@article{WeiserCuiDewhurstetal.2023, author = {Weiser, Jonas and Cui, Jingjing and Dewhurst, Rian D. and Braunschweig, Holger and Engels, Bernd and Fantuzzi, Felipe}, title = {Structure and bonding of proximity-enforced main-group dimers stabilized by a rigid naphthyridine diimine ligand}, series = {Journal of Computational Chemistry}, volume = {44}, journal = {Journal of Computational Chemistry}, number = {3}, doi = {10.1002/jcc.26994}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312586}, pages = {456 -- 467}, year = {2023}, abstract = {The development of ligands capable of effectively stabilizing highly reactive main-group species has led to the experimental realization of a variety of systems with fascinating properties. In this work, we computationally investigate the electronic, structural, energetic, and bonding features of proximity-enforced group 13-15 homodimers stabilized by a rigid expanded pincer ligand based on the 1,8-naphthyridine (napy) core. We show that the redox-active naphthyridine diimine (NDI) ligand enables a wide variety of structural motifs and element-element interaction modes, the latter ranging from isolated, element-centered lone pairs (e.g., E = Si, Ge) to cases where through-space π bonds (E = Pb), element-element multiple bonds (E = P, As) and biradical ground states (E = N) are observed. Our results hint at the feasibility of NDI-E2 species as viable synthetic targets, highlighting the versatility and potential applications of napy-based ligands in main-group chemistry.}, language = {en} } @article{MuellerMetaMeidneretal.2023, author = {M{\"u}ller, Patrick and Meta, Mergim and Meidner, Jan Laurenz and Schwickert, Marvin and Meyr, Jessica and Schwickert, Kevin and Kersten, Christian and Zimmer, Collin and Hammerschmidt, Stefan Josef and Frey, Ariane and Lahu, Albin and de la Hoz-Rodr{\´i}guez, Sergio and Agost-Beltr{\´a}n, Laura and Rodr{\´i}guez, Santiago and Diemer, Kira and Neumann, Wilhelm and Gonz{\`a}lez, Florenci V. and Engels, Bernd and Schirmeister, Tanja}, title = {Investigation of the compatibility between warheads and peptidomimetic sequences of protease inhibitors — a comprehensive reactivity and selectivity study}, series = {International Journal of Molecular Sciences}, volume = {24}, journal = {International Journal of Molecular Sciences}, number = {8}, issn = {1422-0067}, doi = {10.3390/ijms24087226}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-313596}, year = {2023}, abstract = {Covalent peptidomimetic protease inhibitors have gained a lot of attention in drug development in recent years. They are designed to covalently bind the catalytically active amino acids through electrophilic groups called warheads. Covalent inhibition has an advantage in terms of pharmacodynamic properties but can also bear toxicity risks due to non-selective off-target protein binding. Therefore, the right combination of a reactive warhead with a well-suited peptidomimetic sequence is of great importance. Herein, the selectivities of well-known warheads combined with peptidomimetic sequences suited for five different proteases were investigated, highlighting the impact of both structure parts (warhead and peptidomimetic sequence) for affinity and selectivity. Molecular docking gave insights into the predicted binding modes of the inhibitors inside the binding pockets of the different enzymes. Moreover, the warheads were investigated by NMR and LC-MS reactivity assays against serine/threonine and cysteine nucleophile models, as well as by quantum mechanics simulations.}, language = {en} } @article{FranzsicoFantuzziCardozoetal.2021, author = {Franzsico, Marcos A. S. and Fantuzzi, Felipe and Cardozo, Thiago M. and Esteves, Pierre M. and Engels, Bernd and Oliveira, Ricardo R.}, title = {Taming the Antiferromagnetic Beast: Computational Design of Ultrashort Mn-Mn Bonds Stabilized by N-Heterocyclic Carbenes}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {47}, doi = {10.1002/chem.202101116}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256874}, pages = {12126-12136}, year = {2021}, abstract = {The development of complexes featuring low-valent, multiply bonded metal centers is an exciting field with several potential applications. In this work, we describe the design principles and extensive computational investigation of new organometallic platforms featuring the elusive manganese-manganese bond stabilized by experimentally realized N-heterocyclic carbenes (NHCs). By using DFT computations benchmarked against multireference calculations, as well as MO- and VB-based bonding analyses, we could disentangle the various electronic and structural effects contributing to the thermodynamic and kinetic stability, as well as the experimental feasibility, of the systems. In particular, we explored the nature of the metal-carbene interaction and the role of the ancillary η\(^{6}\) coordination to the generation of Mn\(_{2}\) systems featuring ultrashort metal-metal bonds, closed-shell singlet multiplicities, and positive adiabatic singlet-triplet gaps. Our analysis identifies two distinct classes of viable synthetic targets, whose electrostructural properties are thoroughly investigated.