Synthesis, Crystal Structure and Optical Properties of Europium Trifluoroacetate Complexes with 1,10-Phenanthroline and 2,2-Bipyridine

Two europium trifluoroacetate complexes, Eu(CF₃COO)₃·phen ( 1 ) and Eu(CF₃COO)₃·bpy ( 2 ) (where phen=1,10‐phenanthroline, bpy=2,2′‐bipyridine), were synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy (FT‐IR), photoluminescence (PL) spectroscopy and thermogravimetric analysis (TA). Single‐crystal X‐ray structure has been determined for the complex [Eu₂(CF₃COO)₆·(phen)₃·(H₂O)₂]·EtOH. The crystal structure of [Eu₂(CF₃COO)₆·(phen)₃·(H₂O)₂]·EtOH shows that two different coordination styles with europium ions coexist in the same crystal and have entirely different coordination geometries and numbers. This crystal can be considered as an 1:1 adduct of [Eu(CF₃COO)₃·(Phen)₂·H₂O]·EtOH (9‐coordination part) and Eu(CF₃COO)₃·phen·H₂O (8‐coordination part). The excitation spectra of the two complexes demonstrate that the energy collected by "antenna ligands" is transferred to Eu³⁺ ions efficiently. The room‐temperature PL spectra of the complexes are composed of the typical Eu³⁺ ions red emission, due to transitions between ⁵D₀→⁷F_J(J=0→4). The lifetimes of ⁵D₀ of Eu³⁺ in the complexes were examined using time‐resolved spectroscopic analysis, and the lifetime values of Eu(CF₃COO)₃·phen and Eu(CF₃COO)₃·bpy were fitting with bi‐exponential (2987 and 353 µs) and monoexponential (3191 µs) curves, respectively. In order to elucidate the energy transfer process of the europium complexes, the energy levels of the relevant electronic states had been estimated. The thermal analyses indicate that they are all quite stable to heat.     

High‐Performance Oxygen Sensors Based on EuIII Complex/Polystyrene Composite Nanofibrous Membranes Prepared by Electrospinning

An optical oxygen sensor based on an Eu^III complex/polystyrene (PS) composite nanofibrous membrane is prepared by electrospinning. The emission intensity of [Eu(TTA)₃(phencarz)] (TTA=2‐thenoyltrifluoroacetonate, phencarz=2‐(N‐ethylcarbazolyl‐4)imidazo[4,5‐f]1,10‐phenanthroline) decreases with increasing oxygen concentration, and thus the [Eu(TTA)₃ (phencarz)]/PS composite nanofibrous membranes can be used as an optical oxygen‐sensing material based on emission quenching caused by oxygen. Elemental analysis, UV/Vis absorption spectra, scanning electron microscopy (SEM), fluorescence microscopy, luminescence‐intensity quenching Stern–Volmer plots, and excited‐state decay analysis are used to characterize the obtained oxygen‐sensing materials. A high sensitivity (I_N2/I_O2) of 3.38 and short response and recovery times (t_↓=5.0, t_↑=8.0 s) are obtained. These results are the best values reported for oxygen sensors based on Eu^III complexes. The high surface area‐to‐volume ratio and porous structure of the electrospun nanofibrous membranes are taken to be responsible for the outstanding performance.     

Crystal Structure and Luminescence of [Eu(TTA)3·DAF]·0.5C7H8 Complex Excited by Visible Light

The non‐ionic europium(III) complex [Eu(TTA)₃·DAF]·0.5C₇H₈ (TTA = 2‐thenoytrifluoroacetonate, DAF = 4, 5‐diazafluoren‐9‐one) was synthesized. The structural determination has been carried out. DAF coordination induces the both excitation spectra in the solid state and solution having a red shift and sensitizes Eu³⁺ luminescence under visible light excitation.     

Synthesis, photophysical and oxygen-sensing properties of a novel Eu complex incorporated in mesoporous MCM-41

A novel Eu³⁺ complex of Eu(DPIQ)(TTA)₃ (DPIQ=10H-dipyrido [f,h] indolo [3,2-b] quinoxaline, TTA=2-thenoyltrifluoroacetonate) was synthesized and encapsulated in the mesoporous MCM-41, hoping to explore an oxygen-sensing system based on the long-lived Eu³⁺ emitter. The Eu(DPIQ)(TTA)₃/MCM-41 composites were characterized by infrared spectra (IR), ultraviolet-visible (UV-vis) absorption spectra, small-angle X-ray diffraction (SAXRD), luminescence intensity quenching upon various oxygen concentrations, and fluorescence decay analysis. The results indicated that the composites exhibited the characteristic emission of the Eu³⁺ ion and the fluorescence intensity of ⁵D₀-⁷F₂ obviously decreased with increasing oxygen concentrations. The oxygen sensing properties of the composites with different loading levels of Eu(DPIQ)(TTA)₃ complex were investigated. A sensitivity of 3.04, a short response time of 7 s, and good linearity were obtained for the composites with a loading level of 20 mg/g. These results are the best reported values for optical oxygen-sensing materials based on Eu³⁺ complexes so far.     

