Ligand-based Emission Research Articles

Revolutionary fluorescent complex encapsulating berberine for the treatment of diabetic kidney disease

The prevalence of diabetes mellitus in China has reached epidemic levels, diabetic kidney disease (DKD) is characterized by impaired renal function and increased urinary albumin excretion. About 40 % of diabetic patients will develop DKD or even end-stage renal disease. Effective pharmacologic strategies are crucial for treating DKD—a serious complication causing disability and death. In this study, two cobalt(II) ion-based coordination polymers (CPs), [Co(L)2(DNSA)] (1) and [Co(L)(1,4-bdc)]n (2), were synthesized using cobalt(II) nitrate hexahydrate and 2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol under hydrothermal conditions. Fluorescence testing indicated ligand-based emission peaks, with CP1 showing a slight intensity increase and CP2 exhibiting significantly enhanced fluorescence due to its high-rigidity 3D framework. A polyethylene glycol (PEG)-modified CPs loaded with berberine, termed PEG-CPs@Berberine, was synthesized and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). This drug delivery system was evaluated in cell experiments, demonstrating its effectiveness in regulating ferroptosis and enhancing podocyte proliferation. The system's benefits for the therapy of DKD were established, and the specific mechanism was also explored.

A New Co(II)-coordination Polymer: Fluorescence Performances, Loaded with Paclitaxel-hydrogel on Breast Cancer and Molecular Docking Study.

In the current context of the increasing incidence of breast cancer, we aim to develop an efficient drug carrier for breast cancer by constructing an innovative complex consisting of a metal-organic framework (MOF) and a hydrogel. The aim of this initiative is to provide new ideas and tools for breast cancer treatment strategies through scientific research, so as to address the current challenges in breast cancer treatment. In the present study, by employment of a new Co(II)-based coordination polymer with the chemical formula of [Co(H2O)(CH3OH)L]n (1) (H2L = 5-(1H-tetrazol-5-yl)nicotinic acid) was solvothermally synthesized by reaction of Co(NO3)2·6H2O a mixed solvent of MeOH and water. The characteristics of ligand-based absorption and emission, as unveiled by ultraviolet and fluorescence spectroscopy tests, offer insights into the distinctive electronic transitions and structural features originating from the ligand in compound 1. Using natural polysaccharide hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as raw materials, HA/CMCS hydrogels were successfully prepared by chemical method and their internal morphology was studied by scanning electron microscopy. Using paclitaxel as a drug model, we further designed and synthesized a novel metal gel particle-loaded paclitaxel drug and evaluated its inhibitory effect on breast cancer cells. Finally, the hypothesized interactions between the complex and the receptor have been confirmed through molecular docking simulation, and multiple polar interactions have been verified, which further proves the potential anti-cancer capability and excellent bioactivity. Based on this, this composite material prepared from a novel Co(II)-coordinated polymer with paclitaxel hydrogel could provide a useful pathway for the identification and treatment of breast cancer.

Application Values of Two Cu(II) Schiff Base Coordination Complexes on Blue Fluorescent Materials.

Two Schiff base binuclear Cu(II) compounds, [Cu2(L)2·(H2O)2]·2DMF (1) together with its coordination polymer (CP) [Cu2(L)2·(4,4'-bpy)2]n (2) (H2L is 4-hydroxy-3-((2-hydroxy-5-mercaptobenzylidene)amino)-2H-chromen-2-one and 4,4'-bpy is 4,4'-bipyridine), were generated under an identical experimental environment in the absence and existence of auxiliary ligand 4,4'-bpy. Fluorescence spectroscopy testing shows that the ligand-based blue fluorescence emission offers potential for application as a blue photoluminescent material.

Divalent Europium, NIR and Variable Emission of Trivalent Tm, Ho, Pr, Er, Nd, and Ce in 3D Frameworks and 2D Networks of Ln–Pyridylpyrazolates

