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1.
Chemistry ; 29(30): e202203449, 2023 May 26.
Article in English | MEDLINE | ID: mdl-36919766

ABSTRACT

[Mn3 O(OAc)7 (HOAc)]6 ⋅ x AcOH (x=6-9) represents a rare example of a compound containing molecular Mn18 -rings. These are formed by Mn3 (µ3 -O) subunits in which the high-spin Mn(III) centers are bridged by three pairs of acetate anions (AcO- ). An AcOH molecule coordinates to one of the Mn atoms leading to [Mn3 (µ3 -O)(µ2 -OAc)6 (AcOH)]-units, designated in short as Mn3 -units, that are interconnected by acetate anions via the other two Mn atoms to form Mn18 -rings. Magnetic measurements show weak ferromagnetic interactions between them that are suppressed in strong magnetic field. Quantum-chemical calculations on Mn3 model complexes using independently DFT and ab-initio multi reference methods (CASSCF/NEVPT2) show a correlation between the orientation of the pseudo-Jahn-Teller axes of pairs of Mn(III) magnetic centers and corresponding exchange coupling energies. Weak coupling between Mn3 -units within the Mn18 -ring allowed to simulate the magnetic susceptibility versus temperature dependence in terms of basically uncoupled magnetic moments of each Mn3 -unit within the ring.

2.
Inorg Chem ; 60(17): 12651-12663, 2021 Sep 06.
Article in English | MEDLINE | ID: mdl-34431300

ABSTRACT

We obtained single crystals of the binary mixed-valent fluorides Mn2F5 and Mn3F8 using a high-pressure/high-temperature approach. Mn2F5 crystallizes isotypic to CaCrF5 in the monoclinic space group C2/c (No. 15), with a = 8.7078(8) Å, b = 6.1473(6) Å, c = 7.7817(7) Å, ß = 117.41(1)°, V = 369.80(6) Å3, Z = 4, and mC28 at T = 173 K. Mn3F8 crystallizes in the monoclinic space group P21 (No. 4) with a = 5.5253(2) Å, b = 4.8786(2) Å, c = 9.9124(4) Å, ß = 92.608(2)°, V = 266.92(2) Å3, Z = 2, and mP22 at T = 183 K and presents a new structure type. Crystal-chemical reasoning, CHARDI calculations, and quantum-chemical calculations allowed for the assignment of the oxidation states of the Mn atoms. In both bulk compounds, MnF2 was present as an impurity, as evidenced by powder X-ray diffraction and IR and Raman spectroscopy.

3.
Chemistry ; 27(38): 9801-9813, 2021 Jul 07.
Article in English | MEDLINE | ID: mdl-33830547

ABSTRACT

As a consequence of the static Jahn-Teller effect of the 5 E ground state of MnIII in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF6 ]3- anions with two longer and four shorter Mn-F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K3 [MnF6 ] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF6 ]3- anions of quite different nature compared to that met in ideal octahedral MnIII Jahn-Teller systems. Owing to the internal electric field of Ci symmetry dominated by the next-neighbour K+ ions acting on the MnIII sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF6 ]3- anions are present in K3 [MnF6 ]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations.

4.
Chemistry ; 25(68): 15656-15661, 2019 Dec 05.
Article in English | MEDLINE | ID: mdl-31544988

ABSTRACT

The binary lead fluoride Pb3 F8 was synthesized by the reaction of anhydrous HF with Pb3 O4 or by the reaction of BrF3 with PbF2 . The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS 19 F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.

5.
Inorg Chem ; 58(9): 5518-5523, 2019 May 06.
Article in English | MEDLINE | ID: mdl-30896155

ABSTRACT

Li2SiF6:Mn4+ was synthesized via a new HF-free synthesis route by a high-pressure/high-temperature doping experiment at 5.5 GPa and 750 °C. It is proven that the phosphor cannot be synthesized by the common wet-chemical precipitation route in aqueous HF. The sample was characterized by powder X-ray diffraction, EDX, and luminescence spectroscopy. At room temperature, Li2SiF6:Mn4+ exhibits seven emission lines with the strongest line at λmax ≈ 630 nm and a dominant wavelength of λdom ≈ 618 nm. The CIE coordinates are 0.688 and 0.312 for x and y, respectively. The compound shows a luminous efficacy of radiation (LER) of 218 lm Wopt-1, which exceeds the LER of current state-of-the-art red LED phosphor K2SiF6:Mn4+ by 7% due to a blue-shift of the emission. It reveals excellent thermal quenching behavior up to 125 °C.

6.
Chem Commun (Camb) ; 54(12): 1421-1424, 2018 Feb 06.
Article in English | MEDLINE | ID: mdl-29303170

ABSTRACT

The novel binary P4 analogue (Ge2P2)2- proved to be a suitable precursor for heteroatomic cluster synthesis. Over time in solution, it rearranges to form (Ge7P2)2-, as shown by NMR studies and X-ray diffraction. Reactions of (Ge2P2)2- with CdPh2 afford [K(crypt-222)]3[Cd3(Ge3P)3], containing an unprecedented ternary cluster anion with a triangular Cd3 moiety.

7.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 7): 1073-1075, 2017 Jul 01.
Article in English | MEDLINE | ID: mdl-28775886

ABSTRACT

Single crystals of K2Hg(SCN)4 [dipotassium tetra-thio-cyanato-mercurate(II)] were grown from aqueous solutions of potassium thio-cyanate and mercury(II) thio-cyanate and studied by single-crystal X-ray diffraction. In comparison with the previously reported structure model [Zvonkova (1952 ▸). Zh. Fiz. Khim. 26, 1798-1803], all atoms in the crystal structure were located, with lattice parameters and fractional coordinates determined to a much higher precision. In the (crystal) structure, the HgII atom is located on a twofold rotation axis and is coordinated in the form of a distorted tetra-hedron by four S atoms of the thio-cyanate anions. The K+ cation shows a coordination number of eight.

8.
Acta Crystallogr E Crystallogr Commun ; 72(Pt 8): 1211-3, 2016 Aug 01.
Article in English | MEDLINE | ID: mdl-27536416

ABSTRACT

Single crystals of NbF4, niobium(IV) tetra-fluoride, were synthesized by disproportionation of Nb2F5 at 1273 K in a sealed niobium tube, extracted and studied by single-crystal X-ray diffraction. Previous reports on the crystal structure of NbF4 were based on X-ray powder diffraction data and the observed isotypicity to SnF4 [Gortsema & Didchenko (1965 ▸). Inorg. Chem. 4, 182-186; Schäfer et al. (1965 ▸). J. Less Common Met. 9, 95-104]. The data obtained from a single-crystal X-ray diffraction study meant the atomic coordinates could now be refined as well as their anisotropic displacement parameters, leading to a significant improvement of the structural model of NbF4. In the structure, the Nb atom is octahedron-like surrounded by six F atoms of which four are bridging to other NbF6 octa-hedra, leading to a layer structure extending parallel to the ab plane.

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