Enantiospecific Desorption Triggered by Circularly Polarized Light

Abstract

The interest in enantioseparation and enantiopurification of chiral molecules has been drastically increasing over the past decades,since these are important steps in various disciplines such as pharmaceutical industry,asymmetric catalysis,a nd chiral sensing.B ye xposing racemic samples of BINOL (1,1'-bi-2-naphthol) coated onto achiral glass substrates to circularly polarized light, we unambiguously demonstrate that by controlling the handedness of circularly polarized light, preferential desorption of enantiomers can be achieved. There are currently no mechanisms knownt hat would describe this phenomenon. Our observation together with as implified phenomenological model suggests that the process of laser desorption needs to be further developed and the contribution of quantum mechanical processes should be revisited to account for these data. Asymmetric laser desorption provides us with ac ontamination-free technique for the enantioenrichment of chiral compounds.

Chiroptical Properties in Thin Films of π-Conjugated Systems

“…Mueller matrix polarimetry (MMP or MME) has been applied to TPPS aggregates, 268 films of BINOL, 73 squaraine derivatives, 269,270 and poly(fluorene-alt-benzothiadiazole)s. 213,214,824 Second-harmonic generation circular dichroism (SHG-CD) measurements have been described for thin films of several classes of π-conjugated systems, including Langmuir−Blodgett films of an aggregating helicene derivative, 304 ques, 73,279,[322][323][324]345,346 azobenzene polymethacrylates, 540 polyisocyanides, 2 8 0 polydiacetylenes, 6 3 3 and poly(3alkylthiophene)s. 281,716 Circular differential scattering (CDS) has been measured or estimated for poly(fluorene)s, 174 poly(acetylene)s, 271 and poly(fluorene-alt-benzothiadiazole)s. 212−214 Circular differential transmission and circular selective reflection have been measured for cholesteric liquid crystals obtained by various samples. 174,213,228,229,272,273 Ellipsometry has been used for porphyrin aggregates, 268,484 poly(phenylenevinylene)s, 815 oligo-and poly(fluorene)s, 213,228,229,273 and poly(fluorene phenylene)s. 692 Finally, the following techniques have also found sporadic applications for thin films of π-conjugated systems: ECD spectroelectrochemistry, 284 circular differential reflectance, 272,286 and transient circular dichroism.…”

“…The time evolution of thin-film ECD spectra of BINOL is displayed in Figure . Further investigations were then performed on SHG-CD experiments, , showing that the films are also optically active in the nonlinear regime. By analyzing the various terms associated with ECD of anisotropic samples, the authors speculated if the PRE effect could be due to what we call the LDLB term (eq in section ).…”

Giant Photoinduced Chirality in Thin Film Ge2Sb2Te5

“…Amorphous GST alloy films excited with linearly polarized fs laser pulses have displayed similar optical anisotropy following crystallization . A recent report on asymmetric laser desorption of enantiomers from a racemic mixture exposed to CPL also supports nonthermal processes in CPL irradiation …”

“…[29] A recent report on asymmetric laser desorption of enantiomers from a racemic mixture exposed to CPL also supports nonthermal processes in CPL irradiation. [30] The preferential alignment of the dominant Ge-Te and Sb-Te bonds perpendicular to the applied electric field observed in simulations, even within a short timescale of 8 ps, implies that effects of a rotating field vector (in the case of CPL) can lead to similar alignment and consequently the formation of chiral centers. This effect is expected to be enhanced in the repeated pulses; as light propagates through the film, the rotation of the field vector amounts to about 24 for 532 nm light and film thickness of 35 nm.…”

Chiral separation and molecular simulation study of six antihistamine agents on a coated cellulose tri‐(3,5‐dimethylphenycarbamate) column (Chiralcel OD‐RH) and its recognition mechanisms

“…Chirality, as a widespread feature in many bioactive compounds, plays a significant impact on a variety of disciplines like biology, medicine, pharmacology, and many branches of chemistry [1–5]. Stereoisomers of chiral drugs often have different pharmacokinetic properties, pharmacological, and toxicological effects.…”