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Pescitelli G, Di Bari L. The Phenomenon of Vibrational Circular Dichroism Enhancement: A Systematic Survey of Literature Data. J Phys Chem B 2024; 128:9043-9060. [PMID: 39279667 DOI: 10.1021/acs.jpcb.4c04143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/18/2024]
Abstract
While the intensity of vibrational circular dichroism (VCD) signals is commonly 104-105 times smaller than that of corresponding IR signals, several kinds of systems display enhanced VCD spectra with g-values (VCD/IR intensity ratio) above 10-3 and even reaching 5 × 10-2 in some exceptional cases. These systems include transition metal and lanthanide complexes, protein and peptide fibrils, short oligopeptide gels, crystalline compounds, gels and solution aggregates of organic compounds. We review the literature on VCD enhancement, focusing on collecting and analyzing data on enhanced g-values. Special attention is given to the mechanisms proposed to produce these effects.
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Affiliation(s)
- Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56126 Pisa, Italy
| | - Lorenzo Di Bari
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56126 Pisa, Italy
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Yoshida J, Yamazaki K, Tateyama K, Yuge H, Sato H. Chiroptical switching behavior of heteroleptic ruthenium complexes bearing acetylacetonato and tropolonato ligands. Dalton Trans 2021; 50:14611-14617. [PMID: 34605516 DOI: 10.1039/d1dt02592a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four types of tris-chelate ruthenium complexes bearing acetylacetonato (acac) and tropolonato (trop) ligands were synthesized and optically resolved into Δ and Λ isomers: [Ru(acac)3] (Ru-0), [Ru(acac)2(trop)] (Ru-1), [Ru(acac)(trop)2] (Ru-2), and [Ru(trop)3] (Ru-3). Chiral HPLC chromatograms, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) of the four ruthenium complexes were systematically investigated. As a result, the absolute configurations of the newly prepared enantiomeric complexes Ru-2 and Ru-3 were determined. For the case of Ru-2, its absolute configuration was also confirmed by single crystal X-ray diffraction analysis. The ECD changes upon chemical oxidation were further investigated for the four complexes. An ECD change in enantiomeric Ru-1 was observed upon oxidation, but the oxidized species soon returned to the neutral state within a few minutes. Enantiomers of Ru-3 also showed explicit ECD changes upon oxidation. Further, the lifetime of the oxidized state was the longest among the four investigated complexes, whereas they racemized in solution at room temperature. In contrast, the enantiomers of heteroleptic complexes (Ru-1 and Ru-2) concurrently exhibited ECD changes, relatively long lifetime of the oxidized state, and nil or quite slow racemization behavior. The coexistence of acac and trop ligands was key to making the competing factors compatible in the resultant ruthenium complexes.
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Affiliation(s)
- Jun Yoshida
- Department of Chemistry, College of Humanities & Sciences, Nihon University, 3-25-40 Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan.
