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Commemorating 150 Years of Justus von Liebig’s Legacy
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Commemorating 150 Years of Justus von Liebig’s Legacy

A special issue of Chemistry (ISSN 2624-8549).

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 34690

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Christoph Janiak

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Guest Editor
Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
Interests: metal-organic frameworks; nanoparticles; catalysis; coordination polymers
Prof. Dr. Sascha Rohn

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Guest Editor
Department of Food Chemistry and Analysis, Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany
Interests: food proteins; secondary plant metabolites; compound stability and interactions
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Georg Manolikakes

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Department of Chemistry-Organic Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. Geb. 54, D-67663 Kaiserslautern, Germany
Interests: organic synthesis; synthetic methodology; stereoselecticve synthesis; sustainable synthesis; multicomponent reactions; fixation of sulfur dioxide into small organic molecules
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Justus Freiherr von Liebig (1803–1873) was one of the great German chemists of the 19th Century CE, and it is our privilege to honour his achievements and legacy on the occasion of the sesquicentennial of his death. Although he is primarily remembered today as an organic chemist, his contributions covered numerous aspects of organic, inorganic, applied, and technical chemistry, and we hope to do justice to his multiple facets in this Special Issue.

From the earliest class in the chemistry practical laboratory, today’s students encounter the ubiquitous Liebig’s condensor, the classical counter-current water-cooled condensor used for reactions under reflux or for distillations. Liebig often worked at the interface of organic and inorganic chemistry, exemplified by his work on silver fulminate, an isomer of the silver cyanate prepared by Wöhler.

Liebig was one of the pioneers in systematic organic chemistry, being prominent in the development of the theory of radicals and being a master of the art of transformation and degradation of organic materials. His output in his most creative years is prodigious.

In addition to his research, Liebig was a scientist in the von Humboldt tradition and made enormous contributions to the teaching of both theoretical and practical chemistry.

Less well known to the chemical audience are his exceptional contributions to plant and animal physiology and nutrition. Once again, these had a basis in the fundamental chemistry of life and bridged classical organic and inorganic chemistry.

Liebig had wide-ranging interests in food technology and nutrition and was particularly involved in the technology of preparing meat and vegetable extracts, some of which are well known to Anglophile audiences even today. His methods for producing beef extracts resulted in the establishment of Liebig’s Extract of Meat Company, which is the linear antecedent of the UK product «Oxo». Similarly, his process for the manufacture of yeast extracts can be seen as the progenitor of the UK savoury spread «Marmite».

We welcome contributions commemorating all aspects of Liebig’s life and work.

Prof. Dr. Christoph Janiak
Prof. Dr. Sascha Rohn
Prof. Dr. Georg Manolikakes
Guest Editors

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Editorial

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14 pages, 6204 KiB  
Editorial
Justus von Liebig
by Siegfried Schindler
Chemistry 2023, 5(2), 1046-1059; https://doi.org/10.3390/chemistry5020071 - 06 May 2023
Viewed by 1870
Abstract
This is a short overview of the life and achievements of Justus von Liebig. Clearly, this can only be an incomplete and somewhat personal view of the author, who has been a professor of inorganic chemistry at Justus Liebig University since 2002. Having [...] Read more.
This is a short overview of the life and achievements of Justus von Liebig. Clearly, this can only be an incomplete and somewhat personal view of the author, who has been a professor of inorganic chemistry at Justus Liebig University since 2002. Having already been interested in the work of Liebig for many years, and with a strong connection to the Liebig Museum in Giessen, the author hopes to provide some useful information about this great chemist, one of the founders of modern chemistry. The reader should find many interesting, probably new, facts about Liebig’s major impact on chemistry, agriculture, nutrition, and pharmacology. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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Research

