Self-Discriminating Termination of Chiral Supramolecular Polymerization: Tuning the Length of Nanofibers

Directing the supramolecular polymerization towards a preferred type of organization is extremely important in the design of functional soft materials. Proposed herein is a simple methodology to tune the length and optical chirality of supramolecular polymers formed from a chiral bichromophoric binaphthalene by the control of enantiomeric excess (ee). The enantiopure compound gave thin fibers longer than a few microns, while the racemic mixture favored the formation of nanoparticles. The thermodynamic study unveils that the heterochiral assembly gets preference over the homochiral assembly. The stronger heterochiral binding over homochiral one terminated the elongation of fibrous assembly, thus leading to a control over the length of fibers in the nonracemic mixtures. The supramolecular polymerization driven by π–π interactions highlights the effect of the geometry of a twisted π-core on this self-sorting assembly

Circularly Polarized Luminescence in Chiral Aggregates: Dependence of Morphology on Luminescence Dissymmetry

The self-assembly of a chiral perylene bisimide bichromophoric derivative possessing a 1,1′-binaphthalene bridge was investigated by adopting two different methodologies, leading to the formation of aggregates with dissimilar morphologies. The chiral nature of the aggregated structures was optically probed with the help of circular dichroism (CD), vibrational circular dichroism (VCD), and circularly polarized luminescence (CPL). The one-dimensional aggregates formed in methylcyclohexane (MCH) exhibited twice the value of luminescence dissymmetry factor (<i>g</i>_lum) when compared with the spherical aggregates formed in chloroform at higher concentration. The summation of excitonic couplings between the individual chromophoric units in an aggregated system is responsible for the remarkably high luminescence dissymmetry exhibited by the chiral aggregates. The nanostructures could be successfully embedded into polymer films, leading to the fabrication of solid-state materials with high CPL dissymmetry that can find novel applications in chiroptical sensing, memory, and light-emitting devices based on organic nanoparticles

Circularly Polarized Luminescence in Chiral Aggregates: Dependence of Morphology on Luminescence Dissymmetry

The self-assembly of a chiral perylene bisimide bichromophoric derivative possessing a 1,1′-binaphthalene bridge was investigated by adopting two different methodologies, leading to the formation of aggregates with dissimilar morphologies. The chiral nature of the aggregated structures was optically probed with the help of circular dichroism (CD), vibrational circular dichroism (VCD), and circularly polarized luminescence (CPL). The one-dimensional aggregates formed in methylcyclohexane (MCH) exhibited twice the value of luminescence dissymmetry factor (<i>g</i>_lum) when compared with the spherical aggregates formed in chloroform at higher concentration. The summation of excitonic couplings between the individual chromophoric units in an aggregated system is responsible for the remarkably high luminescence dissymmetry exhibited by the chiral aggregates. The nanostructures could be successfully embedded into polymer films, leading to the fabrication of solid-state materials with high CPL dissymmetry that can find novel applications in chiroptical sensing, memory, and light-emitting devices based on organic nanoparticles

Nona-Coordinated Chiral Eu(III) Complexes with Stereoselective Ligand–Ligand Noncovalent Interactions for Enhanced Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) of chiral Eu­(III) complexes with nona- and octa-coordinated structures, [Eu­(<i>R</i>/<i>S</i>-iPr-Pybox)­(<i>D</i>-facam)₃] (<b>1-</b><i><b>R</b></i>/<b>1-</b><i><b>S</b></i>; <i>R</i>/<i>S</i>-iPr-Pybox, 2,6-bis­(4<i>R</i>/4<i>S</i>-isopropyl-2-oxazolin-2-yl)­pyridine; <i>D</i>-facam, 3-trifluoroacetyl-<i>d</i>-camphor), [Eu­(<i>S</i>,<i>S</i>-Me-Ph-Pybox)­(<i>D</i>-facam)₃] (<b>2-</b><i><b>SS</b></i>; <i>S</i>,<i>S</i>-Me-Ph-Pybox, 2,6-bis­(4<i>S</i>-methyl-5<i>S</i>-phenyl-2-oxazolin-2-yl)­pyridine), and [Eu­(Phen)­(<i>D</i>-facam)₃] (<b>3</b>; Phen, 1,10-phenanthroline) are reported, and their structural features are discussed on the basis of X-ray crystallographic analyses. These chiral Eu­(III) complexes showed relatively intense photoluminescence due to their ⁵D₀ → ⁷F₁ (magnetic-dipole) and ⁵D₀ → ⁷F₂ (electric-dipole) transition. The dissymmetry factors of CPL (<i>g</i>_CPL) at the former band of <b>1-</b><i><b>R</b></i> and <b>1-</b><i><b>S</b></i> were as large as −1.0 and −0.8, respectively, while the <i>g</i>_CPL of <b>3</b> at the ⁵D₀ → ⁷F₁ transition was relatively small (<i>g</i>_CPL = −0.46). X-ray crystallographic data indicated specific ligand–ligand hydrogen bonding in these compounds which was expected to stabilize their chiral structures even in solution phase. CPL properties of <b>1-</b><i><b>R</b></i> and <b>1-</b><i><b>S</b></i> were discussed in terms of transition nature of lanthanide luminescence

Nona-Coordinated Chiral Eu(III) Complexes with Stereoselective Ligand–Ligand Noncovalent Interactions for Enhanced Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) of chiral Eu­(III) complexes with nona- and octa-coordinated structures, [Eu­(<i>R</i>/<i>S</i>-iPr-Pybox)­(<i>D</i>-facam)₃] (<b>1-</b><i><b>R</b></i>/<b>1-</b><i><b>S</b></i>; <i>R</i>/<i>S</i>-iPr-Pybox, 2,6-bis­(4<i>R</i>/4<i>S</i>-isopropyl-2-oxazolin-2-yl)­pyridine; <i>D</i>-facam, 3-trifluoroacetyl-<i>d</i>-camphor), [Eu­(<i>S</i>,<i>S</i>-Me-Ph-Pybox)­(<i>D</i>-facam)₃] (<b>2-</b><i><b>SS</b></i>; <i>S</i>,<i>S</i>-Me-Ph-Pybox, 2,6-bis­(4<i>S</i>-methyl-5<i>S</i>-phenyl-2-oxazolin-2-yl)­pyridine), and [Eu­(Phen)­(<i>D</i>-facam)₃] (<b>3</b>; Phen, 1,10-phenanthroline) are reported, and their structural features are discussed on the basis of X-ray crystallographic analyses. These chiral Eu­(III) complexes showed relatively intense photoluminescence due to their ⁵D₀ → ⁷F₁ (magnetic-dipole) and ⁵D₀ → ⁷F₂ (electric-dipole) transition. The dissymmetry factors of CPL (<i>g</i>_CPL) at the former band of <b>1-</b><i><b>R</b></i> and <b>1-</b><i><b>S</b></i> were as large as −1.0 and −0.8, respectively, while the <i>g</i>_CPL of <b>3</b> at the ⁵D₀ → ⁷F₁ transition was relatively small (<i>g</i>_CPL = −0.46). X-ray crystallographic data indicated specific ligand–ligand hydrogen bonding in these compounds which was expected to stabilize their chiral structures even in solution phase. CPL properties of <b>1-</b><i><b>R</b></i> and <b>1-</b><i><b>S</b></i> were discussed in terms of transition nature of lanthanide luminescence