Structural and magnetic properties of Ln(III) complexes with diimines and crotonato as a bridging ligand

Five new lanthanide complexes displaying crotonato bridges have been prepared: [Gd₂(crot)₆(H₂O)₄] · 4(bpa) (1); [Ho₂(crot)₇]_n · (Hbpa) (2); [Gd₂(crot)₆(bipy)₂] (3); [Ho₂(crot)₆(bipy)₂] (4) and [Nd₂(crot)₆(H₂O)₃]_n (5), where bipy=2,2^′-bipyridine; bpa=di(2-pyridyl)amine; crot=crotonato. The compounds were characterized by magnetic susceptibility measurements and their crystal structures were determined by single crystal X-ray diffraction. These studies showed complexes 1, 3 and 4 to be dimers while structures 2 and 5 are polymeric in nature.     

Synthesis and derivatization of halflanthanidocene aryl(alk)oxide complexes

The reaction of halflanthanidocene aryloxides Cp^R′Ln(OAr^tBu,R)₂ (Ln = Y, La, Lu; Cp^R′ = C₅Me₅, C₄Me₄H; R = H, Me) and halflanthanidocene alkoxides [(C₅Me₅)Ln(OCH₂CMe₃)₂]₂ (Ln = Y, Lu) with trimethylaluminum (TMA) was investigated. Monomeric Cp^R′Ln(OAr^tBu,R)₂, derived from the ortho-tBu-substituted OC₆H₂tBu₂-2,6-R-4 (R = H, Me) ligands, form mono(tetramethylaluminate) complexes Cp^R′Ln(OAr^tBu,R)(AlMe₄) for the smaller lanthanide metal centers yttrium and lutetium. Such an [aryloxide] → [aluminate] ligand exchange was not observed at the larger lanthanum metal center. The mobility of the tetramethylaluminate ligands of complexes Cp^R′Ln(OAr^tBu,R)(AlMe₄) (Ln = Y, Lu) was examined by variable-temperature (VT) ¹H NMR spectroscopy, revealing two signals for bridging and terminal methyl groups at lower temperatures. The treatment of complexes Cp^R′Ln(OAr^tBu,R)(AlMe₄) with donor solvent d₈-THF gave Cp^R′Ln(OAr^tBu,R)(Me)(d₈-THF)₂ (Ln = Y, Lu) with terminal methyl groups, according to a donor-induced aluminate cleavage reaction. Dimeric [(C₅Me₅)Ln(OCH₂CMe₃)₂]₂ (Ln = Y, Lu) was synthesized from (C₅Me₅)Ln(NiPr₂)₂(THF) and reacted with two equivalents of TMA per Ln center to yield monomeric bis(TMA) adduct complexes (C₅Me₅)Ln(OCH₂CMe₃)₂(AlMe₃)₂(Ln = Y, Lu). VT NMR spectroscopic studies confirmed a high mobility of the Ln(μ-OCH₂CMe₃)(μ-Me)AlMe₂ moieties at an ambient temperature. Both bis(TMA) adduct complexes were characterized by X-ray structure analysis.     

A family of lanthanide-containing molecular open frameworks with high porosity: [Ln(abdc)(Habdc), nH2O]∞ with Ln = La-Eu and 8 ? n ? 11

Reactions in water between the di-sodium salt of amino terepthalic acid (C₈H₃NO₄Na₂) and a lanthanide chloride lead to a family of 3D-coordination polymers with general chemical formula [Ln(C₈H₃NO₄)(C₈H₄NO₄), O]_∞ where Ln = La-Eu (except Pm) and 8 ? n ? 11. All these compounds are isostructural. High quality single crystals of [Ln(C₈H₃NO₄)(C₈H₄NO₄), nH₂O]_∞ with Ln = La-Sm (except Pm) and 8 ? n ? 11 have been obtained by slow diffusion in agar-agar gels. The crystal structure has been solved for the Nd-containing compound. This compound crystallizes in the cubic system, space group Ia-3 (no. 206) with a = 26.8056(5) Å. The crystal structure can be described as the juxtaposition of large channels with square cross-section.The channels are filled by highly disordered crystallization water molecules. The dehydration of the compounds by freeze-drying is possible and most of the crystallization water molecules can be removed without destruction of the molecular skeleton. The partially dehydrated compounds have general chemical formula [Ln(abdc)(Habdc), 2H₂O]_∞ with Ln = La-Eu except Pm. The porosity of the Nd-containing compound has been estimated by computational methods to 2170 m² g⁻¹. This dehydrated compound reversibly binds water when exposed to wet atmosphere restoring the initial hydrated phase.     

