Refine
Has Fulltext
- yes (50)
Is part of the Bibliography
- yes (50)
Document Type
- Journal article (49)
- Preprint (1)
Keywords
- luminescence (10)
- boranes (8)
- boron (8)
- borylation (7)
- fluorescence (5)
- boronate esters (4)
- cross-coupling (4)
- fluoroarene (4)
- inorganic chemistry (4)
- singlet oxygen (4)
- triarylborane (4)
- boronate (3)
- cell imaging (3)
- chromophore (3)
- density functional calculations (3)
- fluorescent probes (3)
- fluorine (3)
- photophysics (3)
- Boron (2)
- DNA/RNA sensors (2)
- boronic acid (2)
- charge transfer (2)
- homogeneous catalysis (2)
- hydroboration (2)
- lysosome (2)
- phosphorescence (2)
- polycyclic aromatic hydrocarbons (2)
- pyrene (2)
- radical (2)
- redox (2)
- synthetic methods (2)
- theranostics (2)
- two-photon excited fluorescence (2)
- 1,2-additionreaction (1)
- 3-coordinate boron (1)
- 3-coordinate organoboron compounds (1)
- 4-dimethylamino-4′-cyanodiphenylacetylene (1)
- AIE (1)
- Alkyne (1)
- Arylborylene Complexes (1)
- Atomic and molecular interactions with photons (1)
- BSA (1)
- Benzyne (1)
- Boronatester (1)
- Boronsäure (1)
- Borylierung (1)
- B−H activation (1)
- Cyclization (1)
- DNA recognition (1)
- DNA sensing (1)
- DNA/RNA binding (1)
- DPP III enzyme (1)
- Dehydrierende Borylierung (1)
- Diborierung (1)
- Dihydroboranes (1)
- EPR spectroscopy (1)
- Geminaler Bisboronat (1)
- Halogenierung (1)
- Hexadehydro-Diels-Alder (1)
- Hydroborierung (1)
- K-region (1)
- Kreuzkupplung (1)
- Kreuzkupplungen (1)
- Lewis acid (1)
- Lewis acids (1)
- N-heterocyclic carbenes (1)
- N-heterocyclic olefins (1)
- N-methylpyridinium pyrene (1)
- OLED (1)
- Optical spectroscopy (1)
- RNA recognition (1)
- Raman probes (1)
- Ruthenium (1)
- Sonogashira reaction (1)
- TD-DFT (1)
- Wade’s rules (1)
- activated delayes flourescence (1)
- alcohol (1)
- alkyl halides (1)
- anorganic chemistry (1)
- arylmetalate (1)
- bioimaging (1)
- blend (1)
- borafluorenes (1)
- boric acid (1)
- borohydrides (1)
- boroles (1)
- boron heterocycles (1)
- boron reagents (1)
- boronate ester (1)
- boronateesters (1)
- boronates (1)
- borylenes (1)
- carbonyl (1)
- carborane (1)
- catalysis (1)
- chromophores (1)
- circular dichroism (1)
- circular dichrosism (1)
- click CuAAC synthesis (1)
- co-gels (1)
- computational chemistry (1)
- conjugation (1)
- copper (1)
- coupling reactions (1)
- cross‐coupling (1)
- dehydrocoupling (1)
- dehydrogenaticve borylation (1)
- diboration (1)
- donor (1)
- donor-acceptor systems (1)
- dual fluorescence (1)
- electrochemistry (1)
- electron storage (1)
- enediyne (1)
- enyne (1)
- equilibrium (1)
- fluerescence (1)
- fluorescence spectroscopy (1)
- fluorescent probe (1)
- fluoroarenes (1)
- functionalization (1)
- gem-bisboronates (1)
- halogenation (1)
- heavy metals (1)
- heterocycles (1)
- high efficiency (1)
- intersystem crossing (1)
- intersystem crossing (1)
- isomer (1)
- isomerization (1)
- light-emitting-diodes (1)
- low-valent compounds (1)
- luminescent (1)
- metal-free (1)
- methyl viologen (1)
- molecular modelling (1)
- molecular structures (1)
- near-IR chromophores (1)
- nickel (1)
- non-radiative decay (1)
- nucleic acid (1)
- optical materials (1)
- organic light-emitting diodes (1)
- organic synthesis (1)
- organocatalytic (1)
- orthogonal self-assembly (1)
- orylation (1)
- palladium-catalyzed (1)
- pericyclic reaction (1)
- phosphorescene spectra (1)
- photodynamic therapy (1)
- photophysical prosperties (1)
- pi-conjugation (1)
- polycyclic aromatic hydrocarbon (1)
- polymer matrix (1)
- probes (1)
- protein sensing (1)
- pyrenes (1)
- pyridinium (1)
- reaction mechanism (1)
- room-temperature phosphorescence (RTP) (1)
- ruthenium (1)
- sensors (1)
- sigma boranes (1)
- single photon (1)
- stereoselective (1)
- steric effects (1)
- structure elucidation (1)
- supramolecular chemistry (1)
- synthesis (1)
- synthesis design (1)
- tetramers (1)
- threecoordinate boron (1)
- transient absorption (1)
- transition metal (1)
- transition metal-free (1)
- triarylamine (1)
- triarylboranes (1)
- triplet (1)
- trivalent boron (1)
