Magnetic aspects and assemblies of solvent-mediated layered manganese dicarboxylate based coordination polymers (original) (raw)
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One dimensional assembly of Mn6 single molecule magnets linked by oligothiophene bridges
Dalton Transactions, 2010
A new 1D coordination polymer comprised of [Mn III 6 O 2 (Et-sao) 6 (EtOH) 4 (H 2 O) 2 ] 2+ units and bithiophene dicarboxylato was synthesized by mixing EtsaoH 2 (salicylaldoxime), H 2 btda (2,2¢-bithiophene-5,5¢-dicarboxylic acid) and Mn(ClO 4 ) 2 ·6H 2 O in the presence of NEt 4 OH. The crystal structure was determined and consists of Mn 6 clusters bridged by the bithiophene dicarboxylato ligands coordinated to two of the Mn III ions of the Mn 6 polynuclear complex. Direct current magnetic measurements show an overall ferromagnetic interaction between the Mn III ions within the Mn 6 cluster leading to an S = 12 ground state for the Mn 6 unit. Furthermore, this compound presents single-molecule magnet behaviour. Slow relaxation of the magnetization is observed at low temperature following a thermal activated regime with U eff ª 50 K and t 0 ª 2.2 10 -10 s. The magnetic measurements do not show any noticeable interaction between the Mn 6 clusters through the bithiophene dicarboxylato bridges. † Electronic supplementary information (ESI) available: Crystallographic data including tables with selected bond lengths and angles. CCDC reference number 759086. For ESI and crystallographic data in CIF or other electronic format see
Inorganic Chemistry, 2002
The reactions of the Mn III 3 and Mn II Mn III 2 complexes [Mn 3 O(O 2 CEt) 6 (py) 3 ][ClO 4 ] and [Mn 3 O(O 2 CEt) 6 (py) 3 ] with pyridine-2,6-dimethanol (pdmH 2) afford the mixed-valence Mn II 6 Mn III 2 octanuclear complex [Mn 8 O 2 (py) 4 (O 2 CEt) 8 (L) 2 ][ClO 4 ] 2 (1) and the Mn II 7 Mn III 2 enneanuclear complex [Mn 9 (O 2 CEt) 12 (pdm)(pdmH) 2 (L) 2 ] (2), respectively. Both compounds contain a novel pentadentate ligand, the dianion of (6-hydroxymethylpyridin-2-yl)-(6-hydroxymethylpyridin-2-ylmethoxy)methanol (LH 2), which is the hemiacetal formed in situ from the Mn-assisted oxidation of pdmH 2. Complex 1 crystallizes in the monoclinic space group P2 1 /n with the following cell parameters at −160°C: a) 16.6942(5) Å, b) 13.8473(4) Å, c) 20.0766(6) Å,) 99.880(1)°, V) 4572.27 Å 3 , and Z) 2, R (R w)) 4.78 (5.25). Complex 2‚0.2MeCN crystallizes in the triclinic space group P1 h with the following cell parameters at −157°C: a) 12.1312(4) Å, b) 18.8481(6) Å, c) 23.2600(7) Å, R) 78.6887(8)°,) 77.9596(8)°, γ) 82.3176(8)°, V) 5076.45 Å 3 , and Z) 2, R (R w)) 4.12 (4.03). Both complexes are new structural types comprising distorted-cubane units linked together, albeit in two very different ways. In addition, complex 2 features three distinct binding modes for the chelating ligands derived from deprotonated pdmH 2. Complexes 1 and 2 were characterized by variabletemperature ac and dc magnetic susceptibility measurements and found to possess spin ground states of 0 and 11/2, respectively. Least-squares fitting of the reduced magnetization data gave S) 11/2, g) 2.0, and D) −0.11 cm-1 for complex 2, where D is the axial zero-field splitting parameter. Direct current magnetization versus field studies on 2 at <1 K show hysteresis behavior at <0.3 K, establishing 2 as a new single-molecule magnet. Magnetization decay measurements gave an effective barrier to magnetization relaxation of U eff) 3.1 cm-1) 4.5 K.
