The linear and nonlinear optical (NLO) properties of two indolinooxazolidine derivatives acting as multiaddressable switches are reported. The second-order hyperpolarizability contrasts upon ...commutation between their closed and open forms are characterized using hyper-Rayleigh scattering (HRS) measurements, and rationalized by means of density functional theory and post Hartree–Fock ab initio calculations. It is evidenced that the addition of a withdrawing substituent on the indolinic subunit leads to a more effective photoinduced charge transfer while decreasing the transition energy of the S0 → S1 transition, which induces a significant enhancement of the HRS response of the open form. This substitution is however detrimental to the NLO contrast, due to the concomitant increase of the HRS response of the closed form.
The structural and electronic properties of four isomers of didodecyl1‐benzothieno3,2‐b1benzothiophene (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 cm2 V−1 s−1 for the 2,7‐isomer, holding great promise for the field of organic electronics.
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). This is observed when only one BOX is open, either for the monoBOX species (
→
) or for the diBOX (
→
) and triBOX (
→
) compounds, i.e., when the remaining BOXs stay closed. The next BOX openings have much different effects. For the diBOXs, the second opening (
→
) is associated with a decrease of
, and this decrease is tuned by controlling the conformation of the
-linker, i.e., the centrosymmetry of the whole compound because
vanishes in centrosymmetric compounds. For the triBOXs, the second opening gives rise to a
-shape compound, with a negligible change of
, but a decrease of the DR whereas, along the third opening,
remains similar and the DR decreases to the typical value of octupolar systems (DR = 1.5).
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. This methodology can also be applied to the synthesis of other photoactive compounds such as spiropyrans or spirooxazines. According to our working protocol the reaction did not require any solvent or additional reagents and gave the products within 10 min in isolated yields of up to 90%.
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. The current paper presents a simple and cheap high-throughput screening (HTS) assay based on AGE fluorescence and suitable for plant extract screening. We have already implemented an HTS assay based on vesperlysines-like fluorescing AGEs quickly (24 h) formed from BSA and ribose under physiological conditions. However, interference was noted when fluorescent compounds and/or complex mixtures were tested. To overcome these problems and apply this HTS assay to plant extracts, we developed a technique for systematic quantification of both vesperlysines (λ(exc) 370 nm; λ(em) 440 nm) and pentosidine-like (λ(exc) 335 nm; λ(em) 385 nm) AGEs. In a batch of medicinal and food plant extracts, hits were selected as soon as fluorescence decreased under a fixed threshold for at least one wavelength. Hits revealed during this study appeared to contain well-known and powerful anti-AGE substances, thus demonstrating the suitability of this assay for screening crude extracts (0.1 mg/mL). Finally, quercetin was found to be a more powerful reference compound than aminoguanidine in such assay.
New three-dimensional hole-transporting materials (HTMs) based on either 9,9′-spirobifluorene (SBF) or spiro-cyclopenta1,2-b:5,4-b′dithiophene-4,9′-fluorene (SDTF) core have been synthesized. All ...three HTMs, namely, SBFCz2, SDTFCz2, and SDTCz2F, are end-capped with two peripheral 3,6-dimethoxydiphenylaminyl-carbazole (CzDMPA) units. The HTMs behave as molecular glasses with glass transition temperature (T g) close to or higher than that of the reference HTM Spiro-OMeTAD. Thermal and optoelectronic properties strongly depend upon the nature of the bridging core unit between the two CzDMPA units. The two fluorene-bridged molecules SBFCz2 and SDTFCz2 exhibit similar properties. On the contrary, SDTCz2F, where the CzDMPA units are bridged to the cyclopentadithiophene ring, displays lower highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels and smaller band gaps. Upon doping of the HTM layer in perovskite solar cells, in spite of a much lower hole mobility, SDTCz2F leads to the highest power conversion efficiency (16.4% compared to 14.5 and 14.3% for SBFCz2 and SDTFCz2, respectively).
To study the electronic interactions in donor–acceptor (D–A) ensembles, D and A fragments are coupled in a single molecule. Specifically, a tetrathiafulvalene (TTF)‐fused ...dipyrido3,2‐a:2′,3′‐cphenazine (dppz) compound having inherent redox centers has been synthesized and structurally characterized. Its electronic absorption, fluorescence emission, photoinduced intramolecular charge transfer, and electrochemical behavior have been investigated. The observed electronic properties are explained on the basis of density functional theory.
Fused donor–acceptor ensemble: A tetrathiafulvalene (TTF)‐fused dipyrido3,2‐a:2′,3′‐cphenazine (dppz) compound (1) having inherent redox centers has been synthesized and structurally characterized (see picture). Its electronic absorption, fluorescence emission, photoinduced intramolecular charge transfer, and electrochemical behavior have been investigated. Theoretical calculations rationalize these experimental observations.
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
). This goes beyond what is possible to achieve using viologens, which are limited by not providing chelation as well as having no accessible biradicaloid state, corresponding to the neutral direduced MBqn
open-shell behaviour we observe here.
The binding of the snake-like trinitrodicyanomethylenefluorene-C60 derivative (TNDCF-C60) to the dynamic receptor, tetrathiafulvalene calix4pyrrole (TTF-calix4pyrrole), may be controlled via the use ...of a chloride anion as an external trigger. Whereas, in the absence of a chloride anion, the TNDCF “tail” of the trinitrodicyanomethylenefluorene-C60 substrate binds to the TTF−calix4pyrrole in a 2:1 (substrate/receptor) stoichiometry in CH2Cl2 solution, addition of a chloride anion (yellow) leads the TNDCF tail to be displaced in favor of a bound C60 “head”, a process that leads to the formation of a complex with overall 1:2:2 substrate/receptor/chloride anion stoichiometry. These chemical switching events are reflected in easy-to-visualize color changes, as well as in the production of two different kinds of charge-separated states following selective femtosecond photoexcitation.
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