Formation Of Charge-transfer Complex Research Articles

Rigidity-Tuned Full-Color Emission: Uncommon Luminescence Change from Polymer Free-Volume Variations.

Probing the rigidity change of microenvironments via tracking embedded molecular fluorophore emissions represents a robust approach to monitor various polymer microstructural evolutions and biomolecular events with a high spatiotemporal resolution. However, reported fluorophores exclusively blueshift their emissions (termed as "rigidochromism") or merely alter intensities upon rigidification, suffering from inferior sensitivities, low-contrast outputs, and attenuated biocompatibilities. Here, phenanthridine-fused triazatruxene fluorophores (PTFs) with pronounced bathochromic emission (up to 135nm) toward rigidifying media at a low loading of 5ppm without sacrificing the quantum yields and lifetime are developed. PTFs effectively interact with polymeric matrixes through polar-π interactions and form charge-transfer complexes, resulting to a remarkable fluorescent color change from blue to red-orange over matrix rigidifying. Such a unique anti-rigidochromism enables a highly sensitive rigidity detection (i.e., a subtle polymer molecular-weight change (as low as 1000Da vs up to 10kDa for conventional probes) can result to obvious emission color changes). PTFs are able to noninvasively detect polymerization kinetics and in situ optically report polymer degradations. The broadly (nearly full-spectrum) tunable emission and the efficient coupling between anti-rigidochromism and polymer hierarchical structures/topologies render fluorescence with controlled wavelength and chirality, leading to an unprecedented free-volume-based data encryption and anti-counterfeiting technology with a superhigh security level.

VALIDATED SPECTROPHOTOMETRIC METHODS BASED ON CHARGE TRANSFER COMPLEXATION REACTION FOR THE DETERMINATION OF VALACYCLOVIR HYDROCHLORIDE AS ANTIVIRAL DRUG IN PHARMACEUTICAL FORMULATIONS

Objective: The present study aims to develop and validate two simple, sensitive, accurate, precise and economical spectrophotometric methods for the determination of valacyclovir HCl (VAL) in pure form and pharmaceutical formulations. Methods: The developed methods are based on the formation of charge-transfer complex between VAL as n-electron donor and quinalizarin (Quinz) or alizarin red S (ARS) as π-acceptor in methanol to form highly colored chromogens, which showed an absorption maximum at 565 and 540 nm using Quinz and ARS, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Results: Under the optimum conditions, Beer’s law is obeyed in the concentration ranges 0.5–16 and 1.0–20 μg/ml using Quinz and ARS, respectively, with good correlation coefficient (r2 ≥ 0.9994) and with a relative standard deviation (RSD% ≤ 0.70). The limits of detection and quantification were found to be 0.15 and 0.30 µg/ml for Quinz and 0.50 and 1.0 µg/ml for ARS. Conclusion: The methods were successfully applied to the determination of VAL in its pharmaceutical formulations and the validity assesses by applying the standard addition technique. Results obtained by the proposed methods for the pure VAL and commercial tablets agreed well with those obtained by the reported method.

Synthesis and spectroscopic characterization of charge transfer complexes of the donor hesperidin and π-acceptors; 2,3-dichloro-5,6-dicyano-1,4- benzoquinone and tetracyanoethylene

The interactions between a biologically active flavonoid, hesperidin (HESP) and two of the most known π- acceptors DDQ and TCNE were investigated leading to two new charge transfer complexes (CTC). UV-Visible spectrophotometry was used to follow the reactions in solution in methanol and ethanol as solvents. Infrared and NMR spectrophotometry was used to characterize the products formed in the solid state reactions.The)1:1(stoichiometry of formed charge transfer complexes (HESP-DDQ and HESP-TCNE) was confirmed by Molar ratio method and Benesi-Hildbrand equation was used to calculate the formation constants KCT and the molar extinction coefficient ɛCT of the formed CTC.CTC formed in the reaction of hesperidin with π-acceptors DDQ and TCNE showed high formation constants KCT. KCT values for both CTC formed in ethanol are higher than those formed in methanol and those found for the HESP-DDQ CTC were higher than those of HESP-TCNE.Our results suggest the formation of stable CT complexes of hesperidin with π-acceptors DDQ and TCNE.

