Highly Substituted Acephenanthrylenes and Their π-Extended Derivatives: Syntheses, Structural Analyses, and Properties.

This investigation demonstrates that a series of (highly) substituted acephenanthrylenes (APs) 2, benzo[l]acephenanthrylene 3, and dicyclopenta[cd,mn]pyrene 4 are easily prepared by palladium-catalyzed cycloaromatization of 2,3-diethynylbiphenyls 1. The first nonpyrolysis synthesis of 4 by two-fold cycloaromatization was achieved in a high yield. This synthetic protocol has two crucial advantages: facile introduction of various substituents and efficient extension of the AP backbone.

Metal-Ion-Induced Mechanical Chirality: Achiral Rotaxane as the Only Ligand in Chiral Palladium(II)-N-Heterocyclic Carbene Complexes.

We report the insertion of Pd(II) into an originally achiral rotaxane producing two chiral metallorotaxanes: one is planar-chiral, with its two interlocked components both chelating nonequivalently to the metal center; the other is C2-symmetrical-chiral, with the dynamically exchangeable stereogenic units stabilized by the interlocked structure. Chiral additives confirmed the existence of chirality, with the enantiomers of the C2-symmetrical N-heterocyclic carbene complex being resolved using chiral TRISPHAT counteranions.

Evaluation of RevX solution extract as a potential inhibitor of the main protease of SARS-CoV-2-In vitro study and molecular docking.

The main protease (Mpro) of SARS-CoV-2 is a protease necessary for viral polyprotein processing and maturation. Mpro cleaves the polypeptide sequence after the glutamine residues. There is no known cellular protease with this substrate specificity in humans; therefore, it is considered an attractive drug target. Previously, fermented sorghum extract RevX (trademark of Revolutrx INC.) solution significantly alleviated physical decline and complications in a patient with lung adenocarcinoma, suggesting the role of bioactive components in RevX solution. To further explore whether the bioactive components in RevX solution exhibit other biological activities, such as antiviral effects, we investigated its inhibitory effect on the Mpro of SARS-CoV-2 virus. We report herein that the solid extract of the RevX solution exhibits an efficacious Mpro inhibitory activity, with IC50 of 2.07 ± 0.38 µg/mL. Molecular docking of sterol-like components in the RevX extracts identified by MS shows that the three sterol-like molecules can bind to the active region of the GC376-Mpro complex, supporting the structure-function relationship. Combined with its ability to significantly alleviate the body's immunity decline and to inhibit the activity of SARS-CoV-2 Mpro, RevX solution may provide a possible alternative supportive treatment for patients with COVID-19.

Converting non-Mesogenic to Mesogenic Stacking of Amino-s-Triazine-Based Dendrons with p-CN Phenyl Unit by Eliminating Peripheral Dipole.

Three new amino-s-triazine-based dendrons, 1a, 1b, and 1c, containing an aryl-CN moiety in the dendritic skeleton were prepared in 72-81% yields (1a: R1 = - N(n-C8H17)2, R2 = n-OC8H17, 1b: R1 = R2 = - N(n-C8H17)2, 1c: R1 = - N(n-C8H17)2, R2 = - N(n-C4H9)2). Dendrons 1a with N(n-C8H17)2 and n-OC8H17 peripheral substituents, surprisingly, did not show any mesogenic phase during the thermal process. However, non-mesogenic 1a can be converted to mesogenic 1b or 1c by eliminating the peripheral dipole arising from the alkoxy substituent; dendron 1b only comprising the same N(n-C8H17)2 peripheral groups showed a ~25 °C mesogenic range on heating and ~108 °C mesogenic range on cooling. In contrast, dendron 1c possessing different N(n-CmH2m+1)2 (m = 8 versus m = 4) peripheral units, having similar stacking as 1b, exhibited a columnar phase on thermal treatment, but its mesogenic range (~9 and ~66 °C on heating and cooling, respectively) was much narrower than that of 1b, attributed to 1c's less flexible alkyl chains in the peripheral part of dendron. Dendron 1a with the alkoxy substituent in the peripheral skeleton, creating additional dipole correspondingly, thus, leads to the dendritic molecules having a non-mesogenic stacking. Without the peripheral dipole for intermolecular side-by-side interaction, dendrons 1b and 1c exhibit a columnar phase on thermal treatment because of the vibration from the peripheral alkyl chain.

