The new, unsymmetrical azobenzene-tagged ligand 4-(4-azobenzene)-3,6-di(2-pyridyl)pyridazine, adpp, forms complexes with platinum(II) and platinum(IV), which exist as a mixture of geometrical isomers. The complexes are characterized primarily by their NMR spectra, while the structures of the ligand and its complexes [PtMe2(adpp)], [PtBrMe2(CH2C6H4-4-t-Bu)(adpp)], and [PtBrMe2(CH2C6H3-3,5-t-Bu2)(adpp)] have been structurally characterized. In solution, the compounds undergo easy photochemical trans−cis switching of the azobenzene group, with subsequent slow thermal isomerization back to the more stable trans-azobenzene isomer.
5-Aminouracil (5-AU) is a readily available yet underutilized starting material for the synthesis of labelled nucleobase analogues. We have prepared the derivative of 5-AU with the amine-reactive chromophore 9-chloroacridine for the purpose of investigating its potential as a base-discriminating fluorophore. 9-Chloroacridine readily undergoes substitution by reaction with 5-AU to yield a fluorescent nucleobase that after standard manipulations produced a monomer suitable for incorporation into peptide nucleic acid (PNA) by fluorenylmethyloxycarbonyl (Fmoc)-based oligomerization chemistry. Although the monomer was stable in organic solvents, once incorporated into an oligomer the 5-substitution was found to be thermally labile and hydrolyzed to a small degree in neutral aqueous solution during study of its hybridization to cDNA. We have determined that 5-(acridin-9-ylamino)uracil and related derivatives produce the highly fluorescent acridone and 5-AU by hydrolysis in water.
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