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1.
Paramagnetic liquid crystalline complexes of the formula [LnL(LH)2][CF3SO3]2 have been synthesised, where LH is the ligand N-dodecyl-4-(3',4'-didodecyloxybenzoyloxy)salicylaldimine and Ln is a lanthanide metal. When compared with analogous nitrate complexes, the transition temperatures are rather low.  相似文献   

2.
Twelve 5, 10, 15, 20‐tetra[(4‐alkoxy‐3‐ethyloxy)phenyl]porphyrin hydroxylanthanide complexes Ln[(C n OEOP)4P](OH) (n?=?12, 14, 16;Ln?=?Tb, Dy, Er, Yb) and three ligands have been synthesized and their composition, structure and spectral properties studied. Their liquid crystalline behaviour is also presented. Differential scanning calorimetry and polarizing optical microscopy reveal that all exhibit a discotic liquid crystalline phase. X‐ray diffraction shows that the mesophase is a hexagonal columnar, Colh. The lanthanide ion, which is coordinated to the four nitrogen atoms of the porphyrin and to the oxygen atom of the hydroxyl group, is out of the porphyrin molecular plane. All the complexes are stable below 200°C and undergo complete decomposition at 800°C. The fluorescence quantum yields of the lanthanide complexes are much lower than those of the corresponding ligands. The electrochemical studies show that the redox potentials do not change on varying the chain length.  相似文献   

3.
The values of magnetic anisotropy of smectic A-phases for a number of lanthanide complexes (LH)2LM(NO3)2, where M=Nd, Eu, Gd, Tb, Dy, Ho, and Er, and LH is a Schiff's base), were measured. These values are two orders of magnitude larger than those normally found for diamagnetic liquid crystals and are well correlated with magnetic birefringence constants and molecular mangetic anisotropy of nomesogenic lanthanide diketonates. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 694–697, April, 1999.  相似文献   

4.
This work focuses on the investigation of the liquid crystalline behavior and luminescence properties of the lanthanide complexes of Eu(III), Sm(III) and Tb(III) with N-biphenyl-alkylated-4-pyridone ligands. The organic ligands having a biphenyl group attached via a long flexible spacer with either 9 or 10 carbon atoms were synthesized by the reaction between 4-hydroxypyridine and the corresponding bromide compounds. The chemical structures of the organic and lanthanide complexes were assigned based on elemental analysis, single-crystal X-ray diffraction, 1H, 13C NMR and IR spectroscopies, and thermogravimetric analysis (TGA). The X-ray diffraction analysis of a parent compound shows that the lanthanide ions are surrounded by three monodentate pyridone ligands and three bidentate nitrate ions, giving a 9-coordinate environment. The mesogenic behavior and the type of liquid crystalline phases exhibited by the new complexes were analyzed by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), and powder X-ray diffraction (XRD) studies. Only the lanthanide complexes with longer spacer (10) display a monotropic SmA phase, typically on a short thermal range (less than 10 °C). The complexes with shorter flexible chains (9) show no liquid crystalline properties with melting temperatures lower than their analogs with longer spacers. The emission spectra recorded in solid state at room temperatures show typical emission bands for each lanthanide ion employed (Eu(III), Tb(III) and Sm(III)).  相似文献   

5.
A series of liquid-crystalline lanthanide complexes with 1-(4-dodecyloxyphenyl)-3-octadecylamino-2-propene-1-one (HL), which is substituted β-enaminoketone, with the composition Ln(HL)3(NO3)3 (Ln = La, Nd, Gd, Tb, Dy, Ho, and Er) is synthesized. For the most part of the synthesized complexes, the magnetic susceptibility anisotropy (Δχmin) is shown to be one to two orders higher than Δχ of the “classical” organic liquid crystals.  相似文献   

6.
Acetato-bridged palladium–lanthanide tetranuclear heterometallic complexes of the form [Pd2Ln2(H2O)2(CH3COO)10] ⋅ 2 CH3COOH [Ln2=Ce2 ( 1 ), Pr2 ( 2 ), Nd2 ( 3 ), Sm2 ( 4 ), Tb2 ( 5 ), Dy2 ( 6 ), Dy0.2Y1.8 ( 6′′ ), Ho2 ( 7 ), Er2 ( 8 ), Er0.24Y1.7 ( 8′′ ), Tm2 ( 9 ), Yb2 ( 10 ), Y2( 11 )] were synthesised and characterised by experimental and theoretical techniques. All complexes containing Kramers lanthanide ions [Ln3+=Ce ( 1 ), Nd ( 3 ), Sm ( 4 ), Dy ( 6 ), DyY ( 6′′ ), Er ( 8 ), ErY ( 8′′ ), Yb ( 10 )] showed field-induced slow magnetic relaxation, characteristic of single-molecule magnetism and purely of molecular origin. In contrast, all non-Kramers lanthanide ions [Ln3+=Pr ( 2 ), Tb ( 5 ), Ho ( 7 ), Tm ( 9 ), Y3+ ( 11 ) is diamagnetic and non-lanthanide] did not show any slow magnetic relaxation. The variation in the electronic structure and accompanying consequences across the complexes representing all Kramers and non-Kramers lanthanide ions were investigated. The origin of the magnetic properties and the extent to which the axial donor–acceptor interaction involving the lanthanide ions and an electron-deficient orbital of palladium affects the observed magnetic and electronic properties across the lanthanide series are presented. Unique consistent electronic and magnetic properties of isostructural complexes spanning the lanthanide series with properties dependent on whether the ions are Kramers or non-Kramers are reported.  相似文献   

