Spontaneously Resolved Homochiral 3D Lanthanide−Silver Heterometallic Coordination Framework with Extended Helical Ln−O−Ag Subunits

Conglomerate, Racemate, and Achiral Crystals of Polymetallic Europium(III) Compounds of Bis- or Tris-β-diketonate Ligands and Circularly Polarized Luminescence Study

This work reports (a) conglomerate and racemic crystal structures of [(Δ,Δ,Δ,Δ,Δ,Δ)- or/and (Λ,Λ,Λ,Λ,Λ,Λ)-Eu^III ₆(TTP)₈(OH₂)₆Na₄] _n coordination polymers, (b) racemic crystal structures of (Δ,Δ,Δ,Δ)-/(Λ,Λ,Λ,Λ)-Eu^III ₄(TTP)₄(bipy)₄(MEK)₂(OH₂)₂ tetrahedral clusters, and (c) the achiral crystal structure of the [Eu^III ₂(BTP)₄(OH₂)₂Na₂] _n coordination polymer (where BTP = dianionic bis-β-diketonate, TTP = trianionic tris-β-diketonate, and bipy = 2,2'-bipyridine). The screw coordination arrangement of the TTP ligand has led to the formation of homoconfigurational racemic Eu^III products. The conglomerate crystallization of [Eu^III ₆(TTP)₈(OH₂)₆Na₄] _n appears to be caused by the presence of the sodium, Na⁺ counterions, and interactions between oxygen atoms and the trifluoromethyl unit of the TTP ligand and Na⁺ ions. All the Eu^III compounds exhibit characteristic red luminescence (⁵D₀ → ⁷F_J, J = 0-4) in solution or in the solid crystalline state. Circularly polarized luminescence (CPL) was observed in the chiral Eu^III ₆(TTP)₈(OH₂)₆Na₄] _n species, displaying a |g _lum| value in the range of 0.15 to 0.68 at the ⁵D₀ → ⁷F₁ emission band. Subtle changes of the [Eu^III ₆(TTP)₈(OH₂)₆Na₄] _n structure which may be due to selection of twinned crystals or crystals that do not correspond to a perfect spontaneous resolution, are considered to be responsible for the variation in the observed CPL values.

Spontaneous resolution of a Δ/Λ-chiral-at-metal pseudo-tetrahedral Schiff-base zinc complex to a racemic conglomerate with C–H⋯O organized 41- and 43-helices

Weak supramolecular interactions can be decisive!

Vitamin B3 metal-organic frameworks as potential delivery vehicles for therapeutic nitric oxide

The synthesis and structural characterization of two isostructural metal (M=Ni, Co) 3D framework structure that integrate vitamin B₃ building blocks with NO delivery capabilities and low toxicity is presented. The compounds with a formula [M₂(μ₂-H₂O)(μ-vitamin B₃)₄]·2H₂O contain two crystallographic distinct divalent metal centres connected by a bridging water and carboxylate group from vitamin B₃. The porous compounds have the capability of storing and releasing nitric oxide (NO) in a slow and reversible manner, with released amounts of 2.6 and 2.0μmol NOmg_solid^-1, on the Ni and Co compound, respectively. The NO release followed a convenient slow release kinetic profile in both gas and liquid phases. Haemoglobin tests demonstrated that NO is released to the medium in a biologically active form, thus suitable to trigger the desired response in biological systems. The toxicity of the samples with and without loaded NO was evaluated from cytotoxicity tests in HeLa and HEKn cells, showing low toxicity of the compounds at concentrations below 180μgcm^-3. The overall results indicate that these bio based MOFs are of interest for therapeutic applications related with NO delivery. STATEMENT OF SIGNIFICANCE.

Poly[[tetra-aqua-tetra-kis-[μ3-5-(pyridine-4-carboxamido)-isophthalato]nickel(II)diterbium(III)] tetra-hydrate]

In the title compound, {[NiTb₂(C₁₄H₈N₂O₅)₄(H₂O)₄]·4H₂O}_n, the Tb^III ion is coordinated by one water mol­ecule and seven O atoms from four 5-(pyridine-4-carboxamido)­isophthalate (L) ligands in a distorted square-anti­prismatic arrangement, while the Ni^II ion, lying on an inversion center, is six-coordinated in an octa­hedral geometry by two pyridine N atoms, two carboxyl­ate O atoms and two water mol­ecules. One L ligand bridges two Tb^III ions and one Ni^II ion through two carboxyl­ate groups and one pyridine N atom. The other L ligand bridges two Tb^III ions and one Ni^II ion through two carboxyl­ate groups, while the uncoordinating pyridine N atom is hydrogen bonded to an adjacent coordinating water mol­ecule. Extensive O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds play an important role in stabilizing the crystal structure.

