Molecular Junctions for Terahertz Switches and Detectors.

Molecular electronics targets tiny devices exploiting the electronic properties of the molecular orbitals, which can be tailored and controlled by the chemical structure and configuration of the molecules. Many functional devices have been experimentally demonstrated; however, these devices were operated in the low-frequency domain (mainly dc to MHz). This represents a serious limitation for electronic applications, although molecular devices working in the THz regime have been theoretically predicted.

Multi-State Second-Order Nonlinear Optical Switches Incorporating One to Three Benzazolo-Oxazolidine Units: A Quantum Chemistry Investigation.

This contribution employs quantum chemistry methods to describe the variations of the second nonlinear optical responses of molecular switches based on benzazolo-oxazolidine (BOX) units, connected by -linkers, along their successive opening/closing. Under the fully closed forms, all of them display negligible first hyperpolarizability () values. When one BOX is opened, which is sketched as →, a push-pull -conjugated segment is formed, having the potential to enhance and to set the depolarization ratio (DR) to its one-dimensional-like value (DR = 5).

Combining Benzazolo-Oxazolidine Twins toward Multi-state Nonlinear Optical Switches.

Molecular switches are chemical compounds exhibiting the possibility of reversible transformations between their different forms accompanied by a modification in their properties. Among these, switching of multi-addressable Benzazolo-OXazolidines (BOXs) from a closed form to an open form results in drastic modifications in their linear and nonlinear optical properties. Here, we target molecules containing two identical BOX units (DiBOX) connected by different π-conjugated linkers, and we combine synthesis, UV/visible absorption, and hyper-Rayleigh scattering (HRS) measurements, together with density functional theory (DFT) calculations.

Oxacycle-Fused [1]Benzothieno[3,2-b][1]benzothiophene Derivatives: Synthesis, Electronic Structure, Electrochemical Properties, Ionisation Potential, and Crystal Structure.

The molecular properties of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) are vulnerable to structural modifications, which in turn are determined by the functionalization of the backbone. Hence versatile synthetic strategies are needed to discover the properties of this molecule. To address this, we have attempted heteroatom (oxygen) functionalization of BTBT by a concise and easily scalable synthesis.

When Light and Acid Play Tic-Tac-Toe with a Nine-State Molecular Switch.

Combining different molecular switching functions in a single molecule is a simple strategy to develop commutable molecules featuring more than two commutation states. The present study reports on two molecular systems consisting of two indolino-oxazolidine (Box) moieties connected to an aromatic bridge (phenyl or bithiophene) by ethylenic junctions. Such systems, referenced as BiBox, are expected to show up multiaddressable and multiresponsive behaviors.

Prediction of the Synthesis of Spiro Derivatives by Double Intramolecular Aromatic Electrophilic Substitution Using Reactivity Indices.

The synthesis of heterocyclic spirobifluorene (SBF) analogs generally requires long and complicated synthetic pathways. Despite this synthetic effort, such structural modification allows the (opto)electronic properties of this remarkable three-dimensional node to be tuned especially for molecular electronic applications. For this reason, the development of a simple, robust, and efficient synthetic methodology to introduce various heterocycles in place of classical phenyl rings in the spirofluorene motif is highly and timely desirable.

Strong Solid-state Luminescence Enhancement in Supramolecular Assemblies of Polyoxometalate and "Aggregation-Induced Emission"-active Phospholium.

Two new supramolecular fluorescent hybrid materials, combining for the first time [M O ] (M=Mo, W) polyoxometalates (POMs) and aggregation-induced emission (AIE)-active 1-methyl-1,2,3,4,5-pentaphenyl-phospholium (1 ), were successfully synthesized. This novel molecular self-assembling strategy allows designing efficient solid-state emitters, such as (1) [W O ], by directing favorably the balance between the AIE and aggregation-caused quenching (ACQ) effects using both anion-π and H-bonding interactions in the solid state. Combined single-crystal X-ray diffraction, Raman, UV-vis and photoluminescence analyses highlighted that the nucleophilic oxygen-enriched POM surfaces strengthened the rigidity of the phospholium via strong C-H⋅⋅⋅O contacts, thereby exalting its solid-state luminescence.

