Advance Progress on Luminescent Sensing of Nitroaromatics by Crystalline Lanthanide-Organic Complexes

Water environment pollution is becoming an increasingly serious issue due to industrial pollutants with the rapid development of modern industry. Among many pollutants, the toxic and explosive nitroaromatics are used extensively in the chemical industry, resulting in environmental pollution of soil and groundwater. Therefore, the detection of nitroaromatics is of great significance to environmental monitoring, citizen life and homeland security. Lanthanide-organic complexes with controllable structural features and excellent optical performance have been rationally designed and successfully prepared and used as lanthanide-based sensors for the detection of nitroaromatics. This review will focus on crystalline luminescent lanthanide-organic sensing materials with different dimensional structures, including the 0D discrete structure, 1D and 2D coordination polymers and the 3D framework. Large numbers of studies have shown that several nitroaromatics could be detected by crystalline lanthanide-organic-complex-based sensors, for instance, nitrobenzene (NB), nitrophenol (4-NP or 2-NP), trinitrophenol (TNP) and so on. The various fluorescence detection mechanisms were summarized and sorted out in the review, which might help researchers or readers to comprehensively understand the mechanism of the fluorescence detection of nitroaromatics and provide a theoretical basis for the rational design of new crystalline lanthanide-organic complex-based sensors.

Crystal structure of diaqua-diphenanthroline-κ2 N,N′-bis(μ2-2-carboxy-3,4,5,6-tetrafluorobenzoato-κ2 O:O′)-bis(μ2-tetrafluorophthalato-κ3 O,O′:O′)didysprosium(III) – phenanthroline (1/2), C80H38Dy2F16N8O18

C80H38Dy2F16N8O18, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 11.3924(5) Å, b = 12.7091(4) Å, c = 13.2583(5) Å, α = 102.496(3)°, β = 97.955(4)°, γ = 105.588(4)°, V = 1765.36(12) Å3, Z = 2, Rgt (F) = 0.0298, wRref (F 2) = 0.0606, T = 293(2) K.

Aliphatic-Bridged Early Lanthanide Metal–Organic Frameworks: Topological Polymorphism and Excitation-Dependent Luminescence

Six new three-dimensional metal–organic frameworks based on early lanthanide(III) cations and trans-1,4-cyclohexanedicarboxylic acid (H2chdc) were obtained. Their crystal structures were determined by single-crystal X-ray diffraction analysis. The structure of [La2(H2O)4(chdc)3]·2DMF·H2O (1; DMF = N,N-dimethylformamide) contains one-dimensional infinite La(III)-carboxylate chains interconnected by cyclohexane moieties to form a highly porous polymeric lattice with 30% solvent accessible volume. Compounds [Ln2(phen)2(chdc)3]·0.75DMF (2Ln; Ln3+ = Ce3+, Pr3+, Nd3+ and Sm3+; phen = 1,10-phenanthroline) are based on binuclear carboxylate building blocks, which are decorated by chelate phenanthroline ligands and interconnected by cyclohexane moieties to form more dense isostructural coordination frameworks with primitive cubic pcu topology. Compound [Nd2(phen)2(chdc)3]·2DMF·0.67H2O (3) is based on secondary building units similar to 2Ln and contains a coordination lattice isomeric to 2Ln with a rare hexagonal helical snz topology. Thermal stability and luminescent properties were investigated. For 2Sm, a strong and nonmonotonous dependence of the luminescence color on the variation of excitation wavelength was revealed, changing its emission from pinkish red at λex = 340 nm to white at λex = 400 nm, and then to yellow at lower excitation energies. Such nonlinear behavior was rationalized in terms of the contribution of several different luminescence mechanisms. Thus, 2Sm is a rather rare example of a highly tunable monometallic lanthanide-based luminophore with possible applications in light-emitting devices and optical data processing.

Crystal structure of diaqua-bis(μ2-2-carboxy-3,4,5,6-tetrafluorobenzoato-κ2 O:O′)-bis(phenanthroline-κ2 N,N′)-bis(μ2-3,4,5,6-tetrafluorophthalato-κ3 O:O,O′)dieuropium(III) – phenanthroline (1/2), C40H19EuF8N4O9

C40H19EuF8N4O9, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 11.3326(4) Å, b = 12.7652(4) Å, c = 13.2629(4) Å, α = 102.266(2)°, β = 97.689(2)°, γ = 105.630(3)°, V = 1767.93(10) Å3, Z = 2, R gt (F) = 0.0329, wR ref (F 2) = 0.0648, T = 293(2) K.

Synthesis, supramolecular isomerism, and photoluminescence of scandium(III) complexes with tetrafluoroterephthalate ligand

Here we present a new family of seven Sc(III) complexes with tetrafluoroterephthalate ligand (tFBDC2−), having non-polymeric and polymeric 2D and 3D structures. These complexes are characterized by SC XRD, PXRD,...

Molecular and Polymer Ln2M2 (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd) Complexes with Pentafluorobenzoate Anions: The Role of Temperature and Stacking Effects in the Structure; Magnetic and Luminescent Properties

Varying the temperature of the reaction of [{Cd(pfb)(H2O)4}+n·n(pfb)-], [Ln2(pfb)6(H2O)8]·H2O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)5(phen)]n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb2Cd2(pfb)10(phen)2] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln2Cd2 fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln2Zn2 [Ln2Zn2(pfb)10(phen)2]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd2Zn2(pfb)10(H2O)2(phen)2]·4MeCN (VII). A new molecular EuCd complex [Eu2Cd2(pfb)10(phen)4]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

Synthesis and crystal structure of a 6-chloro-nicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine

The title compound is a 6-chloro­nicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bi­pyridine. The nickel(II) ion in the polymeric cation is octa­hedrally coordinated by four water mol­ecule O atoms and by two 4,4′-bi­pyridine N atoms. The 4,4′-bi­pyridine ligands act as bridges, connecting the symmetry-related nickel(II) ions into polymeric chains along the b-axis direction. In the extended structure, these chains, the anions and the water mol­ecules of crystallization are assembled into a three-dimensional network via strong O—H⋯O and O—H⋯N hydrogen bonds

A 6-chloro­nicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bi­pyridine (4,4′-bpy), namely, catena-poly[[[tetra­aqua­nickel(II)]-μ-4,4′-bi­pyridine-κ²N:N′] bis­(6-chloro­nicotinate) tetra­hydrate], {[Ni(C₁₀H₈N₂)(H₂O)₄](C₆H₃ClNO₂)₂·4H₂O}_n or {[Ni(4,4′-bpy)(H₂O)₄](6-Clnic)₂·4H₂O}_n, (1), was prepared by the reaction of nickel(II) sulfate hepta­hydrate, 6-chloro­nicotinic acid and 4,4′-bi­pyridine in a mixture of water and ethanol. The mol­ecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4′-bpy)(H₂O)₄]²⁺}_n cation, two 6-chloro­nicotinate anions and four water mol­ecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octa­hedrally coordinated by four water mol­ecule O atoms and by two 4,4′-bi­pyridine N atoms in the trans position. The 4,4′-bi­pyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4′-bpy)(H₂O)₄]²⁺}_n, the 6-chloro­nicotinate anions and the water mol­ecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O—H⋯O and O—H⋯N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetra­meric R²₄(8) and R⁴₄(10) loops, a dimeric R²₂(8) loop and a penta­meric R⁴₅(16) loop.

The first coordination compound of 6-fluoro-nicotinate: the crystal structure of a one-dimensional nickel(II) coordination polymer containing the mixed ligands 6-fluoro-nicotinate and 4,4'-bi-pyridine

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro­nicotinate (6-Fnic) and 4,4′-bi­pyridine (4,4′-bpy), namely, [Ni(H₂O)₂(6-Fnic)₂(4,4′-bpy)·3H₂O]_n, (1), was prepared. The nickel(II) ion in 1 is octa­hedrally coordinated by the O atoms of two water mol­ecules, two O atoms from O-monodentate 6-fluoro­nicotinate ligands and two N atoms from bridging 4,4′-bi­pyridine ligands.