Molecular Wheels: New Mn 12 Complexes as Single-Molecule Magnets
Inorganic Chemistry, 2008
The preparation, structure and magnetic properties of three new wheel-shaped dodecanuclear manganese complexes, [Mn 12 (Adea) 8 (CH 3 COO) 14 ] · 7CH 3 CN (1 · 7CH 3 CN), [Mn 12 (Edea) 8 (CH 3 CH 2 COO) 14 ] (2) and [Mn 12 (Edea) 8 (CH 3 COO) 2 -(CH 3 CH 2 COO) 12 ] (3), are reported, where Adea 2and Edea 2are dianions of the N-allyl diethanolamine and the N-ethyl diethanolamine ligands, respectively. Each complex has six Mn(II) and six Mn(III) ions alternating in a wheel-shaped topology, with eight n-substituted diethanolamine dianions. All variable-temperature direct current (DC) magnetic susceptibility data were collected in 1, 0.1, or 0.01 T fields and in the 1.8-300 K temperature range. Heat capacity data, collected in applied fields of 0-9 T and in the 1.8-100 K temperature range, indicate the absence of a phase-transition due to long-range magnetic ordering for 1 and 3. Variable-temperature, variablefield DC magnetic susceptibility data were obtained in the 1.8-10 K and 0.1-5 T ranges. All complexes show out-of-phase signals in the AC susceptibility measurements, collected in a 50-997 Hz frequency range and in a 1.8-4.6 K temperature range. Extrapolation to 0 K of the in-phase AC susceptibility data collected at 50 Hz indicates an S ) 7 ground state for 1, 2, and 3. Magnetization hysteresis data were collected on a single crystal of 1 in the 0.27-0.9 K range and on single crystals of 2 and 3 in the 0.1-0.9 K temperature range. Discrete steps in the magnetization curves associated with resonant quantum tunneling of magnetization (QTM) confirm these complexes to be single-molecule magnets. The appearance of extra QTM resonances on the magnetic hysteresis of 1 is a result of a weak coupling between two Mn ions at opposite ends of the wheel, dividing the molecule into two ferromagnetic exchange-coupled S ) 7 / 2 halves. The absence of these features on 2 and 3, which behave as rigid spin S ) 7 units, is a consequence of different interatomic distances.
The Exploitation of Versatile Building Blocks for the Self-Assembly of Novel Molecular Magnets
Journal of Solid State Chemistry, 2001
Using molecular building blocks to self-assemble lattices supporting long-range magnetic order is currently an active area of solid-state chemistry. Consequently, it is the realm of supramolecular chemistry that synthetic chemists are turning to in order to develop techniques for the synthesis of structurally well-de5ned supramolecular materials. In recent years we have investigated the versatility and usefulness of two classes of molecular building blocks, namely, tris-oxalato transition-metal (M. Pilkington and S. Decurtins, in 99Magnetoscience=From Molecules to Materials,:: Wiley+VCH, 2000), and octacyanometalate complexes (Pilkington and Decurtins, Chimia 54, 593 ), for applications in the 5eld of molecule-based magnets. Anionic, tris-chelated oxalato building blocks are able to build up two-dimensional honeycomb-layered structural motifs as well as three-dimensional decagon frameworks. The discrimination between the crystallization of the two-or threedimensional structures relies on the choice of the templating counterions (Decurtins, Chimia 52, 539 (1998); Decurtins et al. Mol. Cryst. Liq. Cryst. 273, 167 (1995); New J. Chem. 117 (1998)). These structural types display a range of ferro, ferri, and antiferromagnetic properties (Pilkington and Decurtins, in 99Magnetoscience=From Molecules to Materials::). Octacyanometalate building blocks self-assemble to a4ord two new classes of cyano-bridged compounds namely, molecular clusters and extended three dimensional networks (J. Larionova et al., Angew. Chem. Int. Ed. 39, 1605 (2000); Pilkington et al., in preparation). The molecular cluster with a Mn II 9 Mo V 6 core has the highest ground state spin value, S ؍ 51/2, reported to-date (Larionova et al., Angew. Chem. Int. Ed. 39, 1605 (2000)). In the high-temperature regime, the magnetic properties are characterized by ferromagnetic intracluster coupling. In the magnetic range below 44 K, the magnetic cluster signature is lost as possibly a bulk behavior starts to emerge. The three-dimensional networks exhibit both paramagnetic and ferromagnetic behavior, since the magnetic properties of these materials directly re6ect the electronic con5guration of the metal ion incorporated into the octacyanometalate building blocks (Pilkington et al., in preparation). For both the oxalate-and cyanide-bridged materials, we are able to manipulate the magnetic properties of the supramolecular assemblies by tuning the electronic con5gurations of the metal ions incorporated into the appropriate molecular building blocks (Pilkington and Decurtins, in 99Magnetoscience=From Molecules to Materials,:: Chimia 54, 593 ).
