Publications by authors named "Gandikota Venkataramana"

A monomer-through-pentamer series of oligo(1,8-pyrenylene)s was synthesized using a two-step iterative synthetic strategy. The trimer, tetramer, and pentamer are mixtures of atropisomers that interconvert slowly at room temperature (as shown by variable-temperature NMR analysis). They are liquids well below room temperature, as indicated by POM, DSC and SWAXS analysis.

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The first synthesis of a pyrene-containing carbon nanoring, cyclo[12]paraphenylene[2]-2,7-pyrenylene ([12,2]CPPyr), is described. Through a sequence of stepwise macrocyclization using Pd and Ni catalysts followed by aromatization of L-shaped cyclohexane units afforded a [12,2]CPPyr in five steps from commercially available compounds. The UV-vis absorption and fluorescence spectra as well as TD-DFT calculations clarified the unique photophysical and electronic properties of the [12,2]CPPyr.

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A concise, highly regioselective synthesis of 1,8-dibromo-4,5-dialkoxypyrenes has been developed and exploited in the synthesis of some 1,8-pyrenylene-ethynylene macrocycles. The (1)H NMR data and NICS calculations indicate that there is little or no macrocyclic ring current. Concentration-dependent UV-visible studies indicate no aggregation at low concentration, but 8b forms dimers with voids suitable for intercalation of small molecules in the solid state.

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The first example of isolation and X-ray crystallographic structural characterization of two conformers arising from rotation along a diacetylenic bond is reported. In both the conformers extensive pi-pi interactions are observed in the solid state. VT-NMR and fluorescence spectroscopic studies in solution suggest that the closed and open conformers are in equilibrium and that the closed conformer is the predominant species at room temperature.

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