Fluorescence quenching of 9,10-dicyanoanthracene by oxygen in liquid and supercritical carbon dioxide

Inverse correlation between efficiency of singlet oxygen production and rate constant for oxygen quenching in the S1 state of anthracene derivatives

“…1,2 It was demonstrated for many molecules that k S q was approximately a diffusion-controlled value whereas the rate constant (k T q ) for oxygen quenching of the lowest excited triplet state (T 1 ) was roughly 1/9 of k S q , and this observation was explained reasonably in terms of the difference of spin-multiplicity in the energy transfer from the two excited states to oxygen. As shown in previous papers, [3][4][5][6][7] k S q of anthracenes substituted at the meso-position depends significantly on the electron-donating character of the substituent and is fairly smaller than a diffusion-controlled limit for the derivatives possessing electron-withdrawing substituents such as 9,10dicyanoanthracene (DCNA), CNA and DCLA.…”

Contribution of local density augmentation in the vicinity of 9-cyanoanthracene and dynamic fluorescence quenching by oxygen in liquid and supercritical carbon dioxide

“…22,23 In previous publications, 25,26 the pressure effect on the fluorescence quenching of pyrene by polybromoethanes, Q, with wide quenching ability in liquid solutions has been studied and successfully interpreted on the basis of a kinetic model, which involves the exciplex, (MQ)*, via the encounter complex, 1 (M*Q) en , formed between the lowest excited singlet state, 1 M*, and Q. This model was successfully applied to the fluorescence quenching of DMEA by oxygen (8.5-40.0 MPa) and CBr 4 (8.5-60.0 MPa) 27 and of DCNA by oxygen (8.0-60.0 MPa) 28 in SCF CO 2 at 35 C as well as in liquid CO 2 (10.0-60.0 MPa) at 25 C, and the fluorescence quenching for these systems in SCF CO 2 was shown to be interpreted in the same framework as that in liquid CO 2 , indicating no contribution of local composition enhancement to the quenching in the pressure range examined.…”

“…For this purpose, we examined the fluorescence quenching of CNA by oxygen in liquid CO 2 and n-hexane as well as in SCF CO 2 , and the results are discussed on the basis of the model described previously by us. [26][27][28][29] The absorption and fluorescence spectra of CNA in liquid and SCF CO 2 solutions were also measured to obtain information about the local density augmentation from the static observations. From the results of the dynamic quenching, together with those from the absorption and fluorescence spectra, the contribution of the local composition enhancement to the quenching is discussed.…”

“…The associated high pressure techniques have been described in detail elsewhere. 24,27,28,30 The sample solution of CNA in liquid and SCF CO 2 with oxygen was prepared as follows: an appropriate volume of an n-hexane stock solution of CNA was placed into a high pressure cell with four optical sapphire windows. The solvent was evaporated and the high pressure cell was evacuated, and then filled with CO 2 from a high pressure syringe pump by which fluids can be compressed at pressures up to 200 MPa.…”

Radiationless deactivation of singlet oxygen (1Δg) sensitized by 9-acetylanthracene in liquid and supercritical ethane: local density augmentation in the vicinity of the singlet oxygen and sensitizer molecules

“…Supercritical fluids (SCFs), which appreciably dissolve many compounds, are interesting solvents because their physical properties such as solvent density, viscosity, etc., change significantly with a small increase in temperature and pressure. 1,2 The microenvironment around the solute molecules in SCF solution has been extensively examined by probing bimolecular reactions, including fluorescence quenching, 1,[3][4][5][6][7][8][9][10][11][12][13] rotational diffusion 14 and triplet-triplet annihilation, 15 and also by measuring partial molar volume, 16,17 and absorption and fluorescence spectra. 2,[18][19][20][21] From these static and dynamic studies, local density augmentation and local composition enhancement around the solute molecules, which may arise as a result of the attractive interactions between the solvent and solute molecules in fluid solution with low density, has been observed in some systems.…”