Light- and Temperature-Controlled Hybridization, Chiral Induction and Handedness of Helical Foldamers.

Helical foldamers have attracted much attention over the last decades given their resemblance to certain biomacromolecules and their potential in domains as different as pharmaceutics, catalysis and photonics. Various research groups have successfully controlled the right- or left- handedness of these oligomers by introducing stereogenic centers through covalent or non-covalent chemistry. However, developing helical structures whose handedness can be reversibly switched remains a major challenge for chemists.

Intermolecular Anionic Mixed-Valence and π-Dimer Complexes of ortho-Pentannulated Bisazacoronene Diimide.

This study reports the serendipitous discovery of intermolecular anionic mixed-valence (MV) and π-dimer species in ortho-pentannulated BisAzaCoroneneDiimides (BACDs) during their electrochemical reduction in a non-aqueous solvent. A library of nitrogen-containing extended PDIs was synthesized via an aza-benzannulation reaction followed by a Pd-catalysed ortho-pentannulation reaction. Ortho-pentannulated BACDs revealed strong aggregation abilities in solution.

Heavy-atom-free π-twisted photosensitizers for fluorescence bioimaging and photodynamic therapy.

As the field of preclinical research on photosensitizers (PSs) for anticancer photodynamic therapy (PDT) continues to expand, a focused effort is underway to develop agents with innovative molecular structures that offer enhanced targeting, selectivity, activation, and imaging capabilities. In this context, we introduce two new heavy-atom-free PSs, DBXI and DBAI, characterized by a twisted π-conjugation framework. This innovative approach enhances the spin-orbit coupling (SOC) between the singlet excited state (S) and the triplet state (T), resulting in improved and efficient intersystem crossing (ISC).

Designing Dual-State and Aggregation-Induced Emissive Luminogens from Lignocellulosic Biosourced Molecules.

Utilizing lignocellulosic biosourced platforms, we synthesized novel cyanostilbene (CS) derivatives featuring the 3,4-dimethoxyphenyl moiety. These derivatives were investigated for their emission properties in both solution and solid states. The two simple CS derivatives exhibit very weak luminescence in solution but significant luminescence in the solid state, indicating distinct Aggregation-Induced Emission (AIE) characteristic.

Perovskite versus Nonperovskite: Modulating the Nature and Optical Properties of One-Dimensional Chiral Lead-Bromide Networks.

In the last 5 years, low-dimensional chiral metal-halide semiconductors have attracted great interest in the generation of chiroptical activity. Among this new family of materials, one-dimensional (1D) networks have appeared as the best candidates for strong circular dichroism (CD) and circularly polarized luminescence (CPL). Here, we present a new family of 1D chiral lead-bromide materials prepared from organic //-1-hydroxypropyl-2-ammonium (//-HP2A) cations.

Driving Triplet State Population in Benzothioxanthene Imide Dyes: Let's twist!

Controlling the formation of photoexcited triplet states is critical for many (photo)chemical and physical applications. Here, we demonstrate that a permanent out-of-plane distortion of the benzothioxanthene imide (BTI) dye promotes intersystem crossing by increasing spin-orbit coupling. This manipulation was achieved through a subtle chemical modification, specifically the bay-area methylation.

Chiral Truxene-Based Self-Assembled Cages: Triple Interlocking and Supramolecular Chirogenesis.

Incorporating chiral elements in host-guest systems currently attracts much attention because of the major impact such structures may have in a wide range of applications, from pharmaceuticals to materials science and beyond. Moreover, the development of multi-responsive and -functional systems is highly desirable since they offer numerous benefits. In this context, we describe herein the construction of a metal-driven self-assembled cage that associates a chiral truxene-based ligand and a bis-ruthenium complex.

Tuning the Solid State Luminescence of Benzofuran-Cyanostilbenes by Functionalization with Electron Donors or Acceptors.

Three series of linear extended benzofuran derivatives associating cyanovinyl unit and electron withdrawing systems such as paracyanophenyl (series 1) and pentafluorophenyl (series 2) units or the electron donor 3,4-dimethoxyphenyl (series 3) moiety have been prepared. The donor character of the benzofuran part is adjusted either without modifying the conjugation by adding electron-donating methoxy groups to positions 5 and 6 of the benzofuran (compounds BF2 and BF3) or by increasing the extension of the conjugation with the naphthofuran unit (BF4), and by the insertion of a furan ring between the benzofuran and the cyanovinylene bond (BF5). While most of the compounds show very low emission in solution, microcrystalline powders of almost all compounds show middle at strong emissions under excitation at 350-400 nm with emission colors ranging from blue - green to red.

Chemistry in the Molten State: Opportunities for Designing and Tuning the Emission Properties of Halide Perovskites.

