Direct Evidence for Secondary Interactions in Planar and Nonplanar Aromatic π-Conjugates and Their Photophysical Characteristics in Solid-State Assemblies
Direct evidence for non-covalent secondary interactions in planar and nonplanar aromatic pi-conjugates and their solid-state assemblies is established. A series of horizontally, vertically, and radially expanded oligo(phenylenevinylene)s (H-OPVs, V-OPVs, and R-OPVs, respectively) were designed with a fixed pi-core and variable alkyl chain lengths on the periphery. Single-crystal structures of the OPVs were resolved to trace the secondary interactions that direct the solid-state self-organization and molecular packing of the chromophores. The H-OPVs were found to be planar, and they did not show any secondary interactions in the crystal lattices. The V-OPVs and R-OPVs were found to be nonplanar and to exhibit multiple CH/pi hydrogen-bonding interactions among aryl hydrogen donors and acceptors. The enthalpies of the melting and crystallization transitions revealed that the planar H-OPVs are highly crystalline compared with the nonplanar R-OPVs and V-OPVs. Polarized light microscopy studies revealed the formation of one-dimensional nematic mesophases in H-OPVs. The absolute solid-state photoluminescence quantum yields (PLQYs) of the OPVs were determined using an integrating sphere setup. The highly packed H-OPVs showed low PLQYs compared with those of the weakly packed V-OPVs and R-OPVs. Time-resolved fluorescence decay measurements revealed that the excited-state decay dynamics of highly packed H-OPVs was much faster with respect to their low PLQYs. The decay profiles were found to be relatively slow (with higher life time (tau)) in the V-OPVs and R-OPVs. A field-effect transistor (FET) device was constructed for an OPV sample that showed a hole carrier mobility in the range of 10(-5) cm(2) V-1 s(-1). The present investigation thus provides a new opportunity to trace the role of secondary interactions on pi-conjugated mesophase self-assemblies and their solid-state emission and FET devices, more specifically based on OPV chromophores.
Mehta; Mehta; Thosar, Journal of the Indian Chemical Society, Industrial and News Edition, 1941, vol. 4, p. 170,171, 173
作者:Mehta、Mehta、Thosar
DOI:——
日期:——
Mehta; Mehta; Thosar, Journal of the Indian Chemical Society, Industrial and News Edition, 1941, vol. 4, p. 170,172, 173
作者:Mehta、Mehta、Thosar
DOI:——
日期:——
CH/π-Interaction-Guided Self-Assembly in π-Conjugated Oligomers
作者:Mahima Goel、Manickam Jayakannan
DOI:10.1002/chem.201102670
日期:2012.3.5
using single‐crystal structures. OPVs were designed with appropriate pendants in the aromatic core and varied by hydrocarbon or fluorocarbon tails along the molecular axis. The roles of aromatic π‐stack, van der Waals forces, fluorophobic effect and CH/π interactions were investigated on the theromotropic liquid crystallinity of OPV molecules. Single‐crystal structures of hydrocarbon OPVs provided