Qing-Yan Liu

Diversity of Lanthanide(III)-Organic Extended Frameworks with a 4,8-Disulfonyl-2,6-naphthalenedicarboxylic Acid Ligand: Syntheses, Structures, and Magnetic and Luminescent Properties

A sulfonate-carboxylate ligand, 4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H(4)-DSNDA), and eight new lanthanide coordination polymers {[Pr(4)(OH)(4)(DSNDA)(2)(H(2)O)(12)](H(2)O)(10)}(n) (1), [Ln(H(2)-DSNDA)(0.5)(DSNDA)(0.5)(H(2)O)(5)](n) (Ln = La(2), Nd(3), Sm(4), Eu(5), Gd(6), and Dy(7)), and {[Er(H-DSNDA)(H(2)O)(4)](H(2)O)}(n) (8) have been synthesized. Detailed crystal structures of these compounds have been investigated. Compound 1 has a 3D framework featuring the unique cubane-shaped [Pr(4)(μ(3)-OH)(4)] clusters and is a binodal 4,8-connected network with (4(16)·6(12))(4(4)·6(2))(2) topology. Compounds 2-7 are isostructural and have 2D layered structures. Compound 8 is also a 2D layer but belongs to different structural types. The luminescence behavior of compound Eu(5) shows that the π-rich aromatic organic ligands efficiently transfer the absorbed light energy to the Eu(III) ions, thus enhancing the overall luminescent properties of compound Eu(5). The magnetic properties of all compounds except for the diamagnetic La(2) compound have been investigated. In addition, elemental analysis, IR spectra, and thermogravimetric analysis of these compounds are also described.

Chiral Induction in the Ionothermal Synthesis of a 3D Chiral Heterometallic Metal–Organic Framework Constructed from Achiral 1,4-Naphthalenedicarboxylate

A chiral heteometallic compound, [(EMIM)NaCu(1,4-ndc)2]n (1), constructed from the achiral 1,4-naphthalenedicarboxylate (1,4-ndc) ligand has been ionothermally synthesized and structurally and magnetically characterized. The chiral induction effect of the enantiopure 1-ethyl-3-methylimidazolium (EMIM) L-lactate additive in the ionothermal reaction is briefly discussed.

Novel Noncentrosymmetric Zinc Coordination Polymer Containing an Unusual Zinc Carboxylate-Sulfonate Substructure with a (10,3)-d Topology and Its Second-Harmonic-Generation Properties

A novel 3D coordination polymer, Zn(2)(μ(2)-OH)(SIP)(DPP) (1), with mixed ligands of 5-sulfoisophthalate (SIP) and 1,3-di-4-pyridylpropane (DPP), has been hydrothermally synthesized and characterized. 1 contains an unusual 3D subnet with distorted (10,3)-d topology and left/right-handed helical channels. Second-harmonic-generation (SHG) measurements revealed that the material has a strong SHG response (∼2.5 times that of potassium dihydrogen phosphate (KDP)) and is phase-matchable. In addition, photoluminescent and thermogravimetric analysis were also performed on 1.

Two novel luminescent silver(I) coordination polymers containing octanuclear silver cluster units or ligand unsupported Ag⋯Ag interactions constructed from 5-sulfoisophthalic acid (H3SIP) and organic amine

Self-assembly of Ag(NO3)2 with 5-sulfoisophthalic acid monosodium salt (NaH2SIP) in the presence of piperazine (pip) or 4,4′-bipyridyl (bpy) produced two new silver(I) coordination polymers, {(H2pip)2[Ag8(SIP)4(H2O)4](H2O)4}n (1) and {[Ag(bpy)][Ag(HSIP)(bpy)](H2O)2}n (2), respectively. Single-crystal X-ray diffraction reveals that compound 1 has a 2D silver carboxylate-sulfonate layered structure containing an uncommon octanuclear [Ag8(CO2)8] cluster wherein the eight silver(I) atoms form two intersecting Ag4 planes. The 2D layers are further linked by the H2pip molecules through hydrogen bonds into a 3D supramolecular structure. Compound 2 features a 2D supramolecular network formed by silver(I)-bpy double chains and HSIP ligands through the combination of coordination bonds, ligand unsupported Ag⋯Ag interactions and weak Ag⋯O coordinative interactions. In the solid state at room temperature, compound 1 exhibits blue photoluminescence with a maximum at 450 nm upon excitation at 365 nm. Compound 2 shows green photoluminescence with a maximum at 564 nm upon excitation at 392 nm.

