Left-handed Helical Chains Research Articles

Homochiral coordination polymers of Zn(II) and Pb(II) with interesting three-dimensional helicates

Based on a designed enantiomerically pure chiral ligand H3L, two interesting homochiral metal−organic frameworks (HMOFs), namely {[Zn3(L)2(H2O)2]∙2H2O}n (1) and {[Pb(HL)(H2O)]∙H2O}n (2), have been solvothermally synthesized (H3L = (S)-4'-(((1-carboxyethyl)amino)methyl)-[1,1′-biphenyl]-3,5-dicarboxylic acid). Complexes 1 and 2 are novel three-dimensional metal−organic helicates with different structural motifs. In 1, anionic (L)3− ligands bridge trimetallic Zn-clusters to form a [3,6]-connected architecture of (63)2(612·83) topology. In particular, each trimetallic Zn-cluster is the node of six strand 21 helical chains consisting of four right-handed helical chains and two left-handed helical chains. In 2, zwitterionic (HL)2− ligands link PbII ions into a 3-connected 103-topological helicate composed of 21 helical chains extending along three crystal axes, and two thirds of which are left-handed. Interesting enough, the chiral ligand H3L not only transferred its inherent chirality to the synthesized complexes 1 and 2, but also induced unexpected helical chirality. Furthermore, the morphologies, thermal stabilities and solid-state optical properties including CD spectra, and nonlinear optical and luminescent properties of compounds 1 and 2 were also carried out. Compounds 1 and 2 exhibit interesting fluorescence emissions and obvious second-order nonlinear activity in addition to the excellent thermal stability of their dehydrated frameworks, indicating that the HMOF materials have great potential in optical devices.

Template synthesis, characterization and antibacterial activity of d10 (Zn2+, Cd2+, Hg2+) Schiff base complexes: A novel supramolecular Cd2+ complex with two 1D helical chains, and its Hirshfeld surface analysis

Three new macroacyclic Schiff base complexes were prepared via condensation of N,N,N',N'-tetrakis(2-aminoethyl) ethylenediamine hydrobromide with 5-bromo salicylaldehyde in the presence of metal ions (Zn2+, Cd2+, Hg2+) as template agents. The compounds were studied with elemental analysis, FT-IR, and 1H, 13C NMR spectroscopy. The structure of the Cd(II) complex, [Cd(H2L)] .2H2O (1), (H4L = N,N,N',N'-tetrakis(5-bromo salicylidene) N,N,N',N'-tetrakis(2-aminoethyl) ethylenediamine), was determined by single crystal X-ray crystallography. The X-ray diffraction analysis revealed that 1 crystallizes in monoclinic space group P21/c. Intermolecular O–H⋯O and C–H⋯Br hydrogen bonds linked [Cd(H2L)] monomers to a 2D network structure along the ac plane. The Br⋯Br halogen bonding interactions further expand the structure and construct a 3D supramolecular network with 1D right-handed and left-handed helical chains along the b axis in a 1:1 ratio. Furthermore, 1 is self-assembled through hydrogen bonding between the lattice water molecules with the phenolic oxygen atoms and phenolato oxygen atoms to form a 1D helical chain perpendicular to bc plane. The impact of the intermolecular contacts on the crystal packing of 1 has been further studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Antibacterial activities of the compounds were screened by the disc diffusion method against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 23212 and S. epidermidis ATCC 34384), and three Gram-negative bacteria (Eschericha coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumonia ATCC 70063). All compounds demonstrated good antibacterial activities, and in three cases, the antibacterial activity of the Hg(II) complex exceeded the one of sulfisoxazole used as a standard.

A new chiral rare-earth organic framework constructed by tartaric acid: synthesis, structural, thermal investigations and optical properties.