The redox reactions of various lanthanide metals with 3-(4-pyridyl)pyrazole (4-PyPzH) or 3-(3-pyridyl)pyrazole (3-PyPzH) ligands yield the 2D network ∞2[Eu(4-PyPz)2(Py)2] containing divalent europium, the 3D frameworks ∞3[Ln(4-PyPz)3] and ∞3[Ln(3-PyPz)3] for trivalent cerium, praseodymium, neodymium, holmium, erbium, and thulium as well as ∞3[La(4-PyPz)3], and the 2D networks ∞2[Ln(4-PyPz)3(Py)] for trivalent cerium and thulium and ∞2[Ln2(4-PyPz)6]·Py for trivalent ytterbium and lutetium. The 18 lanthanide coordination polymers were synthesized under solvothermal conditions in pyridine (Py), partly acting as a co-ligand for some networks. The compounds exhibit a variety of luminescence properties, including metal-centered 4f–4f/5d–4f emission in the visible and near-infrared spectral range, metal-to-ligand energy transfer, and ligand-centered fluorescence and phosphorescence. The anionic ligands 3-PyPz− and 4-PyPz− serve as suitable antennas for lanthanide-based luminescence in the visible and near-infrared range through effective sensitization followed by emission through intra–4f transitions of the trivalent thulium, holmium, praseodymium, erbium, and neodymium. ∞2[Ce(4-PyPz)3(Py)], ∞3[Ce(4-PyPz)3], and ∞3[Ce(3-PyPz)3] exhibit strong degrees of reduction in the 5d excited states that differ in intensity compared to the ligand-based emission, resulting in a distinct emission ranging from pink to orange. The direct current magnetic studies show magnetic isolation of the lanthanide centers in the crystal lattice of ∞3[Ln(3-PyPz)3], Ln = Dy, Ho, and Er.

Anthracene-based lanthanide coordination polymer for the sensitive detection of 2-thiazolidinethione-4-carboxylic acid and temperature

An anthracene-based rare earth coordination polymer (CP) [Tb2Cl2(adip)(NMP)3(H2O)] (1) was prepared by solvothermal assembling of Tb3+ and 5,5′-(anthracene-9,10-diyl)diisophthalic acid (H4adip, NMP = N-methylpyrrolidone) and possesses a 3D framework and ligand-based blue emission. 1 could be used as a fluorescent probe to detect 2-thiazolidinethione-4-carboxylic acid (TTCA) and temperature with excellent selectivity, sensitivity and anti-interference ability. Between 0 and 10 μM concentration range of TTCA, the fluorescence quenching constant (Ksv) of 1 reaches 9.78 × 104 M−1 with the limit of detection of 92.6 nM. 1 could also be used as a temperature sensor within 0–60 °C. The maximum relative sensitivity (Sr) was calculated as 5.74% °C−1 at 60 °C and the temperature resolution (δT) is 0.013–0.003 °C corresponding to the above ambient temperature range. The sensitivities of 1 have reached the best level of reported chemical sensors so far. In addition, the mechanisms of fluorescence quenching were studied.

Dual-Emission Metal–Organic Framework for Highly Selective Ratiometric Sensing of Lithium(I) Ions in Aqueous Solution

The development of highly selective and sensitive detection methods for lithium ions in various environments, such as aqueous or battery application, is highly sought. However, it remains elusive due to the small radius and weak coordination ability of lithium ions. Considering a metal–organic framework (MOF) possesses plentiful open coordination sites and an adjustable pore size, the well-designed MOF would be an ideal platform for the selective detection of Li+. Herein, a novel dual-emission luminescent metal–organic framework with three-dimensional structure, namely, Co–HIAT, was prepared by the hydrothermal method and structurally characterized. The Co–HIAT MOF displays the ligand-based emission at 340 nm and the charge transition emission between the metal ions and ligand at 410 nm simultaneously. Hence, the first example of ratiometric fluorescence detecting of Li+ can be achieved by measuring the ratio of fluorescence at 410 to 340 nm in the fluorescent spectra of the Co–HIAT, which exhibits the outstanding sensitivity and selectivity, giving a detection limit down to 0.17 μM. Detailed experimental studies showed that the sensing mechanism involves the strong interactions of Li+ with the reasonable hydroxyl and carboxyl oxygen atoms in the Co–HIAT framework, which is responsible for the ratiometric change in fluorescence emission properties in the inclusion of Li+. It is worth noting that electrochemical experiments further confirmed its superior affinity for lithium ions. This work represents an important and feasible pathway to design MOFs for the detection of Li+.

