Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21?000, 22?700, and 23?000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.     

4-[(1,3-二氧代丁基)氨基]苯甲酸稀土配合物的合成、表征及发光性质

在乙醇体系中,由主配体4-[(1,3-二氧代丁基)氨基]苯甲酸(H2L,C11H11NO4)、稀土硝酸盐及辅助配体邻菲啰啉(phen)反应合成了两个系列8个配合物[Ln2(L)3(H2O)4]n(Ln=Sm(1),Eu(2),Tb(3),Dy(4));[Ln2(NO3)2(L)2(phen)2]n(Ln=Sm(5),Eu(6),Tb(7),Dy(8))。用元素分析、红外光谱、摩尔电导、热重分析进行表征,确定了产物的化学组成,推断了相应的结构。测定了室温时固体产物的激发和发射光谱,结果表明:由主辅配体共同配位的三元配合物的发光强度好于无辅助配体参与的二元配合物。测定了三元配合物的荧光寿命,其中铕和铽配合物显示较长的荧光寿命。     

Conjugated ligands modulated sandwich structures and luminescence properties of lanthanide metal-organic frameworks

A conjugated ligand, 2-(carboxylic acid)-6-(2-benzimidazolyl) pyridine (Hcbmp), and a series of Lanthanide metal-organic frameworks (MOFs) [Ln(2)(cbmp)(ox)(3)(H(2)O)(2)](2)·2H(3)O(+)·7H(2)O (Ln = Sm (3), Eu (4), and Gd (5), H(2)ox = oxalic acid) have been designed and assembled. To elucidate how the conjugated ligands modulate the structures and luminescence properties, we carried out the structural characterizations and luminescence studies of complexes 3 and 4, and their corresponding oxalate complexes [Ln(ox)(1.5)(H(2)O)(3)]·2H(2)O (Ln = Sm (1) and Eu (2)) were also investigated for comparison. The changes of luminescence behaviors upon dehydration and D(2)O-rehydration processes are presented and discussed in detail. The results indicated that, the cbmp(-) ligands distribute on both sides of the ox(-)-Ln bilayer network to construct a sandwich structure. Moreover, the lowest triplet state of cbmp(-) ligands can match well the energy levels of the Sm(3+) and Eu(3+) cations which allow the preparation of new Ln-MOF materials with enhanced luminescence properties. Meanwhile, the crystallinity of solid states produces more substantial change in the luminescence behaviors than removal or replacement of effective nonradiative relaxers.     

Two series of novel rare earth complexes with dicyanamide [Ln(dca)2(phen)2(H2O)3][dca].(phen), (Ln = Pr, Gd, and Sm) and [Ln(dca)3(2,2'-bipy)2(H2O)]n, (Ln = Gd, Sm, and La): syntheses, crystal structures, and magnetic properties

Two series of novel complexes, [Ln(dca)(2)(Phen)(2)(H(2)O)(3)](dca).(phen) (Ln = Pr (1), Gd (2), and Sm (3), dca = N(CN)(-), phen = 1,10-phenanthroline) and [Ln(dca)(3)(2,2'-bipy)(2)(H(2)O)](n), (Ln = Gd (4), Sm (5), and La (6), 2,2'-bipy = 2,2'-bipydine), have been synthesized and structurally characterized by X-ray crystallography. The crystal structures of the first series (1-3) are isomorphous and consist of discrete [Ln(dca)(2)(Phen)(2)(H(2)O)(3)]+ cations, dca anions, and lattice phen molecules; whereas the structures of the second series (4-6) are characterized by infinite chains [Ln(dca)(3)(2,2'-bipy)(2)(H(2)O)](n). The Ln(III) atoms in all complexes are nine-coordinated and form a distorted tricapped trigonal prism environment. The three-dimensional frameworks of 1-6 are constructed by intermolecular hydrogen bond interactions. Variable-temperature magnetic susceptibility measurements for complexes 1, 2, 4, and 5 indicate a Curie-Weiss paramagnetic behavior over 5-300 K.     