Indolino-Oxazolidine Acido- and Photochromic System Investigated by NMR and Density Functional Theory Calculations.

Three addressable indolino-oxazolidine units connected through an isomerizable double bond to a substituted thiophene represent a smart example of a multiaddressable system whose reversible responses could be selectively activated on demand. Experimental and theoretical approaches to push forward the understanding of the system mechanism and set pathways to design optimized compounds for suitable application are here presented. NMR and UV-visible spectroscopies are used for structural and kinetic studies, while density functional theory (DFT) calculations pave the way to highlight energetic and electronic processes that are involved.

A fascinating multifaceted redox-active chelating ligand: introducing the ,'-dimethyl-3,3'-biquinoxalinium "methylbiquinoxen" platform.

To intimately combine a chelating ligand function with the numerous properties of a viologen-like redox-active centre would offer a rare possibility to design controllable multi-redox states, whose properties arise from strongly correlated phenomena between the organic ligand as well as with any metalloid coordinated centres. Such a concept previously proved to be feasible, however is not widely applicable owing to challenges in terms of synthesis, isolation, and aerial sensitivity of both the ligand and its metal complexes. Here we report the first stable example of such a redox-active molecule, ,'-dimethyl-3,3'-biquinoxalinium˙ "methylbiquinoxen, MBqn˙", which shows a rich redox chemistry and chelates a metal ion in the case of the metal complex [CdCl(MBqn)].

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2-b][1]benzothiophene.

The structural and electronic properties of four isomers of didodecyl[1]-benzothieno[3,2-b][1]benzothiophene (C12-BTBT) have been investigated. Results show the strong impact of the molecular packing on charge carrier transport and electronic polarization properties. Field-induced time-resolved microwave conductivity measurements unravel an unprecedented high average interfacial mobility of 170 cm(2) V(-1) s(-1) for the 2,7-isomer, holding great promise for the field of organic electronics.

Huge electro-/photo-/acidoinduced second-order nonlinear contrasts from multiaddressable indolinooxazolodine.

In this work, linear and nonlinear optical properties of electro-/acido-/photoswitchable indolino[2,1-b]oxazolidine derivatives were investigated. The linear optical properties of the closed and open forms have been characterized by UV-visible and IR spectroscopies associated with DFT calculations. Nonlinear optical properties of the compounds have been obtained by ex situ and in situ hyper-Rayleigh experiments in solution.

Silica-mediated synthesis of indolinooxazolidine-based molecular switches.

A novel and convenient method for the synthesis of photochromic compounds is reported here. It is based on the use of commercially available untreated silica, as an efficient catalyst to perform the condensation between indolinooxazolidine derivatives and aromatic aldehydes under solvent-free conditions. The scope and limitations of this transformation were investigated and several novel photochromic indolinooxazolidines were synthesized.

Indolinooxazolidine: a versatile switchable unit.

The design of multiresponsive systems continues to arouse a lot of interest. In such multistate/multifunctional systems, it is possible to isomerize a molecular system from one metastable state to another by application of different stimulation such as light, heat, proton, or electron. In this context, some researches deal with the design of multimode switch where a same interconversion between two states could be induced by using indifferently two or more different kind of stimuli.

Tuning a 96-well microtiter plate fluorescence-based assay to identify AGE inhibitors in crude plant extracts.

Advanced glycation end-products (AGEs) are involved in the pathogenesis of numerous diseases. Among them, cellular accumulation of AGEs contributes to vascular complications in diabetes. Besides using drugs to lower blood sugar, a balanced diet and the intake of herbal products potentially limiting AGE formation could be considered beneficial for patients' health.

Fluorescent self-assembled monolayers of umbelliferone: a relationship between contact angle and fluorescence.

Self-assembled monolayers (SAMs) that contain fluorophore units are nowadays widely used to tune surface properties and design new chemical sensor chips. It is well-known that the nature of the substrate may strongly interfere with the emission properties of the grafted molecules, but the organization of the monolayer may also have an important role. To study the influence of the SAM organization on the luminescence properties, we prepared different coumarin-based derivatives endowed with tethered chains of different lengths and elaborated the corresponding SAMs on glass slides.

