scholarly journals Chiral Lanthanide Complexes with l- and d-Alanine: An X-ray and Vibrational Circular Dichroism Study

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2729
Author(s):  
Krzysztof Lyczko ◽  
Joanna E. Rode ◽  
Jan Cz. Dobrowolski
Keyword(s):  
Circular Dichroism ◽  
Ir Spectra ◽  
Lanthanide Complexes ◽  
Vibrational Circular Dichroism ◽  
Mirror Reflection ◽  
Electron Configuration ◽  
X Ray ◽  
Lanthanide Contraction ◽  
Contraction Effect ◽  
Circular Dichroïsm

A whole series of [Ln(H2O)4(Ala)2]26+ dimeric cationic lanthanide complexes with both l- and d-alanine enantiomers was synthesized. The single-crystal X-ray diffraction at 100 and 292 K shows the formation of two types of dimers (I and II) in crystals. Between the dimer centers, the alanine molecules behave as bridging (μ2-O,O’-) and chelating bridging (μ2-O,O,O’-) ligands. The first type of bridge is present in dimers I, while both bridge forms can be observed in dimers II. The IR and vibrational circular dichroism (VCD) spectra of all l- and d-alanine complexes were registered in the 1750–1250 cm−1 range as KBr pellets. Despite all the studied complexes are exhibiting similar crystal structures, the spectra reveal correlations or trends with the Ln–O1 distances which exemplify the lanthanide contraction effect in the IR spectra. This is especially true for the positions and intensities of some IR bands. Unexpectedly, the ν(C=O) VCD bands are quite intense and their composed shapes reveal the inequivalence of the C=O vibrators in the unit cell which vary with the lanthanide. Unlike in the IR spectra, the ν(C=O) VCD band positions are only weakly correlated with the change of Ln and the VCD intensities at most show some trends. Nevertheless, this is the first observation of the lanthanide contraction effect in the VCD spectra. Generally, for the heavier lanthanides (Ln: Dy–Lu), the VCD band maxima are very close to each other and the mirror reflection of the band of two enantiomers is usually better than that of the lighter Lns. DFT calculations show that the higher the multiplicity the higher the stability of the system. Actually, the molecular geometry in crystals (at 100 K) is well predicted based on the highest-spin structures. Also, the simulated IR and VCD spectra strongly depend on the Ln electron configuration but the best overall agreement was reached for the Lu complex, which is the only system with a fully filled f-shell.

Shape-conserving enhancement of vibrational circular dichroism in lanthanide complexes

2012 ◽  
Vol 48 (98) ◽  
pp. 11996 ◽  
Author(s):  
Samuele Lo Piano ◽  
Sebastiano Di Pietro ◽  
Lorenzo Di Bari
Keyword(s):  
Circular Dichroism ◽  
Lanthanide Complexes ◽  
Vibrational Circular Dichroism ◽  
Circular Dichroïsm

scholarly journals On the Absolute Stereochemistry of Tolterodine: A Circular Dichroism Study

2019 ◽  
Vol 12 (1) ◽  
pp. 21 ◽  
Author(s):  
Marcin Górecki ◽  
Valerio Zullo ◽  
Anna Iuliano ◽  
Gennaro Pescitelli
Keyword(s):  
Circular Dichroism ◽  
Density Functional ◽  
Vibrational Circular Dichroism ◽  
Time Dependent ◽  
Functional Theory ◽  
X Ray ◽  
Overactive Urinary Bladder ◽  
The Absolute ◽  
Circular Dichroïsm ◽  
Absolute Stereochemistry

Tolterodine (1) is a potent muscarinic receptor antagonist used in the treatment of overactive urinary bladder (OAB) syndrome. Tolterodine is chiral and it was patented, and is currently marketed, as the l-tartrate salt of the (R)-enantiomer. However, the existing literature does not offer an ultimate proof of a stereoselective mode of action of 1. A second open stereochemical issue concerns the absolute configuration (AC) of 1. Neither the original patents nor subsequent studies have established the AC of 1 in an unambiguous way, although the AC of the l-tartrate salt of 1 was assigned by X-ray diffractometry. Finally, neither electronic nor vibrational circular dichroism (ECD and VCD) spectra of 1 are reported so far. We performed a thorough ECD/VCD study of 1 in different solvents and at variable temperatures. Solvent and temperature dependence highlighted the existence of moderate flexibility which was confirmed by molecular modelling. ECD calculations with time-dependent density functional theory (TDDFT) accurately reproduced the experimental spectra and allowed us to confirm the AC of 1 in an independent way.

