An efficient 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU)-mediated synthesis of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides

A series of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides 4 has been effectively achieved in high yield and purity from the reaction of pyrazole carboxylic acid 2 with amines 3 in the presence of TBTU as a catalyst and diisopropyl ethylamine as a base in acetonitrile at room temperature.     

Synthesis and spectral characterization of chloro-organotin(IV) complexes of S-donor ligand: Crystal structure of chloro-t-dibutyltin[4-methyl-1-piperidine]thiocarboxylate

New chloromono- and diorganotin(IV) complexes of 4-methyl-1-piperidine dithiocarboxylic acid have been synthesized in anhydrous chloroform. The complexes were characterized by microanalysis, IR, ¹H and ¹³C NMR, mass spectrometry and XRD. The FTIR spectra clearly demonstrate that organotin(IV) moieties react with [S,S] atoms of the ligand. Compound (1) and (3) exhibits the 5-coordinated while the compound (2) exhibit 6-coordinated geometry in solid state. Compound (3) shows distorted trigonal bipyramidal geometry which is confirmed by X-ray single-crystal diffraction.     

Immobilized dimeric chiral Mn(III) salen complex on short channel ordered mesoporous silica as an effective catalyst for the epoxidation of non-functionalized alkenes

Chiral dimeric Mn(III) salen complex with 1R, 2R-(?)-diaminocyclohexane collar was immobilized on short channel large pore sized silica through a long linker of {(CH₂)₃–NH–melamine–piperazine} to investigate its performance in enantioselective epoxidation of chromenes, indene, styrene and cis β-methyl styrene in the presence of pyridine N-oxide (PyNO) as an axial base using aqueous NaOCl as an oxidant at 0 °C. The immobilized catalyst system showed high turnover frequency (TOF) and enantioselectivity for the smaller and bulkier alkenes like styrene, indene, 2,2-dimethylchromene and 6-cyano-2,2-dimethylchromene (ee up to 98%). These results are the best reported for heterogeneous catalyst under biphasic reaction conditions and were comparable to the dimeric Mn(III) salen system under homogeneous condition. The performance of the immobilized catalyst was retained for six reuse experiments. This protocol was extended to the synthesis of an antihypertensive drug (S)-Levchromakalim (ee 98%) at 1 g level.     

Design and development of an optical beam splitter assembly and high precision colinearity measurements of laser beams

Laser beams with extremely high colinearity are often required where precision position monitoring is important. In order to achieve the said objective, a special type of Laser Beam Splitter Assembly (BSA) has been designed and fabricated in a very small volume due to space constraints. The main features and details of such a system are described here. This type of beam splitter assembly coupled with a diode laser through fibers can be remotely used for alignment or position monitoring of different medium to large size structures with a reconstruction accuracy of 10 μm. In this way, BSA generates two counter propagating laser beams from a single diode laser coupled to an optical fiber. In the present work, the colinearity between two beams within 1 mrad with the variation of 50 μrad has been achieved. The laser's power in the two arms may be controlled precisely, which is an important feature of this BSA. The BSA has been tested to work over a temperature range between ?20 °C to +40 °C. It has also been exposed to 1.0 MeV neutrons at a flux of ～5.0×10¹⁰ n/cm²/s and found compatible.     

Synthesis and studies of covalently linked meso-furyl boron-dipyrromethene-ferrocene conjugates

Four meso-furyl BODIPY-ferrocene conjugates 1–4 in which one or more ferrocene groups were connected directly to BODIPY core or meso-furyl group were synthesized by coupling of appropriate bromo meso-furyl BODIPYs with α-ethynylferrocene under mild Pd(0) coupling conditions. The compounds were characterized by HR-MS mass, NMR, absorption, electrochemistry and fluorescence techniques. The absorption studies of compounds 1–4 showed charge transfer band in addition to BODIPY absorption bands indicating that the BODIPY and ferrocene moieties interact within the conjugates. On the other hand, the charge transfer band is absent in meso-phenyl BODIPY-ferrocene conjugate due to the orthogonal arrangement of ferrocene appended meso-phenyl group with BODIPY core which prevents the interaction between the two moieties. The electrochemical studies showed strong oxidation due to ferrocene moiety and reduction due to meso-furyl BODIPY unit. The compounds 3 and 4 which contain two and three ferrocenyl groups respectively were oxidized at the same potential with two and three electrons involved in the redox process. The compounds 1–4 are weakly fluorescent due to electron transfer from ferrocene unit to BODIPY unit. However, the fluorescence can be restored by oxidizing the ferrocene to ferrocenium ion which prevents the electron transfer between the two moieties. The computational studies support the experimental results.     

