Kinetics stability defined

Mn(ii)-based SOD mimics is critical in determining the complex s SOD activity and stability. We have identified the frans-2,3-cyclohexano group as a substituent that increases both the SOD activity - and kinetic stability of the Mn complex. Figure 4 shows the SOD activities and kinetic stabilities (defined by the second-order rate constant (first-order in [H" ] and first-order in [Mn(L)] complex) of the unsubstituted SOD mimic SC-52608, the 2,3-(R,R)-trans-cyc-lohexano substituted SC-54417, and the 2,3-(f ,/ )-8,9-(R,R)-bis(tra s-cyc-lohexano) substituted SC-55858. The values for the dismutation of superoxide by these complexes increase as additional trans-cyclohexano groups are added, with SC-55858 = 1.20 x 10 M s ) having three times more... 

The first observation of sensitivity-stability was reported by Liljenroth (1918) in connection with the autothermal operation of ammonia oxidation reactors. Papers of Damkdhler (1937) and Wagner (1945) went unnoticed. At Union Carbide Corp. Perkins (1938) used zero order kinetics to define a safe range for ethylene oxidation in an unpublished report. His result,... 

Although most colloidal dispersions are not thermodynamically stable, a consequence of the small size and large surface area in colloids, and of the presence of an interfacial film on droplets, bubbles or particles, is that dispersions of these species, having reasonable kinetic stability, can be made. That is, suspended droplets or particles may not aggregate quickly nor settle or float out rapidly and droplets in an emulsion or bubbles in a foam may not coalesce quickly. Many food and personal care product emulsions and suspensions, for example, are formulated to remain stable for months to years. It is crucial that stability be understood in terms of a clearly defined process, and one must consider the degree of change and the time-scale in the definition of stability. 

In colloid science the term colloid stability means that a specified process that causes the colloid to become a macrophase, such as aggregation, does not proceed at a significant rate. Colloid stability is different from thermodynamic stability (see Ref. [978]). The term colloid stability must be used with reference to a specific and clearly defined process, for example, a colloidally metastable emulsion may signify a system in which the droplets do not participate in aggregation, coalescence, or creaming at a significant rate. See also Kinetic Stability, Thermodynamic Stability. 

Metal-containing compounds provide new opportunities for designing unique and defined 3D globular structures and thus complement molecular diversity created by purely organic scaffolds. In this respect, a key requirement is the kinetic stability of... 

Kinetic Stability Although most colloidal systems are metastable or unstable with respect to the separate bulk phases, they may have an appreciable kinetic stability. That is, the state of dispersion may exist for an appreciable length of time. Colloidal species can come together in very different ways therefore, kinetic stability can have different meanings. A colloidal dispersion can be kinetically stable with respect to coalescence but unstable with respect to aggregation, or a system could be kinetically stable with respect to aggregation but unstable with respect to sedimentation. It is crucial that stability be understood in terms of a clearly defined process. See also Colloid Stability, Thermodynamic Stability. 

When the coordination bonds that hold these assemblies together are both stable and inert, their formation from the components occurs under kinetic rather than thermodynamic control and it is thus disputable if they can be truly defined as supramolecular systems. On the other hand, owing to their kinetic stability, some of these species can be further exploited as building blocks in the construction of higher order architectures through a hierarchical self-assembly approach (see for example the molecular sandwiches 13-15). Through this modular approach, multichromophore systems become easily accessible on demand, with a limited synthetic effort. 

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