Yttrium Complexes Research Articles

Yttrium and lanthanide complexes of β-dialdehydes: synthesis, characterization, luminescence and electrochemistry of coordination compounds with the conjugate base of bromomalonaldehyde.

Novel yttrium, europium and terbium coordination compounds having formulae [AsPh4][Ln(BrMA)4] (6LN), Ln(BrMA)3(bipyO2) (7Ln), Ln(NMA)3(phen) (8Ln) and Ln(NMA)3(terpy) (9Ln) (Ln = Y, Eu, Tb; BrMA = conjugate base of bromomalonaldehyde; bipyO2 = 2,2'-bipyridine-N,N'-dioxide; phen = 1,10-phenantroline; terpy = 2,2':6',2''-terpyridine) were synthesized and characterized by using spectroscopic and electrochemical techniques. Uncharged europium and, to a lesser extent, terbium complexes showed appreciable luminescence in the solid state upon excitation with UV light. Polymeric materials and ionic liquids containing BrMA and lanthanides were prepared and photoluminescence measurements were carried out. From an electrochemical point of view, europium(III) BrMA-complexes showed a quasi-reversible one-electron reduction process. The one electron transfer reaction Eu(III) to Eu(II) allowed the photoluminescence tuning of 8Eu deposited on the surface of a glassy carbon electrode.

Synthesis and structural characterization of amido scorpionate rare earth metals complexes

The reactivity of hybrid scorpionate/cyclopentadienyl ligands in the form of the protio derivatives as a mixture of two regioisomers, namely bpzcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene] and bpztcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene], with the tris(silylamide) precursors [M{N(SiHMe2)2}3(thf)x] of rare earth metals (including the group 3 metals scandium and yttrium) is related to the atomic radii of the metal centres. The reaction with the precursor containing the smallest ion, [Sc{N(SiHMe2)2}3(thf)], did not proceed even heating at reflux temperature in toluene. The reaction with the precursors that contain a medium-sized metal ion, i.e., [M{N(SiHMe2)2}3(thf)2] (M = Y, Lu), proceeded only at high temperature and gave good yields of the silylenediamide-containing derivatives [M{κ(2)-NN-Me2Si(NSiHMe2)2}(bpzcp)] (M = Y , Lu ) and [M{κ(2)-NN-Me2Si(NSiHMe2)2}(bpztcp)] (M = Y , Lu ) by an double activation of Si-H and Si-N bonds. However, the reaction with the precursors that contained the largest metal ions, i.e., [M{N(SiHMe2)2}3(thf)2] (M = Nd, Sm), proceeded rapidly at room temperature to afford the bis(silylamide) complexes [M{N(SiHMe2)2}2(bpzcp)] (M = Nd , Sm ) and [M{N(SiHMe2)2}2(bpztcp)] (M = Nd , Sm ). Additionally, the alkyl heteroscorpionate yttrium and lutetium complexes [M(CH2SiMe3)2(NNCp)] (M = Y, Lu) reacted with an excess of HN(SiHMe2)2 to give the mixed alkyl/amide derivatives [M{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (M = Y , Lu ) and [M{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (M = Y , Lu ). The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures of , and were also established.

Yttrium and lanthanide complexes of β-dialdehydes: synthesis, characterization and luminescence of coordination compounds with the conjugate base of nitromalonaldehyde.

Coordination compounds having formulae [AsPh4][Ln(NMA)4] (1(Ln)), Ln(NMA)3(tppo)2 (2(Ln)), Ln(NMA)3(bipyO2) (3(Ln)), Ln(NMA)3(phen) (4(Ln)) and Ln(NMA)3(terpy) (5(Ln)) (Ln = Y and some lanthanides; NMA = conjugate base of nitromalonaldehyde; tppo = triphenylphosphine oxide; bipyO2 = 2,2'-bipyridine-N,N'-dioxide; phen = 1,10-phenanthroline; terpy = 2,2':6',2''-terpyridine) were synthesized and characterized and X-ray diffraction data were collected for [AsPh4][Y(NMA)4] (1(Y)). The neutral europium derivatives showed appreciable luminescence in the solid state upon excitation with UV light and photoluminescence measurements were carried out. These compounds were used as dopants for the preparation of luminescent poly(methyl methacrylate). Luminescent polyvinylpyrrolidone samples were obtained by reacting the pure polymer with water solutions containing NMA and trivalent europium ions.

