Theoretical Studies of Photophysical Properties of D-π-A-π-D-Type Diketopyrrolopyrrole-Based Molecules for Organic Light-Emitting Diodes and Organic Solar Cells.

A series of D-π-A diketopyrrolopyrrole(DPP)-based small molecules were designed for organic light-emitting diode(OLEDs) and organic solar cell(OSCs) applications. Applying the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results revealed that the photophysical properties were affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibited an intramolecular charge transfer feature. Our results suggest that the designed molecules acted not only as luminescent for OLEDs, but also as donor materials in OSCs. Moreover, they can also be used as potential electron transfer materials for OLEDs and OSCs.

Theoretical and experimental research on self-assembly system of molecularly imprinted polymers formed via chloramphenicol and methacrylic acid.

Chloramphenicol was chosen as the imprinting molecule and the methacrylic acid was chosen as the functional monomer to prepare molecularly imprinted polymers. Ethylene glycol dimethacrylate, pentaerythritol triacrylate, and trimethylolpropane trimethylacrylate were used as the cross-linking agents, respectively. The interaction processes between chloramphenicol and methacrylic acid were simulated by using the ωB97XD/6-31G (d,p) method. The self-assembled configuration, bonding sites, binding number, binding energy, and interaction principle of stable complex formed by chloramphenicol and methacrylic acid with different molar ratios have been studied. The selectivity of the most stable complex formed from chloramphenicol and methacrylic acid was discussed with the thiamphenicol and florfenicol as the analogues of chloramphenicol. The results showed that chloramphenicol and methacrylic acid were interacted through the hydrogen bonds. When the molar ratio was 1:10 and pentaerythritol triacrylate as the cross-linking agent, the ordered complex formed by chloramphenicol and methacrylic acid has the largest amount of hydrogen bonds and the lowest binding energy. Scatchard analysis showed that the maximum apparent adsorption capacity was 173.3 mg/g (0.536 mol/g), and the selection factor of florfenicol was the largest. This study provides a reliable theoretical and experimental basis for the design, preparation, and characterization of chloramphenicol molecularly imprinted polymers.

Theoretical Investigations of the Photophysical Properties of Star-Shaped π-Conjugated Molecules with Triarylboron Unit for Organic Light-Emitting Diodes Applications.

The density functional theory (DFT) and time-dependent DFT (TD-DFT) methodologies have been applied to explore on a series of star-shaped π-conjugated organoboron systems for organic light-emitting diode (OLED) materials. The compounds under investigation consist of benzene as π-bridge and different core units and triarylboron end groups. Their geometry structures, frontier molecular orbital (FMO) energies, absorption and fluorescence spectra, and charge transport properties have been investigated systematically. It turned out that the FMO energy levels, the band gaps, and reorganization energies optical are affected by the introduction of different core units and triarylboron end groups. The results suggest that the designed compounds are expected to be promising candidates for luminescent materials. Furthermore, they can also serve as hole and/or electron transport materials for OLEDs.

Design of Acceptors with Suitable Frontier Molecular Orbitals to Match Donors via Substitutions on Perylene Diimide for Organic Solar Cells.

A series of perylene diimide (PDI) derivatives have been investigated at the CAM-B3LYP/6-31G(d) and the TD-B3LYP/6-31+G(d,p) levels to design solar cell acceptors with high performance in areas such as suitable frontier molecular orbital (FMO) energies to match oligo(thienylenevinylene) derivatives and improved charge transfer properties. The calculated results reveal that the substituents slightly affect the distribution patterns of FMOs for PDI-BI. The electron withdrawing group substituents decrease the FMO energies of PDI-BI, and the electron donating group substituents slightly affect the FMO energies of PDI-BI. The di-electron withdrawing group substituents can tune the FMOs of PDI-BI to be more suitable for the oligo(thienylenevinylene) derivatives. The electron withdrawing group substituents result in red shifts of absorption spectra and electron donating group substituents result in blue shifts for PDI-BI. The -CN substituent can improve the electron transport properties of PDI-BI. The -CH3 group in different positions slightly affects the electron transport properties of PDI-BI.

