Self‐assembly of Renewable Nano‐sized Triterpenoids

Studies on plant metabolites have gained renewed interest in recent years because these can serve as renewable chemicals for the development of a sustainable society. Among various plant secondary metabolites, terpenoids constitute the major component and triterpenoids are the 30C subset of it. In recent years, triterpenoids have drawn the attention of scientific community due to many of its potential and realized applications in medicine, drug delivery, thermochromic materials, pollutant capture, catalysis, liquid crystals, etc. In this personal review, we have discussed our computational results carried out on sixty representative naturally occurring triterpenoids demonstrating that all the triterpenoids are renewable functional nano‐entities. Study of the self‐assembly of several triterpenoids such as betulin, betulinic acid, oleanolic acid, glycyrrhetinic acid and arjunolic acid and their derivatives in different liquids have also been discussed. Moreover, the utilization of the resulting supramolecular architectures such as vesicles, spheres, flowers and fibrillar networks of nano‐ to micrometer dimensions and gels have also been discussed in the perspective of green, renewable and nanos.     

Colored multiplicative and additive non-Gaussian noise-driven dynamical system: Mean first passage time

We have studied the barrier crossing dynamics in presence of non-Gaussian noises. It has been observed that multiplicative colored non-Gaussian noise can induce resonant activation (RA). The conspicuous dependence of mean first passage time (MFPT) on correlation time (_τ2${\tau }_2$) of additive colored noise having fixed variance have been analyzed. Beyond a critical value of _τ2${\tau }_2$ the MFPT increases for a given rate of increase of noise strength with _τ2${\tau }_2$ if the additive colored noise is non-Gaussian. The MFPT first decreases with increase of the non-Gaussian parameter (measures deviation from Gaussian character) of multiplicative colored noise followed by an increase exhibiting a minimum. The appearance of the minimum critically depends on the additive noise.     

Selectivity in Garratt-Braverman cyclization: an experimental and computational study

Bispropargyl sulfones equipped with aromatic rings of dissimilar nature were synthesized. Under basic conditions, these sulfones isomerized to the bisallenic sulfones, creating a competitive scenario between two alternate Garratt-Braverman (GB) cyclization pathways. The observed product distribution ruled out the involvement of any ionic intermediate and supported the diradical mechanism with greater involvement of the electron-rich aromatic ring via the more nucleophilic radical. DFT-based calculations supported the diradical mechanism along with the observed selectivity.     

Colored non-gaussian noise driven open systems: generalization of Kramers' theory with a unified approach

In this paper we have calculated escape rate from a meta stable state in the presence of both colored internal thermal and external nonthermal noises. For the internal noise we have considered usual gaussian distribution but the external noise may be gaussian or non-gaussian in characteristic. The calculated rate is valid for low noise strength of non-gaussian noise such that an effective gaussian approximation of non-gaussian noise wherein the higher order even cumulants of order "4" and higher are neglected. The rate expression we derived here reduces to the known results of the literature, as well as for purely external noise driven activated rate process. The latter exhibits how the rate changes if one switches from non-gaussian to gaussian character of the external noise.     

Click-reagent version of Sonogashira coupling protocol to conjugated fluorescent alkynes with no or reduced homocoupling

A click-reagent version of the Sonogashira-coupling protocol has been developed. Diarylalkynes with donor and/or acceptor substituents have been synthesized via this protocol at moderate to excellent yields and with no or drastically reduced quantities of undesired homocoupled side products. This protocol is green-solvent compatible, air-insensitive, and effective under microwave conditions.     

Barrier crossing dynamics of a charged particle in the presence of a magnetic field: a new turnover phenomenon

In this paper we have investigated the effect of a magnetic field on the barrier crossing rate of a charged particle. At the low friction regime we have observed a new turnover phenomenon for the variation of rate as a function of field strength. Thus although the force due to the magnetic field is not dissipative in nature, it plays a role in the steady state barrier crossing rate similar to that of a dissipative force in the weak damping regime. For appreciable damping strength, the rate monotonically decreases with the increase of field strength. We have demonstrated an interesting resonance effect due to the variation of frequency of the harmonic oscillator associated with the y-component motion at low damping and magnetic field strength.     

Water induced chromogenic and fluorogenic signal modulation in a bi-fluorophore appended acyclic amino-receptor system

An acyclic amino-receptor based bi-fluorophoric signaling system 3 exhibits water-induced simultaneous dual channel chromogenic and fluorogenic signal modulation. Its micromolar solution in various organic solvents exhibits an enhancement in absorption in the presence of water in trace amounts through the water-induced delactonization of rhodamine dye, rendering a visual perception as a function of colour change. The presence of water molecules also facilitates a fluorescence resonance energy transfer (FRET) from the excited nitro-benz-oxa-diazole fluorophore to rhodamine dye of 3 and leads to an enhancement of emission up to a second order of magnitude. The failure of the reference compounds 2 and 4 to respond under similar conditions reveals the role of structural variation of the receptor on the perturbation of photophysical processes.     

Alteration of selectivity in rhodamine based probes for Fe(III) and Hg(II) ion induced dual mode signalling responses

The probes for metal ion induced chromo- and fluorogenic signalling responses alter their selectivity depending upon the nature of substituent as well as a function of solvent medium. 2 has shown selectivity towards Fe(III) ion, 4 towards Hg(II) ion while 3 is responsive towards both Fe(III) and Hg(II) ions.     

Exact scalar field cosmologies in a higher derivative theory

We obtain exact cosmological solutions of a higher derivative theory described by the Lagrangian L=R+2αR ² in the presence of interacting scalar field. The interacting scalar field potential required for a known evolution of the FRW universe in the framework of the theory is obtained using a technique different from the usual approach to solve the Einstein field equations. We follow here a technique to determine potential similar to that used by Ellis and Madsen in Einstein gravity. Some new and interesting potentials are noted in the presence of R ² term in the Einstein action for the known behaviours of the universe. These potentials in general do not obey the slow rollover approximation.     

Turn on Fluorescence Sensing of Zn2+ Based on Fused Isoindole-Imidazole Scaffold

Optical chemosensors caused a revolution in the field of sensing due to their high specificity, sensitivity, and fast detection features. Imidazole derivatives have offered promising features in the literature as they bear suitable donor/acceptor groups for the selective analytes in the skeleton. In this work, an isoindole-imidazole containing a Schiff base chemosensor (1-{3-[(2-Diethylamino-ethylimino)-methyl]-2-hydroxy-5-methyl-phenyl}-2H-imidazo[5,1-a]isoindole-3,5-dione) was designed and synthesized. The complete sensing phenomena have been investigated by means of UV-Vis, fluorescence, lifetime measurement, FT-IR, NMR and ESI-MS spectroscopic techniques. The optical properties of the synthesized ligand were investigated in 3:7 HEPES buffer:DMSO medium and found to be highly selective and sensitive toward Zn²⁺ ion through a fluorescence turn-on response with detection limit of 0.073 μm. Furthermore, this response is effective in gel form also. The competition studies reveal that the response of the probe for Zn²⁺ ion is unaffected by other relevant metal ions. The stoichiometric binding study was performed utilizing Job’s method which indicated a 1:1 sensor–Zn²⁺ ensemble. Computational calculations were performed to pinpoint the mechanism of sensing.