Chiral Coordination Research Articles

Chiral Assembly and Recognition of Seven Copper (II) Coordination Polymers from Tartaric Acid Derivative Ligands.

A pair of enantiomeric ligands, (2R,3R)-dibenzyl-2,3-bis(isonicotinoyloxy)succinate ((R,R)-L) and (2S,3S)-dibenzyl-2,3-bis(isonicotinoyloxy)succinate ((S,S)-L), are designed and synthesized. Seven copper (II) coordination polymers {[Cu((R,R)-L)Br2 (THF)] ⋅ CH3 CN} n (1 a) and {[Cu((S,S)-L)Br2 (THF)] ⋅ CH3 CN}n (1 b), {[Cu((R,R)-L)Cl2 (THF)] ⋅ CH3 CN}n (2 a) and {[Cu((S,S)-L)Cl2 (THF)] ⋅ CH3 CN}n (2 b), {[Cu((R,R)-L)(NO3 )2 (CH3 CN)]}n (3 a) and {[Cu((S,S)-L)(NO3 )2 (CH3 CN)]}n (3 b), {[Cu((R,R)-L)2 (CH3 CN)2 ](ClO4 )2 ⋅ 3CH3 CN}n (4) were obtained through the assemblies with CuBr2 , CuCl2 ⋅ 2H2 O, Cu(NO3 )2 ⋅ 3H2 O, Cu(ClO4 )2 ⋅ 6H2 O, respectively. Single-crystal X-ray diffraction and circular dichroism analysis demonstrate that 1 a-3 a, 1 b-3 b have a mono chiral one-dimensional (1D) chain-like spiral structure, while 4 have 1D chain-like structure whose metal centers have chiral propeller coordination environment. Ligand structure, anions and solvent systems have a regulatory effect on the formation of chiral helical structure. Further investigation has proved that 1 a can be used as circular dichroism spectrum probe for monitoring L-/D-cysteine and L-/D-penicillamine configuration and concentration in aqueous media based on ligand interchange mechanism.

White‐Light Emission and Circularly Polarized Luminescence from a Chiral Copper(I) Coordination Polymer through Symmetry‐Breaking Crystallization

AbstractAchieving white‐light emission, especially white circularly polarized luminescence (CPL) from a single‐phase material is challenging. Herein, a pair of chiral CuI coordination polymers (1‐M and 1‐P) have been prepared by the asymmetrical assembly of achiral ligands and Cu2I2 clusters. The compounds display dual emission bands and can be used as single‐phase white‐light phosphors, achieving a “warm”‐white‐light‐emitting diode with an ultra‐high color rendering index (CRI) of 93.4 and an appropriate correlated color temperature (CCT) of 3632 K. Meanwhile, corresponding CPL signals with maximum dissymmetry factor |glum|=8×10−3 have been observed. Hence, intrinsic white‐light emission and CPL have been realized simultaneously in coordination polymers for the first time. This work gains insight into the nature of chiral assembly from achiral units and offers a prospect for the development of single‐phase white‐CPL materials.

White-Light Emission and Circularly Polarized Luminescence from a Chiral Copper(I) Coordination Polymer through Symmetry-Breaking Crystallization.

Achieving white-light emission, especially white circularly polarized luminescence (CPL) from a single-phase material is challenging. Herein, a pair of chiral CuI coordination polymers (1-M and 1-P) have been prepared by the asymmetrical assembly of achiral ligands and Cu2 I2 clusters. The compounds display dual emission bands and can be used as single-phase white-light phosphors, achieving a "warm"-white-light-emitting diode with an ultra-high color rendering index (CRI) of 93.4 and an appropriate correlated color temperature (CCT) of 3632 K. Meanwhile, corresponding CPL signals with maximum dissymmetry factor |glum |=8×10-3 have been observed. Hence, intrinsic white-light emission and CPL have been realized simultaneously in coordination polymers for the first time. This work gains insight into the nature of chiral assembly from achiral units and offers a prospect for the development of single-phase white-CPL materials.

A structural study into halogenated derivatives of mandelic acid as building blocks of chiral coordination polymers

Mandelic acid and its derivatives are an excellent source of chirality for the construction of chiral coordination polymers (CPs) and metal-organic frameworks (MOFs) for enantioselective applications. To date, limited reports exist for the incorporation of mandelic acid derivatives with halogen substituents such as fluorine and chlorine despite the extra intermolecular interactions possible. The extra sites for hydrogen and halogen bonding in these mandelic acid derivatives may afford interesting modes of coordination and packing in 3 D space. Six CPs containing mandelic acid and its halogenated analogues, (R)-2-chloromandelic acid, 3,5-difluoromandelic acid, 4-trifluoromethylmandelic acid, together with linear dipyridyl co-ligands are reported. These structures consist of three 2 D sql sheets and three 1 D chains with a range of packing motifs influenced by the differing intermolecular interactions present.