Solvent-Free Organometallic Reactivity: Synthesis of Hydride and Carboxylate Complexes of Uranium and Yttrium from Gas/Solid Reactions

Gas/solid reactions involving H2 and CO2 with the metallocenes (C5Me5)2UMe2 and (C5Me5)2U(allyl)2 as solids in the absence of solvent provide an improved method to make organouranium hydride and carboxylate products. Decomposition products that can form in solution from the reactive hydrides can be avoided by this method, and this approach can also provide intermediates too reactive to isolate in some solution reactions. In contrast to the variable nature of the hydrogenolysis reaction of (C5Me5)2UMe2 in toluene that forms byproducts along with the mixture of [(C5Me5)2UH2]2 and [(C5Me5)2UH]2, a byproduct-free hydrogenolysis occurs when (C5Me5)2UMe2 in the solid state is treated with H2 gas to form predominantly [(C5Me5)2UH2]2. H2 reacts with solid (C5Me5)2U(C3H5)2 and (C5Me5)2U(C3H5) similarly. The reaction of CO2 (80 psi) with solid (C5Me5)2UMe2 forms the monocarboxylate (C5Me5)2U(O2CCH3-κ2O,O′)Me, in contrast to the solution reaction that forms the diacetate (C5Me5)2U(O2CCH3-κ2O,O′)2 in minutes. The reaction of H2 with solid (C5Me5)2Y(C3H5) provided (C5Me5)2Y(μ-H)YH(C5Me5)2 without the decomposition products that it forms in solution such that single crystals suitable for X-ray diffraction could be isolated for the first time.

Yttrium– and Aluminum–Bis(phenolate)pyridine Complexes: Catalysts and Model Compounds of the Intermediates for the Stereoselective Ring-Opening Polymerization of Racemic Lactide and β-Butyrolactone

Yttrium and aluminum complexes of an original pyridine-bis(phenolate) ligand have been prepared. Reactions of {ONOMe,Cumyl}Y[N(SiHMe2)2](THF)(Et2O) (1) with 1 equiv of methyl (R)-3-hydroxybutyrate and methyl (S,S)-lactyllactate afforded respectively {ONOMe,Cumyl}Y((R)-OCH(CH3)CH2COOMe) (2) and {ONOMe,Cumyl}Y((S,S)-OCH(CH3)CO2CH(CH3)CO2Me) (3), which are rare models of the active species in the ring-opening polymerization (ROP) of β-butyrolactone (BBL) and lactide (LA), respectively. 13C NMR data for 2 and 3 indicate that, in solution, the carbonyl groups coordinate onto the yttrium centers, forming mononuclear species with six- and five-membered cycles, respectively. The aluminum compounds {ONOMe,Cumyl}Al(iPr (S)-lactate) (5), {ONOMe,Cumyl}Al((R)-OCH(CH3)CH2COOCH3) (6), and {ONOMe,Cumyl}Al((rac)-OCH(CF3)CH2CO2C2H5) (7) were prepared analogously from the parent methyl complex {ONOMe,Cumyl}AlMe (4). NMR data and the solid-state structure of 6 confirm the coordination of the carbonyl group. Yttrium compounds 1 and 2 are active initiators for the ROP of racemic LA and BBL. Their performances (activity, control of the molecular weights, tacticity) are much affected by the nature of the solvent or by the addition of just a few equivalents of pyridine. Optimal conditions are quite contrasted for the ROP of rac-LA and rac-BBL, highlighting fundamental differences between these two monomers. In the best cases, highly heterotactic PLAs (Pr up to 0.96) and syndiotactic-enriched PHB (Pr up to 0.86), with good control over the molecular weights, were obtained.

ChemInform Abstract: Y, Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis, Characterization, and Catalysis in the cis‐1,4‐Selective Polymerization of Isoprene.

