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Efficient synthetic routes that combine different palladium‐catalyzed cross‐coupling reactions have been developed for the preparation of a new family of push‐pull derivatives in which pyridine was used as the acceptor group and different para‐substituted diphenylamines as the donor groups. All compounds showed absorption in the UV/Vis region and blue‐green emission with high quantum yields. Significant red shifts were observed in the absorption and fluorescence emission maxima on increasing the electron‐donating ability of the substituents or on incorporating a π‐conjugated linker. This finding can be explained on the basis of enhanced intramolecular charge transfer (ICT). Strong emission solvatochromism confirmed the formation of an intramolecular charge‐separated emitting state. The HOMO‐LUMO energy gaps have been estimated by experimental electrochemical measurements and the results were interpreted with the aid of DFT calculations. The thermal behavior of all materials has also been studied by differential scanning calorimetry. A series of push‐pull chromophores with a pyridine electron‐withdrawing fragment and methoxy‐, 9H‐carbazol‐9‐yl‐, and 5‐methoxythiophen‐2‐yl‐substituted diphenylamino groups as electron‐donating units was designed. [ABSTRACT FROM AUTHOR]

The formation of chromophore arrays using a DNA templating approach leads to the creation of supramolecular assemblies, where the optical properties of the overall system can be fine‐tuned to a large extent. In particular, porphyrin derivatives have been shown to be versatile building blocks; mostly covalent chemistry was used for embedding the units into DNA strands. Self‐assembly of porphyrin modified nucleosides, on the other hand, has not been investigated as a simplified approach. We report on the synthesis of a magnesium(II) tetraaza porphine (MgTAP) coupled to deoxyuridine, and array formation on DNA templates which contain well‐defined oligo(dA) segments showing strong fluorescence enhancement which is significantly larger than that with a Zn‐porphyrin. The use of the deep‐eutectic solvent glycholine is essential for successful assembly formation. The system allows for sizing of short tandem repeat markers with multiple adenosines, thus the concept could be adaptable to in vitro forensic DNA profiling with a suitable set of different chromophores on all nucleosides. [ABSTRACT FROM AUTHOR]

We present first principle studies on the rational design of an acridine/N‐methylacridinium dye (Acr/MeAcr+) substituted terpyridine ligand to investigate if these chromophores can act as triplet‐energy storage units in bis(terpyridine) ruthenium(II) complexes. We studied the influence of the dye form (Acr/MeAcr+) as well as the interconnecting linker unit (none, 4‐phenyl, or 5‐thien‐2‐yl) and investigated these aspects by steady‐state/time‐resolved spectroscopy, cyclic voltammetry, X‐ray structure analysis, and DFT calculations. [ABSTRACT FROM AUTHOR]

We have discovered a new and unexpected substitution reaction of BODIPY. Through single-crystal XRD analysis, DFT calculations, and other complimentary spectroscopic methods, we have confirmed that the molecular structural assignment of the previously reported nucleophilic substitution of the halogenated carbon atom at the meso position of BODIPY was inaccurate. Indeed, in these substitution reactions, the amino attaches to the methyl group at the 3- or 5-position and not on the meso-carbon of the BODIPY core. As a result of this unexpected substitution reaction, we prepared a BODIPY dimer, attached to the stable radical TEMPO (2,2,6,6-tetramethyl-1- piperidinyloxyl). We confirmed the efficient formation of the triplet state (ΦΔ = 59%, τT = 2.8 μs) of this BODIPY-TEMPO triad through the radical-enhanced intersystem crossing mechanism by using nanosecond time-resolved transient absorption spectroscopy. Through time-resolved EPR spectroscopy, the doublet (spin angular momentum quantum number S = 1/2) and quartet (S = 3/2) states of the triad were observed. Moreover, we observed a strong intramolecular ground-state interaction between the BODIPY chromophores in the triad, which shows new spectral features different to those of H- or J-aggregates and the exciton coupling effect. These TEMPO-labeled compounds were used as triplet photosensitizers for triplet- triplet annihilation (TTA) upconversion (quantum yield ΦUC = 4.7%). [ABSTRACT FROM AUTHOR]

New organic materials containing a cyano-functionalized carbazole moiety at one end linked to different chromophores such as fluorene, carbazole, and triphenylamine at the other end through an acetylene spacer are synthesized and characterized by photophysical, electrochemical, thermal, and electroluminescence studies. A meta-like linkage at the C-2 and C-7 atoms of the central carbazole moiety and the choice of chromophore restricted the emission to the near-ultraviolet region. The photophysical properties of the compounds depend on the nature of the chromophore attached to the carbazole unit. A triphenylamine-substituted derivative exhibited the longest wavelength emission in the series, attributable to the elongated conjugation and electron richness of triphenylamine, whereas the phenyl- and fluorene-functionalized molecules showed the shortest wavelength emissions with vibronic patterns. The compounds containing carbazole and triphenylamine units exhibited positive solvatochromism in their fluorescence spectra, and this behavior is characteristic of charge transfer from a donor to an acceptor. A fluorene derivative containing cyano substituents at the carbazole and fluorene moieties exhibited the best electroluminescence characteristics in the series, probably because of balanced charge transport and effective confinement of the excitons in the emissive layer. [ABSTRACT FROM AUTHOR]

Four series of new push-push-pull chromophores based on two types of heterocyclic cores, namely imidazo- [5,1,2-cd]indolizines and naphtho[1',2':4,5]imidazo[1,2-a]pyridines, and two types of linear p spacers, namely diphenylacetylene and biphenyl, were prepared. The two isomeric heterocyclic compounds were prepared by palladium-catalyzed double C-H functionalization reactions. Further palladium-catalyzed C-C coupling reactions allow the construction of diphenylacetylene and biphenyl spacers on the chromophores. Different electron-donors including NMe2, NPh2, and OMe and CN acceptors were incorporated into the chromophores. The corresponding donor- and acceptor-free compounds were also prepared for comparative studies. In the case of chromophores with strong NMe2 or NPh2 donors, a strong intramolecular charge-transfer (ICT) process occurs leading to fluorescence emission quenching in polar solvents. The use of a slightly weaker OMe donor together with the naphtho[1',2':4,5]imidazo[ 1,2-a]pyridine core allows to obtain an intense blue fluorescence with high quantum yield of up to 0.825. DFT and TD-DFT calculations offer satisfactory explanations to the observed photophysical data. [ABSTRACT FROM AUTHOR]

Mono- and diglyoxylation of chrysene and naphthalene leads to Perkin reactants that yield bismaleates, which efficiently photocyclize to elongated phenacenetetracarboxylic esters. Their band gaps remain significantly larger than the value postulated for polyphenacene. The reaction with α-branched amines gives the corresponding imides, which are significantly stronger electron acceptors than the esters. The obtained [12]- and [14]phenacenes are the longest [n]phenacenes that have been synthesized to date. [ABSTRACT FROM AUTHOR]

Three donor-acceptor-donor (D-A-D) pyrene chromophores are described and compared by DFT computations. The two properties of low energy photon absorption and low energy electrochemical reduction are demonstrated through a pyrene framework. Altering the electron-acceptor strength of the pyrene core by chemical oxidation or installation of a thiadiazole dioxide heterocycle results in the formation of D-A-D chromophores with absorption bands up to 900 nm and LUMO energy levels of approximately -4.1 eV vs. vacuum. [ABSTRACT FROM AUTHOR]