A chiral binaphthyl-based coordination polymer as an enantioselective fluorescence sensor.

A fluorescent, chiral coordination polymer (CP) with a novel topology has been synthesised using a dipyridyl ligand derived from 1,1'-bi-2-naphthol (BINOL). Enantioselectivity ratios up to 2.61 were obtained in fluorescence sensing studies with chiral analytes.

Chiral coordination compounds with exceptional enantioselectivity

The new homochiral Zn-based coordination compounds reveal excellent enantioselective sensing behavior toward d- and l-histidine attributed to the host–guest interactions through the rigid chiral backbones.

Multicolor-tunable room-temperature afterglow and circularly polarized luminescence in chirality-induced coordination assemblies.

Dynamic long-lived multicolor room temperature afterglow and circularly polarized luminescence (CPL) are promising for optoelectronic applications, but integration of these functions into a single-phase chiroptical material is still a difficult and meaningful challenge. Here, a nitrogen-doped benzimidazole molecule 1H-1,2,3-triazolopyridine (Trzpy) showing pure organic room-temperature phosphorescence (RTP) acted as a linker, and then, we propose a chirality-induced coordination assembly strategy to prepare homochiral crystal materials. Two homochiral coordination polymers DCF-10 and LCF-10 not only exhibit multicolor-tunable RTP, the color changed from green to orange under various excitation wavelengths, but also show remarkable excitation-dependent circularly polarized luminescence (CPL), and the dissymmetry factors of CPL in DCF-10 and LCF-10 are 1.8 × 10-3 and 2.4 × 10-3, respectively. Experimental and theoretical studies demonstrated that molecular atmospheres with different aggregation degrees give rise to multiple emission centers for the generation of multicolor-tunable emission. The multicolor-tunable photophysical properties endowed LCF-10 with a huge advantage for multi-level anti-counterfeiting. This work opens up new perspectives for the development and application of color-tunable RTP and CPL.

Structural Diversities of a Series of Cd(II) Coordination Complexes Based on a Flexible Tripodal N-donor Ligand

Three Cd(II) coordination complexes with unique structures and topologies, namely, {[Cd(tttmb)(Hbtc)]·5H2O}n (1), {[Cd(tttmb)(m-phda)(H2O)]·2H2O}n (2), and {[Cd(tttmb)(o-cpla)]·(CH3CN)·(H2O)1.5}n (3), have been successfully synthesized under hydro(solvo)thermally condition based on a flexible tripodal N-contained ligand 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (tttmb) and aromatic polycarboxylate acids (H3btc = 1,2,4-benzenetricarboxylic acid, m-H2phda = 1,3-phenylenediacetic acid and o-H2cpla = Homophthalic acid). Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray single-crystal diffraction and thermogravimetric analyses. 1 crystallize in the orthorhombic chiral space group P212121 and feature 3D coordination networks. 2 reveals a 2D ladder-like structure with (4,4) topology containing alternating Cd(II)/m-phda2− left- and right-handed helical motifs. 3 exhibits a 3D net with (63)(66)(7·82) topology. The structural and dimensional diversity of these complexes not only indicates that the flexible ligand tttmb exhibits strong coordination ability and diverse coordination modes, but also shows that aromatic polycarboxylates play important roles in constructing the frameworks of complexes. Moreover, the different photoluminescence behaviors of 1–3 have been studied in the solid state.

Whither Second-Sphere Coordination?

Whither Second-Sphere Coordination?

Anions mediated amino-type Cd-MOFs catalysts for efficient photocatalytic hydrogen evolution

Photocatalytic water splitting can be used to directly transfer solar energy into chemical energy with highly efficiency. Metal-organic frameworks (MOFs) materials are well known on the advantages of high design flexibility and metal center functionalization. In this study, a series of Cd-centered MOFs were successfully fabricated by a simple solvent evaporation method based on the different anion mediated pyridyl leucine derivatives. Single-crystal X-Ray diffraction showed the isostructural 3D chiral coordination networks of three Cd-MOFs with helical chains connected by the adjacent carboxylate groups. Within the helical coordination chains, the formate (For) and acetate (OAc) anions adopted chelate modes in Cd-LFor and Cd-LOAc, whereas the chloride worked as a monodetate ligand in Cd-LCl. Powder X-ray diffraction (PXRD), Thermogravimetric analysis, UV–vis spectra, Photocurrent-time test (I-t) and Mott-Schottky (MS) curves were carried out to characterize and analysis these Cd-MOFs. All the samples exhibit photocatalytic activity for hydrogen generation in aqueous solution of Na2S/Na2SO3 upon irradiation at full light. The photocurrent time test showed that Cd-LCl showed a higher photocurrent intensity than those of Cd-LFor and Cd-LOAc, which proved the lower electron-hole recombination and correspondingly higher hydrogen production photocatalysis active. The highest H2 production rate reached 17242 ​μmol ​g−1 ​h−1 for Cd-LCl. In the photocatalytic reaction, the hydrogen production rate was stable without significant decrease, indicating that the material had no significant deactivation and had good photocatalytic activity.

