The establishment of ligand field (LF) symmetry around lanthanoid (Ln(III)) centres is of paramount importance to understand factors that govern magnetization relaxation in singlemolecule magnets (SMMs). We investigated a luminescent mononuclear Dy(III) compound [Dy(BA)₄] (pip) (1), where pip is a piperidinium cation and BA is a benzoylacetonate ligand. The stoichiometric compound exhibits zero-field SMM characteristics, quantum tunneling of magnetization (QTM) dominates magnetization relaxation. In the diluted version of the compound (1@Y), the QTM is mitigated, Raman and Orbach processes are involved in the relaxation. The effective energy barrier (Ueff = 53.61 cm-1 ; HDC = 0 Oe) estimated for magnetization relaxation is comparable with the LF splitting (ΔE = 57.2 cm-1) between the ground and first excited Kramers doublets (KDs) determined from the 4 F9/2→ 6 H15/2 Dy(III)based transition recorded at 2.4 K. By analysing the emission spectrum of the isostructural Eu(III) analogue as spectroscopic probe for site symmetry, the LF symmetry around the Dy(III) centre is assigned as C₂ᵥ. The close proximity (178 cm-1) of the triplet state of the ligand and 4 F9/2 state of the Dy(III) facilitates back energy transfer, thereby rendering 1 emissive only at cryogenic temperatures. The predictive accuracy of the complete active space spin-orbit configuration interaction (CASOCI) method is benchmarked against the experimental emission profile. Overall, we propose a strategy to assign effective LF symmetry around Dy(III), establish magneto-optical correlations, and provide a comprehensive analysis of emission process of 1.

The triscatecholatotitanate(IV) anion (Ti(Cat)32-) interacts with various imidazolium cations (2-7) to generate salts (A-F) where the titanium dianion complex is associated with two imidazolium monocations. Two types of cation form these salts; species 2-4 bear methoxy groups, whereas one, two or three dodecyl linear alkyl chains are incorporated within 5, 6 and 7, respectively. These salts were characterized in solution by 1H NMR and the crystal structure of salt C containing the complex Ti(Cat)32- with two imidazolium cations substituted by two methoxy groups (3) was established. Differential scanning calorimetry (DSC) measurements and polarized optical microscopy (POM) observations attest to the thermotropic liquid crystal behavior of the salts, where long alkyl chains are present in salts containing imidazolium cations (5-7). The data extracted from the small- and wide-angle X-ray scattering (SWAXS) analysis of salts 5-7 enable the proposal of the supramolecular organisations of the three mesophases. This organisation is dependent on the number of alkyl chains that compose the imidazolium cations.

Charge mobility plays a crucial role in determining the performance of organic semiconducting devices. Organic semiconductors (OSCs) based on donor-acceptor (D-A) small molecules generally have planar backbones that facilitate charge transport. However, their hole transport property in thin film transistors (TFTs) still required to be further improved, and simultaneously achieving electron transport alongside hole transport remains a great challenge due to the presence of electron traps on the substrate surface. In this study, an isoindigo-based oligothiophene that is a D-A small molecule, was synthesized and employed as an active layer in TFTs. The impact of thermal annealing on the structure, morphology and charge transport properties of its thin films was investigated. By implementing a facile surface engineering, electron traps on the SiO2 dielectric surface were effectively eliminated. As a result, the charge transport behavior in the TFTs was successfully transformed from solely p-type to ambipolar characteristics. This accomplishment holds great significance for the advancement of optoelectronic devices in which both p-type and n-type conduction are harnessed.

