Synthesis, Optical Spectroscopy, and Laser and Biomedical Imaging Application Potential of 2,4,6-Triphenylpyrylium Tetrachloroferrate and Its Derivatives.

Synthesis, optical spectroscopic properties, two-photon (TP) absorption-induced fluorescence, and laser and bioimaging application potentials of 2,4,6-triphenylpyrylium tetrachloroferrate (1),4-(4-methoxyphenyl)-2,6-diphenylpyrylium tetrachloroferrate (2), 2,6-bis(4-methoxyphenyl)-4-phenylpyrylium tetrachloroferrate (3), and 2,4,6-tris(4-methoxyphenyl)pyrylium tetrachloroferrate (4) are presented. The synthesis involves the conversion of pyrylium tosylates to pyrylium chlorides, followed by transformation into 1-4 on heating to reflux with FeCl3 in acetonitrile. They are characterized using 1H and 13C NMR spectra in CD3OD, and FTIR and Raman spectroscopic techniques. The salts dissolve in organic solvents and water (pH = 7 to 3) even at high concentrations (10-3 M). These solutions absorb light strongly from 500-300 nm. Solutions of 1, 3, and 4 fluoresce with high quantum yield in the 500-700 nm spectral range. Salts 1 and 4 exhibit fluorescence lifetime shortening, line width narrowing, and free-running laser action under intense pulsed laser excitation. Toxicity and cell imaging studies using human cancer cell lines reveal that salts 1 and 3 function as cellular fluorophores in vitro and have no adverse effects on cellular viability at nanomolar ranges. Furthermore, acetonitrile and methanol solutions of salts 1, 3, and 4 exhibit strong two-photon absorption-induced fluorescence, opening potential applications in biomedical imaging and microscopy.

Synthesis and Antimicrobial Activity of (E)-1-Aryl-2-(1H-tetrazol-5-yl)acrylonitrile Derivatives via [3+2] Cycloaddition Reaction Using Reusable Heterogeneous Nanocatalyst under Microwave Irradiation.

The magnetically recoverable heterogeneous Fe2O3@cellulose@Mn nanocomposite was synthesized by a stepwise fabrication of Mn nanoparticles on cellulose-modified magnetic Fe2O3 nanocomposites, and the morphology of the nanocomposite was characterized through advanced spectroscopic techniques. This nanocomposite was investigated as a heterogeneous catalyst for the synthesis of medicinally important tetrazole derivatives through Knoevenagel condensation between aromatic/heteroaromatic aldehyde and malononitrile followed by [3+2] cycloaddition reaction with sodium azide. Thirteen potent (E)-1-aryl-2-(1H-tetrazol-5-yl)acrylonitrile derivatives are reported in this paper with very high yields (up to 98%) and with excellent purity (as crystals) in a very short period (3 min @ 120 W) using microwave irradiation. The present procedure offers several advantages over recent protocols, including minimal catalyst loading, quick reaction time, and the utilization of an eco-friendly solvent. Furthermore, the synthesized (E)-1-aryl-2-(1H-tetrazol-5-yl)acrylonitrile derivatives (4b, 4c, and 4m) are shown to have excellent resistance against various fungal strains over bacterial strains as compared to the standard drugs Cefixime (4 µg/mL) and Fluconazole (2 µg/mL).

Modulating the Conductivity of Light-Responsive Ionic Liquid Crystals.

In this work, we describe the phase behaviour and the dielectric and conductivity response of new light-responsive ionic liquid crystals, ILCs, which can be applied as controllable electrolytes. The materials include two different dicationic viologens, the asymmetric 6BP18 and the symmetric EV2ON(Tf)2, containing bistriflimide as the counterions, mixed with 5% and 50% molar, respectively, of one new photoresponsive mesogen called CNAzO14. These mixtures exhibit liquid crystal behaviour, light responsiveness through the E-Z photoisomerisation of the azobenzene groups in CNAzO14, and strong dielectric responses. The 5%-CNAzO14/Ev2ON(Tf)2 mixture displays direct current conductivities in the 10-7 S·cm-1 range, which can be increased by a two-fold factor upon the irradiation of UV light at 365 nm. Our findings set the grounds for designing new smart ionic soft materials with nanostructures that can be tuned and used for energy conversion and storage applications.

Facile One-Pot Synthesis and Anti-Microbial Activity of Novel 1,4-Dihydropyridine Derivatives in Aqueous Micellar Solution under Microwave Irradiation.