Optical and electrical analysis in various organic-inorganic stacked structures

Understanding heterojunctions in layered organic semiconductor devices is crucial in achieving efficient optoelectronic and advanced organic electronic devices. In this paper, we investigated the formation of charge transfer complex (CTC) and the generation of free carriers at the interface of the transition metal oxide (TMO)/organic semiconductor (OS) bi-layer structures. First, the relationship between the CTC and conductivity is analyzed for bi-layers composed of molybdenum oxide (MoO 3 ) and OSs with different highest occupied molecular orbital (HOMO) levels, respectively. Same analysis is done for bi-layers involving N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) and various TMOs with different work-functions, respectively. It is investigated that CTC is formed at the interface of the TMO/organic bi-layer structure and the conductivity in the TMO is increased. The absorbance intensities of the CTCs at the heterojunctions are proposed to depend on the density of the OS radicals formed from the charge transfer process. It is demonstrated that conductivity is low at bi-layer interfaces with high density of CTC. This is because the CTC aligned at the interface acts as a hindrance to electron mobility. Consequently, it is demonstrated that MoO 3 /2TNATA and MoO 3 /NPB exhibited low conductivity despite the formation of more CTCs than MoO 3 /CBP. We propose that the CTCs at the OS/TMO heterojunction with low charge separation efficiency, causes negative charges to align at the interface. This negatively charged electric field at interface act as resistance to the mobility of electrons inside the TMO layer. The investigation is key in achieving efficient organic electronic devices and stacked organic semiconductor functional structures. • Heterojunctions with organic hosts and transition metal oxides are investigated. • The formation of CTC and free carriers at the heterojunctions are analyzed. • Conductivity is low at the heterojunctions with high CTCs. • CTCs with low charge separation efficiency cause resistance to electron flow.

A Universal Study on the Effect Thermal Imidization Has on the Physico-Chemical, Mechanical, Thermal and Electrical Properties of Polyimide for Integrated Electronics Applications

Polyimides (PI) are a class of dielectric polymer used in a wide range of electronics and electrical engineering applications from low-voltage microelectronics to high voltage isolation. They are well appreciated because of their excellent thermal, electrical, and mechanical properties, each of which need to be optimized uniquely depending on the end application. For example, for high-voltage applications, the final polymer breakdown field and dielectric properties must be optimized, both of which are dependent on the curing process and the final physico-chemical properties of PI. The majority of studies to date have focused on a limited set of properties of the polymer and have analyzed the effect of curing from a physicochemical-, mechanical- or electrical-centric viewpoint. This paper seeks to overcome this, unifying all of these characterizations in the same study to accurately describe the universal effect of the cure temperature on the properties of PI and at an industrial processing scale. This paper reports the widest-ranging study of its kind on the effect that cure temperature has on the physico-chemical, mechanical, thermal and electrical properties of polyimide, specifically poly (pyromellitic dianhydride-co-4, 4′-oxydianiline) (PMDA/ODA). The optimization of the cure temperature is accurately studied not only regarding the degree of imidization (DOI), but also considering the entire physical properties. Particularly, the analysis elucidates the key role of the charge–transfer complex (CTC) on these properties. The results show that while the thermal and mechanical properties improve with both DOI and CTC formation, the electrical properties, particularly at high field conditions, show an antagonistic behavior enhancing with increasing DOI while degrading at higher temperatures as the CTC formation increases. The electrical characterization at low field presents an enhancement of the final PI properties likely due to the DOI. On the contrary, at high electric field, the conductivity results show an improvement at an intermediate temperature emphasizing an ideal compromise between a high DOI and PI chain packing when the thermal imidization process is performed over this equilibrium. This balance enables maximum performance to be obtained for the PI film with optimized electrical properties and, overall, optimal thermal and mechanical properties are achieved.

