Nucleophilic addition of CN- ion to -C=N bond of aza-BODIPY leading to turn-on fluorescence sensor

We report for the first time that 1,3,5,7-tetraaryl aza-BODIPYs can be used as an exclusive chemodosimetric, colorimetric and turn-on fluorescence sensor for CN- ion. We demonstrated that CN- ion attacks the -C=N bond of aza-BODIPY core via nucleophilic addition reaction and the resultant compound show significant alteration in electronic properties because of disruption of conjugation as verified by spectral and electrochemical studies. Specially, the aza-BODIPY which exhibit moderate fluorescence in NIR region changes to fluorescent compound which emits strongly in the visible region and thus the 1,3,5,7-tetraaryl aza-BODIPY can be used as turn-on fluorescence sensor for CN- ion. We also used 2-formy1-1,3,5,7-tetraaryl aza-BODIPY which has both -C=N and -CHO active sites for nucleophilic attack by CN- ion and showed that CN- ion prefer -C=N over -CHO as demonstrated here. (C) 2015 Elsevier B.V. All rights reserved

Synthesis of Dicyanovinyl Substituted E-Diphenyldipyrroethene and its Selective Application for Cyanide Sensing

We report the synthesis of two E dicyanovinyl substituted 1,2 ditolyl dipyrroethenes over a sequence of steps and characterized by mass, NMR, and X-ray crystallography. The crystal structure reveals that the E-dicyanovinyl substituted 1,2-ditolyl dipyrroethene is significantly distorted and shows propeller shaped structure. The pyrrole protected E-dicyanovinyl sub-stituted 1,2-ditolyl dipyrroethene is strongly fluorescent compared to unprotected one. The anion sensing studies indicated that the pyrrole protected E-dicyanovinyl substituted 1,2-ditolyl dipyrroethene is selective colorimetric,chemodosimetric turnoff fluorescence sensor for CN- ion as confirmed by absorption, fluorescence and NMR studies

meso-Salicylaldehyde substituted BODIPY as a chemodosimetric sensor for cyanide anions

The meso-salicylaldehyde substituted BODIPY was synthesized over a sequence of steps and characterized by X-ray crystallography, mass, NMR, absorption, fluorescence and electrochemical techniques. The crystal structure showed the presence of strong intramolecular hydrogen bonding between hydroxyl and formyl groups, which induces rigidity in the BODIPY core and makes the BODIPY relatively more fluorescent than the meso-phenyl BODIPY. Our studies showed that the meso-salicylaldehyde BODIPY can be used as a specific chemidosimetric sensor for CN- ions. The presence of a hydroxyl group adjacent to a formyl group helps in activating the formyl group for a nucleophilic attack. Upon addition of the CN- ion to the meso-salicylaldehyde BODIPY, the CN- ion attacks the formyl group and converts it to the cyanohydrin group. This irreversible reaction was monitored by following the changes in absorption, fluorescence and electrochemical properties and the results support the view that the meso-salicylaldehyde substituted BODIPY can be used as a specific chemodosimetric sensor for CN- ions. To substantiate the role of the hydroxyl group, we also prepared the meso(m-formylphenyl) BODIPY which contains only the formyl group on meso-phenyl, and our studies indicated that the meso(m-formylphenyl) BODIPY cannot be used as a chemodosimetric sensor for CN- ions, as verified by absorption and emission studies

Sn-IV Porphyrin Scaffolds for Axially Bonded Multiporphyrin Arrays: Synthesis and Structure Elucidation by NMR Studies

A simple, one-step, supramolecular strategy was adopted to synthesize Sn-IV-porphyrin-based axially bonded triads and higher oligomers by using meso-pyridyl Sn-IV porphyrin, meso-hydroxyphenyl-21,23-dithiaporphyrin, and Ru-II porphyrin as building blocks and employing complementary and non-interfering (SnO)-O-IV and (RuN)-N-II interactions. The multiporphyrin arrays are stable and robust and were purified by column chromatography. H-1, H-1-H-1 COSY and NOESY NMR spectroscopic studies were used to unequivocally deduce the molecular structures of Sn-IV-porphyrin-based triads and higher oligomers. Absorption and electrochemical studies indicated weak interaction among the different porphyrin units in triads and higher oligomers, in support of the supramolecular nature of the arrays. Steady-state fluorescence studies on triads indicated the possibility of energy transfer in the singlet state from the basal Sn-IV porphyrin to the axial 21,23-dithiaporphyrin. However, the higher oligomers were weakly fluorescent due to the presence of heavy Ru-II porphyrin unit(s), which quench the fluorescence of the Sn-IV porphyrin and 21,23-dithiaporphyrin units

Parametric Investigation and optimization of Near-Dry Electrical Discharge Machining

508-511This study investigates near-dry Electric Discharge Machining (EDM) in order to achieve higher Material Removal Rate (MRR), lower Tool Wear Rate (TWR) and Better surface finish than conventional EDM on High Speed Steel (HSS) workpiece. Taguchi L27 orthogonal array was used for conducting experimentation. The experiments have been conducted by mixing of limited quantities of water with high pressure air (air-mist). This paper presents a relatively simple device to be used for applying the near-dry EDM. The near-dry EDM does not produce toxic fumes so called Environment friendly machining process for the applied operating conditions, the near-dry electrical discharge machining presents some advantages regarding the machined surface quality and the electrode tool wear, in comparison with the machining that uses liquid dielectric. The effect of different process parameters like applied current, duty factor, gap control, sensitivity, tool lift was analyzed on MRR, surface finish and tool wear rate