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Formation of radical–radical cocrystals is an important step towards the design of organic ferrimagnets. We describe a simple approach to generate radical–radical cocrystals through the identification and implementation of well‐defined supramolecular synthons which favor cocrystallization over phase separation. In the current paper we implement the structure‐directing interactions of the E−E bond (E=S, Se) of dithiadiazolyl (DTDA) and diselenadiazolyl (DSDA) radicals to form close contacts to electronegative groups. This is exemplified through the preparation and structural characterization of three sets of radical cocrystals; the 2:2 cocrystal [PhCNSSN]2[MBDTA]2 (4) [MBDTA=methyl benzodithiazolyl] and the 2:1 cocrystals [C6F5CNEEN]2[TEMPO] (E=S, 5; E=Se, 6). In 4 the two types of radical are linked via bifurcated inter‐dimer δ+S⋅⋅⋅Nδ− interactions whereas 5 and 6 exhibit a set of five‐centre δ+E⋅⋅⋅Oδ− contacts (E=S, Se). [ABSTRACT FROM AUTHOR]

Formation of radical–radical cocrystals is an important step towards the design of organic ferrimagnets. We describe a simple approach to generate radical–radical cocrystals through the identification and implementation of well‐defined supramolecular synthons which favor cocrystallization over phase separation. In the current paper we implement the structure‐directing interactions of the E−E bond (E=S, Se) of dithiadiazolyl (DTDA) and diselenadiazolyl (DSDA) radicals to form close contacts to electronegative groups. This is exemplified through the preparation and structural characterization of three sets of radical cocrystals; the 2:2 cocrystal [PhCNSSN]2[MBDTA]2 (4) [MBDTA=methyl benzodithiazolyl] and the 2:1 cocrystals [C6F5CNEEN]2[TEMPO] (E=S, 5; E=Se, 6). In 4 the two types of radical are linked via bifurcated inter‐dimer δ+S⋅⋅⋅Nδ− interactions whereas 5 and 6 exhibit a set of five‐centre δ+E⋅⋅⋅Oδ− contacts (E=S, Se). SOMO wrestling: Cocrystallization of radicals requires different open‐shell molecules to interact with each other rather than themselves. This process can be driven by careful selection of favorable electrostatic interactions between molecules. [ABSTRACT FROM AUTHOR]

A series of four dimers based on the connection of two 2-(2′-Hydroxybenzofuran)benzoxazole (HBBO) subunits are described in this article. HBBO fluorophores are especially known for displaying sizable excited-state intramolecular proton transfer (ESIPT) process and a subsequent fluorescence emission stemming from a keto tautomer. Two HBBO monomers, connected through perfluoropropane, sulfonyl spacers or directly connected were synthesized and characterized, in order to assess the influence of the bridge on the photophysical properties. All HBBO monomers comprise of a benzofuranol heterocycle functionalized with an electrodonating group, either p-methoxy (OMe) or p-N,N’-dibutylamino (NBu 2 ). The studies of the optical properties in solution and in the solid-state reveal the presence of either a single keto (K ∗ ) or a dual enol/keto (E ∗ /K ∗ ) emission, depending on the electronic substitution on the benzofuranol ring but also on the electronegativity of the connecting bridge and the close environment (solvent or matrix). Structure/properties relationships confirmed the strong influence of the electronic nature of the spacer on the pK B of the aromatic amine of the benzoxazole units and consequently on the intensity of the proton transfer in the excited-state. The sulfonyl linker was found to be most electronegative spacer in the series, leading to the strongest ESIPT frustration and thus, the highest E ∗ /K ∗ intensity ratio. All dimers containing a NBu 2 moiety were responsive to protonation, leading to an enhanced acidity of the phenolic proton in each case. [ABSTRACT FROM AUTHOR]

Herein, a full investigation of the optical properties and first-principles calculations of a large series of original 2-(2′-hydroxybenzofuran)benzazole (HBBX) dyes is described. The electronic substitution on the π-conjugated core of the fluorophores and the nature of the heteroatom (O, S, N) was varied extensively to assess the necessary parameters to trigger a partial frustration of the excited-state intramolecular proton transfer (ESIPT) process, which results in the emission of both tautomers, that is, enol and keto (E* and K*). The optical properties, studied in solution and in the solid state, revealed the appearance of either an intense single K* or a dual E*/K* emission; a feature that is highly dependent on the electronic substitution (donating or accepting), the heteroelement, and the close environment. Subtle modifications of these parameters allowed the establishment of structure-property relationships that were successfully rationalized by first-principles calculations. In particular, the E*/K* emission intensity ratio was shown to be directly related to the free energies of the two emissive tautomers in the excited state. [ABSTRACT FROM AUTHOR]

Several symmetrical and unsymmetrical thiophene-functionalized diketopyrrolopyrrole chromophores bearing a bis(p-methoxyphenyl)-p-phenylamine substituent were synthesized through palladium-catalyzed cross-coupling reactions. Mono-substitution and di-substitution occur using either alkyne or borolane groups, allowing the preparation of mixed systems. The alkyne derivatives could be prepared in high yields, and are versatile building blocks for the [2+2] cycloaddition of tetracyanoethylene, leading to 1,1,4,4-tetracyanobuta-1,3-diene derivatives. These interesting push-pull molecules exhibit a rich redox activity, which is understandable in light of the behavior of appropriate reference compounds. These innovative and rationally designed scaffolds are highly colored, exhibiting high absorption coefficients and spanning an absorption range of more than 600 nm of the UV/Vis electromagnetic spectrum. [ABSTRACT FROM AUTHOR]

An in-depth electrochemical and spectroscopic characterization of triphenylamine ( TPA ), diketopyrrolopyrrole ( DPP ) and BODIPY ( BOD ) and triads of the single constituents (triad 1: TPA-DPP-TPA ; triad 2: TPA-DPP-BOD ) has been carried out by means of voltammetric (planar diffusion conditions) and in-situ UV-vis-NIR spectroelectrochemical experiments (thin layer conditions). Both triads show anodic and cathodic electron transfer reactions and clear spectroscopic signatures which can be correlated to those of the neutral and charged single components. While there is a strong electronic interaction between TPA and DPP in both triads, an electronic communication with the BOD unit seems to be absent. This is in line with the corresponding energy and charge transfer processes revealed by transient absorption measurements described in our recently published work. [ABSTRACT FROM AUTHOR]

In the present account we describe unsymmetrical triads constructed from extended borondipyrromethene (BODIPY) dyes, diketopyrrolopyrrole (DPP) dyes, and electron donor fragments based on triarylamine. The assemblages are such that each module maintains its individual optical and redox properties. The use of phenyl-alkyne-phenyl or phenyl-alkyne-thienyl spacer units is favorable for weak electronic interaction between the modules. The step-by-step linking of each module using palladium-catalyzed cross-coupling reactions provides both mono- and disubstituted derivatives, the latter obtained by passing in particular through a pivotal monosubstituted DPP building block with a reactive bromo substituent. Thus, grafting of a second dye occurs in a controlled manner, providing the target triads in good yields. This protocol allows also the synthesis of key intermediates and dyads, which appear useful for the understanding of the electrochemical and spectroscopic properties. All the dyes exhibit redox and optical properties suitable for cascade energy transfer and photoinduced electron transfer processes in appropriate solvents. [ABSTRACT FROM AUTHOR]

The preparation of highly water-soluble and strongly fluorescent diketopyrrolopyrrole (DPP) dyes using an unusual taurine-like sulfonated linker has been achieved. Exchanging a phenyl for a thienyl substituent shifts the emission wavelength to near λ=600 nm. The free carboxylic acid group present in these new derivatives was readily activated and the dyes were subsequently covalently linked to a model protein (bovine serum albumin; BSA). The bioconjugates were characterized by electronic absorption, fluorescence spectroscopy and MALDI-TOF mass spectrometry, thus enabling precise determination of the labeling density (ratio DPP/BSA about 3 to 8). Outstanding values of fluorescence quantum yield (30 % to 59 %) for these bioconjugates are obtained. The photostability of these DPP dyes is considerably greater than that of fluorescein under the same irradiation conditions. Remarkably low detection limits between 80 and 300 molecules/μm2 were found for the BSA bioconjugates by fluorescence imaging with a epifluorescence microscope. [ABSTRACT FROM AUTHOR]

The preparation of highly water-soluble and strongly fluorescent diketopyrrolopyrrole (DPP) dyes using an unusual taurine-like sulfonated linker has been achieved. Exchanging a phenyl for a thienyl substituent shifts the emission wavelength to near λ=600 nm. The free carboxylic acid group present in these new derivatives was readily activated and the dyes were subsequently covalently linked to a model protein (bovine serum albumin; BSA). The bioconjugates were characterized by electronic absorption, fluorescence spectroscopy and MALDI-TOF mass spectrometry, thus enabling precise determination of the labeling density (ratio DPP/BSA about 3 to 8). Outstanding values of fluorescence quantum yield (30 % to 59 %) for these bioconjugates are obtained. The photostability of these DPP dyes is considerably greater than that of fluorescein under the same irradiation conditions. Remarkably low detection limits between 80 and 300 molecules/μm2 were found for the BSA bioconjugates by fluorescence imaging with a epifluorescence microscope. [ABSTRACT FROM AUTHOR]

Bothsymmetrical and unsymmetrical α-fused dithienyl-BODIPYdyes have been prepared by oxidative ring closure induced by anhydrousFeCl3. Extension of the π-system in the fused BODIPYleads to a progressive shift to 579 and 665 nm respectively for theabsorption wavelength maxima of the mono- and difused dyes relativeto the unfused species (λabs= 502 nm). Linking suchdyes to an NIR emitting module provides a panchromatic chromophorewith a large absorption cross section in the visible range associatedwith efficient intramolecular cascade energy transfer. [ABSTRACT FROM AUTHOR]

Abstract: 3-Bromodibenzo[g,p]chrysene has been synthesized in a one-pot reaction using phenyliodine(III) bis(trifluoroacetate) (PIFA) as an oxidant and a Lewis acid. The bromo function was easily converted to the cyano, alkyne, and formyl derivatives. Bodipy dyes have either been constructed from the chrysene–aldehyde or by cross coupling reactions with the chrysene ethynyl derivatives. The linking of diketopyrrolopyrrole (DPP) fragments was realized using the chrysene–ethynyl compound or with the in situ prepared chrysene–borolane derivatives. The novel chrysene dyes are highly fluorescent in apolar solvents and were used as input energy in intramolecular energy transfer processes with covalently linked DPP or Bodipy dyes. All mixed dyes are redox active and each module is clearly identified by its redox behavior. Little electronic interaction is evidenced whatever the nature of the dyes and spacer. [Copyright &y& Elsevier]

Beim SOMO‐Ringen steigen C6F5CNSSN‐ und TEMPO‐Radikale in den Ring. In ihrer Zuschrift auf S. 1385 setzen J. M. Rawson und Mitarbeiter vorteilhafte elektrostatische Kontakte ein, um die Kokristallbildung zwischen unterschiedlichen Radikalen zu fördern. Das Konzept wird am Beispiel der Herstellung und strukturellen Charakterisierung dreier Radikal‐Kokristalle demonstriert: des 2:2‐Kokristalls [PhCNSSN]2[MBDTA]2 und der 2:1‐Kokristalle [C6F5CNEEN]2[TEMPO] (E=S, Se). [ABSTRACT FROM AUTHOR]

SOMO Wrestling Molecules of C6F5CNSSN and TEMPO radicals tangle on the Dohyō. In their Communication on page 1371, J. M. Rawson and co‐workers implement favorable electrostatic contacts to drive cocrystal formation between different radicals. The concept is exemplified through the preparation and structural characterization of three sets of radical cocrystals: the 2:2 cocrystal [PhCNSSN]2[MBDTA]2 and the 2:1 cocrystals [C6F5CNEEN]2[TEMPO] (E=S, Se). [ABSTRACT FROM AUTHOR]