Poly[[tetra-aqua-tetra-kis-[μ(3)-5-(pyridine-4-carboxamido)-isophthalato]cobalt(II)dierbium(III)] tetra-hydrate]

In the centrosymmetric polymeric title compound, {[CoEr₂(C₁₄H₈N₂O₅)₄(H₂O)₄]·4H₂O}_n, the Er^III cation has a coordination number of eight and is surrounded by seven carboxyl­ate O atoms from four 5-(pyridine-4-carboxamido)­isophthalate (L) ligands and one water mol­ecule, forming a distorted square-anti­prismatic arrangement. The Co^II cation is located on an inversion center and is coordinated by two pyridine N atoms, two carboxyl­ate O atoms and two water mol­ecules in a distorted octa­hedral geometry. The asymmetric unit contains two anionic L ligands. One bridges two Er^III cations and one Co^II cation through two carboxyl­ate groups and one pyridine N atom, while the other bridges two Er^III cations and one Co^II cation through two carboxyl­ate groups. Extensive O—H⋯O, O—H⋯N and N—H⋯O hydrogen-bonding inter­actions are present in the crystal, involving all uncoordinated water mol­ecules and the uncoordinated pyridine N atom of one of the ligands bonded to an adjacent coordinated water mol­ecule. The title compound is isotypic with the gadolinium analogue.

Poly[[tetra-aqua-tetra-kis-[μ(3)-5-(pyridine-4-carboxamido)-isophthalato]-cobalt(II)-diholmium(III)] tetra-hydrate]

In the centrosymmetric polymeric title compound, {[CoHo₂(C₁₄H₈N₂O₅)₄(H₂O)₄]·4H₂O}_n, the Ho^III ion is coordinated by one water mol­ecule and four 5-(pyridine-4-carboxamido)­isophthalate (L) ligands in a distorted square-anti­prismatic arrangement. The Co^II ion, located on an inversion center, is coordinated by two pyridine N atoms, two carboxyl­ate O atoms and two water mol­ecules in a distorted octa­hedral geometry. One L ligand bridges two Ho ions and one Co ion through two carboxyl­ate groups and one pyridine N atom. The other L ligand bridges two Ho ions and one Co ion through two carboxyl­ate groups, while the uncoordinated pyridine N atom accepts a hydrogen bond from an adjacent coordinated water mol­ecule. Extensive O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonding is present in the crystal.

Solvothermal synthesis, crystal structure, and properties of lanthanide-organic frameworks based on thiophene-2,5-dicarboxylic acid

A series of lanthanide-organic framework coordination polymers, {[La(2)(TDC)(2)(NO(3))(H(2)O)(4)](OH)·5H(2)O}(n) (1) and [Ln(TDC)(NO(3))(H(2)O)](n) (TDC = thiophene- 2, 5- dicarboxylic acid; Ln = Nd(2), Sm(3), Eu(4), Gd(5), Tb(6), Dy(7), Ho(8), Er(9), Yb(10)) have been synthesized by solvothermal reaction and characterized by elemental analysis, FT-IR, TG analysis, single-crystal X-ray diffraction and power X-ray diffraction. The single-crystal X-ray diffraction analysis results show that 1 displays a 3-D porous framework with (3,7)-connected {4(10).6(11)}{4(3)} topology. The compounds 2-10 crystallized in the same P2(1)/c space group and exhibits a (3,6)-connected {4.6(2)}(2){4(2).6(10).8(3)} topology, Right-handed and left-handed helical chains coexist in the 2-D layer structure. The luminescence properties of 2-10 and the magnetic properties of 5,7,8,9 were investigated.

Poly[[tetra-aquatetrakis-[μ(3)-5-(pyridine-4-carboxamido)-isophthalato]cobalt(II)digadolinium(III)] tetra-hydrate]

In the centrosymmetric polymeric title compound, {[CoGd₂(C₁₄H₈N₂O₅)₄(H₂O)₄]·4H₂O}_n, the Gd^III cation is coordinated by one water mol­ecule and four pyridine-4-carboxamido­isophthalate (L) anions in a distorted square-anti­prismatic arrangement, while the Co^II cation, located on an inversion center, is coordinated by two pyridyl-N atoms, two carboxyl­ate-O atoms and two water mol­ecules in a distorted octa­hedral geometry. The asymmetric unit contains two anionic L ligands: one bridges two Gd cations and one Co cation through two carboxyl groups and one pyridine-N atom; the other bridges two Gd cations and one Co cation through two carboxyl groups and the uncoordinated pyridine-N atom is hydrogen-bonded to the adjacent coordinated water mol­ecule. Extensive O—H⋯O and N—H⋯O hydrogen bonds are present in the crystal structure.