Near-Infrared Perylenecarboximide Fluorophores for Live-Cell Super-Resolution Imaging.

Organic near-infrared (NIR) photoblinking fluorophores are highly desirable for live-cell super-resolution imaging based on single-molecule localization microscopy (SMLM). Herein we introduce a novel small chromophore, PMIP, through the fusion of perylenecarboximide with 2,2-dimetheylpyrimidine. PMIP exhibits an emission maximum at 732 nm with a high fluorescence quantum yield of 60% in the wavelength range of 700-1000 nm and excellent photoblinking without any additives. With resorcinol-functionalized PMIP (PMIP-OH), NIR SMLM imaging of lysosomes is demonstrated for the first time in living mammalian cells under physiological conditions. Moreover, metabolically labeled nascent DNA is site-specifically detected using azido-functionalized PMIP (PMIP-N3) via click chemistry, thereby enabling the super-resolution imaging of nascent DNA in phosphate-buffered saline with a 9-fold improvement in spatial resolution. These results indicate the potential of PMIP-based NIR blinking fluorophores for biological applications of SMLM.

TADF Blue Emitters with Balanced π-Conjugation─Design, Synthesis, Spectral Characterization, and a Model OLED with 8-(5-(tert-Butyl)-1,3,4-oxadiazol-2-yl)-N,N-bis(4-(tert-butyl)phenyl)dibenzo[b,d]furan-2-amine.

Blue organic light-emitting diodes (OLED) suffer from relatively short lifetimes and a comparatively low lighting efficiency. One of the approaches to improving their characteristics is the development of luminophores with the potential for thermally activated delayed fluorescence (TADF). Herein, a set of donor-spacer-acceptor compounds with potential for TADF are designed, synthesized, and computationally and spectroscopically characterized. The excited state dynamics of the most prospective dye is monitored by time-resolved fluorescence and transient absorption spectroscopy. The experimental data are obtained and processed by a newly developed method and supplemented by quantum chemical calculations. The comprehensive approach allowed rationalization of the complex cascade-type photophysical behavior. The most promising emitter is included in an OLED displaying a blue color with a maximum EQE of 4.9% and negligible efficiency roll-off at higher luminance.

Microwave-Assisted, Copper-Catalyzed Domino O-H/C-H Arylation Reaction toward the Synthesis of Oxygen-Doped Polyaromatic Molecules.

Benzoxanthenes and their analogues are a very important class of compounds mainly due to their wide range of biological and technological applications. The development of a new methodology for their synthesis, involving an Ullmann-type coupling followed by an intramolecular C-H arylation, catalyzed by copper in a domino fashion, is reported. A variety of para-substituted phenols are amenable to this methodology, affording the desired products in moderate to good yields. Our protocol is expedient and practical and is carried out under microwave irradiation in only 3 min under air. A plausible catalytic cycle is proposed based on experimental mechanistic investigations and density functional theory (DFT) calculations.

Dioxepine-Peri-Annulated PMIs-Synthesis and Spectral and Sensing Properties.

New perylene monoimide (PMI) derivatives bearing a seven-membered heterocycle and 1,8-diaminosarcophagine (DiAmSar) or N,N-dimethylaminoethyl chelator fragments were synthesized, and their spectroscopic properties in the absence and presence of metal cations were determined to evaluate their potential applications as PET optical sensors for such analytes. DFT and TDDFT calculations were employed to rationalize the observed effects.

High-Performance Near-Infrared Chlorinated Rylenecarboximide Fluorophores via Consecutive C-N and C-C Bond Formation.

A new class of near-infrared (NIR) fluorophores, PAI, is obtained by consecutive C-N/C-C bond formation between diphenylamines and 9,10-dibromoperylenecarboximide. Owing to the rigid structure, extended π-conjugation and pronounced push-pull substitution, these fluorophores show emission maxima up to 804 nm and large Stokes shifts. The extraordinarily high fluorescence quantum yields from 47 % to 70 % are attributed to chloro substitution in the bay positions of the perylene core. These characteristics, together with high photostability, qualify them as useful NIR emitters for applications as biomarkers and security inks.

Benchmarking of Density Functionals for the Description of Optical Properties of Newly Synthesized π-Conjugated TADF Blue Emitters.

Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet-triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π-electron conjugation, at the same time possessing high-energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient-corrected through global hybrids to range-separated ones. The results show that the monitored optical properties are especially sensitive to how the long-range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π-electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta-GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively.

1,7,9,10-Tetrasubstituted PMIs Accessible through Decarboxylative Bromination: Synthesis, Characterization, Photophysical Studies, and Hydrogen Evolution Catalysis.

