Single Phenyl Ring Research Articles

Multiple resonance delayed fluorescence emitter with C3 symmetry for high-performance solution-processed OLEDs

Solution-processed organic materials that exhibit both high emission efficiency and narrowband emission characteristics are rare, and the performance of corresponding solution-processed organic light-emitting diodes (sOLEDs) remains inadequate for practical applications. This study proposes a proof-of-concept design aimed at enhancing both solution processing capability and emission efficiency in multiple-resonance induced thermally activated delayed fluorescence (MR-TADF) materials through the integration of multiple emitting units. A unique emitter named TriBNCz is synthesized and characterized, incorporating three MR-building blocks onto a single phenyl ring, resulting in sky-blue emission with a peak at 490 nm and a small full width at half maximum (FWHM) of 25 nm. Significant improvements in solution processing attributes, including solubility and film-forming properties, are achieved. Moreover, except for the MR effect of the excited states, long-range charge transfer properties of excited states are also obtained. The multiple charge transfer channels contribute to higher rate of reverse intersystem crossing (kRISC). The optimized sOLED device exhibits a maximum external quantum efficiency (EQEmax) of 17.8 %. Furthermore, by employing 5TCzBN as a sensitizer, the sensitized sOLED achieves an EQEmax of 28.8 % and a high-level EQE of 26.1 % at 1000 cd m−2, with an FWHM of 30 nm and Commission Internationale de I’Éclairage (CIE) coordinates of (0.103, 0.497), representing one of the best results among narrowband emission sOLEDs. This research opens a new avenue to develop high-performance solution-processed organic materials and sOLED devices.

Enhanced Thermoelectricity in Metal–[60]Fullerene–Graphene Molecular Junctions

The thermoelectric properties of molecular junctions consisting of a metal Pt electrode contacting [60]fullerene derivatives covalently bound to a graphene electrode have been studied by using a conducting-probe atomic force microscope (c-AFM). The [60]fullerene derivatives are covalently linked to the graphene via two meta-connected phenyl rings, two para-connected phenyl rings, or a single phenyl ring. We find that the magnitude of the Seebeck coefficient is up to nine times larger than that of Au-C60-Pt molecular junctions. Moreover, the sign of the thermopower can be either positive or negative depending on the details of the binding geometry and on the local value of the Fermi energy. Our results demonstrate the potential of using graphene electrodes for controlling and enhancing the thermoelectric properties of molecular junctions and confirm the outstanding performance of [60]fullerene derivatives.

Experimental measurement and theoretical prediction of the adhesion force between a single phenyl ring and graphene

The adhesion force between a single phenyl ring and monolayer graphene was measured and calculated through experimental and theoretical methods. We used a method based on Poisson distribution statistics to extract the single-bond force between a single phenyl ring and monolayer graphene using an atomic force microscope (AFM) in water environment. The single-bond force was measured as 190.6 ± 8.1 pN, which was in good agreement with the previous research. Based on the experimental results, we proposed a theoretical model of atomic scale to elucidate the formation process of the single-bond force. The single-bond force was the maximum force in the desorption process, which was divided into two stages: processes A and B. The phenyl ring was lifted up and rotated simultaneously from the state of parallel to perpendicular to graphene in process A; it kept moving upward in the perpendicular direction in process B. The single-bond force of 190.6 pN appeared in process A when the ratio of the vertical lifting height and rotating lifting height was 0.981, which was most consistent with experimental result. Moreover, any force curve measured from experiment could be obtained by fitting the single-bond force curve calculated from theory.

