Synthesis, crystal structure and photophysical properties of europium(III) and terbium(III) complexes with pyridine-2,6-dicarboxamide

The reactions of pyridine-2,6-dicarboxamide with europium(III) and terbium(III) triflates led to the formation of mononuclear complexes of formula [Ln(pcam)₃](CF₃SO₃)₃ (Ln = Eu 1, Tb 2; pcam stands for pyridine-2,6-dicarboxamide). From single-crystal X-ray diffraction analysis, the complexes were found to be isomorphous and isostructural. The [Ln(pcam)₃]³⁺ cations and triflate counterions are connected by intermolecular hydrogen bonds, resulting in a 3D network structure. Both the europium(III) and terbium(III) complexes exhibit efficient ligand sensitized luminescence in the visible region with lifetimes of 1.9 ms and 2.2 ms, respectively, in the solid state.     

The concentration controlled 1D and 2D supramolecular isomers of lanthanide with 2,2’-bipyridyl-3,3’-dicarboxylate and phenanthroline

The reactions of 2,2′-bipyridyl-3,3′-dicarboxylic acid (H₂bpdc) and 1,10-phenanthroline (phen) with lanthanide (III) salts in different concentrations under hydrothermal conditions formed two series of supramolecular isomers of 1D zigzag chains of [Ln(bpdc)_1.5(phen)(H₂O)]_n·3nH₂O (1Ln·3H₂O), and 2D frameworks of [Ln(bpdc)_1.5(phen)(H₂O)]_n (2Ln), (Ln = Ho, Er, Tm, and Yb). At lower concentrations, the supramolecular isomers of 1Ln were formed, in which each isomer has a dinuclear centrosymmetric dimeric unit of [Ln₂(phen)₂(H₂O)₂(μ₂-bpdc)₂]²⁺, and the dimeric units are alternately connected by μ₂-bpdc²⁻ to form a 1D zigzag chain of 1Ln. At higher concentrations, the supramolecular isomers of 2Ln were formed. All the compounds of 2Ln are isomorphous, in which two μ₃-bpdc²⁻ bridge two [Ln(phen)(H₂O)]³⁺ units to yield a 1D double-chains of [Ln₂(phen)₂(H₂O)₂(bpdc)₂]_n²ⁿ⁺, and [Ln₂(phen)₂(H₂O)₂(bpdc)₂]_n²ⁿ⁺ chains are further connected by μ₄-bpdc²⁻ to form a 2D network of [Ln(bpdc)_1.5(phen)(H₂O)]_n. The 2D sheets are combined through the intersheet π-π interactions between the adjacent phen molecules to form a 3D structure of 2Ln. The compounds of Er(III), and Yb(III) exhibit corresponding characteristic photoluminescence in the near-infrared (NIR) region, in which 1Ln and 2Ln show obviously different emission intensity due to their different structures.     

Syntheses, structures, and properties of lanthanide-organic frameworks with flexible disulfide derivative of carboxylate

Reaction of disulfide-containing ligand 6,6′-dithiodinicotinic acid (H₂cpds) with lanthanide metal salts led to three compounds {[Ln₂(cpds)₃(H₂O)₅]·7H₂O}_n (Ln = Gd, 1; Tb, 2; Er, 3) under hydrothermal conditions. The single-crystal X-ray diffraction analysis revealed that complexes 1-3 are isostructural. Two eight-coordinated metal centers are connected with carboxylate groups of H₂cpds to give a binuclear [Ln₂(CO₂)₄] unit. H₂cpds discloses two independent binding modes resulting in the two types of 1-D chains by the connection of [Ln₂(CO₂)₄] unit. Finally, the 1-D chains are linked by H₂cpds to construct a 3-D network with an uncommon twofold interpenetrating 4-connected CdSO₄ structure type (6⁵,8 topology). It is worth noting that polyrotaxane-like motif is also exhibited in the 3-D network. The Tb(III) compound exhibits strong green photoluminescence in the visible region. Furthermore, the magnetic property of the Gd(III) compound has been investigated in the temperature range of 2-300 K. The thermal behaviors and XPRD patterns of three compounds have also been discussed.     

