03 Fakultät Chemie
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Item Open Access An anionic mesoionic carbene (anMIC) and its transformation to metallo MIC‐boranes : synthesis and properties(2025) Rudolf, Richard; Todorovski, Andrej; Lederer, Vera; Neuman, Nicolás I.; Schubert, Hartmut; Sarkar, BiprajitNeutral mesoionic carbenes (MICs) based on a 1,2,3‐triazole core have had a strong impact on various branches of chemistry such as homogeneous catalysis, electrocatalysis, and photochemistry/photophysics. We present here the first general synthesis of anionic mesoionic carbenes (anMICs, 2) based on a 1,2,3‐triazole core and a borate backbone. The free anMIC is stable in solution under an inert atmosphere at low temperatures, and can be stored for several weeks. Analysis of donor properties shows that these anMICs are extremely strong σ‐donors, bypassing the donor properties of strong donors such as MICs, NHCs, anionic NHCs and N‐heterocyclic olefins. The room temperature conversion of the free anMICs leads to three equally interesting compound classes: an amide‐coordinated borane based on a MIC‐borane backbone (2BR3), a polymeric triazolide (1Li) and an amide‐coordinated metallo‐MIC‐borane. The metallo‐MIC‐borane (3Li) is an interesting precursor for the synthesis of further amide‐coordinated MIC‐borane compounds. Quantum chemical calculations have been used to elucidate the mechanism of transformation of the anMICs. We thus introduce three new categories of mesoionic compounds here with potential for different branches of chemistry and beyond.Item Open Access Synthesis, crystal structure and properties of the new laminar quaternary tellurides SrLnCuTe3 (Ln = Sm, Gd-Tm and Lu)(2023) Ruseikina, Anna V.; Grigoriev, Maxim V.; Molokeev, Maxim S.; Garmonov, Alexander A.; Elyshev, Andrey V.; Locke, Ralf J. C.; Schleid, ThomasThis paper reports for the first time on the new laminar quaternary orthorhombic heterometallic quaternary tellurides SrLnCuTe3, the fabrication of which has been a challenge until this work. Data on the crystal structure of tellurides complete the series of quaternary strontium chalcogenides SrLnCuCh3 (Ch = S, Se, Te). Single crystals of the compounds were synthesized from the elements by the halogenide-flux method at 1070 K. The compounds are crystallizing in two space groups Pnma (Ln = Sm, Gd and Tb) and Cmcm (Ln = Dy-Tm and Lu). For SrSmCuTe3 (a = 11.4592(7), b = 4.3706(3), c = 14.4425(9) Å, space group: Pnma) with the largest lanthanoid cation, Sr2+ shows C.N. = 7, whereas Sm3+ reveals a diminished coordination number C.N. = 6. For SrLuCuTe3 (a = 4.3064(3), b = 14.3879(9), c = 11.1408(7) Å, space group: Cmcm) with the smallest lanthanoid cation, coordination numbers of six are realized for both high-charged cations (Sr2+ and Lu3+: C.N. = 6). The cations Sr2+, Ln3+, Cu+ each take independent positions. The structures are built by distorted [CuTe4]7- tetrahedra, forming the infinite chains {∞1[Cu(Te1)1/1t(Te2)1/1t(Te3)2/2e]5−} along [010] in SrLnCuTe3 (Ln = Sm, Gd and Tb) and [100] in SrLnCuTe3 (Ln = Dy-Tm and Lu). The distortion of the polyhedra [CuTe4]7- was compared for the whole series SrLnCuTe3 by means of τ4-descriptor for the four coordinating Te2- anions, which revealed a decrease in the degree of distortion with a decreasing radius at Ln3+. The distorted octahedra [LnTe6]9- form layers {∞2[Ln(Te1)2/2(Te2)2/2(Te3)2/2]3−}. The distorted octahedra and tetrahedra fuse to form parallel layers {∞2[CuLnTe3]2−} and between them, the Sr2+ cations providing three-dimensionality of the structure are located. In the SrLnCuTe3 (Ln = Sm, Gd and Tb) structures, the Sr2+ cations center capped the trigonal prisms [SrTe6+1]12−, united in infinite chains {∞1[Sr(Te1)2/2(Te2)3/3(Te3)2/2]4−} along the [100] direction. The domains of existence of the Ba2MnS3, BaLaCuS3, Eu2CuS3 and KZrCuS3 structure types are defined in the series of orthorhombic chalcogenides SrLnCuCh3 (Ch = S, Se and Te). The tellurides SrLnCuTe3 (Ln = Tb-Er) of both structure types in the temperature range from 2 up to 300 K are paramagnetic, without showing clear signs of a magnetic phase transition.Item Open Access Temperature-resolved crystal structure of ethylene carbonate(2025) Westphal, Lea; Kochetov, Vladislav; Baran, Volodymyr; Hölderle, Tobias; Avdeev, Maxim; Diadkin, Vadim; Marshall, Kenneth; Schökel, Alexander; Opri, Klaudia; Niewa, Rainer; Porcher, Florence; Müller-Buschbaum, Peter; Senyshyn, AnatoliyEthylene carbonate (EC) is an organic solvent of the class of carbonate esters, which is used in state-of-the-art Li-ion batteries as part of the electrolyte mixture, being primarily responsible for the formation of a solid electrolyte interface. Thermal analysis showed that the sample’s