Helicenoid-based bis-1,2,3-triazole tweezer: Synthesis and selective iodide sensing

Abstract

Novel helicenoid based 1,2,3-triazole tweezer 4 was synthesized using a multistep synthetic protocol with high yields from 2,7-Dihydroxynaphtlene 3 as a precursor. This helicenoid-based bis-1,2,3-triazole tweezer 4 selectively causes non-covalent interaction with iodide anion. The UV-vis absorption exhibited enhancement while fluorescence spectra exhibited significant quenching. ¹H NMR titration showed shift of 1,2,3-triazole C-H signal with an increase in iodide concentration. Association constant of 3.818?×?10⁴ M^?1 was recorded for the host interaction with iodide ions. This value of association constant for iodide sensing using 1,2,3-triazole is the best reported so far for hosts with 1,2,3-triazole moiety and suggests that the helicenoid geometry is responsible for this remarkable behavior.     

Facile Synthesis of Pyrazoline Derivatized Amides via Sydnone Ring Cleavage

In the present investigation, we have utilized 3‐[3′‐(5″‐aryl‐2″‐pyrazolin‐3″‐yl)]phenylsydnones 1a–c to couple two biodynamic moieties in amide derivatives 7 , 8 , 9 , 10 . The compounds 1a–c were brominated to 4‐bromo‐3‐[3′‐(5″‐aryl‐2″‐pyrazolin‐3″‐yl)]phenylsydnone 2 , which were further reacted with secondary amines to form the title compounds. These novel molecules were subjected to antitubercular activity against Mycobacterium tuberculae (H₃₇R_v) and antioxidant activity assay.     

Antimicrobial and DNA Cleavage Studies of New N2O2 Diazadioxa Macrocyclic Schiff Base Co(II), Ni(II) and Cu(II) Complexes Containing Triazole Head Unit: Synthesis and Spectroscopic Approach

A novel series of N₂O₂ diazadioxa macrocyclic complexes [MLCl₂] (M=Co²⁺, Ni²⁺ and Cu²⁺) have been synthesized with newly derived biologically active ligands (L^I-L^IV). These ligands were synthesized by the condensation of 1, 6-bis(2-formylphenyl)hexane and 3-subtituted-4-amino-5-hydrazino-1, 2, 4-triazole. The mode of bonding and overall geometry of the complexes have been inferred through IR, EPR, electronic spectral studies, conductivity, magnetic, thermal and electrochemical studies. All the complexes are soluble in DMF and DMSO and are non-electrolytes. All these complexes have been screened for their antibacterial (Escherichia coli, Staphylococus aureus, Salmonella typhi, Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and Cladosporium) by the MIC method. The DNA cleavage study was done by Agarose gel electrophoresis.     

Relative performances of effective medium formulations in interpreting specific composite thin films optical properties

Several powerful effective medium formulations/approximation (EMA) and associated theories with different origins and concepts have been discussed and utilized here in order to model the experimental refractive index evolutions of ZrO₂-SiO₂ and Gd₂O₃-SiO₂ composite films with respect to their compositional mixings. Amongst these formulations, the Böttcher's generalized theory has been noticed to have more versatility and can simulate varieties of experimental observations incorporating a form factor parameter to account for the grain structure and morphology to a great extent. The refractive index modeling results of most of the available theories were compared with respect to their functional evolutions and limitations. It was noticed that at higher silica fractions (>20%) in our composite films, the effective experimental refractive index parameters have remained close to the most modeling results and Böttcher's expression has shown to fit the observable parameters very accurately. However, under low silica compositions (<20%) the refractive index values of the composite films depicted different functional evolutions. Such deviations have been attributed to the various morphological, grain structure and band gap supremacies observed in these specific composite films which are not accounted by the effective medium formulations and approximations. These observations are well supported by the atomic force microscopy results.     

Mode-to-mode energy transfers in convective patterns

We investigate the energy transfer between various Fourier modes in a low-dimensional model for thermal convection. We have used the formalism of mode-to-mode energy transfer rate in our calculation. The evolution equations derived using this scheme is the same as those derived using the hydrodynamical equations for thermal convection in Boussinesq fluids. Numerical and analytical studies of this model show that convective rolls appear as the Rayleigh number R is raised above its critical value R _c. Further increase of Rayleigh number generates rolls in the perpendicular directions as well, and we obtain a dynamic asymmetric square pattern. This pattern is due to Hopf bifurcation. There are two sets of limit cycles corresponding to the two competing asymmetric square patterns. When the Rayleigh number is increased further, the limit cycles become unstable simultaneously, and chaotic motion sets in. The onset of chaos is via intermittent route. The trajectories wander for quite a long time almost periodically before jumping irregularly to one of the two ghost limit cycles.     