Hydrothermal reactions of rare-earth cerium with L-tartaric acid afford a new coordination polymer, namely, poly[[triaqua(μ4-L-tartrato)cerium(III)] chloride], {[Ce(C4H4O6)(H2O)3]Cl}n, (1). The structure was determined by single-crystal X-ray diffraction analysis and further characterized by IR and UV-Vis spectroscopy, powder X-ray diffraction and thermogravimetric analysis. Single-crystal X-ray diffraction analysis revealed that the compound is a new two-dimensional (2D) double-layered structure with one-dimensional left-handed helical chains. The different intermolecular interactions were confirmed using Hirshfeld surface analysis and molecular fingerprint plots. Molecular 2D fingerprint plots quantify the different interactions and highlight that H...H (24.8%), H...O/O...H (26.3%), Cl...H/H...Cl (19.6%), O...O (13.8%) and Ce...O/O...Ce (13.6%) interactions account for 99.8% of all contacts. Additionally, the photoluminescence properties of the compound were investigated in the solid state.

Homochiral coordination polymers based on proline-derivative: structures, magnetic properties, and selective detection of Cr2O72− anion

By incorporating semi-rigid terephthaloyl mono proline-derived ligand [H2TMPro ​= ​terephthaloyl-mono(l-proline)] with the ancillary dipyridyl ligands [bpea ​= ​1,2-bis(4-pyridyl)ethane and bipy ​= ​4,4′-bipyridine], five new homochiral coordination polymers were synthesized. Compounds [Cu3(TMPro)2(μ3-OH)2]·4H2O (1) and [Zn3(TMPro)2(μ3-OH)2]·4H2O (2) are isostructural complicated 3D frameworks, which contain the intertwined right- and left-handed helical chains built from the butterfly-shaped [Cu4(μ3-OH)2(RCOO)6] units. Compound [Cu2(TMPro)2(bpea)2(H2O)2]·7H2O (3) displays a 3D framework composed of Cu1-TMPro left-handed helical chains and Cu2-TMPro right-handed helical chains connected by the bpea ligands. Compound [Cd4(TMPro)4(bpea)6]·10H2O·4C2H5OH (4) features a 3-fold interpenetrating 3D framework with 5-connected hexagonal bnn topological net constructed from the {Cd-TMPro} chains and bpea ligands. Compound [Ni(TMPro)(bipy)(H2O)3] (5) exhibits a {Ni-bipy}2+ 1D chain decorated by the TMPro2− anions. Magnetic susceptibility measurements indicate ferromagnetic exchange interactions between Cu(II) ions in 1. Photoluminescence spectra of 2 show corresponding emission bands of TMPro2− anions. Additionally, for 2, the Ksv value of 553 ​M−1 and detection limit of 70 ​μM imply it can detect the Cr2O72− anion.

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel.

The aqueous equimolar reaction of Ag(i) ions with the thionucleoside enantiomer (−)6-thioguanosine, ((−)6tGH), yields a one-dimensional coordination polymer {Ag(−)tG}n, the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra. At concentrations ≥15 mmol l−1 reactions form a sample-spanning hydrogel which shows self-repair capabilities with instantaneous recovery in which the dynamic reversibility of the coordination chains appears to play a role. The resulting gel exhibits circularly polarised luminescence (CPL) with a large dissymmetry factor of −0.07 ± 0.01 at 735 nm, a phenomenon not previously observed for this class of coordination polymer.

Structural Analysis and Controllable Fabrication of Two Pentazolate-Based 3D Topological Networks.

Two novel sodium-pentazolate frameworks (namely, MPF-3 and MPF-4) were achieved by adding simple additives. MPF-3 exhibits an aesthetic three-dimensional (3D) framework with the zeolitic MTN topology, featuring Na28N80 and Na20N60 nanocages. In MPF-4, two left-handed helical chains construct enclosed homochiral channels filled with dimethyl sulfone molecules, which constitute a zeolite-like UNJ topology. Importantly, the preparation of these two compounds provides an effective experimental means to explore the unique symmetrical structure and multiple coordination modes of pentazolium anion and demonstrates that it is possible to regulate the crystal structure through appropriate additives.