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro­nicotinate (6-Fnic) and 4,4′-bi­pyridine (4,4′-bpy), namely, catena-poly[[di­aqua­bis­(6-fluoro­pyridine-3-carboxyl­ato-κO)nickel(II)]-μ-4,4′-bi­pyri­dine-κ²N:N′] trihydrate], {[Ni(6-Fnic)₂(4,4′-bpy)(H₂O)₂]·3H₂O}_n, (1), was prepared by the reaction of nickel(II) sulfate hepta­hydrate, 6-fluoro­nicotinic acid (C₆H₄FNO₂) and 4,4′-bi­pyridine (C₁₀H₈N₂) in a mixture of water and ethanol. The nickel(II) ion in 1 is octa­hedrally coordinated by the O atoms of two water mol­ecules, two O atoms from O-monodentate 6-fluoro­nicotinate ligands and two N atoms from bridging 4,4′-bi­pyridine ligands, forming a trans isomer. The bridging 4,4′-bi­pyridine ligands connect symmetry-related nickel(II) ions into infinite one-dimensional polymeric chains running in the [10] direction. In the extended structure of 1, the polymeric chains and lattice water mol­ecules are connected into a three-dimensional hydrogen-bonded network via strong O—H⋯O and O—H⋯N hydrogen bonds, leading to the formation of distinct hydrogen-bond ring motifs: octa­meric R₈⁸(24) and hexa­meric R₈⁶(16) loops.

The crystal structure of [(tetra-μ 2-2,6-difluorobenzoato-κ 2 O:O′)-bis-(2,6-difluorobenzoato-κ 2 O:O′)-bis-(1,10-phenanthroline-κ 2 N:N′)]dierbium(III) C66H34N4O12F12Er2

C66H34N4O12F12Er2, triclinic, P1̄ (no. 2), a = 11.8934(5) Å, b = 12.0041(4) Å, c = 12.4578(5) Å, α = 68.718(4)°, β = 64.205(4)°, γ = 87.053(3)°, V = 1480.09(12) Å3, Z = 1, R gt(F) = 0.0326, wR ref(F 2) = 0.0626, T = 293(2) K.

Multi-functional lanthanide-CPs based on tricarboxylphenyl terpyridyl ligand as ratiometric luminescent thermometer and highly sensitive ion sensor with turn on/off effect

The binary compound Ln-CP Tb_0.897Eu_0.103tcptpy has been developed as a ratiometric luminescent thermometer. Its relative sensitivity can reach up to 8.41% K⁻¹ in the 305 to 340 K range.

A new binuclear NiII complex with tetrafluorophthalate and 2,2′-bipyridine ligands: synthesis, crystal structure and magnetic properties

A new NiII compound, [Ni2(tfpa)2(bipy)2(H2O)4] (1) with tetrafluorophthalate (tfpa2−) and 2,2′-bipyridine (abbreviated as bipy) ligands, has been synthesized and structurally characterized. The single-crystal X-ray diffraction analysis reveals that the tfpa2− anions act as bis-monodentate linkers connecting NiII centers to form the dinuclear structure of 1. The dimeric units are stabilized by intramolecular π–π stacking and are further connected into a layer through O–HLO hydrogen bonding. Variable-temperature magnetic susceptibility data in the 10–200 K temperature range indicate weak ferromagnetic coupling between the two NiII ions.

Tunable Light Emission and Multiresponsive Luminescent Sensitivities in Aqueous Solutions of Two Series of Lanthanide Metal-Organic Frameworks Based on Structurally Related Ligands

Two series of lanthanide metal-organic frameworks (Ln-MOFs) from two structurally related flexible carboxylate-based ligands were solvothermally synthesized. H₃L2 with additional -CH₂- group provides more flexibility and different coordination modes and conformations compared with H₃L1. As a result, 2-Ln MOFs are modulated from two-dimensional kgd of 1-Ln to three-dimensional rtl topological frameworks and further achieve enhanced chemical stability. The Eu- and Tb-MOFs exhibit strong fluorescent emission at the solid state because of the antenna effect of the ligands. Interestingly, the emissions can be tuned by simply doping Eu³⁺ and Tb³⁺ of different concentrations within the Eu _xTb_{1- x} MOFs. Notably, 2-Ln MOFs realize nearly white light emission by means of a trichromatic approach (red of Eu(III), green of Tb(III), and blue of the H₃L2 ligand). Furthermore, 2-Ln MOFs also exhibit water stability and demonstrate high selective and sensitive sensing activities toward Fe(III) and Cr(VI) in aqueous solutions. The results further highlight the importance of the ligand flexibility on tuning MOF structures with improved structural stability and ion-sensing properties.

