Structural Induction Effect of a Zwitterion Pyridiniumolate for Metal–Organic Frameworks

Preparing Coordination Polymers with Acentric-Centric Structural Arrangements Related to SHG Response

Three coordination polymers were successfully constructed in this work by applying biligands and were distinctly characterized through single crystal X-ray diffraction. The compounds crystallized in acentric and centric space groups under the direction of coordination bonds and adopted 1-dimensional link and 2-dimensional layer structures, as well as different coordination geometries for metal atoms. All compounds exhibited good thermal stability and luminescence properties, and compound 2 exhibited a good second harmonic generation (SHG) response. The method used in this work offers a feasible approach to using biligand and changing metal salt to obtain the microstructures of coordination materials with specific properties.

Square-planar Tetranuclear Cluster-based Alkaline Earth Metal-organic Frameworks with Enhanced Proton Conductivity

Alkaline earth (AE) metal complexes have garnered significant interest in various functional fields due to their nontoxicity, low density, and low cost. However, there is a lack of systematic investigation into the structural characteristics and physical properties of AE-metal-organic frameworks (MOFs). In this research, we synthesized isostructural MOFs consisting of AE4(μ4-Cl) clusters bridged by benzo-(1,2;3,4;5,6)-tris(thiophene-2'-carboxylic acid) (BTTC3-) ligands. The resulting structure forms a truncated octahedral cage denoted as [AE4(m4-Cl)]6(BTTC)8, which further linked to a porous three-dimensional framework. Among the investigated AE ions (Ca, Sr, and Ba), the Ca4-MOF demonstrated good chemical stability in water compared to Sr4-MOF and Ba4-MOF. The N2 adsorption and solid-state UV-vis-NIR absorption behaviors were evaluated for all AE4-MOFs, showing similar trends among the different metal ions. Additionally, the proton conduction study revealed that the Ca4-MOF exhibited ultra-high proton conductivity, reaching 3.52×10-2 S cm-1 at 343 K and 98 % RH. Notably, the introduction of LiCl via guest exchange resulted in an improved proton conduction of up to 6.36×10-2 S cm-1 under similar conditions in the modified LiCl@Ca4-MOF. The findings shed light on the regulation of physical properties and proton conductivity of AE-MOFs, providing valuable insights for their potential applications in various fields.

Two-dimensional coordination polymers with high proton conductivity and ultrafast highly efficient molecular sieving constructed by the structural inductive effect

A family of unique 2D-layered Cu-based coordination polymers (abbreviated as HNNU-1α, 1β and 1γ) with different halide anions were successfully constructed using a zwitterion pyridiniumolate as the structural inductive agent (SIA). More importantly, we found that the laminates of HNNU-1α exhibit ultrafast highly-efficient molecular sieving in a water system, and HNNU-1α to 1γ display a good proton conductivity of ca. 2.2 × 10^-2, 4.9 × 10^-5, and 3.0 × 10^-4 S cm^-1 at 90 °C and 98% relative humidity (RH), respectively.

Retention of a Four-Fold Interpenetrating Cadmium-Organic Framework through a Three-Step Single Crystal Transformation

Controlled hydration leads to four derivatives of a metal-organic framework consisting of cadmium ions, N¹,N¹,N⁴,N⁴-tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine, and coordinated and free nitrates. The balance of water coordination and the multitude of bonding of the weakly coordinated nitrate lead to a progressive change in the coordination number of the Cd²⁺ ions from eight to seven to six without great perturbation to the 4-fold interpenetration three-dimensional framework.

Coordination Assemblies of Zn(II) Coordination Polymers: Positional Isomeric Effect and Optical Properties

Two Zn(II) coordination polymers (CPs) [Zn(L)(pphda)] (1) and [Zn(L)(ophda)]·H2O (2) were prepared by reactions of ZnSO4·7H2O based on the N-donor 1,4-di(1H-imidazol-4-yl)benzene (L) ligand and two flexible carboxylic acids isomers of 1,4-phenylenediacetic acid (H2pphda) and 1,2-phenylenediacetic acid (H2ophda) as mixed ligands, respectively. Structures of CPs 1 and 2 were characterized by elemental analysis, Infrared spectroscopy (IR), thermogravimetric analysis and single-crystal X-ray diffraction. The CP 1 is a fourfold interpenetrating 66-diamond (dia) architecture, while 2 is a 2D (4, 4) square lattice (sql) layer based on the Zn2(cis-1,2-ophda2−)2 binuclear Zn(II) subunits. The luminescent property, including luminescence lifetime and quantum yield (QY), have been investigated for CPs 1 and 2.

