Spectrophotometric Determination of Acidity Constant of 1-Methyl-4-[4'-aminostyryl]quinolinium Iodide in Aqueous Buffer and Micellar Solutions in the Ground and Excited States

Abstract

Electronic absorption and excitation spectra of 1-methyl-4-[4'-amino styryl]quinolinium iodide (Q-NH2) were measured in aqueous buffer and micellar solutions. The acid dissociation constants in ground and excited states, pK and pK*, were determined spectrophotometrically and amount for the aqueous solution to 3.24 and 1.19, respectively and the pK and pK* for the (Q-NH2) in sodium dodecyl sulphate are 3.72 and-1.95. The results indicated that the pks of the micellar solution is higher than that of the aqueous solution due to the concentration of protons at the micellar interface which suppress the protonation in the ground state. This reflects the large difference between the excited and the ground state dissociation constants of the micellar solution. The mechanism of the studied reactions is discussed.

A simple interfacial pH detection method for cationic amphiphilic self-assemblies utilizing a Schiff-base molecule

“…Recently, several investigations have suggested a discrepancy in the interfacial pH from the bulk pH in various micellar systems, due to micro-heterogeneous compartmentalization. [26][27][28][29][30][31][32][33] However, quantitative estimation of the interfacial pH in these systems has rarely been addressed. Identification of pH at such bilayer interfaces is extremely difficult, due to the complexity and micro-heterogeneous nature of the membrane.…”

Synthesis, Tautomerism Study, Antimicrobial Evaluation and Cytotoxicity of Some New Bis(Arylazo)-Terpyrazoles

“…In an attempt to establish new precursors, the preparation of which is less expensive than β-enaminones and used in such heterocyclic synthesis, it was considered interesting to examine the synthesis and responces of type β-hydroxyenones, R-CO-CH=CHOH. Given the above literatures and continued our preceding efforts within the bioactive heterocyclic synthesis, bis-heterocyclic compounds [20][21][22][23][24][25] and our previous work to synthesize and study spectrophotometrically arylazo and bisarylazo derivatives of heterocyclic dyes [26,27] to surve their utility as photoprobes, and for hydrogen ion concentration sensing [28][29][30]. Herein, novel sodium 3,3'-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)bis(3-oxopropenolate) reported the synthesis (2) and its reactions with hetaryldiazonium salts to yield bis-hydrazonal for the synthesis of bis(arylazo)-terpyrazoles and utility of the physical constrains approach for determining its pK's to elucidate the more best tautomeric form via correlation the acid dissociation constant with Hammett substituent's constants using Hammett equation.…”

Synthesis, Characterization, Tautomeric Structure and Solvatochromic Behavior of Novel 4-(5-Arylazo-2-Hydroxystyryl)-1-Methylpyridinium Iodide as Potential Molecular Photoprobe

“…In the light of the above findings we have continued our efforts to synthesize and study spectrophotometrically arylazo derivatives of heterocyclic compounds and merocyanine dyes to explore their applications as photoprobes, and for pH sensing and water sensing in organic solvents [ 23 , 24 , 25 , 26 , 27 , 28 ]. We display here our interest in the synthesis of 4-(5-arylazo-2-hydroxystyryl)-1-methylpyridinium iodide using and applying the physical constraints approach to evaluate its acid dissociation constant to elucidate the actual tautomeric structure in both its ground and excited states via correlated pK′s and pK*′s by the Hammett equation.…”