Binuclear Lanthanide Complexes Research Articles

Slow magnetic relaxation and photoluminescence behaviors of dilanthanide complexes bearing N8O2 donor macrocyclic ligand

On account of the complicated magnetic exchange interactions between lanthanide ions, binuclear lanthanide complexes have broad application prospect in the field of single-molecule magnets. Therefore, it is necessary to develop reasonable bridging ligands to manipulate the directional assembly of binuclear lanthanide complexes. Herein, we selected the macrocyclic ligand LN8O2 to build up two new dilanthanide complexes [Ln2(LN8O2) (OpyO)2(H2O)2](NO3)2 (1-Ln, Ln = Dy, Tb; LN8O2 = hexamethyl-tetraaza-dioxe-dipyrazolacycloicosaphane-2,9,12,19-tetraene; OpyOH = 2-pyridinol-1-oxide). Dynamic magnetic studies show that 1-Dy exhibits slow relaxation behavior under a 1 kOe applied field. Further fitting analysis of relaxation times gives the effective energy barrier of 38.2 cm−1, and reveals that the slow magnetic relaxation behavior is dominated by the Orbach and Raman processes. High-resolution luminescence emission spectrum indicates the energy gap of 36.8 cm−1 between the ground state and the first excited state, consistent with the magnetic measurement results. 1-Tb exhibits brilliant characteristic green light emission under UV light excitation. The absolute quantum yield of 1-Tb is 44.8%, and its first-order fitted decay lifetime is 779.21 μs at room temperature. This study provides the way for directional construction of high-performance molecular materials with magnetic and optical dual-function.

Binuclear Lanthanide Complexes Based on 4-Picoline-N-oxide: From Sensitized Luminescence to Single-Molecule Magnet Characteristics

Lanthanide complexes featuring luminescent and/or single-molecule magnet (SMM) characteristic(s) are proposed candidates to develop molecule-based spintronics, memory, and quantum information processing (QIP) device architectures. Herein, we report on the luminescent and/or SMM characteristic(s) of charge-neutral binuclear lanthanide complexes─[Ln2Cl6(4-picNO)4(μ2-4-picNO)2]·2H2O (Ln3+ = Tb3+ ([Tb2]) or Dy3+ ([Dy2]); 4-picNO = 4-picoline-N-oxide). The Dy and Tb complexes show 4-picNO-sensitized luminescence with quantum yields in the solid state of 0.14% and 88%, respectively. The luminescent Dy complex is an SMM with a magnetization reversal barrier (Ueff) = 20.6(4) cm–1 under zero applied magnetic field, whereas the Tb complex is not an SMM. The facile preparation of [Ln2Cl6(4-picNO)4(μ2-4-picNO)2]·2H2O complexes showing high luminescence quantum yield (Tb3+) and SMM characteristics (Dy3+) might prove useful toward the designing of analogue luminescent-SMM hybrids suitable for technological applications.

Chelating chloride using binuclear lanthanide complexes in water.

Halide recognition by supramolecular receptors and coordination complexes in water is a long-standing challenge. In this work, we report chloride binding in water and in competing media by pre-organised binuclear kinetically inert lanthanide complexes, bridged by flexible -(CH2)2- and -(CH2)3- spacers, forming [Ln2(DO3A)2C-2] and [Ln2(DO3A)2C-3], respectively. These hydrophilic, neutral lanthanide coordination complexes are shown to bind chloride with apparent association constants of up to 105 M-1 in water and in buffered systems. Hydroxide bridging was observed in these complexes at basic pH, which was proven to be overcome by chloride. Thus, these lanthanide complexes show promise towards chloride recognition in biology and beyond. The results described here have clearly identified a new area of anion coordination chemistry that is ripe for detailed exploration.

