Cobalt-porphyrin solid state

Casting the complex solution of a metalloporphyrin and a polymer ligand such as poly(vinylimidazole-co-alkylmethacrylate) (Olm in Fig. 9-8), for example, on a Teflon plate and drying, yielded both a homogenously dispersed metalloporphyrin in a solid state and a mechanically tough membrane [26]. The Tg of the membrane was increased, for example, from -1 °C for the Olm itself to 6 °C and the membrane became brittle after the incorporation of 40 wt.% cobalt porphyrin this was explained by the stiffening effect of the incorporated... 

Figure 9-15. Dual-mode oxygen transport in the solid-state polymer membrane containing cobalt porphyrin as a fixed carrier of oxygen.

Measurement of Oxygen-Binding Rate Constants for Solid State Cobalt Porphyrin-Polymer Complexes (Section 9.2.4) [27]... 

Jiang L, Cui L, He X. Cobalt-porphyrin noncovalently functionalized grapheme as nonprecious-metal electrocatalyst for oxygen reduction reaction in an alkaline medium. J Solid State Electrochem 2015 19 497-506. 

Interestingly, these complexes bind oxygen with the same affinity as cobalt substituted myoglobin and hemoglobin in the solid state and in toluene. More elaborated models await the synthesis of picket fence porphyrins with different pickets ... 

Muthukumar P, John SA (2014) Efficient oxidation of hydrazine using amine-fiinctionalized cobalt and nickel porphyrin-modified electrodes. J Solid State Electrochem 18 2393-2400... 

B. Preparation of and Oxygen Adsorption In Solid-State Polymer-Attached Cobalt-Porphyrins... 

The complex often loses its activity to bind a gaseous molecule rapidly after fixation in a dry polymer. A solvent or a polymer residue occupies the sixth-coordination site (binding site) of the complex during the solid-state polymer preparation (e.g., casting to form a membrane) procedure or after the immobilization. A permeate molecule has to displace the occupant, and the reaction becomes very slow. If the gaseous molecule-binding site of the complex is kept vacant after the dry polymer preparation, this complex very rapidly reacts as a carrier, even in the solid state. Solid membranes have been successfully prepared by a combination of specific cobalt-porphyrins and polymer attachment of the complex [27-29]. 

Example 5 Preparation of Solid-State Membrane of the Polymer-Attached Cobalt - Porphyrin... 

Example 6 Measurement of the Oxygen-Binding Reaction to the Polymer-Attached Cobalt-Porphyrin in the Solid State [2]... 

Figure 6 Recombination reaction of the photodissociated oxygen to the cobalt-porphyrin fixed in the solid-state membrane. Spectral change after laser flash irradiation and plots (insert) of apparent oxygen-binding rate constant (A app) versus oxygen concentration around the cobalt—porphyrin in the polymer membrane (p ).

The deoxy-oxy cycle was repeated at 1-min intervals and recorded 1.2 X 10 times (about 6 months) by changing the atmosphere of the cobalt-porphyrin polymer membrane from reduced pressure (about 2 cm Hg) to laboratory air pressure (76 cm Hg) at ambient temperature. Lifetime or half-life periods for the oxygen-binding ability were estimated to be 6 months for Structure (6) in the solid membrane state. The corresponding cobalt-porphyrin (6) in homogeneous toluene solution was able to repeat the oxy-deoxy cycle with a lifetime close to only 1 day. 

The dashed curves with the larger peak currents in Figure IB were obtained during the first voltammetric scan from 0.2 V with the cobalt center of the incorporated porphyrin in its oxidized state (enhanced cathodic peak for reduction of RuiNHale ) or its reduced state (enhanced anodic peak for oxidation of Os(bpy)3 ). The solid curves show the steady responses obtained in the absence of incorporated porphyrin or when the voltammetric scans were restricted to the range between 0.2 and —0.5 V or between 0.2 and 0.8 V so that the cobalt center remained in its reduced or oxidized state, respectively. The areas between the dashed and solid curves in Firare IB were used to measure the quantities of CoP(pyH)4 incorporated in me Nafion coatings. 

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