@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{KoleMerzAmaretal.2021,
  author    = {Kole, Goutam Kumar and Merz, Julia and Amar, Anissa and Fontaine, Bruno and Boucekkine, Abdou and Nitsch, J{\"o}rn and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Košćak, Marta and Braunschweig, Holger and Piantanida, Ivo and Halet, Jean-Fran{\c{c}}ois and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.},
  title     = {2- and 2,7-substituted para-N-methylpyridinium pyrenes: syntheses, molecular and electronic structures, photophysical, electrochemical, and spectroelectrochemical properties and binding to double-stranded (ds) DNA},
  series = {Chemistry - A European Journal},
  volume    = {27},
  journal   = {Chemistry - A European Journal},
  number    = {8},
  doi       = {10.1002/chem.202004748},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256642},
  pages     = {2837-2853},
  year      = {2021},
  abstract  = {Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm\(^{-1}\). The N-methylpyridinium compounds have a single reduction at ca. -1.5 V vs. Fc/Fc\(^+\) in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.},
  language  = {en}
}
@article{HattoriMichailSchmiedeletal.2019,
  author    = {Hattori, Yohei and Michail, Evripidis and Schmiedel, Alexander and Moos, Michael and Holzapfel, Marco and Krummenacher, Ivo and Braunschweig, Holger and M{\"u}ller, Ulrich and Pflaum, Jens and Lambert, Christoph},
  title     = {Luminescent Mono-, Di-, and Tri-radicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {68},
  doi       = {10.1002/chem.201903007},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208162},
  pages     = {15463-15471},
  year      = {2019},
  abstract  = {Up to three polychlorinated pyridyldiphenylmethyl radicals bridged by a triphenylamine carrying electron withdrawing (CN), neutral (Me), or donating (OMe) groups were synthesized and analogous radicals bridged by tris(2,6-dimethylphenyl)borane were prepared for comparison. All compounds were as stable as common closed-shell organic compounds and showed significant fluorescence upon excitation. Electronic, magnetic, absorption, and emission properties were examined in detail, and experimental results were interpreted using DFT calculations. Oxidation potentials, absorption and emission energies could be tuned depending on the electron density of the bridges. The triphenylamine bridges mediated intramolecular weak antiferromagnetic interactions between the radical spins, and the energy difference between the high spin and low spin states was determined by temperature dependent ESR spectroscopy and DFT calculations. The fluorescent properties of all radicals were examined in detail and revealed no difference for high and low spin states which facilitates application of these dyes in two-photon absorption spectroscopy and OLED devices.},
  language  = {en}
}
@article{LenczykRoyOberdorfetal.2019,
  author    = {Lenczyk, Carsten and Roy, Dipak Kumar and Oberdorf, Kai and Nitsch, J{\"o}rn and Dewhurst, Rian D. and Radacki, Krzysztof and Halet, Jean-Fran{\c{c}}ois and Marder, Todd B. and Bickelhaupt, Matthias and Braunschweig, Holger},
  title     = {Toward Transition-Metal-Templated Construction of Arylated B\(_{4}\) Chains by Dihydroborane Dehydrocoupling},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {72},
  doi       = {10.1002/chem.201904772},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214324},
  pages     = {16544-16549},
  year      = {2019},
  abstract  = {The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH\(_{2}\)] (Dur=2,3,5,6-Me\(_{4}\)C\(_{6}\)H) and [(Me\(_{3}\)Si)\(_{2}\)NBH\(_{2}\)] led to the formation of bridging borylene complexes of the form [(Cp\(^{*}\)RuH)\(_{2}\)BR] (Cp\(^{*}\)=C\(_{5}\)Me\(_{5}\); 1 a: R=Dur; 1 b: R=N(SiMe\(_{3}\))\(_{2}\)) through oxidative addition of the B-H bonds with concomitant hydrogen liberation. Employing the more electron-deficient dihydroborane [3,5-(CF\(_{3}\))\(_{2}\)-C\(_{6}\)H\(_{3}\)BH\(_{2}\)] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)\(_{4}\)[(Cp\(^{*}\)Ru)\(_{2}\)B\(_{4}\)H\(_{5}\)(3,5-(CF\(_{3}\))\(_{2}\)C\(_{6}\)H\(_{3}\))\(_{4}\)] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido-[1,2(Cp\(^{*}\)Ru)\(_{2}\)(μ-H)B\(_{4}\)H\(_{9}\)] (I) indicates that there appear to be no classical σ-bonds between the boron atoms in complex I, whereas in the case of 4 the B\(_{4}\) chain better resembles a network of three B-B σ bonds, the central bond being significantly weaker than the other two.},