Simultaneous Suppression of π- and σ-Transmission in π-Conjugated Molecules

Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts toward molecular insulators focused on saturated molecules, it remains an open question whether π- and σ-transport can be simultaneously suppressed in conjugated systems. Here, we demonstrate that there are conjugated molecules where the σ-transmission is suppressed by destructive σ-interference, while the π-transmission can be suppressed by a localized disruption of conjugation. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by various structural changes in the molecule. We find that in para-linked oligophenyl rings the σ-transmission can be suppressed by changing the remaining hydrogens to methyl groups due to the inherent gauche-like structure of the carbon backbone within a benzene ring, similar to what was previously seen in saturated systems. At the same time, the methyl groups fulfill a dual purpose as they modulate the twist angle between neighboring phenyl rings. When neighboring rings are orthogonal to each other, the transmission through both π- and σ-systems is effectively suppressed. Alternatively, breaking conjugation in a single phenyl ring by saturating two carbons atoms with two methyl substituents on each carbon, results in suppressed π- and σ-transport independent of dihedral angle. These two strategies demonstrate that methyl-substituted oligophenyls are promising candidates for the development of molecular dielectric materials.

The Immobilization of Oxindole Derivatives Using New Designed Functionalized C60 Nanomolecules

Indirubin and its analogs such as oxindole derivatives are well known as competitive inhibitors of cyclin-dependent kinase 2 (CDK2) and play an important role in the creation of therapies in many cancer diseases. Recent research, in order to increase efficiency, is aimed at creating targeted therapy, which is often based on the immobilization of drugs on the surface of nanocarriers. In this work, two oxindole derivatives were used to test the binding capabilities of newly in silico designed C60 fullerene derivatives. Seventy functionalized nanostructures were created by the addition of amino acid substituents to the single phenyl ring attached to the fullerene surface. Realized calculations, based on flexible docking methods, allowed for obtaining energetic characteristics and structural aspects of complexes created by nanomolecules with considered ligands. Analysis of obtained complexes shows that symmetric substitution to position R3 and R5 allows obtaining fullerene derivatives exhibiting the highest binding capabilities, while the lowest ones are the effect of asymmetric substitution (R2; R4). Obtained values clearly allowed to select a group of substituents and substitution sites that provide the most stable complexes which can be used to create new nanocarriers for the group of drugs under consideration.

Catalytic co-aromatization of methane and heptane as an alkane model compound over Zn-Ga/ZSM-5: A mechanistic study

The joint conversion of methane and heptane, a model compound of paraffin-rich raffinate oil, over a Zn-Ga modified zeolite catalyst has been investigated at various reaction times. In comparison with the performance from a N2 environment, the introduction of methane highly promotes the formation of light aromatic compounds with a single phenyl ring, and increased carbon number and substitution index of chemical constituents formed are indicative of methane incorporation into the liquid product. In addition, with prolonged time, the interaction between catalyst and methane molecules is enhanced. Through cleavage of methane molecules, the formed moieties likely participate in the aromatization reaction, which results in the growth of larger aromatic components through further condensation. According to the NMR spectra, witnessing methane engagement into the phenyl carbon and alkyl carbon sites of the formed liquid aromatics along with increasing reaction time is evidenced 13C-methane incorporation into aromatics. The excellent catalytic performance of Zn-Ga/ZSM-5 might be ascribed to the greatly dispersed metal species on the catalyst surface as well as a certain amount of medium and weak acid sites. With regards to the spent catalyst, the presence of methane could inhibit the aggregation of loaded active metals and coke formation during the co-aromatization process. The elucidation on the co-conversion of methane and high alkane provides great potential for the utilization of natural gas resources and intermediates formed from petrochemical industries.

The length and hydrogenation effects on electronic transport properties of carbon-based molecular wires

Abstract It is known that the conductance of a wire decreases linearly with the increase of its length in the macro circuit. But things are different in mesoscopic field, especially in molecular dimensional circuits due to the quantum interferences in molecular size. In this work, first principles is used to investigate how wire length and hydrogenation degree influence the conductance of molecular wires. For comparison, two types of carbon-based molecular wires, single carbon atomic wire and phenyl ring wire with single hydrogenation or dihydrogenation, are chosen and coupled to two zigzag graphene nanoribbon electrodes, respectively. We show that the conductance of zigzag carbon atomic wire with single hydrogenation exhibits an evident even-odd oscillatory behavior with the increase of wire length, while that of phenyl ring wire starts to increase before decreasing. However, when the above types of wires are edged with dihydrogenation, their conductance decreases exponentially with the increasing wire length. In addition, fine current rectification is found in asymmetric phenyl wires induced by hydrogenation degree, which can be used as diode in future molecular devices. Analyses via orbital hybridization, transmission path, HOMO-LUMO position and so on reveal the microscopic mechanism of the above interesting results.

Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations.

Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent.

How do the substituents affect and regulate the relative retention times of polychlorinated biphenyls during gas chromatography?

The effects and regulatory actions of the polychlorinated biphenyls (PCBs) substituent characteristics on their relative retention times (RRTs) during gas chromatography were analyzed based on known experimental RRTs of 209 PCB congeners and biphenyl; the substituent characteristics used for this analysis included the total amount of substituents, the similarity between two phenyl rings in a single PCB congener, the substituents distribution in single phenyl ring, the main/second‐order interactions effects at each position, and the combined effect of two phenyl rings. At last, the universality of regulation was validated on other experimental conditions. Among them, the full factorial experimental design included 10 factors correlated with each substituent position and two levels (0, 1) were initially applied to the domains of the substituent characteristics. The obtained results have revealed that increasing the total amount of substituents can increase the RRTs of PCBs linearly, but similarities between the two rings cannot control the RRTs effectively. Meanwhile, the more compact the substituent distributions on a single phenyl ring are, the bigger the RRTs of PCBs are. Based on a full factorial experimental design, the overall important trend for each position is as follows: para > meta > ortho and the main regulatory substituents for the second‐order interaction effects are distributed in the same phenyl ring in the following sequence: No > Nm > Np. The congener with two perpendicular phenyl rings exhibits a milder combined effect on RRTs and smaller RRT relatively. The regulation has a good universality among different experimental conditions, revealing the dominant effect of substituent characteristics on RRTs of PCBs. Copyright © 2015 John Wiley & Sons, Ltd.

Combined 1H NMR and LSER study for the compound-specific interactions between organic contaminants and organobentonites

The compound-specific mechanisms for the sorption of organic contaminants onto cetyltrimethylammonium-saturated bentonite (i.e., CTMA-Bentonite) in water were evaluated by 1H NMR study and Linear Solvation Energy Relationship (LSER) approach. In 1H NMR study, comparing with pure CTMAB, the up-field shifts of hydrogen peaks for CH2N+ and CH3N+ of CTMA+ in CTMAB-aromatics (1-naphtylamine, aniline and phenol) mixtures are much greater than that in CTMAB-aliphatics (cyclohexanone and cyclohexanol) mixtures. Meanwhile, the peak position of hydrogen on amino- and hydroxyl-groups of aromatic compounds also changes greatly. 1H NMR data demonstrated the strong molecular interaction between the positive ammonium group of CTMA+ and the delocalized π-systems of aromatic solutes, whereas the interactions of CTMA+ with aliphatic compounds having electron-donating groups (such as cyclohexanol and cyclohexanone) or aromatic ring substituted by electron-withdrawing groups (i.e., nitrobenzene) or nonpolar aromatic compounds with single phenyl ring (i.e., toluene) are weak. The derived LSER equation was obtained by a multiple regression of the solid–water sorption coefficients (Kd) of 16 probe solutes upon their solvation parameters, and demonstrates aromatics sorption onto CTMA-Bentonite is concurrently governed by the π-/n-electron pair donor–accepter interaction and the cavity/dispersion interaction, while the predominant mechanism for aliphatic compounds is the cavity/dispersion interaction, consisting with the 1H NMR results.