Field-Induced Slow Magnetic Relaxation and Gas Adsorption Properties of a Bifunctional Cobalt(II) Compound

A new compound, {[Co(bmzbc)2] · 2DMF}n (JXNU-1, JXNU denotes Jiangxi Normal University), based on the 4-(benzimidazole-1-yl)benzoate (bmzbc(-)) ligand has been synthesized and structurally characterized. The Co(II) ions are bridged by the rod-like bmzbc(-) ligands to give a two-dimensional (2D) sheet wherein the Co(II) ions are spatially separated from each other by the long bmzbc(-) rods. The 2D sheets are further stacked into a 3D framework with 1D channels occluding the guest DMF molecules. Detailed magnetic studies show that the individual octahedral Co(II) ions in JXNU-1 exhibit field-induced slow magnetic relaxation, which is characteristic behavior of single-ion magnets (SIMs). The rarely observed positive value of zero-field splitting (ZFS) parameter D for the Co(II) ion in JXNU-1 demonstrates that JXNU-1 is a unique example of Co(II)-based SIMs with easy-plane anisotropy, which is also confirmed by the calculations. The microporous nature of JXNU-1 was established by measuring CO2 sorption isotherms. The abrupt changes observed in the C3H8 and C2H6 adsorption isotherms indicate that a structural transformation occurred in the gas-loading process. The long connection between the magnetic metal centers in JXNU-1 meets the requirements for construction of porosity and SIM in a well-defined network, harmoniously providing a good candidate of functional molecular materials exhibiting SIM and porosity.

Diversity of lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate extended frameworks: syntheses, structures, and magnetic properties.

Six lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate frameworks, namely, [Ln(H(2)-DHBDC)(1.5)(H(2)O)(2)](n) (Ln = La (1) and Pr (2); H(4)-DHBDC = 2,5-dihydroxy-1,4-benzenedicarboxylic acid), {[Nd(H(2)-DHBDC)(1.5)(H(2)O)(3)](H(2)O)}(n) (3), {[Eu(H(2)-DHBDC)(NO(3))(H(2)O)(4)](H(2)O)(2)}(n) (4), and {[Ln(2)(H(2)-DHBDC)(2)(DHBDC)(0.5)(H(2)O)(3)](H(2)O)(4)}(n) (Ln = Gd (5) and Dy (6)), with four different structural types ranging from 1D chain, 2D layer to 3D networks have been synthesized and structurally characterized. Compounds La (1) and Pr (2) are isomorphous and exhibit 3D frameworks with the unique 1D tubular channels. Compounds Nd (3) and Eu (4) are 2D layer and 1D zigzag chain, respectively, which are further extended to 3D supramolecular frameworks through extensive hydrogen bonds. Isomorphous compounds of Gd (5) and Dy (6) are 3D frameworks constructed from secondary infinite rod-shaped metal-carboxylate/hydroxyl building blocks. While the hydroxyl groups as secondary functional groups in the 1D chain of Eu (4) and 2D layer of Nd (3) are not bonded to the lanthanide centers, the hydroxyl groups in the 3D frameworks of La (1), Pr (2), Gd (5), and Dy (6) participate in coordinating to lanthanide centers and thus modify the structural types of theses compounds. The magnetic data of compounds Pr (2), Nd (3), Gd (5), and Dy (6) have been investigated in detail. In addition, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) patterns and thermogravimetric analysis of these compounds are described.

Metal oxo cluster-based coordination polymers with rigid 1,4-naphthalenedicarboxylate and semirigid 1,3-di(4-pyridyl)propane ligands: syntheses, structural topologies, and luminescent properties

Hydrothermal reactions of Zn(NO3)2 or Pb(NO3)2 with 1,4-naphthalenedicarboxylic acid (1,4-H2ndc) and 1,3-di(4-pyridyl)propane (dpp) lead to two novel metal oxo cluster-based coordination polymers, namely, [Zn5(μ3-OH)2(1,4-ndc)4(dpp)2]n (1) and [Pb5(μ4-O)(1,4-ndc)4(dpp)]n (2). The structures exhibit different cluster motifs depending on the nature of the metal ions. Compound 1 features a 3D structure based on the pentanuclear [Zn5(μ3-OH)2] secondary building unit (SBU) where the five zinc atoms are coplanar; its topological structure is an uninodal 10-connected network of (36.434.53.62) topology. The zinc ions in 1 have a coordination number varying from 4 to 6 and are accompanied by a variety of coordination geometries such as tetrahedral, trigonal bipyramidal, and octahedral. Compound 2 has a 3D architecture containing an unusual hexanuclear [Pb6(μ4-O)2] cluster unit composed of two edge-sharing oxygen-centred [Pb4(μ4-O)] tetrahedrons. One explanation for the presence of the centred bridging oxide ligands in 2 is that owing to steric constraints sufficient carboxylate ligands cannot coordinate to the Pb(II) centers to satisfy the positive charges of the Pb(II) cations. The Pb(II) ions in 2 exhibit diverse hemidirected coordination geometries with coordination numbers of 6 and 7. In the solid state, compounds 1 and 2 exhibit photoluminescence with emission maximum at 495 and 420 nm, respectively.

