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KEYWORDSSome new dimethine and bis-dimethine, cyanine dyes derived from benzo [2,3-b; 2`,3`-b`]bis-pyrazolo[4,5-b]-l,4-(oxa-, thia-, and pyra-)-zine-6,12-dione were synthesized. Effect of chemical structure on the electronic visible absorption spectra of all the synthesized cyanine dyes was investigated in 95% ethanol solution. Effects of solvent and/or solution pH on the electronic visible absorption spectra of some selected synthesized cyanine dyes were also examined in pure solvents having different polarities and/or in aqueous universal buffer solutions, respectively. Structural confirmations were carried out through elemental analysis, mass spectroscopy, IR and 1 H NMR spectra.

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A new pyrazolo[4,3-e]-1,3,4-oxadiazine heterocyclic ring system was prepared and employed to synthesize cyanine dyes of different methine types, including monomethine (simple cyanine) and trimethine (carbocyanine). The antibacterial activity of all the newly synthesized compounds was investigated against some bacterial strains. The electronic absorption spectra of the dyes were studied in absolute ethanol. The structure of all the synthesized compounds was identified via elemental and spectroscopic analysis. The antibacterial activity of some selected newly synthesized compounds, as representatives, against some bacterial strains, Pseudomonas, Serratia, Bacillus cereus, Escherichia coli, and Staphylococcus citrus, was investigated and the inhibition zone diameter IZD is recorded in Table 1. The results revealed that the selected compounds Eissa Scheme I Route to bis mono methine cyanine dyes incorporating pyrazolo-oxadiazine heterocyclic ring system Fayez M. EissaPyrazolo[4,3-e]-1,3,4-oxadiazine heterocyclic ring system was obtained from 4-bromo-3-methyl-1-phenypyrazol-5-one and a bimolar ratio of acetic acid azide of hydrazine derivatives. A ring closure reaction, involving dehydration and dehydrobromination, was carried out. The resultant heterocyclic ring system was quaternized, and the quaternized compound was employed to establish bis mono methine cyanine dyes. Scheme IIRoute to bis tri methine cyanine dyes incorporating pyrazolo-oxadiazine heterocyclic ring system Fayez M. Eissa