Complexes of Cadmium II with Phosphates

R represents a residue which does not affect metal ion coordination at the phosphate, i.e., neither in a positive nor negative sense. (R0)2P02 represents the phosphodiester bridge of a nucleic acid acetate (Ac ) is used as a primitive and simple mimic of such a singly negatively charged situation (see also [58]). 

Pyrimidine-nucleoside phosphates furnish representative values for nucleotide comparisons because the pyrimidine residue does commonly not participate 

The values for the M(R-MP) complexes (column 3) were calculated with p7f2(R.Mp) = 6-20 [114,115] and the straight-line equations given in refs [50,52,74,122]. The values for the M(R-DP) complexes (column 4, including the acidity constant) are from Table 7 in ref [115], and for the values of the M(R-TP) species it holds Those for the alkaline earth ion complexes are from Table 2 in ref [119] and all the others from Table IV of ref [116] (see also [117]). 

These values are the acidity constants of the monoprotonated ligands and refer to pTf jL) (eq. 3). The p/fa value of (R0)2P(0)(0H) is ca. 1 despite the piTa difference acetate mimics the complex stabilities of the M[(R0)2(P02] species relatively well [58] (see also text). 

Unfortunately, no comprehensive set of stability constants of metal ion complexes formed with a phosphodiester has been measured [25] the reason is the low basicity of (R0)2P02, i.e., p H (RO) PO2] [33,34], which precludes potentiometric pH 

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