Unprecedented formation of benzo[d][1,2,3,6]oxatriazocine derivatives via diazo-oxygen bond formation and synthesis of enantiomerically pure 1-alkyl benzotriazole derivatives

A series of amino acid-derived enantiomerically pure substituted benzo[d][1,2,3,6]oxatriazocine derivatives and 1-alkyl substituted benzotriazoles has been prepared by the diazotization of amino acid-derived benzo-fused alicycles. The first unprecedented diazo-oxygen bond formation in acidic medium led to an entirely new kind of substituted benzo[d][1,2,3,6]oxatriazocine heterocycles.     

Immobilization of bio-macromolecules on self-assembled monolayers: methods and sensor applications

Attachment of biomolecules on gold, silicon or glass surfaces has direct implications for the development of novel biosensors in the context of nanoscale detection of pathogens and other metabolites related to issues of human health. In this critical review, we have highlighted the current developments in various techniques of immobilization of biomolecules, specifically biological macromolecules on surfaces through the modification of a functional self-assembled monolayer. The utility of such immobilized biomolecules in the area of biosensing in nanoscale has been surveyed. Merits and demerits of some of the methods with reference to sensitivity of detection and practical use have been discussed (221 references).     

Coordination-driven self-assembly of 2D-metallamacrocycles using a shape-selective Pt(II)2-organometallic 90° acceptor: design, synthesis and sensing study

Synthesis of a series of two-dimensional metallamacrocycles via coordination-driven self-assembly of a shape-selective Pt(II)(2)-molecular building unit incorporating carbazole-ethynyl functionality is described. An equimolar (1?:?1) combination of a Pt(II)(2)-organometallic 90° acceptor, 1, with rigid linear ditopic donors (L(a) and L(b)) afforded [4 + 4] self-assembled octanuclear molecular squares, 2 and 3, in quantitative yields, respectively [L(a) = 4,4'-bipyridine; L(b) = trans-1,2-bis(4-pyridyl)ethylene]. Conversely, a similar treatment of 1 with an amide-based unsymmetrical flexible ditopic donor, L(c), resulted in the formation of a [2 + 2] self-sorted molecular rhomboid (4a) as a single product [L(c) = N-(4-pyridyl)isonicotinamide]. Despite the possibility of several linkage isomeric macrocycles (rhomboid, triangle and square) due to the different connectivity of L(c), the formation of a single and symmetrical molecular rhomboid (4a) as the only product is an interesting observation. All the self-assembled macrocycles (2, 3 and 4a) were fully characterized by multinuclear NMR ((1)H and (31)P) and ESI-MS analysis. Further structural insights about the size and shape of the macrocycles were obtained through energy minimization using density functional theory (DFT) calculations. Decoration of the starting carbazole building unit with Pt-ethynyl functionality enriches the assemblies to be more π-electron rich and luminescent in nature. Macrocycles 2 and 3 could sense the presence of electron deficient nitroaromatics in solution by quenching of the initial intensity upon gradual addition of picric acid (PA). They exhibited the largest quenching response with high selectivity for nitroaromatics compared to several other electron deficient aromatics tested.     

MRDCI study of the low-lying electronic states of PbSi

Electronic states of the PbSi molecule up to 4 eV have been studied by carrying out ab initio based MRDCI calculations which include relativistic effective core potentials (RECPs) of both the atoms. The use of semicore RECPs of Pb produces better dissociation limits than the full-core one. However, the (3)P(0)-(3)P(1) splitting due to Pb is underestimated by about 4000 cm(-1). At least 25 bound electronic states of the Λ-S symmetry are predicted for PbSi. The computed zero-field-splitting in the ground state is about 544 cm(-1). A strong spin-orbit mixing changes the nature of the potential energy curves of many Ω states. The overall splitting among the spin components of A(3)Π is computed to be 4067 cm(-1). However, the largest spin-orbit splitting is reported for the (3)Δ state. A number of spin-allowed and spin-forbidden transitions are predicted. The partial radiative lifetime for the A(3)Π-X(3)Σ(-) transition is of the order of milliseconds. The computed bond energy in the ground state is 1.68 eV, considering the spin-orbit coupling. The vertical ionization energy for the ionization to the X(4)Σ(-) ground state of PbSi(+) is about 6.93 eV computed at the same level of calculations.     