One-, two-, and three-dimensional arrays of Eu3+-4,4,5,5,5-pentafluoro-1-(naphthalen-2-yl)pentane-1,3-dione complexes: synthesis, crystal structure and photophysical properties

A novel beta-diketone, 4,4,5,5,5-pentafluoro-1-(naphthalen-2-yl)pentane-1,3-dione (HPFNP), which contains polyfluorinated alkyl group, as well as the long conjugated naphthyl group, has been used for the synthesis of a series of new tris(beta-diketonate)europium(III) complexes of the general formula Eu(PFNP)3 x L [where L = H2O, 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (bath)] and characterized by various spectroscopic techniques. The single-crystal X-ray diffraction analysis of Eu(PFNP) 3.bpy revealed that the complex is mononuclear, the central Eu(3+) ion is coordinated by six oxygen atoms furnished by three beta-diketonate ligands, and two nitrogen atoms from a bidentate bipyridyl ligand, in an overall distorted square prismatic geometry. Further, analysis of the X-ray crystal data of the above complex also revealed interesting 1D, 2D, and 3D networks based on intra- and intermolecular hydrogen bonds. The room-temperature PL spectra of the complexes are composed of typical Eu(3+) red emissions, assigned to transitions between the first excited state ((5)D0) and the multiplet ((7)F(0-4)). The results demonstrate that the substitution of solvent molecules by bidentate nitrogen ligands in Eu(PFNP)3 x H2O x EtOH greatly enhances the quantum yields and lifetime values.     

Synthesis, characterizations and luminescent properties of three novel aryl amide type ligands and their lanthanide complexes

Three new aryl amide type ligands, N-(phenyl)-2-(quinolin-8-yloxy)acetamide (L(1)), N-(benzyl)-2-(quinolin-8-yloxy)acetamide (L(2)) and N-(naphthalene-1-yl)-2-(quinolin-8-yloxy)acetamide (L(3)) were synthesized. With these ligands, three series of lanthanide(III) complexes were prepared: [Ln(L(1))(2)(NO(3))(2)]NO(3), [Ln(L(2))(2)(NO(3))(2)(H(2)O)(2)]NO(3).H(2)O and [Ln(L(3))(2)(NO(3))(2)(H(2)O)(2)]NO(3).H(2)O (Ln=La, Sm, Eu, Gd). The complexes were characterized by the elemental analyses, molar conductivity, (1)H NMR spectra, IR spectra and TG-DTA. The fluorescence properties of complexes in the solid state and the triplet state energies of the ligands were studied in detail, respectively. It was found that the Eu(III) complexes have bright red fluorescence in solid state. The energies of excited triplet state for the three ligands are 20325 cm(-1) (L(3)), 21053 cm(-1) (L(2)) and 22831 cm(-1) (L(1)), respectively. All the three ligands sensitize Eu(III) strongly and the order of the emission intensity for the Eu(III) complexes with the three ligands is L(3)>L(2)>L(1). It can be explained by the relative energy gap between the lowest triplet energy level of the ligand (T) and (5)D(1) of Eu(III). This means that the triplet energy level of the ligand is the chief factor, which dominates Eu(III) complexes luminescence.     

Syntheses, structures, and luminescent and magnetic properties of novel three-dimensional lanthanide complexes with 1,3,5-benzenetriacetate

Five novel lanthanide complexes with the formulas [Nd(bta)(H2O)2.4.35H2O]n(1), [Sm(bta)(H2O)2.4.5H2O]n (2), [Eu(bta)(H2O).1.48H2O]n (3), [Tb(bta)(H2O).1.31H2O]n (4), and [Yb(bta)(H2O).H2O]n (5) (H3bta = 1,3,5-benzenetriacetic acid) have been prepared by using the corresponding lanthanide salt and H3bta. The results of an X-ray crystallographic analysis revealed that all the complexes have three-dimensional channel-like structures, in which the bta3- ligands adopt different coordination modes: monodentate and mu2-eta2:eta1-bridging coordination modes in 1, 2, and 5 and mu2-eta1:eta1-bridging and mu2-eta2:eta1-bridging coordination modes in 3 and 4, respectively. Complexes 1 and 2, as well as 3 and 4, are isostructural, respectively, in which all the Ln(III) (Ln = Nd, Sm, Eu, and Tb) atoms are nine-coordinated, while the Yb(III) atoms in complex 5 are eight-coordinated. Both complexes 3 and 4 showed strong luminescence upon excitation, and their luminescence decay curves fit well with single exponential decays of which the lifetime is 0.45 ms for 3 and 1.0 ms for 4. The magnetic properties of the complexes were investigated in the temperature range of 1.8-300 K.     