A series of NCO/NCS pincer precursors, 3-(Ar(2)OCH2)-2-Br-(Ar(1)N=CH)C6H3 (((Ar1)NCO(Ar2))Br, 3a-d) and 3-(2,6-Me2C6H3SCH2)-2-Br-(Ar(1)N=CH)C6H3 (((Ar1)NCS(Me))Br, 4a and 4b) were synthesized and characterized. The reactions of [(Ar1)NCO(Ar2)]Br/[(Ar1)NCS(Me)]Br with nBuLi and the subsequent addition of the rare-earth-metal chlorides afforded their corresponding rare-earth-metal-pincer complexes, that is, [((Ar1)NCO(Ar2))YCl2(thf)2] (5a-d), [((Ar1)NCO(Ar2))LuCl2(thf)2] (6a, 6d), [((Ar1)NCO(Ar2))GdCl2(thf)2] (7), [{((Ar1)NCS(Me))Y(μ-Cl)}2{(μ-Cl)Li(thf)2(μ-Cl)}2] (8, 9), and [{((Ar1)NCS(Me))Gd(μ-Cl)}2{(μ-Cl)Li(thf)2(μ-Cl)}2] (10, 11). These diamagnetic complexes were characterized by (1)H and (13)C NMR spectroscopy and the molecular structures of compounds 5a, 6a, 7, and 10 were well-established by X-ray diffraction analysis. In compounds 5a, 6a, and 7, all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two Cl-Li-Cl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis-1,4-selective polyisoprene, whilst the NCO-lutetium complexes were inert under the same conditions.

Reactivity of Scorpionate-Anchored Yttrium Alkyl Primary Amido Complexes toward Carbodiimides. Insertion Selectivity of Y–NHAr and Y–CH2Ph Bonds

The TpMe2-supported yttrium dialkyl TpMe2Y(CH2Ph)2(THF) (TpMe2 = tri(3,5-dimethylpyrazolyl)borate) reacted with 1 equiv of ArNH2 in THF at room temperature to afford the yttrium alkyl primary amido complexes TpMe2YNHAr(CH2Ph)(THF) (Ar = Ph (1), C6H3-iPr2-2,6 (2)) in 84% and 88% isolated yields, respectively. Complex 1 reacted with iPrN═C═NiPr in THF at room temperature to give a yttrium dianionic guanidinate complex, TpMe2Y[(iPrN)2C═NPh](THF)2 (3, 74%). However, the reaction of 1 with ArN═C═NAr (Ar = C6H3-iPr2-2,6) in the same conditions produced a Y–C bond insertion product, TpMe2Y[(ArN)2CCH2Ph](NHPh) (4, 87%). Moreover, treatment of 2 with 1 equiv of iPrN═C═NiPr in THF at room temperature afforded two yttrium complex, TpMe2Y[(iPrN)C═NAr](THF) (5) and TpMe2Y[(iPrN)2CCH2Ph](NHAr) (6), in 58% and 19% isolated yields, respectively. These results indicated that carbodiimide can selectively insert into the Y–CH2Ph and Y–NHAr σ-bonds of TpMe2-supported yttrium alkyl primary amido complexes TpMe2YNHAr(CH2Ph)(THF), and this selectivity depends on the steric hindrance of the substituent groups R of cabodiimides and the primary amido ligands. All these new complexes were characterized by elemental analysis and spectroscopic methods, and their solid-state structures except 1 were also confirmed by single-crystal X-ray diffraction analysis.

Enhanced Luminescence of Terbium Complexes with 2,3-Pyrazinedicarboxylate by Y(III) Doping

Ten kinds of terbium doped inert yttrium complexes with 2,3-pyrazinedicarboxylate (2,3-pzdc2-) have been synthesized. Characterization results indicate that the complexes have the compositions of Tb (pzdc)1.55H2O and TbxYy(pzdc)1.55H2O (x:y=0.10:0.90; 0.20:0.80; 0.30:0.70; 0.40:0.60; 0.60:0.40; 0.70:0.30; 0.80:0.20; 0.90:0.10). IR spectra show that the lanthanide ions coordinate with the carboxylic oxygen atoms and nitrogen atoms of the ligands. Luminescence spectra show that the Y(III) ions can remarkably increase the luminescent intensities of terbium complexes. And Tb0.7Y0.3(pzdc)1.55H2O exhibits the strongest luminescent emission. Furthermore, the doped lanthanide complexes show longer luminescence lifetimes and higher quantum yields. The enhanced luminescence efficiencies of Tb3+ ions in the doped complexes may result from intramolecular energy transfer as well as the decrease of the self-quench of the Tb3+ ions induced by the doped Y(III) ions.