A multicenter lanthanide coordination polymer for ratiometric pesticide monitoring

Due to the increasing environmental and public health issues, efficient recognition and detection approaches for pesticides has attracted concerns worldwide. Herein, luminescent lanthanide coordination polymers (Ln-CPs) with tunable emissive centers are synthesized by simultaneously doping controlled amounts of Eu3+, Tb3+ and Gd3+ into the same framework. An optimized version of the multicenter Ln-CP (Eu0.048Tb0.052Gd0.9-CPBA) is prepared for 2D fingerprint recognizing pesticides. Additionally, the special “turn-on” response of ligand-based emission and “turn-off” response of Eu3+/Tb3+-based emission toward glyphosate (GPS) endow Eu0.048Tb0.052Gd0.9-CPBA with highly selective ratiometric sensing capability. The rapid, sensitive, selective and recyclable sensor for GPS provides a facile and adjustable synthetic approach for the development of multicenter ratiometric sensors. The real-time monitoring platform not only improves the sensitivity and selectivity but also holds great environmental significance.

Iron(II) complexes of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors.

Following a published synthesis of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine (L1), treatment of α,α'-dibromo-2,6-diacetylpyridine with 2 equiv. 2-aminopyrimidine or 2-aminoquinoline in refluxing acetonitrile respectively gives 2,6-bis(imidazo[1,2-a]pyrimidin-2-yl)pyridine (L2) and 2,6-bis(imidazo[1,2-a]quinolin-2-yl)pyridine (L3). Solvated crystals of [Fe(L1)2][BF4]2 (1[BF4]2) and [Fe(L2)2][BF4]2 (2[BF4]2) are mostly high-spin, although one solvate of 1[BF4]2 undergoes thermal spin-crossover on cooling. The iron coordination geometry is consistently distorted in crystals of 2[BF4]2 which may reflect the influence of intramolecular, inter-ligand N⋯π interactions on the molecular conformation. Only 1 : 1 Fe : L3 complexes were observed in solution, or isolated in the solid state; a crystal structure of [FeBr(py)2L3]Br·0.5H2O (py = pyridine) is presented. A solvate crystal structure of high-spin [Fe(L4)2][BF4]2 (L4 = 2,6-di{quinolin-2-yl}pyridine; 4[BF4]2) is also described, which exhibits a highly distorted six-coordinate geometry with a helical ligand conformation. The iron(II) complexes are high-spin in solution at room temperature, but 1[BF4]2 and 2[BF4]2 undergo thermal spin-crossover equilibria on cooling. All the compounds exhibit a ligand-based emission in solution at room temperature. Gas phase DFT calculations mostly reproduce the spin state properties of the complexes, but show small anomalies attributed to intramolecular, inter-ligand dispersion interactions in the sterically crowded molecules.

Single molecule magnet features in luminescent lanthanide coordination polymers with heptacoordinate Dy/Yb(III) ions as nodes.

Two sets of 1D/2D lanthanide coordination polymers with formulas of Ln(oqa)3·2H2O [Hoqa = 2-(4-oxoquinolin-1(4H)-yl) acetic acid, Ln = Dy (1), Yb (2)] and Ln(oaa)2(HCOO)(H2O) [Hoaa = 2-(9-oxoacridin-10(9H)-yl) acetic acid, Ln = Dy (3), Yb (4)] have been synthesized and their physical properties were investigated. All four complexes are constructed from seven-coordinate lanthanide ions and corresponding organic linkers. The lanthanide ions in 1 and 2 adopt a pentagonal bipyramid coordination geometry, whereas the coordination geometry of lanthanide ions in 3 and 4 can be described as a capped octahedron. Slow magnetic relaxation behaviors were observed in these four products at a zero/non-zero static magnetic field. Complexes 1, 2 and 4 exhibit the characteristic emission of Ln(III) ions, whereas complex 3 shows ligand-based emission. Bright yellow light emission was also observed when a voltage was applied, demonstrating the potential of 1 for application in light-emitting diodes (LEDs). Compounds 3 and 4 are the first examples of lanthanide complexes based on Hoaa ligands.

A water-stable dual-responsive Cd-CP for fluorometric recognition of hypochlorite and acetylacetone in aqueous media