7.
Magneto optical devices based on the Faraday effects of lanthanide ion have attracted much attention. Recently, large Faraday effects were found in nano‐sized multinuclear lanthanide complexes. In this study, the Faraday rotation intensities were estimated for lanthanide nitrates [LnIII(NO3)3?n H2O: Ln=Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm) and EuIII complexes with β‐diketone ligands, using magnetic circular dichroism. Eu ions exhibit the largest Faraday rotation intensity for 7F05D1 transitions, and high‐symmetry fields around the Eu ions induce larger Faraday effects. The molecular design for the enhancement of Faraday effects in lanthanide complexes is discussed.  相似文献   

8.
Interaction of a series of lanthanide cations (Ln3+) with a symmetrical octamethyl-substituted cucurbituril (OMeQ[6]) has been investigated. X-ray single-crystal diffraction analysis has revealed that the interaction results in the formation of adducts of OMeQ[6] with aqua complexes of lanthanide cations ([Ln(H2O)8]3+), Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb in OMeQ[6]–Ln(NO3)3–H2O systems. However, no solid crystals were obtained from systems containing La, Ce, Pr, Nd and Sm. X-ray diffraction analysis has revealed that although the solid adducts fall into two isomorphous groups, there are no significant differences in the interactions between OMeQ[6] and [Ln(H2O)8]3+ complexes and in the corresponding supramolecular assemblies. Thermodynamic parameters for the interaction between OMeQ[6] and [Ln(H2O)8]3+ complexes based on isothermal titration calorimetry experiments show two periods corresponding to the above two systems, with the lighter lanthanide cations preferring to remain in solution and the heavier lanthanide cations forming crystalline solids. Electron spectroscopy has shown that interaction of OMeQ[6] with lanthanide cations could provide a means of isolating heavier lanthanide cations from their lighter counterparts.  相似文献   

9.
Luminescent lanthanide-containing chiral liquid crystalline polymers are graft-copolymerised using poly(methylhydrogeno)siloxane (PMHS), crosslinking agent, liquid crystalline monomer and lanthanide complexes. The chemical structures of the monomers are characterised by FTIR, 1?H NMR and elemental analyses. The mesomorphic properties and phase behaviour are investigated by differential scanning calorimetry, thermogravimetric analysis, polarising optical microscopy and X-ray diffraction. The polymers containing less than 9 mol% of the crosslinking units reveal reversible mesomorphic phase transition, wide mesophase temperature ranges and high thermal stability. With the introduction of lanthanide complex units, the polymers are enabled with the significant luminescent properties. The temperature dependence of fluorescence intensity was studied in the liquid crystalline phase. The IR imaging shows that the lanthanide complex units evenly distribute in polymers.  相似文献   

10.
A novel photoluminescent room‐temperature liquid‐crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)3(NO3)3] (Ln=La, Pr, Sm, Gd, Tb, Dy; LH=(E)‐5‐(hexyloxy)‐2‐ [{2‐(2‐hydroxyethylamino)ethylimino]methyl}phenol) have been synthesized and characterized by FTIR, 1H and 13C NMR, UV/Vis, and FAB‐MS analyses. The ligand coordinates to the metal ions in its zwitterionic form. The thermal behavior of the compounds was investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The ligand exhibits an enantiotropic hexagonal columnar (Colh) mesophase at room temperature and the complexes show an enantiotropic lamellar columnar (ColL) phase at around 120 °C with high thermal stability. Based on XRD results, different space‐filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism. The ligand exhibits intense blue emission both in solution and in the condensed state. The most intense emissions were observed for the samarium and terbium complexes, with the samarium complex glowing with a bright‐orange light (ca. 560–644 nm) and the terbium complex emitting green light (ca. 490–622 nm) upon UV irradiation. DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine‐coordinate structure for the lanthanide complexes.  相似文献   