Lanthanide-Aromatic Iminodiacetate Frameworks with Helical Tubes: Structure, Properties, and Low-Temperature Heat Capacity.

A series of lanthanide coordination polymers [LnL(H2O)2]n [Ln = Pr (1), Nd (2), Sm (3), Eu (4), and Gd (5), H3L = N-(4-carboxy-benzyl)iminodiacetic acid] was hydrothermally prepared and structurally characterized. All the five compounds have been confirmed as 3D Ln-CPs with one-dimensional helical tunnels composed of four helical chains, although there are different coordination geometries around Ln3+. Enantiomeric helixes in 1–3, and absolute left-handed and right-handed helical chains in 4 and 5, respectively, lead to different tunnel spaces. Their conformations can also be featured by different space groups and unit cell dimensions. Photoluminescence measurement on 3 and 4 show characteristic emission peaks of Sm3+ and Eu3+ ions, respectively. The low-temperature heat capacity of 1–4 has been investigated in the temperature range of 1.9–300 K. Their heat capacity values are nearly equal below 10 K and display a crossover with the value order Cp,m(2) > Cp,m(1) ≈ Cp,m(4) > Cp,m(3) above 10 K. The measured heat capacities have been fitted, and the corresponding thermodynamic functions were consequently calculated based on the fitting parameters. The standard molar entropies at 298.15 K have been determined to be (415.71 ± 4.16), (451.32 ± 4.51), (308.53 ± 3.09), and (407.62 ± 4.08) J·mol–1·K–1 for 1, 2, 3, and 4, respectively.

Homochiral coordination architectures based on a series of pyridyl-alanine derivatives with varied configurations: Structural diversity, photoluminescence and magnetic properties

Six homochiral coordination polymers based on a series of designed pyridyl-alanine derivatives ligands (x,y-H2PDBAla, x, y ​= ​2, 6; 2, 5; 3, 5) and different divalent cations in the absence/presence of ancillary ligands, including [Zn (2,6-PDBAla)]∙3H2O (1), [Cd (2,6-PDBAla)] (2), [Cd (2,5-PDBAla) (H2O)3]·2H2O (3), [Cu3(2,5-PDBAla)2 (bipy)2(H2O)2]·10H2O (4), [Co(3,5-PDBAla) (bpea) (H2O)] (5), [Ni(3,5-PDBAla) (bpee) (H2O)2]·5H2O (6) (H2PDBAla ​= ​pyridine-dicarbonyl-bis(l-alanine), bipy ​= ​4,4′-bipyridine, bpea ​= ​1,2-bis(4-pyridyl)ethane, bpee ​= ​1,2-bis(4-pyridyl)ethylene), were prepared and characterized. Three kinds of pyridyl-alanine derivatives ligands with versatile coordination modes bridge metal ions to generate the diverse structures. In the absence of ancillary ligand, the 2,6-H2PDBAla ligands and Zn(II)/Cd(II) ions react to get the compounds 1 and 2.1 exhibits a one-dimensional (1D) “loop” chain structure with the 14-membered rings, whereas a 3D framework with the qtz topology was observed in 2, in which the right-handed single-stranded and the left-handed double-stranded helical chains coexist. The 2,5-H2PDBAla ligands coordinate with Cd(II)/Cu(II) ions to yield the compounds 3 and 4.3 shows 1D right-handed single-stranded helical chain, and 4 shows a 2D layer constructed from right-handed single-stranded helical chain. The integration of 3,5-H2PDBAla ligands and Co(II)/Ni(II) ions leads to the compounds 5 and 6.5 displays a 2D wavy layer, consisting of the [Co(3,5-PDBAla)] right-handed single-stranded helical chain and the [Co(bpea)]2+ zigzag chain, and 6 displays a 2D layer with sql topology. The photoluminescence spectra of 1, 2 and 3 reveal the corresponding emissions of organic ligands, their maximum emission peaks appear at 402, 401 and 433 ​nm, respectively. Magnetic susceptibility mensuration of 5 gives the J of −12.35 ​cm−1, indicating strong antiferromagnetic interactions between the Co(II) ions.