Jump to: Editorial

18 pages, 3075 KiB  
Article
In Pursuit of Next Generation N-Heterocyclic Carbene-Stabilized Copper and Silver Precursors for Metalorganic Chemical Vapor Deposition and Atomic Layer Deposition Processes
by Ilamparithy Selvakumar, Nils Boysen, Marco Bürger and Anjana Devi
Chemistry 2023, 5(3), 2038-2055; https://doi.org/10.3390/chemistry5030138 - 20 Sep 2023
Viewed by 1332
Abstract
Volatile, reactive, and thermally stable organometallic copper and silver complexes are of significant interest as precursors for the metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) of ultra-thin metallic films. Well-established CuI and AgI precursors are commonly stabilized by [...] Read more.
Volatile, reactive, and thermally stable organometallic copper and silver complexes are of significant interest as precursors for the metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) of ultra-thin metallic films. Well-established CuI and AgI precursors are commonly stabilized by halogens, phosphorous, silicon, and oxygen, potentially leading to the incorporation of these elements as impurities in the thin films. These precursors are typically stabilized by a neutral and anionic ligand. Recent advancements were established by the stabilization of these complexes using N-heterocyclic carbenes (NHCs) as neutral ligands. To further enhance the reactivity, in this study the anionic ligand is sequentially changed from β-diketonates to β-ketoiminates and β-diketiminates, yielding two new CuI and two new AgI NHC-stabilized complexes in the general form of [M(NHC) (R)] (M = Cu, Ag; R = β-ketoiminate, β-diketiminate). The synthesized complexes were comparatively analyzed in solid, dissolved, and gaseous states. Furthermore, the thermal properties were investigated to assess their potential application in MOCVD or ALD. Among the newly synthesized complexes, the β-diketiminate-based [Cu(tBuNHC) (NacNacMe)] was identified to be the most suitable candidate as a precursor for Cu thin film deposition. The resulting halogen-, oxygen-, and silicon-free CuI and AgI precursors for MOCVD and ALD applications are established for the first time and set a new baseline for coinage metal precursors. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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29 pages, 5231 KiB  
Article
Syntheses, Crystal and Electronic Structures of Rhodium and Iridium Pyridine Di-Imine Complexes with O- and S-Donor Ligands: (Hydroxido, Methoxido and Thiolato)
by Michel Stephan, Max Völker, Matthias Schreyer and Peter Burger
Chemistry 2023, 5(3), 1961-1989; https://doi.org/10.3390/chemistry5030133 - 05 Sep 2023
Viewed by 1298
Abstract
The syntheses of new neutral square-planar pyridine di-imine rhodium and iridium complexes with O- and S-donor (OH, OR, SH, SMe and SPh) ligands along with analogous cationic compounds are reported. Their crystal and electronic structures are investigated in detail with a focus on [...] Read more.
The syntheses of new neutral square-planar pyridine di-imine rhodium and iridium complexes with O- and S-donor (OH, OR, SH, SMe and SPh) ligands along with analogous cationic compounds are reported. Their crystal and electronic structures are investigated in detail with a focus on the non-innocence/innocence of the PDI ligand. The oxidation states of the metal centers were analyzed by a variety of experimental (XPS and XAS) and theoretical (LOBA, EOS and OSLO) methods. The dπ-pπ interaction between the metal centers and the π-donor ligands was investigated by theoretical methods and revealed the partial multiple-bond character of the M-O,S bonds. Experimental support is provided by a sizable barrier for the rotation about the Ir-S bond in the methyl thiolato complex and confirmed by DFT and LNO-CCSD(T) calculations. This was corroborated by the high Ir-O and Ir-S bond dissociation enthalpies calculated at the PNO-CCSD(T) level. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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12 pages, 1970 KiB  
Article
Unraveling the Synthesis of SbCl(C3N6H4): A Metal-Melaminate Obtained through Deprotonation of Melamine with Antimony(III)Chloride
by Elaheh Bayat, Markus Ströbele and Hans-Jürgen Meyer
Chemistry 2023, 5(2), 1465-1476; https://doi.org/10.3390/chemistry5020099 - 20 Jun 2023
Viewed by 1423
Abstract
The discovery of melamine by Justus von Liebig was fundamental for the development of several fields of chemistry. The vast majority of compounds with melamine or melamine derivatives appear as adducts. Herein, we focus on the development of novel compounds containing anionic melamine [...] Read more.
The discovery of melamine by Justus von Liebig was fundamental for the development of several fields of chemistry. The vast majority of compounds with melamine or melamine derivatives appear as adducts. Herein, we focus on the development of novel compounds containing anionic melamine species, namely the melaminates. For this purpose, we analyze the reaction of SbCl3 with melamine by differential scanning calorimetry (DSC). The whole study includes the synthesis and characterization of three antimony compounds that are obtained during the deprotonation process of melamine to melaminate with the reaction sequence from SbCl4(C9N18H19) (1) via (SbCl4(C6N12H13))2 (2) to SbCl(C3N6H4) (3). Compounds are characterized by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), and infrared spectroscopy (IR). The results give an insight into the mechanism of deprotonation of melamine, with the replacement of one, two, or eventually three hydrogen atoms from the three amino groups of melamine. The structure of (3) suggests that metal melaminates are likely to form supramolecular structures or metal-organic frameworks (MOFs). Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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12 pages, 2724 KiB  