Highly Efficient and Long‐Range Charge‐Transfer Complex Emission Between Two Blue Phosphorescent Emitters for White Organic Light‐Emitting Diodes

AbstractHerein, the authors report on charge‐transfer (CT) complex emission‐based organic light‐emitting diodes (OLEDs), which emit light by electric field‐induced intermolecular CT complex formation in the light‐emitting layer. Two phosphorescent materials are chosen to have energy level offset for the CT complex formation. This process generates the CT complex, which efficiently emits only in the electroluminescent device by electric‐field‐induced complex formation. A phenylpyridine‐ligand‐based Ir compound and phenylimidazole‐based Ir compounds are selected as the CT complex‐forming materials, and the CT complex exhibits yellow emission under an electric field. Moreover, the doping of the two compounds in the host material produces white OLEDs, exhibiting both blue emission and yellow emission at a quantum efficiency of 13.7%. In particular, the color of the CT complex device can be tuned by the content of each material in the emitting layer. As an initial result, the quantum efficiency is acceptable, and further material development would enhance the quantum efficiency of the CT complex OLEDs. This light‐emitting device can be used in various applications, e.g., a mono‐color or a white‐color light‐emitting diode.

SPECTROPHOTOMETRIC METHODS FOR THE QUANTITATIVE DETERMINATION OF MEMANTINE HYDROCHLORIDE IN PURE FORM AND PHARMACEUTICAL FORMULATIONS

Objective: Three simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of Alzheimer’s disease drug memantine HCl (MEM) in pure form and pharmaceutical formulations. Methods: The method was based on the formation of charge transfer complex between MEM as n-electron donor and various π-acceptors quinalizarin (Quinz) in methanol, p-chloranilic acid (p-CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile as chromogenic reagents which showed an absorption maximum at 558, 532 and 840 nm using Quinz, p-CA and TCNQ, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Results: Under the optimum conditions, beer’s law is obeyed in the concentration ranges 4.0–24, 10–160 and 5.0–50 μg/mlusing Quinz, p-CA and TCNQ, respectively with good correlation coefficient (r2 ≥ 0.9995) and with a relative standard deviation (RSD% ≤ 1.11). For more accurate analysis, Ringbom optimum concentration ranges were found to be between 8.0–20, 15–140 and 10–45 μg/ml using Quinz, p-CA and TCNQ, respectively. The limits of detection were found to be 1.2, 2.70 and 1.45 µg/ml and the limits of quantification were found to be 4.0, 9.0 and 4.83 µg/ml for Quinz, p-CA and TCNQ, respectively. A Job's plot of the absorbance versus the molar ratio of MEM to each of the acceptors under consideration indicated (1:1) ratio. Conclusion: The methods were successfully applied to the determination of MEM in its pharmaceutical formulations and the validity assessed by applying the standard addition technique. Results obtained by the proposed methods for the pure MEM and commercial tablets agreed well with those obtained by the reported method.

Fmoc-protected amino acids as luminescent and circularly polarized luminescence materials based on charge transfer interaction

Fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids are effective building blocks in self-assembled architectures at hierarchical levels, which however show limited luminescent properties and chiroptical activities. Here we introduce a charge-transfer strategy to build two-component luminescent materials with emerged circularly polarized luminescence properties. A library of Fmoc-amino acids was built, which selectively form charge-transfer complexes with the electron-deficient acceptor. Embedding in amorphous polymer matrix or physical grinding could trigger the charge-transfer luminescence with adjusted wavelengths in a general manner. X-ray diffraction results suggest the multiple binding modes between donor and acceptor. And, the solution-processed coassembly could selectively exhibit circularly polarized luminescence with high dissymmetry g-factors. This work illustrates a noncovalent charge-transfer strategy to construct luminescent and chiroptical organic composites based on the easy-accessible and economic chiral N-terminal aromatic amino acids.