Synthesis and characterization of isomerically pure anti- and syn-anthradiindole derivatives.

Synthesis, isolation, and characterization of isomerically pure syn- and anti-anthradiindole (ADI) derivatives are described. The anti- and syn-ADI structures are demonstrated by (13)C NMR spectroscopy and by single-crystal X-ray diffraction. The spectroscopic and electrochemical properties as well as the stability of these newly synthesized π-conjugated systems are evaluated and supported by quantum-chemical calculations.

Synthesis and evaluation of naphthoic acid derivatives as fluorescent probes to screen advanced glycation end-products breakers.

Advanced glycation end-products, namely AGEs, are involved in the pathogenesis of numerous diseases. If AGEs inhibitors are well-known, only few products are described as compounds able to destroy those deleterious products. In this work, we describe naphthoic acid derivatives, particularly 1-(naphthalen-1-yl)propane-1,2-dione 9, allowing the simple and rapid detection of AGEs breakers using a 96-well microplate fluorescence assay.

Tetrathiafulvalene-fused porphyrins via quinoxaline linkers: symmetric and asymmetric donor-acceptor systems.

A tetrathiafulvalene (TTF) donor is annulated to porphyrins (P) via quinoxaline linkers to form novel symmetric P-TTF-P triads 1 a-c and asymmetric P-TTF dyads 2 a,b in good yields. These planar and extended π-conjugated molecules absorb light over a wide region of the UV/Vis spectrum as a result of additional charge-transfer excitations within the donor-acceptor assemblies. Quantum-chemical calculations elucidate the nature of the electronically excited states.

Star-shaped tetrathiafulvalene-fused coronene with large pi-extended conjugation.

A tristar shaped, planar TTF-fused coronene 1 was synthesized. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV-vis-NIR spectroscopy. Thereby, a nanosized graphite fragment is largely extended in its size, supplemented with a multielectron donor functionality, and shaped to a strongly chromophoric species absorbing intensely in the visible part of the optical spectrum.

Evaluation of a new matrix-free laser desorption/ionization method through statistic studies: comparison of the DIAMS (desorption/ionization on self-assembled monolayer surface) method with the MALDI and TGFA-LDI techniques.

This work demonstrates that the desorption/ionization on self-assembled monolayer surface (DIAMS) mass spectrometry, a recent matrix-free laser desorption/ionization (LDI) method based on an organic target plate, is as statistically repeatable and reproducible as matrix assisted laser desorption ionization (MALDI) and thin gold film-assisted laser desorption/ionization (TGFA-LDI) mass spectrometries. On lipophilic DIAMS of target plates with a mixture of glycerides, repeatability/reproducibility has been estimated at 15 and 30% and the relative detection limit has been evaluated at 0.3 and 3 pmol, with and without NaI respectively.

Acido-triggered nonlinear optical switches: benzazolo-oxazolidines.

This work is the continuation of our previous experimental and theoretical studies aiming at designing efficient nonlinear optical (NLO) switches derived from the benzazolo-oxazolidine core. Here, we report the synthesis and the characterization of the linear and nonlinear optical properties of benzothiazolo[2,3-b]oxazolidine acidochromes by means of hyper-Rayleigh scattering as well as quantum chemical calculations. It is shown that these new derivatives incorporating a benzothiazole subunit exhibit very high static first hyperpolarizability values in their acido-generated form.

Fused donor-acceptor ligands in RuII chemistry: synthesis, electrochemistry and spectroscopy of [Ru(bpy)3-n(TTF-dppz)n](PF6)2.

Three ruthenium(II) polypyridine complexes of general formula [Ru(bpy)(3-n)(TTF-dppz)n](PF6)2 (n=1-3, bpy=2,2'-bipyridine), with one, two or three redox-active TTF-dppz (4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine) ligands, were synthesised and fully characterised. Their electrochemical and photophysical properties are reported together with those of the reference compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2 and [Ru(bpy)2(dppz)](PF6)2 and the free TTF-dppz ligand. All three complexes show intraligand charge-transfer (ILCT) fluorescence of the TTF-dppz ligand.