Communication
Suzuki–Miyaura Reaction in the Presence of N-Acetylcysteamine Thioesters Enables Rapid Synthesis of Biomimetic Polyketide Thioester Surrogates for Biosynthetic Studies
by Sebastian Derra, Luca Schlotte and Frank Hahn
Chemistry 2023, 5(2), 1407-1418; https://doi.org/10.3390/chemistry5020096 - 08 Jun 2023
Cited by 1 | Viewed by 1495
Abstract
Biomimetic N-acetylcysteamine thioesters are essential for the study of polyketide synthases, non-ribosomal peptide synthetases and fatty acid synthases. The chemistry for their preparation is, however, limited by their specific functionalization and their susceptibility to undesired side reactions. Here we report a method [...] Read more.
Biomimetic N-acetylcysteamine thioesters are essential for the study of polyketide synthases, non-ribosomal peptide synthetases and fatty acid synthases. The chemistry for their preparation is, however, limited by their specific functionalization and their susceptibility to undesired side reactions. Here we report a method for the rapid preparation of N-acetylcysteamine (SNAC) 7-hydroxy-2-enethioates, which are suitable for the study of various enzymatic domains of megasynthase enzymes. The method is based on a one-pot sequence of hydroboration and the Suzuki–Miyaura reaction. The optimization of the reaction conditions made it possible to suppress potential side reactions and to introduce the highly functionalized SNAC methacrylate unit in a high yield. The versatility of the sequence was demonstrated by the synthesis of the complex polyketide-SNAC thioesters 12 and 33. Brown crotylation followed by the hydroboration to Suzuki–Miyaura reaction sequence enabled the introduction of the target motif in significantly fewer steps and with a higher overall yield and stereoselectivity than previously described approaches. This is the first report of a transition-metal-catalyzed cross-coupling reaction in the presence of an SNAC thioester. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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17 pages, 6769 KiB  
Article
Reactivity of Rare-Earth Oxides in Anhydrous Imidazolium Acetate Ionic Liquids
by Sameera Shah, Tobias Pietsch, Maria Annette Herz, Franziska Jach and Michael Ruck
Chemistry 2023, 5(2), 1378-1394; https://doi.org/10.3390/chemistry5020094 - 02 Jun 2023
Cited by 3 | Viewed by 1496
Abstract
Rare-earth metal sesquioxides (RE2O3) are stable compounds that require high activation energies in solid-state reactions or strong acids for dissolution in aqueous media. Alternatively, dissolution and downstream chemistry of RE2O3 have been achieved with ionic [...] Read more.
Rare-earth metal sesquioxides (RE2O3) are stable compounds that require high activation energies in solid-state reactions or strong acids for dissolution in aqueous media. Alternatively, dissolution and downstream chemistry of RE2O3 have been achieved with ionic liquids (ILs), but typically with additional water. In contrast, the anhydrous IL 1-butyl-3-methylimidazolium acetate [BMIm][OAc] dissolves RE2O3 for RE = La–Ho and forms homoleptic dinuclear metal complexes that crystallize as [BMIm]2[RE2(OAc)8] salts. Chloride ions promote the dissolution without being included in the compounds. Since the lattice energy of RE2O3 increases with decreasing size of the RE3+ cation, Ho2O3 dissolves very slowly, while the sesquioxides with even smaller cations appear to be inert under the applied conditions. The Sm and Eu complex salts show blue and red photoluminescence and Van Vleck paramagnetism. The proton source for the dissolution is the imidazolium cation. Abstraction of the acidic proton at the C2-atom yields an N-heterocyclic carbene (imidazole-2-ylidene). The IL can be regenerated by subsequent reaction with acetic acid. In the overall process, RE2O3 is dissolved by anhydrous acetic acid, a reaction that does not proceed directly. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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14 pages, 3182 KiB  
Article
On the Redox Equilibrium of TPP/TPPO Containing Cu(I) and Cu(II) Complexes
by Stephanie L. Faber, Nesrin I. Dilmen and Sabine Becker
Chemistry 2023, 5(2), 1288-1301; https://doi.org/10.3390/chemistry5020087 - 17 May 2023
Viewed by 1874
Abstract
Copper(II) clusters of the type [CuII4OCl6L4] (L = ligand or solvent) are a well-studied example of inverse coordination compounds. In the past, they have been studied because of their structural, magnetic, and spectroscopic features. They have [...] Read more.
Copper(II) clusters of the type [CuII4OCl6L4] (L = ligand or solvent) are a well-studied example of inverse coordination compounds. In the past, they have been studied because of their structural, magnetic, and spectroscopic features. They have long been believed to be redox-inactive compounds, but recent findings indicate a complex chemical equilibrium with diverse mononuclear as well as multinuclear copper(I) and copper(II) compounds. Furthermore, depending on the ligand system, such cluster compounds have proven to be versatile catalysts, e.g., in the oxidation of cyclohexane to adipic acid. This report covers a systematic study of the formation of [CuII4OCl6(TPP)4] and [CuII4OCl6(TPPO)4] (TPP = triphenylphosphine, PPh3; TPPO = triphenylphosphine oxide, O=PPh3) as well as the redox equilibrium of these compounds with mononuclear copper(I) and copper(II) complexes such as [CuIICl2(TPPO)2], [{CuIICl2}2(TPPO)2], [{CuIICl2}3(TPPO)2], [{CuII4Cl4}(TPP)4], and [CuICl(TPP)n] (n = 1–3). Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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17 pages, 4227 KiB  