Chiral Coordination Metallacycles/Metallacages for Enantioselective Recognition and Separation

AbstractIn recent years, chiral discrete supramolecular coordination complexes have attracted increasing interest as simple enzyme mimetics owing to their aesthetic architectures and potential applications in chiral science. This review summarizes the recent advances on chiral coordination metallacycles/metallacages with inherent cavities for enantionselective recognition and separation, including their design principles and synthesis, the introduction of chirality and functionality, structural adaptability, and host‐guest bonding in enantioselective process. Finally, the perspectives on the remaining challenges and future opportunities are presented.

Hydrogen-Bond-Driven Synergistically Enhanced Hyperpolarizability: Chiral Coordination Polymers with Nonpolar Structures Exhibiting Unusually Strong Second-Harmonic Generation.

Four chiral coordination polymers (CPs), M[(S,S)-C14 H14 N2 O6 ] and M[(R,R)-C14 H14 N2 O6 ] (M=Zn or Cd), have been exclusively synthesized in high yields with the aid of newly designed chiral ligand under hydrothermal condition. The CPs crystallizing in the orthorhombic nonpolar space group, C2221 , reveal three-dimensional framework structures composed of MO4 tetrahedra and the corresponding homochiral linkers. Powder second-harmonic generation (SHG) measurements indicate that the nonpolar CPs reveal very strong SHG efficiency of ca. 5-9 times that of KH2 PO4 and exhibit type-I phase-matching behavior. Density functional theory calculations suggest that the unusually large SHG efficiency found from the nonpolar CPs should be attributable to the synergistic effect of polarizable metal cations and enhanced hyperpolarizability in the donor-acceptor system originating from the hydrogen bonding in the coordinated linkers.

Hydrogen‐Bond‐Driven Synergistically Enhanced Hyperpolarizability: Chiral Coordination Polymers with Nonpolar Structures Exhibiting Unusually Strong Second‐Harmonic Generation

AbstractFour chiral coordination polymers (CPs), M[(S,S)‐C14H14N2O6] and M[(R,R)‐C14H14N2O6] (M=Zn or Cd), have been exclusively synthesized in high yields with the aid of newly designed chiral ligand under hydrothermal condition. The CPs crystallizing in the orthorhombic nonpolar space group, C2221, reveal three‐dimensional framework structures composed of MO4 tetrahedra and the corresponding homochiral linkers. Powder second‐harmonic generation (SHG) measurements indicate that the nonpolar CPs reveal very strong SHG efficiency of ca. 5–9 times that of KH2PO4 and exhibit type‐I phase‐matching behavior. Density functional theory calculations suggest that the unusually large SHG efficiency found from the nonpolar CPs should be attributable to the synergistic effect of polarizable metal cations and enhanced hyperpolarizability in the donor‐acceptor system originating from the hydrogen bonding in the coordinated linkers.

Innentitelbild: Hydrogen‐Bond‐Driven Synergistically Enhanced Hyperpolarizability: Chiral Coordination Polymers with Nonpolar Structures Exhibiting Unusually Strong Second‐Harmonic Generation (Angew. Chem. 38/2021)

Systematisch synthetisierte nicht-zentrosymmetrische, unpolare, chirale Koordinationspolymere zeigen eine ungewöhnlich effiziente Obertonbildung, was auf den synergistischen Effekt der polarisierbaren Metallkationen und die erhöhte Hyperpolarisierbarkeit im Donor-Akzeptor-System zurückzuführen ist, die von den robusten Wasserstoffbrücken in den koordinierten Linkern herrühren. Details finden sich in der Zuschrift von Joonhyuk Kee und Kang Min Ok auf S. 20824.

Inside Cover: Hydrogen‐Bond‐Driven Synergistically Enhanced Hyperpolarizability: Chiral Coordination Polymers with Nonpolar Structures Exhibiting Unusually Strong Second‐Harmonic Generation (Angew. Chem. Int. Ed. 38/2021)

Systematically synthesized new noncentrosymmetric nonpolar chiral coordination polymers exhibit unusually strong second-harmonic generation efficiencies attributable to the synergistic effect of polarizable metal cations and increased hyperpolarizability in the donor–acceptor system originating from the robust hydrogen bonding in the coordinated linkers. Details can be found in the Communication by Joonhyuk Kee and Kang Min Ok on page 20656.