Study on Dicyandiamide-Imprinted Polymers with Computer-Aided Design.

With the aid of theoretical calculations, a series of molecularly imprinted polymers (MIPs) were designed and prepared for the recognition of dicyandiamide (DCD) via precipitation polymerization using acetonitrile as the solvent at 333 K. On the basis of the long-range correction method of M062X/6-31G(d,p), we simulated the bonding sites, bonding situations, binding energies, imprinted molar ratios, and the mechanisms of interaction between DCD and the functional monomers. Among acrylamide (AM), N,N'-methylenebisacrylamide (MBA), itaconic acid (IA), and methacrylic acid (MAA), MAA was confirmed as the best functional monomer, because the strongest interaction (the maximum number of hydrogen bonds and the lowest binding energy) occurs between DCD and MAA, when the optimal molar ratios for DCD to the functional monomers were used, respectively. Additionally, pentaerythritol triacrylate (PETA) was confirmed to be the best cross-linker among divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethylacrylate (TRIM), and PETA. This is due to the facts that the weakest interaction (the highest binding energy) occurs between PETA and DCD, and the strongest interaction (the lowest binding energy) occurs between PETA and MAA. Depending on the results of theoretical calculations, a series of MIPs were prepared. Among them, the ones prepared using DCD, MAA, and PETA as the template, the functional monomer, and the cross-linker, respectively, exhibited the highest adsorption capacity for DCD. The apparent maximum absorption quantity of DCD on the MIP was 17.45 mg/g.

Preparation of melamine molecularly imprinted polymer by computer-aided design.

Melamine was chosen as template, methacrylic acid was chosen as functional monomer, and divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane trimethylacrylate were chosen as cross-linking agents, respectively. The WB97XD/6-31G(d, p) method was used to calculate the geometry optimization of the different imprinting ratios, the action sites, the bonding situation, and the optimization of the cross-linking agents. The nature of the imprinting effect was also studied by the atoms in molecules theory. The theoretical results showed that melamine interacts with methacrylic acid by hydrogen bonding, and the melamine molecularly imprinted polymers with a molar ratio of 1:6 have the most hydrogen bonds and the most stable structure. Divinylbenzene is the best cross-linking agent for the melamine molecularly imprinted polymers. The melamine molecularly imprinted polymers were synthesized by precipitation polymerization. The results showed that the maximum adsorption capacity for molecularly imprinted polymers towards melamine is 19.84 mg/g, and the adsorption quantity of the polymers to melamine is obviously higher than that of cyromazine, cyanuric acid, and trithiocyanuric in milk. This study could provide theoretical and experimental references for the screening of the imprinting ratio and the cross-linking agent for the given template and monomer system.

Theoretical and experimental studies on the performances of barbital-imprinted systems.

By using density functional theory, we studied the interaction process between barbital and 2-vinyl-4,6-diamino-1,3,5-triazine in acetonitrile at 333 K. Barbital and 2-vinyl-4,6-diamino-1,3,5-triazine were used as the template and functional monomer, respectively. The molecularly imprinted polymer microspheres containing barbital and 2-vinyl-4,6-diamino-1,3,5-triazine were synthesized through precipitation polymerization. After removing the template molecule barbital, the average diameter of the obtained molecularly imprinted polymers was 1.45 µm. By optimizing the molar ratio of barbital and the 2-vinyl-4,6-diamino-1,3,5-triazine, the resulting molecularly imprinted polymers showed the highest adsorption for the barbital. The analysis of the Scatchard plot revealed that the dissociation constant (Kd ) and apparent maximum adsorption quantity (Qmax ) of the molecularly imprinted polymers were 30.69 mg/L and 8.68 mg/g, respectively. The study of selective adsorption showed that molecularly imprinted polymers exhibited higher selectivity for barbtital than that for 1,3-dimethyl barbituric acid and pentobarbital. Herein, the studies can provide theoretical and experimental references for the barbital-imprinted system.

