Solid-state Luminescent Spectra Research Articles

Two unique M-MOFs (M:Zn, Mn) based on various metal-oxygen chains for good sensitivity sensing and magnetic properties

In this paper, two novel two-dimensional MOFs were synthesized by solvothermal reaction of 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid ligand and Zn(Ⅱ) and Mn(Ⅱ) metal ions: {[Zn2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (1), {[Mn2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (2). Complexes 1 and 2 are unique two-dimensional skeletons with particular metal-oxygen chains in their structures. The solid-state luminescence spectrum of complex 1 shows that its maximum emission peak is 448 nm. Further fluorescence studies of complex 1 show that it can efficiently detect Fe3+ and Cr2O72− in aqueous solution with a detection limit of 4.1 × 10−4 M and 2.7 × 10−4 M respectively, and has good recycling performance, so it is a potential bifunctional fluorescent probe material. The mechanism of fluorescence sensing quenching was also investigated in detail. Furthermore, magnetic studies have shown that there is an antiferromagnetic interaction between Mn(II) ions of complex 2.

Origin of the solid-state luminescence of MIL-53(Al) and its connection to the local crystalline structure

Metal-organic frameworks (MOFs) are extensively studied due to their unique surface properties, enabling many intriguing applications. Breathing MOFs, a subclass of MOFs, have gained recent interest for their ability to undergo structural changes based on factors like temperature, pressure, adsorbed molecules. Certain MOFs also exhibit remarkable optical properties useful for applications such as sensors, light-emitting diodes, and scintillators. The most promising MOFs possess high porosity, breathing properties, and photoluminescence activities, allowing for improved device responsiveness and selectivity. Understanding the relationship between crystal structures and photoluminescence properties is crucial in these cases. As studies on this topic are still very limited, we report for the first time an exhaustive study on the solid-state luminescence of the breathing MOF MIL-53(Al), that can stabilize in three different crystalline structures: open-pore, hydrated narrow-pore and closed-pore. We unveil a fascinating solid-state luminescence spectrum, comprising three partially overlapping bands, and elucidate the intricate electronic transitions within each band as well as their intimate correlation with the local crystalline structures. Our characterizations of spectroscopic properties and decay times provide a deeper understanding of the luminescent behaviour of MIL-53(Al) and demonstrate that is possible to identify present crystalline structures by optical measurements or to modify the optical properties inducing structural transitions for this type of materials. These insights could help to design next-generation, selective sensors or smart light emitting devices.

Crystal structure and luminescence spectrum of a one-dimensional nickel(II) coordination polymer incorporating 1,4-bis-[(2-methyl-imidazol-1-yl)meth-yl]benzene and adamantane-1,3-di-carboxyl-ate co-ligands.

An NiII coordination polymer, namely, poly[(μ2-adamantane-1,3-di-carboxyl-ato-κ4 O 1,O 1':O 3,O 3')[μ2-1,4-bis-(2-methyl-imidazol-1-ylmeth-yl)benzene-κ2 N 3:N 3']nickel(II)], [Ni(C12H14O4)(C16H18N4)]n or [Ni(adc)(bmib)]n, (I) [adc = adamantane-1,3-di-carboxyl-ate, C12H14O4 2- and bmib = 1,4-bis-(2-methyl-imidazol-1-ylmeth-yl)benzene, C16H18N4] was synthesized and characterized. It exhibits a one-dimensional extended structure built up from alternating [Ni2(bmib)2] 26-membered rings and [Ni2(adc)2] 16-membered rings. The nickel atom lies on a crystallographic twofold axis and both ligands are completed by mirror symmetry. The solid-state luminescence spectra of (I) and the bmib ligand show strong emissions at 442 and 410 nm, respectively.

