Room-Temperature Phosphorescence of 1-Bromonaphthalene upon Formation of Beta-Cyclodextrin Ternary Complexes with Alcohols and Surfactants: Optimization of Analytical Figures of Merit by Rigorous Equilibrium Studies

Abstract

Room-temperature phosphorimetry of ternary β-cyclodextrin complexes of the model compound 1-bromonaphthalene has been examined. The selected third partners were alcohols (cyclohexanol, cyclopentanol, and 1-pentanol) and surfactants (Triton X-100 and sodium dodecyl sulfate). A thorough analysis of all equilibria involved in the interaction between the components is performed and discussed. A computational procedure, not previously employed to study this type of complex systems, is used for the determination of the equilibrium constants and stoichiometries of the formed species. It is shown that a rigorous analysis of the equilibria is necessary for a proper optimization of analytical methods based on roomtemperature phosphorescence of ternary complexes. The best working conditions are inferred from the examination of three-dimensional and contour plots of the ternary complex concentration as a function of those of the reagents. The latter plots are constructed once the relative stabilities of all intervening species are known. On the basis of the calibration results, the relative advantages of employing the examined systems for determining the studied compound are presented.

Enantioselective room temperature phosphorescence detection of non-phosphorescent analytes based on interaction with β-cyclodextrin/1-bromonaphthalene complexes

“…0.83 ± 0.06 ms. The pre-exponential weight factors A 1 and A 2 in Table 1 point to a ratio of 2:1 for complexes (1) and (2).…”

“…This should be expected since in the presence of oxygen mostly the fraction of MT present in the ternary complex (3) will contribute to the signal. The relative levels of the complexes (1), (2), and (3) will change with the MT concentration, resulting in an Stype curve, as depicted in Fig. 5.…”

“…Interestingly, there are exceptions to this rule: intense RTP of 1-bromonaphthalene (1BrN) in aqueous ␤-cyclodextrin (␤-CD) solutions has been observed under aerated conditions in the presence of alcohols (tert-butyl alcohol, cyclohexanol, cyclopentanol, and 1-pentanol) [1][2][3], alkanes (cyclohexane, bromocyclohex-ane, and 1,2-dibromoethane) [3], surfactants (triton X-100, sodium dodecyl sulfate, dodecylbenzene sulfonate, and deoxycholate) [2,4,5], or polymers (p-octylpolyethylene glycol phenylether) [6]. This phenomenon can be attributed to the formation of ternary complexes that protect the phosphorophore (1BrN) in the excited triplet (T 1 ) state from quenching by oxygen.…”

Spectroscopic study on binding behaviors of different structural nonionic surfactants to cyclodextrins

“…Like OPE and TX, linear aliphatic alcohols are also able to bind with β-CD [43] and greatly enhance the phosphorescence from BN in aerated aqueous solution of β-CD [40]. Addition of 1-butanol into the phosphorescent OPE/β-CD/BN or TX/β-CD/BN systems was examined to compare the complex stability.…”

“…As a result of the preferential binding of surfactants to CDs, surfactants will have a significant effect on the wide applications of the inclusion complexes of CDs with substrates in above areas mentioned. A few groups have studied the interaction of CD with cationic, nonionic, and anionic surfactants by conductance [20][21][22][23][24][25][26][27][28], surface tension [28][29][30][31][32], NMR [33,34], and fluorescence and phosphorescence [35][36][37][38][39][40]. In most cases, inclusion complexes with the predominant stoichiometry of 1:1 were formed in aqueous solutions and thermodynamic and kinetic parameters were determined to evaluate the complex stability of ionic surfactants with CDs.…”