Improving the dyeing and fastness performance of molecular triphenodioxazine on wool and nylon fabrics

Three novel triphenodioxazine acid dyes (phosphorous-containing acid dyes; PAD2-4) modified by phenophosphazine with non-planar conformation were designed and synthesized. Their dyeing and fastness performance on wool and nylon fabrics were discussed in comparison with the performances of traditional triphenodioxazine (TPDO) dyes such as C.I. Direct Blue 106 and C.I. Reactive Blue 198. The excellent dyeing and fastness performance of PAD2-4 on the wool and nylon fabrics were analyzed using DFT calculations. The phosphinic group of these PADs is thought to play a key role in the improvement of the exhaustion dyeing performance; the easier offset face-to-face stacking arrangement was attributed to the overwhelming increase of the rubbing fastness owing to the stronger Van der Waals interactions, as calculated using DFT. A design strategy that includes the introduction of an extra-weak acid group and a zigzagged rigid planar component into the TPDO matrix offers insight into improving the poor exhaustion and fastness performance of traditional TPDOs.