Chiral resolution of l- and d-alanine and a racemic macrocyclic nickel(II) complex: synthesis and crystal structures
01 Mar 2014-Transition Metal Chemistry (Springer International Publishing)-Vol. 39, Iss: 2, pp 135-140
TL;DR: In this paper, the reaction of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two sixcoordinate enantiomers formulated as Ni(RR-L)(l-Ala) and ClO4·2CH3CN, respectively.
Abstract: The reactions of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two six-coordinate enantiomers formulated as [Ni(RR-L)(l-Ala)](ClO4)·2CH3CN (1) and [Ni(SS-L)(d-Ala)](ClO4) (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane, Ala− = alanine anion), respectively. Evaporation from the remaining solutions gave two four-coordinate enantiomers characterized as [Ni(SS-L)](ClO4)2 (S-3) and [Ni(RR-L)](ClO4)2 (R-3), respectively. Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni(II) atom has a distorted octahedral coordination geometry, being coordinated by four nitrogen atoms of L in a folded configuration, plus one carboxylate oxygen atom and one nitrogen atom of l- or d-Ala− in mutually cis-positions. Complexes 1 and 2 are supramolecular stereoisomers, constructed via hydrogen bonding between [Ni(RR-L)(l-Ala)]+ or [Ni(SS-L)(d-Ala)]+ monomers to form 1D hydrogen-bonded zigzag chains. The homochiral natures of complexes 1 and 2 have been confirmed by CD spectroscopy.
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01 Jan 2017
TL;DR: In this article, 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral neighbors with 6-amino-6-deoxy-β-cyclodesyntextrin (am-β -CD) in water at 298 K.
Abstract: We report new 3D fragment descriptors to model parameters and properties of stereoisomeric molecules and conformers. New 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral guests with 6-amino-6-deoxy-β-cyclodextrin (am-β-CD) in water at 298 K. The in-house software, mfSpace (Molecular Fragments Space), was used for QSPR modeling, generation and coding of the 3D fragment descriptors. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method. We used ensemble modeling techniques which include the generation of many individual models, the selection of the most relevant ones and followed by their joint application to test compounds, i.e., applying a consensus model for average predictions. The models based on 2D and 3D fragment descriptors provide the best predictions in external fivefold cross-validation: root mean squared error RMSE = 1.1 kJ/mol and determination coefficient $$R_{{det}}^{2}$$Rdet2 = 0.918 (β-CD), RMSE = 0.89 kJ/mol and $$R_{{det}}^{2}$$Rdet2 = 0.910 (am-β-CD).
5 citations
Cites background from "Chiral resolution of l- and d-alani..."
...l-alanine [55] has the fragment C–C–C=O_abC, when d-alanine [55] possesses the fragment C–C–C=O_abA, and cis- and trans-β-butylene have the fragments C–C=C–C_bbA and C–C=C–C_bbD, respectively....
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TL;DR: In this paper, 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral neighbors with 6-amino-6-deoxy-β-cyclodesyntextrin (am-β -CD) in water at 298 K. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method
Abstract: We report new 3D fragment descriptors to model parameters and properties of stereoisomeric molecules and conformers. New 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral guests with 6-amino-6-deoxy-β-cyclodextrin (am-β-CD) in water at 298 K. The in-house software, mfSpace (Molecular Fragments Space), was used for QSPR modeling, generation and coding of the 3D fragment descriptors. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method. We used ensemble modeling techniques which include the generation of many individual models, the selection of the most relevant ones and followed by their joint application to test compounds, i.e., applying a consensus model for average predictions. The models based on 2D and 3D fragment descriptors provide the best predictions in external fivefold cross-validation: root mean squared error RMSE = 1.1 kJ/mol and determination coefficient $$R_{{det}}^{2}$$
= 0.918 (β-CD), RMSE = 0.89 kJ/mol and $$R_{{det}}^{2}$$
= 0.910 (am-β-CD).
4 citations
TL;DR: In this paper, three enantiomeric pairs of novel homochiral coordination compounds (HCCs) with the formula {[Zn(D-hpg)(4,4′-bipy)(H2O)] · (NO3)}n 1-L, {Zn (Lhpg)2(4, 4′-Bipy)
2 citations
TL;DR: In this article, the macrocyclic nickel(II) complexes can easily take up and fix atmospheric CO2 at room temperature, and the chiral nature of complex 2 has been confirmed by CD spectroscopy.