One novel cadmium(II)-coordination polymer [Cd3L2(datrz)(H2O)3] (CP 1) is controllably synthesized by surmising the astute combination of semi-rigid tricarboxylate acid 4-(2′,3′-dicarboxylphenoxy) benzoic acid (H3L) and auxiliary ligand 3,5-diamino-1,2,4-triazole (datrz). Structure analysis shows that CP 1 has a two-dimensional (2D) layer structure with a 5-nodal (43) (44·62) (45·64·8) (45·6) (47·66·82) topology. Further investigations reveal that CP 1 shows superordinary water stability and good thermal stability. The fluorescent explorations suggest that the as-synthesized CP 1 could emit blue light centered at 485 nm, attributing to ligand-based emission. In terms of sensing investigations, CP 1 could act as a fluorescent sensor for detecting hypochlorite (ClO−) and acetylacetone (acac) through fluorescence turn-off process in aqueous solution, and the detection limit could reach 0.18 μM and 0.056 μM, respectively. Further research reveals that it is more likely the N–H···O–Cl hydrogen bonds between –NH2 groups of the triazole ligands and O atoms of ClO− plays the key role in the system, which may serve as a bridge for the energy transfer, leading to fluorescence quenching of the chemosensor. While the photoinduced electron transfer (PET) combined with inner filter effect (IFT) should be responsible for the turn-off fluorescence of CP 1 triggered by acac.

Influence of counter ions on supramolecular structures of copper(II) complexes derived from 1,8-naphthalimide tecton

A 2-amino-1H-benzo [de]isoquinoline-1,3-(2H)dione ligand (L) has been synthesized which forms a supramolecular metal-organic framework with various copper(Ⅱ) salts (1–3). The supramolecular structures are formed by a combination of covalent and noncovalent forces. The ligand (L) with copper chloride forms step-like chains in which the ligand is coordinated in a bidentate manner (1), whereas for the copper perchlorate derivative a ladder-like arrangement is attained in which the ligand is coordinated in both monodentate and bidentate fashion (2). A coordination polymer is formed with copper sulfate forming a wave-like arrangement (3). The EPR spectra revealed the elongated octahedral geometry around the cooper(Ⅱ) center in the complexes (1–3) which are in good agreement with the coordination environment observed from single crystal X-ray crystallographic studies. The complexes (1–3) are highly fluorescent in aqueous as well as organic solvents. Upon complexation, ligand-based emission is enhanced in complexes. So these complexes might be useful for bioimaging applications.

Dual-Ligand Near-Infrared Luminescent Lanthanide-Based Metal-Organic Framework Coupled with In Vivo Microdialysis for Highly Sensitive Ratiometric Detection of Zn2+ in a Mouse Model of Alzheimer's Disease.

Zinc, which is the second most abundant trace element in the human central nervous system, is closely associated with Alzheimer's disease (AD). However, attempts to develop highly sensitive and selective sensing systems for Zn2+ in the brain have not been successful. Here, we used a one-step solvothermal method to design and prepare a metal-organic framework (MOF) containing the dual ligands, terephthalic acid (H2BDC) and 2,2':6',2″-terpyridine (TPY), with Eu3+ as a metal node. This MOF is denoted as Eu-MOF/BDC-TPY. Adjustment of the size and morphology of Eu-MOF/BDC-TPY allowed the dual ligands to produce multiple luminescence peaks, which could be interpreted via ratiometric fluorescence to detect Zn2+ using the ratio of Eu3+-based emission, as the internal reference, and ligand-based emission, as the indicator. Thus, Eu-MOF/BDC-TPY not only displayed higher selectivity than other metal cations but also offered a highly accurate, sensitive, wide linear, color change-based technique for detecting Zn2+ at concentrations ranging from 1 nM to 2 μM, with a low limit of detection (0.08 nM). Moreover, Eu-MOF/BDC-TPY maintained structural stability and displayed a fluorescence intensity of at least 95.4% following storage in water for 6 months. More importantly, Eu-MOF/BDC-TPY sensed the presence of Zn2+ markedly rapidly (within 5 s), which was very useful in practical application. Furthermore, the results of our ratiometric luminescent method-based analysis of Zn2+ in AD mouse brains were consistent with those obtained using inductively coupled plasma mass spectrometry.

Two novel and high-efficiency optical chemosensors of detecting Fe3+ and CrO42− based on Metal−organic frameworks of Cd(Ⅱ)

Metal−organic frameworks (MOFs)-based sensors for sensing and monitoring toxic chemicals in water have profound significance to the ecological environment and human health. Hence, under hydrothermal conditions, two novel 3D Cd-MOFs, {[Cd3(NTB)2(bibp)4]•6H2O}n (Ⅰ) and [Cd(HNTB)(bibp)]n (Ⅱ) were synthesized, where H3NTB ​= ​4,4′,4″-nitrilotrisbenzoic acid and bibp ​= ​4,4′-bis(imidazolyl)biphenyl. The title Cd-MOFs were characterized via IR spectra, elemental analysis, thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Brunauer−Emmett−Teller (BET). Furthermore, both Ⅰ and Ⅱ present ligand-based blue emission in the solid state and can act as sensors for recognition of Fe3+ and CrO42− in water through fluorescence quenching with good selectivity, sensitivity and chemical stability. Notably, Cd-MOFs exhibit high quenching constants and low detection limits, which are higher or comparable to those chemical sensors reported. Subsequently, the possible sensing mechanisms were disclosed carefully by PXRD, ICP-AES, UV spectroscopy and XPS.