A series of monolayered lead halide hybrid perovskites (HOC(CH)NH)PbX, named (C)PbX ( = 4-6, X = Cl, Br), exhibiting a low congruent melting temperature () ( = 130 °C for (C4)PbBr), high stability in the molten state, and whitish type emission, are reported. From the synthesis in the molten state, rare solid solutions of mixed organic cations (CC')PbX (, ' = 4-6; X = Cl, Br; 0 ≤ ≤1) as well as solid solutions of mixed halides (C)Pb(XX') ( = 4-6; X, X' = Cl, Br; 0 ≤ ≤1) have been prepared and characterized (thermal behavior, powder X-ray diffraction (PXRD), photoluminescence properties). The impact of substitutions is significant on the thermal properties, lowering the down to 100 °C for (C4)Pb(BrCl).

A new G-quadruplex-specific photosensitizer inducing genome instability in cancer cells by triggering oxidative DNA damage and impeding replication fork progression.

Photodynamic therapy (PDT) ideally relies on the administration, selective accumulation and photoactivation of a photosensitizer (PS) into diseased tissues. In this context, we report a new heavy-atom-free fluorescent G-quadruplex (G4) DNA-binding PS, named DBI. We reveal by fluorescence microscopy that DBI preferentially localizes in intraluminal vesicles (ILVs), precursors of exosomes, which are key components of cancer cell proliferation.

Synthesis of 1,6/7-(NO ) -Perylenediimide and 1,6/7-(NH ) -Perylenediimide as Regioisomerically Pure Materials.

The use of perylenediimide (PDI) building blocks in materials for organic electronic is of considerable interest. This popular n-type organic semiconductor is tuned by introducing peripheral groups in their ortho and bay positions. Such modifications radically alter their optoelectronic properties.

Site-selected thionated benzothioxanthene chromophores as heavy-atom-free small-molecule photosensitizers for photodynamic therapy.

Photodynamic therapy is a clinically approved anticancer modality that employs a light-activated agent (photosensitizer) to generate cytotoxic reactive oxygen species (ROS). There is therefore a growing interest for developing innovative photosensitizing agents with enhanced phototherapeutic performances. Herein, we report on a rational design synthetic procedure that converts the ultrabright benzothioxanthene imide (BTI) dye into three heavy-atom-free thionated compounds featuring close-to-unit singlet oxygen quantum yields.

Tweaking the Optoelectronic Properties of S-Doped Polycyclic Aromatic Hydrocarbons by Chemical Oxidation.

Peri-thiaxanthenothiaxanthene, an S-doped analog of peri-xanthenoxanthene, is used as a polycyclic aromatic hydrocarbon (PAH) scaffold to tune the molecular semiconductor properties by editing the oxidation state of the S-atoms. Chemical oxidation of peri-thiaxanthenothiaxanthene with H O led to the relevant sulfoxide and sulfone congeners, whereas electrooxidation gave access to sulfonium-type derivatives forming crystalline mixed valence (MV) complexes. These complexes depicted peculiar molecular and solid-state arrangements with face-to-face π-π stacking organization.

From Zero- to One-Dimensional, Opportunities and Caveats of Hybrid Iodobismuthates for Optoelectronic Applications.

The association of the electron acceptor 4,4'-amino-bipyridinium (AmV) dication and BiI in an acidic solution affords three organic-inorganic hybrid materials, (AmV)(BiI) (), (AmV)(BiI) (), and (AmV)BiI (), whose structures are based on isolated BiI and BiI anion clusters in and , respectively, and on a one-dimensional (1D) chain of -connected corner-sharing octahedra in . In contrast with known methylviologen-based hybrids, these compounds are more soluble in polar solvents, allowing thin film formation by spin-coating. (AmV)BiI exhibits a broad absorption band in the visible region leading to an optical bandgap of 1.

Exciton Coupling in Redox-Active Salen based Self-Assembled Metallacycles.

The incorporation of a redox-active nickel salen complex into supramolecular structures was explored via coordination-driven self-assembly with homobimetallic ruthenium complexes (bridged by oxalato or 5,8-dihydroxy-1,4-naphthoquinato ligands). The self-assembly resulted in the formation of a discrete rectangle using the oxalato complex and either a rectangle or a catenane employing the larger naphthoquinonato complex. The formation of the interlocked self-assembly was determined to be solvent and concentration dependent.

Reversible pH-Controlled Catenation of a Benzobisimidazole-Based Tetranuclear Rectangle.

The development of methodologies to control on demand and reversibly supramolecular transformations from self-assembled metalla-structures requires the rational design of architectures able to answer to an applied stimulus. While solvent or concentration changes, light exposure or addition of a chemical have been largely explored to provide these transformations, the case of pH sensitive materials is less described. Herein, we report the first example of a pH-triggered dissociation of a coordination-driven self-assembled interlocked molecular link.

