Solvatochromism and potentiometic studies of some active nitroso- and nitroso-azo- compounds

Abstract

ester and N-[4-(2-amino-3-hydroxy-pyridin-6-ylazo)phenyl]-acetamide compounds were studied. The dissociation constants were determined potentiometrically. The thermodynamic parameters of dissociation were evaluated. Regression analysis is applied for correlating the different parameters. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds. The electronic character of the substituent and the chemical nature of the solvent are major factors for the observed solvatochromism. Nitroso Pyridin-6-ylazo Triazene Effect of solvents Potentiometry Spectrophotometry

Chromophoric Nucleoside Analogues: Synthesis and Characterization of 6-Aminouracil-Based Nucleodyes

“…21,26a The favorable spectral properties of nucleodyes 5 and 8 compared to 4-nitroazobenzene can be attributed to a stronger donor–acceptor interaction between the 6-aminouracil heterocycle and the nitro group as articulated above. The differences in the extinction coefficients between 5 and 8 and the notable changes with polarity compared to 4-nitroazobenzene confirm that the dye moiety is electronically communicating with the nucleobase and sensitive to its environment.…”

“…21,26 The crystal structure and 1 H NMR spectra of 5 indicate one tautomeric form corresponding to 6-amino-5-(4-nitrophenylazo)uridine. In contrast, two tautomeric forms were observed for 8 in both the solid state and solution.…”

“…The chemical shifts observed in the 1 H NMR spectra for the tautomeric hydrazone proton (=N–NH–) and amide proton (NH–C=O) correspond to the two tautomeric forms seen the crystal structure (Figure 2b and Figure S30). 26a,27 One tautomer, 5-(4-nitrophenylazo)-6-oxocytidine ( 8a , Figure 2c), assumes a tautomeric form similar to that of 5 in which the azo group is hydrogen bonded to the neighboring exocyclic amine. In the other tautomer, 5-(4-nitrophenylhydrazono)-6-oxocytidine ( 8b , Figure 2c), the sugar, and the 4-nitrophenylhydrazone group are both rotated roughly 180° (183° ± 1° and 178° ± 1°, respectively), and the latter is hydrogen bonded to the neighboring exocyclic carbonyl (Figure 2c).…”

Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

“…Attention in our laboratory has escalated regarding the potential of those compounds and their complexes owing to their applicability as potential ligands for a large number of metal ions [2][3][4][5][6][7][8][9][10][11][12][13]. Compounds containing nitrogen and sulphur as donor atoms such as thiouracil (TU) and 6-amino-2-thiouracil (ATU) have an important role to play as anti-cancer and anti-viral activities [14].…”

Solvatochromic absorption and fluorescence studies of adenine, thymine and uracil thio-derived acyclonucleosides

“…Several solvent parameters were used in multiple linear regression equations either each parameter alone or in combination with another as two, three or four components and were presented in Table 5 [38][39][40][41][42][43]. The solvent parameters values are presented in Table 6; where n is refractive index, D is dielectric constant and α, π* and β are solvatochromic parameters.…”