Five new luminescent Pb(II) and Ag(I) coordination polymers based on 1-(4-carboxybenzyl)-1H-pyrazole-3,5-dicarboxylic acid and different neutral ligands

Five new coordination polymers (CPs), namely {Pb1.5(L)} (1), {Pb3(L)2(2,2′-bpy)·2·5H2O} (2), {[Pb(HL)(phen)]·H2O} (3), {Ag2(HL)} (4) and {Ag(H2L)(phen)} (5), have been constructed by using 1-(4-carboxybenzyl)-1H-pyrazole-3,5-dicarboxylic acid (H3L) as an organic ligand. Compound 1 reveals a three-dimensional (3D) (4,6,7)-connected framework with the point symbol of {410·65}{46}2{48·613}2. Compound 2 exhibits a novel (3,6)-connected 3D framework based on a trinuclear Pb(II) cluster with point symbol {42.6}2{44.62.88.10}. Compound 3 is a 1D chain that is further assembled into a 3D supramolecular framework by hydrogen-bonds. Compound 4 shows a (3,6)-connected 3D structure based on a tetranuclear Ag(I) cluster with {4·62}2{42·610·83} topology. Compound 5 is a 0D structure, and can be further expanded into a 3D supramolecular network by various weak interactions. The solid-state luminescent spectra have been measured at room temperature. The results show that compounds 1–5 exhibit strong luminescent emission in the visible region, and can be tunable by varying excitation wavelengths.

Two unique 2D metal-organic frameworks based on various metal-oxygen chains for high sensitivity sensing of Fe(III) and Cr(VI) in aqueous media

Two new 2D MOFs, namely, {[Cd2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (1), {[Co2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (2) were constructed under the solvothermal conditions by using 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid and d10 metal ion Cd(Ⅱ) and Co(Ⅱ). Because the diversity of ligands leads to two different coordination patterns in complexes 1–2, resulting in 1 and 2 with multiple structures. Both 1 and 2 exhibit a 3D supramolecular framework, which based on different metal-oxygen chains. The chains form a 2D layered structure through the carboxyl oxygen atoms in the ligand. The solid-state luminescence spectra of 1 at room temperature showed that the maximum emission peak is 458 nm (λex = 346 nm). At the same time, 1 showed high fluorescence selectivity and low detection limit for Fe3+ cations, Cr2O72− and CrO42− anions in aqueous solution, and can be used as a potential multifunctional material for the detection of these substances. In addition, the fluorescence sensing properties and quenching mechanism of the above ions are discussed in detail.

A new inorganic-organic hybrid based on γ-octamolybdate constructed from in situ decarboxylation reaction

A new inorganic-organic hybrid based on γ-[Mo8O26]4–, [Zn(H2O)2(H2PIDC)2][(Mo8O26)(HPIM)2]·8H2O (1), (H2PIDC = 2-(pyridine-3-yl)-1H-imidazole-4,5-dicarboxylic acid; PIM = 2-(pyridine-3-yl)-imidazole), has been synthesized and structurally characterized by X-ray single-crystal diffraction. PIM was synthesized through in situ decarboxylation reaction from H2PIDC. The two five-coordinated Mo atoms of γ-[Mo8O26]4– are coordinated with two HPIM+ forming a [(Mo8O26)(HPIM)2]2− unit. [Zn(H2O)2(H2PIDC)2]2+ units and [(Mo8O26)(HPIM)2]2− units are linked into a 3D supramolecular structure by noncovalent interactions. The Hirshfeld surface analyses indicates that hydrogen bonding interactions are the dominant interactions in 1. The solid-state luminescence spectrum of compound 1 at room temperature was investigated (λem = 395 nm). We have also studied the cyclic voltammograms and the electrocatalytic reduction of KNO2 of 1-CPE.

Solvent effects on the luminescent properties based on bis(hydroxy-naphthoic acid): Syntheses, crystal structure and Hirshfeld analysis

