Series of Cadmium-Organic Frameworks Based on Mixed Flexible and Rigid Ligands: Single-Crystal-to-Single-Crystal Transformations, Sorption, and Luminescence Properties

Here, we present a series of Cd(II) coordination polymers containing two types of ligands: sterically rigid terephthalate derivatives (bdc-NO22- and bdc-Br2-) and flexible bis(2-methylimidazolyl)propane (bmip). The combination of two types of ligands is used to obtain and characterize compounds by single crystal and powder X-ray diffraction, FT-IR, elemental analysis, and TGA. Guest exchange results in structural transformations. 2-fold interpenetrated 1·DMF and 2·DMF rapidly undergo to 4-fold interpenetrated 1·Et2O, 1·EtOH, and 1·H2O, or 2·Et2O, respectively. Also, changes in the coordinating numbers and length of the N,N'-donor bmip ligand were observed according to single crystal X-ray analysis. Activated guest-free compounds [Cd(bdc-NO2)(bmip)] (1) and [Cd(bdc-Br)(bmip)] (2) are shown to be porous with a BET surface area of 103 and 283 m2·g-1, respectively. Moreover, both compounds demonstrate gate-opening behavior of ethylene adsorption isotherms at low pressures (<1 bar) and highly selective adsorption of benzene over cyclohexane or lower alcohols. Also, both compounds demonstrate a strong dependence of the maximum of the photoluminescence emission on an excitation wavelength. As a result, the photoluminescence color changes from white to red and from blue to red through green and yellow for compounds 1 and 2, respectively, with excitation wavelength changing from 360 to 540 nm.

Catalytic C-H Bond Activation and Knoevenagel Condensation Using Pyridine-2,3-Dicarboxylate-Based Metal-Organic Frameworks

Three 1D coordination polymers (CPs) [M(pdca)(H2O)2] n (M = Zn, Cd, and Co; 1-3), and a 3D coordination framework {[(CH3)2NH2][CuK(2,3-pdca)(pa)(NO3)2]} n (4) (2,3-pdca = pyridine-2,3-dicarboxylate and pa = picolinic acid), have been synthesized adopting a solvothermal reaction strategy. The CPs have been thoroughly characterized using various spectral techniques, that is, elemental analyses, FT-IR, TGA, DSC, UV/vis, and luminescence. Structural information on 1-4 was obtained by PXRD and X-ray single-crystal analyses, whereas morphological insights were attained through FESEM, AFM, EDX, HRTEM, and BET surface area analyses. Roughness parameters were calculated from AFM analysis, whereas dimensions of small domains and interplanar spacing were defined with the aid of HRTEM. CPs 1-3 are 1D isostructural networks, whereas 4 is a 3D framework. Moreover, 1-4 display moderate luminescence at rt. In addition, 1-4 have been applied as economic and efficient porous catalysts for the Knoevenagel condensation reaction and C-H bond activation under mild conditions with good yields (95-98 and 97-99%), respectively. Notably, 1-3 can be reused up to seven cycles, whereas 4 can be reused up to five catalytic cycles with retained catalytic efficiency. Relative catalytic efficacy toward the Knoevenagel condensation reaction follows in the order 2 > 1 > 3 > 4, whereas 2 > 4 > 1 > 3 for C-H activation. The present result demonstrates synthetic, structural, optical, morphological, and catalytic aspects of 1-4.

A luminescent Cd(ii) coordination polymer as a multi-responsive fluorescent sensor for Zn2+, Fe3+ and Cr2O72− in water with fluorescence enhancement or quenching

A luminescent Cd(ii) coordination polymer can act as a multi-responsive sensor for efficiently detecting Zn²⁺, Fe³⁺ and Cr₂O₇²⁻ ions.

Two d10 luminescent metal-organic frameworks as dual functional luminescent sensors for (Fe3+,Cu2+) and 2,4,6-trinitrophenol (TNP) with high selectivity and sensitivity

Two luminescent 3D supramolecular structures [Cd3(L)2(2,2-bipy)2](DMF)3(CH3CH2OH)2(H2O) (1) and [Zn3(L)2(2,2-bipy)2(DMF)2](DMF)2(CH3CH2OH)2(H2O) (2) (H3L = 4,4',4''-nitrilotribenzoic acid) have been successfully synthesized under solvothermal conditions using Cd(NO3)2·4H2O or Zn(NO3)2·6H2O as the metal sources, and 4,4',4''-nitrilotribenzoic acid (H3L), 2,2-bipy as the ligands in DMF solvent. Compound 1 displays a bi-nodal (2,3,6)-coordinated net with {83}2{86·126·163}{8}6 topology, compound 2 can be described as a (3,6)-connected 2-nodal net with kgd topology. The phase purity of compound 1 and 2 is characterized by X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. Compound 1 and 2 can serve as effective luminescent sensors for Fe3+, Cu2+ and TNP via luminescent quenching.

Structural diversity of Zn(ii) based coordination polymers constructed from a flexible carboxylate linker and pyridyl co-linkers: fluorescence sensing of nitroaromatics

Five new Zn(ii) based coordination polymers have been synthesized that were used in the sensing of nitroaromatic compounds via luminescence quenching.

Metal organic frameworks with uni-, di-, and tri-nuclear Cd(ii) SBU prepared from 1,3-bis(4-pyridyl)propane and different dicarboxylate ligands: syntheses, structures and luminescent properties

Systematic variation of co-dicarboxylate ligands leads to three new MOFs based on uni-, di-, and tri-nuclear Cd(ii) SBUs.

Seven entangled coordination polymers assembled from triphenylamine-based bisimidazole and dicarboxylates: interpenetration, self-penetration and mixed entanglement

Seven entangled coordination polymers constructed from a triphenylamine-based bisimidazole and carboxylic acids have been synthesized and characterized.

Crystal structure of tetraaqua-(4,4′-diamino-1,1′-biphenyl-2,2′-disulfonato-κN)(4,4′-bipyridyl-κN)zinc(II) trihydrate, C22H32N4O13S2Zn

C22H32N4O13S2Zn, triclinic, P1̅ (no. 2), a = 9.496(1) Å, b = 10.016(1) Å, c = 16.334(2) Å, α = 102.297(10)°, β = 93.625(10)°, γ = 111.313(10)°, V = 1397.1 Å3, Z = 2, Rgt(F) = 0.0383, wRref(F2) = 0.1020, T = 296 K.

Fluorescent selectivity for small molecules of three Zn-MOFs with different topologies based on a tetracarboxylate ligand

Three Zn-MOFs depended on solvent conditions have been obtained. The guest-free forms demonstrate luminescent sensor for small molecules.

Coordination polymers constructed from a tripodal phosphoryl carboxylate ligand: synthesis, structures and physical properties

Four coordination polymers based on a new tripodal phosphoryl carboxylate H₃TBPPO ligand have been constructed and characterized. Complexes 1–3 show 2-fold interpenetrating flu net, while complex 4 possesses a 4-fold interpenetrating dia network.