1
|
Mazzeo G, Pedotti S, Longhi G, Patti A, Abbate S. Spectroscopic investigation on 1,2-substituted ferrocenes with only planar chirality: How chiroptical data are related to absolute configuration and to substituents. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 272:121010. [PMID: 35180485 DOI: 10.1016/j.saa.2022.121010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 06/14/2023]
Abstract
Single enantiomers of three 1,2-substituted ferrocene derivatives, i.e. 1-methoxymethyl-2-hydroxymethylferrocene (1), 1-formyl-2-hydroxymethylferrocene (2) and 1-iodo-2-hydroxymethylferrocene (3), sharing the common hydroxymethyl substituent and the presence of planar chirality only, were investigated for their spectroscopic (IR and UV) and chiroptical (VCD and ECD) properties. Both enantiomers of 1 were obtained for the first time in optically pure form by lipase-catalyzed kinetic resolution of the corresponding racemate (±)-1 and separately converted into formyl derivatives (+)-2 and (-)-2. The experimental spectroscopic and chiroptical data were compared with DFT calculated spectra and excellent correspondence was found for all compounds, allowing one to confirm the previously assigned absolute configurations. The common features in the VCD spectra of a doublet between 940 and 965 cm-1 and the short-wavelength (about 200 nm) doublet and the longest wavelength band in the ECD spectra were analyzed to test whether they may be taken as markers of the absolute configuration (AC). The predominance of conformers with intramolecular hydrogen bond for the first two investigated compounds is predicted by conformational analysis and also confirmed by NMR.
Collapse
Affiliation(s)
- Giuseppe Mazzeo
- Dipartimento di Medicina Molecolare e Traslazionale (DMMT), Universita di Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Sonia Pedotti
- Institute of Biomolecular Chemistry - CNR, Via Paolo Gaifami 18, 95126 Catania, Italy
| | - Giovanna Longhi
- Dipartimento di Medicina Molecolare e Traslazionale (DMMT), Universita di Brescia, Viale Europa 11, 25123 Brescia, Italy; INO-CNR, Sede Secondaria di Brescia, via Branze, 45 - 25123 Brescia, Italy
| | - Angela Patti
- Institute of Biomolecular Chemistry - CNR, Via Paolo Gaifami 18, 95126 Catania, Italy.
| | - Sergio Abbate
- Dipartimento di Medicina Molecolare e Traslazionale (DMMT), Universita di Brescia, Viale Europa 11, 25123 Brescia, Italy; INO-CNR, Sede Secondaria di Brescia, via Branze, 45 - 25123 Brescia, Italy.
| |
Collapse
|
2
|
Koenis MAJ, Nicu VP, Visscher L, Kuehn C, Bremer M, Krier M, Untenecker H, Zhumaev U, Küstner B, Buma WJ. Vibrational circular dichroism studies of exceptionally strong chirality inducers in liquid crystals. Phys Chem Chem Phys 2021; 23:10021-10028. [DOI: 10.1039/d1cp00854d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Chiral dopants are used in liquid crystal displays to introduce uniform helical alignment. VCD can provide unambiguous determination of the absolute configuration and structural details of such a dopant, while X-ray crystallography fails.
Collapse
|
3
|
Vibrational Circular Dichroism Detects Symmetry Breaking due to Conformational Mobility in C2-Symmetry Chiral Molecules and Provides Further Insight into Inter-Chromophoric Interactions. Symmetry (Basel) 2020. [DOI: 10.3390/sym12111752] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Bicyclo[3.3.1]nonane-2,6-dione (1) and bicyclo[3.3.1]nona-3,7-diene-2,6-dione (2) have been examined by vibrational circular dichroism (VCD), which, as for most C2-symmetric systems, exhibits strong VCD signals. In the case of 2, VCD signals are stronger and sharper with several bisignate doublets; for 1, signals are less intense and broader. The VCD and IR spectra are excellently predicted by DFT calculations: only one conformer is present for 2, while for 1, three main conformers, related through concerted skeleton torsional motions are present (two of them being interchanged by C2-rotation). The VCD spectrum shows specific features for the different conformers, such that correct population factors are crucial for reproducing experimental data. Also, the TD-DFT prediction of ECD (electronic circular dichroism) spectra is good. By comparing the spectroscopic signature of the two molecules (both VCD and ECD) and by careful analysis of the theoretical results, the role of the C=C double bond in compound (2) is evidenced. The double bond contributes toward enhancing the CD response both electronically and vibrationally.
Collapse
|
4
|
Ghidinelli S, Abbate S, Koshoubu J, Araki Y, Wada T, Longhi G. Solvent Effects and Aggregation Phenomena Studied by Vibrational Optical Activity and Molecular Dynamics: The Case of Pantolactone. J Phys Chem B 2020; 124:4512-4526. [PMID: 32396357 PMCID: PMC8007093 DOI: 10.1021/acs.jpcb.0c01483] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Raman and Raman optical activity (ROA), IR, and vibrational circular dichroism (VCD) spectra of (R)- and (S)-pantolactone have been recorded in three solvents. ROA has been employed on water and DMSO solutions, VCD on DMSO and CCl4 solutions. In the last solvent, monomer-dimer equilibrium is present. Due to the low conformational flexibility of the isolated molecule and to the possibility of aggregation, this compound has been used here to test different protocols for computation of the spectroscopic responses taking into account solvent effects. Molecular dynamics (MD) simulations have been carried out together with statistical clustering methods based on collective variables to extract the structures needed to calculate the spectra. Quantum mechanical DFT calculations based on PCM are compared with approaches based on different representations of the solvent shell (MM or QM level). Appropriate treatment of the solvent permits obtaining of good band-shapes, with the added advantage that the MD analysis allows one to take into account flexibility of dimeric structures justifying the broadness of observed bands and the absence of intense VCD couplets in the carbonyl and OH stretching regions.
Collapse
Affiliation(s)
- Simone Ghidinelli
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Sergio Abbate
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy.,Istituto Nazionale di Ottica (INO), CNR, Research Unit of Brescia, c/o CSMT, Via Branze 45, 25123 Brescia, Italy
| | - Jun Koshoubu
- JASCO Corporation, 2967-5 Ishikawa-machi, Hachioji, Tokyo 192-8537, Japan
| | - Yasuyuki Araki
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Takehiko Wada
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Giovanna Longhi
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy.,Istituto Nazionale di Ottica (INO), CNR, Research Unit of Brescia, c/o CSMT, Via Branze 45, 25123 Brescia, Italy
| |
Collapse
|