Potentials of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol as novel charge transfer acceptors in pharmaceutical analysis of some quinolones and cephalosporins

BackgroundQuinolones and cephalosporins are antibiotic agents with activity against Gram-positive and Gram-negative bacteria. They contain chromophores and amine groups which are electron-rich centres capable of donating electrons to electron-deficient compounds. A survey of the literature revealed that 2, 4-dinitro-1-naphthol, a nitroaromatic useful in chemical synthesis, can accept electrons in charge transfer reactions. This work investigates N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol in the formation of charge transfer complexes by accepting electrons from selected quinolones and cephalosporins. Five other nitroaromatics (i.e. 4-nitro-1-naphthylamine, 2-nitro-1-naphthol, 2,4-dinitro-1-naphthylamine, 1-nitronaphthalene and 1,4-dinitronaphthalene) were screened in addition to the aforementioned and compared for charge transfer complexes formation. Spot test was used to establish charge transfer complex formation at room and elevated temperatures with determination done by visual inspection and thin layer chromatographic analysis of the reaction mixture. Ultraviolet visible absorption spectroscopy was used to estimate the extent of complexes.ResultsOnly solutions of adducts of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol gave instant and distinct colour with each drug used at room and elevated temperature. While the former gave deep golden yellow, the latter gave golden yellow against their blank reagent solutions which were, lemon and greenish yellow respectively. Visual inspections of 2-nitro-1-naphthol adduct solutions showed no colour change from the yellow colour of the blank reagent solution, even though the Ultraviolet visible absorption spectra revealed the formation of charge transfer complexes. The adducts solutions of 4-nitro-1-naphthylamine, 2,4-dinitro-1-naphthylamine, 1-nitronaphthalene and 1,4-dinitronaphthalene showed no colour change from their blank reagent solutions and their Ultraviolet visible absorption spectra revealed no formation of charge transfer complexes.ConclusionUltraviolet visible absorption spectral analysis shows superiority of N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol in charge-transfer complex formation over other nitroaromatics screened. N-(2, 4-dinitro-1-naphthyl)-p-toluenesulphonamide and 2, 4-dinitro-1-naphthol are good acceptors of electrons from these drugs, hence could be useful as charge transfer reagents in ultraviolet visible spectrophotometric analysis of these drugs.

Intermolecular interactions of tetracyanoethylene (TCNE) and fumaronitrile (FN) with minor amines: A combined UV-Vis and EPR study.

In this paper, the nature of interactions between two cyanocarbons-tetracyanoethylene (TCNE) and fumaronitrile (FN)-and a series of four secondary amines possessing a general formula C4HxN (x = 5-11) is thoroughly scrutinized. For all of the TCNE-amine pairs, tricyanovinylation (TCV) reaction is observed; however, only for pyrrole, it is accompanied with a visible charge-transfer (CT) complex formation-no such chemical individuals, characteristic for TCNE, have been noticed for aliphatic and alicyclic amines. On the contrary, FN forms such complexes with all the amines studied. Interestingly, a rather unexpected reaction of FN with alicyclic amines has been observed. The recorded electron paramagnetic resonance (EPR) spectra indicate the presence of both TCNE●- and FN●- radicals in the analyzed samples, assigned to a complete charge (electron) transfer process within the CT complexes, whose efficiency can be additionally enhanced by photoirradiation. The origination of the former radical, whose presence is observed also in the TCNE-diethylamine mixture, is as well proposed to result indirectly from the TCV reaction, occurring for this system. Finally, the superhyperfine structure of EPR spectra, indicating the existence of some secondary interactions of the radicals with surrounding compounds, is discussed. Formation of CT complexes and tricyanovinylates has been investigated and characterized with UV-Vis spectroscopy, while the presence of (cyano)radicals in the analyzed mixtures has been evidenced by (photoinduced) EPR measurements. Interpretation of the experimental results is also supplemented with computer simulations including density functional theory calculations.