11.
Liquid crystalline adducts of lanthanide tris(β-diketonates) with 5,5′-diheptadecyl-2,2′-bipiridine forming a nematic mesophase were obtained. Molar constants of magnetic birefringence and the magnetic susceptibility anisotropy of synthesized complexes were determined according to the magnetic birefringence in solution. The values of magnetic susceptibility anisotropy are two orders of magnitude higher than those of organic liquid crystals.  相似文献   

12.
Luminescent ?uorinated chiral liquid crystalline oligomers containing Eu(III) complexes (Eu-LCOs) with good liquid crystalline properties and obvious luminescence properties were prepared using Poly(methylhydrogeno)siloxane (PMHS), chiral liquid crystalline monomer (M1), ?uorinated liquid crystalline monomer (M2), ?uorinated Eu(III) complex (M3). The chemical structures, liquid crystalline behaviours of Eu-LCOs were characterised by various experimental techniques. The introduction of small quantity of ?uorinated Eu(III) complexes endowed the oligomers with excellent luminescence properties. The Eu(III) complexes did not change the liquid crystalline textures of the oligomers. Fourier transform infrared imaging showed that Eu(III) complexes were evenly distributed in oligomers. In order to express the mutual effect and distribution of the components, a structural representation of Eu-LCOs was established. The Eu-LCOs displayed wide mesophase temperature ranges and reversible mesomorphic phase transitions. The Eu-LCOs can emit soft red light when being excited. Luminescence intensities of Eu-LCOs gradually increased with an increase of Eu(III) complexes from 0 to 1.0 mol%. However, the luminescence intensities of Eu-LCOs decreased monotonically with the increase of temperature in liquid crystalline phase.  相似文献   

13.
The lanthanide 2,6-naphthalenedicarboxylates series of the formulas Ln2(ndc)3·nH2O, where Ln = lanthanides from La(III) to Lu(III); ndc - C10H6(COO)22−; n = 4, 4.5 or 5 have been prepared by the precipitation method. All obtained products were examined and characterized by elemental analysis, FTIR spectroscopy, simultaneous thermal analyses TG-DSC and TG-FTIR, X-Ray diffraction patterns as well as luminescence measurements. The crystalline compounds form three isostructural groups: Ce-Sm; La and Eu-Dy; Ho-Lu. In all complexes, the ndc2− ligand appears in the deprotonated form. Heating of the complexes resulted in the multi-steps decomposition process. The dehydration process leads to the formation of stable crystalline Ln2ndc3 compounds which further decompose to the corresponding lanthanide oxides (air atmosphere). In argon atmosphere they decompose with releasing of water, carbon oxides and naphthalene molecules. The luminescence properties of Eu(III), Nd(III), Tb(III) and Er(III) complexes were investigated. The complexes of Eu(III) and Tb(III) emitted red and green light when excited by ultraviolet light whereas Nd(III) and Er(III) display emissions in the NIR region.  相似文献   

14.
Until now, although there are many examples of studying the magnetic properties of Schiff base binuclear lanthanide complexes, the relationship between the structure and magnetic properties of the complexes still is worth further investigation in order to improve the magnetic properties of Schiff base lanthanide complexes. In this work, we successfully obtained two series of binuclear Ln complexes by in situ reaction of 4-diethylaminosalicylaldehyde, benzoic hydrazide and different lanthanide salts at 80°C under solvothermal conditions, namely, [Ln2(L)3(NO3)3]·CH3CN·CH3OH·H2O [Ln = Dy ( 1 ), Ho ( 2 ), Gd ( 3 ) L = deprotonated 4-diethylamino salicylaldehyde benzoylhydrazine], [Ln2(L)4(CH3COO)]CH3COO·CH3CN [Ln = Dy ( 4 ), Ho ( 5 ), Gd ( 6 )]. The complex 1 contains three Schiff base ligands L, two Dy (III) ions, and three NO3. The ligand H1L is formed by in situ Schiff base reaction with 4-diethylaminosalicylaldehyde and benzoic hydrazide with the participation of Ln (NO3)3. When replacing Ln (NO3)3 with Ln (OAc)3, obtained three μ2-OAc bridged binuclear Ln (III) complexes. The magnetic study showed that complex 4 exhibits field-induced single-molecule magnet (SMM) behavior while complex 1 does not show any SMMs behavior. In addition, we have studied the magnetocaloric effect of complexes 3 and 6 , their maximum −ΔSm values are 21.37 J kg−1 K−1 and 15.32 J kg−1 K−1, respectively, under ΔH = 7 T and T = 2 K.  相似文献   