A set of novel compounds based on bis(hydroxyl-naphthoic acid), namely, B26·G [G = N,N-dimethyl formamide (1), N,N-dimethyl acetamide (2), and N-methyl pyrrolidone (3) (B26= 5,5′-methylene bis(6-hydroxy-2-naphthoic acid) were obtained through the solvent evaporation method, respectively. The title compounds 1-3 have been characterized by IR, UV–Vis, element analysis (EA), single crystal X-ray diffraction, and powder X-ray diffraction (PXRD). In these compounds, a plenty of C/O–H⋯O hydrogen bonds can be obviously obtained. There exist trans- and cis-conformation for two naphthoic carboxylic moieties. The host B26 frameworks show the feature of nonporous adaptive compound enclathrating different guest molecules. The solid-state luminescent spectra of 1-3 show that the emission maxima are observed at 432, 393 and 388 nm, respectively. The decay lifetimes can be found to be 0.42, 0.44 and 0.36 ns for compounds 1-3, respectively. Additionally, the quantum yields of compounds 1-3 are 0.02%, 8.76% and 6.74%, respectively. The Hirshfeld surface analysis reveals that the order of the C···H/H···C and C···C closes contact is in a good agreement with that of the luminescent peaks. The experiment of solvent exchange reveals that the B26 host framework shows low crystal-state stability. Additionally, the thermal behaviors of compounds 1-3 have been discussed in detail.

Design of Dinuclear Lanthanide Complexes from N2O2 Donor Ligand for Single Molecule Magnets: Crystalline Architecture and Slow Magnetic Relaxation Studies

AbstractThree new dinuclear lanthanide complexes [Ln2L2(μ2‐benzoate)2(MeOH)2] ⋅ 4MeOH (H2L=2‐Bis(2‐hydroxybenzyl)aminomethyl]pyridine); Ln=Nd (1), Tb (2), Dy (3)) have been synthesized and structurally characterized by single‐crystal X‐ray diffraction analyses. Compounds 1, 2 and 3 are isomorphous and thus the framework connectivity features are the same for all the three compounds. In the dimeric form of the complexes, each metal centre is octacoordinated with square antiprism (D4d symmetry) geometry, which is completed by a coordinated methanol molecule. In addition, the methanol that present in the structural voids also acts as linkers of paddle‐wheel like complexes. Magnetic properties of the compounds have been investigated in detail using direct‐current and alternating‐current susceptibility measurements. From the analysis of all three complexes, the decrease of susceptibility value at low temperatures is due to the depopulation of Stark sublevels and the existence of intramolecular antiferromagnetic interactions. In addition, complex 3 shows slow relaxation of magnetization behavior, a characteristic feature of single molecule magnets (SMMs). An effective energy barrier value (Ueff) of 38.87 K and relaxation time (τ0) of 1.665×10−7 s for the magnetic relaxation process was obtained for 3. Solid state luminescence spectra for complex 2 show characteristic green emission peaks at 543 nm region having potential for applications in the solid state as light emitting diodes and photoluminescent materials.

The substituent effect on the luminescent properties of a set of 4-amino-4-1,2,4-triazole: Syntheses, crystal structures and Hirshfeld analyses

• Three 4-amino-4 H -1,2,4-triazole have been obtained. • Their crystal state structures were characterized by single crystal X–ray diffraction. • The luminescent properties can be meditated by the substituted groups. • The emission peaks are proporational to the intermolecular contacts. A set of compounds based on 4-amino-4 H -1,2,4-triazole group, namely, 4,4′-(4-amino-4H-1,2,4-triazole-3,5-diyl)dibenzoic acid ( 1 ), 4,4′-(4-amino-4H-1,2,4-triazole-3,5-diyl)dianiline ( 2 ), 4,4′-(4-amino-4 H -1,2,4-triazole-3,5-diyl)diphenol ( 3 ), were obtained through reacting different aromatic nitrile and hydrazine under the solvothermal conditions, respectively. The title compounds 1–3 have been characterized by IR, UV–Vis, 1 H NMR, 13 C NMR, element analysis (EA), single crystal X-ray diffraction, and powder X-ray diffraction (PXRD). In these compounds, a plenty of hydrogen bonds (C/N–H⋯O/N) and C H∙∙∙π can be obviously obtained, through which a three-dimensional framework will be constructed. The solid-state luminescent spectra of 1 – 3 show that the emission maxima are observed at 398, 464 and 402 nm, respectively. The order of maximal peaks is 1<3<2 . The Hirshfeld surface analyses confirm that the order of the contribution of C∙∙∙H/H∙∙∙C and H∙∙∙H contacts is 1<3<2 , which is in a good accordance with that of the luminescent bands.