Phenothiazine-based charge-transfer complexes as visible-light photoinitiating systems for acrylate and thiol-ene photopolymerization

Owing to their unique photodynamics, phenothiazine (PTZ) can be used to form charge-transfer complexes (CTCs), which serve as effective visible-light photoinitiating systems (PIS) for acrylate and thiol-based click polymerization. In this study, seven PTZ structures and their corresponding CTCs with iodonium salt (Iod) were evaluated by calculated spectra and polymerization kinetics. The effectiveness of the initiator decreased in the order of N-substituted polycyclic aromatic hydrocarbons > electron-donating aromatics > electron-withdrawing aromatics ≈ aliphatic alkanes. Substituted dimethylaminophenyl derivatives exhibited a lower energy gap and higher photoinitiation efficiency in CTCs. Moreover, PTZ-based CTCs as PIS rendered increased thermal stability to the photosensitive resin systems due to the mild free-radical quenching of PTZ. Such characteristic demonstrates potential versatility in the 3D printing of high-performance and high-precision materials.

Characterization of intrinsic low-polyimide films studied by positron annihilation

Four kinds of polyimide (PI) films were prepared by polycondensation reaction using the pyromellitic dianhydride (PMDA) and 4, 4′-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA）as the dianhydride monomer, the p-phenylenediamine (PDA), 4-4′-diaminodiphenyl ether (ODA) and 4,4′-(Hexafluoroisopropylidene) bis(p-phenyleneoxy) dianiline (HFBDA) as the diamine monomer respectively. The incorporation of trifluoromethyl groups can effectively inhibit the formation of intermolecular and intramolecular charge-transfer complex (CTC), improve the energy gap and increase the free volume in PI, which leads to an improvement in the optical and dielectric properties in different degree for three fluorinated PI films compared with the Kapton film. The maximum transmittance in visible region reaches 90.5% and the dielectric constant at 104Hz is close to 2.0 for PI6FDA-HFPBDA film. The breakdown strength weakens because of the increase of free volume. The correlation between the dielectric and breakdown characteristics and their free volume has been explained with the help of positron lifetime spectra.

The Impact of Interfacial Interactions on Structural, Electronic, and Sensing Properties of Poly(3‐methylthiophene) in Core‐Shell Nanocomposites. Application for Chemical Warfare Agent Simulants Detection

AbstractIn this paper, structural, electronic, and sensing properties of the poly(3‐methylthiophene) (P3MT) in two types of its core–shell nanocomposites with multiwall carbon nanotubes (MWCNTs) and poly(vinylidene fluoride) with different contents of the P3MT component (shell) are explored and are compared. The results indicate specific changes in the P3MT properties appear due to its interfacial interactions with the MWCNTs and PVDF components. In the case of the doped P3MT, charge transfer from MWCNT to P3MT leads to partial dedoping of the latter. The evidence of intermolecular charge transfer complex formation between undoped P3MT (donor) and MWCNTs (acceptor) is obtained. Changes in the properties of P3MT in nanocomposites are used to detect and to reliably recognize some chemical warfare agent's simulants of nerve agents and mustard gas. The sensitivity dependences of the nanocomposites on their work functions, Hansen solubility parameters and analytes electronegativity are studied. It is shown that the sensor response is controlled by a partial charge transfer if the difference between the work function of the sensing material and the electronegativity of the analyte molecules does not exceed a certain value (in the case herein ≈0.3 eV).

