Rylenfarbstoffe als maßgeschneiderte Nanoemitter für die Photonik

Fused Isoindigo Ribbons with Absorption Bands Reaching Near-Infrared

Through fusing isoindigo (IID) units at 6,7;6',7'-positions, a series of new near-infrared (NIR) absorbing and stable ribbon-like conjugated molecules, namely nIIDs in which n represents the number of IID units, have been synthesized. The optical band gaps of the molecules are lowered from 2.03 eV of 1IID to 1.12 eV of 6IID with the increase of the conjugation length. 3IID, 4IID, and 6IID have strong absorption in the NIR region and exhibit photothermal conversion efficiencies of greater than 50 % under laser irradiation at λ=808 nm.

Morphology-Independent Efficient Singlet Exciton Fission in Perylene Diimide Thin Films

Perylene diimides are conjugated chromophores that are of considerable interest owing to their ability to transform a singlet excited state into two triplets by singlet fission. Although singlet fission has previously been reported for certain perylene diimide derivatives, there is some uncertainty about the rates and yield of the process in these materials. In this report, ultrafast transient absorption spectroscopy is used to demonstrate that singlet fission in perylene diimides can occur on a sub-picosecond timescale with quantum yields approaching the theoretical limit of 200 %.

The 3 D Structure of Twisted Benzo[ghi]perylene-Triimide Dimer as a Non-Fullerene Acceptor for Inverted Perovskite Solar Cells

Here, we introduced benzo[ghi]perylenetriimide (BPTI) derivatives including monomer and twisted dimer (t-BPTI) as an alternative electron-transport layer (ETL) material to replace the commonly used PC₆₁ BM in inverted planar heterojunction perovskite solar cells (PSCs). Moreover, the double ETL was applied in our PSCs with structure of glass/ITO/PEDOT:PSS/perovskite/BPTI/C₆₀ or PDI-C4/BCP/Al. The use of a double ETL structure can effectively eliminate the leakage current. The devices with the t-BPTI/C₆₀ double ETL yield an average power conversion efficiency of 10.73 % and a maximum efficiency of 11.63 %. The device based on the complete non-fullerene electron acceptors of t-BPTI/PDI-C4 as double ETL achieved maximum efficiency of 10.0 %. Moreover, it was found that the utilization of alloy t-BPTI+BPTI as ETL can effectively reduce the hysteresis effect of PSCs. The results suggest that BPTI-based electron-transport materials are potential alternatives for widely used fullerene acceptors in PSCs.

Efficient catalytic vicinal diamination of arylene diimides

New substitution patterns for rylene diimides by catalytic diamination.

Electroluminescent and Optoelectronic Properties of OLEDs with Bay-Extended, Distorted Perylene Esters as Emitter Materials

Three esters with a perylene, a unilaterally, and a bilaterally extended perylene core, respectively, were used as emitter materials for organic light-emitting diodes. The electroluminescent properties of these devices were studied. Different spectral shifts were found, which can be attributed to the formation of excited dimers (excimers) in the nanofilms of the emitter materials. Thermal treatment of the unilaterally extended derivative resulted in a red-shift of the electroluminescence owing to the formation of a denser nanofilm. The luminance and efficiency of optoelectronic devices employing the extended perylene esters exceed those of devices using an emitter layer comprised of the perylene ester. Different deposition methods, limitations in the deposition process, and the role of hole-transporting materials are compared.

Rigid Nonfullerene Acceptors Based on Triptycene-Perylene Dye for Organic Solar Cells

Three kinds of nonconjugated rigid perylene bisimide (PBI) derivatives based on a triptycene core were designed, synthesized and characterized. The unique three-dimensional (3D) conformation of triptycene could enable formation of polymer with the favorable morphology for organic polymer solar cells (PSCs) by relieving the self-aggregation of rigid PBI units. The low-lying LUMO energy levels of these compounds demonstrated that they are very suitable for use as acceptors in organic solar cells. A higher power conversion efficiency (PCE) of 6.15 % was obtained for the blend film using the compound with two PBI units (T-2) as the acceptor and commercial poly[[4,8-bis[5-(2-ethylhexyl)thiophene-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophenediyl]] (PCE-10) as the electron donor.