Current biodegradable materials are facing many challenges when used for the design of implantable devices because of shortcomings such as toxicity of crosslinking agents and degradation derivatives, limited cell adhesion, and limited immunological compatibility. Here, a class of materials built entirely of stable protein is designed using a simple protocol based on salt-assisted compaction of albumin, breaking with current crosslinking strategies. Salt-assisted compaction is based on the assembly of albumin in the presence of high concentrations of specific salts such as sodium bromide. This process leads, surprisingly, to water-insoluble handable materials with high preservation of their native protein structures and Young's modulus close to that of cartilage (0.86 MPa). Furthermore, these materials are non-cytotoxic, non-inflammatory, and in vivo implantations (using models of mice and rabbits) demonstrate a very slow degradation rate of the material with excellent biocompatibility and absence of systemic inflammation and implant failure. Therefore, these materials constitute promising candidates for the design of biodegradable scaffolds and drug delivery systems as an alternative to conventional synthetic degradable polyester materials.

A series of novel conjugated semiconducting polymers based on the unsubstituted thiazolo[5,4‐ d ]thiazole (TzTz) unit is synthesized using atom‐economic and environmentally friendly direct (hetero)arylation polymerization (DHAP). The versatility of the proposed polymerization conditions, employing a non‐chlorinated and moderately toxic solvent and cooperative palladium/copper bimetallic catalytic system, is demonstrated through the use of seven comonomers with varying electron‐withdrawing strength: 2,2′‐bithiophene (BT), 6,7‐difluoroquinoxaline (Qx), thieno[3,4‐ c ]pyrrole‐4,6(5H)‐dione (TPD), 5,6‐difluorobenzo[ c ][1,2,5]thiadiazole (BTD), isoindigo (IID), para‐azaquinodimethane (AQM) and 2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (DPP). The resulting TzTz‐based copolymers exhibit optical bandgaps between 1.5 and 2.0 eV with HOMO/LUMO energy levels spanning from −5.2/−3.3 eV to −5.4/−3.9 eV. They all show satisfactory thermal stability for electronic applications (Td = 300−360 °C). Notably, TzTz‐based copolymers are observed they generally exhibit improved backbone planarity and deeper LUMO levels than their thiophene derivatives. A synthesis tool to finely lower the LUMO levels of next‐generation A‐A’ copolymers in view of increasing the performance and air‐stability of doped organic electronics is believed to be provided by this work.

Spin-state switching in iron(II) complexes composed of ligands featuring moderate ligand-field strength-for example, 2,6-bi(1H-pyrazol-1-yl)pyridine (BPP)-is dependent on many factors. Herein, we show that spin-state switching in isomeric iron(II) complexes composed of BPP-based ligands-ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CH2OCOMe, L2)-is dependent on the nature of the substituent at the BPP skeleton. Bi-stable spin-state switching-with a thermal hysteresis width (ΔT1/2) of 44 K and switching temperature (T1/2) = 298 K in the first cycle-is observed for complex 1·CH3CN composed of L1 and BF4- counter anions. Conversely, the solvent-free isomeric counterpart of 1·CH3CN-complex 2a, composed of L2 and BF4- counter anions-was trapped in the high-spin (HS) state. For one of the polymorphs of complex 2b·CH3CN-2b·CH3CN-Y, Y denotes yellow colour of the crystals-composed of L2 and ClO4- counter anions, a gradual and non-hysteretic SCO is observed with T1/2 = 234 K. Complexes 1·CH3CN and 2b·CH3CN-Y also underwent light-induced spin-state switching at 5 K due to the light-induced excited spin-state trapping (LIESST) effect. Structures of the low-spin (LS) and HS forms of complex 1·CH3CN revealed that spin-state switching goes hand-in-hand with pronounced distortion of the trans-N{pyridyl}-Fe-N{pyridyl} angle (ϕ), whereas such distortion is not observed for 2b·CH3CN-Y. This observation points that distortion is one of the factors making the spin-state switching of 1·CH3CN hysteretic in the solid state. The observation of bi-stable spin-state switching with T1/2 centred at room temperature for 1·CH3CN indicates that technologically relevant spin-state switching profiles based on mononuclear iron(II) complexes can be obtained.

