Photochemical Synthesis of 7,12-Dioxa[8]helicene and Density Functional Theory Studies: Unravelling the One-Way Valve System Involving Steric Crowding and Aromatic Stability.

symmetric chiral 7,12-dioxa[8]helicenes were synthesized through a series of photochemical - isomerization, electrocyclic reaction, and oxidation steps in a stepwise sequential manner at both the ends of 2,9-di(()-styryl)naphtho[2,1-b:7,8-b']difuran. The chemical transformations complemented with density functional theory (DFT) studies delineate some fundamental concepts, exhibiting counter current effects, namely, destabilization caused by increasing steric crowding and stabilization caused by aromatic units on the overall transformation. The calculated energy profile diagram unravels the formation of photoinduced intermediate species with increasing free energies for the - isomerization and the electrocyclic reactions; the reverse processes for the said steps are prevented by a specific barrier-less oxidation step forming aromatic rings, presenting a one-way valve situation.

Dehydrative Substitution Reaction in Water for the Preparation of Unsymmetrically Substituted Triarylmethanes: Synthesis, Aggregation-Enhanced Emission, and Mechanofluorochromism.

Water as a reaction media in chemical transformations has several advantages in terms of safety and non-toxicity. However, dehydrative substitution reaction in water is a highly challenging operation. In this paper, we have reported a sulfamic acid-mediated dehydrative substitution reaction of benzofuryl alcohols with several nucleophiles in water towards the scalable, easily isolable, synthesis of unsymmetrically substituted triarylmethanes (TRAMs) in good to excellent yields (up to 92 %).

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas Advancement in Molecular Diagnostics and Signal Readout Approaches.

Discovery of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system has greatly improved the gene editing technology. Their applications in the area of diagnostic innovation are gaining much attention. The key characteristics of CRISPR/Cas system that allowed its extensive exploitation in the detection platform are their programmable and highly selective target recognition scheme.

Design and Development of Axially Chiral Bis(naphthofuran) Luminogens as Fluorescent Probes for Cell Imaging.

Designing chiral AIEgens without aggregation-induced emission (AIE)-active molecules externally tagged to the chiral scaffold remains a long-standing challenge for the scientific community. The inherent aggregation-caused quenching phenomenon associated with the axially chiral (R)-[1,1'-binaphthalene]-2,2'-diol ((R)-BINOL) scaffold, together with its marginal Stokes shift, limits its application as a chiral AIE-active material. Here, in our effort to design chiral luminogens, we have developed a design strategy in which 2-substituted furans, when appropriately fused with the BINOL scaffold, will generate solid-state emissive materials with high thermal and photostability as well as colour-tunable properties.

Cyclic Organoselenide BODIPY-Based Probe: Targeting Superoxide in MCF-7 Cancer Cells.

All aerobic cells contain reactive oxygen species (ROSs) in balance with biochemical antioxidants. Oxidative stress is developed when this balance gets disturbed because of excessive production of ROSs or depletion of antioxidants. Here, in this work, we have developed the first cyclic diselenide BODIPY-based (organoselenium-containing) probe for the selective detection of superoxide.

Synthesis of Concave and Vaulted 2-Pyran-Fused BINOLs and Corresponding [5] and [7]-Oxa-helicenoids: Regioselective Cascade-Concerted Route and DFT Studies.

Synthesis of concave and vaulted 2-pyran-fused BINOLs has been achieved. A regioselective, path-breaking concerted cascade route allows the placement of six-membered heteroaromatic rings at the sterically crowded 7,8 and 7',8' positions of BINOL. DFT studies with relative energetics that support the kinetically controlled reaction pathway are preferred, matching the experimental results.

Benzyne-Mediated Nonconcerted Pathway toward Synthesis of Sterically Crowded [5]- and [7]Oxahelicenoids, Stereochemical and Theoretical Studies, and Optical Resolution of Helicenoids.

Synthesis of [5]- and [7]oxahelicenoids via Diels-Alder reaction of sterically crowded bichromenes with benzyne is presented. Studies carried out on Diels-Alder addition product establish the unusual preference for a stepwise mechanism over the concerted reaction pathway. This high yielding general synthetic protocol affords unexpected anti cycloadducts [5]- and [7]oxahelicenoids, as confirmed by crystallographic analysis.

Mass spectrometric and charge density studies of organometallic clusters photoionized by gigawatt laser pulses.

Clusters on exposure to nanosecond laser pulses of gigawatt intensity exhibit a variety of photo-chemical processes such as fragmentation, intracluster reaction, ionization, Coulomb explosion, etc. Present article summarizes the experimental results obtained in our laboratory utilizing time-of-flight mass spectrometer which deal with one such aspect of cluster photochemistry related to generation of multiply charged atomic ions upon excessive ionization of cluster constituents (Coulomb explosion) at low intensity laser field (∼10  W/cm ). To understand the mechanism of laser-cluster interaction, laser as well as cluster parameters were varied.

Effect of cluster expansion on photoionization of iron pentacarbonyl doped inert gas clusters under gigawatt intensity laser irradiation.

Rationale: The aim of the investigation was to understand the variation in ionization dynamics of inert gas clusters upon doping with species with lower ionization energy than the inert gas constituent. It was postulated that the use of dopant species having lower ionization energy would lead to facile ionization of doped inert gas clusters, resulting in enhancement of the charge state of atomic ions compared with those obtained for pure inert gas clusters.

Methods: Inert gas clusters (Ar(n), Kr(n) or Xe(n)) doped with iron pentacarbonyl were generated by supersonic expansion and subjected to gigawatt intensity laser pulses (266, 355, 532 and 1064 nm wavelengths) obtained from a nanosecond Nd:YAG laser.