxidation of Mn II /edt 2-/Immixtures gave [Mn 2 (Im)(edt) 4 ] 3-, which contains two Mn III ions. (NMe 4 ) 3 [Mn 2 (Im)(edt) 4 ] (5) crystallizes in space group Pna2 1 with (at -160°C) a ) 17.965(5) Å, b ) 16.094(4) Å, c ) 14.789(3) Å, and Z ) 4. The five-coordinate Mn III ions are bridged by the Imgroup across a Mn‚‚‚Mn separation of 6.487(2) Å. The anion of 4 contains high-spin Mn III (S ) 2) and exhibits inter-anion antiferromagnetic exchange interactions (J ) -0.15 cm -1 , g ) 1.91) propagated by interanion NH‚‚‚S hydrogen bonds. Complexes 1-3 and 5 all possess intraanion antiferromagnetic exchange interactions; the fitting parameters are as follows: 1, J ) -19.0 cm -1 , g ) 1.96, D ) -0.22 cm -1 ; 2, J ) -16.4 cm -1 , g ) 1.96, D ) -0.22 cm -1 ; 3, J ) -18.8 cm -1 , g ) 2.00; 5, J ) -1.75 cm -1 , g ) 1.84, D ) -0.028 cm -1 (Ĥ ) -2JS i S j convention). Complexes 1, 2, and 5 have S ) 0 ground states, while that of 3 is S ) 3 / 2 . S0020-1669(97)Supporting Information Available: Textual and tabular summaries of the structure determinations, tables of atomic coordinates, thermal parameters, and bond distances and angles, fully labeled figures for complexes 2-5 and the m Vs T equation for 3 (68 pages). Ordering information is given on any current masthead page. IC970587R Manganese(II) Dithiolate Complexes
Linear trinuclear manganese(II) complexes: crystal structures and magnetic properties
Inorganic Chemistry Communications, 2005
Two new trinuclear manganese(II) complexes, [Mn 3 (O 2 CCH(CH 3) 2) 6 (N-N) 2 ] (N-N is 1,10 0-phenanthroline (1) and 2,2 0-bipyridine (2)) have been prepared and fully characterized. Single crystal X-ray diffraction analysis confirmed a linear arrangement of three Mn(II) centers bridged by six isobutyric carboxylate groups. The magnetic measurements showed that both complexes exhibit an S T = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites: J/k B = À2.31(2) and À2.67(2) K for 1 and 2, respectively.
Inorganic Chemistry, 1997
The reaction of N-n-Bu 4 MnO 4 or NaMnO 4 with appropriate reagents in ethanol-pyridine leads to the high-yield formation of new mixed-valence trinuclear oxo-centered Mn III,III,II complexes of general formulation [Mn 3 O(Xbenzoato) 6 L 3 ] (1, X ) 2-fluoro, L ) pyridine; 2, X ) 2-chloro, L ) pyridine; 3, X ) 2-bromo, L ) pyridine; 4, X ) 3-fluoro, L ) 2 pyridine + 1 H 2 O; 5, X ) 3-chloro, L ) 2 pyridine + 1 H 2 O; 6, X ) 3-bromo, L ) 2 pyridine + 1 H 2 O). The crystal structures of 1, 5, and 6 were determined. Complex 1 crystallizes in the monoclinic system, space group C2/c with a ) 15.774(2) Å, b ) 17.269(2) Å, c ) 21.411(2) Å, ) 91.11(1)°, and Z ) 4. Complex 5 crystallizes in the monoclinic system, space group P2 1 /n with a ) 15.172(2) Å, b ) 17.603(2) Å, c ) 21.996(3) Å, ) 106.300(10), and Z ) 4. Complex 6 crystallizes in the monoclinic system, space group P2 1 /n with a ) 15.533(3) Å, b ) 17.884(2) Å, c ) 21.997(4) Å, ) 106.95(1)°, and Z ) 4. The three complexes are neutral and possess an oxo-centered Mn 3 O unit with peripheral ligands provided by bridging carboxylate and terminal pyridine or H 2 O groups. Each manganese ion is distorted octahedral, and consideration of overall charge necessitates a mixed-valence Mn II Mn III 2 description. In 1, the presence of a C 2 axis through the central O atom and one of the manganese atoms (Mn II ) and the absence of imposed symmetry elements in 5 and 6 (they have the two Mn