- two-photon absorption (1)
- ultrafast Raman loss spectroscopy (1)
- viologens (1)
- weak intermolecular coordination (1)
Institute
EU-Project number / Contract (GA) number
- 669054 (1)
Phenylpyridyl-fused boroles [TipPBB1]\(_4\) and TipPBB2 were synthesized and their properties investigated. [TipPBB1]\(_4\) forms a tetramer in both the solid state and solution. TipPBB2 contains a 4-coordinate boron atom in the solid state but dissociates to give a 3-coordinate boron species in solution. TipPBB2 shows interesting temperature-dependent dual fluorescence in solution because of the equilibrium between 3- and 4-coordinate boron species due to weak N⋅⋅⋅B intermolecular coordination.
Persistent room-temperature phosphorence from purely organic molecules and multi-component systems
(2021)
Recently, luminophores showing efficient room-temperature phosphorescence (RTP) have gained tremendous interest due to their numerous applications. However, most phosphors are derived from transition metal complexes because of their intrinsic fast intersystem crossing (ISC) induced by strong spin–orbit coupling (SOC) constants of the heavy metal.
Metal-free RTP materials are rare and have become a promising field because they are inexpensive and environmentally friendly. This review summarizes organic molecular materials with long triplet lifetimes at room temperature from the perspective of whether they stem from a molecular or multi-component system. Among purely organic phosphors, heteroatoms are usually introduced into the backbone in order to boost the singlet–triplet ISC rate constant.
In multi-component systems, useful strategies such as host–guest, polymer matrix, copolymerization, and supramolecular assembly provide a rigid matrix to restrict nonradiative pathways thus realizing ultralong RTP.
The 2- and 2,7- substituted para-N-methylpyridinium pyrene cations show high-affinity intercalation into ds-DNAs, whereas their non-methylated analogues interacted with ds-DNA/RNA only in the protonated form (at pH 5), but not at physiological conditions (pH 7). The fluorescence from non-methylated analogues was strongly dependent on the protonation of the pyridines; consequently, they act as fluorescence ratiometric probes for simultaneous detection of both ds-DNA and BSA at pH 5, relying on the ratio between intensities at 420 nm (BSA specific) and 520 nm (DNA specific), whereby exclusively ds-DNA sensing could be switched-off by adjustment to pH 7. Only methylated, permanently charged pyrenes show photoinduced cleavage of circular DNA, attributed to pyrene-mediated irradiation-induced production of singlet oxygen. Consequently, the moderate toxicity of these cations against human cell lines is strongly increased upon irradiation. Detailed studies revealed increased total ROS production in cells treated by the compounds studied, accompanied by cell swelling and augmentation of cellular complexity. The most photo-active 2-para-N-methylpyridinium pyrene showed significant localization at mitochondria, its photo-bioactivity likely due to mitochondrial DNA damage. Other derivatives were mostly non-selectively distributed between various cytoplasmic organelles, thus being less photoactive.
A nickel/N-heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B\(_{2}\)(neop)\(_{2}\) (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron-deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni-catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4-(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans-[Ni(ICy)\(_{2}\)(4-CF\(_{3}\)-C\(_{6}\)H\(_{4}\)){(SO)-4-MeO-C\(_{6}\)H\(_{4}\)}] 4. For complex 5, the isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I is in equilibrium with the S-bonded isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(SOC\(_{6}\)H\(_{5}\))] 5, as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2-TZVP-level of theory) and connected via a transition state trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(η\(^{2}\)-{SO}-C\(_{6}\)H\(_{5}\))], which lies only 10.8 kcal/mol above 5.
