Conductive Charge-transfer Complexes Research Articles

Monitoring antiviral active metabolite (N-hydroxycytidine) levels in plasma in presence of carboxylesterase-2 inhibitor verapamil using copper tetracyanoquinodimethane enhanced sensor

This study focuses on the determination of the active metabolite of molnupiravir (MOL), N-hydroxycytidine (NHC), using a square wave voltammetric (SWV) method. Carboxylesterase-2 enzymes catalyze the conversion of MOL prodrug into NHC. However, co-administration of verapamil (VER), a carboxylesterase-2 inhibitor, may reduce the levels of NHC, leading to decreasing its antiviral activity. In this context, the levels of NHC and VER were simultaneously monitored using a carbon paste electrode modified with phase I of copper tetracyanoquinodimethane (CuTCNQ) which is highly conductive charge transfer complex. The as-designed sensor was characterized successfully using various spectroscopic techniques and Scanning Electron Microscopy (SEM). The electrochemical behavior of the newly fabricated probe was examined using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This method demonstrated its efficacy in measuring NHC and VER levels in rabbit plasma samples, showing high sensitivity and selectivity. The calibration plots for the simultaneous quantitation of NHC and VER displayed excellent linearity over the concentration ranges of 50–1600 nmol/L for NHC and 10–250 nmol/L for VER. The limits of detection (LOD) and quantitation (LOQ) in rabbit plasma were found to be 15.2 and 50.8 nmol/L for NHC and 2.9 and 9.9 nmol/L for VER, respectively. Moreover, fundamental pharmacokinetic parameters were calculated for NHC before and after co-administration of VER. The results suggest that the SWV method using CuTCNQ-modified CPE can be a useful tool for the determination of NHC and VER levels in plasma samples, with potential applications in the monitoring of drug-drug interactions involving carboxylesterase-2 inhibitors.

Preparation of Highly Conductive Phthalocyaninato-Cobalt Iodide at the Interface between Aqueous KI Solution and Organic Solvent and Catalytic Properties for Electrochemical Reduction of CO2

Abstract For the industrial practical use of cobalt phthalocyanine (CoPc) as a catalyst for CO2 reduction, the effect of improving conductivity of CoPc crystal on the catalytic activity was investigated. Focusing on (phthalocyaninato) cobalt iodide (CoPcI), which is a highly conductive charge-transfer complex, a simple method for synthesizing CoPcI by simply mixing at an interface between aqueous KI solution and CH2Cl2 solution containing CF3COOH and CoPc was developed by applying the CoPc crystal phase transformation method. The X-ray diffraction pattern of the obtained powder at the interface of CoPc organic and potassium iodide aqueous solutions revealed that the powder is composed of one-dimensional columns of CoPc and a linear array of triiodide ions (I3−). UV-vis absorption spectra showed that iodide ions (I−) change to triiodide ions (I3−) at the interface between aqueous KI solution and organic solvent under acidic conditions. The catalytic property of CoPcI was investigated by polarization measurement and electrochemical impedance spectroscopy using a gas diffusion carbon electrode. CoPcI showed high catalytic activity for CO2 reduction with high CO production selectivity.

Transport Properties of Molecular Conductors (BSBS)2XF6 (X = As, Sb, and Ta): Investigation of Intermolecular Transfer Integrals in the Radical-Cationic State of Benzothienobenzothiophene-Type Semiconductors

[1]Benzoseleno[3,2-b]benzoselenophene (BSBS) derivatives are known as high-performance transistor materials. Novel and highly conductive charge-transfer (CT) complexes, (BSBS)2XF6 (X = As and Sb), have been prepared, and their transport properties are investigated. At room temperature, these complexes exhibit conductivities larger than 600 S cm–1. The chemical pressure effect originating from the counter anion size is estimated to be 0.3 kbar. The thermoelectric (TE) power is 15–17 μV K–1, demonstrating that the BSBS complexes have remarkably large transfer integrals of 310 meV, as observed in the highly conductive benzothienobenzothiophene (BTBT) complexes. From both molecular orbital calculations and experiments, it is demonstrated that the BTBT skeleton has the property of forming a very large energy bandwidth. The TE power of metallic CT complexes based on organic transistor molecules is useful for experimentally determining the intermolecular transfer integrals of charged semiconductor molecules.

Spray-coated contacts from an organic charge transfer complex solution for organic field-effect transistors

We demonstrate the deposition of films of the conducting charge transfer complex TTF-TCNQ from solution by spray-coating. The benefit of spray-coating is the ability to process large volumes of solution, therefore allowing the utilisation of compounds with very low solubility. The sheet resistance in the TTF-TCNQ film is similar to that of the commonly used organic PEDOT:PSS electrodes, with the added benefit of room temperature deposition and no additional thermal treatments. Spray-coated TTF-TCNQ is used as source and drain electrodes for transistors based on the organic semiconductor C8-BTBT, achieving similar performances in terms of mobility and turn-on voltage than when conventional contacts of MoOx/Au are used, whilst exhibiting a slight improvement in the linearity of the output characteristics.

Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes.

Chiral molecular crystals built up by chiral molecules without inversion centers have attracted much interest owing to their versatile functionalities related to optical, magnetic, and electrical properties. However, there is a difficulty in chiral crystal growth due to the lack of symmetry. Therefore, we made the molecular design to introduce intermolecular hydrogen bonds in chiral crystals. Racemic and enantiopure bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) derivatives possessing hydroxymethyl groups as the source of hydrogen bonds were designed. The novel racemic trans-vic-(hydroxymethyl)(methyl)-BEDT-TTF 1, and racemic and enantiopure trans-vic-bis(hydroxymethyl)-BEDT-TTF 2 were synthesized. Moreover, the preparations, crystal structure analyses, and electrical resistivity measurements of the novel achiral charge transfer salt θ21-[(S,S)-2]3[(R,R)-2]3(ClO4)2 and the chiral salt α’-[(R,R)-2]ClO4(H2O) were carried out. In the former θ21-[(S,S)-2]3[(R,R)-2]3(ClO4)2, there are two sets of three crystallographically independent donor molecules [(S,S)-2]2[(R,R)-2] in a unit cell, where the two sets are related by an inversion center. The latter α’-[(R,R)-2]ClO4(H2O) is the chiral salt with included solvent H2O, which is not isostructural with the reported chiral salt α’-[(S,S)-2]ClO4 without H2O, but has a similar donor arrangement. According to the molecular design by introduction of hydroxy groups and a ClO4− anion, many intermediate-strength intermolecular hydrogen bonds (2.6–3.0 Å) were observed in these crystals between electron donor molecules, anions, and included H2O solvent, which improve the crystallinity and facilitate the extraction of physical properties. Both salts are semiconductors with relatively low resistivities at room temperature and activation energies of 1.2 ohm cm with Ea = 86 meV for θ21-[(S,S)-2]3[(R,R)-2]3(ClO4)2 and 0.6 ohm cm with Ea = 140 meV for α'-[(R,R)-2]2ClO4(H2O), respectively. The variety of donor arrangements, θ21 and two kinds of α’-types, and their electrical conductivities of charge transfer complexes based upon the racemic and enantiopure (S,S)-2, and (R,R)-2 donors originates not only from the chirality, but also the introduced intermolecular hydrogen bonds involving the hydroxymethyl groups, perchlorate anion, and the included solvent H2O.

Optimal Fabrication of P3HT:PCBM Based Organic Solar Cells with N-Type DMDCNQI Dopant.

We have fabricated P3HT and PCBM-based organic photovoltaic cells using DMDCNQI as a guest dopant material and an n-type buffer layer. We have investigated the physical effects of the DMD-CNQI molecule as a guest dopant and an n-type charge transfer buffer layer on the performance of the device by examining measurements of light current-voltage and photoluminescence characteristics. The device using DMDCNQI as a dopant and a buffer layer exhibited a remarkable increase in short-circuit current density (Jsc) due to the ability of an electron acceptor and to the formation of a highly conducting charge transfer complex. In particular, the device consisting of ITO/PEDOT:PSS/P3HT:PCBM:DMDCNQI(1 wt%)/DMDCNQ/Al showed a maximum power conversion efficiency of 3.50%.

Electrical Conductivity of Charge Transfer Complexes of Some Thiophene Schiff Base Complex with Nitrobenzene Acceptors

Electrical Conductivity of Charge Transfer Complexes of Some Thiophene Schiff Base Complex with Nitrobenzene Acceptors

Cooperation of Hydrogen-Bond and Charge-Transfer Interactions in Molecular Complexes in the Solid State

Abstract Our recent studies for the development of conducting charge-transfer complexes with well-defined assembled structures based on the cooperation of hydrogen-bond and charge-transfer interactions are described. We have designed and synthesized hydrogen-bonded charge-transfer complexes based on (1) tetrathiafulvalene derivatives having nucleobases, aminobenzo and imidazole moieties, and (2) tetracyanoquinodimethane radical anion salts with hydrogen-bond-functionalized phenalenyl and protonated oligo(imidazole) cations. The directional and site-selective hydrogen-bonds formed various supramolecular network structures, constructing segregated columns as the conduction path. Furthermore, the high polarity of hydrogen-bonds caused strong donor–acceptor or cation–anion electrostatic interactions modulating the ionicity of component molecules and the electronic structure of conduction columns. Such electronic modulation effects in addition to controlling the molecular arrangement realized the first purely organic molecular metal based on a hydrogen-bonded charge-transfer complex in the p-chloranil complex of an imidazole-functionalized tetrathiafulvalene derivative. The proton-donating/accepting ability of the hydrogen-bonding sites afforded the simultaneous proton- and charge-transfer complexes, demonstrating an important prompt for the realization of cooperative proton–electron-transfer systems.