III with a terminal pyridine group and the Mn II with a H 2 O terminal molecule) suggest a trapped-valence situation in all three cases. The Mn II is assigned on the basis of its longer metal-ligand distances. Variabletemperature magnetic susceptibility studies were performed on 1-6 in the temperature range 2-300 K. Satisfactory fits to the observed susceptibility data were obtained by assuming isotropic magnetic exchange interactions and using the appropriate spin Hamiltonian and susceptibility equation. The derived J and J* exchange parameters are all relatively small in magnitude, |J| < 10 cm -1 . J characterizes the Mn II ‚‚‚Mn III interactions and J* the Mn III ‚‚‚Mn III interaction. Magnetization measurements at 2 K up to 50 kG indicate the variability of the ground state: S ) 3 / 2 for 2 and 3; S ) 1 / 2 for 1, 4, and 5; and S ) 3 / 2 , 1 / 2 for 6. X-band EPR spectra measured from 4 K to room temperature on polycrystalline samples of 1-6 show highly significant differences when the ground state is 3 / 2 or 1 / 2 . For S ) 3 / 2 complexes (2 and 3), there is a transition centered at g ≈ 4, which decreases in intensity with increasing temperature. For S ) 1 / 2 complexes, this g ≈ 4 band does not appear but instead there are broad bands centered at g ≈ 2. These results are discussed in terms of spin frustration within the Mn 3 O core, which produces different spin ground states and susceptibility values. X
Inorganic Chemistry, 2008
Two tetranuclear Mn complexes with an average Mn oxidation state of +2.5 have been prepared. These valence isomers have been characterized by a combination of X-ray crystallography, X-ray absorption spectroscopy, and magnetic susceptibility. The Mn II 3 Mn IV tetramer has the Mn ions arranged in a distorted tetrahedron, with an S ) 6 ground spin state, dominated by ferromagnetic exchange among the manganese ions. The Mn II 2 Mn III 2 tetramer also has a distorted tetrahedral arrangement of Mn ions but shows magnetic behavior, suggesting that it is a single-molecule magnet. The X-ray absorption near-edge structure (XANES) spectra for the two complexes are similar, suggesting that, while Mn XANES has sufficient sensitivity to distinguish between trinuclear valence isomers (Alexiou et al. Inorg. Chem. 2003, 42, 2185, similar distinctions are difficult for tetranuclear complexes such as that found in the photosynthetic oxygen-evolving complex.
CrystEngComm, 2013
The reactions of [Mn III (L4a)Cl] or [Mn III (L4b)Cl] with [Pt(SCN) 6 ] 22 resulted in the formation of a 1D polymeric complex [{Mn(L4a)} 2 {m-Pt(SCN) 6 }] n (1) and a trinuclear compound [{Mn(L4b)(H 2 O)} 2 {m-Pt(SCN) 6 }] (2), where L4a and L4b are tetradentate dianionic Schiff base ligands, H 2 L4a = N,N9-ethylenebis(salicylimine) and H 2 L4b = N,N9-3-methylbenzenebis(3-ethoxysalicylimine). In compound 1, the adjacent [Mn(L4a)] + subunits are bound together through the phenolic oxygen atoms, thus forming [{Mn(L4a)} 2 ] 2+ dimers with the shortest Mn … Mn distance of 3.2101(5) Å, while in compound 2, the intermolecular bifurcated O-H … O hydrogen bonds between the neighbouring molecules form [{Mn(L4b)(H 2 O)} 2 ] 2+ dimers, resulting in a supramolecular 1D chain structure. The Mn … Mn distance within the supramolecular dimer is 4.7007(9) Å, while the shortest Mn … Mn distance between the dimers is 9.2347(10) Å. The magnetic analyses comprising the zero-field splitting resulted in a ferromagnetic exchange interaction within the phenolato-bridged dimer in 1 (J = +1.73 cm 21 , D Mn = 22.65 cm 21 ) and the antiferromagnetic exchange interaction within the supramolecular dimer in 2 (J = 20.88 cm 21 , D Mn = 23.06 cm 21 ). The experimental findings regarding the dominant as well as negligible exchange pathways are in good agreement with the results from DFT calculations at the B3LYP/TZVP level of theory. 