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1.
Artigo em Inglês | MEDLINE | ID: mdl-32190951

RESUMO

Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low-energy gap ΔEST' of 0.58 to 1.0 kcal mol-1 . The species are persistent in solution (half-life≈14-21 h) and in the solid state they are stable for weeks.

2.
Chemistry ; 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-32220032

RESUMO

Two linear 1,4-distyrylbenzenes and five star-shaped 1,3,5-tristyrylbenzene derivatives (L2a-L2b, Y0-Y3 and YNBu) were synthesized and spectroscopically characterized. The photophysical properties, optical response to acid and metal ions were investigated. Upon backbone extension of linear distyrylbenzenes or the introduction of dibutylanilines, the electronic spectra are red-shifted. Incorporation of electron-deficient pyridyl units does not significantly affect the optical properties. Variation of the number of pyridine rings and substitution pattern tune the fluorescence response to acids and metal ions. The novel arenes discriminate Al3+, Mn2+, Fe3+, Fe2+, Cd2+, Ag+ and Hg2+.

3.
Chemistry ; 26(4): 799-803, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31609025

RESUMO

The synthesis, property evaluation, and single crystal X-ray structures of four 5,7,12,14-tetrafunctionalized diazapentacenes are presented. The synthesis of these compounds either starts from tetrabromo-N,N-dihydrodiazapentacene or from a diazapentacene tetraketone. Pd-catalyzed coupling or addition of a lithium acetylide gave the precursors that furnish, after further redox reactions, the diazapentacenes as stable crystalline materials. The performance of the tetraphenyl-substituted compound as n-channel semiconductor was evaluated in organic field effect transistors.

4.
Chemistry ; 26(5): 1013-1016, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31609484

RESUMO

The synthesis of a decaethynylated tetraazapentacene is described. It was obtained by a combination of condensation reactions giving the two pyrazine rings and subsequent consecutive Stille-type couplings. This is the first example of any higher (hetero)acene that is peralkynylated. The presence of the four nitrogen atoms removes the peri interaction of the substituted alkyne groups, giving this rock-stable and highly twisted heteroacene.

5.
Chemistry ; 26(1): 160-164, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31538683

RESUMO

A series of quinoidal N,N'-diaryldiaza-N,N'-dihydropentacenes (Quino) was prepared in a two-step reaction, starting from quinacridone. Oxidation of Quino furnishes stable radical cations, isoelectronic to the radical anions of the azaacenes, whereas the dicationic species are isoelectronic to neutral azapentacenes. The spectroscopic properties of the diaryldiazapentacenes and their oxidized mono- and dications are equivalent to that of the dianion of tetraazapentacene (TAP), its radical anion and the neutral TAP.

6.
Angew Chem Int Ed Engl ; 59(5): 1966-1969, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31724294

RESUMO

In combination with bulky substituents at the core, fourfold benzannulation at the cata-positions stabilizes a nonacene sufficiently to allow its isolation and characterization by 1 H NMR and X-ray analysis. The four benzo units blueshift the absorption spectrum in comparison to a solely linear nonacene, but significantly increase the stability in the solid state.

7.
J Org Chem ; 85(1): 296-300, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31686519

RESUMO

A series of dibenzosuberone-fused N-heteroacenes was obtained by the condensation of dibenzosuberonetriketone with a series of substituted diamino- and tetramino-arenes. The electron-deficient triketone reacts at room temperature and furnishes the pyrazine or bis-pyrazine-containing condensation products in good to excellent yield. The targets all display negative curvature according to single crystal structures.

8.
Chemistry ; 26(2): 412-418, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31657859

RESUMO

The synthesis of five spiro-linked azaacene dimers is reported and their properties are compared to that of their monomers. Dimerization quenches emission of the longer (≥(hetero)tetracenes) derivatives and furnishes amorphous thin-films, the absorption is not affected. The larger derivatives were tested as acceptors in bulk-heterojunction photovoltaic devices with a maximum power conversion efficiency of up to 1.6 %.

9.
ACS Appl Mater Interfaces ; 12(5): 6565-6572, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31825591

RESUMO

Conformationally rigid multipodal molecules should control the orientation and packing density of functional head groups upon self-assembly on solid supports. Common tripods frequently fail in this regard because of inhomogeneous bonding configuration and stochastic orientation. These issues are circumvented by a suitable tetrapodal diazatriptycene moiety, bearing four thiol-anchoring groups, as demonstrated in the present study. Such molecules form well-defined self-assembled monolayers (SAMs) on Au(111) substrates, whereby the tetrapodal scaffold enforces a nearly upright orientation of the terminal head group with respect to the substrate, with at least three of the four anchoring groups providing thiolate-like covalent attachment to the surface. Functionalization by condensation chemistry allows a large variety of functional head groups to be introduced to the tetrapod, paving the path toward advanced surface engineering and sensor fabrication.