Processing and Performance of Polymeric Transparent Conductive Composites

Recent advances in microelectronic and optoelectronic industries have spurred interest in the development of reticulate doped polymer films containing “metallic” charge transfer complexes. In this study, such reticulate doped polymer films were prepared by exposing solid solutions of bis(ethylenedioxy) tetrathiafulvalene (BEDO-TTF) in polycarbonate (PC) to iodine, forming conductive charge transfer complexes. The resulting films exhibited room temperature conductivities ranging from 6.33 to S cm−1. The colored iodine complexes in the film were reduced by cyclic voltammetry yielding conductive, colorless, transparent films. We were intrigued to examine the dielectric properties of BEDO-TTF in solid solution in PC prior to formation of the charge transfer complex as no such studies appear in the literature. Dielectric analysis (DEA) was used to probe relaxations in neat PC and BEDO-TTF/PC. BEDO-TTF plasticized the PC and decreased the glass transition temperature. Two secondary relaxations appeared in PC films, whereas the transitions merged in the BEDO-TTF/PC film. DEA also evidenced conductivity relaxations above 180°C which are characterized via electric modulus formalism and revealed that BEDO-TTF increased AC conductivity in PC.

Synthesis and characterization of highly conductive charge-transfer complexes using positron annihilation spectroscopy

Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl4), iodine, bromine, and zinc chloride (ZnCl2) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors π-acceptors (Pi-OH and QL), σ-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl4 and ZnCl2) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl4, and ZnCl2 acceptors and iodine, Pi-OH, and Br2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

Spectral, Thermal and DC Electrical Conductivity of Charge Transfer Complex Formed Between 5,7-Dimethyl-1-oxo-2-phenyl-1H-pyrazolo [1,2-α]pyrazol-4-ium-3-olate and Iodine

Reaction of phenylmalonic acid dihydrazide with 2,4-pentanedione proceeded through a novel rearrangement to give 5,7-dimethyl-1-oxo-2-phenyl-1H-pyrazolo[1,2-α]pyrazol-4-ium-3-olate (DPO). This peculiar structure had a positive charge (cation) localized on the pyrazolium ring and a negative charge localized on the other ring. The intermolecular charge-transfer complexes (CTC) formed between DPO as donor and iodine as an acceptor have been studied spectrophotometrically. Doping was done in two ways: by mixing and chemically using different ratios of I2. The suggested structures of the solid iodine charge-transfer complexes were investigated by several techniques using electronic spectra, FTIR spectroscopy and thermal analysis (TGA and DTA). DC electrical conductivity variation with temperature in the range 300–500 K after annealing for 24 h at 100°C and after doping with different ratios of I2 through the two ways of doping is determined for comparison. The activation energies were calculated and the results were interpreted using the band energy model. DC electrical conductivity of the iodine CTC increased with increasing temperature. The iodine CTC are only one or two orders of magnitude higher in DC electrical conductivity than the undoped material, however the energy gap is very small in addition to its thermal stability which suggests the use of these materials in applications like photovoltaic cells.

Epitaxial Growth of Conductive Charge-transfer Complex in the Organized Molecular Film on Fluorinated Copolymer as Template

Epitaxial Growth of Conductive Charge-transfer Complex in the Organized Molecular Film on Fluorinated Copolymer as Template

ChemInform Abstract: Conductive Charge-Transfer Complexes of Alkoxy Substituted Tetrathiafulvalene, BEDO-TTF

Abstract BEDO-TTF which is one of the oxygen substituted BEDT-TTF analogues, gave conductive organic charge transfer complexes in contrast to BEDT-TTF and other BEDT-TTF derivatives. Especially many complexes exhibit metallic temperature dependences even with the compressed disks. These facts suggest the remarkable tendency of BEDO-TTF to aggregate themselves.

ChemInform Abstract: Phenanthro(1,10-cd:8,9-c′d′)bis(1,2)dithiole and -diselenole as Novel Electron Donors.

The preparation of the title compounds is reported along with their formation of electrically highly conductive charge-transfer complexes with the common electron acceptors TCNQ, TCNQF4, and DDQ.

