The - Stacked Geometries and Association Thermodynamics of Quinacridon
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- stacked associations of three N,N'-di(n-butyl) quinacridone derivatives, widely used dopants inorganic light-emitting diodes, with different sizes of substituents were investigated in solution at varioustemperatures by 1H NMR spectroscopy. The - stacked geometries were estimated by both the magnitudesof peak shifts with concentration and the directions of peak shifts induced by polar solvents. Two patterns ofgeometries with different - interaction strengths were found to coexist in solution for all the three samples.In both of the patterns, the preferential orientation of the stacking is the approach of the carbonyl groups onone molecule to the nitrogen atoms on the stacked partner, which makes the -deficient aromatic atomsinteract with both -rich and -deficient aromatic atoms of the stacked partner to maximize the electrostaticcomplementarity. Differently, whereas the molecules in one pattern are face-to-face stacked in a parallelfashion and slip two rings relative to one another along with the long axis of the conjugated ring systems, themolecules in the other are either face-to-face stacked in an antiparallel fashion with slight slipping betweenlayers or stacked in a turning fashion. Both association constants obtained by fitting the dilution curves andthermodynamic parameters obtained from van't Hoff analyses revealed unexpectedly three thermodynamicprocesses of aggregations for all the three samples in the temperature region of 298-213 K. The size ofsubstituents on the outer aromatic rings significantly influences the - stacked structures and associationthermodynamics.
- stacked associations of three N,N'-di(n-butyl) quinacridone derivatives, widely used dopants inorganic light-emitting diodes, with different sizes of substituents were investigated in solution at varioustemperatures by 1H NMR spectroscopy. The - stacked geometries were estimated by both the magnitudesof peak shifts with concentration and the directions of peak shifts induced by polar solvents. Two patterns ofgeometries with different - interaction strengths were found to coexist in solution for all the three samples.In both of the patterns, the preferential orientation of the stacking is the approach of the carbonyl groups onone molecule to the nitrogen atoms on the stacked partner, which makes the -deficient aromatic atomsinteract with both -rich and -deficient aromatic atoms of the stacked partner to maximize the electrostaticcomplementarity. Differently, whereas the molecules in one pattern are face-to-face stacked in a parallelfashion and slip two rings relative to one another along with the long axis of the conjugated ring systems, themolecules in the other are either face-to-face stacked in an antiparallel fashion with slight slipping betweenlayers or stacked in a turning fashion. Both association constants obtained by fitting the dilution curves andthermodynamic parameters obtained from van't Hoff analyses revealed unexpectedly three thermodynamicprocesses of aggregations for all the three samples in the temperature region of 298-213 K. The size ofsubstituents on the outer aromatic rings significantly influences the - stacked structures and associationthermodynamics.