10.
Chemistry ; 25(64): 14522-14526, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31529726

RESUMO

The syntheses of new, fourfold alkynylated tetraazaacenoacenes (tetraazaanthracenoanthracene, tetraazatetracenotetracene and tetraazapentacenopentacene) are reported. This novel heteroacenoacene motif exhibits surprisingly strong electronic coupling between its constituting diazaacene units.

11.
J Org Chem ; 84(15): 9826-9834, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31309840

RESUMO

We efficiently synthesized otherwise difficult to obtain 2,3- and 2,3,6,7-halogenated anthracenes with diverse east/west substituents. Key steps involve the (i) Vollhardt cyclization of bis(propargyl)benzenes with bis(trimethylsilyl)acetylene, (ii) halo-desilylation introducing chlorine, bromine, or iodine substituents, and (iii) dehydrogenation. Pd catalysis allows selective functionalization at the anthracenes' east/west positions. A tetrahydropentacene is synthesized and derivatized via the same strategy, employing tetrapropargylbenzene.

12.
Chemistry ; 25(48): 11218-11222, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31192476

RESUMO

The synthesis, properties and X-ray single-crystal structures of two regioisomeric triphenyl tristyrylbenzenes are reported. Both C3v and Cs derivatives display aggregation-induced emission (AIE) behavior. Regioisomerism impacts the solid-state intermolecular interactions, the photophysical characteristics and photostability in solution.

13.
Acc Chem Res ; 52(6): 1575-1587, 2019 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-31181909

RESUMO

N-Heteroacenes and N-heteroarenes are the heterocyclic congeners of the acenes and arenes, in which one or several perimeter C-H bonds have been substituted by pyridine-type nitrogen atoms. They are formally segments out of N-doped nanographenes. Position and number of the nitrogens vary greatly, making N-heteroacenes and N-heteroarenes define a vast class of N-nanographene segments; they display modular electronic and structural properties. The nitrogen atoms in the perimeter lead to finely tunable frontier molecular orbital positions and therefore improved electron affinity and higher oxidative stability but conversely also require and allow different synthetic approaches than those reported for the synthesis of their hydrocarbon and nanographene analogues. The chemistry of N-heteroarenes, despite being known for more than a century, has made significant progress in the last years and established these materials both as powerful n-channel semiconductors in thin film transistors and as useful emitters in organic light emitting diodes (OLEDs) and in photovoltaic devices. The electronegative nitrogen atoms impart a deep LUMO into the azaacenes and azaarenes, improve electron injection, and enable powerful electron transport but also charge separation in bulk-heterojunction type organic photovoltaic (OPV) devices. At the same time, azaacenes and azaarenes are fundamentally exciting materials that push the limits of structure and stability, constantly displaying novel topologies and structures as variations of a simple leitmotif; we expect a bright future for esthetically pleasing yet highly functional N-heterocyclic species. Firstly, we discuss novel structures and structural elements that have evolved during the last years in N-heteroacene and N-heteroarene chemistry and delineate their properties. An important aspect is the oligomerization or better multimerization of azaacene and azaarene units into novel and surprising topologies, in which multiple azaarenes or azaacenes are stitched together. Examples are tetrahedral assemblies of tetraazapentacenes but also cyclic tetramers of different types of azaacenes and linearly bent, S-shaped, formally dimeric species. An exciting aspect of the exploration of the structural manifold of azaacenes is their electronic interaction in such assemblies and their solid-state microstructure. A further aspect of this work is the increase in size of the azaacenes and concepts that allow stabilization of the larger congeners. The attachment of four benzo units to the azaacene core is a powerful concept that stabilizes tetraazaheptacenes and should also be useful to achieve persistent tetraazanonacenes. Secondly, we describe the success of N-heteroacenes and N-heteroarenes in organic electronic devices; specifically, the use of symmetrical halogenated tetraazapentacenes as superb n-channel transistor materials with air stable and persistent radical anions as charge carriers; we discuss the structural reason for their success. Use of azaacenes and azaarenes is not restricted to transistors, but they are also applied in bulk heterojunction photovoltaic devices and in brightly emitting OLEDs. Azaacenes and azaarenes are attractive segments out of hetero-nanographenes and objects of study, starting from fundamental structural and topological questions, ranging to powerful applications in organic electronics. The general interest in azaacenes is witnessed by the constantly increasing number of groups who discover and work on these materials as novel functional and flexible species.

14.
Chemistry ; 25(42): 9840-9845, 2019 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-31155772

RESUMO

A bis(benzobuta)tetraazapentacene derivative was reduced to its radical anion and its dianion, using potassium [18]crown-6 anthracenide in THF. Both reduced species were characterized by UV/Vis spectroscopy of the isolated species and by spectroelectrochemistry. Two distinct single-crystal structures of the dianion and an EPR spectrum of the radical anion were obtained. Contrary to other azaacenes, the lowest energy absorption in the UV/Vis spectrum of the dianion is redshifted in comparison to that of the neutral compound.