634 954; Tel: +420 585 634 352 3 Electronic supplementary information (ESI) available: Fig. S1 (the correlation between the ferromagnetic exchange, J, and Mn-O* distance), Fig. S2 (modelling of the effect of ZFS on the magnetic properties of the dimer), Fig. S3 (the calculated spin density distribution using B3LYP/TZVP for [{Mn(L4b)(H 2 O)} 2 {m-Pt(SCN) 6 }] (2)) and Table S1 (the DFT calculated net Mulliken spin densities (r), the expectation values ,S 2 . and exchange energy (J) from the HS and BS states of the [{Mn(L4a)NCS} 2 ] and [{Mn(L4b)(H 2 O)(NCS)} 2 ] moieties extracted from the X-ray structures of 1 and 2, respectively), (the DFT calculated net Mulliken spin densities (r), the expectation values ,S 2 . and exchange energy (J) from the HS and BS states of [{Mn(L4b)(H 2 O)} 2 {m-Pt(SCN) 6 }] (2) based on a geometry from the X-ray structural determination). CCDC 930629 and 930630. For ESI and crystallographic data in CIF or other electronic format see
CrystEngComm, 2014
The reaction of M(ox)‚2H 2 O (M ) Co(II), Ni(II)) or K 2 (Cu(ox) 2 )‚2H 2 O (ox ) oxalate dianion) with n-ampy (n ) 2, 3, 4; n-ampy ) n-aminopyridine) and potassium oxalate monohydrate yields one-dimensional oxalatobridged metal(II) complexes which have been characterized by FT-IR spectroscopy, variable-temperature magnetic measurements, and X-ray diffraction methods. The complexes M(µ-ox)(2-ampy) 2 (M ) Co (1), Ni (2), Cu ) are isomorphous and crystallize in the monoclinic space group C2/c (No. 15), Z ) 4, with unit cell parameters for 1 of a ) 13.885(2) Å, b ) 11.010(2) Å, c ) 8.755(1) Å, and ) 94.21 , Ni (5), Cu ) are also isomorphous and crystallize in the orthorhombic space group Pcnn (No. 52), Z ) 8, with unit cell parameters for 6 of a ) 12.387 , b ) 12.935(3), and c ) 18.632(2) Å. Compound Co(µ-ox)(4-ampy) 2 (7) crystallizes in the space group C2/c (No. 15), Z ) 4, with unit cell parameters of a ) 16.478(3) Å, b ) 5.484(1) Å, c ) 16.592(2) Å, and ) 117.76(1)°. Complexes M(µ-ox)(4-ampy) 2 (M ) Ni (8), Cu (9)) crystallize in the orthorhombic space group Fddd (No. 70), Z ) 8, with unit cell parameters for 8 of a ) 5.342(1), b ) 17.078 , and c ) 29.469(4) Å. All compounds are comprised of one-dimensional chains in which M(n-ampy) 2 2+ units are sequentially bridged by bis-bidentate oxalato ligands with M‚‚‚M intrachain distances in the range of 5.34-5.66 Å. In all cases, the metal atoms are six-coordinated to four oxygen atoms, belonging to two bridging oxalato ligands, and the endo-cyclic nitrogen atoms, from two n-ampy ligands, building distorted octahedral surroundings. The aromatic bases are bound to the metal atom in cis (1-6) or trans (7-9) positions. Magnetic susceptibility measurements in the temperature range of 2-300 K show the occurrence of antiferromagnetic intrachain interactions except for the compound 3 in which a weak ferromagnetic coupling is observed. Compound 7 shows spontaneous magnetization below 8 K, which corresponds to the presence of spin canted antiferromagnetism.