New metal free organic dyes incorporating heterocyclic Benzofuran core as conjugated spacer: Synthesis,Opto-electrochemical,DFT and DSSC studies

Synthesis of a series of new organic photosensitizers, designated as BZ1 - BZ4 , was achieved by incorporating benzofuran core as π-spacer, triphenylamine (TPA) and 4-methoxy triphenylamine (4-MeO-TPA) as donors and cyanoacrylic acid (CAA) and rhodanine-3-acetic acid (RAA) as acceptor/anchoring groups. Structurally, dyes BZ1 and BZ2 carry TPA and 4-MeO-TPA as donors, respectively, whereas CAA constitutes as a common acceptor. On the other hand, BZ3 and BZ4 incorporate TPA and 4-MeO-TPA as donors, respectively, and RAA serves as a common acceptor. Key steps to access BZ1 - BZ4 involved Wittig olefination, reduction of cyano groups to aldehyde, and finally Knoevenagel condensation. In UV–visible spectra, dyes BZ1 - BZ4 exhibited intramolecular charge transfer (ICT) maxima in the range of 503 nm to 534 nm and their extinction coefficients varied from 22,600 to 40,400 M⁻¹ cm⁻¹. Using cyclic voltammetry and UV–visible data, we calculated the optical band gaps, (E₀₋₀) of BZ1-BZ4 to be 2.09, 2.00, 2.01, and 1.93 eV, respectively. DFT studies revealed that HOMOs of dyes were localized essentially on the donors triphenylamine groups, whereas the LUMOs are largely confined over electron acceptors CAA and RAA as well as partly diffused into the benzofuran spacer. DSSCs, configured using BZ1 - BZ4 as photosensitizers, showed fill factors (ff) in the range of 0.57 to 0.76, comparable to standard N3 dye (0.67). In addition, BZ1 and BZ2 dyes with CAA as an acceptor also exhibited decent open circuit voltage (V_oc) in the range of 0.61 to 0.63 relative to the 0.66 observed for N3 dye. Dyes BZ1-BZ2 carrying CAA as an acceptor exhibited an efficiency (η) of 2.03% and 1.49%, respectively, against the benchmark N3 dye, showing η of 5.02%. Due to poor V_oc and short circuit current density (I_sc), dyes BZ3-BZ4 carrying RAA as acceptor/anchoring group performed significantly poor, showing η of 0.08%, and 0.32%, respectively.     

Novel interference effects and a new quantum phase in mesoscopic systems

Mesoscopic systems have provided an opportunity to study quantum effects beyond the atomic realm. In these systems quantum coherence prevails over the entire sample. We discuss several novel effects related to persistent currents in open systems which do not have analogues in closed systems. Some phenomena arising simultaneously due to two non-classical effects namely, Aharonov-Bohm effect and quantum tunneling are presented. Simple analysis of sharp phase jumps observed in double-slit Aharonov-Bohm experiments is given. Some consequences of parity violation are elaborated. Finally, we briefly describe the dephasing of Aharonov-Bohm oscillations in Aharonov-Bohm ring geometry due to spin-flip scattering in one of the arms. Several experimental manifestations of these phenomena and their applications are given.     

Spectroscopic and docking studies of the binding of two stereoisomeric antioxidant catechins to serum albumins

The interactions of two stereoisomeric antioxidant flavonoids, catechin (C) and epicatechin (EC) with bovine serum albumin (BSA) and human serum albumin (HSA), have been investigated by steady state and time resolved fluorescence, phosphorescence, circular dichroism (CD), FTIR and protein–ligand docking studies. The steady-state fluorescence studies indicate a single binding site for both the ligands. FTIR spectra suggest that in both the albumins, C and EC stabilize the α-helix at the cost of a corresponding loss in the β-sheet structure. CD studies have been carried out using (±)C, and both the epimers (+)C and (?)C. The low temperature phosphorescence and protein–ligand [(+), (?) and (±) forms of C and EC] docking studies indicate that the ligands bind in the proximity of Trp 134 of BSA and Trp 214 of HSA, thereby changing their solvent accessible surface areas (ASA). Asn 158 and Glu 130 side chains are found to be within the hydrogen bonding distance from the phenolic –OH groups of C and EC in the case of BSA complex. C and EC are located within the binding pocket of sub-domain IIa of HSA.     

Catalytic activity of an iron(III) Schiff base complex bound in a polymer resin

An iron(III)–ferrocene complex and its heterogeneous analogue bound in a polymer resin have been prepared and employed as catalysts for the oxidation of various organic substrates. Characterization of the heterogeneous and homogeneous complexes was done by SEM, EDAX, TGA, FT-IR, DRS-UV, and spectroscopy. The catalyst’s activity, stability, and reusability were investigated through industrially relevant oxidation reactions. The solid iron(III)–ferrocene Schiff base complex gave more effective results than the solid-supported ferrocene Schiff base ligand. The antimicrobial activities of the molecular complex and free ligand were studied for Gram-positive and Gram-negative bacteria.     

Ecofriendly Biocomposites from Natural fibers: Mechanical and Weathering study

Increasing environmental concerns and depletion of petroleum resources has forced researchers around the globe to find new green materials. In the present research work, a particular interest was focused on the effective use of lignocellulosic natural fibers as reinforcement using polymer resin as a novel matrix. Green composites were prepared using the compression molding technique with different fiber contents. The physicomechanical and thermal characteristics of the different composite samples were investigated as a function of fiber contents. The results obtained suggest that the properties of the polymer matrix are positively affected by the incorporation of natural cellulosic fibers.     

Manganese(I)‐Catalyzed C−H (2‐Indolyl)methylation: Expedient Access to Diheteroarylmethanes

An unprecedented Mn^I‐catalyzed (2‐indolyl)methylation of heteroarenes is reported. This method makes use of an aromatizing cascade strategy to install a (2‐indolyl)methyl group into target molecules, thereby leading to the expedient synthesis of previously challenging and important unsymmetrical diheteroarylmethanes, in particular bis(2‐indolyl)methanes. The proposed cascade process comprises the reorganization of multiple bonds with controlled regioselectivity and high atom economy and can be performed on a gram‐scale. Furthermore, a metal‐free C?H propargylation is observed. The diverse application of this method is also demonstrated.     

Heteropolymer translocation through nanopores

The authors investigate the translocation dynamics of heteropolymers driven through a nanopore using a constant temperature Langevin thermostat. Specifically, they consider heteropolymers consisting of two types of monomers labeled A and B, which are distinguished by the magnitude of the driving force that they experience inside the pore. From a series of studies on polymers with sequences AmBn the authors identify both universal as well as specific sequence properties of the translocating chains. They find that the scaling of the average translocation time as a function of the chain length N remains unaffected by the heterogeneity, while the residence time of each bead is a strong function of the sequence for short repeat units. They further discover that for a symmetric heteropolymer AnBn of fixed length, the pattern exhibited by the residence times of the individual monomers has striking similarity with a double slit interference pattern where the total number of repeat units N/2n controls the number of interference fringes. These results are relevant for designing nanopore based sequencing techniques.