Yttrium complexation with benzoic acid and tris(hydroxymethyl)aminomethane

Yttrium complexation in extraction systems with benzoic acid (BA) and tris(hydroxymethyl)aminomethane (THMAM) was studied. The growth of yttrium distribution ratios in this system is caused by the formation of different-ligand coordination compounds of yttrium with BA and THMAM. Quantum chemical calculations for the formation energy of different-ligand complex showed that the most stable complex forms when yttrium atom coordinates to two THMAM molecules via oxygen and nitrogen atoms and to one THMAM molecule via nitrogen atom. The complex is stable in both bidentate and monodentate coordination of the carboxyl groups of benzoic acid to yttrium atom. Obtained yttrium extracts were used for the synthesis of complex-oxide nanosized cathodophosphors by extraction-pyrolytic technique.

Bis(alkyl) yttrium complex containing a new tridentate amidinate ligand: synthesis and structure

New potentially tridentate amidine containing the quinoline fragment in the lateral chain, viz., NC9H6-8-NHC(But)N-2,6-Pri2-C6H3 (1), was synthesized by the reaction of chloroimine 2,6-Pri2-C6H3-N=C(But)Cl and lithium derivative of 8-aminoquinoline NC9H6-8-NHLi. The elimination of alkane under the action of amidine 1 on Y(CH2SiMe3)2(THF)2 in THF affords bis(alkyl) yttrium complex [NC9H6-8-NC(But)N-2,6-Pri2-C6H3]Y(CH2SiMe3)2(THF) (2), monomeric in the crystalline state.

Y, Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis, Characterization, and Catalysis in the cis‐1,4‐Selective Polymerization of Isoprene

A series of NCO/NCS pincer precursors, 3-(Ar(2)OCH2)-2-Br-(Ar(1)N=CH)C6H3 (((Ar1)NCO(Ar2))Br, 3a-d) and 3-(2,6-Me2C6H3SCH2)-2-Br-(Ar(1)N=CH)C6H3 (((Ar1)NCS(Me))Br, 4a and 4b) were synthesized and characterized. The reactions of [(Ar1)NCO(Ar2)]Br/[(Ar1)NCS(Me)]Br with nBuLi and the subsequent addition of the rare-earth-metal chlorides afforded their corresponding rare-earth-metal-pincer complexes, that is, [((Ar1)NCO(Ar2))YCl2(thf)2] (5a-d), [((Ar1)NCO(Ar2))LuCl2(thf)2] (6a, 6d), [((Ar1)NCO(Ar2))GdCl2(thf)2] (7), [{((Ar1)NCS(Me))Y(μ-Cl)}2{(μ-Cl)Li(thf)2(μ-Cl)}2] (8, 9), and [{((Ar1)NCS(Me))Gd(μ-Cl)}2{(μ-Cl)Li(thf)2(μ-Cl)}2] (10, 11). These diamagnetic complexes were characterized by (1)H and (13)C NMR spectroscopy and the molecular structures of compounds 5a, 6a, 7, and 10 were well-established by X-ray diffraction analysis. In compounds 5a, 6a, and 7, all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two Cl-Li-Cl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis-1,4-selective polyisoprene, whilst the NCO-lutetium complexes were inert under the same conditions.