Synthesis and luminescence of binuclear lanthanide complexes with 4,6-bis(diphenylphosphino)pyrimidine dioxide as a bridging ligand

Five new isostructural binuclear complexes [Ln2L2(H2O)2(NO3)6] (Ln = Sm, Eu, Gd, Tb, and Dy) based on 4,6-bis(diphenylphosphino)pyrimidine dioxide (L) have been synthesized, and their luminescence properties have been studied. The complexes consist of two nine-coordinated Ln(III) atoms linked by two L ligands in the O,O´-bridging manner. The Gd3+ complex possesses ligand-centered emission, while its Tb3+ and Eu3+ analogs exhibit metal-centered phosphorescence only. At the same time, the Sm3+ and Dy3+ complexes show both metal- and ligand-centered emission. In the complexes studied, the ligand L sensitizes the Tb3+ emission most effectively due to the relatively high triplet energy level (23900 cm−1). Moreover, mixed-metal complexes [Tb2xEu2(1-x)L2(H2O)2(NO3)6] (x = 0.9, 0.8, 0.6, 0.4, 0.2) have been synthesized, whose emission color can be tuned from green to yellow and red through adjusting of the Tb/Eu ratio.

Structures and magnetic properties of two series of Schiff base binuclear lanthanide complexes

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.

Photocontrollable Magnetism and Photoluminescence in a Binuclear Dysprosium Anthracene Complex.

By incorporating photoreactive anthracene moieties into binuclear Dy2O2 motifs, we obtain two new compounds with the formulas [Dy2(SCN)4(L)2(dmpma)4] (1) and [Dy2(SCN)4(L)2(dmpma)2(CH3CN)2] (2), where HL is 4-methyl-2,6-dimethoxyphenol and dmpma is dimethylphosphonomethylanthracene. Compound 1 contains face-to-face π-π interacted anthracene groups that meet the Schmidt rule for a [4 + 4] photocycloaddition reaction, while stacking of the anthracene groups in compound 2 does not meet the Schmidt rule. Compound 1 undergoes a reversible single-crystal-to-single-crystal structural transformation upon UV-light irradiation and thermal annealing, forming a one-dimensional coordination polymer of [Dy2(SCN)4(L)2(dmpma)2(dmpma2)]n (1UV). The process is concomitant with changes in the magnetic dynamics and photoluminescent properties. The spin-reversal energy barrier is significantly increased from 1 (55.9 K) to 1UV (116 K), and the emission color is changed from bright yellow for 1 to weak blue for 1UV. This is the first binuclear lanthanide complex that exhibits synergistic photocontrollable magnetic dynamics and photoluminescence. Ab initio calculations are conducted to understand the magnetostructural relationships of compounds 1, 1UV, and 2.

Syntheses, Characterization, and X-ray Crystal Structure of Binuclear Lanthanide Complexes Assembled with Schiff Base and Acetate

Herein we reported the binuclear complexes of the 1-(pyridin-2-yl)-2-(pyridin-2-ylmethylene)hydrazine ligand (HL) [Ln2(HL)2(CH3COO)6].n(H2O) (Ln = Y, Pr, Gd and Er). The binuclear complexes are characterized by IR and physical measurement. Spectroscopic evidence indicated that the Schiff base HL behave an N3 coordination tridentate ligand. The complexes are formulated as [{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1)(h2-OOCH3)2}{h1:h2:m2-OOCH3}2{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1))(h2-OOCH3)2}].n(H2O). The structure of the praseodymium complex was elucidated by X-ray diffraction analysis. Suitable crystals were grown by slow evaporation of methanol solution. The asymmetric unit of the compound contains two neutral ligand molecules, two Pr3+ ions, four acetate anions acting in h2-OOCH3 mode, two acetate anions acting in h1:h2:m2-OOCH3 mode, and three uncoordinated water molecules. The praseodymium atom is ten coordinated and the coordination sphere is best described as a distorted bicapped square antiprism. The PrIII···PrIII distance is 4.2777(6) Å and the bridging angle Pr—O—Pr and O—Pr—O are respectively 115.8(3)° and 64.2(3)°. The structure is consolidated by intra and intermolecular hydrogen bond.

