Central Phenyl Research Articles

Synthesis and Pharmacological Evaluation of 1-Phenyl-3-Thiophenylurea Derivatives as Cannabinoid Type-1 Receptor Allosteric Modulators.

We previously reported diarylurea derivatives as cannabinoid type-1 receptor (CB1) allosteric modulators, which were effective in attenuating cocaine-seeking behavior. Herein, we extended the structure-activity relationships of PSNCBAM-1 (2) at the central phenyl ring directly connected to the urea moiety. Replacement with a thiophene ring led to 11 with improved or comparable potencies in calcium mobilization, [35S]GTPγS binding, and cAMP assays, whereas substitution with nonaromatic rings led to significant attenuation of the modulatory activity. These compounds had no inverse agonism in [35S]GTPγS binding, a characteristic that is often thought to contribute to adverse psychiatric effects. While 11 had good metabolic stability in rat liver microsomes, it showed modest solubility and blood-brain barrier permeability. Compound 11 showed an insignificant attenuation of cocaine seeking behavior in rats, most likely due to its limited CNS penetration, suggesting that pharmacokinetics and distribution play a role in translating the in vitro efficacy to in vivo behavior.

Nematic and switchable intercalated phases in polymerizable bent-core monomers with naphthalene moiety in the side arms of the aromatic core

Liquid crystals (LCs) formed by achiral bent-core (BC) molecules associated with chirality and polar order exhibit electro-optically switchable lamellar and columnar phases, and nematic phases which could be biaxial or polar. As polymeric LCs could have application in photonics and non-linear optics, BC monomers having naphthalene moiety in the side arms and linked with terminal double bonds as polymerizable functional groups were synthesized. 6B2 with a central phenyl ring and 6N2 with a central naphthalene moiety were investigated by optical, x-ray diffraction, dielectric and electro-optic studies. Possible reasons that can account for the exhibited phase transitions will be described.

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks.

We report the synthesis of five dicarboxylic acid-substituted dipolar molecular rotors for the use as linker molecules in metal-organic frameworks (MOFs). The rotor molecules exhibit very low rotational barriers and decent to very high permanent, charge free dipole moments, as shown by density functional theory calculations on the isolated molecules. Four rotors are fluorescent in the visible region. The linker designs are based on push–pull-substituted phenylene cores with ethynyl spacers as rotational axes, functionalized with carboxylic acid groups for implementation in MOFs. The substituents at the phenylene core are chosen to be small to leave rotational freedom in solids with confined free volumes. The dipole moments are generated by electron-donating substituents (benzo-1,3-dioxole, benzo-1,4-dioxane, or benzo-2,1,3-thiadiazole annelation) and withdrawing substituents (difluoro, or dicyano substitution) at the opposite positions of the central phenylene core. A combination of 1,4-dioxane annelation and dicyano substitution generates a theoretically predicted, very high dipole moment of 10.1 Debye. Moreover, the molecules are sufficiently small to fit into cavities of 10 Å3. Hence, the dipolar rotors should be ideally suited as linkers in MOFs with potential applications as ferroelectric materials and for optical signal processing.

Effect of substituted nitrogen atom location on the photophysical and charge transporting properties of carboline derivatives

In this work, three carboline derivatives, 9,9′-m-phenylenedi-α-carboline (NmCP1), 9,9′-m-phenylenedi-β-carboline (NmCP2), and 9,9′-m-phenylenedi-γ-carboline (NmCP3) were designed and synthesized to examine the effect of nitrogen atom position on the photophysical and charge transport properties of carboline derivatives. NmCP1 with α-carboline showed high hole and electron current density in the single carrier device owing to formation of π-π stacking by weak hydrogen bond between α-carbaoline and a phenyl linker from single crystal analysis. Whereas, NmCP2 and NmCP3 were advantageous to increase the triplet energy due to the distortion of the carboline unit from the central phenyl unit. Among the three compounds, the NmCP1 achieved high external quantum efficiency of 18.6% in the deep blue phosphorescent organic light-emitting diodes. Therefore, the control of the nitrogen position could manage the carrier transport properties, photophysical properties and device performances of the carboline derivatives. • Design and synthesis of three carboline derivatives with different nitrogen positions. • Efficient charge transport properties by molecular stacking in the carboline derivatives. • High external quantum efficiency close to 20% in the deep blue phosphorescent organic light-emitting diodes.

