Investigation of substituent effect on cool activity of perylene bisimide pigments

In this paper, some derivatives of perylene bisimides are successfully synthesized and characterized using FTIR, HNMR and XRD techniques. In addition, their UV–Vis–NIR reflectance spectra are investigated. Synthesized pigments were planned to have high structural similarities as all of them were N , N ′-diphenyl-3,4,9,10-perylenedicarboximide derivatives. The substituents are selected from two categories including activating groups and deactivating ones. The correlation between substituent electronic properties and NIR features of the synthesized pigments is investigated, while the data of three previously synthesized derivatives are included. The results have revealed interesting approximate correlation between NIR properties and electronic features of the substituents. Electronically activating groups reduce the reflectance values (on white substrate) of the pigments in comparison with nonsubstituted molecule, while deactivating ones increase the reflectance amount. This result can be a starting point for detailed studying of structure–NIR properties correlation in perylene pigments. Crystallinity (%) of the pigments is estimated using XRD patterns, and the probable correlation of this parameter with NIR properties of the pigments is investigated, and no meaningful correlation is detected. All the pigments are NIR-transparent and subsequently are capable to be used as cool pigments.