Benzonitrile Insertion into Silylarylamides – ansa‐Bis(benzamidinate) Ligand Systems with Rigid o‐ and m‐Phenylene Linkers in the Synthesis of Lithium and Rare Earth Complexes

AbstractThe reactions of the lithium silylarylamides [1,2‐C6H4(NSiMe3)2Li2]2 and [1,3‐C6H4(NSiMe3)2Li2] with two equivalents of PhCN [tetrahydrofuran (thf), room temp.] is an efficient synthetic approach to the ansa‐bis(amidinate) ligand systems [1,2‐C6H4{NC(Ph)NSiMe3}2Li2(thf)]2 and [1,3‐C6H4{NC(Ph)NSiMe3}2Li2(thf)2]2, which were isolated in 54 and 60 % yields, respectively. However, lithium silylarylamide [2,6‐C5H3N(NSiMe3)2Li2] containing a pyridine fragment does not undergo PhCN insertion even at elevated temperatures (thf, toluene), and the reaction affords the silylarylamido complex [2,6‐C5H3N{NSiMe3}2Li2]3·(C6H5CN)4, which contains a coordinated benzonitrile molecule. The different reactivity of the compounds correlates with the changes in the molecular orbital energies estimated by DFT calculations. The salt metathesis reaction of anhydrous YCl3 with lithium amidinate [1,2‐C6H4{NC(Ph)NSiMe3}2Li2(thf)]2 in 2:1 molar ratio (thf, 20 °C) afforded a neutral bis(amidinate) chloro yttrium complex [1,2‐C6H4{NC(Ph)NSiMe3}2]YCl(thf)2 in 80 % yield. With NdCl3, the analogous reaction resulted in a trinuclear neodymium chloro ate complex with a rather unusual μ‐bridging lateral coordination of the amidinate fragment [1,2‐C6H4{NC(Ph)NSiMe3}2Nd(thf)(μ‐Cl)(1,2‐C6H4{NC(Ph)NSiMe3}2Nd{μ‐Cl}2)][Li(thf)2].

Yttrium half-sandwich complexes bearing the 2-(N,N-dimethylamino)ethyl-tetramethylcyclopentadienyl ligand

The synthesis of bis(dimethylsilyl)amide and dimethyl half-sandwich complexes of yttrium bearing the 2-(N,N-dimethylamino)ethyl-tetramethylcyclopentadienyl ligand revealed unusual Si‒H activation reactions and ate complex formation, respectively. Protonolysis of complex Y[N(SiHMe2)2]3(thf)2 with cyclopentadiene C5Me4HCH2CH2NMe2 (HCpNMe2) at elevated temperature yielded complex CpNMe2Y[η2-SiMe2(NSiHMe2)2](thf) featuring a four-membered metallacycle. The bis(amido) ligand [η2-SiMe2(NSiHMe2)2]2− is shown to form via separation of H2SiMe2. In contrast, the salt metathesis reaction of YCl3(thf)3 with LiN(SiHMe2)2 and LiCpNMe2 in a 1/2/1 ratio at ambient temperature generated the non-activated complex CpNMe2Y[N(SiHMe2)2]2, exhibiting a distinct ligand activation at elevated temperatures, as evidenced by a comprehensive NMR spectroscopic study. Application of a sequential salt metathesis protocol involving YCl3(thf)3, LiCpNMe2, and LiMe led to the isolation of ate complexes [CpNMe2YCl2]2[LiCl(thf)2] and [CpNMe2YMe2(LiMe)]2. Aforementioned half-sandwich complexes were all characterized by X-ray structure analyses and the respective silylamido and methyl derivatives are demonstrated to produce the half-sandwich yttrium bis(tetramethylaluminate) complex [CpNMe2AlMe3Y(AlMe4)2] in the presence of excess trimethylaluminium, by NMR spectroscopic studies.