In this work, we present a new synthetic strategy for fourfold-substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X-ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior. We observed the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation. In the presence of poly(dehydroalanine)-graft-poly(ethylene glycol) graft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo3 S13 ]2- clusters in aqueous solution for stable visible light driven hydrogen evolution over three days.

Estrone derived 2-naphthol analogue in the diastereoselective one-pot Betti-condensation.

The utility of deoxy-isoequilenine synthesized from estrone as valuable 2-naphthol analogue is demonstrated in the three components Betti-condensation. A simple, efficient and green procedure for the synthesis of aminobenzylnaphthol analogues (so-called Betti bases) has been realized highly diastereoselectively by using (S)-phenylethylamine and 1- or 2-naphthaldehyde. The absolute configuration of the new chiral compounds obtained has been determined by means of NMR experiments and confirmed by X-ray crystallography. The chiral steroidal aminobenzylnaphthols have been evaluated as pre-catalysts for the addition of diethylzinc to aldehydes with enantioselectivities of up to 98% ee.

Hydrogen-Bonded Donor-Acceptor Arrays at the Solution-Graphite Interface.

Controlling the nanoscale morphology of organic thin films represents a critical challenge in the fabrication of organic (opto)electronic devices. The morphology of the (multicomponent) thin films in turn depends on the mutual orientation of the molecular components and their supramolecular packing on the surface. Here, it is shown how the surface co-assembly of electron-donating and -accepting building blocks can be controlled via (supra)molecular design. Hexa-peri-hexabenzocoronene (HBC) derivatives with multiple hydrogen-bonding (H-bonding) sites were synthesized and their co-assembly with alkyl-substituted perylene tetracarboxy diimide (PDI) was studied using scanning tunneling microscopy (STM) at the solution-graphite interface. STM data shows that electron-rich HBCs co-assemble laterally with electron deficient PDIs via preprogrammed H-bonding sites with high fidelity. The surface stoichiometry of the two components could be readily tuned by changing the number of H-bonding sites on the HBC derivatives via organic synthesis. This model study highlights the utility of (supra)molecular design in co-assembly of building blocks relevant for organic electronics.

Ultra-Narrow Low-Bandgap Graphene Nanoribbons from Bromoperylenes-Synthesis and Terahertz-Spectroscopy.

Soluble ultra-narrow armchair graphene nanoribbons (AGNRs) with length of ≈20 nm and completely fused cores exceeding 5 nm in length, pronounced near-infrared (NIR) absorption up to 1400 nm, and a low band gap (≈0.9 eV) are synthesized from 3,9(3,10)-dibromoperylene and 3,4,9,10-tetrabromoperylene. Since the monomers are obtained from perylene carboxyanhydrides, a remarkable link between dye and graphene chemistry is established. The two-step protocol for the AGNR synthesis by aryl-aryl coupling and subsequent cyclodehydrogenation is compared with a direct Yamamoto polymerization. Ultrafast photoconductivity analysis by optical pump-terahertz (THz) probe spectroscopy of the longest AGNRs excited in the NIR regime (800 nm) reveal their high intrinsic charge carrier mobility.

Water-Soluble NIR-Absorbing Rylene Chromophores for Selective Staining of Cellular Organelles.

Biocompatible organic dyes emitting in the near-infrared are highly desirable in fluorescence imaging techniques. Herein we report a synthetic approach for building novel small peri-guanidine-fused naphthalene monoimide and perylene monoimide chromophores. The presented structures possess near-infrared absorption and emission, high photostability, and good water solubility. After a fast cellular uptake, they selectively stain mitochondria with a low background in live and fixed cells. They can be additionally modified in a one-step reaction with functional groups for covalent labeling of proteins. The low cytotoxicity allows a long time exposure of live cells to the dyes without the necessity of washing. Successful application in localization super-resolution microscopy was demonstrated in phosphate-buffered saline without any reducing or oxidizing additives.

On-surface synthesis of rylene-type graphene nanoribbons.

The narrowest armchair graphene nanoribbon (AGNR) with five carbons across the width of the GNR (5-AGNR) was synthesized on Au(111) surfaces via sequential dehalogenation processes in a mild condition by using 1,4,5,8-tetrabromonaphthalene as the molecular precursor. Gold-organic hybrids were observed by using high-resolution scanning tunneling microscopy and considered as intermediate states upon AGNR formation. Scanning tunneling spectroscopy reveals an unexpectedly large band gap of Δ = 2.8 ± 0.1 eV on Au(111) surface which can be interpreted by the hybridization of the surface states and the molecular states of the 5-AGNR.