Tetravalent Pseudomonas aeruginosa Adhesion Lectin LecA Inhibitor for Enhanced Biofilm Inhibition

AbstractA potent divalent ligand of the Pseudomonas aeruginosa adhesion lectin LecA was elaborated into a tetravalent version. A polyethylene glycol (PEG) spacer was introduced to link two divalent galactosides. Each of the two divalent ligands contained a rigid spacer with a central phenyl group that is bridged by the PEG moiety. The resulting tetravalent ligand was found to bind LecA in the nanomolar range involving all of its sugar (sub)ligands. Analytical ultracentrifugation studies clearly showed that the tetravalent ligand was capable of aggregation the LecA tetramers in contrast to the divalent ligands. The aggregator behavior was found to be of importance in P. aeruginosa biofilm formation inhibition. Despite the weaker affinity it was a considerably better biofilm inhibitor with half inhibitory values around the 28 micromolar range.

Origin of the isotropic motion in crystalline molecular rotors with carbazole stators.

Herein we report two crystalline molecular rotors 1 and 4 that show extremely narrow signals in deuterium solid-state NMR spectroscopy. Although this line shape is typically associated with fast-moving molecular components, our VT 2H NMR experiments, along with X-ray diffraction analyses and periodic DFT computations show that this spectroscopic feature can also be originated from low-frequency intramolecular rotations of the central phenylene with a cone angle of 54.7° that is attained by the cooperative motion of the entire structure that distorts the molecular axis to rotation. In contrast, two isomeric structures (2 and 3) do not show a noticeable intramolecular rotation, because their crystallographic arrays showed very restricting close contacts. Our findings clearly indicate that the multiple components and phase transitions in crystalline molecular machines can work in concert to achieve the desired motion.

Sometimes the Same, Sometimes Different: Understanding Self-Assembly Algorithms in Coordination Networks.

The syntheses and characterizations of three new ligands containing two 4,2′:6′,4″-tpy or two 3,2′:6′,3″-tpy metal-binding domains are reported. The ligands possess different alkyloxy functionalities attached to the central phenylene spacer: n-pentyloxy in 3, 4-phenyl-n-butoxy in 4, benzyloxy in 5. Crystal growth under ambient conditions has led to the formation of {[Co(NCS)2(3)]·0.8C6H4Cl2}n and {[Co(NCS)2(4)]·1.6H2O·1.2C6H4Cl2}n, with structures confirmed by single crystal X-ray diffraction. Both the cobalt(II) center and ligand 3 or 4 act as 4-connecting nodes and both {[Co(NCS)2(3)]·0.8C6H4Cl2}n and {[Co(NCS)2(4)]·1.6H2O·1.2C6H4Cl2}n possess a 3D cds net despite the fact that 3 and 4 contain two 4,2′:6′,4″-tpy and two 3,2′:6′,3″-tpy units, respectively. Taken in conjunction with previously reported data, the results indicate that the role of the alkyloxy substituent is more significant than the choice of 4,2′:6′,4″- or 3,2′:6′,3″-tpy isomer in determining the assembly of a particular 3D net. The combination of Co(NCS)2 with 5 resulted in the formation of the discrete molecular complex [Co(NCS)2(MeOH)2(5)2]·2CHCl3·2MeOH in which 5 acts as a monodentate ligand. The pendant phenyls and both coordinated and non-coordinated 4,2′:6′,4″-tpy units are involved in efficient π-stacking interactions.