Photovoltaic Properties of Polymer Composites Doped with Binuclear Lanthanide Complexes Derived from 3,6-Dipyridin-2-YL-1,2,4,5-Tetrazine With Carbacylamidophosphate Ligands

Photovoltaic Properties of Polymer Composites Doped with Binuclear Lanthanide Complexes Derived from 3,6-Dipyridin-2-YL-1,2,4,5-Tetrazine With Carbacylamidophosphate Ligands

Multifunctional Binuclear Ln(III) Complexes Obtained viaIn SituTandem Reactions: Multiple Photoresponses to Volatile Organic Solvents and Anticounterfeiting and Magnetic Properties

The design and synthesis of simple lanthanide complexes with multiple functions have been widely studied and have faced certain challenges. Herein, we successfully synthesized the series of binuclear lanthanide complexes [Ln2(L1)2(NO3)4] (HL1 = 2-amino-1,2-bis(pyridin-2-yl)ethanol; Ln = Dy (Dy2), Tb (Tb2), Ho (Ho2) Er (Er2)) via the in situ self-condensation of Ln(NO3)3·6H2O-catalyzed 2-aminomethylpyridine (16 steps) under solvothermal conditions. Dy2 was mixed with different volatile organic solvents, and photoluminescence tests demonstrated that it showed an excellent selective photoresponse to chloroform (CHCl3). Sensing Tb2 on different organic solvents under the same conditions showed that it exhibited excellent selective photoresponse to methanol (CH3OH). Even under EtOH conditions, Tb2 could selectively respond to small amounts of CH3OH. To the best of our knowledge, achieving a selective photoresponse to various volatile organic compounds by changing the metal center of the complex is difficult. Furthermore, we performed anticounterfeiting tests on Tb2, and the results showed significant differences between the anticounterfeiting marks under white light and ultraviolet light conditions. The alternating current susceptibilities of Dy2 suggested that it was a typical single-molecule magnet (SMM) (Ueff = 93.62 K, τ0 = 1.19 × 10-5 s) under a 0 Oe dc field. Ab initio calculations on Dy2 indicated that the high degrees of axiality of the constituent mononuclear Dy fragments are the main reasons for the existence of SMM behavior.

A series of lanthanide complexes with 2,4-dimethylbenzoic acid and 2,2:6′,2″-terpyridine: Supramolecular structures, thermal decomposition mechanism and photoluminescence

Six new binuclear lanthanide complexes [Ln(2,4-DMBA)3(terpy)(H2O)]2 (Ln = Eu (1), La (2), Pr (3), Nd (4), Sm (5), Gd (6)) (2,4-DMBA = 2,4-dimethylbenzoate; terpy = 2,2:6′,2″-terpyridine) and four mononuclear complexes [Ln(2,4-DMBA)3(terpy)(H2O)] (Ln = Dy (7), Ho (8), Er (9), Tb (10)) have been synthesized. Complexes 1–6 and 7–10 are isomorphous, adopting interesting structures. In the structures of complexes 1–6, two nine-coordinated Ln(III) centers are linked by two 2,4-DMBA ligands in bridging mode. The other two 2,4-DMBA ligands coordinate with one Ln(III) cation in monodentate and chelating modes. In the structures of complexes 7–10, the Ln(III) center is eight-coordinated. Complexes 1–6 and 7–10 can each aggregate to form one-dimensional and two-dimensional supramolecular structures. Thermal decomposition of complexes 1–10 has been investigated by TG-DSC/FTIR. Interestingly, all of the complexes exhibit a similar three-step decomposition process. The Eu(III) and Tb(III) complexes show strong red and green visible light luminescence. Finally, fluorescence lifetimes and intrinsic quantum yields have been calculated for complexes 1 and 10.

Binuclear Lanthanide(III) Complexes with Chiral Ligands: Dynamic Equilibria in Solution and Binding with Nucleotides Studied by Spectroscopic Methods.

Binuclear lanthanide complexes of Eu(III) and Sm(III) were obtained in the presence of chiral ligand 1,2-(R,R+S,S)-N,N'-bis(2-pyridylmethylene),2-diamine. An unusual structure of the Eu(III) compound with two lanthanide atoms connected through two chlorines was determined by X-ray crystallography. In solution, the dimer coexists with a monomeric complex, and the stability of the binuclear form depends on the solvent and concentration. The dimer-monomer equilibrium was monitored by circularly polarized luminescence (CPL) measured on a Raman optical activity (ROA) spectrometer, where both forms provided large CPL anisotropic ratios of up to 5.6×10-2 . Monomer formation was favored in water, whereas the dimer was stabilized in methanol. When mixed with adenosine phosphates, AMP gave much smaller CPL than ADP and ATP, indicating a high affinity of the Eu (III) complex for the phosphate group, which in connection with the ROA/CPL technique can be developed into a bioanalytical probe.