Adsorbing Volatile Organic Chemicals by Soluble Triazine-Based Dendrimers under Ambient Conditions with the Adsorption Capacity of Pyridine up to 946.2 mg/g.

Two triazine-based dendrimers with peripheral 1,3,5-triamidobenzene (1-3-5-TAB) functionality were prepared, and their void spaces in the bulk solid were investigated. We examined dendrimers of three core lengths and determined the one with the longest core exhibits the largest void space because the peripheral amides were not imbedded in the internal space of each dendritic molecule. The new dendrimers as solids were observed to adsorb volatile organic chemicals efficiently. Importantly, because the dendrimers are soluble in organic solvents, the adsorbed VOCs can be quantified by 1H-NMR spectroscopy by choosing a chemical shift (δ) of dendrimers as the internal standard to exclude interfering impurity signals, a much simpler and more efficient protocol than the traditional GC technique for the VOC quantification. One dendrimer was found to adsorb 24 equivalents of pyridine, so its adsorption capacity is equivalent to 946.2 mg/g. This is a more than 2-fold increase than the reported values by other porous materials.

Unconventional Approaches to Prepare Triazine-Based Liquid Crystal Dendrimers.

Most triazine-based liquid crystalline (LC) dendrimers reported thus far are the main-chain LC macromolecules with long flexible chains at their periphery and attached to internal rigid or semi-rigid frameworks. Their formation of mesogenic phases often depends on the intermolecular face-to-face π-π interactions between dendritic molecules, which are unusual. Their mesogenic phases can also be formed by incorporation of mesogenic units to the dendritic skeletons through long flexible chains, as most side-chain LC dendrimers, in which the peripheral mesogenic units generally play the important roles. For main-chain triazine-based dendrimers, their morphology is maintained by restricted freedom of rigid or semi-rigid connecting units, and their formations of LC phases are therefore not straightforward to be controlled. In this review, we thus describe modulating of the intermolecular face-to-face π-π interactions between the triazine-based dendritic molecules, with the aim of forming LC phases through molecular design.

Electric-Field-Induced Chirality in Columnar Liquid Crystals.

We describe a novel class of tetraphenylbenzene-based discotic molecules with exceptional self-assembling properties. Absorption and fluorescence studies confirmed the formation of J-type aggregates in solution. The discotic mesogens also show an enhancement of the emission upon aggregation. Interestingly, these discotic molecules displayed enantiotropic hexagonal columnar liquid crystal (LC) phases that can be switched into a helical columnar organization by application of an electric field. The helical columns arise from the electric-field-induced tilt of the polar fluorobenzene ring that directs all of the peripheral phenyl groups into a propeller-like conformation with respect to the central benzene core. A cooperative assembly process of these propeller-shaped molecules resolves into a helical columnar organization, in which the preferred helical sense is obtained from the stereogenic center proximate to the polar carbon-fluorine bond. The ease of inducing chirality in columnar LCs by an electric field presents opportunities to create next-generation chiral materials for a variety of applications.

Versatile Pt(II) Pyrazolate Complexes: Emission Tuning via Interplay of Chelate Designs and Stacking Assemblies.

