Synthesis, structures, and photophysical properties of π-expanded oligothiophene 8-mers and their Saturn-like C60 complexes.

Two isomers of a multifunctional π-expanded macrocyclic oligothiophene 8-mer, E,E-1 and Z,Z-1, were synthesized using a McMurry coupling of a dialdehyde composed of four 2,5-thienylene and three ethynylene units under high dilution conditions. On the other hand, cyclo[8](2,5-thienylene-ethynylene) 2 was synthesized by intramolecular Sonogashira cyclization of ethynyl bromide 5. From STM measurements, both E,E-1 and Z,Z-1 formed self-assembled monolayers at the solid-liquid interface to produce porous networks, and from X-ray analyses of E,E-1 and 2, both compounds had a round shape with a honeycomb stacked structure. E,E-1 formed various fibrous polymorphs due to nanophase separation of the macrorings. E,E-1 and Z,Z-1 in solution exhibited photochromism upon irradiation with visible and UV light, respectively, and this photoisomerization was confirmed by using STM. Furthermore, amorphous films of Z,Z-1 and E,E-1 showed photoisomerization, although single crystals, fibers, and square tubes of E,E-1 remained unchanged under similar conditions. E,E-1 with a 12.5-14.7 Å inner cavity incorporated fullerene C60 in the cavity in solution and the solid state to produce a Saturn-like complex, whose structure was determined by X-ray analysis. 2 also formed a Saturn-like complex with C60 in the solid state. These Saturn-like complexes are stabilized by van der Waals interactions between the sulfur atoms of 8-mer and C60. The complexes exhibited charge-transfer interactions in the solid state. Like E,E-1, Saturn-like complex E,E-1⊃C60 formed small cube and fiber structures depending on the solvent used, whereas those of Saturn-like complex 2⊃C60 were limited due to the rigidity of the macroring of 2.

Free radical scavenging, antidiarrheal and anthelmintic activity of Pistia stratiotes L. extracts and its phytochemical analysis.

In this phyto-pharmacological screening of Pistia stratiotes L leaf and root extracts each separately in two different solvents demonstrated its potential medicinal value. Apparent antioxidant value is demonstrated by DPPH, Nitric oxide scavenging and Ferric ion reducing method. Additionally, total flavonoid and phenolic compounds were measured. The leaf methanolic extract scavenged both nitric oxide (NO) and DPPH radical with a dose dependent manner. But the pet ether fraction of root was found to have highest efficacy in Fe(3±) reducing power assay. Flavonoid was found to contain highest in the pet ether fraction of root (411.35mg/g) in terms of quercetin equivalent, similarly highest amount (34.96mg/g) of total phenolic compounds (assayed as gallic acid equivalents) were found to contain in the same fraction. The methanolic fractions appeared less cytotoxic compared to pet ether extracts. The plant extracts caused a dose dependent decrease in faecal droppings in both castor oil and magnesium sulphate induced diarrhea, where as leaf extracts in each solvent appeared most effective. Also, the plant extracts showed anthelmintic activity in earthworm by inducing paralysis and death in a dose dependent manner. At highest doses (50 mg/ml) all fractions were almost effective as the positive control piperazine citrate (10 mg/ml). Thus, besides this cytotoxic effect it's traditional claim for therapeutic use can never be overlooked.

Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds.

In the present work, a theoretical study was carried out to study the molecular structure, harmonic vibrational frequencies, normal force field calculations, and Raman scattering activities for fluorene π-conjugation spacer containing azo-based dye named trans- and cis-bis(9H-fluoren-2-yl)diazene (AzoFL) at density functional theory using B3LYP (Becke-3-Lee-Yang-Parr) functional and 6-31+G(d,p) basis set. The theoretical calculations have also been performed with fluorene and the trans- and cis-isomers of diazene, difluorodiazene by the same method DFT-B3LYP/6-31+G(d,p) and basis set. The present DFT calculation shows that the trans-AzoFL is more stable than the cis-AzoFL by 16.33 kcal/mol. We also report the results of new assignments of vibrational frequencies obtained on the basis of the present calculations. Time-dependent DFT (TD-DFT) and ZIndo calculations have been performed to study the UV-vis absorption behavior and frontier molecular orbitals for the above-mentioned compounds. The UV-vis spectrum from TD-DFT calculation shows the π-π* transition bands at λmax 423.53 nm (εmax 6.0 × 104 M-1 cm-1) and at λmax 359.45 nm (εmax 1.7 × 104 M-1 cm-1), respectively, for trans- and cis-AzoFL. Compared to parent trans-diazene (λmax 178.97 nm), a significant variation to longer wavelength (∼245 nm) is observed due to the incorporation of the fluorene (FL) ring into the -N=N- backbone. The co-planarity of the two FL rings with the longer N=N bond length compared to the unsubstituted parent diazene indicates the effective red shift due to the extended π-conjugation in trans-AzoFL. The nonplanarity of cis-AzoFL (48.1° tilted about the C-N bond relative to the planar N=N-C bond) reflects its ∼64 nm blue shift compared to that of trans-counterpart.