Achiral Components Research Articles

Structural phases formed by NO2/CO co-adsorption on Au{111} surfaces

Exposing a Au{111} surface to NO(2) and then to CO at temperatures around 120 K in ultra-high vacuum gives rise to molecular overlayers in which the two species are co-adsorbed, which we have investigated using low-temperature scanning tunnelling microscopy. Under NO(2)-rich conditions, a (√7 × √7)R19.1° phase with 3:1 NO(2):CO stoichiometry forms. Under CO-rich conditions, this phase co-exists with other phases having 2:1 and 1:1 NO(2):CO stoichiometries and different symmetries, and with bare Au surface. Structural models for these phases are discussed. Individual domains of the (√7 × √7)R19.1° phase are chiral, by virtue of the arrangement of their achiral components, an observation that may have more general implications.

2-Hydroxyanilinium 3,5-dinitrobenzoate

In the title molecular salt, C6H8NO+·C7H3N2O6 −, which crystallizes in the chiral monoclinic space group P21, the achiral components assemble by three different N—H⋯O, one O—H⋯O and one C—H⋯O hydrogen bonds into two-stranded chains running parallel to [010]. The dihedral angles between the carboxy group and the two nitro groups and the mean plane of their attached benzene ring are 24.5 (9), 6.1 (6) and 13.0 (1)°, respectively..

A 3D Polar Nanotubular Coordination Polymer with Dynamic Structural Transformation and Ferroelectric and Nonlinear-Optical Properties

A chiral coordination nanotube, [Cd(3)(BPT)(2)(H(2)O)(9)]·2H(2)O (Cd-1; BPT = biphenyl-3,4',5-tricarboxylate), has been synthesized from achiral components and structurally characterized. It consists of homochiral channels based on right-handed helical chains and shows an interdigitated interaction to give a chiral 3D network. The chiral nanotubular framework exhibts dynamic structural transformation upon removal of the guest molecules, and the polarity of this compound induces it to display both ferroelectric and nonlinear-optical properties.

Synthesis and characterization of a zinc metal–organic framework with chiral nano-pores

Zn3(BPDC)2(O2CH)2·2Et2NCHO is a new metal–organic framework with 2,2′-bipyridine-5,5′-dicarboxylate (BPDC) groups as linkers. Although synthesized solvothermally from achiral components, this MOF has a three dimensional (3D) structure with chiral nano-pores. The zinc centers are linked together by carboxylate groups into trinuclear chains; the two terminal zinc atoms are also bound to bipyridine groups.

Chiral transformations of achiral porous metal–organic frameworks via a stepwise approach

A family of chiral porous metal-organic frameworks were synthesized through an unprecedented chiral transformation process only involving achiral components. This method may provide a new point of view to rationally design targeted chiral MOFs and may shed light on the symmetry breaking mechanism.

Stirring competes with chemical induction in chiral selection of soft matter aggregates

Chirality, the absence of mirror symmetry, can be equally invoked in relation to physical forces and chemical induction processes, yet a competition between these two types of influence is rarely reported. Here we present a self-assembled soft matter system in which chiral selection is controlled by the combined independent action of a chiral dopant and vortical stirring, which are arbitrarily coupled, either constructively or destructively. In the latter case, perfect compensation, that is, absence of a net chiral effect, is realized. The induced enantiomorphic excess is measured in terms of the statistical imbalance of an ensemble of submillimetre domains, where achiral molecules self-assemble with a well-defined orientational chirality that is unambiguously resolved using optical microscopy. The possibility of combining top-down and bottom-up strategies to induce a chiral predominance in a supramolecular system of achiral components should be recognized as a new twist in the process of chiral recognition, selection and control.

Hydrogen bond-organized two-fold interpenetrating homochiral pcu net

Integrating enantiopure D-H2Cam ligands into a meso (4,4)-layer of Cu–4-ptz showing alternating orderly arranged right- and left-handed single-stranded 21 helices of achiral components leads to a hydrogen bond-organized three-dimensional two-fold interpenetrating homochiral pcu net.

Chiral single-molecule magnets: a partial Mn(iii) supertetrahedron from achiral components

A [Mn(III)(9)] partial supertetrahedron is a Single-Molecule Magnet (SMM) with an energy barrier to magnetisation reversal of ~30 K and represents the first chiral SMM obtained from achiral starting materials.

Chiral crystalline solids of ammonium-templated ErIII–formate frameworks assembled from three achiral acentric components

The assembly of three simple achiral but acentric building blocks, protonated monoamine AH+, formate HCOO− and Er3+, resulted in a series of chiral crystals of ammonium-templated erbium–formate frameworks with formula [AH+][Er(HCOO)4−], indicating that the increased opportunity to obtain chiral crystalline solids could be achieved by incorporating multiple acentric centers within the lattice.