  language  = {en}
}
@article{GoettelGaoDotzaueretal.2020,
  author    = {Goettel, James T. and Gao, Haopeng and Dotzauer, Simon and Braunschweig, Holger},
  title     = {\(^{Me}\)CAAC=N\(^{-}\): A Cyclic (Alkyl)(Amino)Carbene Imino Ligand},
  series = {Chemistry - A European Journal},
  volume    = {26},
  journal   = {Chemistry - A European Journal},
  number    = {5},
  doi       = {10.1002/chem.201904715},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212662},
  pages     = {1136-1143},
  year      = {2020},
  abstract  = {A cyclic (alkyl)(amino)carbene (CAAC) has been shown to react with a covalent azide similar to the Staudinger reaction. The reaction of \(^{Me}\)CAAC with trimethylsilyl azide afforded the N-silylated 2-iminopyrrolidine (\(^{Me}\)CAAC=NSiMe\(_{3}\)), which was fully characterized. This compound undergoes hydrolysis to afford the 2-iminopyrrolidine and trimethylsiloxane which co-crystallize as a hydrogen-bonded adduct. The N-silylated 2-iminopyrrolidine was used to transfer the novel pyrrolidine-2-iminato ligand onto both main-group and transition-metal centers. The reaction of the tetrabromodiborane bis(dimethyl sulfide) adduct with two equivalents of \(^{Me}\)CAAC=NSiMe\(_{3}\) afforded the disubstituted diborane. The reaction of \(^{Me}\)CAAC=NSiMe\(_{3}\) with TiCl\(_{4}\) and CpTiCl\(_{3}\) afforded \(^{Me}\)CAAC=NTiCl\(_{3}\) and \(^{Me}\)CAAC=NTiCl\(_{2}\)Cp, respectively.},
  language  = {en}
}
@article{LenczykRoyNitschetal.2019,
  author    = {Lenczyk, Carsten and Roy, Dipak Kumar and Nitsch, J{\"o}rn and Radacki, Krzysztof and Rauch, Florian and Dewhurst, Rian D. and Bickelhaupt, F. Matthias and Marder, Todd B. and Braunschweig, Holger},
  title     = {Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {59},
  issn      = {1521-3765},
  doi       = {10.1002/chem.201902890},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219537},
  pages     = {13566-13571},
  year      = {2019},
  abstract  = {The steric and electronic properties of aryl substituents in monoaryl borohydrides (Li[ArBH\(_3\)]) and dihydroboranes were systematically varied and their reactions with [Ru(PCy\(_3\))\(_2\)HCl(H\(_2\))] (Cy: cyclohexyl) were studied, resulting in bis(σ)-borane or terminal borylene complexes of ruthenium. These variations allowed for the investigation of the factors involved in the activation of dihydroboranes in the synthesis of terminal borylene complexes. The complexes were studied by multinuclear NMR spectroscopy, mass spectrometry, X-ray diffraction analysis, and density functional theory (DFT) calculations. The experimental and computational results suggest that the ortho-substitution of the aryl groups is necessary for the formation of terminal borylene complexes.},
  language  = {en}
}
@article{Belanger‐ChabotBraunschweig2019,
  author    = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger},
  title     = {Hexahalodiborate Dianions: A New Family of Binary Boron Halides},
  series = {Angewandte Chemie International Edition},
  volume    = {58},
  journal   = {Angewandte Chemie International Edition},
  number    = {40},
  doi       = {10.1002/anie.201906666},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219688},
  pages     = {14270-14274},
  year      = {2019},
  abstract  = {The electron-precise binary boron subhalide species [B\(_2\)X\(_6\)]\(^{2-}\) X=F, Br, I) were synthesized and their structures confirmed by X-ray crystallography. The existence of the previously claimed [B\(_2\)Cl\(_6\)]\(^{2-}\), which had been questioned, was also confirmed by X-ray crystallography. The dianions are isoelectronic to hexahaloethanes, are subhalide analogues of the well-known tetrahaloborate anions (BX\(_4\)\(^-\)), and are rare examples of molecular electron-precise binary boron species beyond B\(_2\)X\(_4\), BX\(_3\), and [BX\(_4\)]\(^-\).},
  language  = {en}
}
@article{SchmidtWernerArrowsmithetal.2020,
  author    = {Schmidt, Uwe and Werner, Luis and Arrowsmith, Merle and Deissenberger, Andrea and Hermann, Alexander and Hofmann, Alexander and Ullrich, Stefan and Mattock, James D. and Vargas, Alfredo and Braunschweig, Holger},
  title     = {trans-Selective Insertional Dihydroboration of a cis-Diborene: Synthesis of Linear sp\(^3\)-sp\(^2\)-sp\(^3\)-Triboranes and Subsequent Cationization},
  series = {Angewandte Chemie International Edition},
  volume    = {59},
  journal   = {Angewandte Chemie International Edition},
  number    = {1},
  doi       = {10.1002/anie.201911645},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208090},
