Cyano-Bridged Dy(III) and Ho(III) Complexes with Square-Wave Structure of the Chains

Four new cyano-bridged DyIII-CrIII, DyIII-FeIII, HoIII-CrIII and HoIII-FeIII bimetallic coordination polymers were synthesized by the reaction of [Ln(H2dapsc)(H2O)4](NO3)3 (Ln = Dy, Ho); H2dapsc = 2,6-diacetylpyridinebis(semicarbazone)) with K3[M(CN)6] (M = Cr, Fe) in H2O, resulting in the substitution of two water molecules in the coordination sphere of rare earth by paramagnetic tricharged hexacyanides of Fe and Cr. The complexes are isostructural and consist of alternating [Ln(H2dapsc)(H2O)2]3+ and [M(CN)6]3− units linked by bridges of two cis-cyano ligands of the anion to form square-wave chains. The ac magnetic measurements revealed that the DyCr and DyFe complexes are field-induced single molecule magnets, while their Ho analogs do not exhibit slow magnetic relaxation

A Series of Field-Induced Single-Ion Magnets Based on the Seven-Coordinate Co(II) Complexes with the Pentadentate (N3O2) H2dapsc Ligand

A series of five new mononuclear pentagonal bipyramidal Co(II) complexes with the equatorial 2,6-diacetylpyridine bis(semicarbazone) ligand (H2dapsc) and various axial pseudohalide ligands (SCN, SeCN, N(CN)2, C(CN)3, and N3) was prepared and structurally characterizated: [Co(H2dapsc)(SCN)2]∙0.5C2H5OH (1), [Co(H2dapsc)(SeCN)2]∙0.5C2H5OH (2), [Co(H2dapsc)(N(CN)2)2]∙2H2O (3), [Co(H2dapsc)(C(CN)3)(H2O)](NO3)∙1.16H2O (4), and {[Co(H2dapsc)(H2O)(N3)][Co(H2dapsc)(N3)2]}N3∙4H2O (5). The combined analyses of the experimental DC and AC magnetic data of the complexes (1–5) and two other earlier described those of this family [Co(H2dapsc)(H2O)2)](NO3)2∙2H2O (6) and [Co(H2dapsc)(Cl)(H2O)]Cl∙2H2O (7), their theoretical description and the ab initio CASSCF/NEVPT2 calculations reveal large easy-plane magnetic anisotropies for all complexes (D = + 35 − 40 cm−1). All complexes under consideration demonstrate slow magnetic relaxation with dominant Raman and direct spin–phonon processes at static magnetic field and so they belong to the class of field-induced single-ion magnets (SIMs)

The first photochromic bimetallic assemblies based on Mn(III) and Mn(II) Schiff-base (salpn, dapsc) complexes and pentacyanonitrosylferrate

International audienceFour cyano-bridged bimetallic complexes, \[Mn(salpn)](2)[Fe(CN)(5)NO]\(n) (1), \[Mn(salpn)(CH3OH)](4)[Mn(CN)(5)NO]\[C(CN)(3)]center dot 3H(2)O (2), \[Mn(dapsc)][Fe(CN)(5)NO]center dot 0.5CH(3)OH center dot 0.25H(2)O\(n) (3) and \[Mn(salpn)(CH3OH)](4)[Fe(CN)(5)NO]\(ClO4)(2)center dot 4H(2)O (4), where salpn(2-) = N, N'-1,3-propylene-bis(salicylideneiminato) dianion and dapsc = 2,6-diacetylpyridine-bis(semicarbazone), have been synthesized and structurally characterized by single crystal X-ray diffraction. In 1, the nitroprusside anion [Fe(CN)(5)NO](2-) coordinates with four [Mn(salpn)](+) via four co-planar CN- groups, whereas each [Mn(salpn)](+) links two [Fe(CN)(5)NO](2-) ions, which results in a two-dimensional network. The structure of 3 contains two independent neutral infinite chains \[Mn(dapsc)][Fe(CN)(5)(NO)]\(infinity) consisting of alternating cationic [Mn-II(dapsc)](2+) and anionic [Fe-II(CN)(5)(NO)](2-) units connected through cyanide bridges. The cation complexes 2 and 4 have a pentanuclear molecular structure in which four [Mn(salpn)(MeOH)](+) fragments are linked by the [Mn(CN)(5)NO](3-) or [Fe(CN)(5)(NO)](2-) moieties, respectively. The magnetic and photochromic properties of 1 and 3 have been studied. The thermal magnetic behaviour of the complexes indicates the presence of weak antiferromagnetic interactions between Mn3+ or Mn2+ mediated by diamagnetic [Fe(CN)(NO)-N-5](2-) bridges. Irradiation of 1 and 3 with light gives birth to the long-lived metastable states of nitroprusside

Synthesis, Structure, and Magnetic Properties of 1D {[Mn^III(CN)₆][Mn^II(dapsc)]}_<i>n</i> Coordination Polymers: Origin of Unconventional Single-Chain Magnet Behavior

Two one-dimensional cyano-bridged coordination polymers, namely, {[Mn^II(dapsc)]­[Mn^III(CN)₆]­[K­(H₂O)_2.75(MeOH)_0.5]}_<i>n</i>·0.5<i>n</i>(H₂O) (<b>I</b>) and {[Mn^II(dapsc)]­[Mn^III(CN)₆]­[K­(H₂O)₂(MeOH)₂]}_<i>n</i> (<b>II</b>), based on alternating high-spin Mn^II(dapsc) (dapsc = 2,6-diacetylpyridine bis­(semicarbazone)) complexes and low-spin orbitally degenerate hexacyanomanganate­(III) complexes were synthesized and characterized structurally and magnetically. Static and dynamic magnetic measurements reveal a single-chain magnet (SCM) behavior of <b>I</b> with an energy barrier of <i>U</i>_eff ≈ 40 K. Magnetic properties of <b>I</b> are analyzed in detail in terms of a microscopic theory. It is shown that compound <b>I</b> refers to a peculiar case of SCM that does not fall into the usual Ising and Heisenberg limits due to unconventional character of the Mn^III–CN–Mn^II spin coupling resulting from a nonmagnetic singlet ground state of orbitally degenerate complexes [Mn^III(CN)₆]^3–. The prospects of [Mn^III(CN)₆]^3– complex as magnetically anisotropic molecular building block for engineering molecular magnets are critically analyzed