Naphthalene Monoimides with Peri-Annulated Disulfide Bridge-Synthesis and Electrochemical Redox Activity.

Nowadays, organosulfur compounds provide new options in the development of full organic ion batteries. However, many drawbacks (such as kinetics limitations during the reversible oxidation of disulfides with cleavage of S-S bond, as well as solubility in non-aqueous electrolytes) make their commercialization difficult. Herein, a new concept for the design of organosulfur compounds with regulated redox properties and limited solubility is proposed. As a proof-of-concept, we designed peri-disulfo-substituted 1,8-naphthalimide derivatives, in which the alkyl chain length and halogen substituents (Cl or Br) at positions 3 and 6 are varied. The compounds were synthesized by an originally developed procedure starting from tetrahalonaphthalic anhydride via nucleophilic substitution at both peri-positions in the respective imide. Using ionic liquid electrolyte, it was found that the new peri-dithiolo-1,8-naphthalimides can participate in n- and p-type redox reactions at about 2.0 V and above 4.0 V vs. Li/Li+, respectively. The redox potentials are sensitive mainly to whether Cl or Br substituents are available in the molecule architecture, while the alkyl chain length determines the kinetics of the redox reactions. Among all compounds, the chloro-substituted compound with the shorter alkyl chain displays the best kinetics for both low- and high-voltage redox reactions.

Carbonyl-Functionalized Cyclazines as Colorants and Air-Stable n-Type Semiconductors.

A series of π-extended cycl[3,3,2]azines (3) bearing additional carbonyl groups were synthesized via aldol condensations. Two strong electron acceptor molecules (4 and 5), with low-lying LUMO energy levels of -3.99 and -3.95 eV, respectively, were obtained. Organic thin-film transistors (TFTs) based on the cyanated cyclazine derivatives 5 were fabricated by vapor deposition, exhibiting extraordinarily stable n-type semiconductor character under ambient condition with the highest electron mobility of 0.06 cm2 V-1 s-1 consistently for more than 30 months.

[FeFe]-Hydrogenase H-cluster mimics mediated by naphthalene monoimide derivatives of peri-substituted dichalcogenides.

Synthetic models of the active site of [FeFe]-hydrogenase containing naphthalene monoimide (NMI) of peri-substituted dichalcogenides as bridging linkers have been prepared and characterized using different spectroscopic methods. The influence of the imide functionality and the chalcogen atoms on the redox properties and the catalytic behaviour of complexes 7-10 was studied using cyclic voltammetry. The results revealed that the imide functionality has improved the chemical stability of the reduced species and the replacement of the S atoms by Se caused a cathodic shift in the oxidation peaks. Moreover, the optical properties of compounds 1, 2, 4, and 5 and the respective diiron complexes 7-10 were investigated by UV-Vis absorption and fluorescence spectroscopy assisted by quantum chemical simulations. The structures of complexes 6-9 were confirmed by X-ray diffraction analysis.

Self-Assembly of an Amphiphilic π-Conjugated Dyad into Fibers: Ultrafast and Ultrasensitive Humidity Sensor.

The self-assembly of an amphiphilic monomolecular electron acceptor-donor dyad into electroactive π-π stacked fibrillar structures can be triggered by irradiation with visible light. These fibers, exposing hydrophilic ethylene glycol in their external shell, show unique characteristics as resistive humidity sensors that exhibit high sensitivity and ultrafast response.

Toward perylene dyes by the Hundsdiecker reaction.

An efficient method to synthesize 3,4,9,10-tetrabromoperylenes is reported under optimized Hunsdiecker conditions. Various octasubstituted perylenes were obtained by reaction of 1,6,7,12-tetrachloro-3,4,9,10-tetrabromoperylene with phenol, trimethylsilyl chloride, cooper cyanide, or sulfur via metal-catalyzed couplings or nucleophilic substitutions. These new perylenes show completely different optical and redox properties, thus opening a facile way to develop new chromophophore structures.

Facile transformation of perylene tetracarboxylic acid dianhydride into strong donor-acceptor chromophores.

An efficient synthesis of 9,10-dibromo-1,6,7,12-tetrachloro-perylene-3,4-dicarboxylic acid monoimides from easily available 1,6,7,12-tetrachloro-perylene-3,4,9,10-tetracarboxylic acid dianhydride is reported. Therefrom, unprecedented perylene monoimides with pronounced donor-acceptor character were obtained via twofold aromatic amination. The halogen substituents in the 1,6,7,12-positions of perylene were removed under basic conditions. To the best of our knowledge, this is the first efficient synthetic route toward 9,10-doubly functionalized perylene-3,4-dicarboxylic acid monoimides.