Ab initio methods have been employed to study the conformational behavior and chiroptical properties of acyclic, structurally related aldehydes, ketenes, and diazoalkanes of the type MeCHRCH=XY. The study involved aldehydes 1, 4, and 7 (XY = O, R = H, Me, Et, correspondingly), ketenes (1-alken-1-ones) 2, 5, and 8 (XY = CO, R = H, Me, Et), and 1-diazoalkanes 3, 6, and 9 (XY = NN, R = H, Me, Et). Geometries were optimized at the B3LYP/6-31G level, stationary points were characterized by vibrational frequency analysis, and final energies of 7-9 were obtained at the B3LYP/6-311+G//B3LYP/6-31G level. The chiroptical properties were calculated by the CIS/6-31+G method. It was found that rotational barriers of the functional group (CHXY) about the CC bond are lowered in the following order: aldehydes (1.5-2.1 kcal mol(-1)) > ketenes (1.3-1.6) > diazoalkanes (0.5-0.7). A conformer with the C=X bond eclipsed by an alpha-hydrogen is the global minimum of the ketenes and diazoalkanes, unlike the aldehydes where eclipsing by an alpha-alkyl group is preferred over a hydrogen. In all three classes of compounds, the optical rotational strength of the n-pi transition is greatest for conformers with the dihedral angle, CCCX, in the range 80-100 degrees. Within this range, the signs of the n-pi rotational strengths for the ketenes and diazoalkanes are opposite to ones for the aldehydes. As a whole, the torsional dependencies of the n-pi rotational strength of the ketene and diazo chromophores can be explained within the framework of a model of "through-bond" perturbation. CD spectra of (S)-alpha-methyl-substituted butanal (7), 1-penten-1-one (8), and 1-diazobutane (9) were obtained experimentally. The calculated chiroptical properties of equilibrium mixtures of conformers of compounds 7-9 are in agreement with experimental data.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/jo971612d | DOI Listing |
Angew Chem Int Ed Engl
December 2024
Indian Institute of Science Education and Research Pune, Chemistry, Dr. Homi Bhabha Road, 411008, Pune, INDIA.
Two-dimensional (2D) chiral hybrid perovskites A2PbI4 (A: chiral organic ion) enable chirality controlled optoelectronic and spin-based properties. A+ organic sublattice induces chirality into the semiconducting [PbI4]2- inorganic sublattice through non-covalent interactions at organic-inorganic interface. Often, the A+ cations in the lattice have different orientations, leading to asymmetry in the non-covalent interactions.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Nankai University, School of Materials Science and Engineering, CHINA.
Chiral hybrid organic-inorganic metal halides (HOMHs) hold great promise in broad applications ranging from ferroelectrics, spintronics to nonlinear optics, owing to their broken inversion symmetry and tunable chiroptoelectronic properties. Typically, chiral HOMHs are constructed by chiral organic cations and metal anion polyhedra, with the latter regarded as optoelectronic active units. However, the primary design approaches are largely constrained to regulation of general components within structural formula.
View Article and Find Full Text PDFChem Sci
December 2024
Van't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
Development of chiral organic materials with a strong chiroptical response is crucial to advance technologies based on circularly polarized luminescence, enantioselective sensing, or unique optical signatures in anti-counterfeiting. The progress in the field is hampered by the lack of structure-property relationships that would help designing new chiral molecules. Here, we address this challenge by synthesis and investigation of two chiral macrocycles that integrate in their structure a pseudo-meta [2.
View Article and Find Full Text PDFACS Nanosci Au
December 2024
Department of Chemistry, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
The dynamic control of chiral (enantiomeric) responses in chiral host-guest complexes through external stimuli is a significant challenge in modern chemistry for developing smart stimuli-responsive materials. Herein, we report the (chir)optical properties and chiral recognition behavior of water-soluble chiral naphthotubes () under the influence of hydrostatic pressure as an external stimulus. The hydrostatic pressure spectral profiles compared to those obtained at normal pressure revealed the dynamic behavior of under hydrostatic pressure, owing to the flexible linker.
View Article and Find Full Text PDFSmall
December 2024
State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
Currently, circularly polarized luminescence (CPL) has drawn wide interest in 3D display, information storage, and optical sensing. However, traditional synthetic paths are often accompanied by low chiral optical intensity and complex processes. Cellulose nanocrystals (CNCs), with the properties of liquid crystals, can spontaneously arrange into the left-handed layered nanofilm, which enables them candidates in the construction of CPL materials.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!