This paper describes the synthesis and characterization of liquid crystals based on loop-shaped cationic copper(I) complexes of a multidentate ligand. Their synthesis involves the one-pot reaction of an alkyloxy-decorated pyridine-aldehyde unit with a diamine (2,2'-(ethylenedioxy)bis(ethylamine)) spacer to form in situ a pyridine-imine quadridentate-N4-donor ligand, L, which is able to chelate a copper(I) center associated with various noncoordinating anions. All of these compounds were characterized by NMR, IR, and electronic absorption spectroscopy, and more particularly by X-ray diffraction and mass spectroscopy, enabling unambiguous assignment of the [ML]+ mononuclear nature of the cationic components. The presence of six flexible alkyloxy chains at each end of the ligand associated with the rigidity of the core complex causes induction of a liquid crystal state with a columnar self-organized architecture, where the columns are packed in a hexagonal two-dimensional network.

We have examined the structural and electron transport properties of a swallow-tailed N,N'-bis(1-heptyloctyl)-perylene-3,4:9,10-bis(dicarboximide) (PDI-C8,7) in thin films. A comprehensive analysis of material with the use of X-ray scattering methods evidenced the appearance of a new soft-crystalline mesophase that was induced by thermal processing of the swallow-tail PDI derivative. By combining electrical measurements with grazing-incidence wide-angle X-ray scattering (GIWAXS), we show that these morphological changes of thin films boost their charge transport in the organic field-effect transistor (OFET) configuration. The systematic device engineering of OFETs, including device architecture, thermal history, and preparation method of the active layer, resulted in a significant improvement in the electron field-effect mobility and the related performance parameters. In particular, the results demonstrate a strong improvement in the charge transport of PDI-C8,7 films in their soft-crystalline phase, which originates from the N-substitution by swallow-tails. In addition, our study demonstrates that the melt-processing route, a solvent-free and vacuum-free method for the fabrication of organic thin films, represents an efficient strategy for the fabrication of high-performance air-stable n-type OFETs.

Processes of water condensation and desublimation on solid surfaces are ubiquitous in nature and essential for various industrial applications, which are crucial for their performance. Despite their significance, these processes are not well understood due to the lack of methods that can provide insight at the nanolevel into the very first stages of phase transitions. Taking advantage of synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and environmental scanning electron microscopy (ESEM), two pathways of the frosting process from supersaturated vapors were studied in real time for substrates with different wettabilities ranging from highly hydrophilic to superhydrophobic. Within GIWAXS, a fully quantitative structural and orientational characterization of the undergoing phase transition reveals the information on degree of crystallinity of the new phase and determines the ordering at the surfaces and inside the films at the initial stages of water/ice nucleation from vapor onto the substrates. The diversity of frosting scenarios, including direct desublimation from the vapor and two-stage condensation-freezing processes, was observed by both GIWAXS and ESEM for different combinations of substrate wettability and vapor supersaturations. The classical nucleation theory straightforwardly predicts the pathway of the phase transition for hydrophobic and superhydrophobic substrates. The case of hydrophilic substrates is more intricate because the barriers in Gibbs free energy for nucleating both liquid and solid embryos are close to each other and comparable to thermal energy kBT. At that end, classical nucleation theory allows concluding a relation between contact angles for ice and water embryos on the basis of the observed frosting pathway.

The recent development of π-conjugated nanohoops in organic electronics has opened new perspectives for this family of curved materials.

Single-ether side chains allow modulation of the oxygen position. The further the oxygen atom is from the backbone, the more crystalline the polymer. High doping levels and ordering lead to remarkable conductivities and thermoelectric performances.

The SIRIUS beamline of Synchrotron SOLEIL is dedicated to X-ray scattering and spectroscopy of surfaces and interfaces, covering the tender to mid-hard X-ray range (1.1-13 keV). The beamline has hosted a wide range of experiments in the field of soft interfaces and beyond, providing various grazing-incidence techniques such as diffraction and wide-angle scattering (GIXD/GIWAXS), small-angle scattering (GISAXS) and X-ray fluorescence in total reflection (TXRF). SIRIUS also offers specific sample environments tailored for in situ complementary experiments on solid and liquid surfaces. Recently, the beamline has added compound refractive lenses associated with a transfocator, allowing for the X-ray beam to be focused down to 10 µm × 10 µm while maintaining a reasonable flux on the sample. This new feature opens up new possibilities for faster GIXD measurements at the liquid-air interface and for measurements on samples with narrow geometries.