Angular/linear-shaped indacenodithiophene (IDT) for donor-acceptor copolymers: Geometric shape effects on physical properties and photovoltaic performance

Angular-indacenodithiophene (a-IDT) as the analogue of linear-IDT (l-IDT), in which the central phenyl ring was linked on the β-position of the thiophene ring but fused on its α-position, was designed and synthesized through intramolecular annulation. This designed dibrominated a-IDT monomer was copolymerized with 4,7-bis(4-hexylthiophen-2-yl)-2,1,3-benzothiadiazole (DTBT) as the acceptor unit through Stille coupling reaction to furnish an alternating D-A conjugated polymer Pa-IDTDTBT. Similarly, l-IDT unit and its D-A conjugated polymer Pl-DTDTBT were also synthesized for comparison. The geometric shape of l-IDT and a-IDT subunits have tremendous influence on the conjugated backbone curvature for Pl-IDTDTBT and Pa-IDTDTBT, mainly reflects in changes observed in their photoelectric properties, hole mobilities, film morphology and photovoltaic performance. Theoretical calculation concludes that Pl-IDTDTBT possesses a more linear conjugated backbone and hence stronger intermolecular π–π interactions, leading to more red-shifted absorption spectra of Pl-IDTDTBT in the solution as well as the thin film relative to those of Pa-IDTDTBT. XRD measurements demonstrated that Pl-IDTDTBT has more ordered π-stacking than Pa-IDTDTBT counterpart as a result of the less curvature of the Pl-IDTDTBT conjugated backbone. BHJ PSCs device based on Pl-IDTDTBT/PC71BM achieved a PCE of 5.34%, is higher than Pa-IDTDTBT (3.64%). As expected, Pa-IDTDBT with the more conjugated backbone curvature showed a high Voc of 1.02 V owing to its deeper HOMO energy level (−5.47 eV) relative to Pl-IDTDTBT, which is one of the highest Voc values of IDT-based polymers. Our work demonstrates that the geometric shape of subunits should be considered in designing the novel photovoltaic polymers and other organic optoelectronic materials.

Electronic Decoupling in C3-Symmetrical Light-Responsive Tris(Azobenzene) Scaffolds: Self-Assembly and Multiphotochromism.

We report the synthesis of a novel C3-symmetrical multiphotochromic molecule bearing three azobenzene units at positions 1, 3, 5 of the central phenyl ring. The unique geometrical design of such a rigid scaffold enables the electronic decoupling of the azobenzene moieties to guarantee their simultaneous isomerization. Photoswitching of all azobenzenes in solution was demonstrated by means of UV-vis absorption spectroscopy and high performance liquid chromatography (HPLC) analysis. Scanning tunneling microscopy investigations at the solid-liquid interface, corroborated by molecular modeling, made it possible to unravel the dynamic self-assembly of such systems into ordered supramolecular architectures, by visualizing and identifying the patterns resulting from three different isomers, thereby demonstrating that the multiphotochromism is retained when the molecules are confined in two dimensions.

Crystal structure of meso-3,3'-(1,4-phenyl-ene)bis-(2-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one).

The crystal structure of the title compound - meso-C26H24N2O2S2 with two stereocenters - has half the mol-ecule in the asymmetric unit with the other half generated by a crystallographic center of inversion. The thia-zine ring is in a conformation that is between half-chair and envelope [θ = 52.51 (17)°]. The phenyl ring on the 2-carbon atom of the thia-zine ring is pseudo-axial. The central phenyl ring of the mol-ecule is close to orthogonal to the phenyl rings on either side with an angle of 76.85 (11)° between those planes. In the crystal, pairwise, weak C-H⋯O hydrogen bonds between the central phenyl ring and the oxygen atoms of neighboring mol-ecules result in continuous strips propagating along the a-axis direction. Hydro-phobic inter-actions of the C-H⋯π type are also observed.