Article
Improved Synthesis and Coordination Behavior of 1H-1,2,3-Triazole-4,5-dithiolates (tazdt2−) with NiII, PdII, PtII and CoIII
by Nils Pardemann, Alexander Villinger and Wolfram W. Seidel
Chemistry 2023, 5(2), 1271-1287; https://doi.org/10.3390/chemistry5020086 - 17 May 2023
Viewed by 1397
Abstract
A new synthetic route to 1H-1,2,3-triazole-4,5-dithiols (tazdtH2) as ligands for the coordination of NiII, PdII, PtII and CoIII via the dithiolate unit is presented. Different N-protective groups were introduced with the corresponding azide [...] Read more.
A new synthetic route to 1H-1,2,3-triazole-4,5-dithiols (tazdtH2) as ligands for the coordination of NiII, PdII, PtII and CoIII via the dithiolate unit is presented. Different N-protective groups were introduced with the corresponding azide via a click-like copper-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) and fully characterized by NMR spectroscopy. Possible isomers were isolated and an alternative synthetic route was investigated and discussed. After removal of the benzyl protective groups on sulfur by in situ-generated sodium naphthalide, complexes at the [(dppe)M] (M = Ni, Pd, Pt), [(PPh3)2Pt] and [(η5-C5H5)Co] moieties were prepared and structurally characterized by XRD analysis. In this process, the by-products 11 and 12 as monothiolate derivatives were isolated and structurally characterized as well. With regioselective coordination via the dithiolate unit, the electronic influence of different metals or protective groups at N was investigated and compared spectroscopically by means of UV/Vis spectroscopy and cyclic voltammetry. Complex [(η5-C5H5)Co(5c)] (10), is subject to a dimerization equilibrium, which was investigated by temperature-dependent NMR and UV/Vis spectroscopy (solution and solid-state). The thermodynamic parameters of the monomer/dimer equilibrium were derived. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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13 pages, 2355 KiB  
Article
Modification of the Bridging Unit in Luminescent Pt(II) Complexes Bearing C^N*N and C^N*N^C Ligands
by Stefan Buss, María Victoria Cappellari, Alexander Hepp, Jutta Kösters and Cristian A. Strassert
Chemistry 2023, 5(2), 1243-1255; https://doi.org/10.3390/chemistry5020084 - 15 May 2023
Cited by 3 | Viewed by 1421
Abstract
In this work, we explored the synthesis and characterization of Pt(II) complexes bearing different tri- and tetradentate luminophores acting as C^N*N- and C^N*N^C-chelators. Thus, we investigated diverse substitution patterns in order to improve their processability and assessed the effects of structural variations on [...] Read more.
In this work, we explored the synthesis and characterization of Pt(II) complexes bearing different tri- and tetradentate luminophores acting as C^N*N- and C^N*N^C-chelators. Thus, we investigated diverse substitution patterns in order to improve their processability and assessed the effects of structural variations on their excited state properties. Hence, a detailed analysis of the different synthetic pathways is presented; the photophysical properties were studied by using steady-state and time-resolved photoluminescence spectroscopy. We determined the absorption and emission spectra, the photoluminescence efficiencies, and the excited state lifetimes of the complexes in fluid solutions at room temperature and frozen glassy matrices at 77 K. Finally, a structure–property relationship was established, showing that the decoration of the bridging unit on the tridentate luminophores only marginally affects the excited state properties, whereas the double cyclometallation related to the tetradentate chelator prolongs the excited state lifetime and increases the photoluminescence quantum yield. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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13 pages, 3496 KiB  
Article
Selective Fluorimetric Detection of Pyrimidine Nucleotides in Neutral Aqueous Solution with a Styrylpyridine-Based Cyclophane
by Julika Schlosser, Julian F. M. Hebborn, Daria V. Berdnikova and Heiko Ihmels
Chemistry 2023, 5(2), 1220-1232; https://doi.org/10.3390/chemistry5020082 - 11 May 2023
Viewed by 1535
Abstract
A styrylpyridine-containing cyclophane with diethylenetriamine linkers is presented as a host system whose association with representative nucleotides was examined with photometric and fluorimetric titrations. The spectrometric titrations revealed the formation of 1:1 complexes with log Kb values in the range of 2.3–3.2 [...] Read more.