Effect Analysis of Substituent Characteristics of PBDEs on Its Ah Receptor Binding Affinities

Based on the known experimental Ah receptor binding affinities of 18 kinds of polybrominated diphenyl ethers (PBDEs), the quantitative structure-activity relationships (QSAR) model for PBDEs’ Ah receptor binding affinities was established via 13 substituent parameters (total number of substituent, substituent number in different position, substituent positional relationship parameters, substituent difference between two rings) to complement unknown binding affinities of other 191 PBDEs. Then, the full factorial experiment with 10 factors which correlated with each substituent position and 2 level (0,1) was applied to analyze the main effect and second-order interaction effect of each substituent position on PBDEs’ Ah receptor binding affinities. Meanwhile, different analysis methods were used for the views of the total number of substituent, the similarity of different phenyl ring in single congener and the distribution of substituents on single phenyl ring to expound the correlation between substituent characteristics and Ah receptor binding affinities of PBDEs comprehensively. The obtained results have shown that: PBDEs’ Ah receptor binding affinities are significantly affected by the main effect and second-order interaction effect of substitution positions, especially, the ortho-substituents can weaken the PBDEs’ Ah receptor binding affinities and para-substituents have the opposite effect. The order of the importance for different position is presented as: para>ortho>meta. The main effect of meta-substituent is small which often affects the Ah receptor binding affinities of PBDEs by representing the second-order interaction effects combined with ortho/para-substituent. For other substituent characteristics, the total number of substituent and the similarity of different phenyl ring in single congener cannot control the Ah receptor binding affinities of PBDEs effectively, but the more decentralized for substituents on single phenyl ring, the smaller Ah receptor binding affinities for PBDEs.

Resonance Enhancement via Imidazole Substitution Predicts New Cation Receptors

Design and development of cation receptors represent a fascinating area of research, particularly in dealing with chemical and biological applications that require fine-tuning of cation-π interactions. The electronic nature of a substituent is largely responsible for tuning the strength of cation-π interaction, and recent studies have shown that substituent resonance effect contributes significantly to such interactions. Using substituent resonance effect as a key electronic factor, we have proposed new cation-π receptors (1···M(+)-4···M(+); M(+) = Li(+), Na(+), K(+), NH4(+), and NMe4(+)). B3LYP/6-311+G(d,p) density functional theory (DFT) calculations show that by using a strategy of resonance donation from six nitrogen atoms via three substituted imidazole subunits, more than 4-fold increase in cation-π interaction energy (E(M)(+)) can be achieved for a single phenyl ring compared to benzene. The E(M)(+) (M(+) = NH4(+), NMe4(+)) of 4···M(+), wherein M(+) interacts with only one phenyl ring, is significantly higher than E(M)(+) of a known cation host with several aromatic rings (abstract figure). Our hypothesis on resonance enhancement of cation-π interaction is verified using several π-systems (5-10) containing a lone pair bearing six nitrogens and observed that a nitrogen lone pair attached to a double bond is more effective for donation than the lone pair that is directly attached to the benzenoid ring. Further, a convenient strategy to design electron rich π-systems is provided on the basis of topographical analysis of molecular electrostatic potential.

Preference of the monodentate contact in the CH/π interaction between an alkyl group and a single phenyl ring: Stable structures of benzene–ethane clusters

Infrared spectroscopy has been applied to benzene–ethane clusters to investigate the preferential contact structures due to the CH/π interaction between an alkyl group and a single phenyl ring. Stable structure search of the clusters by high-level ab initio calculations has been also carried out. The observed infrared spectra are well accounted for by the presence of the isomer which has the monodentate structure. The speculated isomer with a tridentate structure has been ruled out by analyses of the observed infrared spectra and theoretical calculations.

Synthesis, characterization and surface wettability of polythiophene derivatives containing semi-fluorinated liquid-crystalline segment

In the scope of increasing our knowledge on the elaboration of smart surfaces, the aim of this work was to synthesize monomers as starting materials for the polymerization or copolymerization via electrochemical route. We report the synthesis and characterization of original structures containing a single phenyl unit bound, on one side, to a semi-fluorinated tail via a thioester connector and, on the other side, to a thiophene moiety. This design approach using cheap raw materials (a single phenyl ring as mesogenic core) associated to an electropolymerizable unit is of great interest in the development of liquid crystal low cost materials to build-up non-wetting surfaces based on the fluorophobic effect. The mesomorphic properties were characterized using differential scanning calorimetry and optical polarizing microscopy. The effect of the length of the fluorinated tail induced the formation of a smectic enantiotropic mesophase for F-hexyl and F-octyl tails. The polymerization of the films was performed in solution of sodium perchlorate in acetonitrile. Hydrophobic surfaces were obtained from the monomers containing a F-hexyl and F-octyl tail, while superhydrophobic surfaces (contact angle of water of 158°) were reached from the monomer containing a F-butyl tail.