Three homoleptic Pt(II) metal complexes [Pt(imPz)2] (1), [Pt(imiz)2] (2), and [Pt(imMz)2] (3) were synthesized from the treatment of Pt(DMSO)2Cl2 and functional imidazolyl pyrazole in refluxing tetrahydrofuran (THF). Alternatively, the heteroleptic Pt(II) complexes [Pt(imPz)(fppz)] (4), [Pt(imiz)(fppz)] (5), and [Pt(imMz)(fppz)] (6) were obtained from the treatment of a common intermediate [Pt(fppzH)Cl2] with a corresponding imidazolyl chelate. Pt(II) complexes 1, 2, and 5 were studied by single-crystal X-ray diffraction to reveal the corresponding packing arrangement in their crystal lattices, among which both homoleptic complexes 1 and 2 formed monomeric species, while heteroleptic 5 aligned as a dimer with a nonbonding Pt···Pt contact of 3.574 Å. Subsequent photophysical examinations showed that the homoleptic 1-3 and heteroleptic 4-6 exhibited the structured sky-blue ππ* emission and structureless light-green-emitting metal-metal-to-ligand charge transfer (MMLCT) emission in the solid state, respectively. A shortened Pt···Pt interaction of approximately 0.34-0.35 nm was confirmed in thin films of all heteroleptic Pt(II) complexes 4-6 by grazing-incidence X-ray diffraction (GIXD) analyses. Finally, Pt(II) complex 6 was employed as a dopant in the fabrication of organic light-emitting diode (OLED) devices with varied doping ratios, among which OLEDs with only 1 wt % 6 in the SimCP host exhibited a maximum external quantum efficiency (EQE) of 5.8% and CIEx,y values of 0.20, 0.31. In contrast, OLEDs using a nondoped architecture (i.e., 100% of 6 in the emitting layer (EML)) achieved a maximum EQE of 26.8%, current efficiency (CE) of 91.7 cd A-1, and power efficiency (PE) of 80.1 lm·W-1 and CIEx,y values of 0.41, 0.55, manifesting their versatility in various degrees of stacking assemblies and hence facile color-tuning capability on OLEDs.

Probe exciplex structure of highly efficient thermally activated delayed fluorescence organic light emitting diodes.

The lack of structural information impeded the access of efficient luminescence for the exciplex type thermally activated delayed fluorescence (TADF). We report here the pump-probe Step-Scan Fourier transform infrared spectra of exciplex composed of a carbazole-based electron donor (CN-Cz2) and 1,3,5-triazine-based electron acceptor (PO-T2T) codeposited as the solid film that gives intermolecular charge transfer (CT), TADF, and record-high exciplex type cyan organic light emitting diodes (external quantum efficiency: 16%). The transient infrared spectral assignment to the CT state is unambiguous due to its distinction from the local excited state of either the donor or the acceptor chromophore. Importantly, a broad absorption band centered at ~2060 cm-1 was observed and assigned to a polaron-pair absorption. Time-resolved kinetics lead us to conclude that CT excited states relax to a ground-state intermediate with a time constant of ~3 µs, followed by a structural relaxation to the original CN-Cz2:PO-T2T configuration within ~14 µs.

3D and 2D supramolecular assemblies and thermotropic behaviour of a carbo-benzenic mesogen.

Hexaalkoxy-di(phenylethynyl)-tetraphenyl-carbo-benzenes bearing six CnH2n+1 aliphatic chains (n = 12, 18) have been synthesized and characterized, including by single crystal XRD analysis. For n = 12, a liquid crystal behaviour was observed in the range of 109-130 °C. DSC, POM and PXRD analyses evidenced a rectangular columnar mesophase at 115 °C. The determined 3D lattice constants are consistent with 2D STM images of the so-called "carbo-mesogen" deposited on an HOPG surface.

Converting Nonliquid Crystals into Liquid Crystals by N-Methylation in the Central Linker of Triazine-Based Dendrimers.

Two triazine-based dendrimers were successfully prepared in 60-75% yields. These newly prepared dendrimers 2a and 2b containing the -NMe(CH2)2NMe- and the -NMe(CH2)4NMe- linkers between two G3 dendrons, respectively, exhibit columnar phases during the thermal process. However, the corresponding dendrimers 1a and 1b containing the -NH(CH2)2NH- and the -NH(CH2)4NH- linkers between two G3 dendrons, respectively, do not show any LC phases on thermal treatment. Computational investigations on molecular conformations reveal that N-methylation of the dendritic central linker leads dendrimers to possess more isomeric conformations and thus successfully converts non-LC dendrimers (1a and 1b) into LC dendrimers (2a and 2b).

Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase.

Examples of polynuclear metallomesogens are few. Herein,1,2,4-triazole ligands were used to prepare mono- and polynuclear silver(I) triazole metallomesogens. Besides showing an SmA phase in the mesophase, two interesting properties were observed. First, higher ion conductivity is always found for the polynuclear complexes than for the mononuclear complexes with the same anion, an observation contrary to the knowledge that migration of a monomeric cation should be faster than that of a polymeric cation. Second, thermolysis of the polynuclear silver(I) triazole complexes in the assembled mesophase yielded Ag nanowires, in an excellent demonstration of the assembled nature of the polynuclear silver(I) ions in the thermolysis process.