Acid-responsive microcapsules: the loading-unloading processes

A simple and convenient method to prepare acid-responsive microcapsules by using functionalized single-walled carbon nanotubes and ytterbium triflate has been developed. Fluorescence active compounds were "pre-loaded" or "post-loaded" in the microcapsules and released later in acidic medium. An interesting "zip-unzip" phenomenon was observed while filming the action of acid on microcapsules under a microscope.     

Multiplex cancer cell detection by SERS nanotags with cyanine and triphenylmethine Raman reporters

SERS nanotags have been prepared to accomplish the multiplex detection of cancer cells. Herein we evaluated the adequacy of lipoic acid-containing cyanine derivatives (Cy3LA and Cy5LA) to function as multiplex partners with a triphenylmethine Raman reporter (B2LA) under a single excitation wavelength. SERS experiments enabled the multiplex recognition of two different cancer cells with antibody-conjugated nanotags that were derivatized with optimized cyanine and triphenylmethine reporters.     

Ratiometric fluorescence signalling of fluoride ions by an amidophthalimide derivative

Fluorescence behaviour of 4-benzoylamido-N-methylphthalimide (1), designed and developed for selective detection of fluoride ions, is reported. 1 displays F⁻-induced colour change that allows its detection with the naked eye. The F⁻ specificity of the sensor system is evident from the fact that unlike F⁻, other halides do not affect the absorption characteristics of 1. Apart from the colorimetric response, the fluorescence output of 1 is also modulated by F⁻ in a manner that permits ratiometric fluorescence signalling of F⁻ as well. It is found that the system can detect F⁻ in the concentration range of 10–60 μM. The results of the experiments and theoretical calculations unambiguously suggest that the changes of the electronic absorption and fluorescence behaviour of 1, which have been exploited for signalling purpose, are due to F⁻-induced deprotonation of the 4-amido moiety of the sensor system.     

New Reagent for Detection of Amino Acids on TLC Plates

JPC – Journal of Planar Chromatography – Modern TLC -     

Post-scission dynamics in fission

A dynamical model for fission from the classical turning point to scission and beyond is presented. We consider the fissioning nucleus as well as the fission fragments as incompressible irrotational deformable charged liquid drops. We focus on the post-scission time evolution of the neck, stretching of the fragments, kinetic energy and excitation energy.     

Photoionization and photoelectron angular distribution for H2

Photoionization of H₂(¹Σ_g⁺) in a vibrational υ″ and rotational N″ state into H₂⁺(²Σ_g⁺) in a vibrational υ′ and rotational N′ state is studied theoretically. The differential cross section, after summing over the final states, is expressed in the well-known simple form of $\text{(}\text{σ}{}_{\mathrm{T}}\text{4π}\text{)[1 + βP}{}_2\text{(}\text{cos}\text{θ)]}$. Parallel expressions are obtained for H₂⁺ in a specific υ′ state (in terms of σ(υ′) and β(υ′)) and for H₂⁺ in a rotational fine level υ′N′ (in terms of σ(υ′N′) and β(υ′N′)). Asymmetry parameters β, β(υ′) and β υ′N′), which are expressed in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, can be reduced approximately to 2 lineary polarized light and to -1 for unpolarized light. Using single-center electronic wave functions and including partial eaves l = 1, 3, and 5, σ(υ′) and β(υ′) are computed as a function of υ′ at 584 Å. The computed σ(υ′) divided by the Frank-Condon overlap, in agreement with experimental results, increases monotonically with υ′; σ_T and β are computed in the incident photon energy range of 600–4000 Å and the results compare favorably with previous calculations.