Thiacalixarene Appended Azo-based Supramolecular Systems: Self-assembly and Photo Tuning Reversible Liquid Crystalline Properties

Four new azo-based supramolecular materials containing thiacalixarene core substituted by variable alkoxy groups ( TFA₁ – TFA₄ ) have been designed and synthesized for the mesomorphic and photoswitching properties. The liquid crystalline behavior were accomplished by using DSC, POM, and XRD studies. All azo-based thiacalixarene based materials with short and higher chain length display columnar hexagonal mesophase with broad temperature range. The thermal behavior of all the materials was investigated by DSC and TGA study. The structural and conformational study of the lower rim functionalized materials was confirmed by using different techniques. These thiacalixarene moulded liquid crystalline compounds shows columnar self-assembly type behavior and higher thermal stability. The introduction of bi-substituted azo-ester network towards the lower rim of thiacalixarene core has impact on the electron delocalization and liquid crystalline properties. The photoswitching properties suggested cis and trans azo-isomerization under radiation of UV light and higher thermal back relaxation time. The mesogenic behaviour of compound TFA₂ and TFA₄ were demolished by the influence of cis and trans isomerization. The structure-property correlation is studied to understand the variation in mesogenic properties with the substitution of variable alkoxy side chain.     

Preparation of open tubular capillary column covalently coated with polystyrene sulfonate with 4,4′-Azobis(4-cyanopentanoyl chloride) as polymerization initiator for electrochromatographic separation of alkaloids,sulfonamides, and peptides

An open tubular capillary electrochromatography column covalently bonded with polystyrene sulfonate was prepared via in situ polymerization using functionalized Azo-initiator 4,4′-Azobis(4-cyanopentanoyl chloride). Scanning electron, fluorescence, and atomic force microscopy techniques showed the formation of a relatively rough layer of polymer. In addition, –CN and C = O stretching vibrations from infrared spectroscopy proved the successful immobilization of the azo-initiator through covalent bonding and X-ray photoelectron spectroscopy confirmed the elemental composition of the formed polymer layer. The prepared column was found to be appropriate for small and medium-sized molecules separation. Compared to bare fused silica capillary column higher selectivity and resolution were obtained for the separation of alkaloids, sulfonamides, and peptides as a result of the electrostatic and pi-pi stacking interactions between the small organic molecules and the coated column without compromising the electroosmotic flow mobility. Separation efficiency was also increased compared to the bare capillary for the separation of alkaloids (about 1.5 times). Moreover, intraday, inter-day, intra-batch, and inter-batch relative standard deviation values of retention time and peak area of peptides were within 2% and 10%, respectively, indicating good repeatability of the column preparation procedure. The developed method for the covalent bonding of polymers through a functionalized azo-initiator could represent a promising stable method for the preparation of an open tubular column.     

Mesomorphism of azo-esters and chalcone-esters

One chalcone-ester homologous series of mesogens α-4-[4^/-n-alkoxybenzoyloxy phenyl β-4^//methoxy benzoyl ethylenes (A) and one azo-ester homologous series of mesogens p-(p^/-n-alkoxybenzoyloxy) phenyl azo-p^//-methoxy benzene (B) being structurally similar are discussed. Both series (A) and (B) differ in respect of central bridges linking two phenyl rings. Mesomorphic properties start from 6th and 1st member of series (A) and (B) respectively. In series (A), 6th to 12th members show both smectogenic and nematogenic properties, and the 14th and 16th members show only nematogenic property. While in series (B), 1st to 10th members show nematogenic properties, 11th member shows both smectogenic and nematogenic properties, while 12th member shows only smectogenic property. Thermal stability of series (A) is relatively high as compared to series (B). Transition temperatures are observed through hot stage polarizing microscope by the miscibility method. Analytical data support the structure of molecules. Textures of series (A) in nematic are threaded and Schlieren in SmecticSmectic A type, while that of series (B) in nematic are threaded in SmecticSmectic A and smectic C.     