Regulating the single-molecule magnetic properties of phenol oxygen-bridged binuclear lanthanide complexes through the electronic and spatial effect of the substituents

Series of Dy2 SMMs displayed the nearly maximum tenfold increase in energy barrier and the hysteresis temperature increased from zero to 2.5 K using the electronic and spatial effect on substituent of the bridging ligand and co-ligands.

Supramolecular structures, thermal decomposition mechanism and heat capacity of the novel binuclear Tb(III) and Dy(III) complexes with 2,3-dimethoxybenzoic acid and 5,5′-dimety-2,2′-bipyridine

Two novel binuclear lanthanide complexes [Tb(2,3-DMOBA)3(5,5′-DM-2,2′-bipy)]2·C2H5OH (1) and [Dy(2,3-DMOBA)3(5,5′-DM-2,2′-bipy)]2·C2H5OH (2) (2,3-DMOBA = 2,3-dimethoxybenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimety-2,2′-bipyridine) have been successfully synthesized and structurally validated by single-crystal diffraction. The results of single-crystal analyses indicate the complexes contains one free ethanol molecule, and each center Ln(III) is nine-coordinated, exhibiting a distorted monocapped square anti-prismatic coordination geometry. The two center Ln(III) are bound by four 2,3-DMOBA ligands, two of which are bridging bidentate and the other two are bridging–chelating. The adjacent binuclear complexes can form 1D supramolecular structure by a pair of alternating identical C–H···O hydrogen bonding interactions, which further form 2D sheet structures. The thermal behavior of these complexes is investigated by TG-DSC/FTIR. What is more, the heat capacities of the complexes 1–2 are measured by DSC at 259.15–346.15 K, and the result indicates that the heat capacity values of the complexes gradually increased with the increase in temperature. In addition, the thermodynamic functions values (HT − H298.15K) and (ST − S298.15K) of the complexes 1–2 are calculated according to the fitted polynomial equations and the thermodynamic equation. The luminescence property of complex 1 is studied.

Construction of NIR luminescent nanoscale lanthanide complexes with new flexible Schiff base ligands

Four mono- and bi-nuclear lanthanide complexes [LnL1(NO3) (H2O)DMF] (Ln = Nd (1) and Yb (2)) and [Ln2 (L2)2(OAc)2] (Ln = Nd (3) and Yb (4)) were synthesized by using two new Schiff base ligands with long (CH2)2NH(CH2)2 backbone. The lengths of the Schiff base ligands are about 1.8 nm. The bi-nuclear lanthanide complexes 3 and 4 have nanoscale structures with sizes of approximately 0.7 nm × 1.1 nm × 1.6 nm. For 3, the molar ratio of Nd:Br:O obtained by the energy dispersive X-ray spectroscopy analysis is in agreement with the crystal structure. The chromogenic Schiff base ligands in 1–4 can efficiently transfer energy to lanthanide ions, thus, these complexes exhibit the typical NIR luminescence of lanthanide ions. Interestingly, 3 and 4 have higher NIR emission quantum yields (Φem) than 1 and 2, respectively.

Sandwich quadruple-decker binuclear lanthanide(III) complexes based on clamshell-type phthalocyanine ligand: synthesis and physicochemical studies

A series of heteroleptic quadruple-decker bis[lanthanide(III)] complexes based on a flexible spacer-linked phthalocyanine ligand of clamshell-type, denoted sandwich-clamshell complexes, have been prepared. Complexation of 1,1’-[benzene-1,2-diylbis(methanediyloxy)]-bis[9(10),16(17),23(24)-tri-tert-butylphthalocyanine] (clam,tBuPc2H4, 1) with [2(3),9(10),16(17),23(24)-tetra-tert-butylphthalocyaninato] lanthanide(III) acetates [tBuPcLnOAc, 2a–d; Ln = Eu (a), Gd (b), Tb (c), Lu(d)] afforded quadruple-deckers clam, tBuPc4Ln2 (3a–d) with good to excellent yields. The complexes reveal intrinsic UV–Vis–NIR absorption by analogy to classical double-decker phthalocyaninates, while demonstrating high thermal stability up to 350 °C. At the same time, a combination of 1H NMR, electrochemistry and SQUID magnetometry supported by DFT theoretical calculations indicates that bis(phthalocyanine) subunits in 3 are in close contact mainly governed by the spacer group and, in some extent, by the presence of bulky tert-butyl peripheral substituents in the four phthalocyanine decks.