Zinc(II) picolinate-based coordination polymers as luminescent sensors of Fe3+ ions and nitroaromatic compounds

The synthesis, structure and photoluminescence properties of the zinc(II) picolinate-based coordination polymers [Zn(H2O)2(L1)] (1) and [Zn(L2)2]·0·.5H2O (2) (L12– = 5-((4-carboxyphenyl)ethynyl)picolinate; L2– = 5-(pyridin-3-ylethynyl)-picolinate) are reported. Both compounds exhibit a ligand-based blue emission under UV irradiation. 1 shows a strong enhancement of the emission intensity with respect to the free ligand with a high quantum yield value of 30 %. This luminescence is quenched by the presence of nitrobenzene or Fe3+ cations without loss of the integrity of the sample. The Stern-Volmer plot yields a value of KSV = 121 M−1, indicating a moderate ability for nitrobenzene sensing (limit of detection, LOD = 5.86·10–4 M). For Fe3+ detection, KSV and LOD values of 812 M−1 and 3.78·10–4 M are respectively obtained. 1 exhibits a strong dependence of the luminescent intensity on pH conditions, preserving its crystal integrity in the 2–12 pH range.

Synthesis, characterization, photoluminescence properties and cytotoxic activities of Sm(III) complexes of β-diketones

Three new homoleptic six-coordinate Sm(III) complexes have been synthesized from β-diketone ligand with different substituent groups. The structural characterization of these compounds has been investigated using elemental analysis, UV-Vis and FT-IR approaches. Then, their photoluminescence properties of the synthesized Sm(III) complexes have been examined. In addition to the ligand-based emission, the complexes showed Sm(III) based f-f transitions at 570-830 nm range. Also, the cytotoxic activities of the complexes have been studied against to human epidermoid carcinoma cell (HTB-54) and normal bronchus epithelial cell (BEAS-2B). According to result, the [Sm(MPBP-1,3PPon)3]·H2O) (IC50: 11.05 μM) complex was more active than [Sm(BMP-1,3PPon)3]·2H2O (IC50: 58.64 μM) and [Sm(BCP-1,3PPon)3]·H2O (IC50: >500 μM) complexes. Moreover, the [Sm(MPBP-1,3PPon)3]·H2O complex showed no effect on normal cell (BEAS-2B). This result shows that complex [Sm(MPBP-1,3PPon)3]·H2O has the potential to be as chemotherapeutic drug.

Unearth the Luminescence Potential of Metal-Organic Frameworks: Adopting a Feasible Strategy to Fabricate One Ratiometric Fluorescence Sensor for Monitoring Both 1-Hydroxypyrene and Cu2.

In this work, a novel luminescent hybrid material with double emission centers (Eu(TTA)0.2@9-1-UMOF) is successfully prepared, adopting a feasible design strategy. Initially, the second ligand 1,2,4-benzenetricarboxylic acid (H3BTC) is encapsulated based on a solid solution approach, which effectively improves the ligand-based emission intensity of the original LMOF and provides functional sites for introducing the second luminescent center; then, Eu3+ as the red emission source is loaded into the frameworks through a coordination post-synthetic modification method; finally, to balance the emission intensity at 613 nm (Eu3+) and 465 nm (1,4-naphthalenedicarboxylic acid (H2NDC)), 2-thenoyltrifluoroacetone (TTA) as a powerful antenna is introduced. Given the outstanding luminescence properties and structural stability of Eu(TTA)0.2@9-1-UMOF, it is further developed as a ratiometric sensor for detecting 1-hydroxypyrene (1-HP, the biomarker of polycyclic aromatic hydrocarbons (PAHs)) and Cu2+, which promotes the pre-diagnosis of human health. Notably, Eu(TTA)0.2@9-1-UMOF exhibits excellent selective recognition ability for both 1-HP and Cu2+ with high sensitivity (LOD = 4.06 × 10-6 mg/mL, 3.85 × 10-7 mol/L, respectively) and fast response speed. In addition, Eu(TTA)0.2@9-1-UMOF as a fluorescent probe shows great potential for the determination of 1-HP and Cu2+ in actual samples. More importantly, this work widens the road for the development of dual/multiple LMOF-based sensors for analytical applications.

