Synthesis, characterization, and luminescence properties of a new series of Eu3+-containing macrocycles

The synthesis and structural characterization of a series of neutral Eu(3+)-containing macrocyclic complexes, Eu(4)-Eu(7), are reported. The synthetic pathway herein allows for the size and functionality of the macrocycle to be tailored in one step from a common precursor (N,N' '-bis(p-isothiocyanatobenzylcarbamoylmethyl)diethylenetriamine-N,N'N' '-triacetic acid, (3) in high yield. The macrocyclic ligands 4-7 have within their structure a bis-amide derivative of diethylenetriaminepentaacetic acid (DTPA) functioning as the europium chelate that is bridged through thiourea groups by either a butyl (4), hexyl (5), octyl (6), or m-benzyl (7) linker. The two thiourea groups were designed into the host macrocycle to serve as hydrogen-bond donors to potential guest molecules that may alter the luminescence properties of the parent macrocycle. Characterization of the luminescence of Eu(4)-Eu(7) reveals an antenna effect from the ligand, and the luminescence lifetime data reveals the presence of one coordinated water molecule in aqueous solution.     

Self-assembled, kinetically locked, Ru(II)-based metallomacrocycles: physical, structural, and modeling studies

By using a "complex as ligand approach," the metal-ion-templated self-assembly of heterometallic tetranuclear metallomacrocycles containing kinetically locked Ru(II) centers is described. Depending on the metal-ion template employed in the self-assembly process, the final macrocycle can be kinetically labile or inert. Electrochemical studies reveal that the kinetically inert macrocycles display reversible Ru(III/II) oxidation couples. The crystal structure of a kinetically inert Ru2Re2 macrocycles reveals a structurally complex palmate anion-binding pocket. Host-guest studies carried out with the same macrocyle in organic solvents reveals that the complex functions as a luminescent sensor for anions and that binding affinity and luminescent modulation is dependent on the structural nature and charge of the guest anion. Computational density functional theory (DFT) studies support the hypothesis that the luminescence of the macrocycle is from a 3MLCT state and further suggests that the observed guest-induced luminescence changes are most likely due to modulation of nonradiative decay processes.     

Novel red-emitting Ba2Tb(BO3)2Cl:Eu phosphor with efficient energy transfer for potential application in white light-emitting diodes

A novel red-emitting Ba(2)Tb(BO(3))(2)Cl:Eu phosphor possessing a broad excitation band in the near-ultraviolet (n-UV) region was synthesized by the solid-state reaction. Versatile Ba(2)Tb(BO(3))(2)Cl compound has a rigid open framework, which can offer two types of sites for various valence's cations to occupy, and the coexistence of Eu(2+)/Eu(3+) and the red-emitting luminescence from Eu(3+) with the aid of efficient energy transfer of Eu(2+)-Eu(3+)(Tb(3+)) and Tb(3+)-Eu(3+) have been investigated. Ba(2)Tb(BO(3))(2)Cl emits green emission with the main peak around 543 nm, which originates from (5)D(4) → (7)F(5) transition of Tb(3+). Ba(2)Tb(BO(3))(2)Cl:Eu shows bright red emission from Eu(3+) with peaks around 594, 612, and 624 nm under n-UV excitation (350-420 nm). The existence of Eu(2+) can be testified by the broad-band excitation spectrum, UV-vis reflectance spectrum, X-ray photoelectron spectrum, and Eu L(3)-edge X-ray absorption spectrum. Decay time and time-resolved luminescence measurements indicated that the interesting luminescence behavior should be ascribed to efficient energy transfer of Eu(2+)-Eu(3+)(Tb(3+)) and Tb(3+)-Eu(3+) in Ba(2)Tb(BO(3))(2)Cl:Eu phosphors.     

Photoproducts formed from photofrin II in cells

Fluorescence and absorption spectra of light-exposed cells containing the tumour-localizing porphyrin preparation Photofrin II (PII) have been studied. Light exposure results in spectral changes that may be due to a photoinduced modification of the porphyrins without breakage of the porphyrin macrocycle and/or to a photoinduced displacement of the porphyrins in the cells. Photochemical reaction involving breakage of the porphyrin macrocycle also occur as can be seen from the loss of absorbance within the Soret band region during light exposure. Singlet oxygen may be involved in the photodegradation of PII in cells since the process is slowed down on bubbling N2 through the samples and is slightly faster in suspensions in Dulbecco's phosphate buffered saline (PBS) made of D2O compared with suspensions in PBS made of H2O. During light exposure a fluorescent product is formed in the cells with fluorescence excitation and emission characteristics similar to those of the "age pigment" lipofuscin (lambda exc = 350 nm, lambda em = 440 nm).     

The preparation and performance of visible-light-sensitized luminescent nanoparticles based on europium complex

Long-wavelength-sensitized luminescent materials are desired for bio-detection. In this paper, we prepared a new kind of luminescent europium nanoparticles by a co-precipitation-condensation method. The luminescent europium complex Eu（tta）3.bpt （tta = thenoyltrifluoroacetonate; bpt = 2-（N,N- di-ethylanilin-4-yl）-4,6-bis（pyrazol-l-yl）-l,3,5-triazine） was used as the active material, being encapsulated in the nanoparticles formed from 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane （PFOTS） and poly（styrene-co-methyl methacrylate） [P（ST-co-MMA）]. The prepared nanoparticles not only can be well dispersed in water but also were of high photostability. Importantly, the nanoparticles displayed maximal excitation wavelength at 425 nm as well as an extended excitation wavelength up to 480 nm and a quantum yield for Eu3＋ luminescence of 0.22 （λex= 425 nm, room temperature）.     

Synthesis, electrochemistry, and photophysical properties of a series of luminescent pyrene-thiophene dyads and the corresponding Co2(CO)6 complexes

A series of pyrene based dyad systems together with their dicobalt hexacarbonyl complexes (1b-6b) were synthesized. The pyrene-thiophene dyads are luminescent in room temperature solution with luminescence lifetimes on the nanosecond time scale. At room temperature the dyad emission is quenched by coordination to a Co(2)(CO)(6) moiety via an acetylene bridge. However, at 77 K this emission is not fully quenched following complexation. Electrochemical studies suggest that an intraligand state is responsible for the emission. Photochemical studies in the presence of PPh(3) indicate that CO loss occurs following broadband irradiation with lambda(exc) > 400 nm, resulting in the formation of both -pentacarbonyl and -tetracarbonyl photoproducts.     

Synthesis and photophysical properties of colloids fabricated by the layer-by-layer polyelectrolyte assembly onto Eu(III) complex as a core

The luminescent colloids have been synthesized through the layer-by-layer assembly of poly(sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI) onto the luminescent core. The latter has been obtained by the reprecipitation of complex Eu[(TTA)(3)1] (where TTA(-) and 1 are thenoyltrifluoroacetonate and 2-(5-chlorophenyl-2-hydroxy)-2-phenylethenyl-bis-(2-methoxyphenyl)phosphine oxide, respectively) from organic solvent to aqueous solution. The variation of Eu(III) complexes indicates the role of the complex core in the development of such core-shell colloids. Complex Eu[(TTA)(3)1] is most convenient precursor of Eu-doped luminescent nanocomposites. The fluorometric measurements at each step of the layer-by-layer polyelectrolyte assembly onto Eu[(TTA)(3)1] core, at various pHs and additives reveal the quenching of Eu-centered luminescence as a result of the interfacial interaction of the core and the dye. The AFM images and electrochemical behavior of PSS-(PEI-PSS)(n)-Eu[(TTA)(3)1] colloids deposited on the surface indicate the stability of the polyelectrolyte multilayer in the dried state.     

静电纺丝制备荧光导电双功能复合纳米纤维及其表征

采用静电纺丝技术将导电聚苯胺(PANI)和铕/铽稀土配合物掺杂到高分子基质聚乙烯吡咯烷酮(PVP)中,制备出荧光导电复合纳米纤维。用扫描电镜(SEM)、荧光光谱仪(FL)、宽频介电松驰谱仪对荧光导电复合纳米纤维的性能进行分析,结果显示,在270nm紫外光激发下,铕系列与铽系列复合纳米纤维分别发出红光和绿光。同时,复合纳米纤维的电导率可以达到1.18×10~(-6) S/cm,两种复合纳米纤维同时具有优异的荧光性能及良好的导电功能。     

Cation coordination induced modulation of the anion sensing properties of a ferrocene-imidazophenanthroline dyad: multichannel recognition from phosphate-related to chloride anions

A new chemosensor molecule 1 based on a ferrocene-imidazophenanthroline dyad, effectively recognizes aqueous hydrogenpyrophosphate and the organic anions ADP and ATP through three different channels. A cathodic shift of the ferrocene/ferrocenium oxidation wave (Delta E 1/2 ranging from -130 mV for hydrogenpyrophosphate and fluoride to -40 mV for ADP). A progressive red-shift of the absorption bands and/or appearance of a new low energy band at 314-319 nm. These changes in the absorption spectra are accompanied by color changes from pale yellow to orange or pink, which allow the potential for "naked eye" detection. The emission spectrum (lambda exc = 390 nm) undergoes an important chelation-enhanced fluorescence effect (CHEF = 50) in the presence of 2.5 equiv of hydrogenpyrophosphate anion and with a large excess of fluoride anion (CHEF = 114). Interestingly, the emission spectrum obtained at different excitation energy (lambda exc = 340 nm) in the presence of AcOH acid is red-shifted and not only perturbed by the hydrogenpyrophosphate anion (CHEF = 71) but also with the organic anions ATP (CHEF = 25), ADP (CHEF = 15), and the dihydrogenphosphate (CHEF = 25). The stable heterobimetallic ruthenium (II) complex 2 selectively senses the chloride anion over other anions examined through two channels: cathodic redox shift (Delta E 1/2 = -80 mV) of the Fe(II)/Fe(III) redox couple keeping the oxidation wave of the ruthenium (II) center unchanged and a significant red emission enhancement (CHEF = 30). (1)H and (31)P NMR studies as well as DFT calculations have been carried out to get information about which molecular sites are involved in bonding. About the deprotonation/coordination dualism, the combined electrochemical, absorption, emission, and NMR data strongly support that fluoride anion induces only deprotonation, anions dihydrogenphosphate, ATP, and ADP from hydrogen-bonded complexes and formation of hydrogen-bonded complex between receptor 1 and hydrogenpyrophosphate anion and deprotonation proceed simultaneously. In regards to receptor 2, all available data (electrochemical, absorption, emission, and 1H NMR) strongly support the formation of a [2. Cl ( - ) ] hydrogen-bonded complex.     

Disilver(I) macrocycles: variation of cavity size with anion binding

Reaction of the N-methylated bis(amidopyridine) ligand, LL = C6H4(1,3-CONMe-4-C5H4N)2, with the silver salts AgNO3, AgO2CCF3, AgO3SCF3, AgBF4, and AgPF6 gave the corresponding cationic disilver(I) macrocycles [Ag2(micro-LL)2]X2, 2a-e. The transannular silver...silver distance in the macrocycles varies greatly from 2.99 to 7.03 A, and these differences arise through a combination of different modes ofanion binding and from the presence or absence of silver...silver secondary bonding. In all complexes, the ligand adopts a conformation in which the methyl group and oxygen atom of the MeNCO units are mutually cis, but the overall macrocycle can exist in either boat (X = PF6 only) or chair conformation. Short transannular silver...silver distances are found in complexes 2b,c, in which the anions CF3CO2- and CF3SO3- bind above and below the macrocycle, but longer silver...silver distances are found for 2a,d,e, in which the anions are present, at least in part, inside the disilver macrocycle. Easy anion exchange occurs in solution, and studies using ESI-MS indicate that the anion binding to form [Ag2X(micro-LL)2]+ follows the sequence X = CF3CO2- > NO3- > CF3SO3-.     