Dinuclear metal phosphonates and -phosphates

The reaction of Cu(II) or Cd(II) salts with 2,4,6-iPr₃C₆H₂PO₃H₂, 2,4,6-iPr₃C₆H₂CH₂PO₃H₂ or 2,6-iPr₂C₆H₃OPO₃H₂ in the presence of strong chelating nitrogen ligands such as 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 2-pyridylpyrazole (pypz) or 3,5-dimethyl pyrazole (dmpz) as the ancillary ligands afforded dinuclear copper or cadmium complexes [Cu₂(2,4,6-iPr₃C₆H₂PO₃H)₄(bpy)₂] (4), [Cu₂(2,6-iPr₂C₆H₃OPO₃H)₂(bpy)₂(OAc)₂(CH₃OH)₂]·(CH₃OH) (5), [Cd₂(2,6-iPr₂C₆H₃OPO₃H)₄ (bpy)₂(CH₃OH)₂]·2(CH₃OH) (6), [Cd₂(2,6-iPr₂C₆H₃OPO₃H)₄(phen)₂] (7), [Cu₂(2,6-iPr₂C₆H₃OPO₃H)₂(PyPz)₂(CH₃OH)₂] (8) and [Cu₂(2,4,6-iPr₃C₆H₂CH₂PO₃H)₂(DMPz)₂Cl₂]·(CH₃OH) (9) The molecular structures of 4-7 are grossly similar. The common structural features in these complexes are that the two metal centers are bridged by two bidentate [RPO₂(OH)]⁻ ligands generating a central eight-membered ring. Each of the metal centers also contains a chelating nitrogen ligand and a monodentate phosphonate or a phosphate ligand. In 5 and 6 other terminal ancillary ligands are also present. In compound 8, each of the two copper centers contains a monodentate [RPO₂(OH)]⁻ ligand along with a molecule of methanol. The two coppers are bridged by two monoanionic pyridylpyrazole ligands. The molecular structure of 9 is similar to that of 4-7. However, in 9 each of the two copper centers contain only terminal monodentate ligands in the form of two chlorides and a pyrazole. Magnetic studies on all of these copper complexes reveal an anti-ferromagnetic behavior at low temperatures. In addition, these complexes were found to be artificial nucleases and can convert supercoiled pBR322 DNA form I into nick form II in 1 min in the presence of an external oxidant through a hydrolytic and/or an oxidative pathway.     

Towards [CpRh(bpy)(H2O)]-promoted P450 catalysis: Direct regeneration of CytC

The organometallic complex pentamethylcyclopentadienyl rhodium 2,2′-bipyridin ([Cp^∗Rh(bpy)(H₂O)]²⁺) was applied as regeneration catalyst for cytochrome C (CytC). Direct reduction of CytC-bound Fe^III was achieved in this model system pointing towards a potential usefulness of this concept to promote cell-free P450 catalysis. In addition, controlled in situ provision with hydrogen peroxide was performed using [Cp^∗Rh(bpy)(H₂O)]²⁺ resulting in improved CytC-catalyzed sulfoxidation of thioanisol This work represents the first step towards the direct-[Cp^∗Rh(bpy)(H₂O)]²⁺ catalyzed regeneration of P450 monooxygenases and peroxidases.     