Development of an reliable analytical method for synergistic extractive spectrophotometric determination of cobalt(II) from alloys and nano composite samples by using chromogenic chelating ligand

A synergistic simple and selective spectrophotometric method was developed for the determination of cobalt(II) with 1-(2',4'-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2',4'-dinitro APTPT] as a chromogenic reagent. The proposed method has been described on the basis of synergistic effective extraction of cobalt(II) in presence of pyridine at pH range 9.5-10.2, showed orange-red coloured ternary complex having molar ratio 1:2:2 (M:L:Py). The equilibrium time is 10 min for extraction of cobalt(III) from organic phase. The absorbance of coloured organic layer in chloroform is measured spectrophotometrically at 490 nm against reagent blank. The Beer's law was obeyed in the concentration range 2.5-15 μg mL(-1) of cobalt(II) and optimum concentration range was 5-12.5 μg mL(-1) of cobalt(II) and it was evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT-pyridine complex in chloroform are 1.109×10(3) L mol(-1) cm(-1) and 0.053 μg cm(-2), respectively while molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT complex in chloroform are 6.22×10(2) L mol(-1) cm(-1) and 0.096 μg cm(-2), respectively. The composition of cobalt(II)-2',4'-dinitro APTPT-pyridine complex (1:2:2) was established by slope ratio method, mole ratio method and Job's method of continuous variation. The ternary complex was stable for more than 48 h. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The method is successfully applied for the determination of cobalt(II) in binary, synthetic mixtures and real samples. A repetition of the method was checked by finding relative standard deviation (R.S.D.) for n=5 which was 0.15%. The reliability of the method is confirmed by comparison of experimental results with atomic absorption spectrophotometer.     

Production of camptothecin by hairy roots and regenerated transformed shoots of Ophiorrhiza rugosa var. decumbens

Camptothecin (CPT), the derivatives of which are used clinically for the treatment of metastatic colon cancer, is isolated from intact plants that can be subjected to environmental fluctuations. In?vitro cultures may be an alternate and continuous source for year-round production of CPT. Since CPT production by undifferentiated cell cultures is low, differentiated tissues such as root cultures may be a viable alternate source for CPT production. Hairy roots were induced in Ophiorriza rugosa, a source of CPT, using Agrobacterium rhizogenes strain LBA9402. The hairy roots, when cultured in light, showed spontaneous regeneration of shoots. Analysis of CPT levels in the hairy roots and in?vitro-grown transformed shoots revealed 0.009% d.w. and 0.012% d.w., respectively.     

Facile TICl<Subscript>4</Subscript>-catalyzed synthesis of novel 1,2,4-triazoles appended to thiazoles

The reaction of sydnone-derived 3-aryl-5-methyl-1,3,4-oxadiazol-2(3H)-ones with thiourea and α-bromoacetophenone derivatives in the presence of a catalytic amount of TiCl₄ produces 2-aryl-4-(4-aryl-1,3-thiazol-2-yl)-5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-ones. The title compounds were screened for their antibacterial and antifungal activity. The toxicity of the compounds was evaluated in terms of mutagenicity, tumorigenicity, and reproductive effects. The drug-relevant properties (ClogP, drug-likeness, and drug score) were calculated, and the structure–activity relationship was discussed.     

Diels–Alder Reaction of 2‐Ethenyl‐1,3,3‐trimethylcyclohexene with 4H‐Chromen‐4‐ones: A Convergent Approach to ABCD Tetracyclic Core of Marine Diterpenoids Related to Puupehenone and Kampanols

A rapid assembly of the tetracyclic core of marine diterpenoids related to puupehenone and kampanols by Diels? Alder reaction of 2‐ethenyl‐1,3,3‐trimethylcyclohexene with 4H‐chromen‐4‐one (=4H‐1‐benzopyran‐4‐one) dienophiles is described.     

Facile Knoevenagel and Domino Knoevenagel/Michael Reactions Using Gel‐Entrapped Base Catalysts

An efficient method for Knoevenagel condensation of arenecarbaldehydes with active methylene compounds such as barbituric acid and Meldrum's acid in the presence of gel‐entrapped base catalysts is reported. The method has been extended to the one‐pot synthesis of arylmethylene‐bis[3‐hydroxycyclohex‐2‐en‐1‐one] derivatives from dimedone (=5,5‐dimethylcyclohexane‐1,3‐dione) and arenecarbaldehydes by using domino Knoevenagel/Michael reaction sequence.