| | - Kana Yamazaki
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Kazunori Tateyama
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Hidetaka Yuge
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Hisako Sato
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-chou, Matsuyama, Ehime 790-8577, Japan
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Cortijo M, Valentín-Pérez Á, Rosa P, Daugey N, Buffeteau T, Hillard EA. Resolution, structures, and vibrational circular dichroism of helicoidal trinickel and tricobalt paddlewheel complexes. Chirality 2020; 32:753-764. [PMID: 32168396 DOI: 10.1002/chir.23211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/29/2020] [Accepted: 02/11/2020] [Indexed: 11/06/2022]
Abstract
It has been recently shown that enantiomers of the helicoidal paddlewheel complex [Co3 (dpa)4 (CH3 CN)2 ]2+ (dpa = the anion of 2,2'-dipyridylamine) can be resolved using the chiral [As2 (tartrate)2 ]2- anion (AsT) and that these complexes demonstrate a strong chiroptical response in the ultraviolet-visible and X-ray energy regions. Here we report that the nickel congener, [Ni3 (dpa)4 (CH3 CN)2 ]2+ , can likewise be resolved using AsT. Depending on the stereochemistry of the enantiopure AsT anion, one or the other of the trinickel enantiomers crystallize from CH3 CN and diethyl ether in space group P421 2 as the (NBu4 )2 [Ni3 (dpa)4 (CH3 CN)2 ](AsT)2 ·[solvent] salt. After resolution, the AsT salts were converted into the PF6 - salts by anion exchange, with retention of the chirality of the trinickel complex. The enantiopure [Ni3 (dpa)4 (CH3 CN)2 ](PF6 )2 ·2CH3 CN and [Co3 (dpa)4 (CH3 CN)2 ](PF6 )2 ·CH3 CN·C4 H10 O compounds crystallize in space groups C2 and P21 , respectively. Both the Ni(II) and Co(II) complex cations are stable towards racemization in CH3 CN. Vibrational circular dichroism (VCD) data obtained in CD3 CN demonstrate the expected mirror image spectra for the enantiomers, the observed peaks arising from the dpa ligand. The VCD response is significant, with Δε values up to 6 Lmol-1 cm-1 and vibrational dissymmetry factors on the order of 10-3 . Density functional theory calculations well reproduce the experimental spectra, showing little difference between the peak position, sign, and intensity in the VCD for the cobalt and nickel complexes. These results suggest that VCD enhancement of these peaks is unlikely, and their remarkable intensity may be due to their rigid helicoidal structure.
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Affiliation(s)
- Miguel Cortijo
- CNRS, University of Bordeaux, ICMCB UMR 5026, Pessac, France.,CNRS, University of Bordeaux, CRPP UMR 5031, Pessac, France
| | - Ángela Valentín-Pérez
- CNRS, University of Bordeaux, ICMCB UMR 5026, Pessac, France.,CNRS, University of Bordeaux, CRPP UMR 5031, Pessac, France
| | - Patrick Rosa
- CNRS, University of Bordeaux, ICMCB UMR 5026, Pessac, France
| | - Nicolas Daugey
- CNRS, University of Bordeaux, ISM, UMR 5255, Talence, France
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Krupová M, Kessler J, Bouř P. Recent Trends in Chiroptical Spectroscopy: Theory and Applications of Vibrational Circular Dichroism and Raman Optical Activity. Chempluschem 2020; 85:561-575. [DOI: 10.1002/cplu.202000014] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/18/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Monika Krupová
- Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic
- Faculty of Mathematics and PhysicsCharles University Ke Karlovu 3 12116 Prague 2 Czech Republic
| | - Jiří Kessler
- Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic
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Merten C, Golub TP, Kreienborg NM. Absolute Configurations of Synthetic Molecular Scaffolds from Vibrational CD Spectroscopy. J Org Chem 2019; 84:8797-8814. [PMID: 31046276 DOI: 10.1021/acs.joc.9b00466] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Vibrational circular dichroism (VCD) spectroscopy is one of the most powerful techniques for the determination of absolute configurations (AC), as it does not require any specific UV/vis chromophores, no chemical derivatization, and no growth of suitable crystals. In the past decade, it has become increasingly recognized by chemists from various fields of synthetic chemistry such as total synthesis and drug discovery as well as from developers of asymmetric catalysts. This perspective article gives an overview about the most important experimental aspects of a VCD-based AC determination and explains the theoretical analysis. The comparison of experimental and computational spectra that leads to the final conclusion about the AC of the target molecules is described. In addition, the review summarizes unique VCD studies carried out in the period 2008-2018 that focus on the determination of unknown ACs of new compounds, which were obtained in its enantiopure form either through direct asymmetric synthesis or chiral chromatography.