Insight into the Construction of (3,6)-Connected rtl, ant, and Chiral anh Nets Based on Structural Investigation of Several MOFs via Steric Tuning of Linkers.

Six cobalt-organic frameworks (1-6) were solvothermally constructed with a tritopic pyridine-carboxylate linker (L-H) and its methyl- and methoxy-functionalized derivatives (L-OCH3 and L-CH3). Due to incorporated multiple substituents with various steric hindrances, the tritopic linkers adopt different molecular configurations, Y-shaped and T-shaped, which further combine octahedral or trigonal-prismatic inorganic nodes to afford diverse (3,6)-connected nets. Consequently, 1 and 2 are rtl nets and 3 and 4 are ant nets. Notably, 5 and 6 present rarely observed chiral anh (flu-3) networks with left-handed double helical chains. The structural investigation indicates that the steric tuning of linkers may essentially dictate the resulting diverse MOF structures. Furthermore, the MOFs presented here can be regarded as an ideal structural platform for a better understanding of the assembly of (3,6)-connected rtl, ant, and chiral anh nets, which are closely related to the shape and geometric configuration/conformation of tridentate organic nodes as well as inorganic building nodes.

Two ZnII-based MOFs constructed with biphenyl-2,2′,5,5′-tetracarboxylic acid and flexible N-donor ligands: syntheses, structures and properties

Two new Zn2+-based metal-organic frameworks (MOFs) based on biphenyl-2,2',5,5'-tetracarboxylic acid, i.e. H4(o,m-bpta), and N-donor ligands, namely, poly[[(μ4-biphenyl-2,2',5,5'-tetracarboxylato)bis{[1,3-phenylenebis(methylene)]bis(1H-imidazole)}dizinc(II)] dimethylformamide monosolvate dihydrate], {[Zn2(C16H6O8)(C14H14N4)2]·C3H7NO·2H2O}n or {[Zn2(o,m-bpta)(1,3-bimb)2]·C3H7NO·2H2O}n (1) {1,3-bimb = [1,3-phenylenebis(methylene)]bis(1H-imidazole)}, and poly[[(μ4-biphenyl-2,2',5,5'-tetracarboxylato)bis{[1,4-phenylenebis(methylene)]bis(1H-imidazole)}dizinc(II)] monohydrate], {[Zn2(C16H6O8)(C14H14N4)2]·H2O}n or {[Zn2(o,m-bpta)(1,4-bimb)2]·H2O}n (2) {1,4-bimb = [1,4-phenylenebis(methylene)]bis(1H-imidazole)}, have been synthesized under solvothermal conditions. The complexes were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction and powder X-ray diffraction analysis. Structurally, the (o,m-bpta)4- ligands are fully deprotonated and combine with Zn2+ ions in μ4-coordination modes. Complex 1 is a (3,4)-connected porous network with honeycomb-like [Zn2(o,m-bpta)]n sheets formed by 4-connected (o,m-bpta)4- ligands. Complex 2 exhibits a (2,4)-connected network formed by 4-connected (o,m-bpta)4- ligands linking Zn2+ ions in left-handed helical chains. The cis-configured 1,3-bimb and 1,4-bimb ligands bridge Zn2+ ions to form multi-membered [Zn2(bimb)2] loops. Optically, the complexes show strong fluorescence and display larger red shifts compared to free H4(o,m-bpta). Complex 2 shows ferroelectric properties due to crystallizing in the C2v polar point group.