A styrylpyridine-containing cyclophane with diethylenetriamine linkers is presented as a host system whose association with representative nucleotides was examined with photometric and fluorimetric titrations. The spectrometric titrations revealed the formation of 1:1 complexes with log Kb values in the range of 2.3–3.2 for pyrimidine nucleotides TMP (thymidine monophosphate), TTP (thymidine triphosphate) and CMP (cytidine monophosphate) and 3.8–5.0 for purine nucleotides AMP (adenosine monophosphate), ATP (adenosine triphosphate), and dGMP (deoxyguanosine monophosphate). Notably, in a neutral buffer solution, the fluorimetric response to the complex formation depends on the type of nucleotide. Hence, quenching of the already weak fluorescence was observed with the purine bases, whereas the association of the cyclophane with pyrimidine bases TMP, TTP, and CMP resulted in a significant fluorescence light-up effect. Thus, it was demonstrated that the styrylpyridine unit is a useful and complementary fluorophore for the development of selective nucleotide-targeting fluorescent probes based on alkylamine-linked cyclophanes. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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17 pages, 3847 KiB  
Article
A Pathway for Aldol Additions Catalyzed by l-Hydroxyproline-Peptides via a β-Hydroxyketone Hemiaminal Intermediate
by Lo’ay Ahmed Al-Momani, Heinrich Lang and Steffen Lüdeke
Chemistry 2023, 5(2), 1203-1219; https://doi.org/10.3390/chemistry5020081 - 10 May 2023
Cited by 1 | Viewed by 1344
Abstract
While the use of l-proline-derived peptides has been proven similarly successful with respect to enantioselectivity, the physico-chemical and conformational properties of these organocatalysts are not fully compatible with transition state and intermediate structures previously suggested for l-proline catalysis. l-Proline or [...] Read more.
While the use of l-proline-derived peptides has been proven similarly successful with respect to enantioselectivity, the physico-chemical and conformational properties of these organocatalysts are not fully compatible with transition state and intermediate structures previously suggested for l-proline catalysis. l-Proline or l-4-hydroxyproline catalysis is assumed to involve proton transfers mediated by the carboxylic acid group, whereas a similar mechanism is unlikely for peptides, which lack a proton donor. Herein, we prepared an array of hydroxyproline-based dipeptides through amide coupling of Boc-protected cis- or trans-4-l-hydroxyproline (cis- or trans-4-Hyp) to benzylated glycine (Gly-OBn) and l-valine (l-Val-OBn) and used these dipeptides as catalysts for a model aldol reaction. Despite the lack of a proton donor in the catalytic site, we observed good stereoselectivities for the R-configured aldol product both with dipeptides formed from cis- or trans-4-Hyp at moderate conversions after 24 h. To explain this conundrum, we modeled reaction cycles for aldol additions in the presence of cis-4-Hyp, trans-4-Hyp, and cis- and trans-configured 4-Hyp-peptides as catalysts by calculation of free energies of conformers of intermediates and transition states at the density functional theory level (B3LYP/6-31G(d), DMSO PCM as solvent model). While a catalytic cycle as previously suggested with l-proline is also plausible for cis- or trans-4-Hyp, with the peptides, the energy barrier of the first reaction step would be too high to allow conversions at room temperature. Calculations on modeled transition states suggest an alternative pathway that would explain the experimental results: here, the catalytic cycle is entered by the acetone self-adduct 4-hydroxy-4-methylpentan-2-one, which forms spontaneously to a small extent in the presence of a base, leading to considerably reduced calculated free energy levels of transition states of reaction steps that are considered rate-determining. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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19 pages, 1104 KiB  
Article
Platform Chemicals from Ethylene Glycol and Isobutene: Thermodynamics “Pays” for Biomass Valorisation and Acquires “Cashback”
by Sergey P. Verevkin and Aleksandra A. Zhabina
Chemistry 2023, 5(2), 1171-1189; https://doi.org/10.3390/chemistry5020079 - 09 May 2023
Viewed by 1495
Abstract
Ethylene glycol (EG) produced from biomass is a promising candidate for several new applications. In this paper, EG derivatives such as mono- and di-tert-butyl ethers are considered. However, accurate thermodynamic data are essential to optimise the technology of the direct tert-butyl ether EG [...] Read more.
Ethylene glycol (EG) produced from biomass is a promising candidate for several new applications. In this paper, EG derivatives such as mono- and di-tert-butyl ethers are considered. However, accurate thermodynamic data are essential to optimise the technology of the direct tert-butyl ether EG synthesis reaction or reverse process isobutene release. The aim of this work is to measure the vapour pressures and combustion energies for these ethers and determine the vaporisation enthalpies and enthalpies of formation from these measurements. Methods based on the First and Second Law of Thermodynamics were combined to discover the reliable thermodynamics of ether synthesis reactions. The thermochemical data for ethylene glycol tert-butyl ethers were validated using structure–property correlations and quantum chemical calculations. The literature results of the equilibrium study of alkylation of EG with isobutene were evaluated and the thermodynamic functions of ethylene glycol tert-butyl ethers were derived. The energetics of alkylation determined according to the “First Law” and the “Second Law” methods agree very well. Some interesting aspects related to the entropy of ethylene glycol tert-butyl ethers were also revealed and discussed. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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14 pages, 8666 KiB  