Abstract: Two dinuclear carbonato-bridged nickel(II) complexes formulated as [Ni(rac-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (1) and [Ni(SS-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, im = imidazole) were isolated from the reactions of [Ni(rac-L)](ClO4)2 and [Ni(SS-L)](ClO4)2 with imidazole in the air, respectively, and a hydrocarbonato-coordinated nickel(II) complex formulated as [Ni(rac-L)](HCO3)(ClO4) (3) was reacted with obtained when [Ni(rac-L)](ClO4)2 reacted with l-cysteine under weakly basic conditions in the air. We found that the macrocyclic nickel(II) complexes can easily take up and fix atmospheric CO2 at room temperature. Single-crystal X-ray diffraction analyses revealed of all three complexes that the central Ni(II) atoms all have a six-coordinated distorted octahedral coordination geometry, and the carbonate anion bridges two Ni(II) atoms in a tridentate fashion to form dimers in complexes 1 and 2, and the hydrocarbonate coordinates with Ni(II) in a didentate fashion in complex 3. The monomers of {[Ni(RR-L)]2(µ-CO3)(H2O)}2+/{[Ni(SS-L)]2(µ-CO3)(H2O)}2+ are connected through hydrogen bonds to generate one-dimensional right- and left-handed helical chains in complex 1. The chiral nature of complex 2 has been confirmed by CD spectroscopy.
1 citations
References
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TL;DR: In this article, the phase transition of grafted PNIPAM chains affects the micro-environment of β-cyclodextrin (β-CD) molecules and then the association between β-CD and guest molecules.
Abstract: In this chapter, the design, fabrication and performance of thermo-responsive membranes for chiral resolution with a high performance are introduced. The membrane is designed with both chiral selectivity based on molecular recognition of beta-cyclodextrin (β-CD) and thermo-sensitivity based on phase transition of PNIPAM. Linear PNIPAM chains are grafted onto porous Nylon6 membrane substrates by using the plasma-graft pore-filling polymerization method, acting as micro-environmental adjustors for β-CD molecules. β-CD moieties are introduced into the linear PNIPAM chains by the chemical grafting polymerization method, acting as chiral selectors. The phase transition of grafted PNIPAM chains affects the micro-environment of β-CD molecules and then the association between β-CD and guest molecules. The chiral selectivity of the prepared thermo-responsive membranes in chiral resolution operated at a temperature below the LCST of PNIPAM is higher than that of membranes with no thermo-sensitivity, while the decomplexation ratio of enantiomer-loaded thermo-responsive membranes in decomplexation operated at a temperature above the LCST is much higher than that of membranes with no thermo-sensitivity. By simply changing the operating temperature, high selective chiral resolution and efficient membrane regeneration can be achieved.
82 citations
TL;DR: Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described and it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli.
Abstract: Buckling-induced reversible symmetry breaking and amplification of chirality using macro- and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli.
81 citations
TL;DR: The data demonstrate that sublimation of serine under relatively mild conditions yields chirally enriched serine octamers and that the chiral preference of the starting serine can be transferred to other compounds through cluster-forming chemical reactions.
Abstract: Spontaneous assembly of amino acids into vapor-phase clusters occurs on heating the solid compounds in air. In comparison to the other amino acids, serine forms clusters to an unusual extent, showing a magic number octamer on sublimation; this octamer can be ionized and characterized by mass spectrometry. Two isomers of the vapor-phase serine octamer are generated, the minor one at 130 °C and the major at 220 °C. The higher temperature cluster shows a strong homochiral preference, as confirmed by isotopic labeling experiments. This serine cluster, like that generated earlier from solution in electrospray ionization experiments, undergoes gas-phase enantioselective substitution reactions with other amino acids. These reactions transfer the chirality of serine to the other amino acid through enantioselective incorporation into the octamer. Other serine pyrolysis products include alanine, glycine, ethanolamine, and small dipeptides, and many of these, too, are observed to be incorporated into the thermally f...
61 citations
TL;DR: The reactions of a racemic four-coordinated nickel(II) complex with l- and d-phenylalanine in acetonitrile/water gave two less-soluble six-coordination enantiomers of Delta-1 and Lambda-1, which shows a motif of a 1D hydrogen bonded zigzag chain instead of a1D helical chain.
Abstract: The reactions of a racemic four-coordinated nickel(II) complex [Ni(α-rac-L)](ClO4)2 (containing equal amount of SS and RR enantiomers) with l- and d-phenylalanine in acetonitrile/water gave two less-soluble six-coordinated enantiomers of {[Ni(f-SS-L)(l-Phe)](ClO4)}n (Δ-1) and {[Ni(f-RR-L)(d-Phe)](ClO4)}n (Λ-1), respectively. Evaporation the remaining solutions gave two six-coordinated diastereomers of {[Ni3(f-RR-L)3(l-Phe)2(H2O)](ClO4)4}n (a-2) and {[Ni3(f-SS-L)3(d-Phe)2(H2O)](ClO4)4}n (b-2), respectively (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, Phe− = phenylalanine anion). The reaction of [Ni(α-rac-L)](ClO4)2 with dl-Phe− gave a conglomerate of c-1; in which, the SS and RR enantiomers preferentially coordinate to l- and d-Phe− respectively to give a racemic mixture of Δ-1 and Λ-1, and the spontaneous resolution occurs during the reaction, in which each crystal crystallizes to become enantiopure. Removing Phe− from Δ-1 and Λ-1 using perchloric acid gave two enantiomers of [Ni(α-SS...
60 citations
50 citations