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Keywords = polycyclic heteroaromatic hydrocarbons

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18 pages, 10785 KB  
Article
Divergent Synthesis of 5,7-Diazaullazines Derivatives through a Combination of Cycloisomerization with Povarov or Alkyne–Carbonyl Metathesis
by Jonas Polkaehn, Peter Ehlers, Alexander Villinger and Peter Langer
Molecules 2024, 29(9), 2159; https://doi.org/10.3390/molecules29092159 - 6 May 2024
Cited by 2 | Viewed by 1723
Abstract
Ullazines and their π-expanded derivatives have gained much attention as active components in various applications, such as in organic photovoltaic cells or as photosensitizers for CO2 photoreduction. Here, we report the divergent synthesis of functionalized diazaullazines by means of two different domino-reactions [...] Read more.
Ullazines and their π-expanded derivatives have gained much attention as active components in various applications, such as in organic photovoltaic cells or as photosensitizers for CO2 photoreduction. Here, we report the divergent synthesis of functionalized diazaullazines by means of two different domino-reactions consisting of either a Povarov/cycloisomerization or alkyne–carbonyl metathesis/cycloisomerization protocol. The corresponding quinolino-diazaullazine and benzoyl-diazaullazine derivatives were obtained in moderate to good yields. Their optical and electronic properties were studied and compared to related, literature-known compounds to obtain insights into the impact of nitrogen doping and π-expansion. Full article
(This article belongs to the Section Organic Chemistry)
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20 pages, 5484 KB  
Article
Complexation of Boron and Aluminum with a Bidentate Hydroxy-BN-naphthalene Ligand
by Yannik Appiarius, Pim Puylaert, Julius Werthschütz, Tim Neudecker and Anne Staubitz
Inorganics 2023, 11(7), 295; https://doi.org/10.3390/inorganics11070295 - 12 Jul 2023
Cited by 1 | Viewed by 2969
Abstract
The isoelectronic relationship of 1,2-azaborinine (B=N structural motif) and benzene (C=C) is well documented. Upon deprotonation of the former, the anionic 1,2-azaboratabenzene is obtained, which is isosteric with pyridine (C=N) and has a similar capability as an aromatic N-donor. We present the [...] Read more.
The isoelectronic relationship of 1,2-azaborinine (B=N structural motif) and benzene (C=C) is well documented. Upon deprotonation of the former, the anionic 1,2-azaboratabenzene is obtained, which is isosteric with pyridine (C=N) and has a similar capability as an aromatic N-donor. We present the complexation of boron and aluminum precursors with a κ2-N,O-donating 8-hydroxy-BN-naphthalene ligand (H2(BQ), 1). Six chelate complexes with 1:1 and 2:1 stoichiometries were isolated and characterized by X-ray diffraction analysis and NMR spectroscopy. Comparing the isosteric dimethylaluminum complexes of H2(BQ) and an 8-hydroxyquinoline (HQ’, 2) as a reference allowed us to quantify the influence of a formal substitution of carbon by boron on the structure and the electronic properties: While the structural parameters of the ligands were similar, the electropositive boron atom affected the electron density distributions within the complexes substantially. As the consequence, the Al–N bond was significantly shortened, and the aluminum atom showed a different coordination geometry than in the quinoline analog. Moreover, strong hypsochromic shifts of both the absorption and the emission were observed. The results highlight that the differences between CN and BN polyaromatic complexes are more distinct than between equally charged BN and CC congeners. Full article
(This article belongs to the Special Issue Boron Chemistry: Fundamentals and Applications)
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37 pages, 7855 KB  
Review
The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy
by Ha Vinh Lam Nguyen, Walther Caminati and Jens-Uwe Grabow
Molecules 2022, 27(12), 3948; https://doi.org/10.3390/molecules27123948 - 20 Jun 2022
Cited by 22 | Viewed by 5363
Abstract
Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have [...] Read more.
Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have become very diverse. Larger and more complex molecular systems have been taken under investigation, ranging from series of heteroaromatic molecules from five- and six-membered rings to polycyclic-aromatic-hydrocarbon derivatives. Such systems are ideally suited to create families of molecules in which the positions and the number of LAMs can be varied, while the heteroatoms often provide a sufficient dipole moment to the systems to warrant the observation of their rotational spectra. This review will summarize three types of LAMs: internal rotation, inversion tunneling, and ring puckering, which are frequently observed in aromatic five-membered rings such as furan, thiophene, pyrrole, thiazole, and oxazole derivatives, in aromatic six-membered rings such as benzene, pyridine, and pyrimidine derivatives, and larger combined rings such as naphthalene, indole, and indan derivatives. For each molecular class, we will present the representatives and summarize the recent insights on the molecular structure and internal dynamics and how they help to advance the field of quantum mechanics. Full article
(This article belongs to the Special Issue Spectroscopic Characterization of Molecular Clusters and Large Amplitude Motions)
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