Exciton Coupling of Merocyanine Dyes from H- to J-type in the Solid State by Crystal Engineering.
A key issue for the application of π-conjugated organic molecules as thin film solid-state materials is the packing structure, which drastically affects optical and electronic properties due to intermolecular coupling. In this regard, merocyanine dyes usually pack in H-coupled antiparallel arrangements while structures with more interesting J-type coupling have been rarely reported. Here we show that for three highly dipolar merocyanine dyes, which exhibit the same π-scaffold and accordingly equal properties as monomers in solution, the solid-state packing can be changed by a simple variation of aliphatic substituents to afford narrow and intense absorption bands with huge hypsochromic (H) or bathochromic (J) shifts for their thin films and nanocrystals. Time-dependent density functional theory calculations show that the energetic offset of almost 1 eV magnitude results from distinct packing motifs within the crystal structures that comply with the archetype H- or J-aggregate structures as described by Kasha's exciton theory.
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Andreas
A
Liess
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Aifeng
A
Lv
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Alhama
A
Arjona-Esteban
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
David
D
Bialas
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Ana-Maria
AM
Krause
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Vladimir
V
Stepanenko
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Matthias
M
Stolte
Institut für Organische Chemie, Universität Würzburg , Am Hubland, 97074 Würzburg, Germany.|Center for Nanosystems Chemistry (CNC), Universität Würzburg , Theodor-Boveri-Weg, 97074 Würzburg, Germany.
Frank
0000-0001-7245-0471
F
Würthner
Merocyanine dyes; crystal engineering; dipole moments; dye aggregates; exciton coupling; supramolecular chemistry