15.
ACS Appl Mater Interfaces ; 11(21): 19481-19488, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31050397

RESUMO

We investigated unsubstituted poly( para-phenylene) (PPP), a long-desired prototype of a conjugated polymer semiconductor. PPP was accessed via thermal aromatization of a precursor polymer bearing kinked, solubility-inducing dimethoxycyclohexadienylene moieties. IR spectroscopy and Vis ellipsometry studies revealed that the rate of conversion of the precursor to PPP increases with temperature and decreases with film density, indicating a process with high activation volume. The obtained PPP films were analyzed in thin-film transistors to gain insights into the interplay between the degree of conversion and the resulting p-type semiconducting properties. The semiconducting behavior of PPP was further unambiguously proven through IR and transistor measurements of molybdenum trioxide p-doped films.

16.
Chemistry ; 25(24): 6082-6086, 2019 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-30811069

RESUMO

This work reports the synthesis and characterization of bis- and tetrakis(thiadiazolo)-appended di- and tetraazaacenes, displaying up to seven catenated benzene/pyrazine rings. The targets are obtained by condensation of benzo-bis(thiadiazole)-4,5-dione with aromatic di- and tetraamines. The condensation products-up to a heptacene-like species-are stable but can be insoluble. Soluble derivatives are readily processible, but do not show enhanced electron affinities, as the two or four attached benzothiadiazole units are effectively resonance-separated from the acene body, maximizing the number of Clar-sextets.

17.
Chemistry ; 25(21): 5412-5415, 2019 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-30724396

RESUMO

A thiaazulenic quinone TAQ was synthesized and its optical and redox properties were investigated. The deep blue-colored compound is readily and reversibly reduced to the colorless anionic state. Electrochromic films were prepared and showed reversible switching behavior for the anodically coloring and NIR electrochromic material.

18.
Chemistry ; 25(11): 2723-2728, 2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30624815

RESUMO

1,4-Diketopyrrolo[3,4-c]pyrroles (DPPs) constitute a class of hydrogen-bonded pigments covering a color range from yellow-orange to dark violet. We report facile dimerization of a Boc-substituted 3,6-dithienyl-DPP. The formed dimer shows brilliantly blue color as a result of the expansion of the chromophore. The soluble dimer acts as latent pigment and is converted to the corresponding pigment either via thermocleavage or acidic deprotection of the Boc groups. The synthesized pigment is characterized by high migrational stability in a polymer matrix and a clear blue color.

19.
Gene ; 691: 141-152, 2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30630097

RESUMO

The nuclear human genome harbors sequences of mitochondrial origin, indicating an ancestral transfer of DNA from the mitogenome. Several Nuclear Mitochondrial Segments (NUMTs) have been detected by alignment-based sequence similarity search, as implemented in the Basic Local Alignment Search Tool (BLAST). Identifying NUMTs is important for the comprehensive annotation and understanding of the human genome. Here we explore the possibility of detecting NUMTs in the human genome by alignment-free sequence similarity search, such as k-mers (k-tuples, k-grams, oligos of length k) distributions. We find that when k=6 or larger, the k-mer approach and BLAST search produce almost identical results, e.g., detect the same set of NUMTs longer than 3 kb. However, when k=5 or k=4, certain signals are only detected by the alignment-free approach, and these may indicate yet unrecognized, and potentially more ancestral NUMTs. We introduce a "Manhattan plot" style representation of NUMT predictions across the genome, which are calculated based on the reciprocal of the Jensen-Shannon divergence between the nuclear and mitochondrial k-mer frequencies. The further inspection of the k-mer-based NUMT predictions however shows that most of them contain long-terminal-repeat (LTR) annotations, whereas BLAST-based NUMT predictions do not. Thus, similarity of the mitogenome to LTR sequences is recognized, which we validate by finding the mitochondrial k-mer distribution closer to those for transposable sequences and specifically, close to some types of LTR.


Assuntos
Núcleo Celular/genética , Mitocôndrias/genética , Análise de Sequência de DNA/métodos , Algoritmos , Evolução Molecular , Genoma Humano , Humanos , Filogenia , Alinhamento de Sequência
20.
Chemistry ; 24(49): 12801-12805, 2018 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-29964330

RESUMO

Soluble butterfly-shaped tetraazapentacenes and tetraazaheptacenes were prepared by condensation or Stille coupling with a stannafluorene. The stability of the benzo-winged tetraazaheptacene is dramatically increased through the fourfold benzannulation, yet its acene character is retained to a significant extent.

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