Structure of binuclear Rh(II) carboxylato complexes with 2,2-bipyridine and an unprecedented rhodium wire with Rh4 core

Structures of rhodium(II) binuclear complexes [Rh₂(OOCCH₃)₂(bpy)₂(H₂O){(CH₃)₂CHOH}][B(C₆H₅)₄]₂ · H₂O (1), [Rh₂Cl₂(OOCCH₃)₂(bpy)₂] · 2H₂O (2), [Rh₂Br₂(OOCCH₃)₂(bpy)₂] · 3H₂O (3), and [Rh₂I₂(OOCCH₃)₂(bpy)₂] (4), as well as an unprecedented wire with infinite Rh-Rh chain, {[Rh₄(μ-OOCH)₄(bpy)₄](BF₄)}_n · 0.5nC₄H₈O₂ (5), have been determined and discussed. Mass spectra of complexes [Rh₂(OOCMe)₂(bpy)₂(H₂O)₂](MeCOO)₂ and [Rh₂(OOCMe)₂(phen)₂(H₂O)₂](MeCOO)₂ have showed stability of polynuclear cations with rhodium in oxidation states in the range +1.25 to +1.75.     

Mononuclear arene ruthenium complexes containing 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine as chelating ligand: Synthesis and molecular structure

The mononuclear cations of the general formula [(η⁶-arene)RuCl(pdpt)]⁺ (pdpt = 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine; arene = C₆H₆ (1); C₆H₅Me (2); p-PrⁱC₆H₄Me (3); C₆Me₆ (4)) have been synthesised from 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine (pdpt) and the corresponding chloro complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-C₆H₅Me)Ru(μ-Cl)Cl]₂, [(η⁶p-PrⁱC₆H₄Me)Ru(μ-Cl)Cl]₂ and [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂, respectively. The X-ray crystal structure analyses of [1][PF₆] · (C₆H₆)_2.5 and [2][PF₆] · (CH₃CN)₂ reveal a typical piano-stool geometry around the metal centre and in the crystal packing a complexed networks of intermolecular interactions.     

Synthesis and structures of four new compounds of the copper(II)-carboxylate-pyridinecarboxamide system

The synthesis and structural characterization of four new copper compounds with formula [Cu(crot)₂(isn)₂(Hcrot)·H₂O] (1), [Cu(oda)(isn)₂] (2), [Cu(crot)₂(nia)₂·(H₂O)] (3) and [Cu(oda)(nia)] (4) (crot = trans-2-butenoate, oda = oxydiacetate, isn = isonicotinamide, nia = nicotinamide) is reported. The complexes extend into 3D supramolecular structures by means of hydrogen bonds. EPR spectra of powder samples of the compounds are reported.     

Assembly of coordination networks: Role of the different M(II)-cysteate chain in structural diversification

In this paper, we have presented the synthesis and crystal structures of five coordination polymers, namely, {[Ni₂(cysteate)₂(bpy)₂(H₂O)₂]·3H₂O}_n (1), {[Cu₂(cysteate)₂(bpy)₂(H₂O)₂]·4H₂O}_n (2), {[Mn₂(cysteate)₂(bpy)(H₂O)₄](bpy)·H₂O}_n (3), {[Zn₂(cysteate)₂(bpy)(H₂O)₄](bpy)·H₂O}_n (4), {[Cd(cysteate)(bpy)(H₂O)]·4H₂O}_n (5), using homochiral l-cysteate and 4,4′-bipyridine (bpy) as mixed ligands, reacted with Ni(II), Cu(II), Mn(II), Zn(II) and Cd(II) ions, respectively. When different metal centers being used, l-cysteate gave rise to three different architectures based on coordination polymeric chains: (1) a helical chain, which is further connected by bpy pillars to generate a racemic twofold 3D (4².8⁴)-lvt net in 1 and 2; (2) a zigzag chain, which is further linked by bpy pillars into a homochiral 2D brick-wall structure in 3 and 4; (3) a zigzag chain, which is further linked by bpy pillars into a homochiral 2D 4⁴ grid network in 5. These results indicate that the metal-directed M(II)-cysteate chain has an important effect on the structural diversification of such complexes.     