Rational Design of Diketopyrrolopyrrole-Based Small Moleculesas Donating Materials for Organic Solar Cells.

A series of diketopyrrolopyrrole-based small molecules have been designed to explore their optical, electronic, and charge transport properties as organic solar cell(OSCs) materials. The calculation results showed that the designed molecules can lower the band gap and extend the absorption spectrum towards longer wavelengths.The designed molecules own the large longest wavelength of absorption spectra,the oscillator strength, and absorption region values. The optical, electronic, and charge transport properties of the designed molecules are affected by the introduction of different π-bridges and end groups. We have also predicted the mobility of the designed molecule with the lowest total energies. Our results reveal that the designed molecules are expected to be promising candidates for OSC materials. Additionally, the designed molecules are expected to be promising candidates for electron and/or hole transport materials. On the basis of our results, we suggest that molecules under investigation are suitable donors for[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and its derivatives as acceptors of OSCs.

Design of N-N ylide bond-based high energy density materials: a theoretical survey.

The generally encountered contradiction between large energy content and stability poses great difficulty in designing nitrogen-rich high-energy-density materials. Although N-N ylide bonds have been classified as the fourth type of homonuclear N-N bonds (besides >N-N<, -N[double bond, length as m-dash]N-, and N[triple bond, length as m-dash]N), accessible energetic molecules with N-N ylide bonds have rarely been explored. In this study, 225 molecules with six types of novel structures containing N-N ylide bonds were designed using density functional theory and CBS-QB3 methods. To guide future synthesis, the effects of substitution on the thermal stability, detonation velocity, and detonation pressure of the structures were evaluated under the premise that the N-N ylide skeleton remains stable. The calculations show that the bond dissociation energy values of the N-N ylide bonds of the designed 225 structures were in the range of 61.21-437.52 kJ mol-1, except for N-1NNH2. Many of the designed structures with N-N ylide bonds exhibit high detonation properties, which are superior to those of traditional energetic compounds. This study convincingly demonstrates the feasibility of the design strategy of introducing an N-N ylide bond to develop new types of energetic materials.

Photophysical properties of derivatives of 2-(2-hydroxyphen-yl)-1,3,4-oxadiazole: a theoretical study.

Five 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD) derivatives have been designed to explore their optical, electronic, and charge transport properties as charge transport and/or luminescent materials. The calculation results showed that the absorption and fluorescence wavelengths of derivatives have bathochromic shifts compared with those of HOXD. The derivatives with benzo[c]thiophene (2), benzo[d]thiazole (3), benzo[d]thieno[3,2-b]thiophene (4), and thieno[3,4-b]quinoxaline (5) fragments are expected to be promising candidates for electron transport materials. Furthermore, the derivatives 2 and 5 have better hole- and electron-transporting balance and can act as nice ambipolar materials. Derivative with benzo[c][1,2,5]thiadiazole fragment (1) and 2-5 can emit phosphorescence, which can enhance the electroluminescent efficiency that is the demanding factor for electroluminescence materials of OLEDs in flat panel display technologies. In addition, the derivatives 3 and 4 are promising luminescent materials for organic light emitting diodes (OLEDs) as well.

Molecular design of D-π-A-π-D small molecule donor materials with narrow energy gap for organic solar cells applications.