Dihedral Angle Control of Blue Thermally Activated Delayed Fluorescent Emitters through Donor Substitution Position for Efficient Reverse Intersystem Crossing.

This study shows a molecular design strategy for controlling the dihedral angle of two carbazole donors linked to a 2,4-diphenyl-1,3,5-triazine acceptor by a phenyl unit. Using this approach, six thermally activated delayed fluorescence emitters were synthesized with donors placed in various positions around a central phenyl core, and the photophysical relationship between the donor position and its dihedral angle was investigated. We demonstrate that this angle can affect both the strength of the charge transfer state and the conjugation across the entire molecule, effectively changing the singlet-triplet energy gap of the system. We conclude that materials containing two substituted -ortho donors or one -ortho and an adjacent -meta have the smallest energy gaps and the shortest delayed fluorescence lifetimes. On the other hand, emitters with no -ortho substituted donors have larger energy gaps and slow-to-negligible delayed fluorescence. When applying these materials to organic light-emitting diodes, these blue-emitting devices have a range of electrical properties, the best producing efficiencies as high as 21.8% together with high resistance to roll-off that correlate with the reverse intersystem crossing rates obtained.

3-Cyano thiophene-based π-conjugated mesogens: XRD and 13C NMR investigations

ABSTRACT3-Cyano thiophene-centred π-conjugated mesogens with alkoxy phenyl/biphenyl rings are synthesised by palladium acetate-catalysed direct arylation to investigate the mesophase properties and the molecular order. The synthesised mesogens mostly exhibit smectic A mesophase as confirmed by X-ray diffraction studies. Further, due to the manifestation of π-conjugated core, the mesogens exhibit photo luminescence in solution with emission maxima in the range 425–460 nm. Density functional theory and time-dependent density functional theory calculations of a representative mesogen indicate possible intramolecular charge transfer transition between the biphenyl to 3-cyanothiophene units. Despite structural simplicity, the observation of smectic A phase is attributed to location of strong dipole moment component perpendicular to the long axis of the molecules due to the presence of polar cyano group at 3-position of central thiophene ring. The 13C NMR studies are performed in mesophase and using the 13C–1H dipolar couplings determined from 2D separated local field experiment; the order parameters of central thiophene ring and side arm phenyl rings are calculated. Moreover, the order parameter ratios of thiophene and side arm phenyl rings indicate the bent–core nature of the mesogen.

Substituent-directed ESIPT-coupled Aggregation-induced Emission in Near-infrared-emitting Quinazoline Derivatives.

A series of ESIPT (excited state intramolecular proton transfer) active systems (HQz1-HQz6) derived from quinazoline have been reported. The ESIPT emission for these derivatives gets completely quenched in solvents with diverse polarities which have been restored via aggregation-induced emission (AIE) with large Stokes shift (up to 314 nm). It varied from 450 to 701 nm just by altering substituents at the para position of hydroxy group in the central phenyl ring. As well, HQz1-HQz6 displayed solid state emission [∼455 (blue) to ∼704 nm (red)]. The formyl group on the central hydroxy-phenyl ring of these derivatives induces ESIPT by increasing acidity of the hydroxy proton which has been followed by 1 H NMR studies. Further, it has been clearly shown that emission colour and aggregate morphology can be fine tuned by incorporating apt substituents. The present study offers a simple route to obtain colour tunable ESIPT emission via AIE which is very important for biological imaging and fabrication of optoelectronic devices.

Influence of Quantum Interference on the Thermoelectric Properties of Molecular Junctions.