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Affiliation(s)
- Christian Merten
- Ruhr Universität Bochum , Organische Chemie II , Universitätsstraße 150 , 44780 Bochum , Germany
| | - Tino P Golub
- Ruhr Universität Bochum , Organische Chemie II , Universitätsstraße 150 , 44780 Bochum , Germany
| | - Nora M Kreienborg
- Ruhr Universität Bochum , Organische Chemie II , Universitätsstraße 150 , 44780 Bochum , Germany
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Pescitelli G, Lüdeke S, Górecki M, Di Bari L. Symmetry-Dependent Vibrational Circular Dichroism Enhancement in Co(II) Salicylaldiminato Complexes. J Phys Chem Lett 2019; 10:650-654. [PMID: 30675786 DOI: 10.1021/acs.jpclett.8b03764] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chiral coordination compounds of Co(II) and other open-shell metal complexes display enhanced vibrational circular dichroism (VCD) spectra associated with the existence of low-lying excited states (LLESs). In addition to the enhancement, a series of Co(II) salicylaldiminato complexes exhibits an almost monosignate pattern of VCD bands, a unique feature if compared with the usual alternation of positive and negative signals. Frequency and excited-state calculations reveal that VCD enhancement and sign reversal selectively affect the normal modes of B symmetry of the C2-symmetric pseudotetrahedral species thanks to their combination with one or more LLES having the same B symmetry. This proves the strict relation between VCD enhancement and monosignate appearance and demonstrates an unprecedented symmetry dependence of the two phenomena.
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Affiliation(s)
- Gennaro Pescitelli
- Department of Chemistry and Industrial Chemistry , University of Pisa , Via Moruzzi 13 , 56126 Pisa , Italy
| | - Steffen Lüdeke
- Institute of Pharmaceutical Sciences , University of Freiburg , Freiburg 79104 , Germany
| | - Marcin Górecki
- Department of Chemistry and Industrial Chemistry , University of Pisa , Via Moruzzi 13 , 56126 Pisa , Italy
- Institute of Organic Chemistry , Polish Academy of Sciences , Warsaw 01-224 , Poland
| | - Lorenzo Di Bari
- Department of Chemistry and Industrial Chemistry , University of Pisa , Via Moruzzi 13 , 56126 Pisa , Italy
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De los Santos ZA, Lynch CC, Wolf C. Optische Chiralitätssensorik mit ligandenfreien, weit verbreiteten Cobaltsalzen. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201811761] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Zeus A. De los Santos
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
| | - Ciarán C. Lynch
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
| | - Christian Wolf
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
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De los Santos ZA, Lynch CC, Wolf C. Optical Chirality Sensing with an Auxiliary‐Free Earth‐Abundant Cobalt Probe. Angew Chem Int Ed Engl 2018; 58:1198-1202. [DOI: 10.1002/anie.201811761] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 11/20/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Zeus A. De los Santos
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
| | - Ciarán C. Lynch
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
| | - Christian Wolf
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 USA
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Pescitelli G, Lüdeke S, Chamayou AC, Marolt M, Justus V, Górecki M, Arrico L, Di Bari L, Islam MA, Gruber I, Enamullah M, Janiak C. Broad-Range Spectral Analysis for Chiral Metal Coordination Compounds: (Chiro)optical Superspectrum of Cobalt(II) Complexes. Inorg Chem 2018; 57:13397-13408. [PMID: 30339376 DOI: 10.1021/acs.inorgchem.8b01932] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Chiroptical broad-range spectral analysis extending from UV to mid-IR was employed to study a family of Co(II) N-(1-(aryl)ethyl)salicylaldiminato Schiff base complexes with pseudotetrahedral geometry associated with chirality-at-metal of the Δ/Λ type. While common chiral organic compounds have well-separated absorption and circular dichroism spectra (CD) in the UV/vis and IR regions, chiral Co(II) complexes feature an almost unique continuum of absorption and CD bands, which cover in sequence the UV, visible, near-IR (NIR), and IR regions of the electromagnetic spectrum. They can be collected in a single (chiro)optical superspectrum ranging from the UV (230 nm, 5.4 eV) to the mid-IR (1000 cm-1, 0.12 eV), which offers a fingerprint of the structure and stereochemistry of the metal complexes. Each region of the superspectrum contributes to one piece of information: the NIR-CD region, in combination with TDDFT calculations, allows a reliable assignment of the metal-centered chirality; the UV-CD region facilitates the analysis of the Δ/Λ diastereomeric equilibrium in solution; and the IR-VCD region contains a combination of low-lying metal-centered electronic states (LLES) and ligand-centered vibrations and displays characteristically enhanced and monosignate VCD bands. Circular dichroism in the NIR and IR regions is crucial to reveal the presence of d-d transitions of the Co(II) core which, due to the electric-dipole forbidden character, would be otherwise overlooked in the corresponding absorption spectra.
