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. The probe demonstrates excellent selective response for superoxide over other ROSs with nine-fold increase in fluorescence intensity. The detection limit was found to be 0.924 µM. The plausible "turn-on" mechanism has been proposed based on the spectroscopic and quantum chemical data. Usefulness of the probe for selective detection of superoxide was confirmed in mammalian breast cancer cell lines.

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

Synthesis of concave and vaulted 2H-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. The new BINOLs exhibit smaller dihedral angle than BINOL on the diol part; this structural feature can be an assisting factor for better ligation with metals in the metal-catalyzed reactions. Corresponding C2 symmetric [5] and [7]-oxa-helicenoids have an overlapping, sterically crowded geometry.

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. To rationalize these intriguing antiaddition products, the reaction mechanism was elucidated by means of DFT analysis. Additionally, hydroxy-functionalized [7]oxahelicenoid has been resolved in its optically pure forms.

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. The ions generated upon laser-cluster interaction were characterized using a time-of-flight mass spectrometer. RESULTS: Upon interaction of the laser with the doped inert gas clusters, the charge states of the atomic ions were found to increase with the laser wavelength. However, the highest observed charge states were found to be lower for doped inert gas clusters than for pure inert gas clusters, at all laser wavelengths. CONCLUSIONS: Wavelength-dependent generation of multiply charged atomic ions has been explained based on the three stage model, i.e. multiphoton ionization ignited-inverse bremsstrahlung heating, and electron ionization. This model explains enhancement in the charge state of atomic ions with increasing wavelength based on inverse bremsstrahlung heating of the inner ionized electron, which is a more efficient process at longer wavelengths. Inefficient coupling of laser energy in the case of doped inert gas clusters compared with pure inert gas clusters has been rationalized on the basis of accelerated disintegration of the cluster due to facile initial ionization of dopant molecules having low ionization energy. The results suggest that a longer laser wavelength and a slower rate of cluster expansion facilitate the efficient transfer of optical energy into cluster systems.