  pages     = {325-329},
  year      = {2020},
  abstract  = {The reaction of aryl- and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3-trans -dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis -1,2-μ-H-3-hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3H4\(^+\) analogues.},
  language  = {en}
}
@article{HermannFantuzziArrowsmithetal.2020,
  author    = {Hermann, Alexander and Fantuzzi, Felipe and Arrowsmith, Merle and Zorn, Theresa and Krummenacher, Ivo and Ritschel, Benedikt and Radacki, Krzysztof and Engels, Bernd and Braunschweig, Holger},
  title     = {Oxidation, Coordination, and Nickel-Mediated Deconstruction of a Highly Electron-Rich Diboron Analogue of 1,3,5-Hexatriene},
  series = {Angewandte Chemie, International Edition},
  volume    = {59},
  journal   = {Angewandte Chemie, International Edition},
  number    = {36},
  doi       = {10.1002/anie.202006131},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240652},
  pages     = {15717-15725},
  year      = {2020},
  abstract  = {The reductive coupling of an N-heterocyclic carbene (NHC) stabilized (dibromo)vinylborane yields a 1,2-divinyl- diborene, which, although isoelectronic to a 1,3,5-triene, displays no extended p conjugation because of twisting of the C\(_2\)B\(_2\)C\(_2\) chain. While this divinyldiborene coordinates to copper(I) and platinum(0) in an η\(^2\)-B\(_2\) and η\(^4\)-C\(_2\)B\(_2\) fashion, respectively, it undergoes a complex rearrangement to an η\(^4\)-1,3-diborete upon complexation with nickel(0).},
  language  = {en}
}
@article{BruecknerHessStennettetal.2021,
  author    = {Br{\"u}ckner, Tobias and Heß, Merlin and Stennett, Tom E. and Rempel, Anna and Braunschweig, Holger},
  title     = {Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond},
  series = {Angewandte Chemie, International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie, International Edition},
  number    = {2},
  doi       = {10.1002/anie.202012101},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240669},
  pages     = {736-741},
  year      = {2021},
  abstract  = {An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit.},
  language  = {en}
}
@article{ZhangRadackiBraunschweigetal.2021,
  author    = {Zhang, Fangyuan and Radacki, Krzysztof and Braunschweig, Holger and Lambert, Christoph and Ravat, Prince},
  title     = {Zinc-[7]helicenocyanine and its discrete π-stacked homochiral Dimer},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  doi       = {10.1002/anie.202109380},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256534},
  pages     = {23656-23660},
  year      = {2021},
  abstract  = {In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×10\(^6\) M\(^{-1}\) and 3.42×107 M\(^{-1}\) in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn\(^{-7}\)HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state.},
  language  = {en}
}
@article{RauchEndresFriedrichetal.2020,
  author    = {Rauch, Florian and Endres, Peter and Friedrich, Alexandra and Sieh, Daniel and H{\"a}hnel, Martin and Krummenacher, Ivo and Braunschweig, Holger and Finze, Maik and Ji, Lei and Marder, Todd B.},
  title     = {An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers},
  series = {Chemistry - A European Journal},
  volume    = {26},
  journal   = {Chemistry - A European Journal},
  number    = {57},
  doi       = {10.1002/chem.202001985},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218345},
  pages     = {12951 -- 12963},
  year      = {2020},
  abstract  = {Using a new divergent approach, conjugated triarylborane dendrimers were synthesized up to the 2nd generation. The synthetic strategy consists of three steps: 1) functionalization, via iridium catalyzed C-H borylation; 2) activation, via fluorination of the generated boronate ester with K[HF\(_{2}\)] or [N(nBu\(_{4}\))][HF\(_{2}\)]; and 3) expansion, via reaction of the trifluoroborate salts with aryl Grignard reagents. The concept was also shown to be viable for a convergent approach. All but one of the conjugated borane dendrimers exhibit multiple, distinct and reversible reduction potentials, making them potentially interesting materials for applications in molecular accumulators. Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. However, the conjugation does not increase further upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane subunits, suggesting a potential application as photonic antennas.},
  language  = {en}
}
@article{CrumbachBachmannFritzeetal.2021,
