Selectivity and sensitivity of metal determination by co-ordination compounds.

Quantum chemical structure calculations for metal co-ordination compounds with various organic ligands allow choice of generalized parameters of chelate electronic structures, to form a basis for systematization and prediction of analytical properties. The extent of the co-ordinative saturation of a metal is measured as the sum of the covalent bonding energies of the two-centre metal interactions with the ligand atoms. The concept of "valence state of the ligand" is considered and characterized by the energy sum of the covalent components of two-centre interactions in the ligand.

Electronic spectra and structure of some phenoxazone-type dyes.

Quantum-mechanical calculations of the electronic structure and spectra of a number of phenoxazone dyes are given. The distribution analysis of pi-electron density in the ground and excited states makes clear the origin of the colour of these compounds and gives the possibility of direct assessment of organic reagents in terms of colour contrast and sensitivity of analytical reactions. This is illustrated for a series of dihydroxy derivatives of phenoxazone dyes.

Properties and construction of azo-dye reagents for inorganic photometric analysis.

An approach to constructing new organic reagents (based on azo dyes) for photometric analysis is described. Its essence is the detailed consideration of the electronic structure of the chromophore nuclei of the dyes in the ground and excited states. Knowing the nature of the electron transition, it is possible to construct the organic reagents with optimal properties.