©Roman Hansi
Research interests
Peter Weinbergers main research interests are located in the field of molecular magnetic compounds based on Fe(II) spin crossover (SCO) systems as well as lanthanide and actinide coordination chemistry and on applied research on materials for thermochemical energy storage.
His group focuses on:
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Structural tuning of tetrazole-BODIPY Ag(I) coordination compounds via co-ligand addition and counterion variation
The coordination properties of a previously described fluorescence active ligand (L), consisting of a coordinating unit (1H-tetrazol-1-yl) and a fluorophore (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative) towards Ag(I) were investigated. Additionally, the influence of different anions (BF4−, PF6−, PF2O2−, ClO4−, ReO4− and NO3−) and a co-ligand (CH3CN) on the crystal structure formation and intramolecular interactions of the Ag(I) coordination compounds was studied. Beside structural investigations via single crystal X-ray diffraction, bulk characterization of the coordination compounds was conducted in both solution and solid-state, including NMR (1H, 11B, 19F, 31P and 13C), ATR-IR, UV-vis and photoluminescence spectroscopy as well as PXRD. Eleven distinct coordination compounds are reported, each falling into one of four classes: the first group (I) comprises of a mononuclear complex, whereas group (II) consists of dinuclear complexes with ligand bridged metal centers (Ag(I)) and weak intermetallic interactions (∼4 Å). Group (III) likewise includes dinuclear complexes, but the bridging mode was prevented and the Ag–Ag distance was reduced (∼3.2 Å) upon the addition of a co-ligand. Group (IV), a structurally diverse category consists of coordination polymers, which in some cases show even shorter intermetallic contacts (<3.1 Å). All investigated coordination compounds exhibit photoluminescence in the solid state, with structurally dependent emission maxima distinct from those of the ligand.
"Structural tuning of tetrazole-BODIPY Ag(I) coordination compounds via co-ligand addition and counterion variation", Li, R., Crystengcomm, /, Schöbinger, M., Huber, M., Stöger, B., Hametner, C., & Weinberger, P. (2025). †. 27, 2689. doi.org/10.1039/d5ce00197h
Multifunctional bistable magnetic materials, particularly spin crossover (SCO)-photoluminescence (PL) systems, are of significant interest for molecular sensor applications. However, achieving predictable SCO tuning while simultaneously combining these properties remains a challenge. In this context, we synthesized a series of heteroleptic Fe(II) coordination compounds incorporating a fluorescence-active BODIPY-based 1H-tetrazole ligand (4,4-difluoro-1,3,5,7-tetramethyl-8-[(1H-tetrazol-1-yl)methyl]-4-bora-3a,4a-diaza-s-indacene), with the compounds differing by counteranion size (BF4– < ClO4– ≪ PF6– < CF3SO3– < SbF6–). Remarkably, CF3SO3– coordinates to Fe(II), while all other anions form noncoordinating isostructural complexes. The coordination of CF3SO3– can be reversed through a topochemical exchange with H2O. Magnetic studies reveal that for the isostructural coordination compounds with noncoordinating anions, increasing anion size leads to incomplete and/or less abrupt spin transitions. The complex incorporating noncoordinating BF4– exhibits the most abrupt and complete SCO, demonstrating a weak yet synergistic interplay between SCO and PL signal modulation upon the spin transition, an effect attributed to electronic coupling. While not featuring SCO, the compound with a coordinating CF3SO3– anion is crystallographically interesting as it features a phase transition, forming a subtle 4-fold superstructure below 180 K. Our study provides a versatile platform for independent tuning of SCO and PL properties, paving the way for application in multifunctional devices.
"T 1/2 Tuning in a Synergistic BODIPY-Tetrazole Fe(II) Spin Crossover-Photoluminescence System via Counterion Variation", Huber, M., Schöbinger, M., Stöger, B., Reissner, M., & Weinberger, P. (2025). 25, 56. doi.org/10.1021/acs.cgd.5c00492
The combination of spin crossover (SCO) with guest incorporation properties has attracted the interest of researchers in the last couple of decades and has led to the design of numerous SCO porous coordination polymers (SCO-PCPs). The most famous class of SCO-PCPs is the Hofmann-type network, which is a very promising material for (chemo)sensing applications. Different strategies have been carried out to expand the classic structure {Fe(pz)[MII(CN)4]} (M = Ni, Pd, Pt) to get larger cavities, but the resulting compounds often showed a poor magnetic behavior. In this work, we present wide-mesh-size spin-switching Hofmann-type networks based on tetrakis-cyanoacetylides synthesized with a newly developed method, resulting in compounds with the general formula {Fe(pz)[M(C3N)4]} (M=Ni, Pd, Pt). The compounds were characterized in their structural, magnetic, and spectroscopic properties. They present 5-fold larger cavities and a drastic increase in porosity. The desired hysteretic and guest-dependent spin-crossover behavior is retained, and in situ chemo-switching of the spin state and the memory effect are also observed.
"Tetrakis-Cyanoacetylides as Building Blocks for a Second Generation of Spin-Switchable Hofmann-type Networks with Enhanced Porosity", Zeni, W., Mü, D., Artner, W., Giester, G., Reissner, M., & Weinberger, P. (2024). Cite This: Inorg. Chem, 63, 17067–17076. doi.org/10.1021/acs.inorgchem.4c02732
Two novel nitrogen-rich lanthanide compounds of 5,5´-(azobis)tetrazolide (ZT) were synthesized and structurally characterized. The dinuclear, isostructural compounds [Ce2(ZT)2CO3(H2O)12] · 4 H2O (1) and [Pr2(ZT)2CO3(H2O)12] · 4 H2O (2) were synthesized via two independent routes. Compound 1 was obtained after partial Lewis acidic decomposition of ZT by CeIV in aqueous solution of (NH4)2Ce(NO3)6 and Na2ZT. Compound 2 was obtained by crystallization from aqueous solutions of Pr(NO3)3, Na2ZT, and Na2CO3. By X-ray diffraction analysis at 200 K, it was found that the trivalent lanthanide cations are bridged by a bidentate carbonato ligand and each cation is further coordinated by six H2O ligands and one ZT ligand thus being ninefold coordinated.