Synthesis and the crystal structure of a new chiral metal-organic coordination polymer based on l-proline-substituted 2-aminobenzene-1,4-dicarboxylic acid derivative

Synthesis and the crystal structure of a new chiral metal-organic coordination polymer based on l-proline-substituted 2-aminobenzene-1,4-dicarboxylic acid derivative

Chiral Detection with Coordination Polymers

Coordination polymers and metal-organic frameworks are prime candidates for general chemical sensing, but the use of these porous materials as chiral probes is still an emerging field. In the last decade, they have found application in a range of chiral analysis methods, including liquid- and gas-phase chromatography, circular dichroism spectroscopy, fluorescence sensing, and NMR spectroscopy. In this minireview, we examine recent works on coordination polymers as chiral sensors and their enantioselective host-guest chemistry, while highlighting their potential for application in different settings.

Synthetic strategies towards chiral coordination polymers

• Chiral coordination polymers can be synthesised via direct or indirect methods. • Indirect methods include spontaneous resolution, chiral templating and induction. • Ligands with point chirality can be derived from various chiral pool molecules. • Other coordination polymers are built from ligands with axial or planar chirality. • Post-synthetic modification can be used to impart or unveil chirality in frameworks. Chiral coordination polymers and porous chiral MOFs have great potential as agents for enantioselective separations, sensing, and catalysis due to their well-structured internal chiral cavities. They also have physical properties that may be exploited, such as non-linear optical activity, ferroelectrics, magnetochiral dichroism, and use as chemical shift reagents. There are many ways in which chiral coordination polymers can be synthesised and the file has grown tremendously over the past two decades. In this review, we will discuss some of the main synthetic approaches that have been taken towards this fascinating class of materials. The main focus will be placed on synthetic approaches using enantiopure ligands, the route that is most likely to yield homochiral network solids. We will highlight the applications of many examples, noting how the design of the frameworks influences their application. Whilst this is a mature field, there still lies huge potential for functional chiral materials, and we aim to demonstrate areas that are ripe for exploration.

Crystal structures of three copper(II)-2,2'-bi-pyridine (bpy) compounds, [Cu(bpy)2(H2O)][SiF6]·4H2O, [Cu(bpy)2(TaF6)2] and [Cu(bpy)3][TaF6]2 and a related coordination polymer, [Cu(bpy)(H2O)2SnF6] n.

We report the hydro-thermal syntheses and crystal structures of aqua-bis-(2,2'-bi-pyridine-κ2 N,N')copper(II) hexa-fluorido-silicate tetra-hydrate, [Cu(bpy)2(H2O)][SiF6]·4H2O (bpy is 2,2'-bi-pyridine, C10H8N2), (I), bis-(2,2'-bi-pyridine-3κ2 N,N')-di-μ-fluorido-1:3κ2 F:F;2:3κ2 F:F-deca-fluorido-1κ5 F,2κ5 F-ditantalum(V)copper(II), [Cu(bpy)2(TaF6)2], (II), tris-(2,2'-bi-pyridine-κ2 N,N')copper(II) bis[hexa-fluorido-tantalate(V)], [Cu(bpy)3][TaF6]2, (III), and catena-poly[[di-aqua-(2,2'-bi-pyridine-κ2 N,N')copper(II)]-μ-fluorido-tetra-fluorido-tin-μ-fluorido], [Cu(bpy)(H2O)2SnF6] n , (IV). Compounds (I), (II) and (III) contain locally chiral copper coordination complexes with C 2, D 2, and D 3 symmetry, respectively. The extended structures of (I) and (IV) are consolidated by O-H⋯F and O-H⋯O hydrogen bonds. The structure of (III) was found to be a merohedral (racemic) twin.

Synthesis of a rod-based porous coordination polymer from a nucleotide as a sequential chiral inductor

We report the two-step synthesis of a novel chiral rod-based porous coordination polymer (PCP). The chemical approach consists of the use of a previously prepared bis(ethylenediamine) copper monomer [Cu(en)]2(NO3)2 [where en = ethylenediamine] reacting with the cytidine 5′-monophosphate (CMP) nucleotide. The bis(ethylenediamine) copper compound—stabilized by axial coordination of nitrate counter-anions—reacts in the presence of sodium salt of CMP to yield right-handed copper(II) chains of P helicity with formula [Cu2(en)2(CMP)2]·5H2O (1). The axial coordination of the CMP2- ligands through the N3 and O2 sites (free nitrogen and carbonyl groups) of the cytosine nucleobase and oxygen atoms of phosphate moieties, ensure stabilization of the neutral chiral polymer. The supramolecular organization involves strong hydrogen bonding interactions to build supramolecular chains of the same helicity. The resulting PCP constitutes one of the few examples of CMP compounds exhibiting coordination involving both nucleobase and phosphate moieties, where a highly stable metal complex is used as precursor for the rational construction of rod-based hydrogen metal-organic frameworks (HMOFs). Furthermore, it shows the intrinsic capability of biomolecules to act as chiral transfer systems.