Refine
Has Fulltext
- yes (105)
Is part of the Bibliography
- yes (105)
Year of publication
Document Type
- Journal article (75)
- Preprint (30)
Language
- English (105) (remove)
Keywords
- boron (46)
- diborenes (15)
- Boron (11)
- carbenes (9)
- inorganic chemistry (8)
- density functional calculations (6)
- diborynes (6)
- aromaticity (5)
- heterocycles (5)
- N-heterocyclic carbenes (4)
- borylene (4)
- diborane (4)
- diboranes (4)
- diborene (4)
- luminescence (4)
- radical (4)
- structure elucidation (4)
- Bor (3)
- Diborane (3)
- Multiple bonds (3)
- bond activation (3)
- boranes (3)
- borylation (3)
- borylenes (3)
- fluorescence (3)
- hydroboration (3)
- low-valent compounds (3)
- multiple bonds (3)
- radicals (3)
- singlet oxygen (3)
- small-molecule activation (3)
- Anorganische Chemie (2)
- Aromaticity (2)
- BN compounds (2)
- Biradicals (2)
- Borylene (2)
- Cycloaddition (2)
- DFT (2)
- DFT calculations (2)
- EDA-NOCV (2)
- Heterocycles (2)
- Main-group chemistry (2)
- bonding (2)
- carbene ligands (2)
- chemical bonding (2)
- computational chemistry (2)
- conjugation (2)
- crystal structure (2)
- cycloaddition (2)
- diazadiborinines (2)
- diboration (2)
- diradicals (2)
- hydrogenation (2)
- low-valent main group chemistry (2)
- main group elements (2)
- main-group chemistry (2)
- multiple bonding (2)
- one-electron oxidation (2)
- oxidative addition (2)
- platinum (2)
- polycycles (2)
- redox (2)
- ring expansion (2)
- single-crystal X-ray study (2)
- transition metal complex (2)
- two-photon absorption (2)
- 1,2-additions (1)
- 1,2-azaborinine (1)
- 1,4-Diborabenzene (1)
- ACID (1)
- Acene (1)
- Arylborylene Complexes (1)
- B,N-heterocycles (1)
- B,N-heterocylcles (1)
- B-B bond (1)
- B-B bond activation (1)
- Beryllium (1)
- Bindungsaktivierung (1)
- Biradikale (1)
- Boranes (1)
- Borylation (1)
- B−H activation (1)
- C-H activation (1)
- CH activation (1)
- CO activation (1)
- CO2 fixation (1)
- Carbene (1)
- Chemie (1)
- DFT mechanism (1)
- DNA/RNA binding (1)
- DNA/RNA sensors (1)
- Diboranes (1)
- Diborene (1)
- Diboryne (1)
- Dihydroboranes (1)
- EPR spectroscopy (1)
- Heterocyclen (1)
- Heterocyclische Verbindungen (1)
- Hydroarylation (1)
- K-region (1)
- Kristallographie (1)
- Lewis acidity (1)
- Lewis acids (1)
- Lewis adducts (1)
- Lewis-base adducts (1)
- Metallocene (1)
- Metallocenes (1)
- Multiple bonding (1)
- N ligands (1)
- N-functionalization (1)
- N-heterocyclic olefins (1)
- NHCs (1)
- NIR OLED (1)
- NMR spectroscopy (1)
- OLEDs (1)
- Organoboron chemistry (1)
- Palladium-catalyzed silaboration (1)
- Parent Piano-Stool Complex (1)
- Pnictogen reduction (1)
- R factor = 0.018 (1)
- R factor = 0.027 (1)
- Ruthenium (1)
- Selen (1)
- Selenium (1)
- T = 100 K (1)
- T = 174 K (1)
- Tellur (1)
- Tellurium (1)
- Tetrafluorodiborane (1)
- Titanium (1)
- Transition metals (1)
- Wade’s rules (1)
- X-ray crystallography (1)
- \(\pi\) interactions (1)
- ab initio calculations (1)
- acenes (1)
- acetone (1)
- alkenes (1)
- alkylideneborane (1)
- alkynes (1)
- amine borane dehydrocoupling (1)
- anionic dimetalloborylene complexes (1)
- antiaromaticity (1)
- azaborinines (1)
- azaborole (1)
- azadiboretidines (1)
- azobenzenes (1)
- beryllium (1)
- binary species (1)
- bioimaging (1)
- biradicals (1)
- bismuth (1)
- bond Activation (1)
- bond dissociation energies (1)
- bond theory (1)
- borafluorenes (1)
- boraselenone (1)
- borohydrides (1)
- boroles (1)
- boron chains (1)
- boron tetraiodide (1)
- boron-bound hydrogen (1)
- boronate (1)
- boronic acid (1)
- boronium cations (1)
- boryl anion (1)
- borylene complexes (1)
- carbene (1)
- carbene donor (1)
- carbocations (1)
- carbon dioxide (1)
- carborane (1)
- catalysis (1)
- catenation (1)
- cationic species (1)
- cations (1)
- cell imaging (1)
- chain structures (1)
- chalcogens (1)
- charge transfer (1)
- chelates (1)
- chemistry (1)
- chirality (1)
- chromism (1)
- chromophores (1)
- circularly polarized luminescence (1)
- complexes (1)
- conjugated oligomers (1)
- crystal-structure (1)
- crystallographic analyses (1)
- crystallography (1)
- cumulene (1)
- cyclic (alkyl)(amino)carbene (1)
- cyclic alkyl(amino)carbene (1)
- cyclization (1)
- cyclopenten-4-yl cation (1)
- data-to-parameter ratio = 22.3 (1)
