Manganese complexes stability constants

Amine-extraction equilibria can also be modeled by chemical-reaction equilibrium constants. Figure 8.3-3 indicates that cations such as iron(IIl), zinc, cobelt(ll) and coppeifU) exhibit high distribution coefficients with chloride solutions, wherese nickel. iron(II), and manganese are not extracted to any great extent. The besis for the differences in distribution coefficients lies mainly in the tendency for the former group of cations to fonn chloride complexes. Stability constants for these complexes are available in the literature,11 and they can be used to develop quantitative phase-equilibrium models. 

Willems et al. [37] used a polarographic method to study the miconazole complexes of some trace elements. Manganese, iron, cobalt, and zinc element formed miconazole complexes with different stability constants. Polarography was used for detecting stability constants. The evolution of the respective formation constants followed the natural (Irving-Williams) order. The stepwise constant of the complexes formed increased from manganese to cobalt and decreased for zinc. The results are discussed with respect to the possible mechanism of action of miconazole. 

In contrast to the ionic complexes of sodium, potassium, calcium, magnesium, barium, and cadmium, the ease with which transition metal complexes are formed (high constant of complex formation) can partly be attributed to the suitably sized atomic radii of the corresponding metals. Incorporated into the space provided by the comparatively rigid phthalocyanine ring, these metals fit best. An unfavorable volume ratio between the space within the phthalocyanine ring and the inserted metal, as is the case with the manganese complex, results in a low complex stability. 

The stability constant (7=0.1, 25 °C) has been reported for the 1 1 manganese(II) complex of the related amide-containing, 15-membered macrocycle l,4,7-trimethylcarboxy-9,14-dioxo-1,4,7,10,13-pentaazacyclopentadecane as 14.7 (log value). ... 

Van den Berg, C.M.G. and Kramer, 3.R., 1979. Determination of complexing capacities of ligands in natural waters and conditional stability constants of the copper complexes by means of manganese dioxide. Anal. Chim. Acta, 106 113-120. 

Mixed donor ligands. AG°, AH°, and AS° values for the formation of complexes between asparaginate and Mn2+ as well as H+, Fe2+, Co2+, Ni2 +, and Zn2+ in aqueous solution at 25°C have been reported.93 Cytostatic Hadacidin, JV-formyl-JV-hydroxyglycine (HAD), forms the complex Mn(HAD) for which spectroscopic and stability constant data have been reported.94 Manganese(n) complexes of human serum albumin have also been studied.95... 

The first-row transition metal ions have borderline hard soft properties. Therefore, there is no simple rule to predict comparative complex stabilities for a given metal ion with the different donor atoms. In contrast, the stability of complexes of these metal ions with a given ligand does follow a general trend. Thus the stability constants for complexes with NTP increase with the metal ion in the order Co + < Mn + < Zn + < Ni " " < Cu " ", which is the usual Irving-Williams order, except for the reversal of cobalt and manganese. The usual decrease in stability with increasing atomic number is observed for the complexes with metal ions of the alkaline earth series. The stabihty of the... 

Zn" > Fe > Cu" > Co" > Mn" > Fe > Ni", is in qualitative agreement with the order of the stability constants of the corresponding cfalorometallate anions, although it is difficult to predict the position of some of the metals that form rather weak complexes, such as cobalt, manganese and iron(II). It appears, therefore, that the extractability of a given metd is more a reflection of the stability of the anionic metal species... 

In the solubility measurements employing radioactively labelled manganese, and at 6 < pH < 13.6, Mn(ll)(aq) concentrations ranging between 1.5 x 10 and 1.5 x 10 M were indicated. Mehra and Glubeli proposed that this corresponded to the formation of a soluble species Mn(HSe)(OH)(aq) and calculated the stability constant of the complex. 

NO adds reversibly to reduced cobalamin, Cbl(II).156 It does not react directly with aquacobalamin(III), (0blni(H2O)), but it does add to Cbl,n(N02 ) and Cblm(NO).175 Acid hydrolysis of the dinitroso species releases nitrite, and binding of nitrite to Cblln(H20) generates Cbln,(. 02 ). This sequence thus affords a nitrite-catalyzed mechanism for NO substitution at Cblln(H20). The reaction of NO with Com porphyrins is quite complex.176 In the first step, NO displaces an axial water ligand to form a weakly bound mono NO complex this mono NO complex reacts with a second molecule of NO to form nitrite and a reduced Co-NO complex. This latter process is called reductive nitrosylation. Manganese(II) porphyrins bind NO very rapidly.177 Stability constants have been measured for the formation of mono and bis NO complexes of Cun(dithiocarbamate)2.157... 

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