Synthesis and structural characterization of copper(I) complexes bearing N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA): Cytotoxic activity evaluation of a series of water soluble Cu(I) derivatives containing PTA, PTAH and mPTA ligands

New copper(I) complexes containing the water soluble N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA) phosphine have been synthesized by ligand-exchange reactions starting from [Cu(CH₃CN)₄][BF₄] or [Cu(CH₃CN)₄][PF₆] precursors and (mPTA)X (X = CF₃SO₃, I). Depending on the ligand counter ion, the hydrophilic [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a and [Cu(mPTA)₄][(CF₃SO₃)₄(PF₆)] 3c complexes or the iodine-coordinated [Cu(mPTA)₃I]I₃4 species were obtained respectively and fully characterized by spectroscopic methods. Single crystal structural characterization was undertaken for [Cu(mPTA)₃I]I₃·H₂O, 4·H₂O, and [Cu(mPTA)₄][(CF₃SO₃)₂(BF₄)₃] ·0.25H₂O, 3b·0.25H₂O, the latter obtained by crystallization of [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a. The cytotoxicity of analogous tetrahedral homoleptic Cu(I) derivatives [Cu(PTA)₄](BF₄) 1, [Cu(PTAH)₄][Cl₄(BF₄)] 2, [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a and [Cu(mPTA)₄][(CF₃SO₃)₄(PF₆)] 3c was evaluated against a panel of several human tumor cell lines. All the complexes showed in vitro antitumor activity comparable to that of the reference metallodrug cisplatin. Tests performed on cisplatin sensitive and resistant cell lines showed that against human ovarian 2008/C13^* cell line pair, the resistance factor of copper derivatives was roughly 7-fold lower than that of cisplatin, whereas against human cervix cancer A431/A431-Pt cell line pair it was about 2.5-fold lower. These results, confirming the circumvention of cisplatin resistance, support the hypothesis that phosphine copper(I) complexes follow different cytotoxic mechanisms than do platinum drugs.     

Addition of secondary amines to activated alkenes promoted by Pd(II) complexes: Use of ammonium salts as cocatalysts

The complexes [Pd(acac)₂] 1, [Pd(hfa)₂] 2 (hfa = hexafluoroacetylacetonate), [Pd(CF₃CO₂)₂] 3 and [Pd₃(CH₃CO₂)₆] 4 exhibit very different catalytic efficiency in the reaction between secondary amines and activated alkenes. Complexes 1 and 4 generally show an enhanced activity when catalytic amounts of NH₄X salts (X⁻ = low-coordinating anion) are added to the reaction mixtures. On the contrary, the activity of the perfluorurate analogues 2 and 3, which is much higher than that of 1 and 4, is generally scarcely affected by the presence of the NH₄X additive. The cocatalytic effect of NH₄X is comparable with that of strong acids such as CF₃SO₃H. The ammonium salts alone can behave as a catalyst giving an almost quantitative yield of the hydroamination product.     

Bidentate guanidine ligands with ethylene spacer in copper-dioxygen chemistry: Structural characterization of bis(μ-hydroxo) dicopper complexes