Improved luminescence properties by the self-assembly of lanthanide compounds with a 1-D chain structure for the sensing of CH3COOH and toxic HS− anions

A family of lanthanide compounds has been explored and enhanced luminescence has been accomplished by doping method. A brand new and multifunctional fluorescence probe was developed, which was able to detect CH₃COOH and HS⁻ with different mechanisms.

Selectively detecting toluene and benzaldehyde by two stable lanthanide–organic frameworks as luminescent probes

Two stable lanthanide–organic frameworks as luminescent probes to sensitively detect for toluene and benzaldehyde through luminescent quenching.

Enhanced luminescence and tunable magnetic properties of lanthanide coordination polymers based on fluorine substitution and phenanthroline ligand

Lanthanide coordination polymers with F-substituted carboxylate tectonics and phenanthroline ligands exhibit emission from the visible to near-infrared region with long lifetime. Dy(iii) compounds show temperature dependent and field induced single molecule magnetism.

Hydrothermal assembly, structures, topologies, luminescence, and magnetism of a novel series of coordination polymers driven by a trifunctional nicotinic acid building block

In this work, a trifunctional N,O-building block, 5-(4-carboxyphenoxy)nicotinic acid (H₂cpna), that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether) was used for the hydrothermal assembly of thirteen new coordination compounds: [Co(μ₃-Hcpna)₂]_n (1), [Mn(μ₄-cpna)(H₂O)]_n (2), [Mn(μ₄-cpna)(H₂O)₂]_n (3), [Mn(μ-cpna)(2,2'-bipy)(H₂O)₂]_n (4), {[Ni(μ₃-cpna)(2,2'-bipy)(H₂O)]₂·H₂O}_n (5), {[Cd(μ₃-cpna)(2,2'-bipy)]·2H₂O}_n (6), [Zn₂(μ-cpna)₂(2,2'-bipy)₂] (7), [Cu(μ-cpna)(2,2'-bipy)(H₂O)]_n (8), {[Mn(μ-cpna)(phen)₂]·6H₂O}_n (9), {[Ni(μ₃-cpna)(phen)(H₂O)]·H₂O}_n (10), [Zn₂(μ-cpna)₂(phen)₂] (11), {[Pb(μ₃-cpna)(phen)]·H₂O}_n (12), and [Ni(μ₃-cpna)(4,4'-bipy)_0.5(H₂O)]_n (13). These products were synthesized from the corresponding metal(ii) chlorides, H₂cpna, NaOH, and optional N-donor supporting ligands or templates {bis(4-pyridyl)amine (bpa), 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), or 1,10-phenanthroline (phen)}. Products 1-13 were characterized in the solid state by standard methods, including elemental and thermogravimetric analysis (TGA), IR spectroscopy, and powder (PXRD) and single-crystal X-ray diffraction. The structures of 1-13 feature distinct structural types, namely the 3D metal-organic frameworks (MOFs 1-3), the 2D coordination polymers (5, 6, 10, 12, and 13), the 1D coordination polymers (4, 8, and 9), and the 0D discrete cyclic dimers (7 and 11). Such a wide structural diversity of 1-13 is driven by various factors, including the type of the metal(ii) node, the deprotonation degree of H₂cpna, and/or the type of supporting ligand or template. Notably, an addition of bpa can tune the structure of MOF 3 by the template effect. Topological classification of underlying metal-organic networks was performed, leading to several distinct topological nets: rtl (in 1), hxg-d-4-C2/m (in 2), sra (in 3), 2C1 (in 4, 8 and 9), fes (in 5, 10, and 12), hcb (in 6), and 3,4L83 (in 13). The magnetic behavior of 1-5, 8-10, and 13 was studied and theoretically modeled, disclosing antiferromagnetic interactions. The luminescence behavior of 6, 7, 11, and 12 was also investigated.