15.
Liquid crystalline complexes of the formula [Ln(LH)3(DOS)3] have been synthesized, where Ln is a trivalent rare earth-ion (Y, La-Lu, except Pm), LH is the ligand N-octadecyl-4-tetradecyloxysalicylaldimine and DOS is the dodecyl sulphate counterion. Although the Schiff 's base ligands do not exhibit mesomorphism, the complexes do (SmA phase). The mesophase behaviour of these compounds has been investigated by polarizing optical microscopy, differential scanning calorimetry, high temperature X-ray diffraction and thermogravimetric analysis. The stoichiometry of the complexes remains constant throughout the lanthanide series.  相似文献   

16.
Structural analyses indicate that the ligand and lanthanide ions form mononuclear 10-coordinate ([Ln L2 · (NO3)2] · NO3 [Ln(III) = La, Sm, Nd, and Yb; L is chromone-3-carbaldehyde-(isonicotinoyl) hydrazone) complexes with 1 : 2 metal-to-ligand stoichiometry. DNA-binding studies show that the ligand and its lanthanide complexes can bind to calf thymus DNA via an intercalation mode with binding constants of 105 (mol L?1)?1, and the lanthanide complexes bind stronger than the free ligand alone. Antioxidant activities of the ligand and lanthanide complexes were determined by superoxide and hydroxyl radical scavenging methods in vitro. The ligand and complexes possess strong scavenging effects, and the lanthanide complexes show stronger antioxidant activities than the ligand and some standard antioxidants, such as vitamin C.  相似文献   

17.
Lewis-base adducts of tris(β -diketonato)lanthanide(III) complexes were prepared, where the β -diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β -diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.  相似文献   

18.
The synthesis and liquid crystalline properties of lanthanide complexes with different but structurally related Schiff's base ligands are described. The complexes all contain nitrate counterions and have the stoichiometry [Ln(LH)3 (NO3)3], where Ln is a trivalent rare-earth ion (La, Nd, Gd or Ho) and LH is a Schiff's base ligand. None of the Schiff's base ligands exhibits mesomorphism, but some of the complexes do (SmA phase). It is shown that the presence or absence and the position of substituents on the ligand determine whether or not the complexes show mesomorphism. The thermal behaviour of these compounds has been investigated by hot stage polarizing microscopy and differential scanning calorimetry.  相似文献   

19.
Two types of isostructural complexes of lanthanide chlorides with diglyme have been synthesized. These are mononuclear molecular complexes [LnCl3(diglyme)(THF)] (Ln = Eu ( 1 ), Gd ( 2 ), Dy ( 3 ), Er ( 4 ), Yb ( 5 ); diglyme = diethylen glycol dimethyl ether) and binuclear molecular complexes [LnCl3(diglyme)]2 (Ln = Dy ( 3d ), Er ( 4d ), Yb ( 5d )). Complex 1 was obtained by the reaction of [EuCl3(DME)2] with diglyme in THF. The complexes 2 – 5 and 3d – 5d resulted from reactions of LnCl3·6H2O, (CH3)3SiCl and diglyme in THF. The mononuclear complexes 2 – 5 crystallized directly from the solutions where the reactions of lanthanide compounds with diglyme took place. Recrystallizations of the powder products of the same reactions from dichloromethane resulted in the binuclear complexes 3d – 5d . Reactions of lanthanide bromide hydrates, (CH3)3SiBr and diglyme in THF achieved mononuclear molecular complexes [LnBr3(diglyme)(L)] (Ln = Gd, L = H2O ( 6 ); Ln = Ho, L = THF ( 7 )). Crystals of 6 and 7 were grown by recrystallization from dichloromethane. The lanthanide atoms (Ln = Eu–Yb) are seven‐coordinated in a distorted pentagonal bipyramidal fashion in all reported complexes, 1 – 7 and 3d – 5d . Four oxygen atoms and three halide ions are coordinated to lanthanide atoms in 1 – 7 , [LnX3(diglyme)(L)]. Four chloride ions, two bridging and two nonbridging, and three oxygen atoms are coordinated to lanthanide atoms in 3d – 5d , [LnCl3(diglyme)]2.  相似文献   

20.
A meso-substituted unsymmetrical porphyrin liquid crystal, 5-(4-myristyloxy)phenyl-10,15,20-triphenyl porphyrin, and a series of its lanthanide complexes, (lanthanide ions: Gd, Tb, Dy, Ho and Er) with acetylacetone were synthesized and characterized by elemental analyses, molar conductances, UV-Vis, IR and 1H?NMR spectra. A structure is proposed in which the porphyrin is as a tetradentate ligand and acetylacetonate is bidentate to the lanthanide. Luminescence spectra show that quantum yields of the Q band fluorescence are in the region 0.027–0.191. DSC data and an optical textural photo using a polarizing microscope indicates that the compounds have liquid crystalline character.  相似文献   

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