RESUMEN El estudio cinético de la reacción de transferencia de átomos de oxígeno (TAO) foto asistida se estudió usando un complejo de dioxo-Mo anclado al TiO2, estimulada por la luz en condiciones ambientales usando trifenilfosfina como molécula modelo. La cinética de la reacción TAO fue estudiada con tres sistemas catalíticos anclados al TiO2: 4,4’-dicarboxilato-2,2’-bipiridina-dioxocloromolibdeno (MoO2L/TiO2), H2MoO4 (H2MoO4/TiO2) y óxido de molibdeno (MoO3/ TiO2).. El catalizador MoO2L/TiO2 permitió la conversión más alta del 90% y una selectividad (al óxido de fosfina) cercana al 100%. MoO3/TiO2 no permitió la oxo-transferencia sugiriendo la importancia del ligando bipiridinico como una conexión electrónica entre la unidad MoO2L y el TiO2. Adicionalmente, se observó que cuando se incrementa el flujo fotónico, el rendimiento cuántico y la concentración inicial de la PPh3, aumenta la velocidad de reacción de la TAO para el sistema MoO2L/TiO2.

ABSTRACT Kinetic study of the photo-assisted oxygen atom transfer reaction (OAT) using a dioxo-Mo complex anchored on TiO2, stimulated by light, was performed at ambient conditions using triphenylphosphine (PPh3) as a model molecule. The kinetic of the OAT reaction was studied with three catalytic systems: 4,4’-dicarboxylate-2,2’-bipyridine-dioxochloromolybdenum (MoO2L/TiO2), H2MoO4 (H2MoO4/TiO2) and molybdenum oxide (MoO3/ TiO2) anchored to TiO2. The MoO2L/TiO2 gives conversion higher than 90% and selectivity (to phosphine oxide) close to 100%. MoO3/TiO2 did not allow the oxo-transference, suggesting the importance of the bipyridine ligand as an electronic connector between MoO2L unit and TiO2. With the MoO2L/TiO2 system was observed that when the photonic flux increases, the quantum yield, and the OAT reaction rate increases.

Several models for the estimation of thermodynamic properties of layered double hydroxides (LDHs) are presented. The predicted thermodynamic quantities calculated by the proposed models agree with experimental thermodynamic data. A thermodynamic study of the anion exchange process on LDHs is also made using the described models. Tables for the prediction of monovalent anion exchange selectivities on LDHs are provided. Reasonable agreement is found between the predicted and the experimental monovalent anion exchange selectivities.

The synthesis of layered double hydroxides (LDHs) by hydrothermal-LDH reconstruction and coprecipitation methods is reviewed using a thermodynamic approach. A mixture model was used for the estimation of the thermodynamics of formation of LDHs. The synthesis and solubility of LDHs are discussed in terms of standard molar Gibbs free energy change of reaction. Data for numerous divalent and trivalent metals as well as for some monovalent and tetravalent metals that may be part of the LDH structure have been compiled. Good agreement is found between theoretical and experimental data. Diagrams and tables for the prediction of possible new LDH materials are provided.