“Controlling complexation behaviour of early lanthanides via the subtle interplay of their Lewis acidity with the chemical stability of 5,5´-(azobis)tetrazolide”, P. Weinberger, G. Giester, G. Steinhauser, Z. Anorg. Allg. Chem., 646 (2020) 1882–1885.
https://doi.orf/10.1002/zaac.202070231
Work in Progresss, PhD Thesis Sophia Mundigler
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µTCM Heat Battery
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Mixed magnesium, cobalt, nickel, copper, and zinc sulfates as thermochemical heat storage materials
Thermochemical energy storage is an emerging technology being researched for harvesting waste heat and promoting integration of renewable energy in order to combat climate change. While many simple salts such as MgSO4⋅7H2O have been investigated thoroughly, there remains much work to be done in the domain of materials that take advantage of synergetic effects of multiple different cations located in the same crystal. To this end, a solid solution library of divalent metal sulfates of the formula M1-xM2xSO4·nH2O (M, M2 = Mg, Co, Ni, Cu, Zn) has been synthesized. Following X-ray powder diffraction to confirm phase purity, scanning electron microscopy provided insight into particle morphology. One of the most conspicuous features was the presence of star-shaped cracks in some of the materials, which may contribute to increased surface area and enhance reaction kinetics. The simultaneous thermal analysis of the mixed salt sulfates led to several conclusions. Corresponding to the high initial dehydration barrier of NiSO4⋅6H2O, incorporation of nickel into other sulfates led to lower degrees of dehydration at low temperatures. The opposite effect was observed with the addition of copper. Of great interest was the surprisingly facile dehydration of hydrated Mg0.25Zn0.75SO4, which exceeded that of both pure MgSO4⋅7H2O and ZnSO4⋅7H2O. This promising compound is one representative of three different compounds with 75 % zinc which all have the highest dehydration activity up to 100 °C of all compounds in the series of hydrates of M1-xZnxSO4·nH2O (M = Mg, Ni, Cu).
"Mixed magnesium, cobalt, nickel, copper, and zinc sulfates as thermochemical heat storage materials", Jakob Smith, Peter Weinberger, Andreas Werner, Measurement: Energy, Volume 4, 2024, 100027, ISSN 2950-3450, doi.org/10.1016/j.meaene.2024.100027
To improve energy efficiency and reduce greenhouse gas emissions, energy storage technologies are of paramount importance. Thermochemical energy storage (TCES) materials offer high energy storage densities, and systems based on the dehydration of common salt hydrates like MgSO4·7H2O have been extensively investigated, though frequent problems such as agglomeration and unfavorable kinetics highlight the need for further material development. We consulted our VIENNA TCES-database and became aware of the Tutton salts, A2M(XO4)2·6H2O, (X = S or Se) which have also been previously investigated as TCES materials, although the effects of cation substitution on reactivity had remained poorly characterized. Herein, we report the synthesis and characterization of 41 mixed Tutton salts with the composition K2Zn1-xMx (SO4)2·6H2O (M = Mg, Co, Ni, Cu). Two trends were readily apparent: increasing the amount of nickel leads to a predictable increase in the dehydration onset temperature while preserving the simple form of the single dehydration step observed, while the use of copper leads to a predictable decrease in dehydration onset.
"Dehydration performance of a novel solid solution library of mixed Tutton salts as thermochemical heat storage materials", Smith, J., Weinberger, P., & Werner, A. (2024). Journal of Energy Storage, 78, 2352–152. doi.org/10.1016/j.est.2023.110003
Salt hydrates are highly promising materials for thermochemical energy storage applications to store waste heat below 200 ◦C. Although highly researched and theoretically promising, in practical applications salt hydrates often cannot fulfill expectations. Based on the promising results of the Ca-oxalate monohydrate/Ca-oxalate system, other Ca-dicarboxylate salt hydrates were investigated to determine whether potential materials for heat storage can be found amongst them. A simultaneous thermal analysis showed that all candidates are applicable in the temperature range of 100–200 ◦C, and thermally stable up to 220 ◦C. Calcium malonate dihydrate (637 J/g), calcium terephthalate trihydrate (695 J/g), and tetrafluoro calcium terephthalate tetrahydrate (657 J/g) have shown higher enthalpies of dehydration than Ca-oxalate monohydrate. Due to the investigation of derivatives of Ca-terephthalate, it is possible to report the crystal structure of 2-fluoro calcium terephthalate. In single crystals, it forms a trihydrate and crystallizes in the Pmna space group (Z = 4, Z’ = 1/2 ) forming infinite chains of Ca atoms. De- and rehydration reactions of the most promising candidates were studied in situ with powder X-ray diffraction showing the structural changes between the hydrate and anhydrate states.
"Characterization of Ca-Dicarboxylate Salt Hydrates as Thermochemical Energy Storage Materials", Werner, J., Smith, J., Stöger, B., Artner, W., Werner, A., & Weinberger, P. (2023). Crystals, 13(10). doi.org/10.3390/CRYST13101518
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