Two novel coordination compounds containing heterocyclic bidentate N,N-donor ligand 2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (fpo) were synthesized. A general formula for compounds originating from perchlorates of iron, cobalt, and fpo can be written as: [M(fpo)2(H2O)2](ClO4)2 (M = Fe(II) for (1) Co(II) for (2)). The characterization of compounds was performed by general physico-chemical methods-elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) in case of organics, and single crystal X-ray diffraction (sXRD). Moreover, magneto-chemical properties were studied employing measurements in static field (DC) for 1 and X-band EPR (Electron paramagnetic resonance), direct current (DC), and alternating current (AC) magnetic measurements in case of 2. The analysis of DC magnetic properties revealed a high spin arrangement in 1, significant rhombicity for both complexes, and large magnetic anisotropy in 2 (D = -21.2 cm-1). Moreover, 2 showed field-induced slow relaxation of the magnetization (Ueff = 65.3 K). EPR spectroscopy and ab initio calculations (CASSCF/NEVPT2) confirmed the presence of easy axis anisotropy and the importance of the second coordination sphere.

• Klíčová slova
• 1,3,4-oxadiazole, second coordination sphere, single-molecule magnet,
• MeSH
• anizotropie MeSH
• elektronová paramagnetická rezonance MeSH
• furany chemie   MeSH
• kobalt chemie   MeSH
• komplexní sloučeniny chemie   MeSH
• krystalografie rentgenová MeSH
• magnetická rezonanční spektroskopie MeSH
• molekulární modely MeSH
• oxadiazoly chemie   MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• spektroskopie Mossbauerova MeSH
• železnaté sloučeniny chemie   MeSH
• železo chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 1,3,4-oxadiazole MeSH Prohlížeč
• furan MeSH Prohlížeč
• furany MeSH
• kobalt MeSH
• komplexní sloučeniny MeSH
• oxadiazoly MeSH
• železnaté sloučeniny MeSH
• železo MeSH

Crystal structures and magnetic properties of polymeric and trinuclear heterobimetallic MnIII···PtII···MnIII coordination compounds, prepared from the Ba[Pt(CN)₄] and [Mn(L4A/B)(Cl)] (1a/b) precursor complexes, are reported. The polymeric complex [{Mn(L4A)}₂{μ⁴-Pt(CN)₄}]n (2a), where H₂L4A = N,N'-ethylene-bis(salicylideneiminate), comprises the {Mn(L4A)} moieties covalently connected through the [Pt(CN)₄]2- bridges, thus forming a square-grid polymeric structure with the hexacoordinate MnIII atoms. The trinuclear complex [{Mn(L4B)}₂{μ-Pt(CN)₄}] (2b), where H₂L4B = N,N'-benzene-bis(4-aminodiethylene-salicylideneiminate), consists of two [{Mn(L4B)} moieties, involving pentacoordinate MnIII atoms, bridged through the tetracyanidoplatinate (II) bridges to which they are coordinated in a trans fashion. Both complexes possess uniaxial type of magnetic anisotropy, with D (the axial parameter of zero-field splitting) = -3.7(1) in 2a and -2.2(1) cm-1 in 2b. Furthermore, the parameters of magnetic anisotropy 2a and 2b were also thoroughly studied by theoretical complete active space self-consistent field (CASSCF) methods, which revealed that the former is much more sensitive to the ligand field strength of the axial ligands.

• Klíčová slova
• crystal structures, magnetic anisotropy, manganese(III), platinum(II), zero-field splitting,
• MeSH
• komplexní sloučeniny chemie   MeSH
• krystalografie rentgenová MeSH
• ligandy MeSH
• magnetismus MeSH
• mangan chemie   MeSH
• molekulární struktura MeSH
• Schiffovy báze chemie   MeSH
• sloučeniny platiny chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• komplexní sloučeniny MeSH
• ligandy MeSH
• mangan MeSH
• Schiffovy báze MeSH
• sloučeniny platiny MeSH

Single-molecule magnets display magnetic bistability of molecular origin, which may one day be exploited in magnetic data storage devices. Recently it was realised that increasing the magnetic moment of polynuclear molecules does not automatically lead to a substantial increase in magnetic bistability. Attention has thus increasingly focussed on ions with large magnetic anisotropies, especially lanthanides. In spite of large effective energy barriers towards relaxation of the magnetic moment, this has so far not led to a big increase in magnetic bistability. Here we present a comprehensive study of a mononuclear, tetrahedrally coordinated cobalt(II) single-molecule magnet, which has a very high effective energy barrier and displays pronounced magnetic bistability. The combined experimental-theoretical approach enables an in-depth understanding of the origin of these favourable properties, which are shown to arise from a strong ligand field in combination with axial distortion. Our findings allow formulation of clear design principles for improved materials.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The novel field-induced single-molecule magnet based on a tetracoordinate mononuclear heteroleptic Co(II) complex involving two heterocyclic benzimidazole (bzi) and two thiocyanido ligands, [Co(bzi)2(NSC)2], (CoL4), was prepared and thoroughly characterized. The analysis of AC susceptibility data resulted in the spin reversal energy barrier U = 14.7 cm(-1), which is in good agreement with theoretical prediction, U(theor). = 20.2 cm(-1), based on axial zero-field splitting parameter D = -10.1 cm(-1) fitted from DC magnetic data. Furthermore, mutual interactions between CoL4 and ferromagnetic barium ferrite BaFe12O19 (BaFeO) in hybrid materials resulted in suppressing of slow relaxation of magnetization in CoL4 for 1:2, 1:1 and 2:1 mass ratios of CoL4 and BaFeO despite the lack of strong magnetic interactions between two magnetic phases.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH