Transamination of Zwitterionic Quinones with Polyamines: The Carbon Bridge Matters.

The one-pot transamination reactions on a zwitterionic benzoquinonemonoimine yield either a quinoxaline derivative or bis-zwitterionic macrocycles, depending on the number of carbon atoms bridging primary polyamines. These latter products, featuring two confined donor cavities, are the result of a [2 + 2] condensation without the need for template effect or high dilution conditions.

Two-step access to bis--perfluoroalkyl-corroles towards -perfluoroacyl-ABC-corroles.

A solventless and acid-catalyzed condensation of -perfluoroalkyl-dipyrromethanes with selected benzaldehydes was used to prepare ten different bilanes that were isolated before their oxidation into -AB-corroles bearing two -perfluoroalkyl groups. Macrocycles bearing long chains (CF or CF) are key precursors to afford ABC-corroles having a -acyl substituent when subjected to a mild and basic hydrolysis affecting one of the alkyl substituents.

Breaking Azacalix[4]arenes into Induline Derivatives.

Tetraamino-tetranitro-azacalixarene is at the crossroad of two different families of compounds depending on the conditions and the agent used to reduce the NO groups: (1) azacalixphyrin in neutral medium, or (2) phenazinium of type in acidic medium. The key role of the N-substituted amino functions at the periphery is highlighted by investigating octaaminoazacalixarene as a model compound, and by using the corresponding tetrahydroxy-tetranitro-azacalixarene as a precursor, which behaves differently.

A Strategy to Design Substituted Tetraamino-Phenazine Dyes and Access to an NIR-Absorbing Benzoquinonediimine-Fused Quinoxaline.

The straightforward access to N- or C-substituted dinitro-tetraamino-phenazines () is enabled in oxidative conditions via formation of two intermolecular C-N bonds from accessible 5-nitrobenzene-1,2,4-triamine precursors. The photophysical studies revealed green absorbing and orange-red emitting dyes, with enhanced fluorescence in the solid state. Further reduction of the nitro functions led to the isolation of a benzoquinonediimine-fused quinoxaline (), which undergoes diprotonation to form a dicationic coupled trimethine dye absorbing beyond 800 nm.

Deciphering Electronic and Structural Effects in Copper Corrole/Graphene Hybrids.

Non-covalent hybrid materials based on graphene and A -type copper corrole complexes were computationally investigated. The corroles complexes contain strong electron-withdrawing fluorinated substituents at the meso positions. Our results show that the non-innocent character of corrole moiety modulates the structural, electronic, and magnetic properties once the hybrid systems are held.

Effect of the electron donating group on the excited-state electronic nature and epsilon-near-zero properties of curcuminoid-borondifluoride dyes.

Epsilon-near-zero (ENZ) properties have been reported in organic molecular films. In particular, cyanine and squaraine films have been shown to exhibit ENZ properties in the visible spectral region with a strong 3 order nonlinear optical response near the ENZ spectral region. Noting both cyanine and squaraine belong to the polymethine family, a series of six curcuminoid borondifluoride (Curc) derivatives were developed to examine whether such a polymethine character is positively correlated with the ENZ property of the organic films.

Synthesis and Electron Accepting Properties of Two Di(benz[]indenone)-Fused Tetraazaanthracene Isomers.

We designed and synthesized a novel di(benz[]indenone)-fused tetraazaanthracene derivative and isolated its two isomers, and , having and configurations, respectively. Their structure and that of the condensation reaction intermediates, - and -, were fully characterized using one- and two-dimensional nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction. The optical and electronic properties of and were investigated using ultraviolet-visible absorption and fluorescence spectroscopies, cyclic voltammetry, and time-dependent density functional theory calculations.

Switching from Single to Simultaneous Free-Radical and Anionic Polymerization with Enamine-Based Organic Electron Donors.

Although most monomers can polymerize through different propagation pathways, polymerization-initiating systems that can switch from one mode to another are rare. In this study, we demonstrate that enamine-based organic electron donors (OEDs) constitute the first systems able to initiate either free-radical or anionic polymerization under simple, mild, and safe conditions. While direct electron-transfer reduction of monomers by OEDs results in the initiation of anionic chain-growth polymerization, introduction of a competing oxidant with a higher reduction potential than the monomer switches the former anionic propagation to a clean radical-propagation process.

Stabilization of a 12-π electrons diamino-benzoquinonediimine tautomer.

The first example of diamino-benzoquinonediimine bearing both electron-donating and electron-withdrawing groups on the same 6-π electron subunit was synthesized using a straightforward one pot strategy. Photophysical analysis and theoretical calculations demonstrate that this unique substitution pattern is efficient to favour the establishment of a single tautomeric structure in solution.

Small Panchromatic and NIR Absorbers from Quinoid Zwitterions.

The transamination of oxoaminobenzoquinonemonoimine (BQI derivatives), an unconventional zwitterionic quinone, allows isolation of a series of compounds featuring electron-donating aryl auxochromes. The substitution has a very strong impact on the electrochemical and optical features, which is rationalized by theoretical calculations. Protonation and alkylation of the BQIs toward the corresponding cations lead to surprising red-shifts of the absorption, especially in the instance of the most electron-rich dyes that exhibit panchromatic absorption spanning up to the near-infrared (NIR) region, a remarkable achievement for such small molecules.

Exciton Interactions, Excimer Formation, and [2π+2π] Photodimerization in Nonconjugated Curcuminoid-BF Dimers.

We describe the synthesis of a series of covalently linked dimers of quadrupolar curcuminoid-BF dyes and the detailed investigation of their solvent-dependent spectroscopic and photophysical properties. In solvents of low polarity, intramolecular folding induces the formation of aggregated chromophores, the UV/Vis absorption spectra of which display the optical signature characteristic of weakly-coupled H-aggregates. The extent of folding and, in turn, of ground-state aggregation is strongly dependent on the nature of the flexible linker.

Fused bis-azacalixphyrin that reaches NIR-II absorptions.

The fusion of two azacalixphyrin cycles absorbing in the NIR-I domain moves the absorption properties beyond 1000 nm, towards the second biological transparency window (NIR-II). This new type of NIR-II dye was synthesised through the intermediate preparation of a rare example of bis-tetra-azacalix[4]arene where the two macrocycles share a common aromatic unit.

Azacalixquinarenes: From Canonical to (Poly-)Zwitterionic Macrocycles.

Azacalixquinarenes, a new family of macrocycles composed of diaminobenzoquinone diimine units linked by dinitrobenzene rings, are synthesized by selective oxidation of the parent azacalixarenes. Crystallographic analyses of two compounds demonstrated the presence of canonical (uncharged) and zwitterionic quinones within a single structure. The electron-withdrawing nature of the dinitrobenzene moieties can trigger the intramolecular H-transfer that generates zwitterionic ground-state quinones.

Azacalixphyrins as NIR photoacoustic contrast agents.

Near-infrared (NIR) azacalixphyrins bearing aryl substituents strongly impacting the physico-chemical properties of the macrocycles were designed, enabling hyperchromic and bathochromic shifts of the absorption compared to their N-alkylated analogues. This engineering enhances the photoacoustic response under NIR excitation, making azacalixphyrins promising organic contrast agents that reach the 800-1000 nm range.

Hetero-Bimetallic Effect as a Route to Access Multinuclear Complexes.

We report the synthesis of a key mononuclear intermediate complex based on a quinoid ligand and its further metalation to afford the corresponding hetero-bimetallic compound that revealed unique properties. An unprecedented hetero-bimetallic effect in coordination chemistry could be indeed observed and exploited to prepare, through selective ligand exchange, a tetranuclear complex (Pd-Ni-Ni-Pd) absorbing light up to the far-red region. Most importantly, we describe here to the best of our knowledge the first use of bischelating ligand for ligand exchange, and this approach can be considered as a new route for incorporating planar units to access multi-heteronuclear complexes.