Antitumor properties of some titanocene chalcogenates

Five chalcogen-coordinated bis(η⁵-cyclopentadienyl)titanium(IV) chalcogenolates were tested against fluid Ehrlich ascites tumor for antitumor properties: the titanocene phenolates (C₅H₅)₂TiCl(2,4,6-OC₆H₂Cl₃) (I) and (C₅H₅)₂Ti(OC₆F₅)₂ (II); the titanocene thiophenolate (C₅H₅)₂Ti(SC₆F₅)₂ (III); the titanocene dithiolene chelate (C₅H₅)₂Ti[cis-1,2-S₂C₂ (CN)₂] (IV); and the titanocene selenophenolate (C₅H₅)₂TiCl(SeC₆H₅) (V). The best antitumor activity and an optimum cure rate of 100% were observed in the case of the pentafluorophenyl derivatives II and III, followed by IV and V which induced cure rates of 90 and 80% respectively. These results confirm that bis(η⁵-cyclopentadienyl)titanium(IV) diacido complexes can be widely varied at the position of the acido ligands without loss of antitumor potency. The titanocene derivatives described in the present study are the first neutral mercapto and seleno titanocene derivatives for which strong antiproliferative properties have been shown.     

pH-value-controlled assembly of photoluminescent zinc coordination polymers

By pH-value adjustment, the reactions of zinc salt, 1,3,5-benzenetricarboxylic acid (H₃btc) and 4,4′-bipyridine (bpy) yield three coordination polymers, formulated as [Zn₃(btc)₂(bpy)(H₂O)₂]_n (1), [Zn(Hbtc)(bpy)(H₂O)]_n · 3nH₂O (2) and [Zn(Hbtc)(bpy)(H₂O)]_n · 4nH₂O (3), respectively. The structure of 1 is a 3D network containing channels filled with bpy ligands. Compound 2 consists of twofold interpenetrating (10,3)-b networks, while compound 3 is a 2D layer structure. The fluorescent studies reveal that they exhibit intense violet luminescence in solid state.     

Structure and properties of cobalt ortho-phenylenediacetate coordination polymers with rigid dipyridyl ligands

Divalent cobalt coordination polymers containing both ortho-phenylenediacetate (ophda) and rigid dipyridyl ligands 4,4′-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethylene (dpee) display different topologies depending on carboxylate binding mode, tether length, and inclusion of charged species. [Co(ophda)(H₂O)(dpee)]_n (1) displays a common (4,4) grid layer motif. Use of the shorter bpy tether afforded {[Co₂(ophda)₂(bpy)₃(H₂O)₂][Co(bpy)₂(H₂O)₄](NO₃)₂·2bpy·7H₂O}_n (2) or [Co(ophda)(bpy)]_n (3) depending on cobalt precursor. Compound 2 manifests 5-connected [Co₂(ophda)₂(bpy)₃(H₂O)₂]_n pillared bilayer slabs with rare 4⁸6² SnS topology and entrained [Co(bpy)₂(H₂O)₄]²⁺ complex cations. The 3-D coordination polymer 3 has an uncommon 4,6-connected binodal (4⁴6²)(4⁴6¹⁰8) fsc topology, and shows ferromagnetic coupling (J = +1.5(2) cm⁻¹) along 1-D spiro-fused [Co(OCO)₂]_n chain submotifs.     

Complexes of lanthanoid salts with macrocyclic ligands. Part 25. Lanthanoid trifluoroacetate complexes with 12-crown-4, 15-crown-5, and 18-crown-6 ethers

