1. K calc 9200 mol -1 dm -3 K calc 9200 mol -1 dm -3 We have developed a model that give an answer to this question and gives the meaning of the parameters [6]. This model produces equations 2-4: 02468101214 0.80 0.85 0.90 0.95 1.00 Emission intensity /a.u.   [  CD] / mol dm -3 In order to apply the Pseudophase Model to reactions under restricted geometry conditions (rgc) the exchange between R f and R b (f: free, b: bound) must be fast in relation to the reactive steps [1]. However, this model has been applied to this kind of reactions in the limit of slow exchange [2-5]. This introduces the following question: 10 4 [DNA]/ mol dm -3 0510152025 10 20 30 40 50 60 (K SV ) obs / mol -1 dm 3 Photochemical reactions are usually faster than these exchange processes, so, in principle, the Pseudphase Model cannot explain the changes in reactivity observed under rgc. [I - ] / mol dm -3 0.000.040.080.12 0 1 2 3 4 0.000.020.040.060.08 0.0 0.1 0.2 0.3 0.4 0.5 [I - ] / mol dm -3 K calc (average) 1147 mol -1 dm -3 K calc (average) 1147 mol -1 dm -3 100 ·[KI] (mol dm -3 ) K app (mol -1 dm 3 ) 3.01.83 2465 1397 3.51.99 2475 1292 4.02.15 2506 1214 4.52.30 2645 1198 5.02.45 2563 1091 5.52.60 2591 1043 6.02.74 2653 1013 8.03.27 2909 932 K app = 1104 mol -1 dm 3 Independent of [Q] DNA bCD Obtaining K: kinetic data Obtaining K: classical procedure Emission intensity /a.u. 0510152025 0.0 0.2 0.4 0.6 0.8 1.0 10 4 [DNA]/ mol dm -3 The developed treatment : · Explains that the Stern-Volmer constant can be dependent on the quencher concentration. · Establishes a quantitative relation between the true binding constant and the apparent binding constant, obtained from kinetic (quenching) data. · Has been applied to the quenching of 1-pyrene-carboxaldehyde by I - in the presence of two different receptors. Quantitative agreement has been found between the predictions of the treatment and the experimental data. On the application of the Pseudophase Model to photochemical reaction in the slow exchange limit Introduction Eva Bernal, María Marchena and Francisco Sánchez*. Departamento de Química Física, Facultad de Química Universidad de Sevilla 1 2 What is the meaning of parameters obtained by fitting the experimental data to the Pseudophase Model, in the case of photochemical reactions? 3 4 Figure 1. Stern-Volmer plot for the quenching of 1-pyrene-carboxaldehyde by iodide at fixed DNA concentration of 3·10 -4 mol dm -3. Figure 2. Plot of (Ksv) obs vs. DNA concentration. The values of (Ksv) obs have been obtained from emission intensity of 1-pyrene-carboxaldehyde at different concentrations of quencher (iodide) as. Figure 3. Plot of emission intensity of 1-pyrene- carboxaldehyde at different  CD concentrations. Figure 5. Stern-Volmer plot for the quenching of 1- pyrene-carboxaldehyde by iodide at different concentrations of  -CD: 3 mM (  ), 5 mM (  ), 6 mM ( ) and 9 mM ( ).. Figure 3. Plot of emission intensity of 1-pyrene- carboxaldehyde at different DNA concentrations. Results and Discussion K 9400 mol -1 dm -3 K 9400 mol -1 dm -3 K 1100 mol -1 dm -3 K 1100 mol -1 dm -3 K calc (mol -1 dm 3 ) ConclusionsReferences R f +M R b K k f k b Products In order to check this model, the quenching of the excited state of 1- pyrene-carboxaldehyde by iodide was studied. These studies was carried out in the presence of DNA and β-cyclodextrin (β –CD), two receptors of different characteristics. The idea is to determine K by a classical procedure and compare the value obtained with that resulting from using equations 2-4. Fast in realtion to [ 1] F.M. Menger, C.E. Portnoy, J. Am. Chem.Soc. 89 (1967) 4698-4703. [2] P. Lopez-Cornejo, F. Sanchez, J. Phys. Chem. B 105 (2001) 10523- 10527. [3] P. López-Cornejo, J.D. Mozo, E. Roldán, M.Domínguez, F. Sánchez, Chem. Phys. Lett. 352 (2002) 33-38. [4] E. Pelizzetti, E. Pramauro, Inorg.Chem. 18 (1979) 882-883. [5] T. Lopes-Costa, F. Sanchez, P. Lopez-Cornejo, J. Phys. Chem. B 113 (2009) 9373-9378. [6] M. Marchena, F. Sanchez, Prog. React. Kinet. Mech. 35 (2010) 27- 80.