Calorimetric investigations of luminescent films polycarbonate (PC) doped with europium complex [Eu(TTA)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]

Polymers doped with rare earth complexes are advantaged in film production for many applications in the luminescent field. In this luminescent polycarbonate (PC) films doped with diaquatris(thenoyltrifluoroacetonate)europium(III) complex [Eu(TTA)₃(H₂O)₂] were prepared and their calorimetric and luminescent properties in the solid state are reported. The thermal behavior was investigated by utilization of differential scanning calorimetry (DSC) and thermogravimetry (TG). Due of the addition of rare earth [Eu(TTA)₃(H₂O)₂] into PC matrix, changes were observed in the thermal behavior concerning the glass transition and thermal stability. Characteristic broadened narrow bands arising from the ⁵D₀ → ⁷F_J transitions (J = 4−0) of Eu³⁺ ion indicate the incorporation of the Eu³⁺ ions in the polymer. The luminescent films show enhancement emission intensity with an increase of rare earth concentration in polymeric matrix accompanied by decrease in thermal stability.     

Synthesis,Structures, and Luminescent Properties of Lanthanide Complexes with Triphenylphospine Oxide

Seven lanthanide complexes [Ln(OPPh₃)₃(NO₃)₃] ( 1 – 3 ) (OPPh₃ = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh₃)₄(NO₃)₂](NO₃) ( 4 ), [Ln(OPPh₃)₃(NO₃)₃]₂ ( 5 – 7 ) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh₃ ligand in the air. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1 – 4 are mononuclear complexes formed by OPPh₃ ligands and nitrates. The asymmetric units of complexes 5 – 7 consist of two crystallographic‐separate molecules. Complex 1 is self‐assembled to construct a 2D layer‐structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain‐like structure that was assembled by OPPh₃ ligands and nitrate ions through C–H ··· O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb³⁺ (λ_em = 480, 574 nm) and Eu³⁺ (λ_em = 552, 593, 619, 668 nm).     

Luminescence properties of sol-gel derived silica gels doped and undoped with RE-complexes(RE=Eu,Tb)

The luminescence properties of silica gels and silica gels doped with two rare earth complexes,Eu(TTA)3 and Tb(o-CBA)3 (TTA=thenoyltrifluocetate,o-CBA=o-chlorobenzoic acid) are reported and discussed.Pure silica gels show a blue luminescence,and the maximum excitation and emission wavelengths depend strongly on the solvents used.Both of the studied rare earth complexes exhibit the characteristic emissions of the rare earth ions in silica gels,i.e.,Eu3+5 Do→7 FJ(J=0,1,2,3,4),Tb3+5D4→7FJ(J=3,4,5,6) transitions.Compared with the pure RE-complexes powder,the silica gels doped with RE-complexes show fewer emission lines of the rare earth ions.Furthermore the rare earth ion (Tb3+) presents a longer lifetime (1346μs) in silica gel doped with Tb(o-CBA)3 than in pure Tb(o-CBA)3 powder (744μs).The reasons responsible for these results are discussed in the context.     

Microwave synthesis and characterization of europium complexes with cinnamic acid and phenanthroline

We report here the synthesis and characterization of a host of Eu(Phen)L₃ with cinnamic acid (C₆H₅CH = CHCOOH, HL) and phenanthroline (Phen), and employing microwave radiation, where the microwave radiation is used just for the uniform heating of the reaction mixture. Its IR absorption spectra, scanning electron microscopy (SEM), and fluorescence spectra were studied. The results show that the particles of Eu(Phen)L₃ phosphors are basically spherical in shape, with good dispersing. The mean particle size is 1–2 μm. The excitation spectrum is a broad band and the main peak is at 320.0 nm. Moreover, excitation peak at 396.0 nm was found in the excitation spectrum. The emission spectrum shows that Eu(Phen)L₃ has narrow emission peaks. The emission peaks are ascribed to Eu³⁺ ions transition from ⁵ D _J (J = 0) to ⁷ F _J (J = 1, 2, 4). However, the strongest main emission peak locates at 614.0 nm, which corresponds to the electric dipole transition of Eu³⁺(⁵ D ₀ → ⁷ F ₂) The article is published in the original.     