  author    = {Crumbach, Merian and Bachmann, Jonas and Fritze, Lars and Helbig, Andreas and Krummenacher, Ivo and Braunschweig, Holger and Helten, Holger},
  title     = {Dithiophene-Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {17},
  doi       = {10.1002/anie.202100295},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238996},
  pages     = {9290 -- 9295},
  year      = {2021},
  abstract  = {Access to dithiophene-fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one-electron reduction processes. The weak aromatic character of the novel 1,2,7-azadiborepin ring is demonstrated with in-depth theoretical investigations using nucleus-independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations.},
  language  = {en}
}
@article{NeesKupferHofmannetal.2020,
  author    = {Nees, Samuel and Kupfer, Thomas and Hofmann, Alexander and Braunschweig, Holger},
  title     = {Planar Cyclopenten-4-yl Cations: Highly Delocalized π Aromatics Stabilized by Hyperconjugation},
  series = {Angewandte Chemie International Edition},
  volume    = {59},
  journal   = {Angewandte Chemie International Edition},
  number    = {42},
  doi       = {10.1002/anie.202009644},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218358},
  pages     = {18809 -- 18815},
  year      = {2020},
  abstract  = {Theoretical studies predicted the planar cyclopenten-4-yl cation to be a classical carbocation, and the highest-energy isomer of C\(_{5}\)H\(_{7}\)\(^{+}\). Hence, its existence has not been verified experimentally so far. We were now able to isolate two stable derivatives of the cyclopenten-4-yl cation by reaction of bulky alanes Cp\(^{R}\)AlBr\(_{2}\) with AlBr3. Elucidation of their (electronic) structures by X-ray diffraction and quantum chemistry studies revealed planar geometries and strong hyperconjugation interactions primarily from the C-Al σ bonds to the empty p orbital of the cationic sp\(^{2}\) carbon center. A close inspection of the molecular orbitals (MOs) and of the anisotropy of current (induced) density (ACID), as well as the evaluation of various aromaticity descriptors indicated distinct aromaticity for these cyclopenten-4-yl derivatives, which strongly contrasts the classical description of this system. Here, strong delocalization of π electrons spanning the whole carbocycle has been verified, thus providing rare examples of π aromaticity involving saturated sp\(^{3}\) carbon atoms.},
  language  = {en}
}
@article{BachmannHelbigCrumbachetal.2022,
  author    = {Bachmann, Jonas and Helbig, Andreas and Crumbach, Merian and Krummenacher, Ivo and Braunschweig, Holger and Helten, Holger},
  title     = {Fusion of Aza- and Oxadiborepins with Furans in a Reversible Ring-Opening Process Furnishes Versatile Building Blocks for Extended π-Conjugated Materials},
  series = {Chemistry - A European Journal},
  volume    = {28},
  journal   = {Chemistry - A European Journal},
  number    = {63},
  doi       = {10.1002/chem.202202455},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293926},
  year      = {2022},
  abstract  = {A modular synthesis of both difurooxa- and difuroazadiborepins from a common precursor is demonstrated. Starting from 2,2′-bifuran, after protection of the positions 5 and 5' with bulky silyl groups, formation of the novel polycycles proceeds through opening of the furan rings to a dialkyne and subsequent re-cyclization in the borylation step. The resulting bifuran-fused diborepins show pronounced stability, highly planar tricyclic structures, and intense blue light emission. Deprotection and transformation into dibrominated building blocks that can be incorporated into π-extended materials can be performed in one step. Detailed DFT calculations provide information about the aromaticity of the constituent rings of this polycycle.},
  language  = {en}
}
@article{WitteArrowsmithLamprechtetal.2023,
  author    = {Witte, Robert and Arrowsmith, Merle and Lamprecht, Anna and Schorr, Fabian and Krummenacher, Ivo and Braunschweig, Holger},
  title     = {C-C and C-N Bond Activation, Lewis-Base Coordination and One- and Two-Electron Oxidation at a Linear Aminoborylene},
  series = {Chemistry - A European Journal},
  volume    = {29},
  journal   = {Chemistry - A European Journal},
  number    = {16},
  doi       = {10.1002/chem.202203663},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312491},
  year      = {2023},