melting point is 309 K. The crystal structure of EC is investigated using powder diffraction in a temperature range from 3 K up to its melting point, using neutron- and synchrotron-based radiation. Over the whole temperature range, the sample shows single-phase behavior with the space group being C 2/ c (No. 15), and given the detailed temperature dependence of the structural evolution, thermodynamic and mechanical properties of solid EC are studied. The local structure in both solid and liquid states was additionally investigated by total scattering diffraction and analysis of the pair distribution function. The results obtained are discussed in line with those of molecular dynamics simulations.Item Open Access The first members of the monoclinic lanthanoid(III) fluoride oxoarsenate(III) series Ln2F2[As2O5] (Ln=La - Nd and Sm)(2025) Locke, Ralf J. C.; Zimmer, Frank C.; Schleid, ThomasIn synthesis experiments for the preparation of Ln5F3[AsO3]4 representatives in evacuated glassy silica ampoules at temperatures of maximum 825 °C, surprisingly compounds with the composition Ln2F2[As2O5] could be obtained and subsequently also reproduced on target. The new Ln2F2[As2O5] representatives with Ln = La - Nd and Sm crystallize needle‐shaped in the monoclinic space group P21/c with lattice parameters ranging from a = 793.24(5) pm, b = 1346.39(9) pm, c = 1359.41(9) pm and β = 106.932(3)° for La2F2[As2O5] to a = 769.11(5) pm, b = 1307.50(9) pm, c = 1328.74(9) pm and β = 106.819(3)° for Sm2F2[As2O5] with Z = 8. Their crystal structure can be broken down into two parts consisting of infinite [Ln2F2]4+ and discrete [As2O5]4− units. Three distinct kinds of fluoride anions are trigonally planar surrounded by lanthanoid cations and another one carries even a fourth of them in their coordination sphere with a secondary contact resulting in a distorted tetrahedron. These [FLn3]8+ and [FLn3+1]11+ building blocks share common corners and edges creating strands {[F2Ln2]4+}, which propagate along [100]. The four different As3+ lone‐pair cations form ψ1‐tetrahedra [AsO3]3− with three oxygen atoms and are conversurally linked pairwisely creating dinuclear pyroanionic [As2O5]4− units. These [As2O5]4− groups arrange themselves alternatingly along [100] with their lone pairs pointing into central empty channels. The {[F2Ln2]4+} strands are linked to the [As2O5]4− units via four distinguishable Ln3+ cations providing them coordination numbers of eight and nine. Raman spectroscopy confirmed that no (OH)− groups resulting from the synthesis were present apt to replace part of the F− and the stoichiometry Ln2F2[As2O5] was verified using WDXS elemental analyses.Item Open Access Activation and fixation of atmospheric CO2 through a 1,2,3‐triazole‐based mesoionic carbene-borane adduct(2025) Neubrand, Maren; Stubbe, Jessica; Rudolf, Richard; Walter, Robert R. M.; Nößler, Maite; Sarkar, BiprajitCapturing atmospheric CO2 and converting it to valuable chemicals are important goals in contemporary science. We present here a simple, transition metal‐free triazolylidene–borane adduct that can capture atmospheric CO2 and convert it to formate. Several key intermediates were isolated and characterized by a combination of multinuclear NMR spectroscopy, IR spectroscopy and single crystal X‐ray diffraction. A first closed cycle for the conversion of CO2 to formic acid by using the aforementioned triazolylidene–borane compound is presented as well.Item Open Access Sulfur‐composites derived from poly(acrylonitrile) and poly(vinylacetylene) : a comparative study on the role of pyridinic and thioamidic nitrogen(2023) Kappler, Julian; Klostermann, Sina V.; Lange, Pia L.; Dyballa, Michael; Veith, Lothar; Schleid, Thomas; Weil, Tanja; Kästner, Johannes; Buchmeiser, Michael R.Sulfurized poly(acrylonitrile) (SPAN) is a prominent example of a highly cycle stable and rate capable sulfur/polymer composite, which is solely based on covalently bound sulfur. However, so far no in‐depth study on the influence of nitrogen in the carbonaceous backbone, to which sulfur in the form of thioketones and poly(sulfides) is attached, exists. Herein, we investigated the role of nitrogen by comparing sulfur/polymer composites derived from nitrogen‐containing poly(acrylonitrile) (PAN) and nitrogen‐free poly(vinylacetylene) (PVac). Results strongly indicate the importance of a nitrogen‐rich, aromatic carbon backbone to ensure full addressability of the polymer‐bound sulfur and its reversible binding to the aromatic backbone, even at high current rates. This study also presents key structures, which are crucial for highly cycle and rate stable S‐composites.Item Open Access Alkaline earth metal nitride chalcogenides, Ca6N2Se3, Sr6N2Se3 and