The syntheses of the aliphatic bidentate guanidine-amine-hybrid ligands DMEGdmae (L1), TMGdmae (L2), TMGdeae (L3) and DPipGdmae (L4) as well as the reaction of their Cu(I) complexes with molecular oxygen (monitored by UV-Vis spectroscopy) are reported. The molecular structures of 10 bis(μ-hydroxo) dicopper complexes based on these ligands are described. The solid state structures of [Cu₂(μ-OH)₂(DMEGdmae)₂]X₂ (X⁻ = I⁻ (1), CF₃SO₃⁻ (2), SbF₆⁻ (3), PF₆⁻ (4)), [Cu₂(μ-OH)₂(TMGdmae)₂]X₂ (X⁻ = I⁻ (5), CF₃SO₃⁻ (6)), [Cu₂(μ-OH)₂(TMGdeae)₂]Cu₂I₄ (7) and [Cu₂(μ-OH)₂(DPipGdmae)₂]X₂ (X⁻ = CF₃SO₃⁻ (8), SbF₆⁻ (9), PF₆⁻ (10)) show a square-planar distorted coordination of the copper(II) ion. The bis(μ-hydroxo) dicopper complex 1 exhibits a Cu···Cu distance of 2.860(1) Å, which is one of the smallest observed for hydroxo-bridged copper compounds so far. The influence of the anion on the structure of the bis(μ-hydroxo) dicopper(II) unit is analyzed for the reported complexes and a literature overview with emphasis on the structural characteristics of the Cu₂O₂ moiety of bis(μ-hydroxo) dicopper(II) and bis(μ-oxo) dicopper(III) is given.     

Hydrothermal investigation of the lanthanide (Ln=La, Ce, Pr, Nd, Sm) 2,6-pyridinedicarboxylate system

In this paper, two new dipicolinate complexes, Ln₂(dipic)₃(H₂O)₃ (1) with Ln=La, Ce, Pr, Nd, Sm and Ce₃(dipic)₅(H₂O)₂ (2), are described. Hydrothermal synthesis, crystal structure and thermal behaviour of both compounds are described, as well as the magnetic behaviour of the trinuclear complex (2). The structures consist of LaO₇N₂, LaO₇N (1) and CeO₇N, CeO₆N₃ (2) polyhedra linked to form three-dimensional networks. The magnetic study of 2 confirms that it corresponds to a Ce(III)-Ce(IV) molecular compound and that the magnetic interaction is certainly antiferromagnetic. According to the thermogravimetric analysis, thermal decomposition of compounds 1 starts at about 100-130 °C, when 2 is thermally stable up to 250 °C.     

Ligand induced PH bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the PH bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

Structures, fluorescent properties of the Ag(I) compounds based on molecular clips with biphenyl core

Three silver complexes Ag₂(L)₂(NO₃)₂ (1), Ag₂(L)₂(SO₃CF₃)₂(H₂O)_0.5 (2), and [Ag₂(L)₂(NO₃)₂]_n (3) were prepared from molecular clips, 2,2′-Bis(imidazol-1-ylmethyl)-biphenyl (L) and structurally characterized to investigate the structural-luminescent relation. Compound 1 is a bimetallic supramolecular rectangle in which two L ligands are connected by two linearly coordinated Ag(I) ions. Compound 2 is described as a double helicate due to the nature of the twist of the imidazole groups after coordination to Ag(I) centers. In compound 3, the Ag(I) centers are connected by L ligands into a one-dimensional zigzag chain. Solid state and solution fluorescent measurements exhibit the presence of ligand-based emission at 415 and 435 nm of compounds 1 and 2, respectively. It is said that the dihedral angles between the two imidazole rings coordinated to one Ag(I) center affect the emission properties.     

First example of thiostannates with lanthanide-containing counter cations: Solvothermal synthesis, crystal structures and properties of thiostannates with neodymium(III) and gadolinium(III) complexes of bidentate and tridentate amino ligands

Three new lanthanide thiostannates [Ln₂(en)₆(μ₂-OH)₂]Sn₂S₆ (Ln = Nd (1), Gd (2); en = ethylenediamine) and [Gd(dien)₃]₂[(Sn₂S₆)Cl₂] (3) (dien = diethylenetriamine) were first synthesized by treating LnCl₃ with SnCl₄ and S under mild solvothermal conditions. Compounds 1 and 2 are isostructural. They consist of a binuclear lanthanide(III) complex [Ln₂(en)₆(μ₂-OH)₂]⁴⁺ cation and a dimeric [Sn₂S₆]⁴⁻ anion. The anion is built up by two SnS₄ tetrahedra sharing a common edge. The Nd³⁺ and Gd³⁺ ions are in an eight-coordinated environment forming distorted bicapped trigonal prisms. Compound 3 is composed of two monouclear [Gd(dien)₃]³⁺ complex cations, a [Sn₂S₆]⁴⁻ anion, and two chlorine ions. The Gd³⁺ ion has a nine-coordinated environment forming a distorted tricapped trigonal prism. In compounds 1-3, extensive hydrogen bonds are formed leading to three-dimensional networks of anions and cations. The band gaps of 2.42 eV for 1 and 3.17 eV for 2 have been derived from optical absorption spectra. The new lanthanide compounds might be the precursors for ternary lanthanide thiostannates by the heat treatment under nitrogen atmosphere to get rid of organic components.     

Mixed-ligand compounds incorporating quadruply bonded dimolybdenum(II) core: Syntheses, structures and reactivity studies

Reaction of cis-[Mo₂(OAc)₂(CH₃CN)₆][BF₄]₂ with NP-Et,Me (2-ethyl-3-methyl-1,8-naphthyridine) in acetonitrile provides trans-[Mo₂(NP-Et,Me)₂(OAc)₂(CH₃CN)][BF₄]₂ (1). Partial protonation of 1 by HBF₄·Et₂O in acetonitrile leads to trans-[Mo₂(NP-Et,Me)₂(OAc)(CH₃CN)₃][BF₄]₃ (2). In both compounds, NP-R ligands are arranged in a head-to-head (HH) fashion leaving one of the axial sites vacant. Substitution of acetonitriles by NP-Me (3-methyl-1,8-naphthyridine) in trans-[Mo₂(NP-tz)₂(OAc)(CH₃CN)₂][BF₄]₃ provides trans-[Mo₂(NP-tz)₂(OAc)(NP-Me)][BF₄]₃ (3) with retention of configuration. Fully solvated dimolybdenum(II) compound reacts with NP-NH₂ to provide [Mo₂(NP-NH₂)₂(NP-NH)(CH₃CN)₂][BF₄]₃ (4) in which the NP-NH₂ ligands are trans and arranged in a HH fashion. The deprotonated ligand (NP-NH⁻) binds the dimetal unit utilizing naphthyridine nitrogen and amido nitrogen. Treatment of [Mo₂(NP-tz)₂(CH₃CN)₄][CF₃SO₃]₄ with bpym (2,2′-bipyrimidine) followed by crystallization in air provided an oxo complex [Mo₂(NP-tz)₂(μ₂-O)₂(bpym)₂][CF₃SO₃]₄ (5). Compounds 1-5 have been characterized by a variety of spectroscopic techniques and by X-ray crystallography. The reactivity pattern is rationalized based on ligand labilities and thermodynamic stabilities.     

A new gold(III)-aminoethyl imidazolium aurate salt: Synthesis, characterization and reactivity

Tetrachloroauric acid HAuCl₄ reacts with the ionic liquid 1-(2-aminoethyl)-3-methylimidazolium nitrate [NH₂(CH₂)₂ImMe]NO₃, (2b) or its dicationic ammonium salt [NH₃(CH₂)₂ImMe][NO₃]₂, (3) in methanolic solutions to give the novel gold(III)-aminoethyl imidazolium aurate salt [Cl₃AuNH₂(CH₂)₂ImMe][AuCl₄] (4). The reaction of 4 with [ⁿBu₄]Cl gives [NH₂(CH₂)₂ImMe][AuCl₄] (2c) whereas with acetone the dicationic, iminium-functionalized, imidazolium aurate salt [Me₂C=N(H)(CH₂)₂ImMe][AuCl₄]₂ (5) has been isolated. The structures in the solid state of 2c, 3, 4, and 5 have been determined by X-ray diffraction. The electrochemical behaviour of 4 has been examined by Cyclic voltammetry in acetonitrile and compared with 2c and KAuCl₄.     