An Unconventional Approach to Induce Liquid-Crystalline Phases of Triazine-Based Dendrons by Breaking Their Self-Assembly into Dimers.

Three triazine-based dendrons (1 a-c) were successfully prepared in 70-83 % yields. These newly prepared dendrons are found to be liquid crystalline (LC). Computational investigations on molecular conformations and dipoles of triazine-based dendrons reveal that the substituent on the central triazine unit interrupts strong dipole or H-bond interactions to avoid dimeric formation. The obtained dendrons, not favouring self-assembly into dimers but showing LC behaviours, provides evidence for an approach contrary to the conventional method of inducing LC behaviours of dendrons by dimer or trimer formation, mostly through H-bond interactions.

Regioselective synthesis of tetraphenyl-1,3-butadienes with aggregation-induced emission.

In the presence of substoichiometric amounts of Co2(CO)8, internal bisarylalkynes undergo reductive dimerization with good to excellent yields. The Co2(CO)8-induced reactions described are experimentally quite simple and provide a very useful synthetic procedure for the synthesis of tetraphenylbutadienes which exhibit aggregation-induced emission enhancement, i.e., weak emission in good solvents but strong fluorescence in solvents that lead toward formation of aggregates or in the solid state.

Biaxial aromatics with face-on/edge-on stacking adaptability: an STM/STS study of 1D nanowires assembled via rotatable ethynyls.

Scanning tunnelling microscopy/spectroscopy reveals significant electronic communications between edge-on biphenyl moieties of a benzene core derivatised biaxially with four ethynyl-biphenyls. The key to the successful assembly of conjugated 1D nanowires is the rotatable features of ethynyls, which allow dual adaptability of edge-on and face-on orientations for the aromatic rings.

A small change in central linker has a profound effect in inducing columnar phases of triazine-based unconventional dendrimers.

Four unconventional triazine-based dendrimers have been prepared and characterized by (1) H and (13) C NMR spectroscopies, mass spectrometry, and elemental analysis. Based on DSC studies, polarizing microscopy, and powder XRD, two of these dendrimers, containing linkers with an odd number of carbon atoms, were observed to display columnar liquid-crystalline phases during thermal treatment. However, the other two dendritic analogues, containing linkers with an even number of carbon atoms, were not observed to behave correspondingly. Based on computer simulation, we reasonably assume that the dendrimers with an odd number of carbon atoms in their linkers distort their molecular shape and adopt two isomeric structures due to asymmetrical congestion. This reduces the molecular π-π face-to-face interaction, which in turn causes the dendrimers to form columnar LC phases during thermal treatment. However, the dendrimers with an even number of carbon atoms in their linkers have more symmetrical skeletons and do not display any liquid-crystalline phase upon thermal treatment. This new strategy should be applicable for eliciting the columnar liquid-crystalline properties of other types of unconventional dendrimers with rigid frameworks.

Facile catch and release of fullerenes using a photoresponsive molecular tube.

A novel M2L2 molecular tube capable of binding fullerene C60 was synthesized from bispyridine ligands with embedded anthracene panels and Ag(I) hinges. Unlike previous molecular cages and capsules, this open-ended tubular host can accommodate a single molecule of various C60 derivatives with large substituents. The fullerene guest can then be released by using the ideal, noninvasive external stimulus, light.

Electrical pulse triggered reversible assembly of molecular adlayers.

Reversible adlattice assembly for alkoxy-decorated aromatics is controllable by short electrical pulses.

Induction of the columnar phase of unconventional dendrimers by breaking the C2 symmetry of molecules.

Two triazine-based unconventional dendrimers were prepared and characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD studies showed that these dendrimers display columnar liquid-crystalline phases during thermal treatment. This is ascribable to breaking of their C(2) symmetry. The molecular conformations of prepared dendrimers were obtained by computer simulation with the MM3 model of the CaChe program in the gas phase. The simulation showed that the conformations of the prepared dendrimers are rather flat and disfavor formation of the LC phase. However, due to C(2)-symmetry breaking, the prepared dendrimers have structural isomers in the solid state and thus show the desired columnar phases. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks.

Enantiotropic nematics from cross-like 1,2,4,5-tetrakis(4'-alkyl-4-ethynylbiphenyl)benzenes and their biaxiality studies.

The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations.