A series of lanthanide coordination polymers with 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine: Syntheses, crystal structures and luminescence properties

Multifunctional Luminescent 3D Ln-MOFs with High Sensitivity for Trace Detection of Micronutrients

The synthesis of two versatile fluorescent metal-organic frameworks (MOFs), [Eu(4-NCP)(1,4-bdc)]n·0.5H2O (1) and [Eu(4-NCP)(4,4'-bpdc)]n·0.75H2O (2) (HNCP = 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline, 1,4-H2bdc = benzene-1,4-dicarboxylic acid, 4,4'-H2bpdc = 4,4'-biphenyldicarboxylic acid), was carried out using a hydrothermal method. These MOFs were characterized through various advanced technologies to determine their structural information. The results indicate that both MOFs exhibited 3D network structures with specific topologies. Furthermore, these MOFs demonstrated exceptional thermal stabilities and adsorption capabilities. Additionally, complex 2 was utilized for studying the fluorescence sensing properties of various micronutrients including metal ions, nitro aromatic compounds, and biological small molecules. Notably, complex 2 showed promising potential as a multifunctional sensor for selectively detecting Fe3+, nitrobenzene, and ascorbic acid in aqueous solutions through fluorescence quenching with low limits of detection (LODs ∼ 10-7 M) and high quenching constants (Ksv ∼ 103 M-1). Moreover, the detection mechanism of complex 2 was further investigated by using experimental methods and DFT calculations.

Competitive substitution in europium metal-organic gel for signal-on electrochemiluminescence detection of dipicolinic acid

Metal-organic gels (MOGs) emerged as an attractive luminescent soft material for electrochemiluminescence (ECL). In this work, a cathodic ECL-activated europium metal-organic gel (Eu-MOG) has been synthesized by a facile mixing of Eu3+ with 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine (Hcptpy) under mild conditions. The prepared Eu-MOG is highly mesoporous for co-reactant permeation to produce an ultra-stable and high-efficient ECL, based on the antenna effect of Eu3+ coordinating with Hcptpy. Moreover, dipicolinic acid (DPA) can competitively coordinate with Eu3+ instead of water molecules, producing an enhanced ECL signal. Therefore, an ECL enhancement assay was developed for DPA detection. There was a linear relationship between the ECL intensity and the logarithmic concentration of DPA in the 0.01-1 μM range, and the detection limit is 7.35 nM. This work displays the promising application of Eu-MOG in the ECL field, opening a broad inspection for seeking a new generation of ECL luminophores.

3D-Frameworks and 2D-networks of lanthanide coordination polymers with 3-pyridylpyrazole: photophysical and magnetic properties

A series of 15 lanthanide-containing coordination polymers, both 3D- and 2D-networks, as well as complexes of Ln-trichlorides with 3-(3-pyridyl)pyrazole (3-PyPzH), were synthesized. A large structural diversity is observed depending on the ligand content: 3∞[Ln(3-PyPzH)Cl₃], Ln = Eu and Gd, of sra topology, 2∞[Sm(3-PyPzH)Cl₃], 2∞[Ln₂(3-PyPzH)₃Cl₆]·2solv, Ln = Eu³⁺, Tb³⁺, Dy³⁺, Ho³⁺ and Er³⁺, solv = Tol and MeCN, of sql topology and 2∞[Ln(3-PyPzH₂)Cl₄], Ln = La and Nd, of hcb topology with salt like complexes of the formula [(3-PyPzH₂)][Ln(3-PyPzH)₂Cl₄], Ln = Eu, Tb, Dy and Ho. The products were characterized by single-crystal and powder X-ray diffraction, high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry (DTA/TG) combined with mass spectrometry, differential scanning calorimetry (DSC), IR-spectroscopy, UV-visible spectrophotometry, photoluminescence spectroscopy, and magnetic susceptibility. Absorption spectroscopy shows ion-specific 4f-4f transitions that can be assigned to Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺ and Er³⁺ in a wide range from the UV-VIS to NIR region. An excellent antenna effect through ligand-metal energy transfer was observed in 2∞[Tb₂(3-PyPzH)₃Cl₆]·2solv, leading to high efficiency of the luminescence indicated by a quantum yield up to 76%. Direct current magnetic susceptibility studies reveal the absence of interatomic interaction for Dy³⁺ and Er³⁺ and weak ferromagnetic interaction for Ho³⁺. Thermal analysis shows good stability up to 365 °C for 2∞[Ho₂(3-PyPzH)₃Cl₆]·2MeCN.

Variable Luminescence and Chromaticity of Homoleptic Frameworks of the Lanthanides together with Pyridylpyrazolates

Homoleptic, 3D coordination polymers of the formula ³³ _∞ [Ln(3-PyPz)₃ ] and ³ _∞ [Ln(4-PyPz)₃ ], (3-PyPz)^- =3-(3-pyridyl)pyrazolate anion, (4-PyPz)^- =3-(4-pyridyl)pyrazolate anion, both C₈ H₆ N₃ ^- , Ln=Sm, Eu, Gd, Tb, Dy, were obtained as highly luminescent frameworks by reaction of the lanthanide metals (Ln) with the aromatic heterocyclic amine ligands 3-PyPzH and 4-PyPzH. The compounds form two isotypic series of 3D coordination polymers and exhibit fair thermal stability up to 360 °C. The luminescence properties of all ten compounds were determined in the solid state, with an antenna effect through ligand-metal energy transfer leading to high efficiency of the luminescence displayed by good quantum yields of up to 74 %. The emission is mainly based on ion-specific lanthanide-dependent intra 4 f-4 f transitions for Tb³⁺ : green, Dy³⁺ : yellow, Sm³⁺ : orange-red, Eu³⁺ : red. For the Gd³⁺ -containing compounds, the yellow emission of ligand triplet-based phosphorescence is observed at room temperature and 77 K. Co doping of the Gd-containing frameworks with Eu³⁺ and Tb³⁺ allow further shifting of the chromaticity towards white light emission.

Lanthanide coordination polymers based on designed bifunctional 2-(2,2':6',2″-terpyridin-4'-yl)benzenesulfonate ligand: syntheses, structural diversity and highly tunable emission

Seven novel lanthanide coordination polymers, [Eu(STP)(glu)]_n (1), [Ln₄(STP)₂(glu)₅]_n·4nH₂O [Ln = Er (2), Yb (3)], [Ln(STP)(1,3-bdc)]_n·0.5nH₂O [Ln = Tb (4), Yb (5)], and [Ln(STP)(1,2-bdc)]_n [Ln = Eu (6), Tb (7)] [NaSTP = sodium 2-(2,2':6',2″-terpyridin-4'-yl)benzenesulfonate, H₂glu = glutaric acid, H₂(1,3-bdc) = benzene-1,3-dicarboxylic acid, H₂(1,2-bdc) = benzene-1,2-dicarboxylic acid], have been prepared under hydrothermal conditions and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Compound (1) possesses a 2D layered structure based on 1D chains with STP^- and glu^2- anions acting as bridges. Compounds (2) and (3) are isomorphous and show a rare 3D tcj/hc net with a tetranuclear Ln³⁺ unit regarded as a seven-connected node and a glu^2- anion serving as a three-connected node. Compounds (4) and (5) are isomorphous and exhibit six-connected pcu nets by denoting binuclear units to six-connected nodes. Compounds (6) and (7) display 3D 3,5T1 nets with (1,2-bdc)^2- anions and dimetallic units serving as three- and five-connected nodes, respectively. The Eu compounds (1) and (6) demonstrate typically red emission, while the Tb compounds (4) and (7) exhibit characteristic green emission. The emission spectra of heteronuclear compounds [Eu_xTb_1-x(STP)(1,2-bdc)]_n (0 ≤ x ≤ 1) as efficient luminescent tags were investigated. The intermetallic energy transfer of Tb to Eu was also evaluated.

Four new metal–organic frameworks based on diverse secondary building units: sensing and magnetic properties

Four new metal–organic frameworks based on diverse secondary building units were assembled and 1 showed high selectivity in the detection of CrO₄²⁻, Cr₂O₇²⁻, MnO₄⁻ and Fe³⁺.

Highly selective luminescence sensing for the detection of nitrobenzene and Fe3+ by new Cd(ii)-based MOFs

Herein, three Cd(ii)-based MOFs were assembled, and the complex 3 showed a high selectivity in the detection of nitrobenzene and Fe³⁺.

Rational synthesis of a luminescent uncommon (3,4,6)-c connected Zn(ii) MOF: a dual channel sensor for the detection of nitroaromatics and ferric ions

A 3D (3,4,6)-c connected net constructed using a rigid tetracarboxylate ligand and sensing studies to detect nitroaromatics and ferric ion performed.

Five 1D to 3D Zn(ii)/Mn(ii)-CPs based on dicarboxyphenyl-terpyridine ligand: stepwise adsorptivity and magnetic properties

Five coordination polymers with different dimensional structures have been solvothermally synthesized by utilizing H₂dtp ligand. Complexes1and2reveal strong solid-state luminescence, and complexes3–5display antiferromagnetic exchange.

A Cu(ii) MOF with a flexible bifunctionalised terpyridine as an efficient catalyst for the single-pot hydrocarboxylation of cyclohexane to carboxylic acid in water/ionic liquid medium

A bifunctionalised terpyridine based Cu(ii) MOF for efficient hydrocarboxylation of cyclohexane to cyclohexanecarboxylic acid in an ionic liquid medium.

Lanthanide metal–organic frameworks based on a 1,2,3-triazole-containing tricarboxylic acid ligand for luminescence sensing of metal ions and nitroaromatic compounds

A series of novel 3D lanthanide MOFs based on unsymmetrical 1,2,3-triazole-containing tricarboxylic acid ligand (H3TAIP) has been synthesized. Compound 1 [Tb(TAIP)(DMF)₂] exhibits selective detection of 4-nitrotoluene and Fe³⁺ ion.

Alcohol-soluble bis(tpy)thiophenes: new building units for constitutional dynamic conjugated polyelectrolytes

Constitutional dynamics and spectral properties of conjugated ionic unimers and their metallo-supramolecular dynamers with Zn(ii) and Fe(ii) ion couplers are presented together with new knowledge on the MLCT band of bis(tpy)Fe(ii) units.

Synthesis of discrete Re(i) di- and tricarbonyl assemblies using a [4 × 1] directional bonding strategy

Discrete assembly of two Re(i) squares was achieved by a simple [4 × 1] strategy where the complexes, [Re(4-pytpy-κ²N)(CO)₃Br] and [Re(4-pytpy-κ³N)(CO)₂Br], act as their own ligands. The properties of the assemblies and their precursors are described along with solid-state X-ray diffraction studies.

A microporous lanthanum metal–organic framework as a bi-functional chemosensor for the detection of picric acid and Fe3+ ions

A novel microporous lanthanum metal–organic framework 1 was synthesized by using the rigid unsymmetrical tricarboxylate ligand H₃TPT. This compound exhibits selective detection of picric acid (PA) and Fe³⁺ ion.

Seven novel coordination polymers constructed by rigid 4-(4-carboxyphenyl)-terpyridine ligands: synthesis, structural diversity, luminescence and magnetic properties

Seven coordination polymers, namely [Mn(4-cptpy)2]n (1), [Co(4-cptpy)2]n (2), [Mn3(4-cptpy)6(H2O)]n·2nH2O (3), [Co(4-cptpy)(HCOO)(H2O)]n·nDMF (4), [Zn2(4-Hcptpy)2Cl4]n·2nC2H5OH·nH2O (5), [Co4(3-cptpy)4(HCOO)4(H2O)2]n (6), and [Mn(3-cptpy)2]n (7) (4-Hcptpy = 4-(4-carboxyphenyl)-4,2':6',4''-terpyridine; 3-Hcptpy = 4-(4-carboxyphenyl)-3,2':6',3''-terpyridine), have been synthesized under hydro(solvo)thermal conditions and structurally characterized. A general solvothermal method is proposed for preparing carboxylate complexes in DMF solution without any basic additive. 1 and 2 possess isostructural 3D metal-organic frameworks containing nanosized cavities. 3 is a beautiful 2D coordination polymer assembled by flower-like Mn3(4-cptpy)6(H2O) subunits. 4 and 6 both display 2D polymeric networks constructed from 4/3-cptpy(-) ligands, in which the formate ligands originate from the hydrolysis of DMF. 5 is a 1D 2(1) helical chain polymer. 7 shows a 2D network with a (3.6) two-nodal kgd topology. 4/3-Hcptpy ligands display seven types of coordination modes. The zinc complex 5 emits strong violet luminescence. 1 and 2 are both thermally stable below 440 °C and exhibit antiferromagnetic interactions.

A series of novel zinc(II) entangled coordination polymers based on carboxyphenyl-terpyridine ligands

Hydrothermal synthesis has afforded five divalent zinc coordination polymers containing 4-(4-carboxyphenyl)-2,2':6',2''-terpyridine (HL1) or its isomer 4-(4-carboxyphenyl)-2,2':4',4''-terpyridine (HL2), with or without the addition of auxiliary ligands, 1,3,5-benzenetricarboxylic acid (H3btc) and 1,4-benzenedicarboxylic acid (H2bdc). Their structures have been characterized by single crystal X-ray analyses and further characterized by infrared spectra, elemental analyses, powder X-ray diffraction, thermogravimetric analyses and photoluminescent spectra. Across this series, the π···π interactions have a dramatic impact on the self-assembly of these entanglement structures, in either case it can exert an important structure-directing role. In addition, the disposition of pyridine nitrogen atoms in ligands also plays a large role in structure direction in this system. Complex 1 is a 2D + 2D→3D inclined polycatenated coordination polymer based on the resulting array of 2D (6,3) layers constructed by 1D→2D π···π directed self-assembly. Complex 2 is assembled into a 3D framework by means of 1D + 1D→3D mutual interdigitation based on 1D→1D self-assembly driven by π···π stacking interactions. Complex 3 shows a 2D + 2D→3D interdigital network involving 2D + 2D→2D parallel interpenetrated and 2D + 2D→2D interdigital (4,4) layer motifs. Complex 4 displays a 2D + 2D→3D polythreaded framework based on a 2D (4,4) network comprised of alternating rings and rods. Complex 5 is a (3,4)-connected 3D framework with topology (4.8(2).10(3))(4.8(2)). In comparison with covalently connected entanglements, such π···π directing self-assembly of entanglements are far less explored, especially, polycatenane based on 1D chain motifs and polythread based on 2D layer motifs are rarely reported. Furthermore, the luminescent properties of complexes 1-5 at room temperature have also been studied in detail herein.

Fast response and high sensitivity europium metal organic framework fluorescent probe with chelating terpyridine sites for Fe³⁺

Iron is one of the most important elements in the metabolic process for all living system. However, both its deficiency and excess from normal permissible limits can induce serious disorders. We synthesized a europium-based metal-organic framework (Eu-MOF), EuL(3) (L = 4'-(4-carboxyphenyl)-2,2': 6',2″-terpyridine), under hydrothermal conditions, and used it as a solid luminescence sensor for Fe(3+) ions. The robust EuL(3) shows fast response (∼ 1 min) and high sensitivity (Stern-Volmer constant K(SV) = 4.1 × 10(3) L/mol) for Fe(3+) ions in aqueous solution or biological systems due to the existence of chelating terpyridine and open channels. The simple and portable test paper based on the EuL(3) fluorescent sensor system provides a convenient and reliable detection of Fe(3+) in every day applications. This pioneering work contributes to extend the potential application of Ln-MOFs to the biological and environmental areas.