A Family of 3D Coordination Polymers Composed of Mn19 Magnetic Units
Angewandte Chemie-international Edition, 2006
The current intense interest in polynuclear clusters stems not only from their aesthetically pleasing structures, magnetic interactions, and magnetostructural correlations, but also from the discovery that some function as nanoscale magnetic particles, or single-molecule magnets (SMMs). [1] Below their blocking temperature (T B ), such molecules behave as magnets and exhibit hysteresis in scans of magnetization versus dc field. This behavior results from the combination of a large ground spin state (S) with a large and negative (easy-axis type) magnetoanisotropy. SMMs have several potential applications, including high-density information storage, in which each bit of information is stored as the magnetization orientation of an individual molecule, and quantum computation, in which the molecules can serve as qubits.
Dalton Transactions, 2012
Salicylamidoxime was used to synthesize 13 new polynuclear Mn III complexes. We present the crystallographic structures, the magnetic susceptibility and the magnetization measurements of eight of them (1-8) with the general formula [Mn 6 O 2 (H 2 N-sao) 6 (L) 2 (solvent) 4-6 ] (L = carboxylate, chloride, 2-cyanophenolate; solvent = H 2 O, MeOH, EtOH, py). These complexes consist of two trinuclear {Mn III 3 (μ 3 -O)(H 2 N-sao) 3 } + cationic units linked together via two oximate and two phenolate oxygen atoms. All behave as single-molecule magnets, with the spin ground state varying from 4 to 12 and anisotropy energy barriers from 24 to 86 K, the latter being as high as the present record barrier in the Mn 6 complexes. DFT calculations were performed to compute the exchange magnetic coupling constants J between the metallic ions and to provide an orbital interpretation of exchange. Our results are in line with previously reported results with the parent salicylaldoxime derivatives. The Mn-N-O-Mn torsion angle appears as the main parameter controlling the J values. The critical angle where the exchange coupling between two Mn III switches from antiferromagnetic to ferromagnetic is 27°, less than the one found in related complexes with salicylaldoxime (30°). We propose a structural classification of the {Mn 6 } complexes in four classes depending on the coordination of the axial carboxylate. The work points out the structural flexibility of such systems, their sensitivity to solvent effects and their ability to achieve high anisotropy energy barriers by simple desolvation. † Electronic supplementary information (ESI) available: Crystal data on compounds 9-13 , dc and ac magnetic susceptibility, magnetization as a function of H and H/T, Arrhenius plot of the relaxation processes for compounds
Acta Crystallographica Section C Structural Chemistry, 2014
The title complex, catena-poly[di-μ3-acetato-κ(6)O:O:O&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-tetra-μ2-acetato-κ(4)O:O;κ(4)O:O&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-diaquabis(pyridine-κN)trimanganese(II)], [Mn3(CH3COO)6(C6H5N)2(H2O)2]n, is a true one-dimensional coordination polymer, in which the Mn(II) centres form a zigzag chain along [010]. The asymmetric unit contains two metal centres, one of which (Mn1) lies on an inversion centre, while the other (Mn2) is placed close to an inversion centre on a general position. Since all the acetates behave as bridging ligands, although with different μ2- and μ3-coordination modes, a one-dimensional polymeric structure is formed, based on trinuclear repeat units (Mn1...Mn2...Mn2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;), in which the Mn2 and Mn2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; sites are related by an inversion centre. Within this monomeric block, the metal-metal separations are Mn1...Mn2 = 3.36180 (18) Å and Mn2...Mn2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; = 4.4804 (3) Å. Cation Mn1, located on an inversion centre, displays an [MnO6] coordination sphere, while Mn2, on a general position, has a slightly stronger [MnO5N] ligand field, as the sixth coordination site is occupied by a pyridine molecule. Both centres approximate an octahedral ligand field. The chains are parallel in the crystal structure and interact via hydrogen bonds involving coordinated water molecules. However, the shortest metal-metal separation between two chains [5.3752 (3) Å] is large compared with the intrachain interactions. These structural features are compatible with a single-chain magnet behaviour, as confirmed by preliminary magnetic studies.