The role of C-H and C-C stretching modes in the intrinsic non-radiative decay of triplet states in a Pt-containing conjugated phenylene ethynylene

The intrinsic non-radiative decay (internal conversion) from the triplet excited state in phosphorescent dyes can be described by a multi-phonon emission process. Since non-radiative decay of triplet excitons can be a significant process in organic light-emitting diodes, a detailed understanding of this decay mechanism is important if the overall device efficiency is to be controlled. We compare a deuterated Pt(II)-containing phenylene ethynylene with its non-deuterated counterpart in order to investigate which phonon modes control to the non-radiative decay path. We observe that deuteration does not decrease the non-radiative decay rate. A Franck-Condon analysis of the phosphorescence spectra shows that the electronic excitation is coupled strongly to the breathing mode of the phenyl ring and the C≡C carbon stretching modes, while high-energy C-H or C-D stretching modes play an insignificant role. We, therefore, associate the internal conversion process with the carbon-carbon stretching vibrations.     

Determination of tryptophan in raw materials, rat brain and human plasma by RP-HPLC technique

This paper describes tryptophan (TRP) estimation in raw human plasma and rat brain by reversed-phase high-performance liquid chromatography (RP-HPLC). Estimation was carried out on a Purospher STAR C18 column using water-acetonitrile (90:10 v/v, at pH 2.7) mixture at a rate of 1.5 mL/min as mobile phase. Eluents were monitored at 273 nm by an ultraviolet detector. The method was linear (R(2) > 0.999), precise (intra-day and inter-day precision <2%) in the range of 0.25-20 μg/mL. The detection and quantification limits were 0.0144 μg/mL and 0.0437 μg/mL, respectively. In human plasma, Day 1 and Day 2 precision were 0.054-2.29% and 1.66-3.7%; whereas precisions in rat brain were 1.23-2.3% and 0.677-4.2%, respectively. The method was applied to study TRP level in human smokers and in arthritic rat brain. An efficient RP-HPLC method was developed for TRP determination that worked for clinical and research purposes.     

Shape-directing role of cetyltrimethylammonium bromide in the preparation of silver nanoparticles

We report a simple chemical reduction method for the synthesis of different colored silver nanoparticles, AgNP, using tyrosine as a reducing agent. Effects of cetyltrimethylammonium bromide, CTAB, and tyrosine concentrations are analyzed by UV-visible measurements and scanning electron microscopy (SEM) to evaluate the mode of AgNP aggregation. The position and shape of the surface resonance plasmon absorption bands strongly depend on the reaction conditions, i.e., [CTAB], [tyrosine], and reaction time. Sub-, post-, and dilution-micellar effects are accountable for the fast and slow nucleation and growth processes. Spectrophotometric measurement also shows that the average size and the polydispersity of AgNP increase with [CTAB] in the solution. CTAB acted as a shape-directing agent.     

Synthesis and In Vitro Antibacterial Activity of Novel Steroidal (6R)‐Spiro‐1,3,4‐thiadiazoline Derivatives

Novel steroidal (6R)‐spiro‐1,3,4‐thiadiazoline derivatives were synthesized by the cyclization of steroidal thiosemicarbazones with acetic anhydride, screened in vitro against antibacterial activity using disc‐diffusion method and the minimum inhibitory concentration. The results showed that steroidal thiadiazoline derivatives exhibited better antibacterial activity than the steroidal thiosemicarbazone derivatives. Chloro and acetoxy substituents on the 3β‐position of the steroidal thiadiazoline ring increased the antibacterial activity. Among all the compounds, compound 7 and 8 were found better inhibitors of both types of bacteria (Gram‐positive and Gram‐negative) as compared to the respective drug amoxicillin. All the synthesized compounds were well characterized by spectroscopic methods such as IR, ¹H‐NMR, ¹³C‐NMR mass, and elemental analysis and their stereochemistry was also discussed.