D Ramaiah - Academia.edu (original) (raw)

Papers by D Ramaiah

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The Journal of Organic Chemistry, 1988

ABSTRACT The phototransformations of several 4-benzopyranol systems incorporating the 1,2-dibenzo... more ABSTRACT The phototransformations of several 4-benzopyranol systems incorporating the 1,2-dibenzoylalkene moiety have been studied for steady-state photolysis, product analysis, and nanosecond laser flash photolysis. Under direct photolysis, prototropic reactions leading to 2-pyranols and/or their methoxy analogues are shown to dominate, presumably through the intermediacy of carbocations produced as a result of photodehydroxylation. No products, e.g., butenoic acid/ester derivatives, attributable to intramolecular phenyl groups migration along the 1,2-di-benzoylalkene moiety, are observed. The laser flash photolysis of 4- and 2-pyranols in benzene or methanol shows the formation of triplets, characterized by unusually short lifetimes (submicrosecond), which testify to the reactive nature of the triplets. In addition, in the case of 2-pyranols, longer-lived transient species characterized by absorptions at long wavelengths (700-800 nm) are observed; these are best assigned as biradicals, produced as a result of ring-opening via triplet-mediated Câ-O bond cleavage. 29 references, 3 figures, 1 table.

Photochemistry and Photobiology, 2002

Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high tri... more Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high triplet yields and therefore represent new types of photosensitizers that could be useful for photodynamic therapy. We have analyzed the cytotoxicity and genotoxicity of the bromo derivative 1, the iodo derivative 2 and the corresponding nonhalogenated dye 3 in the absence and presence of visible light. At concentrations of 1-2 lM, 1 and 2 reduced the cloning efficiency of AS52 Chinese hamster ovary cells to less than 1% under conditions that were well tolerated in the dark. Similarly, the proliferation of L5178Y mouse lymphoma cells was inhibited by photoexcited 1 and 2 with high selectivity. The squaraine 3 was much less efficient. Both 1 and 2 induced only few mutations in the gpt locus of the AS52 cells in the presence of light and were not mutagenic in the dark. No mutagenicity with and without irradiation was observed in Salmonella typhimurium TA100 and TA2638. However, both 1 and 2 plus light increased the frequency of micronuclei in AS52 cells. The results indicate that halogenated squaraines exhibit photobiological properties in vitro that are favorable for photodynamic therapeutical applications.

The Journal of Physical Chemistry

... This work was performed under the auspices of the US. Department of Energy by the Lawrence Li... more ... This work was performed under the auspices of the US. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. A Laser Flash Photolysls Study of 2,6-Dlmethyl-3,5-diphenyl-4-pyrone and Related Chromones. ...

Acta Crystallographica Section C Crystal Structure Communications

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