Article
Activated Carbon from Sugarcane Bagasse: A Low-Cost Approach towards Cr(VI) Removal from Wastewater
by Rana Ahmed, Inga Block, Fabian Otte, Christina Günter, Alysson Duarte-Rodrigues, Peter Hesemann, Amitabh Banerji and Andreas Taubert
Chemistry 2023, 5(2), 1124-1137; https://doi.org/10.3390/chemistry5020077 - 09 May 2023
Viewed by 2180
Abstract
The potential of pretreated sugarcane bagasse (SCB) as a low-cost and renewable source to yield activated carbon (AC) for chromate CrO42− removal from an aqueous solution has been investigated. Raw sugarcane bagasse was pretreated with H2SO4, H [...] Read more.
The potential of pretreated sugarcane bagasse (SCB) as a low-cost and renewable source to yield activated carbon (AC) for chromate CrO42− removal from an aqueous solution has been investigated. Raw sugarcane bagasse was pretreated with H2SO4, H3PO4, HCl, HNO3, KOH, NaOH, or ZnCl2 before carbonization at 700 °C. Only pretreatments with H2SO4 and KOH yield clean AC powders, while the other powders still contain non-carbonaceous components. The point of zero charge for ACs obtained from SCB pretreated with H2SO4 and KOH is 7.71 and 2.62, respectively. Batch equilibrium studies show that the most effective conditions for chromate removal are a low pH (i.e., below 3) where >96% of the chromate is removed from the aqueous solution. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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17 pages, 4177 KiB  
Article
Surface Functionalization of Calcium Phosphate Nanoparticles via Click Chemistry: Covalent Attachment of Proteins and Ultrasmall Gold Nanoparticles
by Kathrin Kostka and Matthias Epple
Chemistry 2023, 5(2), 1060-1076; https://doi.org/10.3390/chemistry5020072 - 07 May 2023
Viewed by 1807
Abstract
Calcium phosphate nanoparticles (60 nm) were stabilized with either polyethyleneimine (PEI; polycationic electrolyte) or carboxymethylcellulose (CMC; polyanionic electrolyte). Next, a silica shell was added and terminated with either azide or alkyne groups via siloxane coupling chemistry. The particles were covalently functionalized by copper-catalyzed [...] Read more.
Calcium phosphate nanoparticles (60 nm) were stabilized with either polyethyleneimine (PEI; polycationic electrolyte) or carboxymethylcellulose (CMC; polyanionic electrolyte). Next, a silica shell was added and terminated with either azide or alkyne groups via siloxane coupling chemistry. The particles were covalently functionalized by copper-catalyzed azide-alkyne cycloaddition (CuAAC; click chemistry) with proteins or gold nanoparticles that carried the complementary group, i.e., either alkyne or azide. The model proteins hemoglobin and bovine serum albumin (BSA) were attached as well as ultrasmall gold nanoparticles (2 nm). The number of protein molecules and gold nanoparticles attached to each calcium phosphate nanoparticle was quantitatively determined by extensive fluorescent labelling and UV–Vis spectroscopy on positively (PEI) or negatively (CMC) charged calcium phosphate nanoparticles, respectively. Depending on the cargo and the nanoparticle charge, this number was in the range of several hundreds to thousands. The functionalized calcium phosphate particles were well dispersible in water as shown by dynamic light scattering and internally amorphous as shown by X-ray powder diffraction. They were easily taken up by HeLa cells and not cytotoxic. This demonstrates that the covalent surface functionalization of calcium phosphate nanoparticles is a versatile method to create transporters with firmly attached cargo molecules into cells. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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18 pages, 3405 KiB  
Article
Synthesis, Structures and Photophysical Properties of Tetra- and Hexanuclear Zinc Complexes Supported by Tridentate Schiff Base Ligands
by Tobias Severin, Viktoriia Karabtsova, Martin Börner, Hendrik Weiske, Agnieszka Kuc and Berthold Kersting
Chemistry 2023, 5(2), 1028-1045; https://doi.org/10.3390/chemistry5020070 - 02 May 2023
Viewed by 1923
Abstract
The synthesis, structure and photophysical properties of two polynuclear zinc complexes, namely [Zn6L2(µ3-OH)2(OAc)8] (1) and [Zn4L4(µ2-OH)2](ClO4)2 (2 [...] Read more.
The synthesis, structure and photophysical properties of two polynuclear zinc complexes, namely [Zn6L2(µ3-OH)2(OAc)8] (1) and [Zn4L4(µ2-OH)2](ClO4)2 (2), supported by tridentate Schiff base ligand 2,6-bis((N-benzyl)iminomethyl)-4-tert-butylphenol (HL) are presented. The synthesized compounds were investigated using ESI-MS, IR, NMR, UV-vis absorption spectroscopy, photoluminescence spectroscopy and single-crystal X-ray crystallography. The hexanuclear neutral complex 1 comprises six-, five- and four-coordinated Zn2+ ions coordinated by O and N atoms from the supporting ligand and OH- and acetate ligands. The Zn2+ ions in complex cation [Zn4L4(µ2-OH)2]2+ of 2 are all five-coordinated. The complexation of ligand HL by Zn2+ ions leads to a six-fold increase in the intensity and a large blue shift of the ligand-based 1(π-π)* emission. Other biologically relevant ions, i.e., Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+ and Cu2+, did not give rise to a fluorescence enhancement. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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22 pages, 6971 KiB  
Article