Synthesis, Crystal Structure, and Properties of a Zn(II) Coordination Polymer Based on a Difunctional Ligand Containing Triazolyl and Carboxyl Groups

A new compound, namely, [Zn(L)2]n (1) was obtained by the reaction of 2-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) with ZnSO4·7H2O, and the compound was characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis. The linear HL ligands were deprotonated to be L− anions and act as two-connectors to link Zn2+ to form a two-dimensional (2D) lay structure with (4, 4) topology. The large vacancy of 2D framework allows another layer structure to interpenetrate, resulting in the formation of 2D + 2D → 2D parallel interpenetration in 1. The weak interactions, such as hydrogen bonding and π–π stacking interactions, connect the adjacent 2D layers into a three-dimensional (3D) coordination polymer. The solid-state UV-visible spectroscopy and luminescent property have also been studied.

Metal(II) Coordination Polymers Derived from Mixed 4-Imidazole Ligands and Carboxylates: Syntheses, Topological Structures, and Properties

Four new metal⁻organic coordination polymers [Cu(L)(mpa)]·3H₂O (1), [Co(L)(mpa)]·H₂O (2), [Zn(L)(mpa)]·H₂O (3), and [Cd(L)(mpa)(H₂O)]·H₂O (4) were synthesized by reactions of the corresponding metal(II) salts based on mixed ligands of 1,4-di(1H-imidazol-4-yl)benzene (L) and 4-methylphthalic acid (H₂mpa), respectively. The structures of the complexes were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Compound 1 exhibits a binodal 4-connected three dimensional (3D) architecture with (6⁵·8)-CdSO₄ topology, while complexes 2 and 3 are isostructural and have two-dimensional (2D) layer structure with (4, 4) sql topology based on the binuclear metal subunits. Complex 4 has the same 2D layer structure with (4, 4) sql topology as complexes 2 and 3, but the inclined interpenetration of parallel sets of layers result in the formation with 2D + 2D → 3D framework. The activated sample 1 shows selective CO₂ uptake over N₂. The photoluminiscent properties together with quantum yield (QY) and luminescence lifetime are also investigated for complexes 3 and 4 in the solid state at room temperature.

Selective fluorescent sensing and photocatalytic properties of three MOFs based on naphthalene-1,4-dicarboxylic acid and 2,4,5-tri(4-pyridyl)-imidazole

Three MOFs display high sensitivity in the detection of NB and Ca²⁺ or Co²⁺ ions as luminescent probes. Moreover, 3 exhibits a relatively good photocatalytic degradation activity of rhodamine B.

Six novel coordination polymers based on the 5-(1H-tetrazol-5-yl)isophthalic acid ligand: structures, luminescence, and magnetic properties

Six coordination polymers containing clusters or chains have been synthesized by a combination of one tetrazolate-isophthalate ligand and N-donor ligands. Their structures, magnetic properties and luminescence properties were discussed in detail.

Host-Guest Engineering of Coordination Polymers for Highly Tunable Luminophores Based on Charge Transfer Emissions

Aiming at the targeted construction of coordination polymer luminophores, the engineering of host-guest architectures with charge transfer based emissions is performed by utilizing the interactions between the electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (tpt) and electron-rich polycyclic aromatic hydrocarbons (PAHs) motifs as acceptors and donors, respectively. Through guest modulation of a prototype coordination polymer [Cd(tpt)(1,4-pda)(H₂O)₂]·(tpt)·(H₂O)₂ (1) (1,4-H₂pda = 1,4-phenylenediacetic acid), a series of coordination polymers with different PAHs as guests, [Cd₂(tpt)₂(1,4-pda)₂]·guest (2-5) (guest = triphenylene for 2, pyrene for 3, coronene for 4, and perylene for 5), are successfully fabricated. Distinct from 1, coordination polymers 2-5 reveal unique bilayer structures with PAHs interlayer and good stability, owing to the enhanced stacking interactions between tpt motifs and PAH guests. Moreover, their emissions cover a wide range of wavelength due to the effective guest to host charge transfer interactions between donor and acceptor motifs. Their readily tunable host-guest charge transfer based emissions make them good candidates as potential luminophores.

A series of novel cadmium(ii) coordination polymers with photoluminescence and ferroelectric properties based on zwitterionic ligands

Herein, a series of Cd(ii) compounds were obtained by using a zwitterionic ligand (H₃LBr₃) and an aromatic secondary ligand (H₄BTC).

New zinc(ii) dyes with enhanced two-photon absorption cross sections based on the imidazolyl ligand

The effective TPA cross sections of Dyes 1–3 revealed that the exceeding TPA behavior may attributed to form the new D–π–A type compound that enhanced the intramolecular ICT progress. Dyes 1–3 were successfully applied in bio-imaging.

Chiral template induced homochiral MOFs built from achiral components: SHG enhancement and enantioselective sensing of chiral alkamines by ion-exchange

A homochiral anionic framework built from achiral components was synthesized for enantioselective sensing of chiral alkamines. Ion-exchange with polar or chiral organic cations leads to the enhancement of the SHG efficiency.