Syntheses, characterization, DNA/HSA binding ability and antitumor activities of a family of isostructural binuclear lanthanide complexes containing hydrazine Schiff base

Three dinuclear lanthanide complexes, [Ln2(L)2(μ3-OAc)4(H2O)2]⋅2H2O (Ln = La (1), Eu (2) and Dy (3), HL = N’-(2-hydroxybenzylidene) nicotinohydrazide), have been synthesized and characterized by IR, elemental analysis and X-ray single-crystal diffraction. Crystallographic study revealed that the representative complex 1 displays a discrete dinuclear structure with a distorted tricapped trigonal prismatic geometry around La(III) ion. The interaction of complexes 1–3 with CT-DNA was investigated by absorption spectra, fluorescence quenching and viscosity, which reveals that the complexes bind to CT-DNA with a moderate intercalative mode. The complexes exhibited obvious DNA cleavage activities in the presence of H2O2. All complexes could bind to human serum albumin (HSA) with medium affinity through static mode; thus, HSA could effectively transport complexes. Furthermore, three complexes exhibited specific cytotoxicity to A549 cancer cells in micromole magnitude than other cancer cells tested and less toxicity than cisplatin for normal human cells HUVEC, in which massive cell apoptosis was induced by complexes through producing DNA damage and suppressing DNA synthesis.Communicated by Ramaswamy H. Sarma

Construction of lanthanide complexes based on 2,6‐dimethylbenzoic acid and 5,5′-dimethyl-2,2′-bipyridine: Supramolecular structures, thermodynamic properties and luminescence

By using conventional solution method, two novel binuclear lanthanide complexes, [Eu(2,6-DMBA)3(5,5′-DM-2,2′-bipy)]2(1), and [Sm(2,6-DMBA)3(5,5′-DM-2,2′-bipy)]2(2) (2,6-DMBA = 2,6-dimethylbenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimethy-2,2′-bipyridine), have been synthesized at room temperature. The two complexes are characterized by element analysis, single-crystal X-ray diffraction analyses and powder X-ray diffraction. The single-crystal analyses results indicate they are isomorphous in the monoclinic space group of P2(1)c. The binuclear complexes 1 and 2 are linked to form 1D, 2D supramolecular structures through the same C–H⋯O hydrogen bonding interactions. The thermal decomposition process of these complexes is investigated by TG-DSC/FTIR technology and the FTIR spectra of the escaped gas also are measured. In addition within a temperature range from 295.15 K to 410.15 K, heat capacities of the title complexes are measured by a DSC instrument, which indicates that no phase transition occurs in this range, and the heat capacity values of the complexes gradually increases with rising temperature. Not only that, the thermodynamic functions values (HT-H298.15K) and (ST-S298.15K) of the complexes 1 and 2 are calculated according to the fitted polynomial equations and the thermodynamic equation. The luminescent behaviour of complex 1 is investigated in the solid state. The complex 1 with Eu3+ ion shows strong red luminescence behaviour, and the luminescence lifetime and fluorescent quantum yield are calculated to be 1.442 ms and 18.96%.

A series of new lanthanide complexes with 2‐bromo‐5‐methoxybenzoic acid and 5,5′‐dimethyl‐2,2′‐bipyridine: Crystal structures, thermal behavior, luminescent and magnetic properties