The position of NH2-subsituted group controlled the luminescent properties based on 4-amino-4H-1,2,4-triazole: Syntheses, crystal structures and Hirshfeld analyses

The tunable photoluminescent materials has drawn extensive attention in recent years. The position of the substituents tuned the luminescent materials are one of attractive methods. Herein, we present a feasible and facile strategy to achieve a 4-amino-1,2,4-1H-triazole-based organic materials. A set of compounds based on 4-amino-4H-1,2,4-triazole group, namely, x,x'-(4-amino-4H-1,2,4-triazole-3,5-diyl)dianiline [x ​= ​2 (1), x ​= ​3 (2), x ​= ​4 (3)] (the formulas are C14H14N6, C14H14N6 and C14H16N6O for compounds 1–3, respectively), were obtained. The title compounds 1–3 have been characterized by IR, UV–Vis, element analysis (EA), single crystal X-ray diffraction, and powder X-ray diffraction (PXRD). In these compounds, a plenty of hydrogen bonds (C/N–H⋯O/N) and C–H … π can be obviously found. The order of the packing interactions is represented as the following: 2 ​> ​3>1. The Hirshfeld surface analyses reveal that the contribution order of the H⋯H bond contacts in compounds 1–3 is listed: 2 ​> ​3>1, which is in a good agreement with that of the stacking interactions. The solid-state luminescent spectra of 1–3 show that the emission maxima are observed at 404, 377 and 457 ​nm, respectively, where the order of the peaks is represented as 3 ​> ​1>2. The Hirshfeld surface analyses show that the contribution order of the C⋯H/H⋯C close contacts is listed: 3 ​> ​1>2, which is in a good accordance with that of the fluorescent maxima.

Luminescent properties of activated forms of rigid ligand Cd(II)-coordination polymers sustained by hydrogen bond

Two new Cd(II) coordination polymers namely {[Cd(BTC)(H2O)]∙0.5HBimb·2H2O}n(1) and{[Cd2(CH3COO)4(4,4′-dpy)2]∙H2O}n(2) were synthesized using an extremely versatile imidazole-based N-donor ligand,1,4-bis[(1H-imidazol-1-yl)methyl]benzene (Bimb), rigid 1,3,5-Benzenetricarboxylic acid (H3BTC) and 4,4′-dipyridyl (4,4′-dpy) with different metal salt at different temperatures. Elemental analysis, Variable Temperature Photoluminescence, and thermal stability were used to characterize both coordination polymers. The single crystal analysis reveals that (1) is an anionic framework in which charge neutrality is compansated by H2Bimb+2 ions, where as (2) is a neutral complex. The OH⋯O hydrogen bonding helps in elevation of dimensionality from 1D coordination chain to 2D architectures in both the complexes. The solid-state luminescence spectra of as synthesized and activated forms (90 °C, 180 °C and 300 °C) for complexes (1) and (2) were recorded at 350 nm and 330 nm as excitation wavelength respectively. The activated forms reflect strong blue luminescence with the peak maximum in the range of 391–390 nm (3.1710–3.1791 eV) for complex (1) and for complex (2) it is at396-399 nm (3.1309–3.1074 eV). Thermogravimetric analysis reveals that both are contented with good thermal stability.

Diverse Coordination Numbers and Geometries in Pyridyl Adducts of Lanthanide(III) Complexes Based on β-Diketonate

Ten mononuclear rare earth complexes of formula [La(btfa)3(H2O)2] (1), [La(btfa)3(4,4′-Mt2bipy)] (2), [La(btfa)3(4,4′-Me2bipy)2] (3), [La(btfa)3(5,5′-Me2bipy)2] (4), [La(btfa)3(terpy)] (5), [La(btfa)3(phen)(EtOH)] (6), [La(btfa)3(4,4′-Me2bipy)(EtOH)] (7), [La(btfa)3(2-benzpy)(MeOH)] (8), [Tb(btfa)3(4,4′-Me2bipy)] (9) and (Hpy)[Eu(btfa)4] (10), where btfa = 4,4,4-trifuoro-1-phenylbutane-1,3-dionato anion, 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-bipyridine, 4,4′-Me2bipy = 4,4′-dimethyl-2,2′-bipyridine, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-bipyridine, terpy = 2,2′:6′,2′-terpyridine, phen = 1,10-phenathroline, 2-benzpy = 2-(2-pyridyl)benzimidazole, Hpy = pyridiniumH+ cation) have been synthesized and structurally characterized. The complexes display coordination numbers (CN) eight for 1, 2, 9, 10, nine for 5, 6, 7, 8 and ten for 3 and 4. The solid-state luminescence spectra of Tb-9 and Eu-10 complexes showed the same characteristic bands predicted from the Tb(III) and Eu(III) ions. The Overall Quantum Yield measured (ϕTOT) at the excitation wavelength of 371 nm for both compounds yielded 1.04% for 9 and up to 34.56% for 10.