  abstract  = {A cyclic alkyl(amino)carbene (CAAC)-stabilized dicoordinate aminoborylene is synthesized by the twofold reduction of a [(CAAC)BCl\(_{2}\)(TMP)] (TMP=2,6-tetramethylpiperidyl) precursor. NMR-spectroscopic, X-ray crystallographic and computational analyses confirm the cumulenic nature of the central C=B=N moiety. Irradiation of [(CAAC)B(TMP)] (2) resulted in an intramolecular C-C bond activation, leading to a doubly-fused C\(_{10}\)BN heterocycle, while the reaction with acetonitrile resulted in an aryl migration from the CAAC to the acetonitrile nitrogen atom, concomitant with tautomerization of the latter to a boron-bound allylamino ligand. One-electron oxidation of 2 with CuX (X=Cl, Br) afforded the corresponding amino(halo)boryl radicals, which were characterized by EPR spectroscopy and DFT calculations. Placing 2 under an atmosphere of CO afforded the tricoordinate (CAAC,CO)-stabilized aminoborylene. Finally, the twofold oxidation of 2 with chalcogens led, in the case of N\(_{2}\)O and sulfur, to the splitting of the B-C\(_{CAAC}\) bond and formation of the 2,4-diamino-1,3,2,4-dichalcogenadiboretanes and CAAC-chalcogen adducts, whereas with selenium a monomeric boraselenone was isolated, which showed some degree of B-Se multiple bonding.},
  language  = {en}
}
@article{KoleKošćakAmaretal.2022,
  author    = {Kole, Goutam Kumar and Košćak, Marta and Amar, Anissa and Majhen, Dragomira and Božinović, Ksenija and Brkljaca, Zlatko and Ferger, Matthias and Michail, Evripidis and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Moos, Michael and Braunschweig, Holger and Boucekkine, Abdou and Lambert, Christoph and Halet, Jean-Fran{\c{c}}ois and Piantanida, Ivo and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.},
  title     = {Methyl Viologens of Bis-(4'-Pyridylethynyl)Arenes - Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology},
  series = {Chemistry - A European Journal},
  volume    = {28},
  journal   = {Chemistry - A European Journal},
  number    = {40},
  doi       = {10.1002/chem.202200753},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287126},
  year      = {2022},
  abstract  = {A series of bis-(4'-pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis-N-methylpyridinium compound showed a larger two-photon absorption cross-section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds-DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene-analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi-faceted features, in combination with its two-photon absorption properties, suggest it to be a promising lead compound for development of novel light-activated theranostic agents.},
  language  = {en}
}
@article{BruecknerRitschelJimenez‐Hallaetal.2023,
  author    = {Br{\"u}ckner, Tobias and Ritschel, Benedikt and Jim{\´e}nez-Halla, J. Oscar C. and Fantuzzi, Felipe and Duwe, Dario and Markl, Christian and Dewhurst, Rian D. and Dietz, Maximilian and Braunschweig, Holger},
  title     = {Metal-Free Intermolecular C-H Borylation of N-Heterocycles at B-B Multiple Bonds},
  series = {Angewandte Chemie International Edition},
  volume    = {62},
  journal   = {Angewandte Chemie International Edition},
  number    = {5},
  doi       = {10.1002/anie.202213284},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312385},
  year      = {2023},
  abstract  = {Carbene-stabilized diborynes of the form LBBL (L=N-heterocyclic carbene (NHC) or cyclic alkyl(amino)carbene (CAAC)) induce rapid, high yielding, intermolecular ortho-C-H borylation at N-heterocycles at room temperature. A simple pyridyldiborene is formed when an NHC-stabilized diboryne is combined with pyridine, while a CAAC-stabilized diboryne leads to activation of two pyridine molecules to give a tricyclic alkylideneborane, which can be forced to undergo a further H-shift resulting in a zwitterionic, doubly benzo-fused 1,3,2,5-diazadiborinine by heating. Use of the extended N-heteroaromatic quinoline leads to a borylmethyleneborane under mild conditions via an unprecedented boron-carbon exchange process.},
  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}
}
@article{HagspielArrowsmithFantuzzietal.2021,
  author    = {Hagspiel, Stephan and Arrowsmith, Merle and Fantuzzi, Felipe and Vargas, Alfredo and Rempel, Anna and Hermann, Alexander and Br{\"u}ckner, Tobias and Braunschweig, Holger},
  title     = {Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {12},
  doi       = {10.1002/anie.202015508},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256432},
  pages     = {6446-6450},
  year      = {2021},
  abstract  = {Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.},
  language  = {en}
}