Sr6N2Te3(2025) Sun, Guowei; Niewa, RainerThe novel isotypic hexagonal alkaline earth metal nitride chalcogenides Ca6N2Se3, Sr6N2Se3 and Sr6N2Te3 (Rmathematical equation (No.167); Z=6) were synthesized from Ca(Sr)/Na flux at 1173 K. The compounds belong to the rare class of ternary metal nitride chalcogenides. The structures feature the shortest Ca/Sr-N bonds within the regular trigonal antiprismatic coordination (Ca-N: 235.17(8); Sr-N: 251.20(6) pm). Two crystallographic distinct nitrogen atoms are coordinated in a trigonal antiprism and a twisted trigonal prism, respectively, and are alternatively condensed via trigonal trans-faces to form one-dimensional chains mathematical equation . The chalcogenide ions in comparison realize rather ambiguous environments. Raman spectroscopic data are reportedItem Open Access Filling voids : cubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W(2026) Höhn, Peter; Link, Lukas; Reckeweg, Olaf; Prots, Yurii; Niewa, RainerCubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W are synthesized by various high-temperature reactions and their respective crystal structures were investigated using X-ray diffraction. Red transparent crystals (Ba6N5/6)2[NbVN4][CN2]6 in space group Im3 as aristotype exhibit site disorder of the [NbN4]7 anion and an about 42% occupation of a further nitride ion site for charge balance. Upon reduced nitrogen content on the latter site, dark gray (Ba6Nx)2[NbN4][CN2]6 with x=0.55(7) crystallizes in the direct subgroup I23 with fully ordered tetrahedra. This structure is also observed for crystals of red (Ba6N2/3)2[HfIVN4][CN2]6 with ordered tetrahedra [HfN4]8. Dark red (Ba6N)2[WVIN4][CN2]6 with enlarged nitride content balancing the higher charge of the transition metal in oxidation state þ6 crystallizes in the different direct subgroup Pn3, and shows an unlike site order for the nitride ions. Depending on the (dis)order of the nitride ions, the nitridometalate ions (dis)order in different patterns. Powder diffraction data of microcrystalline samples indicate identical structures of the zirconium and hafnium compounds in I23, but realization of space group Pn3 of the red compounds of not only molybdenum and tungsten but also niobium and tantalum. The IR spectra corroborate the identity of the carbodiimide anion.Item Open Access On the rubidium thiotellurate(IV) Rb2[TeS3] and its tritohydrate Rb2[TeS3] ⋅ 1/3 H2O(2024) Wolff, Klaus K.; Pfitzner, Arno; Schleid, ThomasRb2[TeS3] and Rb2[TeS3] ⋅ 1/3 H2O were obtained from rubidium azide (RbN3), tellurium and sulfur in 2 : 1 : 3 molar ratios from evacuated fused silica ampoules at 500 °C under more or less anhydrous conditions. Both compounds crystallize orthorhombically in the space group P212121 (Rb2[TeS3]: a=873.42(6) pm, b=1316.73(9) pm, c=2064.59(14) pm; Rb2[TeS3] ⋅ 1/3 H2O: a=872.97(6) pm, b=1299.82(9) pm, c=2148.26(15) pm, both at -173 °C for Z =12) and contain discrete ψ1‐tetrahedral [TeS3]2- anions (d(Te-S)=232-236 pm) in layerwise arrangements. The difference results from the water of hydration in Rb2[TeS3] ⋅ 1/3 H2O, which increases the coordination numbers of half of the six crystallographically distinct Rb+ cations from six and seven (only sulfur) to seven and almost eight by providing with oxygen from H2O an extra ligand (d(Rb-O)=290-318 pm). Red Rb2[TeS3] transforms pseudo‐topotactically into yellow Rb2[TeS3] ⋅ 1/3 H2O immediately upon contact with moist atmosphere. The compounds were screened with X‐ray diffraction, Raman and diffuse reflectance spectroscopy as well as thermal analysis.Item Open Access Control of molecular packing in crystal and electron communication of two ferrocenyl moieties across chiral isomannide or isosorbide bridge(2023) Zullo, Valerio; Guo, Tianao; Iuliano, Anna; Ringenberg, Mark R.Intramolecular electronic communication between electrochemically active groups connected by a bridging moiety can be modified through small changes in the spatial disposition of the redox active moieties and/or by the nature of the central core. In this study, chiral bio-based compounds, namely isomannide and isosorbide, were employed as cheap and easy-to-functionalize chiral scaffolds to bridge two ferrocenyl electroactive moieties. The crystal structures of both bis-ferrocenyl diester complexes were studied and they showed that the chirality of the bridge results in an open or tight helical crystal packing. The electron communication between the two electroactive units in the mixed valent monocations was also investigated using electrochemistry (cyclic voltammetry and differential pulsed voltammetry), and spectroelectrochemistry in the UV-Vis NIR. A computational study through time-dependent DFT was also employed to gain greater insight into the results obtained.