Synthesis, structures and magnetic properties of heterobimetallic RuIII–3d (3d = Mn, Ni) compounds based on the chiral RuIII building block

2018 ◽  
Vol 42 (19) ◽  
pp. 16237-16243 ◽  
Author(s):  
Jing Ru ◽  
Ru-Fen Zhang ◽  
Yang Shi ◽  
Shao-Liang Zhang ◽  
Qian-Li Li ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Circular Dichroism ◽  
Ir Spectroscopy ◽  
Building Block ◽  
Vibrational Circular Dichroism ◽  
X Ray ◽  
X Ray Crystallography ◽  
Circular Dichroïsm

Two pairs of new chiral RuIII–Mn/Ni compounds have been successfully synthesized and characterized by IR spectroscopy, X-ray crystallography, circular dichroism (CD) and vibrational circular dichroism (VCD) spectra.

scholarly journals Absolute configuration of the antimalarial erythro-mefloquine – vibrational circular dichroism and X-ray diffraction studies of mefloquine and its thiourea derivative

RSC Advances ◽  
2016 ◽  
Vol 6 (85) ◽  
pp. 81461-81465 ◽  
Author(s):  
M. Kohout ◽  
J. Vandenbussche ◽  
A. Roller ◽  
J. Tůma ◽  
J. Bogaerts ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Absolute Configuration ◽  
Circular Dichroism Spectroscopy ◽  
Vibrational Circular Dichroism ◽  
X Ray Diffraction ◽  
Thiourea Derivative ◽  
X Ray ◽  
The Absolute ◽  
Circular Dichroïsm

The long-standing discussion of the absolute configuration of erythro-mefloquine is revisited, showcasing the strength of a combination of experimental and calculated vibrational circular dichroism spectroscopy.

scholarly journals Absolute Configuration Assignment of 3′,4′-di-O-acylkhellactones Using Vibrational Circular Dichroism Exciton Chirality

2015 ◽  
Vol 10 (6) ◽  
pp. 1934578X1501000 ◽  
Author(s):  
Abigail I. Buendía-Trujillo ◽  
J. Martín Torrres-Valencia ◽  
Pedro Joseph-Nathan ◽  
Eleuterio Burgueño-Tapia
Keyword(s):  
Circular Dichroism ◽  
Diffraction Analysis ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Vibrational Circular Dichroism ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aerial Parts ◽  
Configuration Assignment ◽  
Circular Dichroïsm

The 3′R,4 ‘R absolute configuration (AC) of the angular-type pyranocoumarins (-)-3′,4′-di- O-acetylkhellactone (2), (-)-4′- O-acetyl-3′- O-angeloylkhellactone (3), (+)-3′- O-acetyl-4- O-isobutyroylkhellactone (4), and (-)-3′- O-angeloyl-4′- O-senecioylkhellactone (5), isolated from the aerial parts of Prionosciadum thapsoides, was assigned by vibrational circular dichroism exciton chirality (VCDEC), and confirmed by comparison of their VCD frequencies with those calculated using DFT at the B3LYP/DGDZVP level. This again reveals that AC assignments based on optical rotation data are not very confident. Evaluation of Flack and Hooft parameters obtained after single-crystal X-ray diffraction analysis of 3, independently confirmed this AC.

(1S,7S)-7-Methyl-6,9-diazatricyclo[6,3,0,01,6]tridecane-5,10-dione, a tricyclic spirodilactam containing non-planar amide groups: Synthesis, NMR, crystal structure, absolute configuration, electronic and vibrational circular dichroism

1988 ◽  
Vol 53 (11) ◽  
pp. 2447-2472 ◽  
Author(s):  
Petr Maloň ◽  
C. L. Barness ◽  
Miloš Buděšínský ◽  
Rina K. Dukor ◽  
Dick Van der Helm ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Circular Dichroism ◽  
Absolute Configuration ◽  
Optically Active ◽  
Vibrational Circular Dichroism ◽  
X Ray Diffraction ◽  
X Ray ◽  
Circular Dichroïsm ◽  
C Nmr ◽  
Active Precursor

The title spirocyclic dilactam (1S,7S)-7-methyl-6,9-diazatricyclo[6,3,0,01,6]tridecan-5,10-dione (I), a molecule designed to contain non-planar amide groups, has been synthesized from an optically active precursor of known absolute configuration. The relative and absolute configuration have been determined by X-ray diffraction. The conformation of the compound has been investigated by X-ray, 1H and 13C NMR, electronic and vibrational circular dichroism. The compound possesses moderately non-planar amide groups in the two rings of nonequal geometry. The electronic CD is dominated by inherent chirality of the amide chromophores. The dilactams I and II ((1S,6S)-6-methyl-5,8-diazatricyclo[6,3,0,01,5]undecan-4,9-dione – having five-membered rings) exhibit monosignate amide I VCD and strong VCD bands in the mid-ir region.

scholarly journals A Novel Azaphilone Muyophilone A From the Endophytic Fungus Muyocopron laterale 0307-2

2021 ◽  
Vol 9 ◽  
Author(s):  
Chao Yuan ◽  
Yuhua Guo ◽  
Ke Wang ◽  
Zhunian Wang ◽  
Longfei Li ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Nmr Spectroscopy ◽  
Single Crystal ◽  
Endophytic Fungus ◽  
Vibrational Circular Dichroism ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spectroscopic Analyses ◽  
Circular Dichroïsm

Two known azaphilone derivatives, 4,6-dimethylcurvulinic acid (1) and austdiol (2), and their novel heterotrimer, muyophilone A (3), were isolated and identified from an endophytic fungus, Muyocopron laterale 0307-2. Their structures and stereochemistry were established by extensive spectroscopic analyses including HRMS, NMR spectroscopy, electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectroscopic methods, as well as single crystal X-ray diffraction. In the structure of 3, two compound 2-derived azaphilone units were connected through an unprecedented five-membered carbon bridge which was proposed to be originated from compound 1. Compound 3 represents the first example of azaphilone heterotrimers.

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