Influence of charge on anion receptivity in amide-based macrocycles

Binding and structural aspects of anions with tetraamido/diquaternized diamino macrocyclic receptors containing m-xylyl, pyridine, and thiophene spacers are reported. (1)H NMR studies indicate that the quaternized receptors display higher affinities for anions compared to corresponding neutral macrocycles. The macrocycles containing pyridine spacers consistently display higher affinity for a given anion compared to those with either m-xylyl or thiophene spacers. The m-xylyl- and pyridine-containing receptors exhibit high selectivity for H(2)PO(4)(-) in DMSO-d(6) with association constants, K(a) = 1.09 × 10(4) and >10(5) M(-1), respectively, and moderate selectivity for Cl(-) with K(a) = 1.70 × 10(3) and 5.62 × 10(4) M(-1), respectively. Crystallographic studies for the Cl(-) and HSO(4)(-) complexes indicate that the m-xylyl-containing ligand is relatively elliptical in shape, with the two charges at ends of the major axis of the ellipse. The anions are hydrogen bonded with the macrocycle but are outside the ligand cavity. In the solid state, an unusual low-barrier hydrogen bond (LBHB) was discovered between two of the macrocycle's carbonyl oxygen atoms in the HSO(4)(-) complex. The pyridine-containing macrocycle folds so that the two pyridine units are face-to-face. The two I(-) ions are chelated to the two amides adjacent to a given pyridine. In the structure of the thiophene containing macrocycle with two BPh(4)(-) counterions, virtually no interaction was observed crystallographically between the macrocycle and the bulky anions.     

New lanthanide complexes for sensitized visible and near-IR light emission: synthesis, 1H NMR, and X-ray structural investigation and photophysical properties

We describe the syntheses, the 1H NMR studies in CD3OD and D2O as solvent, the X-ray characterization, and the luminescence properties in D2O solution of the two complexes Eu.1 and Er.1, where 1 is a dipartite ligand that includes (i) a 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) unit serving as hosting site for the metal center; and (ii) a phenanthroline unit which plays the role of light antenna for the sensitization process of the metal centered luminescence. In a previous report (Inorg. Chem. 2002, 41, 2777), we have shown that for Eu.1 there are no water molecules within the first coordination sphere. X-ray and 1H NMR results reported here are consistent with full saturation of the nine coordination sites within the Eu.1 and Er.1 complexes. In addition, these studies provide important details regarding the conformations, square antiprism (SAP) and twisted square antiprism (TSAP), adopted in solution by these complexes. The luminescence results are consistent with both an effective intersystem crossing (ISC) at the light absorbing phenanthroline unit (lambda(exc) = 278 nm) and an effective energy transfer (en) process from the phenanthroline donor to the cation acceptor (with unit or close to unit efficiency for both steps). In D2O solvent, the overall sensitization efficiency, phi(se), is 0.3 and 5 x 10(-6), for Eu.1 (main luminescence peaks at 585, 612, 699 nm) and Er.1 (luminescence peak at 1530 nm), respectively. The photophysical properties of both complexes are discussed with reference to their structural features as elucidated by the obtained 1H NMR and X-ray results.     

Ratiometric probes for hydrogencarbonate analysis in intracellular or extracellular environments using europium luminescence

A series of six, cationic, zwitterionic and anionic Eu complexes has been examined for the analysis of hydrogencarbonate concentration in the intracellular and extracellular ranges; an anionic complex incorporating three glutarate residues and a sensitising acridone chromophore (lambda exc = 410 nm) exhibits a 69% change in the intensity ratio of the 618/588 nm Eu emission bands between 5 and 15 mM HCO3- in a cell lysate medium.     