Synthesis,crystal structure and luminescence of three europium complexes with 2-iodobenzoic acid

Three new complexes, [Eu(2-IBA)₃?·?H₂O] _n (1), [Eu(2-IBA)₃?·?2,2′-bpy]₂ (2), and [Eu(2-IBA)₃?·phen]₂ (3) (2-IBA?=?2-iodobenzoato; 2,2′-bpy?=?2,2’-bipyridine; phen?=?1,10-phenanthroline) were synthesized, and their crystal structures determined by X-ray diffraction. In complex 1, Eu³⁺ ions are linked through carboxylate groups via bridging – chelating – bridging coordination modes to form a one-dimensional polymeric chain. The carboxylate groups are tetradentate-bridged. Complex 2 is binuclear with an inversion center, in which europium is nine-coordinated with seven oxygen atoms from five 2-IBA ligands and two nitrogen atoms from one 2,2′-bpy molecule in a distorted monocapped square antiprism. The crystal structure of 3 is similar to that of 2. These complexes emit red light luminescence. The ⁵ D ₀?→?⁷ F _j (j?=?1–4) transition emission of Eu³⁺ ion has been observed.     

Synthesis,crystal and molecular structure of the 3:2 complex between europium nitrate and the A-isomer of dicyclohexyln-18-crown-6: Conformational study of the ligand

The crystal and molecular Structure of bis[dinitrato-(2,5,8,15,18,21-hexaoxatricyclo[20.4.0.0^9,14]hexa-consane)europium(III)]pentakis(nitrato) europiate(III) ([Eu(NO₃)₂·L_A]₂[Eu(NO₃)₅]) has been determined from single-crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P2₁/c (ITC No. 14): a = 13.614(3)Å, b = 21.697(4)Å, c = 22.591(5)Å, β = 107.15(2)°, Z = 4. The structure was refined to a final R value of 0.055 (R_w = 0.055). The asymmetric unit contains three independent ions with approximate C₂ symmetry: [Eu(NO₃)₅]^2? and two distinct [Eu(NO₃)₂.L_a]⁺ cations with the macrocyclic ligand in the cis-syn-cis-conformation (A-isomer). The Eu(III) ions are 10-coordinated with the following mean bond lengths: Eu? O(nitrate) = 2.46(3)Å in the anion and the two cations, Eu? O(ether) = 2.55(9)Å in both cations. For the uncomplexed A-and B-isomers, as well as for their complexes with various metal ions, a conformational analysis has been made on the six O-atoms of the ligand which can be considererd as a fluxional ring. In the presently reported europium complex cations, the oxygen-ring conformation is almost a perfect boat with the metal ions lying in the least-sqiares plane of the O-atoms (deviation: 0.02–0.05Å). The same conformation prevails in all the complexes containing the A-isomer(exception: dimethylthallium complex) and in most of the complexes with the B-isomer. For this isomer, a chair conformation is found in the uncomplexed ligand, in the sodium complex, and in the complex with dimethylthallium. The occurrence of these conformations is discussed with respect to the crystallographic symmetry of the complexes and the relative mean M? O and O? O distances.     

Lanthanide(II) Complexes Supported by N,O‐Donor Tripodal Ligands: Synthesis,Structure, and Ligand‐Dependent Redox Behavior