Aqueous dispersions of organic semiconducting nanoparticles (NPs) are particularly attractive as inks for the environmentally friendly preparation of organic solar cells. The internal morphology of the NPs, which depends on their elaboration process, is a key parameter, which has a significant influence on the final morphology of the active layer and therefore its effectiveness. In the present study, core-shell (PF2:PC71BM) NPs were prepared by miniemulsion. Their internal morphology including the composition of the two phases was characterized by scanning transmission X-ray microscopy (STXM) showing a core composed of 77% PC71BM and a shell composed of 75% PF2. It was found that thermal annealing promotes PC71BM diffusion from the core to the shell, increasing its proportion in the shell from 25% to 42%. This annealing, when applied after NPs deposition by spincoating, allows partial coalescence of the NPs, reducing the roughness of the active layer, and increases electron mobility, thus demonstrating the formation of PC71BM percolation paths for electron transport. A PCE of 1.6% could thus be obtained after 10min of thermal annealing at 100°C. At higher temperature, Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS) analyses demonstrate the modification of the PF2 structuration from randomly oriented lamella after deposition to edge-on orientation after annealing, leading to an unfavorable decrease of the hole mobility in the direction perpendicular to the substrate, while increasing the hole mobility in the substrate plane. This study demonstrates the need to systematically characterize the internal morphology of NPs in order to rationalize the morphology of the active layer and optimize its properties.

Spin-state switching in iron(II) complexes composed of ligands featuring moderate ligand-field strength—for example, 2,6-bi(1H-pyrazol-1-yl)pyridine (BPP)—is dependent on many factors—examples include lattice solvent, counter anion, and substituent. Herein, we show that spin-state switching in isomeric iron(II) complexes (1·CH3CN and 2) composed of tridentate all nitrogen coordinating ligands—ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CH2OCOMe, L2)—is controlled by the nature of substituent at the fourth position of the pyridine ring of the BPP skeleton. Complex 1·CH3CN, crystallized with acetonitrile solvent, undergoes abrupt and hysteretic spin-state switching, hence bistable switching, with a thermal hysteresis width (ΔT1/2) of 44 K and switching temperature (T1/2) = 298 K in the first cycle. Conversely, the isomeric counterpart of 1·CH3CN—complex 2—crystallized with no lattice solvent; the complex was trapped in the high-spin (HS) state upon cooling from 300 K. Molecular structures of the LS and HS forms of complex 1·CH3CN revealed that spin-state switching induces a pronounced angular distortion, creating an energy barrier separating the LS and HS states. Traversing the barrier requires substantial molecular rearrangement in the presence of constraints imposed by the crystal lattice, rendering the spin-state switching of 1·CH3CN hysteretic in the solid-state. The observation of bistable spin-state switching with T1/2 centred at room temperature for 1·CH3CN as well as the attribution of pronounced angular distortion and conformational variation of the COOEt substituent as causes behind the observed hysteretic spin-state switching indicates that technologically relevant spin-state switching profiles based on mononuclear iron(II) complexes can be obtained.