CONTEXT: Developing novel materials present a great challenge to improve the photovoltaic performance of organic solar cells (OSCs). In this paper, we designed a series of the donor-π bridge-acceptor-π bridge-donor (D-π-A-π-D) structure molecules. These molecules consist of diketopyrrolopyrrole (DPP) moiety as core, 9-hexyl-carbazole moiety as terminal groups, and different planar electron-rich aromatic groups as π-bridges. The density functional theory (DFT) and time-dependent DFT (TD-DFT) computations showed that the frontier molecular orbital (FMO) energy levels, energy gaps, electron-driving forces (ΔEL-L), open-circuit voltage (Voc), fill factor (FF), reorganization energy (λ), exciton binding energy (Eb), and absorption spectra of the designed molecules can be effectively adjusted by the introduction of different π-bridges. The designed molecules have narrow energy gap and strong absorption spectra, which are beneficial for improving the photoelectric conversion efficiency of organic solar cells. In addition, the designed molecules possess large ΔEL-L, large Voc, and FF values and low Eb when the typical fullerene derivatives are used as acceptors. The FMO energy levels of the designed molecules can provide match well with the typical fullerene acceptors PC61BM, bisPC61BM, and PC71BM. Our results suggest that the designed molecules are expected to be promising donor materials for OSCs. METHODS: All DFT and TD-DFT calculations were carried out using the Gaussian 09 code. The computational technique chosen was the hybrid functional B3LYP and the 6-31G(d,p) basis set. The benzene and chloroform solvent effects have been considered using the polarized continuum model (PCM) at the TD-DFT level. The simulated absorption spectra of designed molecules were plotted by using the GaussSum 1.0 program.

Enhancing electrocatalytic methanol oxidation of Pd-Ir nanoalloy through electron-rich catalytic interface induced by incorporating phosphorus.

Incorporating less expensive nonmetal phosphorus (P) into noble metal-based catalysts has become a developing strategy to enhance the catalytic performance of electrocatalysts for methanol electrooxidation reaction (MOR), attributing to the electronic and synergistic structure alteration mechanism. In the work, three-dimensional nitrogen-doped graphene anchoring ternary Pd-Ir-P nanoalloy catalyst (Pd7IrPx/NG) was prepared by co-reduction strategy. As a multi-electron system, elemental P adjusts the outer electron structure of Pd and diminishes the particle size of nanocomposites, which heightens the electrocatalytic activity effectively and accelerate MOR kinetics in alkaline medium. The study reveals that the electron effect and ligand effect induced by P atoms on the hydrophilic and electron-rich surface of Pd7Ir/NG and Pd7IrPx/NG samples can reduce the initial oxidation potential and peak potential of COads, showing significantly enhanced the anti-poisoning ability compared with commercial Pd/C as the benchmark. Meanwhile, the stability of Pd7IrPx/NG is significantly higher than that of commercial Pd/C. The facile synthetic approach provides an economic option and a new vision for the development of electrocatalysts in MOR.

A DFT study of pyrrole-isoxazole derivatives as chemosensors for fluoride anion.

The interactions between chemosensors, 3-amino-5-(4,5,6,7-tetrahydro-1H-indol-2-yl)isoxazole-4-carboxamide (AIC) derivatives, and different anions (F(-) Cl(-), Br(-), AcO(-), and H(2)PO(4) (-)) have been theoretically investigated using DFT approaches. It turned out that the unique selectivity of AIC derivatives for F(-) is ascribed to their ability of deprotonating the host sensors. Frontier molecular orbital (FMO) analyses have shown that the vertical electronic transitions of absorption and emission for the sensing signals are characterized as intramolecular charge transfer (ICT). The study of substituent effects suggests that all the substituted derivatives are expected to be promising candidates for fluoride chemosensors both in UV-vis and fluorescence spectra except for derivative with benzo[d]thieno[3,2-b]thiophene fragment that can serve as ratiometric fluorescent fluoride chemosensor only.

Design, preparation and adsorption performances of norfloxacin molecularly imprinted polymers.