Manganese-organic framework assembled by 5-((4′-(tetrazol-5″-yl)benzyl)oxy)isophthalic acid: A solvent-free catalyst for the formation of carbon–carbon bond

A new three-dimensional manganese-based metal–organic framework Mn4L2(HL)(H2O)5, (1), based on semi-rigid 5-((4′-(tetrazol-5′’-yl)benzyl)oxy)isophthalic acid ligand (H3L) have been prepared and characterized under solvothermal condition. In the structure of 1, trinuclear Mn3O13N2 units are linked each other by sharing vertex and edge to form left- and right- hand helical O-Mn-O chains along b axis, then adjacent left and right handed helical chains are interconnected by L3− and HL2− ligands to generate a 2D layer and L3− ligands with mode II connect the neighboring layers to form a 3D network. 1 shows high stability under different pH conditions and various organic solvents. After activation, 1 exhibits excellent catalytic properties for two typical CC bond reactions, cyanosilylation and Knoevenagel condensation reaction of aldehydes, under solvent-free conditions at room temperature.

Novel triorganotin complexes based on phosphonic acid ligands: Syntheses, structures and in vitro cytostatic activity

Six novel organotin phosphonate complexes, [(Me3Sn)4(HL1)4]n1, [(Me3Sn)2(HL2)2]n2, [(Me3Sn)2L3(H2O)]n3, [(Ph3Sn)(HL1)]64, [(Ph3Sn)2L2]n5 and [(Ph3Sn)2L3]66, derived from phosphonic acid ligands [NaHL1 = 1-C10H7OPO2(OH)Na, H2L2 = 1-C10H7PO(OH)2, H2L3 = 2-C10H7PO(OH)2], have been synthesized and characterized by elemental analysis, FT-IR, NMR (1H, 13C, 31P and 119Sn) spectroscopy and X-ray crystallography. The structural analysis reveals that complexes 1 and 5 display 1D infinite zig-zag chain structures, and complex 2 shows 1D right-handed helical chain structure, while complex 3 displays 1D left-handed helical chain structure. Complexes 4 and 6 are 24-membered macrocyclic rings interconnected by P, O and Sn atoms. Additionally, the molecules of complexes 1 and 3 are further linked through intermolecular π···π and O-H···O interaction into supramolecular structures, respectively. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1–6 against the human cervix tumor cells (HeLa), human hepatocellular carcinoma cells (HepG-2) and human normal breast cells (HBL-100). Importantly, the anti-proliferative properties and possible pathway of complex 6 are investigated, and the results demonstrate that complex 6 could induce apoptotic cell death via an overload of intracellular reactive oxygen species (ROS) levels and the dysfunctional depolarization of mitochondrial membranes.

Construction of luminescent coordination polymers based on 5-(1-(carboxymethyl)-pyrazol-3-yl)isophthalic ligand for sensing Cu2+ and acetone

Two new coordination polymers (CPs), namely, [Zn3(L)2(phen)3(H2O)2·2H2O]n (phen = 1,10-phenanthroline) (1) and [Pb(HL)]n(2) were constructed from the coordination reaction of 5-(1-(carboxymethyl)-pyrazol-3-yl)isophthalic acid (H3L) ligand and Zn(II) or Pb(II) ions under hydrothermal conditions. It was found that 1 and 2 exhibited an infinite one-dimensional (1D) chain and three-dimensional (3D) framework with left-handed and right-handed helical chains based on single crystal X-ray diffraction analysis, respectively. Both of them had good luminescent property at room temperature. Meanwhile, 1 possessed highly luminescent sensing properties for environmentally relevant Cu2+ ions with a quenching coefficient Ksv of 1.509 × 104 M−1, and the fluorescence quenching efficiency of acetone reached 90%, which indicated that 1 could be taken as a potential candidate for developing multifunctional luminescent sensors. Our work thus paves a way for developing CPs as an appealing platform to construct crystalline materials for environmental applications.

Enantiomeric Polyoxometalates Based on Malate Chirality-Inducing Tetra-ZrIV-Substituted Keggin Dimeric Clusters.