Synthesis, structure, and characterization of three series of 3d-4f metal-organic frameworks based on rod-shaped and (6,3)-sheet metal carboxylate substructures

Three series of porous lanthanide metal-organic coordination polymers, namely [Cu(bpy)Ln(3)(ip)(5)(Hip)(H(2)O)] [Ln = Er (1a), Y (1b), Eu (1c); bpy = 2,2'-bipyridine, H(2)ip=isophthalic acid], [Cu(3)(bpy)(2)Ln(2)(ip)(6)(H(2)O)(5)] [Ln = Yb (2a), Gd (2b), Tb (2c)], and [Cu(3)Ln(2)(ip)(6)] [Ln = Eu (3a), Gd (3b)] have been synthesized hydrothermally by the reaction of the combination of 3d-4f metal centers and N-/O-donor ligands. X-ray diffraction analyses reveal that polymers 1a-c and 2a-c, as well as 3a, b are isomorphous in structure. Polymers 1a-c consist of 3D alpha-Po networks based on a inorganic rod-shaped secondary building units (SBUs) of {Er(6)Cu(2)(bipy)(2)(O(2)C)(11)} which are 27.03 A in length. Polymers 2a-c also contain 3D alpha-Po networks, constructed from shorter (14.79 A) but similarly rod-shaped SBUs of {Yb(2)Cu(3)(bpy)(2)(O(2)C)(12)}. The structure also contains hydrogen-bonded (H(2)O)(6) chains which can be reversibly dehydrated/rehydrated. Polymers 3a, b contain metal carboxylate substructures which have 2D (6,3) topologies; these layers are bridged by the ip(2-) ligands to give an overall 3D network which contains two sorts of cavities. This series of Ln-Cu coordination polymers are further characterized by antiferromagnetic behavior.     

Syntheses, crystal structures and luminescent properties of new lanthanide(III) organoarsonates

The first examples of lanthanide(III) organoarsonates, Ln(L(1))(H(2)O)(3) (Ln = La (1), H(3)L(1) = 4-hydroxy-3-nitrophenylarsonic acid), Ln(L(1))(H(2)O)(2) (Ln = Nd (2), Gd (3)), and mixed-ligand lanthanide(III) organoarsonates, Ln(2)(HL(1))(2)(C(2)O(4))(H(2)O)(2) (Ln = Nd (4), Sm (5), Eu (6)), were hydrothermally synthesized and structurally characterized. Compounds 1-3 feature a corrugated lanthanide arsonate layer, in which 1D lanthanide arsonate inorganic chains are further interconnected via bridging L(1)(3-) ligands. Compounds 4-6 exhibit a complicated 3D network. The interconnection of the lanthanide(III) ions by the bridging arsonate ligand leads to the formation of a novel 3D framework with long narrow 1D tunnels along the a-axis, with the oxalate anions are located at the above tunnels and bridging with lanthanide(III) ions. Compounds 2 and 4 exhibit the characteristic emission bands of the Nd(III) ion, whereas compound 6 displays the characteristic emission bands of the Eu(III) ion. The magnetic properties of compounds 3-6 were also investigated.     

Highly luminescent bis-diketone lanthanide complexes with triple-stranded dinuclear structure

A new bis-β-diketone, 3,3'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl (BTB), has been designed and prepared for the synthesis of a series of dinuclear lanthanide complexes [Ln(2)(BTB)(3)(C(2)H(5)OH)(2)(H(2)O)(2)] [Ln = Eu (1), Gd (2)], [Ln(2)(BTB)(3)(DME)(2)] [Ln = Nd (3), Yb (4); DME = ethylene glycol dimethyl ether] and [Eu(2)(BTB)(3)(L)(2)] [L = 2,2-bipydine (5); 1,10-phenanthroline (6); 4,7-diphenyl-1,10-phenanthroline (7)]. Complexes 1-7 have been characterized by various spectroscopic techniques and their photophysical properties are investigated. X-ray crystallographical analysis reveals that complexes 1, 3 and 4 adopt triple-stranded dinuclear structures which are formed by three bis-bidentate ligands with two lanthanide ions. The complexes 1 and 3-7 display strong visible red or NIR luminescence upon irradiation at ligand band around 372 nm, depending on the choice of the lanthanide. The solid-state photoluminescence quantum yields and the lifetimes of Eu(3+) complexes are determined and described.     

Highly luminescent, visible-emitting lanthanide macrocyclic chelates stable in water and derived from the cyclen framework

Two new tetraazamacrocyclic ligands are designed with the aim of sensitizing the luminescence of Tb(III) and Eu(III) ions in water: L5 [1,4,7,10-tetrakis[N-(phenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane] and L6 [1,4,7,10-tetrakis[N-(4-phenylphenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane]. These ligands react with lanthanide trifluoromethanesulfonates to yield stable 1:1 complexes in water (log K = 12.89 +/- 0.15 for EuL5). X-ray diffraction on [Tb(L5)(H(2)O)](CF(3)SO(3))(3) (P1 macro, a = 13.308(3) A, b = 14.338(3) A, c = 16.130(3) A, alpha = 101.37(3) degrees, beta = 96.16(3) degrees, gamma = 98.60(3) degrees ) shows the Tb(III) ion lying on a C(4) axis and being 9-coordinate, with one water molecule bound in its inner coordination sphere. The absolute quantum yields are determined in aerated water for the complexes formed with ions used in fluoroimmunoassays (Ln = Sm, Eu, Tb, and Dy). Large values are found for [Tb(H(2)O)(L5)](3+) and [Eu(H(2)O)(L6)](3+), in line with the molecular design of the receptors: 23.1% and 24.7%, respectively. The intense luminescence of these ions results from efficient intersystem crossing and L --> Ln energy transfer processes, as well as from a suitable shielding of the emitting ions from radiationless deactivation.     

Crystal structures and magnetic and luminescent properties of a series of homodinuclear lanthanide complexes with 4-cyanobenzoic ligand

A series of homodinuclear lanthanide(III) complexes with the 4-cba ligand, [La2(4-cba)6(phen)2(H2O)6] (1) and [Ln2(4-cba)6(phen)2(H2O)2] (Ln = Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), and Dy (7); 4-Hcba = 4-cyanobenzoic acid; phen = 1,10-phenanthroline), have been synthesized and structurally characterized by single-crystal X-ray diffraction. In 1, two water molecules bridge two nine-coordinated La ions, and six 4-cba ligands coordinate to the two La ions in terminal mode. In the isostructural complexes 2-7, two eight-coordinated Ln ions are connected by four bidentate 4-cba ligands, and another two 4-cba ligands terminate the two Ln ions. The variable-temperature magnetic properties of 2-7 have been investigated. Complex 7 shows a significant ferromagnetic interaction between Dy(III), while no magnetic interaction exists between Gd(III) ions in 6. In 2-5, the value of chi(M)T decreases with decreasing temperature, but the magnetic interactions between the Ln(III) ions cannot definitely be concluded. Notably, the spin-orbit coupling parameters, lambda, for Sm(III) (216(2) cm(-1)) and Eu(III) (404(2) cm(-1)) have been obtained in 4 and 5, respectively. The strong fluorescent emissions of 4, 5, and 7 demonstrate that ligand-to-Ln(III) energy transfer is efficient and that the coordinated water molecules do not quench their luminescence by the nonradiative dissipation of energy.     

Diverse lanthanide coordination polymers tuned by the flexibility of ligands and the lanthanide contraction effect: syntheses, structures and luminescence

Two new flexible exo-bidentate ligands were designed and synthesized, incorporating different backbone chain lengths bearing two salicylamide arms, namely 2,2'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))bis(N-benzylbenzamide) (L(I)) and 2,2'-(2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl))bis(oxy)bis(N-benzylbenzamide) (L(II)). These two structurally related ligands are used as building blocks for constructing diverse lanthanide polymers with luminescent properties. Among two series of lanthanide nitrate complexes which have been characterized by elemental analysis, TGA analysis, X-ray powder diffraction, and IR spectroscopy, ten new coordination polymers have been determined using X-ray diffraction analysis. All the coordination polymers exhibit the same metal-to-ligand molar ratio of 2?:?3. L(I), as a bridging ligand, reacts with lanthanide nitrates forming two different types of 2D coordination complexes: herringbone framework {[Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)](∞) (Ln = La (1), and Pr (2), m = 1, 2)} as type I,; and honeycomb framework {[Ln(2)(NO(3))(6)(L(I))(3)·nCH(3)OH](∞) (Ln = Nd (3), Eu (4), Tb (5), and Er (6), n = 0 or 3)} as type II, which change according to the decrease in radius of the lanthanide. For L(II), two distinct structure types of 1D ladder-like coordination complexes were formed with decreasing lanthanide radii: [Ln(2)(NO(3))(6)(L(II))(3)·2C(4)H(8)O(2)](∞) (Ln = La (7), Pr (8), Nd (9)) as type III, [Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)·nCH(3)OH](∞) (Ln = Eu (10), Tb (11), and Er (12), m, n = 2 or 0) as type IV. The progressive structural variation from the 2D supramolecular framework to 1D ladder-like frameworks is attributed to the varying chain length of the backbone group in the flexible ligands. The photophysical properties of trivalent Sm, Eu, Tb, and Dy complexes at room temperature were also investigated in detail.     