A novel type of near-IR dyes (II) is developed using a novel FeCl3-promoted oxidative ring-closure of BODIPY precursors that occurs exclusively in the α,α′-position. [ABSTRACT FROM AUTHOR]

Cocrystallization of the dithiadiazolyl (DTDA) radicals p‐XC6F4CNSSN (X=F, Cl, Br, I, CN) with TEMPO afforded the 2 : 1 cocrystals [p‐XC6F4CNSSN]2[TEMPO] (1–5) whose structures all reflect a common S4⋅⋅⋅O supramolecular motif. The nature of this interaction was probed by DFT calculations (M06/aug‐cc‐pVDZ) on 1 which revealed that the enthalpy of formation of the [C6F5CNSSN]2[TEMPO] supramolecular motif from [C6F5CNSSN]2 and TEMPO is substantial (−54.0 kJ mol−1). Electronic structure calculations revealed a TEMPO‐based doublet S=1/2 configuration as the ground state with limited spin density on the DTDA rings (2.4 %). The corresponding spin quartet state is +78.9 kJ mol−1 higher in energy. An atoms‐in‐molecules analysis reveals four bond critical points (BCPs) between the TEMPO O and the DTDA S atoms as well as additional BCPs between selected DTDA S atoms and methyl H atoms of the TEMPO molecule. Herein, the structures of 2–5 are considered within the context of a hierarchical view of competing and complementary intermolecular interactions; in particular, the established supramolecular CN⋅⋅⋅S−S synthon is sacrificed in order to form the new S4⋅⋅⋅O interaction. [ABSTRACT FROM AUTHOR]

Bridge over troubled water: Highly fluorescent thiazolothiazole dyes with quantum yields of up to 60 % were prepared in a facile synthesis from dithiooxamide and various aldehydes. When adequately engineered, such dyes could be used as fluorescent bridges with other dyes. A sequence of highly efficient, intramolecular electronic‐energy‐transfer steps followed from selective illumination of the fluorescent centre in the molecular triads. [ABSTRACT FROM AUTHOR]

The ability of an unconstrained boron dipyrromethene dye to report on changes in local viscosity is improved by appending a single aryl ring at the lower rim of the dipyrrin core. Recovering the symmetry by attaching an identical aryl ring on the opposite side of the lower rim greatly diminishes the sensory activity, as does blocking rotation of the meso-aryl group. On the basis of viscosity- and temperature-dependence studies, together with quantum chemical calculations, it is proposed that a single aryl ring at the 3-position extends the molecular surface area that undergoes structural distortion during internal rotation. The substitution pattern at the lower rim also affects the harmonic frequencies at the bottom of the potential well and at the top of the barrier. These effects can be correlated with the separation of the H1,H7 hydrogen atoms. [ABSTRACT FROM AUTHOR]

We have devised new diketopyrrolopyrrole dyes soluble in polar solvents. The colors of the dyes have been changed by substituting the 3,6-phenyl residues for thiophene groups. The solubility in polar solvents has been improved by alkylation of a dimethylaminopropyne fragment with a 1,3-sultone giving rise to sulfobetaine moieties. These dyes exhibit strong and broad absorption in the visible range (488 nm for the phenyl-DPP and 578 nm for the thiophene-DPP) and intense fluorescence at, respectively, 554 nm (ΦF 0.36) and 609 nm (ΦF 0.19). The phenyl-DPP dye exhibits a maximum broad band lasing efficiency of 14.6% and a maximum narrow band lasing efficiency of 9.5% with a wide tunable range (554 nm to 616 nm) on excitation with a second harmonic of a Q-switched Nd:YAG (532 nm) laser in MeOH/H2O. The lasing efficiency remains unaffected for hours. The thiophene-DPP dye does not show any lasing action. [ABSTRACT FROM AUTHOR]