Eu(III) complexes as anion-responsive luminescent sensors and paramagnetic chemical exchange saturation transfer agents

The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the (1)H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate, and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate, and carbonate. These anions have weak dissociation constants that range from 19 to 38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate, and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at pH 6.5 or 7.2. This work shows that the Eu(S-THP) complex has unique selectivity toward binding of biologically relevant anions and that anion binding results in changes in both the luminescence and the PARACEST spectra of the complex.     

Bambus[n]urils: a new family of macrocyclic anion receptors

A recently discovered anion receptor is jointed by three related macrocycles differing in the number of glycoluril units and type of substitution. The synthesis is carried out in nonpolar solvents compared to aqueous media used in the case of the original macrocycle. The size of macrocycle is controlled by a template. A hexameric macrocycle with benzyl substitution binds halide anions with an affinity exceeding 10(9) M(-1) while a tetrameric analog does not bind any of the investigated anions.     

Colloidal nanoparticles of a europium complex with enhanced luminescent properties

We report an alternative approach, that is, forming Eu(tta)3dpbt (dpbt = 2-( N, N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine, tta = thenoyltrifluoroacetonato) nanoparticles in water/methanol mixtures, to satisfy the combined requirements of good dispersibility in water solutions and efficient long-wavelength sensitization for Eu (III) complexes to be used in biological applications. The size of Eu(tta)3dpbt colloidal particles with very high luminescent capabilities can be modulated to some extent by changing the preparation conditions. The optical excitation window for the Eu (III) luminescence of Eu(tta)3dpbt nanoparticles, extending up to 475 nm, is wider than that of Eu(tta)3dpbt molecules dissolved in toluene. This is the first example for obviously extending the sensitization window of luminescent lanthanide materials to the long-wavelength region by forming nanoparticles of a lanthanide complex. Quantum yields of Eu (III) luminescence of the prepared Eu(tta)3dpbt colloidal particles, with an average diameter of 33.1 nm, are 0.27, 0.27, 0.24, 0.19, 0.14, and 0.01 upon excitation at 402, 420, 430, 440, 450, and 475 nm, respectively. The Eu(tta)3dpbt nanoparticles exhibited excellent two-photon sensitization performance with a highest delta Phi value of 3.2 x 10(5) GM (1 GM = 10(-50) cm4 s photo(-1) particle(-1)) at the excitation wavelength of 832 nm, which is about 7 times higher than the highest value reported for the CdSe/ZnS core-shell quantum dots. The favorable luminescent properties and the good dispersibility in water solutions of the Eu(tta)3dpbt nanoparticles are very promising for the development of new luminescent nanoprobes for bioanalysis.     

Tetra- and octalactam macrocycles and catenanes with exocyclic metal coordination sites: versatile building blocks for supramolecular chemistry

The synthesis of a new tetralactam macrocycle and the simultaneous formation of catenanes and larger octalactam macrocycles is reported. These species bear 2,2'-biquinoline moieties suitably positioned to bind a metal center at the outer periphery of the macrocycles. (1)H NMR chemical shifts permit the unambiguous distinction of transoid and cisoid conformations of the biquinoline moiety, thereby allowing an unequivocal identification of the catenane and octalactam structures, despite the fact that both have the same elemental composition and bear identical structural subunits. With the aid of an anion template effect, rotaxanes can be prepared from the smaller tetralactam macrocycle. These reveal significantly altered requirements in terms of the stopper size as compared to previously reported tetralactam wheels. Several copper(I)-mediated dimers and a (bpy)(2)Ru(II) complex (bpy=2,2'-bipyridine) have been synthesized from the tetralactam macrocycle and the rotaxanes. The anion binding abilities of the tetralactam macrocycle and its (bpy)(2)Ru(II) complex in DMSO have been compared by (1)H NMR titration experiments, which revealed significantly enhanced binding by the metal complex. Mass spectrometry has been used to study the potential formation of larger assemblies of copper(I) and the catenane built-up from two tetralactam macrocycles. Indeed, a 2:2 complex was identified. In contrast, the octalactam macrocycle of the same elemental composition yields only 1:1 complexes, with the Cu(I) ion connecting its two biquinoline moieties in the center of a figure-eight-shaped molecule. Molecular modeling studies support the structural assignments made.     