Inhibition and disaggregation of α-synuclein oligomers by natural polyphenolic compounds

Aggregation of alpha-synuclein (αS) into oligomers is critically involved in the pathogenesis of Parkinson’s disease (PD). Using confocal single-molecule fluorescence spectroscopy, we have studied the effects of 14 naturally-occurring polyphenolic compounds and black tea extract on αS oligomer formation. We found that a selected group of polyphenols exhibited potent dose-dependent inhibitory activity on αS aggregation. Moreover, they were also capable of robustly disaggregating pre-formed αS oligomers. Based upon structure–activity analysis, we propose that the key molecular scaffold most effective in inhibiting and destabilizing self-assembly by αS requires: (i) aromatic elements for binding to the αS monomer/oligomer and (ii) vicinal hydroxyl groups present on a single phenyl ring. These findings may guide the design of novel therapeutic drugs in PD. Structured summary of protein interactions Alpha-synuclein binds to Alpha-synuclein by biophysical (View Interaction 1, 2)

Inducing the Rotation of a Single Phenyl Ring with Tunneling Electrons

We report on the electron induced intramolecular rotation of a single phenyl ring of an azobenzene derivative adsorbed on a Au(111) surface using a low-temperature scanning tunneling microscope (STM). By proper functionalization of each of the two azobenzene's phenyl rings with CN end groups, we are able to identify two distinct isomers at the metal surface corresponding to two possible alignments of the functional groups in the trans conformer. Tunneling electrons induce molecular motion and intramolecular conformational changes both on isolated molecules and H-bonded molecular islands. Particular enhancement is observed for the electrons resonantly tunneling through affinity levels, which is consistent with electronic molecular excitations as the basic mechanism for this manipulation process. On the basis of quantum chemical calculations of a free azobenzene molecule, we propose a dynamical model for the ring-rotation pathways, which includes the electric field in the STM junction to effectively couple electronic excitation with intramolecular rotations.

New binucleating ligand with two [P,S] chelation pockets on a single phenyl ring: Syntheses and X-ray structures of 1,4-bis(diphenylphosphino)-2,5-difluoro-3,6-bis(methylthio)benzene and of bimetallic complex (CO) 3Fe(μ-[(PPh 2)(SMe)C 6F 2(SMe)(PPh 2)])Fe(CO) 3

Double deprotonations of 1,4-dibromo-2,5-difluorobenzene with LDA (2 equiv., T < −90 °C) generate a reasonably stable organodilithium intermediate. Quenching this reaction mixture with chlorophosphines ClPR 2 produce p-bis(phosphino)benzenes R 2P–C 6Br 2F 2–PR 2 (R = Ph, 4a; R = iPr, 4b). Facile lithium–bromine exchange occurs upon exposure of 4a to BuLi (2 equiv., −80 °C), leading to the generation of another organodilithium intermediate. Addition of MeS–SMe (2 equiv.) to such reaction mixtures gives 1,4-bis(diphenylphosphino)-2,5-difluoro-3,6-bis(methylthio)benzene ( 2). Compound 2 is the first example of a neutral binucleating ligand featuring the [P,S] chelating sites on the opposite sides of a single phenyl ring. Compound 4b does not undergo the analogous transformation when subjected to the same conditions (2BuLi/2MeS–SMe). Addition of 2 to Fe(CO) 5/2(Me 3NO · 2H 2O) reaction mixtures led to the isolation of the bimetallic complex {(CO) 3Fe[P,S]–C 6F 2–[P,S]Fe(CO) 3} ( 3), ([P,S] represents the chelating pockets formed by adjacent –PPh 2 and –SMe groups). All of the new compounds were characterized by spectroscopic and analytical techniques (multinuclear NMR, mass-spectrometry, and/or elemental analysis). In addition, compounds 2 and 3 were characterized via single crystal X-ray diffraction methods.

