Close Columnar Packing of Triangulenium Ions in Langmuir Films

TY - JOUR

T1 - Close Columnar Packing of Triangulenium Ions in Langmuir Films

AU - Simonsen, Jens Bæk

AU - Kjær, Kristian

AU - Howes, Paul

AU - Nørgaard, Kasper

AU - Bjørnholm, Thomas

AU - Harrit, Niels Holger

AU - Laursen, Bo Wegge

N1 - Paper id:: DOI: 10.1021/Ia803733s

PY - 2009

Y1 - 2009

N2 - Three new tris(dialkylamino)trioxatriangulenium (ATOTA(+)) salts rendered amphiphilic by attachment of two (5a center dot PF6 and 5b center dot PF6) or four (5c center dot PF6) n-decyl chains have been synthesized, and their Langmuir films have been studied by grazing incidence X-ray diffraction (GIXD). Compounds 5a center dot PF6 and 5b center dot PF6 both self-assemble into 2D-crystalline Langmuir monolayers, in which the planar triangular shaped carbenium ions form columnar aggregates segregated from the PF6- ions. The column width is found to be close to the width of the triangulenium moiety itself (similar to 17 angstrom), while the repeat distance along the columnar aggregates is only 3.45 angstrom, implicating a near cofacial columnar structure with only a small tilt of the planar carbenium ions relative to the columnar axis. A detailed Bragg rod analysis confirmed an 8-9 degrees tilt and inferred a large anisotropy in the smearing/thermal displacement along the pi-pi stacking and lamellar packing directions. Specular X-ray reflectivity (SXR) was used to confirm the model derived from the GIXD data and elucidate the average position of the disordered PF6- ions, showing that the majority of the anions are accommodated in the ATOTA(+) layer rather than in the water subphase.

AB - Three new tris(dialkylamino)trioxatriangulenium (ATOTA(+)) salts rendered amphiphilic by attachment of two (5a center dot PF6 and 5b center dot PF6) or four (5c center dot PF6) n-decyl chains have been synthesized, and their Langmuir films have been studied by grazing incidence X-ray diffraction (GIXD). Compounds 5a center dot PF6 and 5b center dot PF6 both self-assemble into 2D-crystalline Langmuir monolayers, in which the planar triangular shaped carbenium ions form columnar aggregates segregated from the PF6- ions. The column width is found to be close to the width of the triangulenium moiety itself (similar to 17 angstrom), while the repeat distance along the columnar aggregates is only 3.45 angstrom, implicating a near cofacial columnar structure with only a small tilt of the planar carbenium ions relative to the columnar axis. A detailed Bragg rod analysis confirmed an 8-9 degrees tilt and inferred a large anisotropy in the smearing/thermal displacement along the pi-pi stacking and lamellar packing directions. Specular X-ray reflectivity (SXR) was used to confirm the model derived from the GIXD data and elucidate the average position of the disordered PF6- ions, showing that the majority of the anions are accommodated in the ATOTA(+) layer rather than in the water subphase.

U2 - 10.1021/la803733s

DO - 10.1021/la803733s

M3 - Journal article

C2 - 19231877

SN - 0743-7463

VL - 25

SP - 3584

EP - 3592

JO - Langmuir

JF - Langmuir

IS - 6

ER -