The lanthanoid trifluoroacetates, Ln(TFA)₃, react with 12-crown-4, 15-crown-5, and 18-crown-6 ethers to give complexes with various metal:ligand ratios, 1:1, 3:2, and 2:1. The following complexes have been isolated and characterized: Ln(CF₃CO₂)₃· (C₈He₁₆O₄), Ln = La, Ce, Pr; [Ln(CF₃CO₂)₃]₃· (C₈H₁₆O₄)₂, Ln = Pr, Eu, Er; [Ln(CF₃CO₂)₃]₂· (C₈H₁₆O₄), Ln = Pr, Nd, Sm; [Ln(CF₃CO₂)₃]₂· (C₁₀H₂₀O₅), Ln = La---Eu; Ln(CF₃CO₂)₃·(C₁₂H₂₄O₆), Ln = La---Eu; [Ln(CF₃CO₂)₃]₂·(C₁₂H₂₄O₆), Ln = Y, Eu---Er, Yb. Thermogravimetric data show that the 2:1 complexes are usually thermally more stable. The 2:1 complexes with the 15-membered polyether undergo a slow hydrolysis in the presence of traces of water, which yields the hydroxo complex [Ln₂(CF₃CO₂)₃(OH)(C₁₀H₂₀O₅)₂] [Ln₂(CF₃CO₂)₈]. The vibrational spectra confirm the coordination of the coronands; the Δν_as(CCO) shifts are not large, which point to a moderate interaction between the polyethers and the metal ions. Magnetic susceptibilities and X-ray powder diagrams have been measured.High-resolution excitation and emission spectra have been analysed for the europium-containing compounds. The spectrum of Eu(CF₃CO₂)₃·3H₂O indicates the presence of a single species with low symmetry, in agreement with the crystal structure data for the isostructural Pr-salt. The anhydrous salt Eu(CF₃CO₂)₃ generates an emission spectrum with broad bands and probably contains several, closely related polymeric species. The spectrum of [Eu(CF₃CO₂)₃]₂(C₁₀H₂₀O₅) is consistent with the presence of two chemically different sites for Eu(III); the emission bands are broad. The double salt AgEu(CF₃CO₂)₄·3CH₃CN has also been investigated; the observed transitions point to the presence of a species with idealized D_2d symmetry. The emission spectrum of [Eu(CF₃CO₂)₃]₂(C₁₂H₂₄O₆) displays sharp bands and reveals the presence of two different sites for the metal ion with efficient energy transfers between them. One of the species may have a relatively high symmetry.In solution, all the complexes are non-electrolytes in acetonitrile and propylene carbonate and close to 1:1 electrolytes in methanol. Some dissociation occurs in acetonitrile for the 2:1 complexes with 18-crown-6 ether. On the other hand, ¹H NMR spectra of the lanthanum 1:1 complexes with 12- crown-4 and 18-crown-6 ethers indicate no dissociation of the complexed polyether. Log β₁ is greater than 6 for both complexes; it is equal to 4.4 for the samarium 1:1 complex with 18-crown-6 ether.     

Stereospecific interactions between dinuclear complex cations involving square-planar [Pt(II)(μ-S)2(bpy)] (bpy = 2,2′-bipyridine) frameworks derived from optically active octahedral Co(III) units with d- or l-penicillaminates

The reaction of the octahedral mononuclear complex, trans(N)-[Co(l-pen-N,O,S)₂]⁻ (pen = penicillaminate), with [PtCl₂(bpy)] (bpy = 2,2′-bipyridine) stereoselectively gave an optically active S-bridged dinuclear complex, [Pt(bpy){Co(l-pen)₂}]Cl · 3H₂O (2Cl · 3H₂O), whose structure is enantiomeric to the previously reported [Pt(bpy){Co(d-pen)₂}]Cl · 3H₂O (1Cl · 3H₂O). The mixture of equimolar amounts of 1Cl · 3H₂O and 2Cl · 3H₂O in H₂O crystallizes as [Pt(bpy){Co(d-pen)₂}]_0.5[Pt(bpy){Co(l-pen)₂}]_0.5Cl · 7H₂O (3Cl · 7H₂O), in which the enantiomeric complex cations 1 and 2 are included in the ratio of 1:1. The crystal structures of 2Cl · 3H₂O and 3Cl · 7H₂O were determined by X-ray crystallography, and compared with that of 1Cl · 3H₂O. The structural feature for 2 is essentially consistent with that for 1, except for the absolute configurations around the octahedral Co(III) center. The optically active complex cation 2 exists as a monomer, accompanied by no intermolecular interactions in the π-electronic systems of bpy moieties. In the crystals of 3Cl · 7H₂O, on the other hand, the enantiomeric complex cations, [Pt(bpy){Co(d-pen)₂}]⁺ and [Pt(bpy){Co(l-pen)₂}]⁺, are arranged alternately while overlapping the bpy planes along a axis, and the π electronic system of the bpy framework in [Pt(bpy){Co(d-pen)₂}]⁺ interacts with those in [Pt(bpy){Co(l-pen)₂}]⁺. Differences between the crystal structures of 2Cl · 3H₂O and3Cl · 7H₂O significantly reflect their diffuse reflectance spectra. In aqueous solution, each cation in both 2Cl · 3H₂O and 3Cl · 7H₂O is comparatively put on a free environment without such intermolecular interactions.     

