Ion-Pair Oligomerization of Chromogenic Triangulenium Cations with Cyanostar-Modified Anions That Controls Emission in Hierarchical Materials

TY - JOUR

T1 - Ion-Pair Oligomerization of Chromogenic Triangulenium Cations with Cyanostar-Modified Anions That Controls Emission in Hierarchical Materials

AU - Qiao, Bo

AU - Hirsch, Brandon E.

AU - Lee, Semin

AU - Pink, Maren

AU - Chen, Chun Hsing

AU - Laursen, Bo Wegge

AU - Flood, Amar H.

PY - 2017

Y1 - 2017

N2 - The hierarchical assembly of colored cationic molecules with receptor-modified counteranions can be used to control optical properties in materials. However, our knowledge of when the optical properties emerge in the hierarchical organization and the variety of cation-anion salts that are available to create these materials is limited. In this work, we extend the salts from small halides to large inorganic anions and determine how the structure coevolves with the emission properties using solution assemblies. We study the chromogenic trioxatriangulenium (TOTA+) cation and its coassembly with cyanostar (CS) macrocycles selected to modify tetrafluoroborate (BF4 -) counteranions through formation of 2:1 sandwich complexes. In the solid state, the TOTA+ cation stacks in an alternating manner with the sandwich complexes producing new red-shifted emission and absorption bands. Critical to assigning the structural origin of the new optical features across the four levels of organization (1° → 4°) is the selection of specific solvents to produce and characterize different assemblies present in the hierarchical structure. A key species is the electrostatically stabilized ion pair between the TOTA+ cation and sandwich complex. The red-shifted features only emerge when the ion pairs oligomerize together into larger (TOTA·[CS2BF4])n assemblies. New electronic states emerge as a result of multiple copies of the TOTA+ making π-contact with cyanostar-anion complexes. Our findings and the ease with which the materials can be prepared as crystals and films by mixing the salt with a receptor provide a strong platform for the de novo design of new optical materials.

AB - The hierarchical assembly of colored cationic molecules with receptor-modified counteranions can be used to control optical properties in materials. However, our knowledge of when the optical properties emerge in the hierarchical organization and the variety of cation-anion salts that are available to create these materials is limited. In this work, we extend the salts from small halides to large inorganic anions and determine how the structure coevolves with the emission properties using solution assemblies. We study the chromogenic trioxatriangulenium (TOTA+) cation and its coassembly with cyanostar (CS) macrocycles selected to modify tetrafluoroborate (BF4 -) counteranions through formation of 2:1 sandwich complexes. In the solid state, the TOTA+ cation stacks in an alternating manner with the sandwich complexes producing new red-shifted emission and absorption bands. Critical to assigning the structural origin of the new optical features across the four levels of organization (1° → 4°) is the selection of specific solvents to produce and characterize different assemblies present in the hierarchical structure. A key species is the electrostatically stabilized ion pair between the TOTA+ cation and sandwich complex. The red-shifted features only emerge when the ion pairs oligomerize together into larger (TOTA·[CS2BF4])n assemblies. New electronic states emerge as a result of multiple copies of the TOTA+ making π-contact with cyanostar-anion complexes. Our findings and the ease with which the materials can be prepared as crystals and films by mixing the salt with a receptor provide a strong platform for the de novo design of new optical materials.

U2 - 10.1021/jacs.7b01937

DO - 10.1021/jacs.7b01937

M3 - Journal article

C2 - 28437103

AN - SCOPUS:85018331734

SN - 0002-7863

VL - 139

SP - 6226

EP - 6233

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 17

ER -