Divalent Europium, NIR and Variable Emission of Trivalent Tm, Ho, Pr, Er, Nd, and Ce in 3D Frameworks and 2D Networks of Ln–Pyridylpyrazolates
by Heba Youssef, Jonathan Becker, Clemens Pietzonka, Ilya V. Taydakov, Florian Kraus and Klaus Müller-Buschbaum
Chemistry 2023, 5(2), 1006-1027; https://doi.org/10.3390/chemistry5020069 - 28 Apr 2023
Viewed by 1726
Abstract
The redox reactions of various lanthanide metals with 3-(4-pyridyl)pyrazole (4-PyPzH) or 3-(3-pyridyl)pyrazole (3-PyPzH) ligands yield the 2D network ∞2[Eu(4-PyPz)2(Py)2] containing divalent europium, the 3D frameworks ∞3[Ln(4-PyPz)3] and ∞3[Ln(3-PyPz)3] for [...] Read more.
The redox reactions of various lanthanide metals with 3-(4-pyridyl)pyrazole (4-PyPzH) or 3-(3-pyridyl)pyrazole (3-PyPzH) ligands yield the 2D network ∞2[Eu(4-PyPz)2(Py)2] containing divalent europium, the 3D frameworks ∞3[Ln(4-PyPz)3] and ∞3[Ln(3-PyPz)3] for trivalent cerium, praseodymium, neodymium, holmium, erbium, and thulium as well as ∞3[La(4-PyPz)3], and the 2D networks ∞2[Ln(4-PyPz)3(Py)] for trivalent cerium and thulium and ∞2[Ln2(4-PyPz)6]·Py for trivalent ytterbium and lutetium. The 18 lanthanide coordination polymers were synthesized under solvothermal conditions in pyridine (Py), partly acting as a co-ligand for some networks. The compounds exhibit a variety of luminescence properties, including metal-centered 4f–4f/5d–4f emission in the visible and near-infrared spectral range, metal-to-ligand energy transfer, and ligand-centered fluorescence and phosphorescence. The anionic ligands 3-PyPz− and 4-PyPz− serve as suitable antennas for lanthanide-based luminescence in the visible and near-infrared range through effective sensitization followed by emission through intra–4f transitions of the trivalent thulium, holmium, praseodymium, erbium, and neodymium. ∞2[Ce(4-PyPz)3(Py)], ∞3[Ce(4-PyPz)3], and ∞3[Ce(3-PyPz)3] exhibit strong degrees of reduction in the 5d excited states that differ in intensity compared to the ligand-based emission, resulting in a distinct emission ranging from pink to orange. The direct current magnetic studies show magnetic isolation of the lanthanide centers in the crystal lattice of ∞3[Ln(3-PyPz)3], Ln = Dy, Ho, and Er. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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13 pages, 3094 KiB  
Article
Synthesis, Structure, and Spectroscopic Properties of Luminescent Coordination Polymers Based on the 2,5-Dimethoxyterephthalate Linker
by Aimée E. L. Cammiade, Laura Straub, David van Gerven, Mathias S. Wickleder and Uwe Ruschewitz
Chemistry 2023, 5(2), 965-977; https://doi.org/10.3390/chemistry5020065 - 22 Apr 2023
Cited by 1 | Viewed by 1423
Abstract
We report on the synthesis and the crystal structure of the solvent-free coordination polymer CoII(2,5-DMT) (1) with 2,5-DMT ≡ 2,5-dimethoxyterephthalate which is isostructural to the already reported MnII and ZnII congeners (C2/c, Z [...] Read more.
We report on the synthesis and the crystal structure of the solvent-free coordination polymer CoII(2,5-DMT) (1) with 2,5-DMT ≡ 2,5-dimethoxyterephthalate which is isostructural to the already reported MnII and ZnII congeners (C2/c, Z = 4). In contrast, for M = MgII, a MOF with DMF-filled pores is obtained, namely Mg2(2,5-DMT)2(DMF)2 (2) (P1¯, Z = 2). Attempts to remove these solvent molecules to record a gas sorption isotherm did not lead to meaningful results. In a comparative study, the thermal (DSC/TGA) and luminescence properties of all the four compounds were investigated. The compounds of the MII(2,5-DMT) composition show high thermal stability up to more than 300 °C, with the ZnII compound having the lowest decomposition temperature. MII(2,5-DMT) with MII = MnII, ZnII and 2 show a bright luminescence upon blue light irradiation (λ = 405 nm), whereas CoII in 1 quenches the emission. While ZnII in ZnII(2,5-DMT) and MgII in 2 do not significantly influence the (blue) emission and excitation bands compared to the free 2,5-DMT ligand, MnII in MnII(2,5-DMT) shows an additional metal-centred red emission. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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17 pages, 5683 KiB  
Article
Synthesis of 5-Metalla-Spiro[4.5]Heterodecenes by [1,4]-Cycloaddition Reaction of Group 13 Diyls with 1,2-Diketones
by Hanns M. Weinert, Christoph Wölper and Stephan Schulz
Chemistry 2023, 5(2), 948-964; https://doi.org/10.3390/chemistry5020064 - 20 Apr 2023
Viewed by 1411
Abstract
Monovalent group 13 diyls are versatile reagents in oxidative addition reactions. We report here [1,4]-cycloaddition reactions of β-diketiminate-substituted diyls LM (M = Al, Ga, In, Tl; L = HC[C(Me)NDipp]2, Dipp = 2,6-iPr2C6H3) with [...] Read more.
Monovalent group 13 diyls are versatile reagents in oxidative addition reactions. We report here [1,4]-cycloaddition reactions of β-diketiminate-substituted diyls LM (M = Al, Ga, In, Tl; L = HC[C(Me)NDipp]2, Dipp = 2,6-iPr2C6H3) with various 1,2-diketones to give 5-metalla-spiro[4.5]heterodecenes 1, 4–6, and 8–10, respectively. In contrast, the reaction of LTl with acenaphthenequinone gave the [2,3]-cycloaddition product 7, with Tl remaining in the +1 oxidation state. Compound 1 also reacted with a second equivalent of butanedione as well as with benzaldehyde in aldol-type addition reactions to the corresponding α,β-hydroxyketones 2 and 3, while a reductive activation of a benzene ring was observed in the reaction of benzil with two equivalents of LAl to give the 1,4-aluminacyclohex-2,4-dien 12. In addition, the reaction of L’BCl2 (L = HC[C(Me)NC6F5]2) with one equivalent of benzil in the presence of KC8 gave the corresponding 5-bora-spiro[4.5]heterodecene 13, whereas the hydroboration reaction of butanedione with L’BH2 (14), which was obtained from the reaction of L’BCl2 with L-selectride, failed to give the saturated 5-bora-spiro[4.5]heterodecane. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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14 pages, 4517 KiB  