Sterically demanding benzene-1,3,5-tricarboxamides: tuning the mechanisms of supramolecular polymerization and chiral amplification

Benzene-1,3,5-tricarboxamide (BTA) derivatives with one or three phenylalanine octyl ester (PheOct) moieties were synthesized and their supramolecular polymerization and chiral amplification behavior were investigated in mixing experiments between enantiomer pairs and in mixing with another, achiral BTA component. The incorporation of PheOct moieties is shown to have a major impact on the supramolecular self-assembly.

Homo-chiral self-assemblies and magnetic studies of M(II)-2,2′-bipyridine-4,4′-dicarboxylate coordination polymers

Abstract Homochiral self-assembly is a challenging task, especially from achiral components without any chiral auxiliary. Based on rational selection of achiral organic ligand, two kinds of chiral coordination polymers, {Mn(o1,o2-μ-bpdc)(H2O)2}n (1) and {Ni(o1,o1′-μ-bpdc)(H2O)2}n (2) (bpdc = 2,2′-bipyridine-4,4′-dicarboxylate), have been successfully synthesized by hydrothermal reaction. The X-ray single crystal determination and the structural insight indicate that the coordination behaviors of both bpdc ligands and metal ions between the two kinds of coordination polymers are distinct. Temperature dependent magnetic studies reveal that Mn(II) ions in 1 show antimagnetic interactions, while Ni(II) ions in 2 show weakly ferromagnetic interactions.

A one-dimensional homochiral Mo(iv)-Cu(ii) coordination polymer: spontaneous resolution and photoresponsive properties

A one-dimensional homochiral MoIVCuII compound, [Cu(tren)][Cu(33)][Mo(CN)8]·4H2O (1, tren = tris(2-aminoethyl)amine, 33 = bis(3-aminopropyl)amine), was synthesized and characterized. Compound 1 experiences spontaneous resolution from achiral components and crystallized in a chiral space group P21. It exhibits photomagnetism via photoinduced metal-to-metal charge transfer, making it a novel example of multifunctional molecule-based materials.

Quantitative Surface Chirality Detection with Sum Frequency Generation Vibrational Spectroscopy: Twin Polarization Angle Approach

Here we report a novel twin polarization angle (TPA) approach in the quantitative chirality detection with the surface sum-frequency generation vibrational spectroscopy (SFG-VS). Generally, the achiral contribution dominates the surface SFG-VS signal, and the pure chiral signal is usually two or three orders of magnitude smaller. Therefore, it has been difficult to make quantitative detection and analysis of the chiral contributions to the surface SFG-VS signal. In the TPA method, by varying together the polarization angles of the incoming visible light and the sum frequency signal at fixed s or p polarization of the incoming infrared beam, the polarization dependent SFG signal can give not only direct signature of the chiral contribution in the total SFG-VS signal, but also the accurate measurement of the chiral and achiral components in the surface SFG signal. The general description of the TPA method is presented and the experiment test of the TPA approach is also presented for the SFG-VS from the S- and R-limonene chiral liquid surfaces. The most accurate degree of chiral excess values thus obtained for the 2878 cm1 spectral peak of the S- and R-limonene liquid surfaces are (23.7 0.4)% and (25.4 1.3)%, respectively.

Formation of a Chiral Host with Axially Chiral Cationic 1D Coordination Polymers Composed of Achiral Building Blocks and Inclusion of Anionic Tris-Chelate Complexes in an Unbalanced Δ/Λ Ratio

Abstract Two crystals, [{Co(hfac)2}{Ni(pyterpy)2}][Co(hfac)3]2 (1) and [Co(CNacac)2][Ni(pyterpy)2]SO4·xG (2), composed of 1D cationic coordination polymers were prepared by self-assembly of achiral component metal complexes in solution (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionato, CNacac = 3-cyanopentane-2,4-dionato, pyterpy = 4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine, G = methanol and water). 1 is chiral and spontaneously optically resolved, whereas 2 is achiral. In 1, an alternate linkage of [Co(hfac)2] and [Ni(pyterpy)2]2+ forms a 1D coordination polymer and twisting of the two complexes about the principal axis of the 1D polymer makes the polymer axially chiral. The 1D polymers stack to create two-types of 1D channels, where anionic complexes [Co(hfac)3]− are included. One channel contains only Δ-[Co(hfac)3]−, whereas the other contains an equal amount of Δ- and Λ-[Co(hfac)3]−. Therefore, the Δ/Λ ratio of [Co(hfac)3]− is 3/1. In the case of 2, 1D coordination polymers are formed by an alternate linkage of [Co(CNacac)2] and [Ni(pyterpy)2]2+. They are chiral due to twisting of one pyridine ring in [Ni(pyterpy)2]2+, however, there are inversion centers in 2. These results demonstrated that axial chirality can be introduced into 1D coordination polymers by twisting the two component metal complexes alternately linked. This method is useful and prospective for preparing chiral coordination polymers from achiral building blocks.