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Affiliation(s)
- Gennaro Pescitelli
- Department of Chemistry and Industrial Chemistry , University of Pisa , 56126 Pisa , Italy
| | - Steffen Lüdeke
- Institute of Pharmaceutical Sciences , University of Freiburg , D-79104 Freiburg , Germany
| | | | - Marija Marolt
- Institute of Pharmaceutical Sciences , University of Freiburg , D-79104 Freiburg , Germany
| | - Viktor Justus
- Institute of Pharmaceutical Sciences , University of Freiburg , D-79104 Freiburg , Germany
| | - Marcin Górecki
- Department of Chemistry and Industrial Chemistry , University of Pisa , 56126 Pisa , Italy.,Institute of Organic Chemistry , Polish Academy of Sciences , 01-224 Warsaw , Poland
| | - Lorenzo Arrico
- Department of Chemistry and Industrial Chemistry , University of Pisa , 56126 Pisa , Italy
| | - Lorenzo Di Bari
- Department of Chemistry and Industrial Chemistry , University of Pisa , 56126 Pisa , Italy
| | | | - Irina Gruber
- Institute of Inorganic Chemistry and Structural Chemistry , University of Düsseldorf , D-40225 Düsseldorf , Germany
| | - Mohammed Enamullah
- Department of Chemistry , Jahangirnagar University , Dhaka - 1342 , Bangladesh
| | - Christoph Janiak
- Institute of Inorganic Chemistry and Structural Chemistry , University of Düsseldorf , D-40225 Düsseldorf , Germany
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Górecki M, Carpita L, Arrico L, Zinna F, Di Bari L. Chiroptical methods in a wide wavelength range for obtaining Ln 3+ complexes with circularly polarized luminescence of practical interest. Dalton Trans 2018; 47:7166-7177. [PMID: 29774898 DOI: 10.1039/c8dt00865e] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We studied enantiopure chiral trivalent lanthanide (Ln3+ = La3+, Sm3+, Eu3+, Gd3+, Tm3+, and Yb3+) complexes with two fluorinated achiral tris(β-diketonate) ligands (HFA = hexafluoroacetylacetonate and TTA = 2-thenoyltrifluoroacetonate), incorporating a chiral bis(oxazolinyl)pyridine (PyBox) unit as a neutral ancillary ligand, by the combined use of optical and chiroptical methods, ranging from UV to IR both in absorption and circular dichroism (CD), and including circularly polarized luminescence (CPL). Ultimately, all the spectroscopic information is integrated into a total and a chiroptical super-spectrum, which allows one to characterize a multidimensional chemical space, spanned by the different Ln3+ ions, the acidity and steric demand of the diketone and the chirality of the PyBox ligand. In all cases, the Ln3+ ions endow the systems with peculiar chiroptical properties, either allied to f-f transitions or induced by the metal onto the ligand. In more detail, we found that Sm3+ complexes display interesting CPL features, which partly superimpose and partly integrate the more common Eu3+ properties. Especially, in the context of security tags, the pair Sm/Eu may be a winning choice for chiroptical barcoding.
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Affiliation(s)
- Marcin Górecki
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124 Pisa, Italy.
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