Fluorescein based fluorescent and colorimetric sensors for sensitive detection of TNP explosive in aqueous medium: Application of logic gate

Rapid detection of 2,4,6-trinitrophenol (TNP) in real samples has recently attained considerable attention from the perspective of national security, human health, and environmental safety. In this context, cost-effective and convenient detection of TNP explosive was accomplished through two new fluorescein based sensors F2 and F3. Sensors displayed effective fluorescence quenching response towards TNP in the aqueous medium. Highly sensitive fluorescence detection of TNP explosive (detection limit, 0.73 (F2) and 1.7 nM (F3)) was governed by ground-state charge transfer complex formation, facilitated by favorable H-bonding between sensor and TNP explosive. Fluorescence quenching mechanism for the detection of TNP explosive was investigated through UV–Visible absorption, dynamic light scattering (DLS), density functional theory (DFT) calculations, the Benesi-Hildebrand, and Job’s plots. Advantageously, sensors displayed selective and immediate colorimetric recognition of TNP explosive. Importantly, sensors exhibited quick response time towards TNP even in the presence of potential interferences that make them highly suitable for practical applications. Sensors were successfully applied for fluorescent and colorimetric detection of TNP explosive in industrial water samples and fabrication of logic gates. Further, convenient contact mode and instant surface sensing of TNP explosive were achieved through the fabrication of fluorescent strips and explosive responsive test kits.

Spectroscopic and DFT studies of the charge transfer complexation of iodine with aniline and its derivatives in carbon tetrachloride medium

The charge-transfer (CT) complex formation of iodine with aniline and derivatives of aniline in CCl4 at numerous temperatures (293.15–308.15 K) has been investigated by UV–Visible spectroscopy and density functional theory (DFT) methods. The formation constant (KCT) of the CT complexation was determined by using the Benesi-Hildebrand plot. The KCT values of CT complexes amid iodine and aniline/aniline derivatives were found to be changed with temperature variation and the change of the structure of donor molecules. Thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 of CT complexes were calculated from the standard thermodynamic equations. The ΔG0 values are negative, which indicates the spontaneous nature of CT complexation. The ΔH0 and ΔS0 values for the iodine-aniline/ derivatives of aniline indicated that the CT complexation is happened due to hydrophobic and exothermic interactions. The additional CT band has appeared in the UV spectra from experimental and DFT studies. Besides, the interaction between the I2 and aniline/ derivatives of aniline was detected by the elongation of bond length of I2 acceptors. Also, other parameters associated with the CT complexes have been evaluated and described in detail.

Selective Extraction, Recovery, and Sensing of Hydroquinone Mediated by a Supramolecular Pillar[5]quinone Quinhydrone Charge-Transfer Complex.

Intermolecular interactions between an electron-rich aromatic hydroquinone (HQ) with its electron deficient counterpart, benzoquinone (BQ), result in the formation of a quinhydrone charge-transfer complex. Herein, we report a novel quinhydrone-type complex between pillar[5]quinone (P[5]Q) and HQ. Characterized by a suite of spectroscopic techniques including 1H NMR, UV-visible, and FTIR together with PXRD, SEM, BET, CV, and DFT modeling studies, the stability of the complex is determined to be due to an electron-proton transfer reaction coupled with a complementary donor-acceptor interaction. The selectivity of P[5]Q toward HQ over other dihydroxybenzene isomers allows for not only the naked-eye detection of HQ but also its selective liquid-liquid extraction and recovery from aqueous media.

Interfacial Charge Transfer Complexes in TiO2-Enediol Hybrids Synthesized by Sol-Gel.

Metal oxide-organic hybrid semiconductors exhibit specific properties depending not only on their composition but also on the synthesis procedure, and particularly on the functionalization method, determining the interaction between the two components. Surface adsorption is the most common way to prepare organic-modified metal oxides. Here a simple sol–gel route is described as an alternative, finely controlled strategy to synthesize titanium oxide-based materials containing organic molecules coordinated to the metal. The effect of the molecular structure of the ligands on the surface properties of the hybrids is studied using three enediols able to form charge transfer complexes: catechol, dopamine, and ascorbic acid. For each system, the process conditions driving the transition from the sol to chemical, physical, or particulate gels are explored. The structural, optical, and photoelectrochemical characterization of the amorphous hybrid materials shows analogies and differences related to the organic component. In particular, electron paramagnetic resonance (EPR) spectroscopy at room temperature reveals the presence of organic radical species with different evolution and stability, and photocurrent measurements prove the effective photosensitization of TiO2 in the visible range induced by interfacial ligand-to-metal charge transfer.