New ruthenium(II) precursors with the tetradentate sulfur macrocycles tetrathiacyclododecane ([12]aneS4) and tetrathiacyclohexadecane ([16]aneS4) for the construction of metal-mediated supramolecular assemblies

The preparation and structural characterization of several new Ru(II) complexes in which four coordination positions are occupied by the sulfur atoms of a macrocycle, either 1,4,7,10-tetrathiacyclododecane ([12]aneS4) or 1,5,9,13-tetrathiacyclohexadecane ([16]aneS4), and the two others by relatively labile ligands (Cl⁻, , H₂O, dmso-S), are described:cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a), cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b), cis-[Ru([16]aneS4)Cl₂] (4), and trans-[Ru([16]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (5).The complexes of the larger [16]aneS4 macrocycle have a flexible coordination geometry, either cis or trans, that makes them unsuited for being used as precursors in metal-driven self-assembly processes.On the contrary, the [12]aneS4 complexes cis-[Ru([12]aneS4)(dmso-S)Cl]Cl (1) and, above all, its chlorido free derivatives cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a) and cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b) are potential precursors of the geometrically stable 90° bis-acceptor fragment cis-[Ru([12]aneS4)]²⁺.Preliminary results of their reactivity towards the linear linker pyrazine (pyz) showed that the nature of the isolated product depends on that of the counter-anion.When treated with pyz 2b afforded the dinuclear complex [{Ru([12]aneS4)(ONO₂)}₂(μ-pyz)](NO₃)₂ (8), while 2a gave the molecular triangle [{cis-Ru([12]aneS4)(μ-pyz)}₃](CF₃SO₃)₆ (9), both in low yields.The X-ray structures of compounds 2a, 2b, 4, 5, [{Ru([12]aneS4)Cl}₂(μ-pyz)]Cl₂ (7), 9, and of the sandwich complex[Ru([12]aneS3-S)₂](CF₃SO₃)₂ (3), in which only three sulfur atoms of each macrocycle are bound to ruthenium, are also described.     

Syntheses and molecular structures of Co-Na and Co-K coordination polymers constructed using mono- and bis-chelated cobalt(III) complexes of bis(2-pyridylcarbonyl)amide ion

Four new hetero-bimetallic Co³⁺-Na⁺ and Co³⁺-K⁺ coordination polymers having the molecular formulae [Na(H₂O)Co(L)(N₃)₃]_n (1), [Na₂Co(L)(N₃)₃(H₂O)₅][Co(L)(N₃)₃] (2), K[Co(L)(NCS)₃]·H₂O (3) and K[Co(L)₂][Co(NCS)₄]·0.5H₂O (4), were synthesized. Compounds 1-4 were characterized by single crystal X-ray diffraction, IR, UV-Vis, and thermogravimetric methods. These bimetallic systems have EE, EO azide bridge (1, 2) as well as bent (1, 2, 3) and linear (1, 4) aquo bridges. Important features observed among them were: a Z-shaped and diamond-shaped Co₂Na₂ clusters in 1, a centrosymmetric double ladder like polymer based on Na₄ cluster in 2, and a linear KOK core having paddle-wheel structure in 4.     

Hydrothermal syntheses, structures and properties of five rare earth coordination polymers with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

Hydrothermal reactions of rare earth ions(III) with a flexible building unit (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H₂tzda) lead to five novel coordination polymers with 1D chain and 3D network structures, namely, {[Y₂(tzda)₃(H₂O)₁₀] · 5H₂O}_n (1) and [Ln₂(tzda)₃(H₂O)₅]_n [Ln = Er (2), Pr (3), Nd (4), Eu (5)]. Compound 1 has one-dimensional ribbon-like chain structure constructed by [Y₂(tzda)₃] units through the syn-anti bidentate bridging mode of carboxylate groups. Compounds 2-5 possess compact three-dimensional network structures which are made up of [Ln₂(tzda)₃] (Ln = Er, Pr, Nd and Eu) units bridged by carboxylate groups. In these compounds, the flexible tzda²⁻ ligand is versatile and displays six different coordination fashions to meet the requirement of the coordination preference of the metal center. Furthermore, the magnetic behaviors for 2-5 in the temperature range of 5.0-300 K and photoluminescent property of 5 are significantly investigated in this paper.     