长波敏化发光铕配合物纳米粒子的制备与表征

以牛血清白蛋白(BSA)为保护剂, 利用沉淀法制备了平均粒径为35 nm的Eu(tta)3dpbt (dpbt = 2-(N,N-二乙基苯胺-4-基)-4,6-二(3,5-二甲基吡唑-1-基)-1,3,5-三嗪, tta = 噻吩甲酰三氟丙酮负离子)荧光纳米粒子. BSA保护Eu(tta)3dpbt纳米粒子在水中分散稳定性高, 光稳定性好, 长波敏化发光性能优良. 其在可见光区激发峰位于415 nm, 激发峰尾部延展至470 nm, 发光量子产率为0.20 (λex=415 nm, 25 ℃). 在近红外双光子激发下可发出纯正的红光, Eu(tta)3dpbt纳米粒子最大双光子激发作用截面为2.4×10⁵ GM (λex=830 nm, 1 GM=10^-50 cm⁴·s·photo^-1·particle^-1).     

Synthesis under Micromave Irradition and Crystal Structure of 4''-Acetylbenzo-15 -crown-5thiosemicarbazone

The title compound is a bifunctional receptors including a thiourea group and a crown ether ring. Due to many possible potentials as a new class of reagents for membrane transports,ion-selective electrodes as well as reaction catalysts, the design and synthesis of bifunctional receptors for simultaneous binding of cations and anions is of ongoning interest in srprarnolecular chemistry1-5. In bifunctional receptors, the binding sites for anions and cations are covalently linked so as to exhibit allosteric or cooperative complexation where the binding affinity for anions(cations)is modified as a result of the cation(anion) complexation.Literature[6] reported that the ability of the thiourea group to bind anions is significantly enhanced when Na+ is bound to the crown moiety. To date, however only a few receptors of this class have been reported.6-8In this paper, we report an improved procedure under microwave irradiation that gives higher yields of title compound and needs fewer reaction times than traditional method.The structure of this compound was determined by IR ,element analysis and X-ray analysis.Scheme 1 The reaction equationThe crystal belongs to triclinic crystal system, P-1 space group, a=0.9547(0)nm, b=1.3637(3)nm,c=1.6029(3)nm, α =75.33(3) , β =83.62(3) , γ =70.99(3) ,Z=4,Dc=1.335g/cm3,F(000)=816,R1= 0.0557 ,wR2=0.1281. It is assembled into a three-dimensionalsupramolecule by intermolecular hydrogen bonds.     

钨钼酸盐荧光粉基质组成及其退火过程对荧光性能的影响

采用高温固相法合成了一系列Eu3+掺杂的钨钼酸盐红色荧光粉CaxSr0.88-x(WO4)y(MoO4)1-y:0.08Eu3+。对其晶体结构和荧光性能进行了X射线衍射(XRD)、荧光光谱(PL)的表征,研究了不同Sr/Ca和WO4/MoO4比例对荧光粉光谱性能的影响,初步研究了不同退火过程对其发光性能的影响。所合成的Ca0.70Sr0.18(MoO4)0.5(WO4)0.5:0.08Eu3+荧光粉发光强度较好,可以被近紫外光(395 nm)和蓝光(465nm)有效激发,发射峰位于616 nm(Eu3+的5 D0→7 F2跃迁)。