Search results for "acceptor"
showing 10 items of 394 documents
Photo-electrical and transport properties of hydrothermal ZnO
2016
We performed the studies of optical, photoelectric, and transport properties of a hydrothermal bulk n-type ZnO crystal by using the contactless optical techniques: photoluminescence, light-induced transient grating, and differential reflectivity. Optical studies revealed bound exciton and defect-related transitions between the donor states (at ∼60 meV and ∼240 meV below the conduction band) and the deep acceptor states (at 0.52 eV above the valence band). The acceptor state was ascribed to VZn, and its thermal activation energy of 0.43 eV was determined. A low value of carrier diffusion coefficient (∼0.1 cm2/s) at low excitations and temperatures up to 800 K was attributed to impact the rec…
Hole localization in thermoelectric half-Heusler (Zr0.5Hf0.5)Co(Sb1−xSn ) thin films
2019
Abstract The (Ti, Zr, Hf)Co(Sb 1 − x Snx) material class has recently come into focus as an attractive p-type high-temperature thermoelectric material. This study experimentally demonstrates that homogeneous, highly textured (Zr0.5Hf0.5)Co(Sb 1 − x Snx) thin films can be grown on single crystalline MgO. By varying the sputter power, samples with both positive and negative Seebeck coefficient can be grown. The underlying reason for the sign change is the segregation of Sn nano-inclusions, which lower the effective doping of the half-Heusler matrix. Similarly the Hall constant also switches sign at low temperatures, which is modeled assuming semi-metal behavior and low temperature hole locali…
2,4,5-Triaryl imidazole probes for the selective chromo-fluorogenic detection of Cu(II). Prospective use of the Cu(II) complexes for the optical reco…
2019
The sensing behaviour toward metal cations and biothiols of two 2,4,5-triarylimidazole probes (3a and 3b) is tested in acetonitrile and in acetonitrile-water. In acetonitrile the two probes present charge-transfer absorption bands in the 320-350 nm interval. Among all cations tested only Cu(11) is able to induce bathochromic shifts of the absorption band in the two probes, which is reflected in marked colour changes. Colour modulations are ascribed to the formation of 1:1 Cu(II)-probe complexes in which the cation interacts with the imidazole acceptor heterocycle. Besides, the two probes present intense emission bands (at 404 and 437 nm for 3a and 3b respectively) in acetonitrile that are q…
Tuning the Electronic Properties of Nonplanar exTTF-Based Push–Pull Chromophores by Aryl Substitution
2012
International audience; A new family ofπ-extended tetrathiafulvalene (exTTF) donor−acceptorchromophores has been synthesized by [2 + 2] cycloaddition of TCNE with exTTF-substituted alkynes and subsequent cycloreversion. X-ray data and theoretical calculations,performed at the B3LYP/6-31G**level, show that the new chromophores exhibit highlydistorted nonplanar molecular structures with largely twisted 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) units. The electronic and optical properties, investigated by UV/visspectroscopy and electrochemical measurements, are significantly modified when theTCBD acceptor unit is substituted with a donor phenyl group, which increases the twistingof the TCBD unit…
Synthesis of an Acceptor–Donor–Acceptor Multichromophore Consisting of Terrylene and Perylene Diimides for Multistep Energy Transfer Studies
2016
Motivated by the results obtained from the investigation of singlet–singlet annihilation in a linear multichromophore comprising terrylene diimides (TDI) and perylene diimide (PDI) in 2010, we report the detailed process toward the successful synthesis of a TDI–PDI–TDI dyad. Ineffective synthetic pathways, which were necessary for the understanding of the step-by-step construction of the complex multichromophore, are described, leading toward a universal synthetic plan for multicomponent systems containing rylene diimides separated by rigid oligophenylene spacers.
A Ferroelectric Iron(II) Spin Crossover Material
2017
A dual-function material in which ferroelectricity and spin crossover coexist in the same temperature range has been obtained. Our synthetic strategy allows the construction of acentric crystal structures in a predictable way and is based on the high directionality of hydrogen bonds. The well-known iron(II) spin crossover complex [Fe(bpp)₂]²+ (bpp = 2,6-bis(pyrazol-3-yl)pyridine), a four-fold noncentrosymmetric H-bond donor, was combined with a disymmetric H-bond acceptor such as the isonicotinate (isonic) anion to afford [Fe(bpp)₂](isonic)₂·2H₂O. This low-spin iron(II) compound crystallises in the acentric nonpolar I-4 space group and shows piezoelectricity and SHG properties. Upon dehydra…
A Fully Conjugated TTF-π-TCAQ System: Synthesis, Structure, and Electronic Properties
2011
The synthesis of the first fully conjugated tetrathiafulvalene-tetracyano-p-quinodimethane ((TTF)-TCNQ)-type system has been carried out by means of a Julia-Kocienski olefination reaction. In particular, a tetracyanoanthraquinodimethane (TCAQ) formyl derivative and two new sulfonylmethyl-exTTFs (exTTF = 2-[9-(1,3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole)--prepared as new building blocks--were linked. A variety of experimental conditions reveal that the use of sodium hexamethyldisilazane (NaHMDS) as base in THF afforded the E olefins with excellent stereoselectivity. Theoretical calculations at the B3LYP/6-31G** level point to highly distorted exTTF and TCAQ that form an almo…
Role of the Open-Shell Character on the Pressure-Induced Conductivity of an Organic Donor-Acceptor Radical Dyad
2018
Single‐component conductors based on neutral organic radicals have received a lot of attention due to the possibility that the unpaired electron can serve as a charge carrier without the need of a previous doping process. Although most of these systems are based on delocalized planar radicals, we present here a nonplanar and spin localized radical based on a tetrathiafulvalene (TTF) moiety, linked to a perchlorotriphenylmethyl (PTM) radical by a conjugated bridge, which exhibits a semiconducting behavior upon application of high pressure. The synthesis, electronic properties, and crystal structure of this neutral radical TTF‐Ph‐PTM derivative (1) are reported and implications of its crystal…
A water molecule in the interior of a 1H-pyrazole Cu2+ metallocage
2016
Water has a great tendency to associate through hydrogen bonding with water molecules or other hydrogen bond donor or acceptor groups. Here the case of a water molecule encapsulated in the interior of a metallocage receptor is presented. The association of four copper(II) ions and two aza-macrocyclic receptors in which two 1H-pyrazole units are connected by cadaverine diamines leads to the inclusion of a water molecule into the cage, as proved by X-ray analysis and infrared spectroscopy. The included water molecule shows no hydrogen bonding with any component of the cage presenting only a weak hydrogen bond with an oxygen atom of a perchlorate counter-anion. The IR stretching vibrations pre…
Acceptor Specificity of Amylosucrase from Deinococcus radiopugnans and Its Application for Synthesis of Rutin Derivatives
2016
The transglycosylation activity of amylosucrase (ASase) has received significant attention owing to its use of an inexpensive donor, sucrose, and broad acceptor specificity, including glycone and aglycone compounds. The transglycosylation reaction of recombinant ASase from Deinococcus radiopugnans (DRpAS) was investigated using various phenolic compounds, and quercetin-3-O-rutinoside (rutin) was found to be the most suitable acceptor molecule used by DRpAS. Two amino acid residues in DRpAS variants (DRpAS Q299K and DRpAS Q299R), assumed to be involved in acceptor binding, were constructed by site-directed mutagenesis. Intriguingly, DRpAS Q299K and DRpAS Q299R produced 10-fold and 4-fold hig…