The preparation and characterization of a series of complexes of the Yb and Eu cations in the oxidation state II and III with the tetradentate N,O‐donor tripodal ligands (tris(2‐pyridylmethyl)amine (TPA), BPA^? (HBPA=bis(2‐pyridylmethyl)(2‐hydroxybenzyl)amine), BPPA^? (HBPPA=bis(2‐pyridylmethyl)(3.5‐di‐tert‐butyl‐2‐hydroxybenzyl)amine), and MPA^2? (H₂MPA=(2‐pyridylmethyl)bis(3.5‐di‐tert‐butyl‐2‐hydroxybenzyl)amine) is reported. The X‐ray crystal structures of the heteroleptic Ln²⁺ complexes [Ln(TPA)I₂] (Ln=Eu, Yb) and [Yb(BPA)I(CH₃CN)]₂, of the Ln²⁺ homoleptic [Ln(TPA)₂]I₂ (Ln=Sm, Eu, Yb) and [Eu(BPA)₂] complexes, and of the Ln³⁺ [Eu(BPPA)₂]OTf and [Yb(MPA)₂K(dme)₂] (dme=dimethoxyethane) complexes have been determined. Cyclic voltammetry studies carried out on the bis‐ligand complexes of Eu³⁺ and Yb³⁺ show that the metal center reduction occurs at significantly lower potentials for the BPA^? ligand as compared with the TPA ligand. This suggests that the more electron‐rich character of the BPA^? ligand results in a higher reducing character of the lanthanide complexes of BPA^? compared with those of TPA. The important differences in the stability and reactivity of the investigated complexes are probably due to the observed difference in redox potential. Preliminary reactivity studies show that whereas the bis‐TPA complexes of Eu²⁺ and Yb²⁺ do not show any reactivity with heteroallenes, the [Eu(BPA)₂] complex reduces CS₂ to afford the first example of a lanthanide trithiocarbonate complex.     

The First Europium(III) β‐Diketonate Complex Functionalized Polyhedral Oligomeric Silsesquioxane

The first europium(III) β‐diketonate complex functionalized polyhedral oligomeric silsesquioxane (POSS) has been obtained by immobilization of such a complex at a silicon vertex of the POSS cage through the complexation of Eu³⁺ ions with thenoyltrifluoroacetone‐functionalized POSS. The new molecular hybrid material is liquid at room temperature, and shows bright‐red emission when irradiated with UV light due to energy transfer from the thenoyltrifluoroacetone ligand to the coordinated Eu³⁺ ions. Thermal analysis has revealed a significant improvement in the thermal stability of the material compared with tris(2‐thenoyltrifluoroacetonate)europium(III) dihydrate, [Eu(TTA)₃] ? 2 H₂O. In the context of recent advances in printable electronic technology, this novel luminescent organic liquid with the characteristic emission of Eu³⁺ may potentially be useful in the development of next‐generation organic devices such as flexible displays.     

Metal‐Ion Sensing Europium(III) Complexes with Bidentate Phosphine Oxide Ligands Containing a 2,2′‐Bipyridine Framework

Novel Eu^III complexes with bidentate phosphine oxide ligands containing a bipyridine framework, i.e., [3,3′‐bis(diphenylphosphoryl)‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)₃(BIPYPO)]) and [3,3′‐bis(diphenylphosphoryl)‐6,6′‐dimethyl‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)₃(Me‐BIPYPO)]), were synthesized for lanthanide‐based sensor materials having high emission quantum yields and effective chemosensing properties. The emission quantum yields of [Eu(hfa)₃(BIPYPO)] and [Eu(hfa)₃(Me‐BIPYPO)] were 71 and 73%, respectively. Metal‐ion sensing properties of the Eu^III complexes were also studied by measuring the emission spectra of Eu^III complexes in the presence of Zn^II or Cu^II ions. The metal‐ion sensing and the photophysical properties of luminescent Eu^III complexes with a bidentate phosphine oxide containing 2,2′‐bipyridine framework are demonstrated for the first time.     

Synthesis,structure and luminescence properties of two novel lanthanide complexes with 2-fluorobenzoic acid and 1,10-phenanthroline

Two lanthanide complexes with 2-fluorobenzoate (2-FBA) and 1,10-phenanthroline (phen) were synthesized and characterized by X-ray diffraction. The structure of each complex contains two non-equivalent binuclear molecules, [Ln(2-FBA)₃?·?phen?·?CH₃CH₂OH]₂ and [Ln(2-FBA)₃?·?phen]₂ (Ln?=?Eu (1) and Sm (2)). In [Ln(2-FBA)₃?·?phen?·?CH₃CH₂OH]₂, the Ln³⁺ is surrounded by eight atoms, five O atoms from five 2-FBA groups, one O atom from ethanol and two N atoms from phen ligand; 2-FBA groups coordinate Ln³⁺ with monodentate and bridging coordination modes. The polyhedron around Ln³⁺ is a distorted square-antiprism. In [Ln(2-FBA)₃?·?phen]₂, the Ln³⁺ is coordinated by nine atoms, seven O atoms from five 2-FBA groups and two N atoms of phen ligand; 2-FBA groups coordinate Ln³⁺ ion with chelating, bridging and chelating-bridging three coordination modes. The polyhedron around Ln³⁺ ion is a distorted, monocapped square-antiprism. The europium complex exhibits strong red fluorescence from ⁵D₀?→?⁷F _j ( j?=?1–4) transition emission of Eu³⁺.     