Azopyrazolobenzylidene derivatives of 4‐amino‐1,2,4‐triazol‐3‐ones. Synthesis of 4‐{[4‐(3,5‐dimethyl‐1H‐pyrazol‐4‐yl)diazenyl]‐benzylidene}amino‐2‐aryl‐5‐methyl‐3H‐[1,2,4]‐triazol‐3‐ones

The Schiff bases 3a‐h obtained from 4‐amino‐1,2,4‐triazol‐3‐ones 1a‐h when subjected to Japp‐Klingemann reaction yielded the corresponding 3‐{2‐[(2‐aryl‐5‐methyl‐3H‐[1,2,4]‐triazol‐3‐one‐4‐yl)]‐iminophenyl}‐pentane‐2,4‐diones 4a‐h . These diones on cyclisation with N₂H₄ yielded the title compounds 5a‐h . The energetics of the Keto‐enol tautomers of the diones was calculated by semiemperical calculations using AM1 and PM3 methods. All these compounds were screened for their antimicrobial activity against few microbes and most of them exhibited fungal inhibition more than the reference drugs used.     

Accumulation and Toxicity of Nanoplastics in Photosynthetic-Species

This plastic waste degrades into nanoparticles, which are referred to as nanoplastics (NPs) pollutants, due to faulty reuse and recycling processes. These micro and nano plastic pollutants have the ability to absorb and interact with common pollutants and have a high surface area to volume ratio, which causes serious effects on the environment, especially plants. The size of pollutants is so small that they can cross the biological barriers and affect the cellular and molecular levels. Exposure to nanoplastics in photosynthetic species affects the growth and photosynthesis mechanism of the plants. Nanoplastics also affect humans through intake of the exposed plant materials. These pollutants can be plastic pellets, personal care products, marine coatings, synthetic textiles, etc. Plastic pollutants may enter the human body mainly through contaminated food and water. This review incorporates the toxicity of such pollutant and how their remediation is being done. The focus is also on the advancement of detection and remediation techniques.     

Synthesis of Naked-eye Detectable Fluorescent 2<Emphasis Type="Italic">H-</Emphasis>chromen-2-One 2, 6-Dicyanoanilines: Effect of Substituents and pH on Its Luminous Behavior

A variety of new coumarin derivatives containing C-4 bridged 2,6-dicyanoanilines (4a-4d) were synthesized via multicomponent one pot approach. These novel sensors were characterized by spectral analysis and a series of pH sensing fluorescence studies were performed, the results indicating that the sensors are highly selective and more effective at various pH. The fluorescence colour changes at different pH could be directly detected by naked eyes.     

Extrinsic multiecho phase-contrast SSFP: evaluation on cardiac output measurements

Multiecho phase-contrast steady-state free precession (PC-SSFP) is a recently introduced sequence for flow quantification. In this multiecho approach, a phase reference and a velocity-encoded readout were acquired at different echo times after a single excitation. In this study, the sequence is validated in vitro for stationary flow. Subsequently, the sequence was evaluated on cardiac output measurements in vivo for through-plane flow in comparison to regular single gradient echo velocity quantification [phase-contrast spoiled gradient echo (PC-GE)]. In vitro results agreed with regular flow meters (RMS 0.1 cm/s). Cardiac output measurements with multiecho PC-SSFP on 10 healthy subjects gave on average the same results as the standard PC-GE. However, the limits of repeatability of PC-SSFP were significantly larger than those of PC-GE (2 l/min and 0.5 l/min, respectively, P=.001). The multiecho approach introduced some specific problems in vivo. The difference in echo times made the velocity maps sensitive for water-fat shifts and B(0)-drifts, which in turn made velocity offset correction problematic. Also, the addition of a single bipolar gradient cancelled the flow compensated nature of the SSFP sequence. In combination with the prolonged TR, this resulted in flow artifacts caused by high and pulsatile through-plane flow, affecting repeatability. Given the significantly lower repeatability of PC-SSFP, cardiac output in turn is less reliable, thus impairing the use of multiecho PC-SSFP.     

Mesomorphic properties of liquid crystalline compounds with chalconyl central linkage in two phenyl rings

In order to investigate the influence of the central linking group and the effect of flexibility on mesomorphism, we have synthesised a newly homologous series 3-(3-butoxyphenyl)-1-(4-n-alkoxy phenyl) prop-2-en-1-one (series-l) consisting of 13 homologues C₁–C₈, C₁₀, C₁₂, C₁₄, C₁₆ and C₁₈. In the present series, mesophase commences from the C₆ homologue. C₁–C₅ homologues did not exhibit liquid crystalline (LC) property, while C₆–C₁₂ homologues exhibited an enantiotropic nematic phase and the rest of the homologues C₁₄–C₁₈ displayed monotropic SmC and nematic mesophase. The transition temperatures of the synthesised compounds were determined by an optical polarising microscopy equipped with a heating stage. All newly synthesised compounds were confirmed by ¹H-NMR, ¹³C-NMR, IR and elemental analysis.