In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts.
N‐heterocyclic olefins (NHOs), relatives of N‐heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π‐electron donating ability, NHOs were attached to triarylborane π‐acceptors (A) giving donor (D)–π–A compounds 1–3. In addition, an enamine π‐donor analogue (4) was synthesized for comparison. UV–visible absorption studies show a larger red shift for the NHO‐containing boranes than for the enamine analogue, a relative of cyclic (alkyl)(amino) carbenes (CAACs). Solvent‐dependent emission studies indicate that 1–4 have moderate intramolecular charge‐transfer (ICT) behavior. Electrochemical investigations reveal that the NHO‐containing boranes have extremely low reversible oxidation potentials (e.g., for 3, \(E^{ox}_{1/2}\) =−0.40 V vs. ferrocene/ferrocenium, Fc/Fc\(^+\), in THF). Time‐dependent (TD) DFT calculations show that the HOMOs of 1–3 are much more destabilized than that of the enamine‐containing 4, which confirms the stronger donating ability of NHOs.
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.
With the rapid development of the hexadehydro‐Diels‐Alder reaction (HDDA) from its first discovery in 1997, the question of whether a concerted or stepwise mechanism better describes the thermally activated formation of ortho‐benzyne from a diyne and a diynophile has been debated. Mechanistic and kinetic investigations were able to show that this is not a black or white situation, as minor changes can tip the balance. For that reason, especially, linked yne‐diynes were studied to examine steric, electronic, and radical‐stabilizing effects of their terminal substituents on the reaction mechanism and kinetics. Furthermore, the influence of the nature of the linker on the HDDA reaction was explored. The more recently discovered photochemical HDDA reaction also gives ortho‐arynes, which display the same reactivity as the thermally generated ones, but their formation might not proceed by the same mechanism. This minireview summarizes the current state of mechanistic understanding of the HDDA reaction.
Wir berichten über die katalytische Triborierung terminaler Alkine mit B\(_2\)pin\(_2\) (Bis‐(pinakolato)‐dibor) unter Verwendung von einfach zugänglichem Cu(OAc)\(_2\) und P\(^n\)Bu\(_3\). Verschiedene 1,1,2‐Triborylalkene, eine Verbindungsklasse mit potentieller Funktion als Matrix‐Metallo‐Proteinase(MMP‐2)‐Inhibitor, werden direkt in mäßigen bis guten Ausbeuten erhalten. Das Verfahren zeichnet sich durch milde Reaktionsbedingungen, ein breites Substratspektrum und eine gute Verträglichkeit gegenüber funktionellen Gruppen aus. Diese Cu‐katalysierte Reaktion kann im Gramm‐Maßstab durchgeführt werden und liefert die entsprechenden 1,1,2‐Triborylalkene in mäßigen Ausbeuten. Die Verwendung solcher Verbindungen wird anhand weiterer Transformationen der C−B‐Bindungen zur Darstellung eines geminalen Dihalogenborylalkens (F, Cl, Br), eines Monohalogendiborylalkens (Cl, Br) und eines trans‐Diaryldiborylalkens demonstriert, welche bedeutende Synthesebausteine darstellen und bisher nur schwer zugänglich waren.
Eine effiziente, einstufige Synthese von 1,1,1‐Trialkylalkanen durch die sequenzielle, dehydrierende Borylierung und zweifache Hydroborierung von terminalen Alkinen mit Pinakolboran (HBpin) wurde unter Verwendung des kostengünstigen und einfach zugänglichen Kupfersalzes Cu(OAc)2 als Katalysator realisiert. Das Verfahren zeichnet sich durch ein breites Substratspektrum, eine außerordentliche Selektivität und eine hohe Toleranz gegenüber funktionellen Gruppen aus. Zudem kann die Reaktion ohne Ausbeuteverlust im Gramm‐Maßstab durchgeführt werden. Die somit erhaltenen 1,1,1‐Trialkylalkane können Anwendungen in der Herstellung von synthetisch wertvollen und bislang schwer zugänglichen α‐Vinylboronaten und zyklischen Boryl‐Verbindungen finden. Verschiedene Alkylgruppen können stufenweise über eine basenvermittelte deborylierende Alkylierung eingeführt werden, um racemische, tertiäre Alkylboronate herzustellen, die einfach in nützliche tertiäre Alkohole umgewandelt werden können.