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1.
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 %.

2.
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.

3.
ACS Appl Mater Interfaces ; 12(3): 3572-3579, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31799828

RESUMO

Engineering the energetics of perovskite photovoltaic devices through deliberate introduction of dipoles to control the built-in potential of the devices offers an opportunity to enhance their performance without the need to modify the active layer itself. In this work, we demonstrate how the incorporation of molecular dipoles into the bathocuproine (BCP) hole-blocking layer of inverted perovskite solar cells improves the device open-circuit voltage (VOC) and, consequently, their performance. We explore a series of four thiaazulenic derivatives that exhibit increasing dipole moments and demonstrate that these molecules can be introduced into the solution-processed BCP layer to effectively increase the built-in potential within the device without altering any of the other device layers. As a result, the VOC of the devices is enhanced by up to 130 mV, with larger dipoles resulting in higher VOC. To investigate the limitations of this approach, we employ numerical device simulations that demonstrate that the highest dipole derivatives used in this work eliminate all limitations on the VOC stemming from the built-in potential of the device.

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.
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.

7.
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.

8.
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.

9.
Nat Commun ; 10(1): 5202, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729391

RESUMO

Singlet fission is the photoinduced conversion of a singlet exciton into two triplet states of half-energy. This multiplication mechanism has been successfully applied to improve the efficiency of single-junction solar cells in the visible spectral range. Here we show that singlet fission may also occur via a sequential mechanism, where the two triplet states are generated consecutively by exploiting oxygen as a catalyst. This sequential formation of carriers is demonstrated for two acene-like molecules in solution. First, energy transfer from the excited acene to triplet oxygen yields one triplet acene and singlet oxygen. In the second stage, singlet oxygen combines with a ground-state acene to complete singlet fission. This yields a second triplet molecule. The sequential mechanism accounts for approximately 40% of the triplet quantum yield in the studied molecules; this process occurs in dilute solutions and under atmospheric conditions, where the single-step SF mechanism is inactive.

10.
J Phys Chem B ; 123(50): 10780-10793, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31751127

RESUMO

Generating two long-living low-energy excitations after absorption of a single high-energy photon has stoked interest in singlet fission (SF) to enhance solar energy conversion in photovoltaics. To this end, survival of the triplet states is critical. This process is investigated in diethynylbenzene-linked tetraaza-triisopropylsilylethynyl-pentacene dimers, for which SF is energetically feasible and facilitated by the close distances between the azapentacenes. The ortho and meta connectivities are explored and compared with the tetraazapentacene molecule and the (1,3,5) trimer. Efficient SF (potential ΦT ≥ 160%) is demonstrated in all oligomers by quantitative kinetic analysis of broadband transient absorption and fluorescence signals. Together with dynamics of the starting singlet, the triplet pair, and the final free triplet state, our results show an intermediate component with spectral properties compatible with a biexcitonic state. Long-living triplets represent only a fraction of the high number of transient triplet pair intermediates, which undergo triplet-triplet annihilation as well as fusion between neighboring pentacenes. Therefore, our work provides new insight into the SF in covalent dimers and paves the way for the application of these materials for carrier multiplication.

11.
Nat Commun ; 10(1): 4735, 2019 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-31628299

RESUMO

Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.

12.
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.

13.
Chem Commun (Camb) ; 55(76): 11458-11461, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31535684

RESUMO

We report a polymer-based sensor that rapidly detects cancer based on changes in serum protein levels. Using three ratiometric fluorescence outputs, this simple system identifies early stage and metastatic lung cancer with a high level of accuracy exceeding many biomarker-based assays, making it an attractive strategy for point-of-care testing.


Assuntos
Biomarcadores Tumorais/sangue , Proteínas Sanguíneas/análise , Corantes Fluorescentes/química , Neoplasias Pulmonares/diagnóstico por imagem , Polímeros/química , Animais , Fluorescência , Humanos , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/secundário , Camundongos , Camundongos Transgênicos , Estrutura Molecular , Neoplasias Experimentais/sangue , Neoplasias Experimentais/diagnóstico por imagem , Neoplasias Experimentais/secundário , Testes Imediatos
14.
Chemistry ; 25(66): 15147-15154, 2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31482610

RESUMO

N-Heteropolycycles are attractive as materials in organic electronic devices. However, a detailed understanding of the low-energy electronic excitation characteristics of these species is still lacking. In this work, the matrix isolation technique is applied to obtain high-resolution absorbance spectra for a series of tetracene and core-substituted N-analogues. The experimental electronic excitation spectra obtained for matrix-isolated molecules are then analysed with the help of quantum-chemical calculations. Additional lower energy excitation bands in the spectrum of the core-substituted N-derivatives of tetracene could be explained in terms of intensity borrowing from dipole-forbidden transitions due to Herzberg-Teller vibronic coupling. In the case of tetracene, evidence for the additional formation of London dimers (J aggregates) is found at higher tetracene concentrations in the matrix.

15.
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.

16.
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.

17.
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.

18.
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.

19.
J Am Chem Soc ; 141(22): 8834-8845, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31063690

RESUMO

Quantum chemistry and time-resolved spectroscopy are applied to rationalize how singlet fission (SF) is affected by systematic chemical modifications introduced into phenazinothiadiazoles (PTD). Substitution of the terminal aromatic ring of TIPS-tetracene by a thiadiazole group leads to a considerable change in the relative energies of its S1 and T1 states. Thus, in contrast to TIPS-tetracene, SF becomes exothermic for various PTD derivatives, which show S1-2T1 energy differences as high as 0.15 eV. This enables SF in PTD as corroborated by femtosecond transient absorption spectroscopy and TD-DFT calculations. The latter report T-T spectra consistent with thin film UV-vis femtosecond transient absorption of PTDs at long delays. TD-DFT calculations also show that the S1-T1 energy gap can be rationally tuned by introducing N atoms into the aromatic scaffold and by the halogenation of one side ring of the PTD. In addition, the specific S1-to-1(T1T1) electronic coupling depends on the crystal morphology and the electronic properties simultaneously. Thus, both of them govern the strength and the interplay between direct and superexchange couplings, which in the most favorable cases accelerate SF to rate constants beyond (100 fs)-1. Remarkably, direct coupling was found to contribute considerably to the total effective coupling and even to dominate it for some PTDs investigated here. A quantum yield of 200% is obtained on the early picosecond time scale for all compounds studied here, which is reduced to 100% due to triplet-triplet annihilation after a few nanoseconds.

20.
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.

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