Four new binuclear lanthanide complexes [Ln(2‐Br‐5‐MOBA)3(5,5′‐DM‐2,2′‐bipy)]2 (Ln = Gd(1), Tb(2), Dy(3), Er(4); 2‐Br‐5‐MOBA = 2‐bromo‐5‐methoxybenzoate; 5,5′‐DM‐2,2′‐bipy = 5,5′‐dimethyl‐2,2′‐bipyridine) have been successfully synthesized and then further characterized by infrared spectra, single‐crystal X‐ray diffraction, elemental analyses and Powder X‐ray diffraction (PXRD). Complexes 1–3 are isostructure with the coordination number of nine, while the complex 4 is eight‐coordinated exhibiting a different structure. Nevertheless, the complexes 1–4 form the same 1D, 2D and 3D supramolecular structures by hydrogen bonding (C‐H···Br and C‐H···O) and π–π stacking interactions. Thermal behavior of complexes 1–4 was studied by TG/DSC‐FTIR techniques. The luminescent spectra of complexes 2 and 3 were investigated at room temperature, which exhibits characteristic luminescence of Tb3+ and Dy3+ ions, respectively. The luminescence decay curve of the complex 2 was measured, which follows double‐exponential decay law. The luminescence lifetime of complex 2 is 0.693 ms. What's more, the magnetic properties of complexes 1–4 have been investigated by measuring the magnetic susceptibility in the temperature range of 2–300 K.

Two Novel Binuclear Lanthanide Complexes with 2,5‐Dichlorobenzoic Acid and 5,5’‐Dimethyl‐2,2’‐bipyridine: Crystal Structures, Luminescence and Thermal Properties

AbstractTwo novel binuclear lanthanide complexes [Ln(2, 5‐DClBA)3(5,5’‐DM‐2,2’‐bipy)(H2O)]2(5,5’‐DM‐2,2’‐bipy) (Ln=Eu(1), Tb(2)); 2,5‐DClBA=2,5‐dichlorobenzoate; 5,5’‐DM‐2,2’‐bipy=5,5’‐dimethyl‐2,2’‐bipyridine) have been successfully synthesized via conventional solution method and then characterized by single‐crystal X‐ray diffraction and elemental analysis. These two binuclear complexes differ from other reported binuclear complexes, because the free neutral ligands are not common in crystal structure. The complexes are isomorphic, which have the same coordination number of eight with a distorted square antiprismatic molecular geometry. The binuclear units feature hydrogen bonding (O−H⋅⋅⋅N and C−H⋅⋅⋅Cl) and π‐π stacking interactions assemble the adjacent molecular units into 1D, 2D and 3D supramolecular novel structures. It is worth noting that the novel 1D supramolecular structure is formed by the hydrogen bonding interaction between the nitrogen atoms of free 5,5’‐DM‐2,2’‐bipy ligand and the oxygen atom of the coordination water molecule. The thermal decomposition mechanism of the two complexes were studied by TG/DSC‐FTIR techniques. Additionally, the luminescence spectra and lifetime have been studied in detail. The results indicate that Eu3+ ion and Tb3+ ion could be sensitized by ligands and thus emitted intense characteristic red and green luminescence, respectively.

Crystal structure, thermochemical and fluorescent properties of two novel binuclear lanthanide complexes with 3-chloro-4-methoxybenzoic acid and 5,5′-dimethy-2,2′-bipyridine

Two novel binuclear lanthanide complexes, [Ln(3-Cl-4-MOBA)3(5,5′‐DM‐2,2′‐bipy)]2(5,5′‐DM‐2,2′‐bipy) (Ln = Eu(1), Gd(2)), 3-Cl-4-MOBA = 3-chloro-4-methoxybenzoate; 5,5′‐DM‐2,2′‐bipy = 5,5′-dimethy-2,2′-bipyridine) have been successfully synthesized under hydrothermal conditions. The complexes are characterized by single-crystal X-ray diffraction and elemental analysis. Complexes 1 and 2 are isomorphous, and each metal center is eight-coordinated with a distorted square-antiprism coordination geometry. The binuclear units are assembled into 1D, 2D and 3D supramolecular structures by weak hydrogen bonds (CH···O and CH···Cl) and π–π stacking interactions. Thermal behavior of the complexes 1 and 2 was determined by TG/DSC-FTIR techniques.Heat capacities of the complexes are measured by a DSC instrument in the temperature range of 283.15–393.15 K. Based on the heat capacities date, the thermodynamic functions (HT-H298.15K) and (ST-S298.15K) were obtained. The activation energy E values of the first decomposition stage for complexes 1 and 2 were calculated by integral iso-conversional nonlinear (NL-INT) method. The fluorescence spectra and lifetime of complex 1 (Eu3+ ion) were studied in depth.