Here, norfloxacin (NOR) molecularly imprinted polymers (MIPs) exhibiting improved adsorption and selectivity properties were prepared via simulation and experiment. NOR and methacrylic acid (MAA) were employed as the imprinting molecule and functional monomer, respectively. The imprinting ratio, as well as cross-linking agents of the NOR-MIPs, had been optimised via the LC-ωPBE/6-31G(d,p) method. The nature and mechanism of the interaction between MIPs and MAA, as well as the selectivity of the NOR-MAA stable complex (1:1), were also discussed. Based on the simulation results, the effects of the different imprinting ratios and cross-linking agents on the adsorption of NOR-MIPs were also investigated. Concurrently, the affinity, selectivity and stability of NOR-MIPs were analysed via dynamic, static and selective adsorption, as well as thermogravimetry. The calculated and experimental results demonstrated that the stable complexes comprising NOR and MAA were formed via hydrogen bonding. The complex comprising NOR and MAA in an interaction ratio of 1:6 exhibited the highest number of hydrogen bonds and the lowest binding energy. Trihydroxymethylpropyl trimethylacrylate was more appropriate for the synthesis of NOR-MIPs compared with the two other cross-linking agents. NOR-MIPs achieved the excellent selective adsorption of NOR in single and multiple adsorption systems. This design and synthesis strategy availed a new idea for the efficient preparation of s with specific adsorption performance.

Synthesis, Crystal Structures and Antibacterial Activities of N,N'-Ethylene-bis(3-bromosalicylaldimine) and Its Copper(II) and Cobalt(III) Complexes.

A bis-Schiff base N,N'-ethylene-bis(3-bromosalicylaldimine) (H2L) was prepared from 3-bromosalicylaldehyde and ethane-1,2-diamine. With H2L as ligand, a new copper(II) complex [CuL] (1) and a new cobalt(III) complex [CoL(NCS)(DMF)] (2) were prepared and characterized by physico-chemical methods and single crystal X-ray analysis. X-ray analysis indicates that the Cu atom in complex 1 is in square planar coordination, and the Co atom in complex 2 is in octahedral coordination. The compounds were tested in vitro for their antibacterial activities on Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens. Both complexes have effective activities on the bacteria.

In-situ oxidation of Palladium-Iridium nanoalloy anchored on Nitrogen-doped graphene as an efficient catalyst for methanol electrooxidation.

Palladium (Pd)-based materials have been widely used as catalysts for the methanol oxidation reaction (MOR). Unfortunately, the catalytic activity was limited by structure, carbon monoxide intermediates (COads) tolerance and stability. It was currently difficult to be used in large-scale commercial production. Herein, to further improve their electrocatalytic activity, a facile oxidation method to achieve in-situ oxidation of palladium-iridium (PdIr) alloy on nitrogen-doped graphene (NGS) is used, which is named as Pd-Ir-O/NGS. The new catalyst exhibits remarkable MOR activity (1374.8 mA mg-1), COads tolerance (the onset oxidation potential reach 0.725 V) and stability (the current density retention rate after 500 cycles of cyclic voltammetry is 44.9%). As a catalyst for MOR, the Pd-Ir-O/NGS has more outstanding electrocatalytic performance compared with commercial Pd/C and other counterparts. The mechanism study shows that the excellent catalytic performance is attributed to (1) the synergistic electronic effect of Pd-Ir-O due to the introduction of Ir and O, (2) the insertion of O into PdIr alloy that kinetically accelerated the oxidation of poisoning methoxy intermediates and (3) the vital roles of unique three-dimensional (3D) structure of NGS with abundant nitrogen atoms. Our findings herald a new paradigm for the modification of palladium-based materials for MOR and provide an alternative design principle for novel 3D carbon-based material for various application.

Mxene coupled over nitrogen-doped graphene anchoring palladium nanocrystals as an advanced electrocatalyst for the ethanol electrooxidation.