TiO2-Acetylacetone as an Efficient Source of Superoxide Radicals under Reduced Power Visible Light: Photocatalytic Degradation of Chlorophenol and Tetracycline

Visible light-sensitive TiO2-based nanomaterials are widely investigated for photocatalytic applications under high power (≥300 W) UV and visible light. The formation of charge transfer complexes (CTCs) between bidentate ligands and nanocrystalline TiO2 promotes visible light absorption and constitutes a promising alternative for environmental remediation under reduced visible light power. However, the efficiency of photodegradation, the volatilization profile of bidentates, and the role of reactive oxidizing species (ROS) are not fully understood. In this study, thermogravimetric analyses coupled with mass spectroscopy (TGA-MS) were performed on TiO2-Acetylacetone (ACAC) CTC. TiO2-ACAC CTC calcined at 300 °C (TiO2-A300) was applied for the photocatalytic degradation of chlorophenol (4-CP) and tetracycline (TC) under low power visible light (26 W). Furthermore, the ROS scavengers isopropanol and benzoquinone were added for studying the photocatalytic role of •OH and •O2− radicals. The TGA-MS showed the release of ACAC fragments, such as ethyl ions and acetone, in the range between 150 °C and 265 °C, while between 300 °C and 450 °C only CO2 and H2O were released during oxidation of ACAC. The photocatalytic abatement of tetracycline (68.6%), performed by TiO2-A300, was ~two times higher than that observed for chlorophenol (31.3%) after 6 h, indicating a distinct participation of ROS in the degradation of these pollutants. The addition of the ROS scavenger revealed •O2− radicals as primarily responsible for the high efficiency of TiO2-ACAC CTC under reduced visible light. On the other hand, the •OH radicals are not efficiently generated in the CTC. Therefore, the development of heterostructures based on TiO2-ACAC CTC can increase the generation of ROS through coupling with semiconductors capable of generating •OH under visible light.

Quinine Charge Transfer Complexes with 2,3-Dichloro-5,6-Dicyano-Benzoquinone and 7,7,8,8-Tetracyanoquinodimethane: Spectroscopic Characterization and Theoretical Study

The molecular charge transfer reactions of quinine (Q) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a π-acceptor to form charge transfer (CT) complexes have been studied. The CT complexes were characterized by infrared spectra, NMR, mass spectrometry, conductometry and spectrometry. The Q-DDQ and Q-TCNQ charge transfer complexes were monitored at 480 and 843 nm, respectively. The results confirm the formation of CT complexes. The molar ratio of Q:DDQ and Q: TCNQ assessed using Job’s method was 1:1, which agrees with the results obtained by the Benesi-Hildebrand equation. The stability of the formed CT complexes was assessed by measuring different spectroscopic parameters such as oscillator strength, transition dipole moment, ionization potential, the energy of CT complex, resonance energy, dissociation energy and standard free energy change. The DFT geometry optimization of quinine, DDQ and TCNQ, its charge transfer complex, and UV theoretical vs. experimental comparative study were carried out. The theoretical and experimental results agreed. DFT/B3LYP/6-311++G(d,p) level of theory was used for the investigation of charge transfer between quinine as electron donor and (DDQ and TNCQ) as electron acceptors. The geometric structures, orbital energies, HOMO, LUMO and energy gaps were determined. The transition energies of the charge transfer complexes were computed using the TD-DFT/B3LYP/6-311++G(d,p) level of theory. The computed parameters were comparable to the experimental parameters, and the computational results aided in the analysis of the data.

Highly efficient bromine capture and storage using N-containing porous organic cages

Two distinct N-containing POCs show exceptional Br2 vapor adsorption ability and different reversibility of adsorption by forming charge-transfer complexes with polybromide species, as demonstrated by experimental investigations and DFT calculations.