Since the first applications of nanohoops in organic electronics appear promising, the time has come to go deeper into their rational design in order to reach high-efficiency materials. To do so, systematic studies dealing with the incorporation of electron-rich and/or electron-poor functional units on nanohoops have to be performed. Herein, the synthesis, the electrochemical, photophysical, thermal, and structural properties of two [4]cyclo-2,7-carbazoles, [4]C-Py-Cbz, and [4]C-Pm-Cbz, possessing electron-withdrawing units on their nitrogen atoms (pyridine or pyrimidine) are reported. The synthesis of these nanohoops is first optimized and a high yield above 50% is reached. Through a structure-properties relationship study, it is shown that the substituent has a significant impact on some physicochemical properties (eg HOMO/LUMO levels) while others are kept unchanged (eg fluorescence). Incorporation in electronic devices shows that the most electrically efficient Organic Field-Effect transistors are obtained with [4]C-Py-Cbz although this compound does not present the best-organized semiconductor layer. These experimental data are finally confronted with the electronic couplings between the nanohoops determined at the DFT level and have highlighted the origin in the difference of charge transport properties. [4]C-Py-Cbz has the advantage of a more 2D-like transport character than [4]C-Pm-Cbz, which alleviates the impact of defects and structural organization.

In this work, we describe the design and synthesis of a novel soluble conjugated molecule, CAR-TzDPP, consisting of a central diketopyrrolopyrrole core (DPP) connected to carbazole endcaps through thiazole rings. To evaluate its properties, a triazatruxene-based molecule (TAT-TzDPP) was used as a model for comparison. The electrochemical and the in-solution optical properties are in good agreement with those obtained from DFT calculations. However, the thin-film self-assemblies of CAR-TzDPP exhibited distinct differences, forming a more standard crystalline structure including insulating side-chains layers that disallowed side interactions between aromatic rings. This resulted in a reduced charge transport ability to a two-dimensional (2D) ambipolar charge transport in CAR-TzDPP, compared to the nearly isotropic unipolar charge transport in TAT-TzDPP. Despite this, CAR-TzDPP can be considered a viable alternative for device configurations requiring semiconducting pathways aligned in the substrate plane due to its simplified and high yield synthesis route, ease of processing, and reliable charge mobility in OFETs. This research highlights the significance of molecular units in small semiconducting organic molecules, not only in terms of their individual optoelectronic properties but also in terms of their self-assembly capabilities, which ultimately influence their charge transport properties.

Two-dimensional perovskites containing an organic fluorophore can be a unique emitter for light-emitting diodes (LEDs). However, external quantum efficiencies (EQEs) of fluorophore-containing perovskite LEDs reported thus far are still very low. In this study, these are able to boost the EQE to ≈10% by choosing an organic fluorophore with appropriate energy levels for the perovskite structure organization. In the fluorophore-containing perovskite LEDs, carrier transport and exciton formation take place in the perovskite's metal halide framework, thereby avoiding the direct formation of nonradiative triplet excitons on the organic fluorophores. Subsequently, the bright triplet excitons formed in the metal halide framework are transferred to form the radiative singlet states of the organic fluorophores, leading to efficient electroluminescence (EL) from the organic fluorophores regularly dispersed inside the perovskite structure. Unexpectedly higher light-outcoupling efficiency, which is caused by the light scattering in the polycrystalline perovskite layer, will be another reason for efficient EL. These findings will contribute toward the fabrication of LED-based products with high performance at a low cost.

Novel hybrid silsesquioxane-based liquid crystalline derivatives with varied lengths of spacers and tails have been synthesized by hydrosilylation reactions of octakis(dimethylsiloxy)silsesquioxane and side-on mesogens via a platinum catalyst. The thermal behavior of three types of silsesquioxane-based liquid crystals (LCs), differentiated by the molecular structure of mesogens, was investigated by differential scanning calorimetry (DSC) and polarising optical microscopy (POM). Temperature-dependent small and wide-angle X-ray scattering was used to verify liquid crystalline phases, revealing that the silsesquioxane-based derivatives formed hexagonal columnar and nematic mesophases, and the effect of the molecular structure of the mesogens and the spacer length on the formation of LC phases is discussed. This investigation demonstrated that the choice of the "side-on" attachments plays a crucial role in enhancing the emergence of the nematic phase.

A new NFA design based on the unusual BODIPY unit as the central electron accepting component is described. All derivatives exhibit low optical bandgaps, high extinction coefficients and LUMO levels deep enough to be used as NFAs.