Heterospin systems constructed from [Cu2Ln]3+ and [Ni(mnt)2]1-,2- Tectons: First 3p-3d-4f complexes (mnt = maleonitriledithiolato)

New heterospin complexes have been obtained by combining the binuclear complexes [{Cu(H(2)O)L(1)}Ln(O(2)NO)(3)] or [{CuL(2)}Ln(O(2)NO)(3)] (L(1) = N,N'-propylene-di(3-methoxysalicylideneiminato); L(2) = N,N'-ethylene-di(3-methoxysalicylideneiminato); Ln = Gd(3+), Sm(3+), Tb(3+)), with the mononuclear [CuL(1)(2)] and the nickel dithiolene complexes [Ni(mnt)(2)](q)- (q = 1, 2; mnt = maleonitriledithiolate), as follows: (1)infinity[{CuL(1)}(2)Ln(O(2)NO){Ni(mnt)(2)}].Solv.CH(3)CN (Ln = Gd(3+), Solv = CH(3)OH (1), Ln = Sm(3+), Solv = CH(3)CN (2)) and [{(CH(3)OH)CuL(2)}(2)Sm(O(2)NO)][Ni(mnt)(2)] (3) with [Ni(mnt)2]2-, [{(CH(3)CN)CuL(1)}(2)Ln(H(2)O)][Ni(mnt)(2)]3.2CH(3)CN (Ln = Gd(3+) (4), Sm(3+) (5), Tb(3+) (6)), and [{(CH(3)OH)CuL(2)}{CuL(2)}Gd(O(2)NO){Ni(mnt)(2)}][Ni(mnt)(2)].CH(2)Cl(2) (7) with [Ni(mnt))(2]*-. Trinuclear, almost linear, [CuLnCu] motifs are found in all the compounds. In the isostructural 1 and 2, two trans cyano groups from a [Ni(mnt)2]2- unit bridge two trimetallic nodes through axial coordination to the Cu centers, thus leading to the establishment of infinite chains. 3 is an ionic compound, containing discrete [{(CH(3)OH)CuL(2)}(2)Sm(O(2)NO)](2+) cations and [Ni(mnt)(2)](2-) anions. Within the series 4-6, layers of discrete [CuLnCu](3+) motifs alternate with stacks of interacting [Ni(mnt)(2)](*-) radical anions, for which two overlap modes, providing two different types of stacks, can be disclosed. The strength of the intermolecular interactions between the open-shell species is estimated through extended Hückel calculations. In compound 7, [Ni(mnt)(2)](*-) radical anions coordinate group one of the Cu centers of a trinuclear [Cu(2)Gd] motif through a CN, while discrete [Ni(mnt)(2)](*-) units are also present, overlapping in between, but also with the coordinated ones. Furthermore, the [Cu(2)Gd] moieties dimerize each other upon linkage by two nitrato groups, both acting as chelate toward the gadolinium ion from one unit and monodentate toward a Cu ion from the other unit. The magnetic properties of the gadolinium-containing complexes have been determined. Ferromagnetic exchange interactions within the trinuclear [Cu(2)Gd] motifs occur. In the compounds 4 and 7, the [Ni(mnt)(2)](*-) radical anions contribution to the magnetization is clearly observed in the high-temperature regime, and most of it vanishes upon temperature decrease, very likely because of the rather strong antiferromagnetic exchange interactions between the open-shell species. The extent of the exchange interaction in the compound 7, which was found to be antiferromagnetic, between the coordinated Cu center and the corresponding [Ni(mnt)(2)](*-) radical anion, bearing mostly a 3p spin type, was estimated through CASSCF/CASPT2 calculations. Compound 6 exhibits a slow relaxation of the magnetization.     

