Effects of diphenyl-vinyl-substituted diketopyrrolopyrrole isomers on stacking and luminescence

Two kinds of novel diphenyl-vinyl-substituted diketopyrrolopyrrole derivatives with different configurations, linear shaped R-4DPsvs. S shaped R-2DPs, were synthesized and characterized to explore their structural, optical, and electrochemical properties. The distinct placement of diphenyl significantly affected molecular planarity, conjugation and π-π stacking in the solid state, as confirmed by single-crystal X-ray diffraction analysis. The layer spacing of compounds with 4-diphenyl were approximately 3.30-3.40 Å. These molecules exhibited strong absorption in the visible region (350-680 nm) and emitted magenta fluorescence in solution, whereas 4-diphenyl-substituted derivatives (R-4DPs) displayed more intense absorption and redshift attributed to enhanced conjugation with linear and rigid configuration.