Remarkable high efficiency of red emitters using Eu(iii) ternary complexes

We have synthesized Eu(iii) ternary complexes possessing record photoluminescence yields up to 90%. This high luminescence performance resulted from the absence of quenching moieties in the Eu coordination environment and an efficient energy transfer between ligands, combined with a particular symmetry of the coordination environment.

Lanthanide-MOFs constructed from mixed dicarboxylate ligands as selective multi-responsive luminescent sensors

Five novel Ln-MOFs associated with the mixed ligands of 4-(pyridin-3-yloxy)-phthalic acid (H₂ppda) and terephthalic acid (H₂bdc), namely, [Ln(ppda)(bdc)_0.5(C₂H₅OH)(H₂O)]_n (Ln = Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)) were synthesized under the solvothermal conditions. Compounds 1-5 exhibit the isostructural 2D layered structures. The solid-state luminescence properties of compounds 1, 2, 4 and 5 were investigated in detail. It was found that compound 4 not only detected nitrobenzene derivatives-based explosives with high selectivity, sensitivity, and recyclability, but also served as an excellent selective sensing material for Fe³⁺ ion and Cr₂O₇^2- ion. In particular, it is worth noting that the detection limit of TNP can reach 3.0 × 10^-8 M. It was found that the free oxygen atoms of the ether bond, which function as the Lewis basic sites in Ln-MOFs, might interact with metal ions. In addition, the sensing mechanisms of 4 for different analytes were explored further.

Five transition metal coordination polymers driven by a semirigid trifunctional nicotinic acid ligand: selective adsorption and magnetic properties

Five coordination polymers have been synthesized by a new organic linker containing three distinct types of functional groups together with the mixed 2,2′-bipy or 4,4′-bipy co-ligand, revealing various framework structures and selective gas adsorption and magnetic properties.

Bringing 5-(3,4-dicarboxylphenyl)picolinic acid to crystal engineering research: hydrothermal assembly, structural features, and photocatalytic activity of Mn, Ni, Cu, and Zn coordination polymers

A novel tricarboxylic acid block with phthalate and picolinate functionalities was applied for the assembly of a new series of coordination polymers with interesting structural features and functional properties.

Efficient pure white light emission based on a three-component La:Eu,Tb-doped luminescent lanthanide metal–organic framework

A three-component Eu and Tb-doped La complex based on a semirigid tricarboxylate ligand is successfully constructed with high-efficiency white light emission (Φ = 11.22% at 345 nm).

Syntheses, structures, luminescence and magnetic properties of seven isomorphous metal–organic frameworks based on 2,7-bis(4-benzoic acid)-N-(4-benzoic acid)carbazole

Seven isomorphous lanthanide metal–organic frameworks with special luminescence and magnetic properties are synthesized and characterized.

Luminescence and white-light emitting luminescent sensor of tetrafluoroterephthalate-lanthanide metal–organic frameworks

H₂TFBDC lanthanide complexes emitting white light was synthesized and a luminescent sensor for the detection of benzaldehyde has been produced.

Synthesis and structure of color tunable and white-light emitting lanthanide metal–organic framework materials constructed from conjugated 1,1′-butadiynebenzene-3,3′,5,5′-tetracarboxylate ligand

Seven isostructural lanthanide MOFs based on 1,1′-butadiynebenzene-3,3′, 5,5′-tetracarboxylate ligands were synthesized. Color tunable and white-light emitting materials were achieved by carefully adjusting the doping concentration of Eu³⁺ and Tb³⁺ in the Gd³⁺ compound.

Inorganic–organic hybrid white light phosphors

This feature article reviews the development of inorganic–organic hybrid white-light phosphors for the applications on light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs).

Lanthanide-based metal–organic frameworks as luminescent probes

We discuss the construction of lanthanide-based metal–organic frameworks, their applications in possible detection mechanisms, and summarize some examples of Ln-MOFs as luminescent probes.