Hydrothermal Syntheses,Crystal Structures,and Luminescent Properties of Three Organic‐Lanthanide Complexes with 3‐Hydroxycinnamic Acid

Three new homodinuclear lanthanide(III) complexes [Ln₂(L)₆(2,2′‐bipy)₂] [Ln = Tb^III ( 1 ), Sm^III ( 2 ), Eu^III ( 3 ); HL = 3‐hydroxycinnamic acid (3‐HCA); 2,2′‐bipy = 2,2′‐bipyridine] were synthesized and characterized by IR spectroscopy, elemental analyses, and X‐ray diffraction techniques. Complexes 1 – 3 crystallize in triclinic system, space group P$\bar{1}$ . In all complexes the lanthanide ions are nine‐coordinate by two nitrogen atoms from the 2,2′‐bipy ligand and seven oxygen atoms from one chelating L ligands and four bridging L ligands, forming distorted tricapped trigonal prismatic arrangements. The lanthanide(III) ions are intramolecularly bridged by eight carboxylate oxygen atoms forming dimeric complexes with Ln ··· Ln distances of 3.92747(15), 3.9664(6), and 3.9415(4) Å for complexes 1 – 3 , respectively. The luminescent properties in the solid state of HL ligand and Eu^III complex are also discussed.     

Visual Detection of Triethylamine and a Dual Input/Output Logic Gate Based on a Eu3+-Complex

A series of Ln³⁺-metal centered complexes, Ln(TTA)₃(DPPI) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; or Ln = Gd, 4) [(DPPI = N-(4-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenyl)-N-phenylbenzenamine) and (TTA = 2-Thenoyltrifluoroacetone)] have been synthesized and characterized. Among which, the Eu³⁺-complex shows efficient purity red luminescence in dimethylsulfoxide (DMSO) solution, with a Commission International De L’ Eclairage (CIE) coordinate at x = 0.638, y = 0.323 and Φ_Eu^L = 38.9%. Interestingly, increasing the amounts of triethylamine (TEA) in the solution regulates the energy transfer between the ligand and the Eu³⁺-metal center, which further leads to the luminescence color changing from red to white, and then bluish-green depending on the different excitation wavelengths. Based on this, we have designed the IMPLICATION logic gate for TEA recognition by applying the amounts of TEA and the excitation wavelengths as the dual input signal, which makes this Eu³⁺-complex a promising candidate for TEA-sensing optical sensors.     

Crystal Structure and Luminescence of a Europium Nitrate Complex with Furancarboxylic Acid and 2,2′-Bipyridine

Abstract

A quaternary mixed ligand europium complex, [Eu(FA)₂NO₃bipy]₂, has been synthesized, where FA = α-furancarboxylic acid anion and bipy=2,2′-bipyridine. The europium complex crystallizes in the triclinic system, space group P1. Its structure was determined by X-ray diffraction methods. The two europium ions in the dimer are held together by four carboxylate groups of furancarboxylic acid and each europium ion is further bonded to one chelated bidentate nitrate and one 2,2′-bipyridine molecule. The coordination modes of the four carboxylate groups are divided into two types, bidentate bridging and tridentate bridging, making a coordination number of 9. Excitation and luminescence spectra observed at 77 K show that the europium ion site in the crystal has low symmetry and emission 5D ₁→⁷ F_J of the Eu³⁺ ion disappears after 20 μs.     

Remarkable Tuning of the Coordination and Photophysical Properties of Lanthanide Ions in a Series of Tetrazole‐Based Complexes