Article
Stabilization of 2-Pyridyltellurium(II) Derivatives by Oxidorhenium(V) Complexes
by Felipe Dornelles da Silva, Maximilian Roca Jungfer, Adelheid Hagenbach, Ernesto Schulz Lang and Ulrich Abram
Chemistry 2023, 5(2), 934-947; https://doi.org/10.3390/chemistry5020063 - 18 Apr 2023
Viewed by 1167
Abstract
Zwitterionic compounds such as pyridine-containing tellurenyl compounds are interesting building blocks for heterometallic assemblies. They can act as ambiphilic donor/acceptors as is shown by the products of reactions of the zwitterions HpyTeCl2 or HCF3pyTeCl2 with the rhenium(V) complex [ReOCl [...] Read more.
Zwitterionic compounds such as pyridine-containing tellurenyl compounds are interesting building blocks for heterometallic assemblies. They can act as ambiphilic donor/acceptors as is shown by the products of reactions of the zwitterions HpyTeCl2 or HCF3pyTeCl2 with the rhenium(V) complex [ReOCl3(PPh3)2]. The products have a composition of [ReO2Cl(pyTeCl)(PPh3)2] and [ReO2Cl(CF3pyTeCl)(PPh3)2] with central {O=Re=O…Te(Cl)p⏠y}+ units. The Re-O bonds in the products are elongated by approximately 0.1 Å compared with those to the terminal oxido ligands and establish Te…O contacts. Thus, the normally easily assigned concept of oxidation states established at the two metal ions becomes questionable (ReV/TeII vs. ReIII/TeIV). A simple bond length consideration rather leads to a description with the coordination of a mesityltellurenyl(II) chloride unit to an oxido ligand of the Re(V) center, but the oxidation of the tellurium ion and the formation of a tellurinic acid chloride cannot be ruled out completely from an analysis of the solid-state structures. DFT calculations (QTAIM, NBO analysis) give clear support for the formation of a Re(V) dioxide complex donating into an organotellurium(II) chloride and the alternative description can at most be regarded as a less favored resonance structure. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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22 pages, 5871 KiB  
Article
Phosphine Functionalized CpC Ligands and Their Metal Complexes
by Florian Nährig, Yu Sun and Werner R. Thiel
Chemistry 2023, 5(2), 912-933; https://doi.org/10.3390/chemistry5020062 - 18 Apr 2023
Viewed by 1127
Abstract
Simple nucleophilic aliphatic substitution gives access to mono- and diphosphine ligands with a CpC group in the backbone. The monophosphine ligand coordinates to gold(I) via the phosphine site, to thallium(I) via the cyclopentadienyl site and to ruthenium(II) via a combination of both, [...] Read more.
Simple nucleophilic aliphatic substitution gives access to mono- and diphosphine ligands with a CpC group in the backbone. The monophosphine ligand coordinates to gold(I) via the phosphine site, to thallium(I) via the cyclopentadienyl site and to ruthenium(II) via a combination of both, resulting in an ansa-type structure. Coordination with the cyclopentadiene site is not possible for the diphosphine ligand. In this case, monodentate coordination to gold(I) and bidentate coordination to the [PdCl(μ2-Cl)]2, the [Rh(CO)(μ2-Cl)]2, and the Rh(CO)Cl fragment is observed, showing the variability in coordination modes possible for the long-chain diphosphine ligand. Ligands and complexes were characterized by means of NMR and IR spectroscopy, elemental analysis and X-ray structure analysis. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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21 pages, 6573 KiB  
Article
Coinage Metal Complexes Containing Perfluorinated Carboxylates
by Robin Piani, Björn B. Beele, Jörg Rust, Christian W. Lehmann and Fabian Mohr
Chemistry 2023, 5(2), 813-833; https://doi.org/10.3390/chemistry5020058 - 08 Apr 2023
Viewed by 1128
Abstract
A variety of coinage-metal complexes containing perfluorinated carboxylate ligands, together with their structures and thermal behavior, are reported. The silver(I) salts were accessible from the direct reaction of Ag2O with the acids in toluene. Their gold(I) phosphine counterparts formed in high [...] Read more.
A variety of coinage-metal complexes containing perfluorinated carboxylate ligands, together with their structures and thermal behavior, are reported. The silver(I) salts were accessible from the direct reaction of Ag2O with the acids in toluene. Their gold(I) phosphine counterparts formed in high yields by transmetallation using the silver(I) salts. Some structurally unique, mixed-metal (Au,Ag) complexes formed upon combining solutions of the silver(I) salts with the gold(I) phosphine carboxylates. The reduction of dinuclear copper(II) compounds containing perfluorinated carboxylates with triphenylphosphine resulted in the formation of the corresponding copper(I) tris(phosphine) complexes. X-ray structures of representative complexes, together with IR- and TGA data, are reported. Full article
(This article belongs to the Special Issue Commemorating 150 Years of Justus von Liebig’s Legacy)
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