Conservation of structural arrangements and 3 : 1 stoichiometry in a series of crystalline conductors of TMTTF, TMTSF, BEDT-TTF, and chiral DM-EDT-TTF with the oxo-bis[pentafluorotantalate(v)] dianion.

The occurrence of isostructural conducting radical cation salts of diversely substituted tetrathiafulvalene (TTF) precursors with the same anion is most often limited to very similar derivatives such as tetramethyl-tetrathiafulvalene (TMTTF) and tetramethyl-tetraselenafulvalene (TMTSF). Here we show that the use of the oxo-bis[pentafluorotantalate(v)] dianion [TaFO] affords upon electrocrystallization of TMTTF, TMTSF, bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF), racemic dimethyl-ethylenedithio-tetrathiafulvalene (()-DM-EDT-TTF), and enantiopure (,)-DM-EDT-TTF a series of mixed valence crystalline radical cation salts with the same 3 : 1 stoichiometry. The donor layers show similar features in the five materials, such as alternation of trimeric units within stacks which arrange in parallel columns of β-type.

Investigation of the K[Fe(CN)]-Mediated Mono- and Bis-Palladium-Catalyzed Cyanation of the Benzothioxanthene Core.

The pallado-catalyzed cyanation of benzothioxanthene imide () derivatives is explored herein. Once optimized on the monobromo , mild reaction conditions were successfully applied to the dibromo derivative affording two regioisomers that have been isolated and structurally solved. Additional hydrogen-deuterium exchange experiments were carried out to support a proposed mechanism involving the formation of a five-membered palladacycle intermediate in the bay area.

Exploring the Electronic Properties of Extended Benzofuran-Cyanovinyl Derivatives Obtained from Lignocellulosic and Carbohydrate Platforms Raw Materials.

Two series of linear extended benzofuran derivatives associating cyanovinyl unit and phenyl or furan moieties obtained from benzaldehyde-lignocellulosic (Be series) or furaldehyde -saccharide (Fu series) platforms were prepared in order to investigate their emission and electrochemical properties. For the fluorescence in solution and solid states, contrasting results between the two series were demonstrated. For Be series a net aggregation induced emission effect was observed with high fluorescence quantum yield for the solid state.

Synthesis, characterization and use of benzothioxanthene imide based dimers.

The synthesis of benzothioxanthene imide based dimers is reported herein. Subtle chemical modifications were carried out and their impact on the optical and electrochemical properties was investigated for a better structure-property relationship analysis. The icing on the cake was that these new structures were used as light emitting materials for the fabrication and demonstration of the first BTXI-based OLEDs.

Desymmetrization of Perylenediimide Bay Regions Using Selective Suzuki-Miyaura Reactions from Dinitro Substituted Derivatives.

Bay decoration of perylenediimide (PDI) is an attractive approach for tuning the optoelectronic properties of the dye as well as breaking backbone planarity, which provides the possibility of preventing the undesired formation of aggregates. This is usually performed through successive bis-bromination of PDI and pallado-catalyzed cross-coupling, which leads to symmetric triads. We now describe an efficient synthetic strategy for desymmetrization of the accepting PDI core by starting from its bis-nitration.

Triphenylamine/Tetracyanobutadiene-Based π-Conjugated Push-Pull Molecules End-Capped with Arene Platforms: Synthesis, Photophysics, and Photovoltaic Response.

π-Conjugated push-pull molecules based on triphenylamine and 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) have been functionalized with different terminal arene units. In solution, these highly TCBD-twisted systems showed a strong internal charge transfer band in the visible spectrum and no detectable photoluminescence (PL). Photophysical and theoretical investigations revealed very short singlet excited state deactivation time of ≈10 ps resulting from significant conformational changes of the TCBD-arene moiety upon photoexcitation, opening a pathway for non-radiative decay.

Non-Symmetrical Sterically Challenged Phenanthroline Ligands and Their Homoleptic Copper(I) Complexes with Improved Excited-State Properties.

A strategy is presented to improve the excited state reactivity of homoleptic copper-bis(diimine) complexes CuL by increasing the steric bulk around Cu whereas preserving their stability. Substituting the phenanthroline at the 2-position by a phenyl group allows the implementation of stabilizing intramolecular π stacking within the copper complex, whereas tethering a branched alkyl chain at the 9-position provides enough steric bulk to rise the excited state energy E . Two novel complexes are studied and compared to symmetrical models.

Nanoscale rotational dynamics of four independent rotators confined in crowded crystalline layers.

We report a study where Car-Parrinello molecular dynamics simulations and variable-temperature (30-300 K) H spin-lattice relaxation time experiments nicely complement each other to characterize the dynamics within a set of four crystalline 1,4-diethynylbicyclo[2.2.2]octane (BCO) rotors assembled in the metal-organic rotor, {Li(CO-Ph-BCO-py)(HO)}·2DMF.