The current study describes a novel and eco-conscious method to synthesize 1,4-dihydropyridine derivatives utilizing an aqueous micellar solution containing aluminum dodecyl sulfate, Al(DS)3, using readily available starting material. The final products were synthesized with excellent yields within remarkably quick reaction durations, promoting remarkable atom economy and minimizing environmental impacts. The present protocol has several advantages over other methodologies in terms of high yield (up to 97%) with excellent purity. Further, the synthesized 1,4-DHPs exhibit favorable to excellent resistance against examined bacterial and fungal species. Intriguingly, polar groups on the phenyl ring (5b, 5c, 5i and 5j) make the 1,4-DHPs equally potent against the microbes as compared to the standard drugs.

Poly(Pyridinium Salt)s Containing 2,7-Diamino-9,9'-Dioctylfluorene Moieties with Various Organic Counterions Exhibiting Both Lyotropic Liquid-Crystalline and Light-Emitting Properties.

A series of poly(pyridinium salt)s-fluorene main-chain ionic polymers with various organic counterions were synthesized by using ring-transmutation polymerization and metathesis reactions. Their chemical structures were characterized by Fourier Transform Infrared (FTIR), proton (1H), and fluorine 19 (19F) nuclear magnetic resonance (NMR) spectrometers. These polymers showed a number-average molecular weight (Mns) between 96.5 and 107.8 kg/mol and polydispersity index (PDI) in the range of 1.12-1.88. They exhibited fully-grown lyotropic phases in polar protic and aprotic solvents at different critical concentrations. Small-angle X-ray scattering for one polymer example indicates lyotropic structure formation for 60-80% solvent fraction. A lyotropic smectic phase contains 10 nm polymer platelets connected by tie molecules. The structure also incorporates a square packing motif within platelets. Thermal properties of polymers were affected by the size of counterions as determined by differential scanning calorimetry and thermogravimetric analysis measurements. Their ultraviolet-visible (UV-Vis) absorption spectra in different organic solvents were essentially identical, indicating that the closely spaced π-π* transitions occurred in their conjugated polymer structures. In contrast, the emission spectra of polymers exhibited a positive solvatochromism on changing the polarity of solvents. They emitted green lights in both polar and nonpolar organic solvents and showed blue light in the film-states, but their λem peaks were dependent on the size of the counterions. They formed aggregates in polar aprotic and protic solvents with the addition of water (v/v, 0-90%), and their λem peaks were blue shifted.

Thermotropic Liquid-Crystalline and Light-Emitting Properties of Bis(4-aalkoxyphenyl) Viologen Bis(triflimide) Salts.

A series of bis(4-alkoxyphenyl) viologen bis(triflimide) salts with alkoxy chains of different lengths were synthesized by the metathesis reaction of respective bis(4-alkoxyphenyl) viologen dichloride salts, which were in turn prepared from the reaction of Zincke salt with the corresponding 4-n-alkoxyanilines, with lithium triflimide in methanol. Their chemical structures were characterized by 1H and 13C nuclear magnetic resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry, polarizing optical microscopy, and variable temperature X-ray diffraction. Salts with short length alkoxy chains had crystal-to-liquid transitions. Salts of intermediate length alkoxy chains showed both crystal-to-smectic A (SmA) transitions, Tms, and SmA-to-isotropic transitions, Tis. Those with longer length of alkoxy chains had relatively low Tms at which they formed the SmA phases that persisted up to the decomposition at high temperatures. As expected, all of them had excellent thermal stabilities in the temperature range of 330-370 °C. Their light-emitting properties in methanol were also included.

Phosphine Oxide Containing Poly(pyridinium salt)s as Fire Retardant Materials.

Six new rugged, high-temperature tolerant phosphine oxide-containing poly(4,4'-(p-phenylene)-bis(2,6-diphenylpyridinium)) polymers P-1, P-2, P-3, P-4, P-5, and P-6 are synthesized, characterized, and evaluated. Synthesis results in high yield and purity, as confirmed by elemental, proton (1H), and carbon 13 (13C) nuclear magnetic resonance (NMR) spectra analyses. High glass transition temperatures (Tg > 230 °C) and high char yields (>50% at 700 °C) are determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. These new ionic polymers exhibit excellent processability, thin-film forming, high-temperature resistance, fire-resistance and retardation, coating, adhesion, mechanical and tensile strength, and n-type (electron transport) properties. The incorporation of phosphine oxide and bis(phenylpyridinium) moieties in the polymer backbones leads to high glass transition temperatures and excellent fire retardant properties, as determined by microcalorimetry measurements. The use of organic counterions allows these ionic polymers to be easily processable from several common organic solvents. A large variety of these polymers can be synthesized by utilizing structural variants of the bispyrylium salt, phosphine oxide containing diamine, and the counterion in a combinatorial fashion. These results make them very attractive for a number of applications, including as coating and structural component materials for automobiles, aircrafts, power and propulsion systems, firefighter garments, printed circuit boards, cabinets and housings for electronic and electrical components, construction materials, mattresses, carpets, upholstery and furniture, and paper-thin coatings for protecting important paper documents.