ChemInform Abstract: Design of Novel Chalcogen-Containing Organic Metals: Extensively Conjugated Electron Donors and Acceptors with Reduced On-Site Coulomb Repulsion

Abstract This review describes the design of extensively conjugated electron donors and acceptors based on structural modifications of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ), respectively. These molecules have the advantage of reduced on-site Coulomb repulsion which is one of the prerequisites for components of organic metals. The construction of such large compounds is currently accomplished by insertion of an extensively π-conjugated system between two 1,3-dithiolylidene or dicyanomethylene groups. The usefulness of a heteroquinoid system as such a building block is demonstrated by examples of heteroatom-incorporating TCNQ acceptors (hetero-TCNQs), which form a variety of highly conductive charge-transfer complexes. In addition, recent advances concerning quino-2,2′-bis(1,3-dithioles) and TTF vinylogs as novel electron donors are introduced.

Ultrafast and large reflectivity change by ultraviolet excitation of the metallic phase in the organic conductor (EDO-TTF) 2PF 6

We examined the ultrafast response of the metallic high-temperature phase in the conducting charge transfer complex (EDO-TTF) 2PF 6. A large reflectivity change of approximately 10% was observed when the intra-molecular band was excited by a weak 3.1 eV ultraviolet light pulse. The lifetimes of the photo-induced states were 0.2 and 0.7 ps in the Drude-like band and the intra-molecular band, respectively. Measurement of the photo-induced spectrum just after photo-excitation and simulation using the Drude model revealed that the electronically excited EDO-TTF molecules shortened the relaxation time of conduction electrons and reduced the reflectivity of the Drude-like band.

Novel Benzene-Bridged Triphenylene-Based Discotic Dyads

We report the synthesis and characterization of two series of novel triphenylene-based benzene-bridged symmetric discotic dimers. Two triphenylene discotics have been connected to a rigid benzene ring via flexible methylene spacers. In one series, triphenylene moiety was tethered with benzene via an ester linkage, while in the second series it is via an ether linkage. Within each series, the orientation of the linkage of the triphenylene core around the benzene core has been changed by substituting the benzene ring at o-, m-, and p-positions. These materials have been characterized from their spectral and elemental analysis. The thermotropic liquid crystalline properties were investigated by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction studies. All the virgin compounds do not display any mesomorphism; however, their charge transfer complexes with trinitrofluorenone, an electron acceptor, exhibited columnar mesophases. The direct current (dc) conductivity of charge transfer complexes at two ratios has been studied at variable temperature. The small conductivity value demonstrates that long spacers as well as connectivity to the rigid benzene ring dilute the column packing, hence making pi-pi interaction less efficient for the entire column length. A hexagonal assembly of triphenylene-benzene dimer 12 on a highly oriented pyrolytic graphite (HOPG) surface has been visualized with scanning tunneling microscopy (STM).

Excitation photon energy dependence of photo-induced phase transition in (EDO-TTF)2PF6

The conducting charge transfer complex (EDO-TTF)2PF6 has two types of charge transfer bands in the low temperature insulator phase: CT1 at 0.56 eV and CT2 at 1.38 eV. We excited these bands independently with a tunable ultrashort pulse laser and studied the difference of the photo-induced phases by measuring change in reflectivity spectrum over a wide photon energy range. As a result, we found that both the photo-induced phases by CT1 and CT2 excitation are the same except for their photo-conversion efficiencies

The photo-induced phase and coherent phonon in the organic conductor(EDO-TTF)2PF6

We have investigated the nature of the photo-induced stateand coherent phonon in the conducting charge transfer complex(EDO-TTF)2PF6 by measuring the ultrafast reflectivity change over a wide photon energy range from 0.069 eV(18 µm) to 2.1 eV (580 nm). The photo-induced spectra just after photo-excitation indicate that thephoto-induced phase is similar to but clearly different from that in a thermally inducedmetal phase though they are the same for general photo-induced phase transition. Thetemporal profiles at each probe photon energy are accompanied by extraordinarily largeamplitude oscillation originating from coherent phonon generation. The periodof the coherent phonon depends discretely on the probe photon energy, whilethe generation efficiency of both the photo-induced phase and coherent photonreaches a maximum when the peak top of a charge transfer band is excited. Theseresults are probably attributable to the strong electron–vibration coupling in thiscomplex.

Synthesis of Bis(ethylenedithio)dithiadiazafulvalenes (BEDT-DTDAF) and Generation of Charge-Transfer Complexes with Tetracyanoquinodimethane

The synthesis of bis(ethylenedithio)dithiadiazafulvalenes (BEDT-DTDAFs), in four steps via 4,5-(ethylenedithio)thiazole and 3-alkyl-4,5-(ethylenedithio)thiazolium salts, and the generation of conducting charge-transfer complexes from a new type of dithiadiazafulvalene and tetracyanoquinodimethane are reported.