Direct solvothermal growth, crystal structures, and optical properties of one-dimensional lanthanide selenidoarsenate(v) polymers [Ln(dien)2(micro3-AsSe4)] (Ln = Nd, Sm): the first example of an AsSe4(3-) anion acting as a ligand to a lanthanide complex

Two novel lanthanide selenidoarsenates(v) [Ln(dien)2(micro(3)-AsSe(4))] (Ln = Nd 1, Sm 2, dien = diethylenetriamine) were synthesized by the reactions of As(2)O(3) and Se with Nd(2)O(3) or Sm(2)O(3) in dien under solvothermal conditions. 1 and 2 are in the orthorhombic crystal system with Iba2 and Pbca space groups, respectively. The [AsSe(4)](3-) anion acts as a tridentate micro(3)-AsSe(4) ligand to bridge the lanthanide [Ln(dien)2](3+) complexes leading to one-dimensional neutral [Ln(dien)(2)(micro(3)-AsSe(4))](infinity) chains. The chains contact through hydrogen bonding to form network structures. The lanthanide center lies within a nine-coordinated environment involving six N atoms of two dien ligands and three Se atoms of two different tetrahedral [AsSe(4)](3-) anions forming a distorted monocapped square antiprism. The novel coordination polymers [Nd(dien)2(micro(3)-AsSe(4))](infinity) and [Sm(dien)2(micro(3)-AsSe(4))](infinity) are the first examples of solvothermally synthesized selenidoarsenates with [AsSe(4)](3-) anion acting as a ligand in lanthanide complexes. The band gaps of 2.11 eV for 1, and 2.18 eV for 2 have been derived from optical absorption spectra. TG-DSC curves show that two compounds remove coordinated dien ligands in a single step.     

Scrutinizing low-spin Cr(II) complexes

The oxidation state of the chromium center in the following compounds has been probed using a combination of chromium K-edge X-ray absorption spectroscopy and density functional theory: [Cr(phen)(3)][PF(6)](2) (1), [Cr(phen)(3)][PF(6)](3) (2), [CrCl(2)((t)bpy)(2)] (3), [CrCl(2)(bpy)(2)]Cl(0.38)[PF(6)](0.62) (4), [Cr(TPP)(py)(2)] (5), [Cr((t)BuNC)(6)][PF(6)](2) (6), [CrCl(2)(dmpe)(2)] (7), and [Cr(Cp)(2)] (8), where phen is 1,10-phenanthroline, (t)bpy is 4,4'-di-tert-butyl-2,2'-bipyridine, and TPP(2-) is doubly deprotonated 5,10,15,20-tetraphenylporphyrin. The X-ray crystal structures of complexes 1, [Cr(phen)(3)][OTf](2) (1'), and 3 are reported. The X-ray absorption and computational data reveal that complexes 1-5 all contain a central Cr(III) ion (S(Cr) = (3)/(2)), whereas complexes 6-8 contain a central low-spin (S = 1) Cr(II) ion. Therefore, the electronic structures of 1-8 are best described as [Cr(III)(phen(?))(phen(0))(2)][PF(6)](2), [Cr(III)(phen(0))(3)][PF(6)](3), [Cr(III)Cl(2)((t)bpy(?))((t)bpy(0))], [Cr(III)Cl(2)(bpy(0))(2)]Cl(0.38)[PF(6)](0.62), [Cr(III)(TPP(3?-))(py)(2)], [Cr(II)((t)BuNC)(6)][PF(6)](2), [Cr(II)Cl(2)(dmpe)(2)], and [Cr(II)(Cp)(2)], respectively, where (L(0)) and (L(?))(-) (L = phen, (t)bpy, or bpy) are the diamagnetic neutral and one-electron-reduced radical monoanionic forms of L, and TPP(3?-) is the one-electron-reduced doublet form of diamagnetic TPP(2-). Following our previous results that have shown [Cr((t)bpy)(3)](2+) and [Cr(tpy)(2)](2+) (tpy = 2,2':6',2"-terpyridine) to contain a central Cr(III) ion, the current results further refine the scope of compounds that may be described as low-spin Cr(II) and reveal that this is a very rare oxidation state accessible only with ligands in the strong-field extreme of the spectrochemical series.     