Thermotropic Liquid-Crystalline and Light-Emitting Properties of Poly(pyridinium) Salts Containing Various Diamine Connectors and Hydrophilic Macrocounterions.

A set of poly(pyridinium) salts containing various diamine moieties, as molecular connectors, and poly(ethyleneglycol)-4-nonylphenyl-3-sulfopropyl ether, thereafter referred to as "Macroion", as the hydrophilic counterion, were prepared by metathesis reaction from the respective precursory tosylated poly(pyridinium)s in methanol. The structure of these ionic polymers was established by spectroscopy and chromatography techniques. The shape-persistent ionic poly(pyridinium) materials, inserting rigid or semi-rigid diamine spacers, display thermotropic liquid-crystalline properties from room-temperature up to their isotropization (in the temperature range around 160-200 °C). The nature of the LC phases is lamellar in both cases as identified by the combination of various complementary experimental techniques including DSC, POM and variable-temperature SAXS. The other polymers, inserting bulky or flexible spacers, only form room temperature viscous liquids. These new macromolecular systems can then be referred to as polymeric ionic liquid crystals (PILCs) and or polymeric ionic liquids (PILs). All the ionic polymers show excellent thermal stability, in the 260-330 °C temperature range as determined by TGA measurements, and a good solubility in common organic solvents as well as in water. Their optical properties were characterized in both solution and solid states by UV-Vis and photoluminescent spectroscopies. They emit blue or green light in both the states and exhibit a positive solvatochromic effect.

Room temperature thermotropic liquid crystalline phases of catanionic surfactants derived from quaternary ammonium surfactants and bis(2-ethylhexyl)sulfosuccinate.

HYPOTHESIS: Properties of catanionic surfactants can be tailored by the choice of appropriate headgroups and hydrocarbon tails. Thermal behavior of catanionic surfactants can be influenced by the length and number of alkyl chains. EXPERIMENTS: A series of eight catanionic surfactants were synthesized from quaternary ammonium surfactants as the cationic counterpart and bis(2-ethylhexyl)sulfosuccinate (AOT) as the anionic counterpart. The thermal properties and the liquid crystalline properties of these catanionic surfactants were studied by the following methods: Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Hot-Stage Polarized Light Microscopy (HSPLM), and X-ray Diffraction (XRD). FINDINGS: The results indicate that transition temperatures, enthalpies of transition, and mesophase structures vary with the length and number of chains attached to the quaternary nitrogen. These compounds exhibit room temperature liquid crystalline (LC) textures that are predominantly "fan-like," as observed by HSPLM, and phases that are hexagonal columnar, as observed by XRD, with the exception of one compound which exists as a nematic liquid crystal at 25°C. Additionally, all of the surfactants also exhibit thermal stability in the range of 256-300°C.

Synthesis of [PtCl2(4,4'-dialkoxy-2,2'-bipyridine)] complexes and their in vitro anticancer properties.

A series of [Pt(II)Cl2(4,4'-dialkoxy-2,2'-bipyridine)] complexes of the general formula of [Pt(II)Cl2(4,4'-bis(RO)-2,2'-bipyridine)] (where R = -(CH2)n-1CH3, n = 2-6, 8) were synthesized and characterized using (1)H NMR, (13)C NMR spectroscopy, elemental analysis, mass spectroscopy, and differential scanning calorimetry measurements. The in vitro anti-proliferative activities of these compounds were evaluated against human cancer cell lines A549 (lung adenocarcinoma), DU145 (prostate carcinoma), MCF-7 (breast adenocarcinoma), and MDA-MB-435 (melanoma) using the MTS cell proliferation assay. Several Pt(II) coordination compounds were found to have greatly enhanced activity compared to cisplatin after a one hour treatment in all cell lines tested. A structure-activity relationship was observed, that is, the activity increases as the carbon chain length of the alkyl group increases. The activity was maximum when the carbon chain length reached four or five carbons and decreased with the longer carbon chain length. Fluorescence microscopy and flow cytometry data indicate that the main mode of cell death is through apoptosis with some necrotic responses.