Inorganic Chemistry, 2001
3 ] (6) have been obtained from the 1:1 reaction of the corresponding homocarboxylate species. Complex 5‚CH 2 Cl 2 ‚H 2 O crystallizes in the triclinic space group P1 h with, at -165°C, a ) 15.762(1), b ) 16.246-(1), c ) 23.822(1) Å, R ) 103.92(1), ) 104.50(1), γ ) 94.23(1)°, Z ) 2, and V ) 5674(2) Å 3 . Complex 6‚CH 2 Cl 2 crystallizes in the triclinic space group P1 h with, at -158°C, a ) 13.4635(3), b ) 13.5162(3), c ) 23.2609(5) Å, R ) 84.9796(6), ) 89.0063(8), γ ) 86.2375(6)°, Z ) 2, and V ) 4207.3(3) Å 3 . Complexes 5 and 6 both contain a [Mn 12 O 12 ] core with the CHCl 2 CO 2ligands ordered in the axial positions and the RCO 2ligands (R ) CH 2 Bu t (5) or Et ) in equatorial positions. There is, thus, a preference for the CHCl 2 CO 2to occupy the sites lying on the Mn III Jahn-Teller axes, and this is rationalized on the basis of the relative basicities of the carboxylate groups. Direct current magnetic susceptibility studies in a 10.0 kG field in the 2.00-300 K range indicate a large ground-state spin, and fitting of magnetization data collected in the 10.0-70.0 kG field and 1.80-4.00 K temperature range gave S ) 10, g ) 1.89, and D ) -0.65 K for 5, and S ) 10, g ) 1.83, and D ) -0.60 K for 6. These values are typical of [Mn 12 O 12 (O 2 CR) 16 (H 2 O) 4 ] complexes. Alternating current susceptibility studies show the out-of-phase susceptibility ( M ′′) signals characteristic of the slow relaxation in the millisecond time scale of single-molecule magnets. Arrhenius plots obtained from M ′′ versus T data gave effective barriers to relaxation (U eff ) of 71 and 72 K for 5 and 6, respectively. 1 H NMR spectra in CD 2 Cl 2 show that 5 and 6 are the main species present on dissolution, but there is evidence for some ligand distribution between axial and equatorial sites, by intra-and/or intermolecular exchange processes. (6) (a) Aubin, S. M. J.; Sun, Z.; Guzei, I. A.; Rheingold, A. L.; Christou, G.; Hendrickson, D. N. Chem. Commun. 1997, 2239. (b) Sun, Z.; Ruiz, D.; Rumberger, E.; Incarvito, C. D.; Folting, K.; Rheingold, A. L.; Christou, G.; Hendrickson, D. N. Inorg. Chem. 1998, 37, 4758. (7) (a) Brechin, E. K.; Yoo, J.; Nakano, M.; Huffman, J. C.; Hendrickson, D. N.; Christou, G. Chem. Commun. 1999, 783. (b) Yoo, J.; Brechin, E. K.; Yamaguchi, A.; Nakano, M.; Huffman, J. C.; Maniero, A. L.; Brunel, L.-C.; Awaga, K.; Ishimoto, H.; Christou, G.; Hendrickson, D. N. Caneschi, A.; Cornia, A.; Fabrizi de Biani, F.; Gatteschi, D.; Sangregorio, C.; Sessoli, R.; Sorace, L.
Dalton Transactions, 2012
Two new coordination polymers have been synthesized with Mn 2+ and Dy 3+ ions using a new bent etherbridged tricarboxylic acid ligand, o-cpiaH 3 (5-(2-carboxy-phenoxy)-isophthalic acid). The ligand readily reacts with a Mn 2+ salt in presence of pyridine ( py) under hydrothermal condition to afford a 3D coordination polymer {[Mn 9 (o-cpia) 6 ( py) 3 (3H 2 O)]·H 2 O} n (1), that contains two types of polymeric chains. One of them is merely carboxylate bridged Mn 2+ where each metal ion shows both penta-and hexa-coordination. The other chain consists of carboxylate-bridging along with terminally bound pyridines providing both penta-and hexa-coordination to each metal ion. When o-cpiaH 3 is treated with Dy(NO 3 ) 3 .xH 2 O under solvothermal condition, it gives rise to an unusual double layer (6,6) connected 2D coordination polymer {[Dy(o-cpia)]} n (2), where each metal ion is hexacoordinated. The double layer 2D sheets are stacked to each other in AA⋯ fashion through strong C-H⋯π interactions to generate an overall 3D supramolecular architecture. Both the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Variable temperature magnetic susceptibility measurements indicate that 1 exhibits metamagnetic behavior while 2 shows weak antiferromagnetic behavior. † Electronic supplementary information (ESI) available: selected bonds and distances for 1 and 2, figures, IR, TGA analysis, ESI-MS, and NMR. CCDC reference numbers 841423 and 841424. For ESI and crystallographic data in CIF or other electronic format see