A series of seven new tetrazole‐based ligands (L1, L3–L8) containing terpyridine or bipyridine chromophores suited to the formation of luminescent complexes of lanthanides have been synthesized. All ligands were prepared from the respective carbonitriles by thermal cycloaddition of sodium azide. The crystal structures of the homoleptic terpyridine–tetrazolate complexes [Ln(Li)₂]NHEt₃ (Ln=Nd, Eu, Tb for i=1, 2; Ln=Eu for i=3, 4) and of the monoaquo bypyridine–tetrazolate complex [Eu(H₂O)(L7)₂]NHEt₃ were determined. The tetradentate bipyridine–tetrazolate ligand forms nonhelical complexes that can contain a water molecule coordinated to the metal. Conversely, the pentadentate terpyridine–tetrazolate ligands wrap around the metal, thereby preventing solvent coordination and forming chiral double‐helical complexes similarly to the analogue terpyridine–carboxylate. Proton NMR spectroscopy studies show that the solid‐state structures of these complexes are retained in solution and indicate the kinetic stability of the hydrophobic complexes of terpyridine–tetrazolates. UV spectroscopy results suggest that terpyridine–tetrazolate complexes have a similar stability to their carboxylate analogues, which is sufficient for their isolation in aerobic conditions. The replacement of the carboxylate group with tetrazolate extends the absorption window of the corresponding terpyridine‐ (≈20 nm) and bipyridine‐based (25 nm) complexes towards the visible region (up to 440 nm). Moreover, the substitution of the terpyridine–tetrazolate system with different groups in the ligand series L3–L6 has a very important effect on both absorption spectra and luminescence efficiency of their lanthanide complexes. The tetrazole‐based ligands L1 and L3–L8 sensitize efficiently the luminescent emission of lanthanide ions in the visible and near‐IR regions with quantum yields ranging from 5 to 53 % for Eu^III complexes, 6 to 35 % for Tb^III complexes, and 0.1 to 0.3 % for Nd^III complexes, which is among the highest reported for a neodymium complex. The luminescence efficiency could be related to the energy of the ligand triplet states, which are strongly correlated to the ligand structures.     

Chiral Sensing of Various Amino Acids Using Induced Circularly Polarized Luminescence from Europium(III) Complexes of Phenanthroline Dicarboxylic Acid Derivatives

Circularly polarized luminescence (CPL) was observed from [Eu(dppda)₂]^? (dppda=4,7‐diphenyl‐1,10‐phenanthroline‐2,9‐dicarboxylic acid) and [Eu(pzpda)₂]^? (pzpda=pyrazino[2,3‐f][1,10]phenanthroline‐7,10‐dicarboxylic acid) in aqueous solutions containing various amino acids. The selectivity of these complexes towards amino acids enabled them to be used as chiral sensors and their behavior was compared with that of [Eu(pda)₂]^? (pda=1,10‐phenanthroline‐2,9‐dicarboxylic acid). As these Eu^III complexes have achiral D_2d structures under ordinary conditions, there were no CPL signals in the emission assigned to f–f transitions. However, when the solutions contained particular amino acids they exhibited detectable CPL signals with g_lum values of about 0.1 (g_lum=CPL/2 TL; TL=total luminescence). On examining 13 amino acids with these three Eu^III complexes, it was found that whether an amino acid induced a detectable CPL depended on the Eu^III complex ligands. For example, when ornithine was used as a chiral agent, only [Eu(dppda)₂]^? exhibited intense CPL in aqueous solutions of 10^?2 mol dm^?3. Steep amino acid concentration dependence suggested that CPL in [Eu(dppda)₂]^? and [Eu(pzpda)₂]^? was induced by the association of four or more amino acid molecules, whereas CPL in [Eu(pda)₂]^? was induced by association of two arginine molecules.     

Synthesis and Optical Properties of Europium‐Complex‐Doped Inorganic/Organic Hybrid Materials Built from Oxo–Hydroxo Organotin Nano Building Blocks

Hybrid materials doped with novel europium complexes were synthesized using PMMA‐co‐Sn₁₂Clusters (copolymers from oxohydroxo‐organotin dimethacrylate and methylmethacrylate) as the matrix material. Two types of hybrid materials were obtained: the physically doped product, PMMA‐co‐Sn₁₂Cluster/Eu(TTA)₃phen, and the grafted product, PMMA‐co‐Sn₁₂Cluster‐co‐[EuAA(TTA)₂phen] (TTA=2‐thenoyltrifluoroacetone, phen=phenanthroline and AA=acrylic acid). The hybrid materials exhibited characteristic luminescence of the Eu³⁺ ions, and also showed relative especial optical properties compared with samples just using PMMA as the matrix material. The PMMA‐co‐Sn₁₂Cluster matrix exhibited a high physical doping quantity of [Eu(TTA)₃phen], which can be attributed to the special structure of this kind of hybrid material. GPC (gel‐permeation chromatography), TGA (thermogravimetric analysis), SEM, ¹H NMR, ICP (inductively coupled plasma), ¹¹⁹Sn NMR, FTIR, and diffuse reflectance techniques were employed to characterize the structures and properties of these hybrid materials.