Oxygen reduction catalyzed by a Carbohydrazone based compound at liquid/liquid interfaces

Electrocatalysis of molecular oxygen reduction reaction at liquid-liquid interface and DFT computational study of proton transfer from the conjugate acid of 2,2'-dipyridylamineto oxygen

In this study, the catalytic effect of 2,2'-dipyridylamine (DPA) on the reduction of oxygen (O₂) at the polarized water/1,2-dichloroethane (DCE) interface was investigated. Ferrocene (Fc) and tetrathiafulvalene (TTF) were weak electron donors used in this study. Slow reduction of O₂ at the interface containing Fc and TTF was significantly accelerated upon the addition of DPA. Voltammetry and biphasic shake flask experiments revealed that DPA acts as a proton ionophore to transfer protons between the aqueous and organic phases. The PA, GB, and pK_a values of all possible conjugate acids of DPA were calculated. Then, a mechanism was suggested to explain the interaction between protonated DPA and oxygen molecular. The mechanism was computationally analyzed by using density functional theory (DFT). Furthermore, DFT calculations at the B3LYP/6-31G** level of theory showed that the conjugate acid species of DPA transfer proton to O₂ at the interface. The results show that DPA-H²⁺ and DPA-H¹⁺ are the best species to transfer proton to molecular oxygen.

Reaction Kinetics at PDMS-E Emulsion Droplet-Gelatin Interface

In this work, interfacial reaction kinetics between α-[3-(2,3-epoxypropoxy)propyl]-ω-butyl-polydimethylsiloxane emulsion droplets with different sizes and gelatin was studied. The results of amino conversion rate determination show that the reaction proceeded in two steps. Fluorescence spectra analysis indicates that step 1 (0-2 h) should be the adsorption of gelatin on droplet surface. In step 2 (2-13 h), amino conversion rate increased rapidly. The reaction rate in step 2 ( k₂) was obtained by using the 2nd-order approach to model the grafting reaction kinetics. The quantitative relationships among amino conversion rate, droplet size, the concentration of surfactant, reaction temperature, and time were described by linear regression models in given ranges of conditions in step 2. Thermodynamic analysis indicates that the interfacial reaction is an endothermic reaction. After 13 h, the reaction was almost stopped.