Synthesis, structures, photoluminescent and electroluminescent properties of boron complexes with anilido-imine ligands

Syntheses of three new N-arylanilido-arylimine bidentate Schiff base type ligand precursors, ortho-C₆H₄[NH(2,6-ⁱPr₂C₆H₃)](CHNAr¹) [Ar¹ = p-FC₆H₄ (2a); C₆H₅ (2b); p-OMeC₆H₄ (2c)], and their four-coordinated boron complexes, ortho-C₆H₄[N(2,6-ⁱPr₂C₆H₃)](CHNAr¹)BF₂ [Ar¹ = p-FC₆H₄ (3a); C₆H₅ (3b); p-OMeC₆H₄ (3c)] are described. The boron complexes 3a-3c were synthesized from the reaction of BF₃(OEt₂) with the lithium salt of their corresponding ligand. All complexes were characterized by ¹H and ¹³C NMR spectroscopy and molecular structures of complexes 3a and 3c were determined by X-ray crystallography. The photophysical properties of complexes 3a-3c were briefly examined. All three complexes display bright green fluorescence in solution and in the solid state. Electroluminescent devices with complex 3c as the emitter were fabricated. These devices were found to give green emission with maximum current efficiency of 2.92 cd/A and maximum luminance of 670 cd/m².     

Diastereoisomerically pure pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2-bipyridine: structural, electrochemical and spectral studies

Pyrazole-3,5-dicarboxylate-bridged dinuclear ruthenium(II) and osmium(II) complexes of 2,2^′-bipyridine of composition [(bpy)₂Ru(pzdc)Ru(bpy)₂](ClO₄) · H₂O (1) and [(bpy)₂Os(pzdc)Os(bpy)₂](ClO₄) · H₂O (2) have been obtained in high yield and have been separated to their homochiral (ΛΛ/ΔΔ) rac (1a, 2a) and heterochiral (ΛΔ/ΔΛ) meso (1b, 2b) diastereoisomers. The distinctive structural features of these diastereoisomers have been characterized by 1-D and 2-D ¹H NMR spectroscopy. The X-ray crystal structure of rac-[(bpy)₂Os(pzdc)Os(bpy)₂](ClO₄) · H₂O (2a) has been determined. The electrochemical and electronic spectral studies have established that there remain difference in properties and hence difference in intermetallic communication between the diastereoisomeric forms in each case.     

Structural change of supramolecular coordination polymers of itaconic acid and 1,10-phenanthroline along lanthanide series

Five new supramolecular lanthanide coordination polymers with three different structures, {[La₂(IA)₃(phen)₂] · 2H₂O}_n (1), {[Ln(IA)_1.5(phen)] · xH₂O}_n [x = 1, Ln = Eu (2); x = 0.25, Ln = Dy (3)], and [Ln(IA)_1.5(phen)]_n [Ln = Er (4); Yb (5)], were prepared by hydro- and solvothermal reactions of lanthanide chlorides with itaconic acid (H₂IA) and 1,10-phenanthroline (phen), and structurally characterized by single crystal X-ray diffraction. 1 Comprises 1-D double-chains that are further assembled to a 3-D supramolecular structure via hydrogen bonds and π-π stacks between phen molecules. 2 and 3 have 2-D infinite networks which are further constructed to form 3-D supramolecular architectures with 1-D channels by π-π aromatic interactions. 4 and 5 have 2-D layer structures consisting of three types of rings which are further architectured to form 3-D supramolecular structures by C-H?O hydrogen bonds. The H₂IA ligands are all completely deprotonated and exhibit tetra-, penta-, and hexadentate coordination modes in the titled complexes. The high-resolution emission spectrum of 2 shows only one Eu³⁺ ion site in 2, which is in agreement with the result of X-ray diffraction. And the magnetic property and the thermal stability of 2 were also investigated.     