On the basis of the synergistic strategy of lacunary polyoxometalate structure-directing function and chiral ligand inducting role, two pairs of enantiomeric polyoxotungstates, (NH4)4(TMA)4[Zr4(μ3-O)2(l-/d-mal)2(B-α-HSiW10O37)2] (TMA = tetramethylammonium, mal = malate (C4H5O5); l-mal for 1a, d-mal for 1b) and (NH4)4(TMA)4[Zr4(μ3-O)2(l-/d-mal)2(B-α-PW10O37)2] (l-mal for 2a, d-mal for 2b), and a mesomeric polyoxotungstate, (NH4)3Na2K5[Zr4(μ3-O)2(l-mal)(d-mal)(B-α-SiW10O37)2] (3), were hydrothermally synthesized. 1a, 2a and 1b, 2b respectively exhibit 1-D 21 right- and left-hand helical chains formed by hydrogen-bonding interactions, and 3 forms a 3-D (3,10)-connected framework by Na+/K+ ions with {418.624.83}{43}2 topology. These homochiral compounds represent the first examples of enantiomerically pure ZrIV-substituted Keggin POMs. In this system, {Zr4(μ3-O)2(l-/d-mal)2} clusters transfer chirality from d- or l-mal to Keggin polyoxotungstate dimeric clusters, which was demonstrated by structural comparison between the homochiral architecture and mesomer as well as circular dichroism spectra of enantiomers. UV-vis diffuse reflectance spectra reveal that 1-3 are potential semiconductor materials. In addition, 1 and 2 exhibit second harmonic generation response with their response intensities of 0.8 times that of KDP.

Synthesis, Structure and In Vitro Anti-gastric Cancer Activity of Two New Mixed-Ligand Cu(II) and Cd(II)-Coordination Polymers

By using a strategy of introducing two organic ligands with different donor groups, two new Cu(II) and Cd(II) coordination polymers (CPs) [Cu3(OH)(pz)3(Hpz)(H2O)(ipa)](H2O)4 (1, Hpz = pyrazol, H2ipa = isophthalic acid) and [Cd(phen)(ndc)](H2O) (2, phen = 1,10-phenanthroline, H2ndc = 1,2-naphthalene dicarboxylic acid) are synthesized and characterized. The molecular structures of the as-prepared CPs were determined by the single crystal X-ray diffraction (SCXRD) studies and their phase purities have been confirmed via the power X-day diffraction analysis (PXRD). The Cu(II)-based complex 1 is composed of trinuclear Cu3(µ3-OH)(pz)3 clusters that extended by the ipa2− ligands into a 1D left-handed helical chain along the c axis. In complex 2, the ndc2− ligands connect with the binuclear Cd2 unit along the c axis to shape a 1D chain-like structure, which is further stacked into a 2D layered network via π–π stacking. The as-prepared two CPs transformed to the nanoscale regime by mechanical grinding to yield nano 1 and nano 2 with excellent water dispersibility, maintaining its crystallinity. In addition, the in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were conducted on the gastric cancer cell line AGS with increasing concentrations of the two nanosized CPs, which reveal their promising anticancer activity.

Syntheses, structures and in vitro cytostatic activity of four novel homochiral organotin(IV) phosphonates

Four novel homochiral organotin phosphonates, namely, (R)-, (S)-[(Me3Sn)2(pemp)(H2O)]n (1, 2) and (R) -, (S)-[(Ph3Sn)2(pemp)2]n (3, 4) [pempH2 = (R)- or (S)-(1-phenylethylamino) methylphosphonic acid], were synthesized and characterized by X-ray diffraction analysis, elemental analysis, FT-IR, NMR (1H, 13C, 31P and 119Sn), TGA (thermogravimetric analysis) and CD (circular dichroism spectra). The structure analysis indicates that complex 1 displays 1D left-handed helical chain and complex 2 shows right-handed helical chain. These 1D chains are further linked into a 2D supramolecular network architecture through the intermolecular O–H⋯O interactions. Complexes 3 and 4 are isostructural that showing 1D infinite zig-zag chain structure. In addition, the molecules of complexes 3 and 4 are further linked through intermolecular C–H···π interactions into a 2D supramolecular structure. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1–4 against the human cervix tumor cells (HeLa) and the human hepatocellular carcinoma cells (HepG-2).