Electronic Interactions in Tertiary Oligophenylureas

The syntheses, structures, and spectroscopy of a series of oligomeric tertiary oligophenylureas possessing one to five phenyl rings are reported. A convergent synthetic method employing tertiary monoamine and diamine building blocks is employed. NMR and molecular modeling are indicative of folded structures for all of the oligophenylureas in which adjacent phenyl rings have a splayed face-to-face geometry. NMR chemical shifts, absorption and emission maxima, and electrochemical oxidation potentials are all dependent upon the number of phenyl rings. The addition of a first inner phenyl has a pronounced effect on the chemical shifts, while a second and third inner phenyl have diminished effects. The oxidation potentials of the oligophenylureas display an abrupt decrease upon the addition of the second inner phenyl. The absorption and emission spectra are relatively insensitive to the addition of one to three inner phenyl rings. The electronic structures of the oligophenylureas possessing one to eight rings have been analyzed using ZINDO calculations. The frontier orbitals of the ureas with one to three phenyl rings are localized on a single phenyl ring (the inner ring for the three-ring urea), whereas the frontier orbitals of the higher oligomers are delocalized over two phenyl rings. In all cases, urea-localized n,pi* transitions are lower in energy than the phenyl-localized pi,pi* transitions. The changes in properties with added phenyl rings parallel those previously observed for multilayered cyclophanes; however, they are less pronounced because of weaker coupling between the phenyl rings of the oligophenylureas.

Palladium-Catalyzed Cross-Coupling Reactions in the Synthesis of Novel Aromatic Polymers

Several novel aromatic polymers have been prepared through palladium-catalyzed cross-coupling reactions involving two single phenyl ring units, one containing two bromo substituents and the other containing either two boronic ester moieties or two tributyltin moieties. These sets of reactions were carried out under different conditions (catalyst, solvent, and base) in order to optimize the yield, the degree of polymerization, and the polydispersity. Following optimization of the reaction conditions, a series of novel, substituted polymers were prepared to show the scope of the methodology. The synthesis of the polymerizable aromatic intermediates proved interesting and challenging, particularly those with many substituents. The novel polymers generated are discussed in terms of their synthetic methods, degree of polymerizations, and polydispersities.

Structural determinants of HERG channel block by clofilium and ibutilide.

Block of human ether-a-go-go related gene (HERG) K(+) channels by a variety of medications has been linked to acquired long QT syndrome, a disorder of cardiac repolarization that predisposes to lethal arrhythmias. The drug-binding site is composed of residues that face into the central cavity of the channel. Two aromatic residues located on the S6 domain (Tyr652 and Phe656) are particularly important structural determinants of drug block. The role of pore helix residues (Thr623, Ser624, Val625) is less clear. In this study, we compared the pharmacological properties of two structurally related compounds, ibutilide and clofilium. Both compounds are charged amines with a single phenyl ring. Clofilium, a chlorobenzene derivative, is a potent blocker of HERG channels, but has a remarkably slower time course for recovery from block than ibutilide, a methanesulfonanilide. The difference in the rate of recovery from block can be explained simply by variation in drug trapping. There is little recovery from clofilium block with D540K HERG channels that permit untrapping at hyperpolarized potentials. Alanine-scanning mutagenesis of the S6 domain and a portion of the pore helix revealed that the binding site residues were the same for both compounds. However, S624A, located at the base of the pore helix, was the only HERG mutation that enabled rapid recovery from clofilium block. In summary, the pore helix residues are important components of the HERG drug binding site, and may be particularly important for drugs with polar substituents, such as a halogen (e.g., clofilium) or a methanesulfonamide (e.g., ibutilide).