Differential effects of Co(III), Ni(II), and Ru(III) amine complexes on Sindbis virus

Transition metal complexes [Co(cyclen)(NH₃)₂](ClO₄)₃⋅H₂O (cyclen = 1,4,7,10-tetraazacyclododecane) (2), [Co(NH₃)₅(OH₂)](CF₃SO₃)₃ (3) [Ni(NH₃)₆]Br₂ (4) and [Ru(NH₃)₆]Cl₃ (5) were tested against Sindbis infected baby hamster kidney (BHK) cells and show differential effects from the previously reported anti-viral complex [Co(NH₃)₆]Cl₃ (1). The macrocyclic complex 2 and labile aqua complex 3 show either no or little effect on the survival on Sindbis virus-infected cells as compared to that for 1, which show a monotonic increase in % BHK cell survival. Nickel and ruthenium ammine complexes 4 and 5 had a moderate influence of cell survival. While the results showed some anti-viral activity for some of the structural variations, it appears that 1, with its potential to be a broad-spectrum anti-viral compound, occupies a unique position in its ability to both significantly enhance cell survival and to decrease viral expression of infected cells. We also show that 1 also shows anti-viral activity against Adenovirus lending support to the broad-spectrum potential of this complex.     

Secondary ligand-metal interactions in rhodium(III) and iridium(III) phosphoramidite complexes

The synthesis, characterization, and application in asymmetric catalytic cyclopropanation of Rh(III) and Ir(III) complexes containing (S_a,R_C,R_C)-O,O′-[1,1′-binaphthyl-2,2′-diyl]-N,N′-bis[1-phenyl-ethyl]phosphoramidite (1) are reported. The X-ray structures of the half-sandwich complexes [MCl₂(C₅Me₅)(1,κP)] (M = Rh, 2a; M = Ir, 2b) show that the metal-phosphoramidite bond is significantly shorter in the Ir(III) analog. Chloride abstraction from 2a (with CF₃SO₃SiMe₃ or with CF₃SO₃Me) and from 2b (with AgSbF₆) gives the cationic species [MCl(C₅Me₅)(1,2-η-1,κP)]⁺ (M = Rh, 3a; M = Ir, 3b), which display a secondary interaction between the metal and a dangling phenethyl group (NCH(CH₃)Ph) of the phosphoramidite ligand, as indicated by NMR spectroscopic studies. Complexes 3a and 3b slowly decompose in solution. In the case of 3b, the binuclear species [Ir₂Cl₃(C₅Me₅)₂]⁺ is slowly formed, as indicated by an X-ray study. Preliminary catalytic tests showed that 3a cyclopropanates styrene with moderate yield (35%) and diastereoselectivity (70:30 trans:cis ratio) and with 32% ee (for the trans isomer).     

Synthesis, crystal structure and properties of novel isostructural two-dimensional lanthanide-based coordination polymers with 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid

Five new isostructural two-dimensional lanthanide-based coordination polymers with the formula Ln₂(F₄BDC)₃(DEF)₂(EtOH)₂-2(DEF) (Ln = Tb, 1; Gd, 2; Eu, 3; La, 4; Nd, 5; F₄BDC²⁻ = 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate ligands; DEF = N,N′-diethylformamide), have been synthesized by reaction of Ln(NO₃)₃ and F₄BDC in a DEF/EtOH solvent mixture. The compounds were characterized by single-crystal and powder X-ray diffraction. In all cases, the metal ion is coordinated by nine oxygen atoms from two bidentate μ₂-F₄BDC²⁻ ligands, two bridging μ₂-F₄BDC²⁻ ligands, one μ₃-F₄BDC²⁻ ligand, one DEF molecule and one EtOH molecule forming a tri-capped trigonal prism. The Ln(1) metal ion is linked to an adjacent Ln(1) metal ion through the oxygen atoms of two bridging μ₂-F₄BDC²⁻ ligands and two μ₃-F₄BDC²⁻ bridging ligands to form a Ln₂O₁₈ dimer. The Ln₂O₁₈ polyhedra building units are linked to each other through four F₄BDC²⁻ ligands to form 2D sheets that are held together by hydrogen bonding to form a 3D framework. Compounds 1-5 were further characterized using thermogravimetric analysis and infrared spectroscopy. Studies of the photoluminescence properties of compounds 1 and 3, as well as the catalytic activity of compounds 3-5 in the Biginelli reaction, are presented.     

Synthesis and structural characterization of dinuclear complexes of trivalent aluminum, gallium, indium and chromium derived from pyrazole-2-ethanol

The reaction of 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL) with anhydrous metal(III) halides (M = Al, Ga, In and Cr) results in the isolation of four novel dinuclear complexes [Al(μ-L)Cl₂]₂ (1), [Ga(μ-L)Cl₂]₂ (2), [In(μ-L)Br₂(H₂O)]₂·2thf (3) and [Cr(μ-L)Cl₂(H₂O)]₂·1.5thf (4) in good yields. The new complexes have been characterized with the aid of analytical and spectroscopic studies. A single crystal X-ray structure determination in each case confirms the dimeric structure for all the complexes in the solid-state. The pyrazole ethanol ligand binds to the metal through both pyrazole nitrogen and bridging alkoxide oxygen terminals with the formation of a central M₂O₂ core involving the ethoxide anion. The metal(III) center is pentacoordinated in compounds 1 and 2, while it is hexacoordinated in compounds 3 and 4.     

Dinuclear organoiridium(III) mono- and bis-intercalators with rigid bridging ligands: Synthesis, cytotoxicity and DNA binding

The DNA binding and in vitro cytotoxicity of the dinuclear Ir(III) polypyridyl complexes [{(η⁵-C₅Me₅)Ir(dppz)}₂(μ-pyz)](CF₃SO₃)₄1 and [{(η⁵-C₅Me₅)Ir(pp)}₂(μ-4,4′-bpy)](CF₃SO₃)₄2-4 (pp = dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), dipyrido[2,3-a:2′,3′-c]phenazine (dppz), benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (dppn)) with the rigid bridging ligands pyrazine (pyz) or 4,4′-bipyridine (4,4′-bpy) have been studied. Stable intercalative binding into CT DNA (calf thymus DNA) is indicated for the dppz complexes 1 and 3 by induced negative CD bands at about 300 nm and large viscosity increases, with the individual measurements being in accordance with intrastrand bis-intercalation for 3 and mono-intercalation for 1. The observed interruption of specific interresidue NOE cross peaks from the relevant nucleobase H6/H8 protons to the sugar H2′/H2″ protons of the preceding nucleotide is in accordance with bis-intercalation of complex 3 between the C3G18 and G4C17 base pairs and the T5A16 and A6T15 base pairs of the decanucleotide d(5′-CGCGTAGGCC-3′). Complexes 1 and 3 exhibit a greatly improved uptake by HT-29 (colon carcinoma) cells and significantly improved in vitro IC₅₀ values of 1.8 ± 0.1 and 3.8 ± 0.1 μM towards this cell line in comparison to the mononuclear complex [(η⁵-C₅Me₅)IrCl(dppz)](CF₃SO₃) (IC₅₀ = 7.4 ± 0.9 μM).