Development of good support materials is widely adopted as a valid strategy to fabricate high performance electrocatalysts for the ethanol oxidation reaction (EOR). In this study, the small diameter Ti3C2Tx MXene thin nanosheets inserted into three-dimensional nitrogen-doped grapheme (NG) was constructed via a facile hydrothermal method and employed as support materials for anchoring Pd nanocrystals (Pd/Ti3C2Tx@NG). The obtained-Pd/Ti3C2Tx@NG as EOR electrocatalyst in alkaline media outperforms the commercial Pd/C with better electrocatalytic activity, enhanced long-term stability and high CO tolerance. The Ti3C2Tx inserted into NG probably plays a key role for enhancing the properties of the synthesized-catalyst. Inserting Ti3C2Tx into NG allows the electrocatalysts to have high porosity, surface hydrophilicity, sufficient number of anchor sites for Pd nanocrystals and modifies its electronic properties, which can promote the electrocatalytic activity and durability. The enhanced EOR performance endows Pd/Ti3C2Tx@NG with great application potential in fuel cells as an anode catalyst. Furthermore, the prepared Ti3C2Tx@NG is also suitable in various desired applications, especially other oxidation reactions.

Metal-organic interface engineering for coupling palladium nanocrystals over functionalized graphene as an advanced electrocatalyst of methanol and ethanol oxidation.

Adjusting the surface structures and electronic structures of metal nanocrystals (NCs) by the metal-organic interface interaction is an emerging strategy to enhance their electrocatalytic behavior. In this work, the d-phenylalanine-functionalized graphene (DPHE-GS) anchoring Pd NCs (denoted as Pd/DPHE-GS) was fabricated via the diazo-reaction followed by a simple chemical reduction. Owing to the metal-organic interface interaction between Pd NCs and DPHE, the size, distribution and electronic structures of Pd NCs on the surface of DPHE-GS can be adjusted. Therefore, the Pd/DPHE-GS shows the highest electrocatalytic activity and the most robust long-term durability and stability towards methanol and ethanol oxidation reaction (MOR and EOR) compared to the commercial Pd/C and other counterparts. This work presents an effective interface engineering strategy to enhance electrocatalytic property.

Design of sensitizer with suitable frontier molecular orbital via substitution on starburst triphenylamine derivative.

Herein, a series of organic molecules were designed through locating different substituents on the compound (WD8-c-1) to develop their performances used as the sensitizers in the field of dye-sensitized solar cells. The geometry and relevant electronic properties of WD8-c-1 and its derivatives were simulated at the B3LYP/6-31G(d,p) level. The absorption spectra were calculated using the TD-PBE0/6-31+G(d,p) method. These calculated results show that the type and position of the substituents strongly affected the distributions of frontier molecular orbitals and the energy gaps for the WD8-c-1-derived molecules. The reorganization energies results reveal that their hole charge transfer rates are higher than that of the representative hole transport material. Moreover, the mobility of the representative WD8-c-1 derivative also has been simulated. The starburst triphenylamine with suitable substituent has the more suitable FMO energy to match those of TiO2, broad absorption region, smaller reorganization energies, and high hole mobility.

Surface engineering of copper sulfide-titania-graphitic carbon nitride ternary nanohybrid as an efficient visible-light photocatalyst for pollutant photodegradation.

Advanced photocatalyst is a key for photocatalytic water purification in the environmental pollutant remediation. In this study, graphitic carbon nitride (g-CN) modified by CuS and TiO2 ternary nanohybrid (CuS-TiO2-g-CN) with close interfacial contact among CuS, TiO2 and g-CN was fabricated through a facile and green method. Compared to the binary g-CN-based counterparts, the CuS-TiO2-g-CN possesses multiple photo-generated charge transfers owing to the synergistic action of CuS, TiO2 and g-CN. And hence the separation efficiency of photo-generated electron-hole pairs can be improved for the CuS-TiO2-g-CN. The optical and photoelectrochemical measurements prove that the CuS-TiO2-g-CN has narrower band gap energy and higher transient photocurrent density than those of g-CN and TiO2-g-CN. Therefore, the CuS-TiO2-g-CN shows notably higher photocatalytic activity and stability towards the degradation of Rhodamine B (RhB) than g-CN and TiO2-g-CN under visible-light irradiation. Moreover, a possible visible-light photocatalytic mechanism of CuS-TiO2-g-CN for degrading RhB was also proposed on the basis of the experimental results and literature reports.