}, language = {en} } @article{BruecknerFantuzziStennettetal.2021, author = {Br{\"u}ckner, Tobias and Fantuzzi, Felipe and Stennett, Tom E. and Krummenacher, Ivo and Dewhurst, Rian D. and Engels, Bernd and Braunschweig, Holger}, title = {Isolation of neutral, mono-, and dicationic B\(_2\)P\(_2\) rings by diphosphorus addition to a boron-boron triple bond}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {24}, doi = {10.1002/anie.202102218}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256451}, pages = {13661-13665}, year = {2021}, abstract = {The NHC-stabilised diboryne (B\(_2\)(SIDep)\(_2\); SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B\(_2\)P\(_2\) heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B\(_2\)P\(_2\) rings, with their diradicaloid, planar-ring isomers lying close in energy.}, language = {en} } @article{SchmidtFantuzziKlopfetal.2021, author = {Schmidt, Paul and Fantuzzi, Felipe and Klopf, Jonas and Schr{\"o}der, Niklas B. and Dewhurst, Rian D. and Braunschweig, Holger and Engel, Volker and Engels, Bernd}, title = {Twisting versus delocalization in CAAC- and NHC-stabilized boron-based biradicals: the roles of sterics and electronics}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {16}, doi = {10.1002/chem.202004619}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256636}, pages = {5160-5170}, year = {2021}, abstract = {Twisted boron-based biradicals featuring unsaturated C\(_2\)R\(_2\) (R=Et, Me) bridges and stabilization by cyclic (alkyl)(amino)carbenes (CAACs) were recently prepared. These species show remarkable geometrical and electronic differences with respect to their unbridged counterparts. Herein, a thorough computational investigation on the origin of their distinct electrostructural properties is performed. It is shown that steric effects are mostly responsible for the preference for twisted over planar structures. The ground-state multiplicity of the twisted structure is modulated by the σ framework of the bridge, and different R groups lead to distinct multiplicities. In line with the experimental data, a planar structure driven by delocalization effects is observed as global minimum for R=H. The synthetic elusiveness of C\(_2\)R\(_2\)-bridged systems featuring N-heterocyclic carbenes (NHCs) was also investigated. These results could contribute to the engineering of novel main group biradicals.}, language = {en} } @article{RoyTroesterFantuzzietal.2021, author = {Roy, Dipak Kumar and Tr{\"o}ster, Tobias and Fantuzzi, Felipe and Dewhurst, Rian D. and Lenczyk, Carsten and Radacki, Krzysztof and Pranckevicius, Conor and Engels, Bernd and Braunschweig, Holger}, title = {Isolation and Reactivity of an Antiaromatic s-Block Metal Compound}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {7}, doi = {10.1002/anie.202014557}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224447}, pages = {3812 -- 3819}, year = {2021}, abstract = {The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation-state flexibility of the s-block metals has long stood in the way of their participation in sophisticated π-bonding arrangements, and truly antiaromatic systems containing s-block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis-base-coordination chemistry.}, language = {en} } @article{RamlerFantuzziGeistetal.2021, author = {Ramler, Jaqueline and Fantuzzi, Felipe and Geist, Felix and Hanft, Anna and Braunschweig, Holger and Engels, Bernd and Lichtenberg, Crispin}, title = {The dimethylbismuth cation: entry into dative Bi-Bi bonding and unconventional methyl exchange}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202109545}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256543}, pages = {24388-24394}, year = {2021}, abstract = {The dimethyl bismuth cation, [BiMe\(_2\)(SbF\(_6\))], has been isolated and characterized. Reaction with BiMe\(_3\) allows access to the first compound featuring Bi→Bi donor-acceptor bonding. In solution, dynamic behavior with methyl exchange via an unusual S\(_E\)2 mechanism is observed, underlining the unique properties of bismuth species as soft Lewis acids with the ability to undergo reversible Bi-C bond cleavage.