The synthesis and structure of heteroleptic tris(diimine)ruthenium(II) complexes

The reactions of bidentate diimine ligands (L2) with cationic bis(diimine)[Ru(L)(L1)(CO)Cl]+ complexes (L, L1, L2 are dissimilar diimine ligands), in the presence of trimethylamine-N-oxide (Me3NO) as a decarbonylation reagent, lead to the formation of heteroleptic tris(diimine) ruthenium(II) complexes, [Ru(L)(L1)(L2)]2+. Typically isolated as hexafluorophosphate or perchlorate salts, these complexes were characterised by UV-visible, infrared and mass spectroscopy, cyclic voltammetry, microanalyses and NMR spectroscopy. Single crystal X-ray studies have elucidated the structures of K[Ru(bpy)(phen)(4,4'-Me(2)bpy)](PF(6))(3).1/2H(2)O, [Ru(bpy)(5,6-Me(2)phen)(Hdpa)](ClO(4))(2), [Ru(bpy)(phen)(5,6-Me(2)phen)](ClO(4))(2), [Ru(bpy)(5,6'-Me(2)phen)(4,4'-Me(2)bpy)](PF(6))(2).EtOH, [Ru(4,4'-Me(2)bpy)(phen)(Hdpa)](PF(6))(2).MeOH and [Ru(bpy)(4,4'-Me(2)bpy)(Hdpa)](ClO(4))(2).1/2Hdpa (where Hdpa is di(2-pyridyl)amine). A novel feature of the first complex is the presence of a dinuclear anionic adduct, [K(2)(PF(6))(6)](4-), in which the two potassium centres are bridged by two fluorides from different hexafluorophosphate ions forming a K(2)F(2) bridging unit and by two KFPFK bridging moieties.     

Trinuclear to dinuclear: a radii dependence lanthanide(III) self-assembly coordination behavior of an amide-type tripodal ligand

Lanthanide nitrate complexes with the heptadentate ligand L (6-[2-(2-(diethylamino)-2-oxoethoxy)ethyl]-N,N,12-triethyl-11-oxo-3,9-dioxa-6,12-diazatetradecanamide), [Ln(2)L(NO(3))(6)] (Ln = La, Nd, Sm, Eu, Ho), have been prepared and characterized. The X-ray crystallographic studies show that, in [La(2)L(NO(3))(6)(H(2)O)].H(2)O (1), two complex cations [LaL(H(2)O)](3+) are linked by a hexanitrato anion [La(NO(3))(6)](3)(-) and form a trinuclear cation. In [Nd(2)L(NO(3))(6)(H(2)O)].CHCl(3).1/2CH(3)OH.1/2H(2)O (2), one complex cation [NdL(H(2)O)](3+) and a hexanitrato complex anion [Nd(NO(3))(6)](3)(-) are linked by a bridging NO(3)(-) to form a dinuclear complex. In both complexes, the bridging nitrate is an unusual tetradentate ligand. The metal ions are 12-coordinated in hexanitrato anions and 10-coordinated in complex cations. The chainlike supramolecular structures of La(3+) complex are parallel and have no hydrogen bonds in between, while, in the Nd(3+) complex, a chiral cavity is formed by hydrogen bonds between two adjacent supramolecular chains. These influences are further investigated by assessing the separation efficiency of L and (1)H NMR spectra of its lanthanide nitrate mixtures in solution.     

Assembling process of charged nonanuclear cationic lanthanide(III) clusters assisted by dichromium decacarbonyl hydride

The reaction of Ln(acac)(3).3H(2)O (Ln = Sm, Eu, Gd, Dy, Yb) with K[Cr(2)(CO)(10)(micro-H)] at different molar ratios and solvents leads to the formation of nonanuclear lanthanide hydroxo acetylacetonate complexes of general formula [Ln(9)(OH)(10)(acac)(16)][HCr(2)(CO)(10)]. The compounds are isomorphous, and the common cationic cluster core consists of a novel square antiprismatic arrangement of nine Ln atoms connected by micro(3), micro(4) hydroxo bridges and/or by acetylacetonate ligands as it results from the single-crystal X-ray analysis of the Sm derivative for which the most suitable crystals were obtained.     

Two- and three-dimensional lanthanide complexes: synthesis, crystal structures, and properties

3,5-pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1-9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal-organic framework structures. The complexes {[Ln2(HL)3(H2O)4].2H2O}n (Ln=Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3].3H2O}n (Ln=Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln=Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoledicarboxylic acid were observed, which proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers. The photophysical and magnetic properties have also been investigated.