The Highly Connected MOFs Constructed from Nonanuclear and Trinuclear Lanthanide-Carboxylate Clusters: Selective Gas Adsorption and Luminescent pH Sensing

The highly odd-numbered 15-connected nonanuclear [Ln9(μ3-O)2(μ3-OH)12(O2C-)12(HCO2)3] and 9-connected trinuclear [Ln3(μ3-O)(O2C-)6(HCO2)3] lanthanide-carboxylate clusters with triangular and linear carboxylate bridging ligands were synergistically combined into Ln-MOFs, [(CH3)2NH2]3{[Ln9(μ3-O)2(μ3-OH)12(H2O)6][Ln3(μ3-O)(H2O)3](HCO2)3(BTB)6}·(solvent)x (abbreviated as JXNU-3, Ln = Gd, Tb, Er; BTB3- = benzene-1,3,5-tris(4-benzoate)), displaying a (3,9,15)-connected topological net. The JXNU-3(Tb) exhibits highly selective CO2 adsorption capacity over CH4 that resulted from the high localized charge density induced by the presence of the nonanuclear and trinuclear cluster units. In addition, JXNU-3(Tb) with high chemical stability and characteristic bright green color exhibits fluorescent pH sensing, which is pertinent to the different protonation levels of the carboxylate groups of the benzene-1,3,5-tris(4-benzoate) ligand with varying pH.

3D metal–organic frameworks constructed of 2D metal aromatic sulfonate–carboxylate layers and 1,3-di(4-pyridyl)propane pillars: syntheses, structural topologies, and luminescent properties

Two metal–organic frameworks {[Zn2(DSBDC)(dpp)2](H2O)2}n (1) (H4DSBDC = 2,5-disulfonylterephthalate acid and dpp = 1,3-di(4-pyridyl)propane) and [Cd2(SBTC)(dpp)1.5]n (2) (H4SBTC = 5-sulfonyl-1,2,4-benzenetricarboxylic acid) with novel sulfonate–carboxylate ligands have been synthesized and structurally characterized. The in situ formation of the H4DSBDC ligand derived from H4SBTC is unprecedented and involves a fundamentally new substitution of sulfonate for carboxylate in the in situ ligand synthesis reaction. The solid state structures of 1 and 2 consist of neutral 2D metal aromatic sulfonate–carboxylate layers, which are pillared by the dpp ligands to generate different 3D architectures. The topological structure of 1 is a trinodal net based on three kinds of topologically equivalent 4-connected nodes with the Schlafli symbol of (64.82). The framework of 2 can be classified as a 4,5,6-connected 3D net with the Schlafli symbol of (43.63) (43.65.82) (46.66.83). In the solid state, compounds 1 and 2 exhibit white-ish and blue photoluminescences, respectively.

Evolution from linear tetranuclear clusters into one-dimensional chains of Dy(III) single-molecule magnets with an enhanced energy barrier

Reactions of DyCl3·6H2O or Dy2O3 with 2-quinolinecarboxylic acid (H-QLC) yielded two compounds, namely, [Dy4(QLC)12(H2O)6]·4H2O (1) and [Dy(QLC)3(H2O)2]n (2). Compound 1 is a linear tetranuclear structure with one central [Dy2(QLC)4(H2O)4] subunit and two terminal [Dy(QLC)3(H2O)] subunits linked by bridging QLC− ligands. Compound 2 has a one-dimensional (1D) chain wherein the [Dy(QLC)2] unit formed by two QLC− ligands chelating a Dy(III) ion is connected by the bridging QLC− ligands. Compounds 1 and 2 exhibit slow magnetic relaxation behaviour in the absence of a static magnetic field, which is rarely observed in lanthanide-carboxylate compounds. During the structural evolution from a linear Dy4 cluster of 1 into a 1D chain of 2, the anisotropy energy barrier (Ueff) is enhanced from 45.4(2) to 144.2(1) K. Though the Dy(III) centers in 1 and 2 all are eight-coordinated with square antiprismatic coordination environments, the higher energy barrier observed for 2 could be the result of a more favorable crystal field for the Dy(III) ions in 2.