Synthesis,characterization, structure and luminescence studies of dinuclear gold(I) alkynyls of bis(diphenylphosphino)alkyl- and aryl-amines

A series of alkynylgold(I) bis(diphenylphosphino)alkyl- and aryl-amine complexes, [{Ph₂PN(R)PPh₂}Au₂(CCR′)₂] [R = ⁿPr, R′ = Ph (1), C₆H₄OMe-p (2), C₆H₄Me-p (3), C₆H₄Cl-p (4); R = C₆H₄OMe-p, R′ = Ph (5)], has been synthesized. The X-ray crystal structures of 1 and 2 revealed the presence of short intramolecular Au⋯Au contacts with the distances of 2.8404(8) and 3.0708(7) Å. The luminescence behavior of the complexes were studied.     

Assembly and upconversion luminescence of lanthanide-organic frameworks with mixed acid ligands

Three new lanthanide coordination polymers based on mixed acid ligands [Ln(oba)(ox)_0.5(H₂O)₂]_n (Ln = Y (1); Er (2); Yb (3). H₂oba = 4,4′-oxybis (benzoic acid); H₂ox = oxalic acid) were prepared by hydrothermal reactions and characterized by single-crystal X-ray diffraction. In these complexes, lanthanide ions are bridged by oba ligands to form 1D double-stranded chains, which are further connected by ox ligands, resulting in the formation of 2D (4,4) grids. The upconversion emission of the Y:Er-Yb co-doped coordination polymer was studied and the unusual blue emission for the Er(III) complexes was observed, which arises from the ²H_9/2 → ⁴I_15/2 transition and can be explained by three-photon excitation mechanism which is mostly phonon-dependent. The introduction of the oxalate anion without high-energy vibrational groups is beneficial to the increasing intensity of upconversion fluorescence. The magnetic properties of complexes 2 and 3 were investigated. The decrease of χ_MT over the temperature range of 300-2 K and the negative value of θ are due primarily to the splitting of the ligand field of the Er^III and Yb^III ions together with the possible weak antiferromagnetic coupling between the rare earth ions.     

Reduction of structural dimensionality through incorporation of auxiliary ligands in lanthanide tetracyanoplatinates

The synthesis of a series of lanthanide tetracyanoplatinates containing the auxiliary ligands 1,10′-phenanthroline (phen) or 2,2′-bipyridine (bpy) have been carried out by reaction of Ln³⁺ nitrate salts with phen or bpy and potassium tetracyanoplatinate in solvent systems containing dimethylsulfoxide and dimethylformamide. The use of these solvents has lead to the isolation of [{Ln(DMSO)₂(C₁₂H₈N₂)(H₂O)₃}₂Pt(CN)₄](Pt(CN)₄)₂·2C₁₂H₈N₂·4H₂O (Ln = Eu (Eu-1), Tb (Tb-1), Yb(Yb-1)), [Ln(DMF)₃(C₁₂H₈N₂)(H₂O)₂NO₃]Pt(CN)₄ (Ln = La (La-2), Eu (Eu-2), Tb (Tb-2)), and [Ln(DMF)₃(C₁₀H₈N₂)(H₂O)₂NO₃]Pt(CN)₄ (Ln = La (La-3), Sm (Sm-3), Eu (Eu-3), Tb (Tb-3)) in the form of single crystals. Single-crystal X-ray diffraction has been used to investigate their structural features. The use of DMSO versus DMF as the solvent results in markedly different structural features. Eu-1 contains [{Eu(DMSO)₂(C₁₂H₈N₂)(H₂O)₃}₂Pt(CN)₄]²⁺ complex cations where the two Eu³⁺ centers are linked by a trans-bridging Pt(CN)₄²⁻ anion to form a dimeric lanthanide complex cation. An additional uncoordinated Pt(CN)₄²⁻ anion balances charge. Eu-2 and Eu-3 consist of zero-dimensional salts with [Eu(DMF)₃(C₁₂H₈N₂)(H₂O)₂(NO₃)]²⁺ or [Eu(DMF)₃(C₁₀H₈N₂)(H₂O)₂(NO₃)]²⁺ complex cations, respectively, and only non-coordinated Pt(CN)₄²⁻ anions. Photoluminescence measurements illustrate that the Eu³⁺ and Tb³⁺ compounds for all three structure types display enhanced emission due to intramolecular energy transfer from the coordinated cyclic amines.