Di- vs. tetra-substituted quinonediimines: a drastic effect on coordination chemistry.

We describe the first isolation of N,N'-disubstituted benzoquinonediimines (QDIs) 2 which revealed drastically different properties compared to N,N',N'',N'''-tetrasubstituted QDIs 1 due to the absence of N-substituents in the "upper part" of the molecule. Three major differences could be highlighted thanks to the present joint experimental and theoretical investigation: (1) the metalation with different metal precursors revealed a specific behaviour in coordination chemistry giving access to novel complexes with unprecedented stoichiometry and remarkable absorption properties. More specifically, a new monoplatinum complex that is able to absorb light from the UV up to the NIR region because of its unique delocalization pathway across the metal centre was obtained; (2) this new class of di-substituted QDIs showed an exceptionally broad pK range (ΔpK∼ 8) that could be explained by the possible tuning of the basicity of each imine which is now attainable; (3) these quinones could be used as reagents in organic synthesis to form the previously unknown N,N',N'',N'''-tetrasubstituted QDIs with tuneable substituents (aryl vs.

Boron difluoride hemicurcuminoid as an efficient far red to near-infrared emitter: toward OLEDs and laser dyes.

A hemicurcuminoid boron difluoride complex is used as an emitter in organic light-emitting diodes, showing far red/near-infrared electroluminescence with an external quantum efficiency as high as 2.1%. This dye blended in CBP thin films shows amplified spontaneous emission with a threshold of 22 μJ cm at 750 nm, making this compound attractive for organic semiconductor lasers operating in the near-infrared region.

Transamination at the Crossroad of the One-Pot Synthesis of N-Substituted Quinonediimines and C-Substituted Benzobisimidazoles.

A green and very efficient synthesis of N-substituted benzoquinonediimines or C-substituted benzo-bis(imidazole) derivatives is described under similar conditions. The different reaction pathway is only controlled by the nature of the primary amines, which tunes the reactivity of the intermediates.

Polymerization Initiated by Organic Electron Donors.

Polymerization reactions with organic electron donors (OED) as initiators are presented herein. The metal-free polymerization of various activated alkene and cyclic ester monomers was performed in short reaction times, under mild conditions, with small amounts of organic reducing agents, and without the need for co-initiators or activation by photochemical, electrochemical, or other methods. Hence, OED initiators enabled the development of an efficient, rapid, room-temperature process that meets the technical standards expected for industrial processes, such as energy savings, cost-effectiveness and safety.

1,3-Alternate Tetraamido-Azacalix[4]arenes as Selective Anion Receptors.

Six tetraaza[1.1.1.

meso-Ester Corroles.

The introduction of ester groups on the 5- and 15-meso positions of corroles stabilizes them against oxidation and induces a redshift of their absorption and emission spectra. These effects are studied through the photophysical and electrochemical characterization of up to 16 different 5,15-diester corroles, in which the third meso position is free or occupied by an aryl group, a long alkyl chain, or an ester moiety. Single-crystal X-ray structure analysis of five 5,15-diestercorroles and DFT and time-dependent DFT calculations show that the strong electron-withdrawing character of the 5,15 ester substituents is reinforced by their π overlap with the macrocyclic aromatic system.

An efficient synthesis of porphyrins with different meso substituents that avoids scrambling in aqueous media.

We have developed new conditions that afford regioisomerically pure trans-A2B2-, A3B-, and trans-AB2C-porphyrins bearing aryl and arylethynyl substituents. The porphyrins were prepared by the acid-catalyzed condensation of dipyrromethanes with aldehydes followed by oxidation with p-chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Optimal conditions for the condensation were identified after examining various reaction parameters such as solvent composition, acid concentration, and reaction time.

Extendable nickel complex tapes that reach NIR absorptions.

Stepwise synthesis of linear nickel complex oligomer tapes with no need for solid-phase support has been achieved. The control of the length in flat arrays allows a fine-tuning of the absorption properties from the UV to the NIR region.