}, language = {en} } @article{MukhopadhyaySchleierWirsingetal.2020, author = {Mukhopadhyay, Deb Pratim and Schleier, Domenik and Wirsing, Sara and Ramler, Jaqueline and Kaiser, Dustin and Reusch, Engelbert and Hemberger, Patrick and Preitschopf, Tobias and Krummenacher, Ivo and Engels, Bernd and Fischer, Ingo and Lichtenberg, Crispin}, title = {Methylbismuth: an organometallic bismuthinidene biradical}, series = {Chemical Science}, volume = {11}, journal = {Chemical Science}, number = {29}, doi = {10.1039/D0SC02410D}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-251657}, pages = {7562-7568}, year = {2020}, abstract = {We report the generation, spectroscopic characterization, and computational analysis of the first free (non-stabilized) organometallic bismuthinidene, BiMe. The title compound was generated in situ from BiMe\(_3\) by controlled homolytic Bi-C bond cleavage in the gas phase. Its electronic structure was characterized by a combination of photoion mass-selected threshold photoelectron spectroscopy and DFT as well as multi-reference computations. A triplet ground state was identified and an ionization energy (IE) of 7.88 eV was experimentally determined. Methyl abstraction from BiMe\(_3\) to give [BiMe(_2\)]• is a key step in the generation of BiMe. We reaveal a bond dissociation energy of 210 ± 7 kJ mol\(^{-1}\), which is substantially higher than the previously accepted value. Nevertheless, the homolytic cleavage of Me-BiMe\(_2\) bonds could be achieved at moderate temperatures (60-120 °C) in the condensed phase, suggesting that [BiMe\(_2\)]• and BiMe are accessible as reactive intermediates under these conditions.}, subject = {Photoelektronenspektroskopie}, language = {en} } @unpublished{SchmidtFantuzziArrowsmithetal.2020, author = {Schmidt, Uwe and Fantuzzi, Felipe and Arrowsmith, Merle and Hermann, Alexander and Prieschl, Dominic and Rempel, Anna and Engels, Bernd and Braunschweig, Holger}, title = {Tuneable reduction of cymantrenylboranes to diborenes or borylene-derived boratafulvenes}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/D0CC06398C}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222149}, year = {2020}, abstract = {Whereas the reduction of N-heterocyclic carbene (NHC)-stabilised cymantrenyldibromoboranes, (NHC)BBr\(_2\)Cym, in benzene results in formation of the corresponding diborenes (NHC)\(_2\)B\(_2\)Cym\(_2\), a change of solvent to THF yields a borylene of the form (NHC)\(_2\)BCym, stabilised through its boratafulvene resonance form.}, language = {en} } @article{SaalfrankFantuzziKupferetal.2020, author = {Saalfrank, Christian and Fantuzzi, Felipe and Kupfer, Thomas and Ritschel, Benedikt and Hammond, Kai and Krummenacher, Ivo and Bertermann, R{\"u}diger and Wirthensohn, Raphael and Finze, Maik and Schmid, Paul and Engel, Volker and Engels, Bernd and Braunschweig, Holger}, title = {cAAC-Stabilized 9,10-diboraanthracenes—Acenes with Open-Shell Singlet Biradical Ground States}, series = {Angewandte Chemie International Edition}, volume = {59}, journal = {Angewandte Chemie International Edition}, number = {43}, doi = {10.1002/anie.202008206}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217795}, pages = {19338 -- 19343}, year = {2020}, abstract = {Narrow HOMO-LUMO gaps and high charge-carrier mobilities make larger acenes potentially high-efficient materials for organic electronic applications. The performance of such molecules was shown to significantly increase with increasing number of fused benzene rings. Bulk quantities, however, can only be obtained reliably for acenes up to heptacene. Theoretically, (oligo)acenes and (poly)acenes are predicted to have open-shell singlet biradical and polyradical ground states, respectively, for which experimental evidence is still scarce. We have now been able to dramatically lower the HOMO-LUMO gap of acenes without the necessity of unfavorable elongation of their conjugated π system, by incorporating two boron atoms into the anthracene skeleton. Stabilizing the boron centers with cyclic (alkyl)(amino)carbenes gives neutral 9,10-diboraanthracenes, which are shown to feature disjointed, open-shell singlet biradical ground states.}, language = {en} }