- data-to-parameter ratio = 23.6. (1)
- decarbonylation (1)
- dehydrocoupling (1)
- density functional theory (1)
- density-functional calculations (1)
- design (1)
- desymmetrization (1)
- diboraindanes (1)
- diborane(6) (1)
- diboron (1)
- diboryne (1)
- dicoordinate borylene (1)
- dilaboration (1)
- donor-acceptor systems (1)
- dual fluorescence (1)
- electrochemistry (1)
- electrolytes (1)
- electron donors (1)
- electron storage (1)
- electron-precise diborates (1)
- electrophiles (1)
- electrophilic substitution (1)
- enamines (1)
- equilibrium (1)
- erovalent diboron compounds (1)
- fluorescent probes (1)
- furan (1)
- fused thiazaboroles (1)
- group 13 (1)
- group 8 metals (1)
- half-sandwich complexes (1)
- halides (1)
- halogens (1)
- helicene (1)
- helicenes (1)
- heterodinuclear compound (1)
- homochiral dimer (1)
- hybrid materials (1)
- hydroamination (1)
- hydroarylation (1)
- hydrogen (1)
- hyperconjugation (1)
- imide ligands (1)
- iminoboranes (1)
- insertion (1)
- intersystem crossing (1)
- iodine (1)
- isoelectronic analogues (1)
- isomer (1)
- isomerization (1)
- isomers (1)
- ketenes (1)
- ligand exchange (1)
- ligands (1)
- low-valent main-group species (1)
- luminescent (1)
- mean σ(C–C) = 0.004 Å (1)
- mechanism (1)
- metal borylene complexes (1)
- metal-free (1)
- metallaboranes (1)
- metallacycles (1)
- metathesis (1)
- methyl exchange (1)
- methyl viologen (1)
- molecular-structure (1)
- naphthyridine (1)
- near-IR chromophores (1)
- nitrogen heterocycles (1)
- nitrogen ligands (1)
- nitrogen trichloride (1)
- nucleic acid (1)
- nucleophile (1)
- nucleophilic addition (1)
- nucleophilic substitution (1)
- oligomerization (1)
- organic chemistry (1)
- organometallic chemistry (1)
- orylation (1)
- oxidation (1)
- palladium (1)
- pericyclic reaction (1)
- phosphorus (1)
- phosphorus heterocycles (1)
- photoelectron spectroscopy (1)
- photoisomerization (1)
- photolysis (1)
- photophysical prosperties (1)
- phthalocyanines (1)
- pi-conjugation (1)
- pincer ligand (1)
- polycyclic aromatic hydrocarbon (1)
- polycyclic aromatic hydrocarbons (1)
- potassium reagent (1)
- push-pull stabilization (1)
- pyrenes (1)
- pyridinium (1)
- reaction mechanism (1)
- reaction mechanisms (1)
- reactive intermediates (1)
- rearrangement (1)
- rearrangements (1)
- redox processes (1)
- redox reactions (1)
- reduction (1)
- reductive coupling (1)
- ring-expansion reactions (1)
- ruthenium (1)
- s-block metals (1)
- salt metathesis (1)
- sigma boranes (1)
- silaboration (1)
- silylenes (1)
- small HOMO-LUMO gap (1)
- solid-state NMR (1)
- solid-state sturcture (1)
- spectroscopy (1)
- spin distribution (1)
- spiroborates (1)
- steric effects (1)
- strained molecules (1)
- structural analysis (1)
- supramolecular assembly (1)
- synchrotron radiation (1)
- synthesis (1)
- synthetic methods (1)
- terminal alkynes (1)
- tetramers (1)
- tetrametallaborides (1)
- tetraorganoborate salt (1)
- theranostics (1)
- thermal rearrangement (1)
- thiophene (1)
- threecoordinate boron (1)
- titanium (1)
- transfer hydrogenation (1)
- transition metal (1)
- transition metals (1)
- triarylamine (1)
- triarylborane (1)
- triarylboranes (1)
- triboranes (1)
- trimetallaborides (1)
- triple bonds (1)
- viologens (1)
- wR factor = 0.038 (1)
- wR factor = 0.069 (1)
- weak intermolecular coordination (1)
- π aromaticity (1)
- π-extension (1)
Institute
Sonstige beteiligte Institutionen
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.
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.
Dithiophene‐Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics
(2021)
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.
Planar Cyclopenten‐4‐yl Cations: Highly Delocalized π Aromatics Stabilized by Hyperconjugation
(2020)
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.
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.
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.
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.
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.
cAAC‐Stabilized 9,10‐diboraanthracenes—Acenes with Open‐Shell Singlet Biradical Ground States
(2020)
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.
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.