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

The synthesis of O-doped polyaromatic hydro- carbons in which two polycyclic aromatic hydrocarbon sub units are bridged through one or two O atoms has been achieved. This includes high-yield ring-closure key steps that, depending on the reaction conditions, result in the formation of furanyl or pyranopyranyl linkages through intramolecular C-O bond formation. Comprehensive photophysical measurements in solution showed that these compounds have exceptionally high emission yields and tunable absorption properties throughout the UV/Vis spectral region. Electrochemical investigations showed that in all cases O annulation increases the electron-donor capabilities by raising the HOMO energy level, whereas the LUMO energy level is less affected. Moreover, third-order nonlinear optical (NLO) measurements on solutions or thin films containing the dyes showed very good values of the second hyperpolarizability. Importantly, poly(methyl methacrylate) films containing the pyranopyranyl derivatives exhibited weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, and thus revealed them to be exceptional organic materials for photonic devices.

Relationship between Side-Chain Polarity and the Self-Assembly Characteristics of Perylene Diimide Derivatives in Aqueous Solution

Perylene-3,4,9,10-tetracarboxylic acid diimides (PDIs) have recently gained considerable interest for water-based biosensing applications. PDIs have been studied intensively in the bulk state, but their physical properties in aqueous solution in interplay with side-chain polarity are, however, poorly understood. Therefore, three perylene diimide based derivatives were synthesized to study the relationship between side-chain polarity and their self-assembly characteristics in water. The polarity of the side chains was found to dictate the size and morphology of the formed aggregates. Side-chain polarity rendered the self-assembly and photophysical properties of the PDIs-both important for imminent water-based applications-and these were revealed to be especially responsive to changes in solvent composition.

Highly Emissive Far Red/Near-IR Fluorophores Based on Borylated Fluorene-Benzothiadiazole Donor-Acceptor Materials

Stille, Suzuki–Miyaura and Negishi cross‐coupling reactions of bromine‐functionalised borylated precursors enable the facile, high yielding, synthesis of borylated donor–acceptor materials that contain electron‐rich aromatic units and/or extended effective conjugation lengths. These materials have large Stokes shifts, low LUMO energies, small band‐gaps and significant fluorescence emission >700 nm in solution and when dispersed in a host polymer.

Accessing the Triplet State in Heavy-Atom-Free Perylene Diimides

Previous studies of perylenediimides (PDIs) mostly utilized the lowest singlet excited state S1 . Generation of a triplet excited state (T1 ) in PDIs is important for applications ranging from photodynamic therapy to photovoltaics; however, it remains a formidable task. Herein, we developed a heavy-atom-free strategy to prompt the T1 ←S1 intersystem crossing (ISC) by introducing electron-donating aryl (Ar) groups at the head positions of an electron-deficient perylenediimide (PDI) core. We found that the ISC efficiency increases from 8 to 54 % and then to 86 % by increasing the electron-donating ability of head-substituted aryl groups from phenyl (p-PDI) to methoxyphenyl (MeO-PDI) and then to methylthioxyphenyl (MeS-PDI). By enhancing the intramolecular charge-transfer (ICT) interaction from p-PDI to MeO-PDI, and then to MeS-PDI, singlet oxygen generation via energy-transfer reactions from T1 of PDIs to (3)O2 was demonstrated with the highest yield of up to 80 %. These results provide guidelines for developing new triplet-generating PDIs and related rylene diimides for optoelectronic applications.

Development of an Enyne Metathesis/Isomerization/Diels-Alder One-Pot Reaction for the Synthesis of a Novel Near-Infrared (NIR) Dye Core

N-Alkyl-N-allyl-2-alkynylaniline derivatives undergo a tandem ring-closing enyne metathesis/isomerization/Diels-Alder cycloaddition sequence in the presence of a second-generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring-closing metathesis to generate cyclic 4-vinyl-1,2-dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring-closing metathesis products are selectively converted into a 7-methyl-4H-naphtho[3,2,1-de]quinoline-8,11-dione core. Overall, the reaction sequence converts simple aniline derivatives into π-conjugated small molecules, which have characteristic absorption in the near-infrared region, in a single operation through three unique ruthenium-catalyzed transformations.