Coupling strong photoluminescence and narrow band gap in a new tetranuclear copper cluster: Copper(I) iodide with dimethylamine

A novel tetranuclear Cu4I4 - organic amine cluster was synthesized, which was involved dimethylamine and cuprous iodide by hydrothermal, [C2H7N]4·Cu4I4 (1). The structure of compound 1 was determined by single crystal X-ray diffraction analysis and further characterized by elemental analysis, infrared spectroscopy, luminescence spectrum, powder X-ray diffraction, and thermogravimetric analysis. The result of solid-state luminescence spectrum testing of compound 1 displays strong yellow-light emission with λmax = 595 nm at room temperature, suggesting that compound 1 may be a good yellow light-emitting material. Specially, compound 1 exhibits a narrow band gap of 2.182 eV in semiconductor property and is chiefly contributed by inorganic Cu4I4 of [C2H7N]4·Cu4I4. These findings will contribute to an alternative pathway for exploring and developing novel fluorescence and semiconducting materials of the coordination compounds and related properties in other materials.

The hydroxylic position mediated the luminescent properties based on 4-amino-4H-1,2,4-triazole: Syntheses, crystal structures and Hirshfeld analyses

A set of compounds based on 4-amino-4H-1,2,4-triazole group, namely, x,x'-(4-amino-4H-1,2,4-triazole-3,5-diyl) diphenol [x ​= ​2 (1), x ​= ​3 (2), x ​= ​4 (3)], were obtained through reacting a set of cyano-phenol and hydrazine under the solvothermal conditions, respectively. The title compounds 1–3 have been characterized by IR, element analysis (EA), single crystal X-ray diffraction, and powder X-ray diffraction (PXRD). A lot of hydrogen bonds (C/N/O–H⋯O/N) and C–H … π can be clearly observed in these compounds. It surprisedly occurs the presence of trans- and cis-conformation for compounds 3. The increasing order of the dihedral angles between the phenyl and triazole-yl rings is 1 ​< ​2<3. The solid-state luminescent spectra of 1–3 show that the emission maxima are observed at 461, 414 and 402 ​nm, respectively, which shows the declining order of 1 ​> ​2>3. The luminescent maximal peaks decrease with the diminution of hydroxylic steric effects. The Hirshfeld surface analyses reveal that the contribution order of the O⋯H/H⋯O contacts in compounds 1–3 is listed: 1 ​< ​2<3, which is in a good agreement with that of the dihedral angles, and an inverse proportional to the fluorescent maxima of compounds 1–3.

Two coordination polymers constructed by 5-[(4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylic acid and 2,2'-bipyridine: syntheses, structures and luminescence properties.

Coordination polymers (CPs) have attracted increasing interest in recent years. In this work, two new CPs, namely poly[[aquabis(2,2'-bipyridine-κ2N,N'){μ3-5-[(4-carboxylatophenoxy)methyl]benzene-1,3-dicarboxylato-κ4O1,O1':O3:O5}(μ-formato-κ3O:O,O')dicadmium(II)] monohydrate], {[Cd2(C16H9O7)(HCO2)(C10H8N2)2(H2O)]·H2O}n (1), and poly[[(2,2'-bipyridine-κ2N,N'){μ3-5-[(4-carboxylphenoxy)methyl]benzene-1,3-dicarboxylato-κ4O1,O1':O3:O5}manganese(II)] sesquihydrate], {[Mn(C16H10O7)(C10H8N2)]·1.5H2O}n (2), have been prepared using the tricarboxylic acid 5-[(4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylic acid and 2,2'-bipyridine under hydrothermal conditions. CP 1 displays a two-dimensional layer structure which is further extended into a three-dimensional (3D) supramolecular structure via intermolecular π-π interactions, while CP 2 shows a different 3D supramolecular structure extended from one-dimensional ladder chains by intermolecular π-π interactions. In addition, the solid-state luminescence spectra of 1 and 2 were studied at room temperature.