Solid‐State Chiral Supramolecular Organic Fluorophore Having a π‐Conjugated Phenylene Ethynylene Unit

AbstractA solid‐state, chiral, helical, columnar, organic fluorophore having a π‐conjugated phenylene ethynylene unit was prepared by using 4‐[2‐(4‐methylphenyl)ethynyl]benzoic acid and 1‐phenylethylamine. Such a chiral π‐conjugated organic fluorophore can be obtained from achiral and racemic component molecules, and it exhibits circularly polarized luminescence (CPL) in the solid state.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Constitutional self-sorting of homochiral supramolecular helical single crystals from achiral components

Double-helical architectures obtained from achiral ligands and metal ions present supramolecular homochirality in the single -crystal state under constitutional self-sorting.

Absolute helicity induction in three-dimensional homochiral frameworks.

Three Co(II) isomers assembled from D-, or L-, or DL-camphorate together with achiral isonicotinate exhibit a clear relationship between chirality and helicity even though chiral molecules are not in the backbone of the helix: the absolute sense of helix made of achiral components is controlled by chains of metal and enantiopure chiral ligands running perpendicular to helix in two enantiomeric forms.

Syntheses and Crystal Structures of a Series of Novel Helical Coordination Polymers Constructed from Flexible Bis(imidazole) Ligands and Metal Salts

This paper reports eight novel one-dimensional (1D) helical chain polymers consisting of metal salts and flexible bis(imidazole) ligands, formulated as [Co(L1)2(bimb)] (1), [Cu2(bimb)2Cl2] (2), [Co(L2)2(bimb)] (3), [Co(L3)(bix)Cl] (4), [Co(L4)2(bix)] (5), [Co(L5)2(bimb)] (6), [Ni(L6)2(bimb)] (7), and [Ni(L7)2(bimb)] (8) (bimb = 1,4-bis(imidazol-1-yl)-butane, bix = 1,4-bis(imidazol-1-yl-methylene)-benzene, HL1 = 3,5-dinitrobenzoic acid, HL2 = 4-methoxylbenzoic acid, HL3 = benzoic acid, HL4 = 4-methylbenzoic acid, HL5 = 3-nitrobenzoic acid, HL6 = 4-nitrobenzoic acid and HL7 = 4-chlorobenzoic acid), which have been obtained via hydrothermal reaction and characterized by single-crystal X-ray diffraction, elemental analysis, IR and thermogravimetric analyses. 1 consists of chiral polymer chains assembled from achiral components due to the presence of left-handed helices. 2 is a very unusual racemic compound based on perpendicular left- and right-handed helical chains. 3 contains two distinct types of helical chains, one with an almost flat, zigzag type geometry and the other showing a distinct tubular motif. 4 is also a racemic compound with tubes larger than those in 3. 5−8 show rare meso-helical structures. This series of complexes provides new examples of 1D infinite helical structures for flexible bis(imidazole) ligands.

Effects of the size of aromatic chelate ligands and d 10 metal ions on the structures of dicarboxylate complexes: From dinuclear molecule to helical chains and 2D network

Four new mixed-ligand complexes, namely [Zn 2(pam) 2(2,2′-bpy) 2] ( 1), [Cd(pam)(2,2′-bpy) 2] n ( 2), [Zn(pam)(phen)] n ( 3) and [Cd (pam)(phen)] n · 0.5 n CH 3CH 2OH · 0.5 nH 2O ( 4) (H 2pam = pamoic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been synthesized under hydro(solvo)thermal conditions. Complex 1 possesses a discrete dinuclear metallamacrocyclic structure. Complex 2 is a 1D homochiral helical coordination polymer that is built from achiral components, whereas 3 displays a 1D helical chain structure. 4 is an unusual 2D double-layered structure generated by π ⋯ π interactions of two 2D networks. The structural differences of these complexes are mainly due to the differences of the size of the rigid aromatic chelate ligands and d 10 metal ions. It appears that the chelate ligands and metal ions of the larger size favor the formation of high-dimensional structures, whereas those of the smaller size favor the formation of low-dimensional structures in the present system. The photoluminescence and thermal stability of these complexes were investigated.

Control of circularly polarized luminescence (CPL) properties by supramolecular complexation

The sign of circularly polarized luminescence (CPL) of a chiral 21-helical columnar organic fluorophore was successfully controlled in the solid-state by changing an achiral fluorescence component molecule, and not by using a chiral component molecule with opposite chirality.