Highly Soluble Benzo[ghi]perylenetriimide Derivatives: Stable and Air-Insensitive Electron Acceptors for Artificial Photosynthesis

A series of new benzo[ghi]perylenetriimide (BPTI) derivatives has been synthesized and characterized. These remarkably soluble BPTI derivatives show strong optical absorption in the range of λ=300-500 nm and have a high triplet-state energy of 1.67 eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (Ered =-0.11 V vs. the normal hydrogen electrode) that electron-trapping reactions with O2 and H2 O do not occur. The BPTI radical anion on a fluorine-doped tin oxide|TiO2 electrode is persistent up to tens of seconds (t1/2 =39 s) in air-saturated buffer solution. As a result of favorable packing, theoretical electron mobilities (10(-2) ∼10(-1) cm(2) V(-1) s(-1)) are high and similar to the experimental values observed for perylene diimide and C60 derivatives. Our studies show the potential of the cyanophenyl-modified BPTI compounds as electron acceptors in devices for artificial photosynthesis in water splitting that are also very promising nonfullerene electron-transport materials for organic solar cells.

Organic Crystals with Near-Infrared Amplified Spontaneous Emissions Based on 2'-Hydroxychalcone Derivatives: Subtle Structure Modification but Great Property Change

A series of highly efficient deep red to near-infrared (NIR) emissive organic crystals 1-3 based on the structurally simple 2'-hydroxychalcone derivatives were synthesized through a simple one-step condensation reaction. Crystal 1 displays the highest quantum yield (Φf) of 0.32 among the reported organic single crystals with an emission maximum (λem) over 710 nm. Comparison between the bright emissive crystals 1-3 and the nearly nonluminous compounds 4-7 clearly gives evidence that a subtle structure modification can arouse great property changes, which is instructive in designing new high-efficiency organic luminescent materials. Notably, crystals 1-3 exhibit amplified spontaneous emissions (ASE) with extremely low thresholds. Thus, organic deep red to NIR emissive crystals with very high Φf have been obtained and are found to display the first example of NIR fluorescent crystal ASE.

Control of the intermolecular coupling of dibromotetracene on Cu(110) by the sequential activation of C-Br and C-H bonds

Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions.

The B(C6F5)3 boron Lewis acid route to arene-annulated pentalenes

4,5-Dimethyl-1,2-bis(1-naphthylethynyl)benzene (12) undergoes a rapid multiple ring-closure reaction upon treatment with the strong boron Lewis acid B(C6F5)3 to yield the multiply annulated, planar conjugated π-system 13 (50 % yield). In the course of this reaction, a C6F5 group was transferred from boron to carbon. Treatment of 12 with CH3B(C6F5)2 proceeded similarly, giving a mixture of 13 (C6F5-transfer) and the product 15, which was formed by CH3-group transfer. 1,2-Bis(phenylethynyl)benzene (8 a) reacts similarly with CH3B(C6F5)2 to yield a mixture of the respective C6F5- and CH3-substituted dibenzopentalenes 10 a and 16. The reaction is thought to proceed through zwitterionic intermediates that exhibit vinyl cation reactivities. Some B(C6F5)3-substituted species (26, 27) consequently formed by in situ deprotonation upon treatment of the respective 1,2-bis(alkynyl)benzene starting materials (24, 8) with the frustrated Lewis pair B(C6F5)3/P(o-tolyl)3. The overall formation of the C6F5-substituted products formally require HB(C6F5)2 cleavage in an intermediate dehydroboration step. This was confirmed in the reaction of a thienylethynyl-containing starting material 21 with B(C6F5)3, which gave the respective annulated pentalene product 23 that had the HB(C6F5)2 moiety 1,4-added to its thiophene ring. Compounds 12-14, 23, and 26 were characterized by X-ray diffraction.