A Series of 3D Porous Lanthanide-Substituted Polyoxometalate Frameworks Based on Rare Hexadecahedral {Ln6W8O28} Heterometallic Cage-Shaped Clusters.

A series of 3D porous lanthanide-substituted polyoxometalate frameworks, Na2[Ln2(H2O)11]2[Ln3(H2O)3(α-SiW11O39)2]2·69H2O (1-Ln, Ln = Sm, Eu, Gd, Tb, and Dy), are built from novel hexadecahedral {Ln6W8O28} heterometallic cage-shaped clusters. Intriguingly, every tetrameric {[Ln3(H2O)3(α-SiW11O39)2]2}14- cage-cluster is linked with another eight tetrameric cage-clusters by Ln3+ cations, leading to a novel 3D inorganic porous framework, which exhibits good thermal and chemical stability, excellent water vapor adsorption capacity, and moderate proton conductive properties. Furthermore, the solid state luminescence spectra demonstrate that 1-Sm, 1-Eu, 1-Tb, and 1-Dy display the lanthanide characteristic emission bands. The temperature-dependent magnetic susceptibility indicates that there are antiferromagnetic interactions in 1-Tb and 1-Dy.

A new photoluminescent terbium(III) coordination network constructed from 1,2,4,5-benzenetetracarboxylic acid: Synthesis, structural characterization and application as a potential marker for gunshot residues

A novel terbium(III) coordination network (CN) of formula [TbHbtec]n1, constructed from 1,2,4,5-benzenetetracarboxylic acid (H4Btec) and Tb3+ ions, has been obtained under hydrothermal conditions. Single crystal X-ray diffraction and topological studies revealed the crystal structure of CN 1 involves a cubic primitive network with topology pcu-αPo, uninodal and with point symbol (412. 63). In the crystal structure, the ligand is monoprotonated (Hbtec3−) with six Hbtec3− adopting the monodentate, bidentate chelating and bidentate chelating-bridging coordination modes, leading to the formation of a 3-D coordination network. Solid state luminescence spectrum showed the characteristic 5D4 → 7FJ (J = 6–2) transitions of the Tb3+ ion upon excitation in the Hbtec3− singlet levels, revealing that the ligand Hbtec3− is a good sensitizer for the intense green emission of Tb3+ ions. Thermogravimetric analysis (TGA) showed CN 1 has exceptional thermal stability decomposing at temperatures higher than 470 °C. Taking advantage of its excellent thermal and optical properties, the [TbHbtec]n was tested as luminescent marker for gunshot residues, opening the possibility of using this compound in forensic analysis of crime scenes.

Flux Synthesis, Monoclinic Structure, and Luminescence of Europium(III)‐Doped K3La(PO4)2

AbstractSingle crystals of potassium lanthanum orthophosphate are prepared from high‐temperature melts containing potassium molybdate as a flux and structurally investigated by single‐crystal X‐ray diffraction. The framework is shown to be constructed from isolated LaO7 monocapped prisms and PO4 tetrahedra through corner‐ and edge‐sharing giving rise to 2D sheets with composition [La(PO4)2]3−. Three types of potassium cations reside between these layers. For the solid solutions K3La1−xEux(PO4)2 (x = 0.1–0.9) prepared by the solid‐state route, the excitation and emission luminescence spectra are studied at room temperature. The emission spectra exhibit strong reddish performance, which is due to the 5D0→7FJ transitions of Eu3+ ions. The correlation between the structure and the photoluminescent properties of the phosphors is studied. The energy transfer and concentration quenching of the phosphors are discussed. Solid solutions K3La1−xEux(PO4)2 have a potential application for white‐light‐emitting diodes.