Molecular junctions offer unique opportunities for controlling charge transport on the atomic scale and for studying energy conversion. For example, quantum interference effects in molecular junctions have been proposed as an avenue for highly efficient thermoelectric power conversion at room temperature. Toward this goal, we investigated the effect of quantum interference on the thermoelectric properties of molecular junctions. Specifically, we employed oligo(phenylene ethynylene) (OPE) derivatives with a para-connected central phenyl ring ( para-OPE3) and meta-connected central ring ( meta-OPE3), which both covalently bind to gold via sulfur anchoring atoms located at their ends. In agreement with predictions from ab initio modeling, our experiments on both single molecules and monolayers show that meta-OPE3 junctions, which are expected to exhibit destructive interference effects, yield a higher thermopower (with ∼20 μV/K) compared with para-OPE3 (with ∼10 μV/K). Our results show that quantum interference effects can indeed be employed to enhance the thermoelectric properties of molecular junctions.

Phenothiazine-Based Oligo(p-phenylenevinylene)s: Substituents Affected Self-Assembly, Optical Properties, and Morphology-Induced Transport.

Designing intramolecular charge-transfer (ICT)-based luminogenic ordered assemblies exhibiting significant electrical transport is a challenging task in the field of organic optoelectronics. In this context, a series of novel phenothiazine-based oligo(p-phenylenevinylene) (OPV1-6) derivatives were designed and their structure-property relationship was investigated. Upon examining their photophysical properties, all the OPVs were found to exhibit significant intramolecular charge-transfer characteristics in organic solvents. While inspecting the self-assembly behaviour, the OPV with a long alkyl chain on the central phenyl core (OPV4) underwent gelation in organic solvent mixtures through strong hydrophobic interactions of the long hexadecyl chains and π-interactions from their aromatic counterparts. Computational studies revealed a lamellar packing of molecules in the assembly. Interestingly, the degree of ICT and the gelation abilities of OPVs were significantly influenced by the electronic nature of the substituents appended to the peripheral phenothiazines. Further, the AC impedance results revealed an increase in storage and electronic transport for the fluorescent thin films prepared by an increase in the content of OPV4 in PMMA.

Dicoumarol derivatives: Green synthesis and molecular modelling studies of their anti-LOX activity

Dicoumarol derivatives were synthesized in the InCl3 catalyzed pseudo three-component reactions of 4-hydroxycoumarin with aromatic aldehydes in excellent yields. The reactions were performed in water under microwave irradiation. All synthesized compounds were characterized using NMR, IR, and UV–Vis spectroscopy, as well as with TD-DFT. Obtained dicoumarols were subjected to evaluation of their in vitro lipid peroxidation and soybean lipoxygenase inhibition activities. It was shown that five of ten examined compounds (3e, 3h, 3b, 3d, 3f) possess significant potential of antilipid peroxidation (84–97%), and that compounds 3b, 3e, 3h provided the highest soybean lipoxygenase (LOX-Ib) inhibition (IC50 = 52.5 µM) and 3i somewhat lower activity (IC50 = 55.5 µM). The bioactive conformations of the best LOX-Ib inhibitors were obtained by means of molecular docking and molecular dynamics. It was shown that, within the bioactive conformations interior to LOX-Ib active site, the most active compounds form the pyramidal structure made of two 4-hydroxycoumarin cores and a central phenyl substituent. This form serves as a spatial barrier which prevents LOX-Ib Fe2+/Fe3+ ion activity to generate the coordinative bond with the C13 hydroxyl group of the α-linoleate. It is worth pointing out that the most active compounds 3b, 3e, 3h and 3i can be candidates for further examination of their in vitro and in vivo anti-inflammatory activity and that molecular modeling study results provide possibility to screen bioactive conformations and elucidate the mechanism of dicoumarols anti-LOX activity.

Photochromic DTE-Substituted-1,3-di(2-pyridyl)benzene Platinum(II) Complexes: Photomodulation of Luminescence and Second-Order Nonlinear Optical Properties.

We disclose a new family of photochromic cyclometalated platinum(II) complexes (PtDTE1 and PtDTE2), where a dithienylethene (DTE) unit is connected at the para-position of the central phenyl ring of (N^C^N) cyclometalated ligand, through two different linkages. Their syntheses are presented along with the X-ray characterizations of both the open and closed isomers of PtDTE1. The investigation of their photophysical properties is made, including absorption, photochromism, emission, and second-order nonlinear properties. We report a quantitative photoisomerization for both PtDTE1 and PtDTE2, irrespective of the nature of the connecting mode between the DTE unit and the platinum(II) moiety. The efficient photochromism allows a significant NLO photomodulation, both in solution and in thin films. In addition, we show that the photoluminescence of the PtDTE1 and PtDTE2 can be controlled by the open/closed isomerization of the DTE unit.

A Two-Dimensional Coordination Polymer Based on 1,1':4',1''-Terphenyl-2',4,4'',5'-tetracarboxylate

The coordination polymer, [MnL0.5(H2O)(phen)] n (H4L = 1,1':4',1''-terphenyl-2',4,4'',5'-tetracarboxylic acid, phen = 1,10-phenanthroline), has been solvothermal synthesized and structurally characterized by single-crystal X-ray diffraction. Complex crystallizes in triclinic sp. gr. $$P\bar 1$$ with Z = 2. Two carboxylate oxygen atoms in the central phenyl rings from two μ $${u_{{6^ - }}}$$ L4– ligands doubly-bridge two Mn(II) ions to form the dinuclear $$M{n_2}{({O_{CO{O^ - }}})_2}$$ unit. Each dinuclear $$M{n_2}{({O_{CO{O^ - }}})_2}$$ unit links four L4– ligands and each L4–ligand bridges four dinuclear $$M{n_2}{({O_{CO{O^ - }}})_2}$$ units to generate a 2D coordination network, which can be rationalized as a binodal (4,4) topological network by considering the dinuclear $$M{n_2}{({O_{CO{O^ - }}})_2}$$ units and L4– ligands as 4-connected nodes.

Crystal structure and Hirshfeld surface analysis of a pyridiniminium bromide salt: 1-[2-([1,1'-biphen-yl]-4-yl)-2-oxoeth-yl]-3-methyl-1,4-di-hydro-pyridin-4-iminium bromide.

In the cation of the title salt, C20H19N2O+·Br-, the phenyl rings are inclined to one another by 38.38 (8)°, whereas the central phenyl ring and the pyridiniminium ring are almost perpendicular with a dihedral angle of 87.37 (9)°. The N+=C cationic double bond was verified by the shortened bond length of 1.337 (2) Å. In the crystal, the Br- anion is linked to the cation by an N-H⋯Br hydrogen bond. C-H⋯O hydrogen bonds link adjacent pyridiniminium cations into inversion dimers with an R22(18) graph-set motif. These dimers are stacked in a phen-yl-phenyl T-shaped geometry through C-H⋯π inter-actions. A Hirshfeld surface analysis was conducted to verify the contributions of the different inter-molecular inter-actions.

Amide linkage in novel three-ring bent-core molecular assemblies: polar mesophases and importance of H-bonding

ABSTRACTHere, we report the first examples of achiral unsymmetrical three-ring bent-shaped liquid crystals comprising amide and imine linkages with transverse substituents of methyl and chloro moieties on the central phenyl ring in the core, exhibiting polar banana phases. The extensive intra and inter molecular H-bonding induced novel banana mesomorphic phases. One-dimensional stacking in the mesomorphic phase as well as ferroelectric polar order promoted by intermolecular H-bonding of amide linkage is demonstrated. The compounds exhibit multifunctional properties viz., the enantiotropic liquid crystalline (LC) phase at ambient temperatures, electro-optical response, spontaneous polarisation, emission characteristics with large Stokes shift, and even charge distribution with large voltage holding ratio (VHR) values. The smectic type phase was confirmed by XRD studies and polar order was established by switching current and dielectric investigations. DFT studies revealed the importance of their suitability for display applications.