Quantitative Structure-Retention Relationships (QSRR) for Chromatographic Separation of Disazo and Trisazo 4,4'-Diaminobenzanilide-based Dyes

For a series of 23 disazo and trisazo 4,4'-diaminobenzanilide-based direct dye molecules, thechromatographic mobilities, extrapolated to modifier-free conditions (RM0 values), were determinedfrom reverse-phase thin-layer chromatography (RP-TLC) experiments. Traditional and rational QSAR/QSPR modelling techniques have been applied to find a quantitative structure-retention relationship (QSRR) for the dyes. Molecular dye structures were energy minimized by both molecular mechanics and quantum chemical calculations. A variety of 1D to 3D molecular descriptors taking into account size, shape, symmetry, electronic structure, atom or group distribution, and hydrophobicity of the dyes was derived from the optimized three-dimensional geometries. Multiple linear regression (MLR) and artificial neural network (ANN) modelling revealed that the R M0 values can be successfully expressed by a combination of hydrophobic and polarity dye structural parameters. Additional comparative molecular field (CoMFA) and similarity index (CoMSIA) analyses suggested almost equal contribution of both steric and electrostatic fields to the chromatographic mobility and the major role of hydrophobic and electrostatic interactions with the chromatographic environment.