LOGK1 Predictor Manual

LogK1 is a program for the prediction of logarithmic value of the stability constant of  complex compounds by the first stage. 
1. Draw a ligand or complex structure on the ACD/ChemSketch' page.
2. Run Logk1.bas using Run ChemBasic... command from the File menu.

OVERVIEW

This demo version can predict stability constants for the complexes of  31 metal ions (see the list below) with wide range of ligands containing amine nitrogens and acetic oxygens as donor atoms; for example, polyamines, carboxylic acids, aminoacids, complexones.

THEORY

The basis of the program is the correlation equation of a type:

lg(K1) = a(M) + a(NN5)*n(NN5) + a(NN6)*n(NN6) + a(NO5)*n(NO5) + a(NO6)*n(NO6) + a(OO5)*n(OO5) + a(OO6)*n(OO6), 

where 
n - a number of different types of five- and sixmembered chelate rings in a given complex; 
a - correlation coefficients.

This type of equation is based on well known experimental fact that complexes with five- and six membered chelate rings are most stable in overwelming cases. Complexes with chelate rings of four or more than six members are not so stable and were neglected.

The correlation coefficients were obtained from the analysis of huge range of experimental stability constant values of complexes with polyaminopolycarboxylato ligands. Because of  known divergence of  data under different conditions, the values only for the default conditions are used for correlations. The default conditions: T = 250C, I=0.1, aqueous solutions, values obtained by potentiometric titration. This means that calculated value of stability constant is the value under this conditions!

LgK1 predicts stability constants of  complex compounds only by the first stage, i.e. only a single ligand may be attached to metal ion. It may be large macrocyclic or polychelate ligand or just an ammonia or acetic ligand, but only a single.

CALCULATIONS

Calculations can be performed in the two ways: 

   1) Directly, for the single drawn complex compound. In this case, all bonds must be drawn. It is nesesary that all metal - nitrogen bonds have a "coordination bond" type and all metal - carboxylic oxygen are of "single bond" types (remember that the carboxylic oxygen bounds to metal with lack of hydrogen atom, in contrast to amine nitrogen). After the calculation, the single predicted value is displayed.
 
2) For all complexes which can be formed from the drawn ligand and metal ion with its coordinating number entering in the dialog textboxes.. 

In this case, the program will analyze all the possible variants of connection of one, two, three and so on donor atoms of drawn ligand to the specified metal ion and will calculate logK1 for each variant. All the results will be placed in the current document in the ACD/ChemSketch. 


SCOPE AND LIMITATION

1.    Calculation of log(K1) for the complexes of the following metals is possible: 

Ba2+, Ca2+, Cd2+, Ce3+, Co2+, Cr3+, Cu2+, Dy3+, Er3+, Eu3+, Gd3+, Hg2+, Ho3+, La3+, Lu2+, Mg2+, Mn2+, Nd3+, Ni2+, Pb2+, Pr3+, Sm3+, Sr2+, Tb3+, Th4+, Tm3+, UO22+, VO2+, Y3+, Yb3+, Zn2+

2.   Only the coordination through amine nitrogen or carboxylic oxygen is considered, all the other possible donor atoms are neglected.

3.    The maximum number of donor atoms in ligand (amine nitrogens + carbocylic oxygens) should not exceed 10.

4.    The formation of four-membered chelate rings on metal is considered impossible.