Unprecedented Selenium and Lanthanide Simultaneously Bridging Selenotungstate Aggregates Stabilized by Four Tetra-vacant Dawson-like {Se2 W14 } Units.

In the presence of the larger [H2 N(CH3 )2 ]+ and K+ counter cations as structure-stabilizing agents, a class of unprecedented selenium and lanthanide (Ln) simultaneously bridging tetra-vacant Dawson-like selenotungstate aggregates [H2 N(CH3 )2 ]2 Na9 K2 H19 {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }2 ⋅60 H2 O [Ln=TbIII (1), DyIII (2), HoIII (3), ErIII (4), TmIII (5), YbIII (6)] have been obtained by the one-pot assembly reaction of Na2 WO4 ⋅2 H2 O, Ln(NO3 )3 ⋅6 H2 O, and Na2 SeO3 under moderately acidic aqueous conditions and the complexes were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. It should be noted that the appropriate molar ratio of Se/W is extremely important in the formation of 1-6 and can effectively ameliorate the yield of 1-6. Moreover, dimethylamine hydrochloride is also indispensable and plays a considerably important role in improving the solubility of Ln ions and stabilizing the structures of 1-6. The main polyoxoanion skeletons of 1-6 are constructed from two sandwich-type tetra-vacant Dawson-like {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }16- half-units linked through two W-O-Ln bridges. The sandwich-type half-unit comprises two tetra-vacant Dawson-like [Se2 W14 O52 ]12- fragments encapsulating a unique dodecanuclear Se-Ln-W [Ln4 W4 Se4 O22 (H2 O)5 ]8+ oxo cluster. Their solid-state visible and NIR fluorescent properties and lifetime decay behaviors were measured and their solid-state luminescent spectra mainly demonstrate the characteristic emission bands of Ln3+ ions. Moreover, the dominant wavelengths, the color purity, and correlated color temperatures of 1-5 have been also calculated. In addition, the luminous flux values of 1-5 are 2031, 6992, 3071, 921, and 477 lumen, respectively.

RE-p-halobenzoic acid–terpyridine complexes, Part II: structural diversity, supramolecular assembly, and luminescence properties in a series of p-bromobenzoic acid rare-earth hybrid materials

Twenty-four new rare-earth p-bromobenzoic acid complexes, [RE(L1)3(L2)(H2O)]2 (RE = La3+ (1), Ce3+ (2), Pr3+ (3), Nd3+ (4)), [RE(L1)3(L2)(H2O)]2 (RE = La3+ (1′), Ce3+ (2′), Pr3+ (3′), Nd3+ (4′)), [RE(L1)3(L2)]2·H2O (RE = Sm3+ (5), Eu3+ (6), Gd3+ (7), Tb3+ (8)), RE(L1)3(L2)(H2O) (RE = Gd3+ (7′), Tb3+ (8′), Dy3+ (9), Ho3+ (10), Er3+ (11), Tm3+ (12), Yb3+ (13), Lu3+ (14), Y3+ (15)), and RE2(L1)4(L2)2(Ox) (RE = Tm3+ (12′), Yb3+ (13′) Lu3+ (14′)); L1: p-bromobenzoic acid; L2: 2,2′:6′,2′′-terpyridine; Ox: oxalic acid, have been hydrothermally synthesized and structurally characterized by single crystal and powder X-ray diffraction. The series includes binuclear molecular complexes [(La3+–Nd3+), (La′3+–Nd′3+), (Sm3+–Tb3+)], which transition to pseudo-dimeric units (Gd3+–Y3+) as a result of the lanthanide contraction. The range of structures is completed by distinct oxalate-bridged binuclear complexes (Tm3+–Lu3+), formed via in situ synthesis, that appear only with the smallest lanthanides and only from higher temperature syntheses. There are subtle differences in coordination environments between the five structure types as a result of the lanthanide contraction, despite all complexes in this study containing binuclear units. All twenty-four complexes feature halogen- and π-based supramolecular interactions which assemble the molecular complexes into one, two, and three dimensions. Visible and near-IR solid state luminescence spectra were collected on complexes 3, 4, 5, 6, 8, 8′, 9, 12, and 13 and characteristic terpyridine sensitized luminescence was observed.