Structure, reactivity and luminescence studies of triphenylsiloxide complexes of tetravalent lanthanides.

Among the 14 lanthanide elements (Ce–Lu), until recently, the tetravalent oxidation state was readily accessible in solution only for cerium while Pr(iv), Nd(iv), Dy(iv) and Tb(iv) had only been detected in the solid state. The triphenylsiloxide ligand recently allowed the isolation of molecular complexes of Tb(iv) and Pr(iv) providing an unique opportunity of investigating the luminescent properties of Ln(iv) ions. Here we have expanded the coordination studies of the triphenylsiloxide ligand with Ln(iii) and Ln(iv) ions and we report the first observed luminescence emission spectra of Pr(iv) complexes which are assigned to a ligand-based emission on the basis of the measured lifetime and computational studies. Binding of the ligand to the Pr(iv) ion leads to an unprecedented large shift of the ligand triplet state which is relevant for future applications in materials science.

Synthesis and optoelectronic properties of a dinuclear iridium (III) complex containing a picolinic acid derivative by nonconjugated linkage with a D-A-D core

A novel dinuclear iridium (Ⅲ) complex containing a non- conjugated bridging picolinic acid ligand of (C8TPAPhOC2FIrpic)2BT with a D-A-D core was synthesized and characterized, in which the D-A-D core consists of benzo[c][1,2,5]thiadiazole (BT) and triphenylamino (TPA) units. Its optophysical, electrochemical and electroluminescent characteristics were primarily studied. It is found this dinuclear iridium (Ⅲ) complex exhibited similar photoluminescent and electroluminescent profiles, but higher brightness and efficiency in compared with the picolinic acid ligand in the single-emissive-layer organic light-emitting devices. The maximum luminance of 7404 cd/m2 and current efficiency of 0.81 cd/A was obtained in the (C8TPAPhOC2FIrpic)2BT-based devices. The efficient energy transfer is observed from the terminal iridium complex unit to the picolinic acid ligand. This work demonstrates that the picolinic acid ligand with a D-A-D core can facilitate dinuclear iridium (III) complex to exhibit the ancillary ligand-based red emission.

A Two-Fold Interpenetrated Dual-Emitting Luminescent Metal-Organic Framework as a Ratiometric Sensor for Chromium(III).

A novel two-fold interpenetrated metal-organic framework, namely Co-EDDA, was synthesized by hydrothermal reaction of 5,5'-[ethane-1,2-diylbis(oxy)]diisophthalic acid (H4EDDA), Co(NO3)2·6H2O, and 1,4-di(1H-imidazol-1-yl)benzene in water in an alkaline environment and structurally characterized. Co-EDDA could display clear dual-emission signals at 350 and 430 nm, representing the charge transfer emission between metal ions and the ligand and the ligand-based emission, respectively, which represents the ratiometric luminescence response to chromium(III) with high selectivity and sensitivity (limit of detection of 0.54 μM). Comprehensive studies indicate that the detection can be attributed to the interaction between the Cr3+ ions and the O atoms on the ether bond in Co-EDDA.

Lanthanide dicyanoaurate coordination polymers containing 1,10-phenanthroline: Synthesis, structure, and luminescence

The synthesis of two novel lanthanide dicyanoaurates containing the bidentate ligand 1,10-phenanthroline (phen) have been carried out by reaction of select lanthanide nitrate salts with phen and potassium dicyanoaurate. The resultant compounds, [Ln(C12H8N2)(H2O)2{Au(CN)2}3] (Ln = Gd, Tb), are isostructural as established by single-crystal X-ray diffraction studies. Prominent structural features in these one-dimensional polymeric compounds are the existence of hexameric aurophilic interactions containing kinked Au6 units, π-stacking from partial phen ring alignment, and strong H-bonding interactions. Photoluminescence measurements illustrate that [Tb(C12H8N2)(H2O)2{Au(CN)2}3] displays enhanced Tb-based emission due to intramolecular energy transfer from the coordinated ligands while [Gd(C12H8N2)(H2O)2{Au(CN)2}3], which lacks low-lying electronic states, exhibits broad-band ligand-based emission.