Arylazoimidazole Coordinated and Naphthalene-Dicarboxylato Bridged Polymers of Co(II) and Photochromic Zn(II) Complexes

Naphtheledicarboxylato ((NDC2–) bridged coordination polymers (CPs) along with (E)-1-methyl-2-(p-chlorophenylazo)imidazole (ClPai-Me) coordination to Co(II), [Co(∝-NDC)0.5(∝4-NDC)0.5(ClPai-Me)]·0.5H2O (1), and to Zn(II), [Zn(∝-NDC)0.5(∝4-NDC)0.5(ClPai-Me)]·0.5H2O (2), have been characterized. In the single crystal X-ray structure of 1, ClPai-Me chelates to the Co(II) ion by N(azo) and N(imidazolyl), whereas in compound 2, it acts as a monodentate N(imidazolyl) donor to the Zn(II) ion. The coordination atmosphere around Co(II) in the 1 ion is distorted octahedral CoN2O4, whereas in the case of 2, it is distorted square pyramidal ZnNO4. Compounds 1 and 2 exhibit the right-handed (P) and left-handed (M) one-dimensional helical chain. NDC–2 is serving as a bridge between two M(II) ions to constitute μ-NDC and four M(II) ions to construct μ4-NDC to assemble three-dimensional polymers. Upon UV light (369 nm) irradiation, compound 2 shows trans-to-cis isomerization of -N═N–C6H4–Cl-p both in the solid and solutio...

Isostructural lanthanide metal-organic frameworks comprised of left-handed helical chains: Synthesis, structure and luminescent properties

Six isostructural three-dimensional (3D) lanthanide metal-organic frameworks (Ln-MOFs), [Ln(μ2-OH)(PDC)(H2O)2]·DMF (Ln=Pr (1), Nd (2), Eu (3), Tb (4), Ho (5), and Yb (6), H2PDC=pyridine-3,5-dicarboxylic acid), have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal gravimetric analysis. The framework contains unusual Ln-carboxylate/μ2-OH left-handed helical chains, which are extended by PDC2− linkers to form 3D networks with 1D hexagonal channel. The lanthanide contraction effect induces the decreases of average Ln- distances from Pr to Yb. Due to the efficient sensitization of PDC2− ligand, complexes 2 and 6 display strong characteristic luminescence in the near-infrared (NIR) region, respectively. Moreover, the luminescent properties of complexes 3 and 4 are also studied in the solid state at room temperature.

Syntheses, Crystal Structures, and Properties of Two IB Group Metal Coordination Polymers Based on 2-(Trifluoromethyl)-1H-Imidazole-4,5-Dicarboxylate

Two new IB group metal coordination polymers, namely, {[Cu3(TFMIDC)2(H2O)2] · 4H2O}n (I) and [Ag2(HTFMIDC)(Py)] n (II) (H3TFMIDC = 2-(trifluoromethyl)-1H-imidazole-4,5-dicarboxylic acid, Py = pyridine), have been successfully prepared and structurally characterized by different techniques including single crystal X-ray diffraction (CIF files CCDC nos. 1545402 (I) and 1545403 (II)), IR spectra, and powder X-ray diffraction. Compound I features an interesting two-dimentional (2D) sheet containing 1D left-handed and right-handed helical chains, while compound II exhibits an infinite 1D zig–zag chain structure. Both two coordination polymers further stack through weak interactions to give rise to 3D supramolecular frameworks. Furthermore, the thermal stabilities of I and II as well as the photoluminescent property of II were also studied.

A homochiral Zn-Dy heterometallic left-handed helical chain complex without chiral ligands: anion-induced assembly and multifunctional integration.

Both second-order nonlinear optical and single-molecule magnet properties are observed in a novel 1D homochiral Zn-Dy heterometallic left-handed helical chain complex (1) without chiral ligands, which evolves from a Zn3Dy2 pentanuclear cluster complex (2), thanks to the structural guiding role of perchlorate anions.