Reactivity of Acridine Dye Triplet States in Electron Transfer Reactions

Abstract

Abstract—Rate constants, kq, for the reaction of cationic and neutral acridine orange and 10‐methylacridine orange triplet states (3AOH +, 3AO, 3MAO+) with a series of electron donors have been measured. Two different protolytic forms of the semireduced dye radical are produced by acridine orange triplet quenching at various pHM values in methanolic solution. It is found that k4 decreases with increasing oxidation potential of the reducing agent for all triplet states in a manner which is expected for electron transfer reactions. The different reactivities of the cationic and neutral triplet forms can, therefore, be attributed to the difference in reduction potentials of these species. The difference in reduction potentials is related to the pKM values of triplet state, pKTM, and semireduced dye radical, pKMS, by thermodynamic consideration. pKTM (3AOH+/3AO) is determined to be 11.2. From thispKSM (AOH./AO;) is estimated to be 17–18. This is in striking contrast to the protolytic equilibrium of the semireduced dye radicals found to be pKF= 4.1. We conclude that the last value represents the second protonation equilibrium (AOH+2./AOH). This conclusion is confirmed by spectroscopic data.

Amperometric Detection of dsDNA Using an Acridine‐Orange‐Modified Glucose Oxidase

“…The absorption spectrum in basic ethanol of AO NHBoc (Figure S1 a, red dashed line) showed a redshift of the absorption maximum compared to the absorbance of the free‐base AO (black solid line). This bathochromic shift, which is characteristic of alkylated (or protonated) AO derivatives, conclusively demonstrates the successful attachment of the 14‐atom‐long tether. Finally, after deprotection in HCl/dioxane, the free amine AO NH2 was obtained in a moderate overall yield.…”

Amperometric Detection of dsDNA using an Acridine‐Orange‐Modified Glucose Oxidase

“…The absorption spectrum in basic ethanol of AO NHBoc (Figure S1 a, red dashedl ine) showedaredshift of the absorption maximum comparedt o the absorbance of the free-base AO (black solid line). This bathochromic shift, which is characteristico falkylated (or protonated) AO derivatives, [8,11,18] conclusively demonstrates the successful attachment of the 14-atom-long tether.F inally,a fter deprotection in HCl/dioxane, the free amine AO NH2 was obtained in am oderate overall yield. The amino group in AO NH2 can be used to attach the intercalating species to the deglycosylated enzyme.…”

Potential Applications of Cucurbit[n]urils Inclusion Complexes in Photodynamic Therapy

“…[26a,32] The increase in fluorescence quantum yield and/or change in the fluorescence lifetimes resulting on modulation of fluorescence, can be useful in the detection of the molecules during drug delivery and cellular localization using techniques such as Fluorescence Lifetime Imaging (FLIM), because it could allow greater contrast [55b] and improvements of the signal-to-noise ratio as well as differentiating the emission of the photosensitizer from background noise. [78] MB + 665 [61] 685 [62] 686 [63] 0.03 [61,64] 0.02 [63] 0.52 AE 0.03 [61] 0.370 [62] 0.345 [63] 95,000 (664 nm) [65] MB + @CB [7] 661 [61] 0.22 [61] 0.13 AE 0.01 [31a] 1.49 AE 0.03 [61] AO + 435 [66] 492 [32,66] 450 [67] 550 [66] 535 [66][67] 525 [32] 0.055 [66] 0.041 [66] 0.25 [67] 0.20 [31a] 6.2 [66] 1.7 [66][67] 2.01 AE 0.04 [32] 62,000 (491 nm) [68] pH 12.0 pH 7.0 AO + @CB [7] 485 [32] 508 [32] 0.56 AE 0.02 [p] 3.46 AE 0.02 [32] pH 7.0 RF 450 [69] 370 [69] 530 [35] 0.267 AE 0.01 …”

“…Abs l max /nm Em l max /nm F f t/ns e/M À1 cm À1 Condition [a] MB + 665 [61] 685 [62] 686 [63] 0.03 [61,64] 0.02 [63] 0.52 AE 0.03 [61] 0.370 [62] 0.345 [63] 95,000 (664 nm) [65] MB + @CB [7] 661 [61] 0.22 [61] 0.13 AE 0.01 [31a] 1.49 AE 0.03 [61] AO + 435 [66] 492 [32,66] 450 [67] 550 [66] 535 [66][67] 525 [32] 0.055 [66] 0.041 [66] 0.25 [67] 0.20 [31a] 6.2 [66] 1.7 [66][67] 2.01 AE 0.04 [32] 62,000 (491 nm) [68] pH 12.0 pH 7.0 AO + @CB [7] 485 [32] 508 [32] 0.56 AE 0.02 [p] 3.46 AE 0.02 [32] pH 7.0 RF 450 [69] 370 [69] 530 [35] 0.267 AE 0.01 [70] 0.26 [5] 4.70 [71] 12,200 (450 nm) [72] pH 7.0 RF@CB [7]~380 [71] 532 [71] 0.146…”