Yttrium Complexes Featuring Different Y–C Bonds. Comparative Reactivity Studies: Toward Terminal Imido Complexes

The reactions of 2,6-diisopropylaniline with equimolar amounts of alkyl–heteroaryl yttrium complexes containing Y–C(sp3, alkyl) along with Y–C(sp2, heteroaryl) bonds resulting from intramolecular C–H bond activation of the amido–pyridinate ligands [NNOBzFur]YCH2SiMe3(THF)2, [NNSBzTh]YCH2SiMe3(THF)2, and [NNSEtTh]YCH2SiMe3(THF)2 have been scrutinized with the aim of synthesizing yttrium terminal imido species. These reactions occur at ambient temperature with the protonolysis of the Y–C(sp3, alkyl) bond, thus affording anilido–heteroaryl species and maintaining the residual Y–C(sp2, heteroaryl) bond untouched. However, the subsequent transformation of the as-synthesized anilido–heteroaryl complexes depends on the nature of the substituent on the 6-position of the pyridyl ring. In the case of the benzofuryl yttrium derivative [NNOBzFur]YNH-2,6-iPr2C6H3(THF)2 (4), heating to 50 °C results in benzofuran ring opening with the formation of an anilido species supported by a dianionic amido–yne–phenolate ligand f...

Influence of the utilized precursors on the morphology and properties of YBa2Cu3O7−y superconducting nanostructures

In order to prevent agglomeration of high temperature ceramic material, the solid state processing based on new and appropriate yttrium complex precursors without applying surfactant has been suggested. These have been prepared by a reaction of yttrium acetate with three coordination compositions, acetylacetone, 2-hydroxo-1-naphthaldehyde and salicylaldehyde, for forming yttrium complex types. It was found that the size and morphology of products are clearly dependent on the type of utilized precursor because the organic ligands around yttrium center in these novel precursors act like a protecting agent. Magnetic susceptibility measurements showed that Tc of the superconducting nanoparticles is from 82K to 88.4K. The crystalline structures of the nanoparticles remained in orthorhombic symmetry. Characterizations of specimens were performed using scanning electron microscopy and transmission electron microscopy, supported by other techniques including XRD diffraction, energy dispersive X-ray, FT-IR spectrum and magnetic susceptibility measurements.

Brightly luminescent markers based on nanoparticles composed of complexes of metal ions with coumarin-30

This paper discusses the sensitized fluorescence of coumarin-30 in nanoparticles self-organized from complexes of phenylbenzoyltrifluoroacetone and 1, 10-phenanthroline with ions of the lanthanides, yttrium, aluminum, and scandium in water–alcohol solutions. It is shown that, when nanoparticles are formed from complexes of lanthanide and yttrium ions, the coumarin-30 molecules from the solution are completely incorporated into the nanoparticles. An absence of concentration quenching of the cofluorescence of coumarin-30 in the nanoparticles is detected in the entire region of dye concentrations studied here. Facts are presented that prove that coumarin-30 is incorporated in the lanthanide and yttrium complexes as a synergic bidentate ligand. It is demonstrated that brightly luminescent markers can be created that absorb not only in the 360–370 nm region, but also in the 440–450 nm region and that possess a narrow fluorescence spectrum with a maximum at λ=520 nm.

29Si–1H IMPACT HMBC: a suitable tool for analyzing silylated derivatives

A modified version of the IMPACT heteronuclear multiple bond correlation (HMBC) has allowed the characterization of an organosilane and a tetrasilylated yttrium complex. With the help of this sequence, an average gain in sensitivity close to 2 has been obtained compared with the standard HMBC experiment for disilanes as well as for yttrium complexes containing silylated ligands. This modified version of this long-range correlation experiment opens the way for following kinetics in the range of a fraction of a minute and to study by NMR low concentrated samples and low abundant nuclei.

Rare-Earth Half-Sandwich Dialkyl and Homoleptic Trialkyl Complexes for Rapid and Stereoselective Polymerization of a Conjugated Polar Olefin

Under ambient conditions, discrete half-sandwich rare-earth (RE) dialkyls, [η5-(1,3-(SiMe3)2C9H5)]]RE(CH2SiMe3)2(THF) (RE = Sc, Y, Dy, Lu), catalyze rapid and stereoselective coordination polymerization of β-methyl-α-methylene-γ-butyrolactone (βMMBL), a conjugated polar olefin and a member of the naturally occurring or biomass-derived methylene butyrolactone family. Within the present RE series, the complex of the largest ion (Dy3+) exhibits the highest activity, achieving a high turnover frequency of 390 min–1, and also produces the highly isotactic polymer PβMMBL (mm = 91.0%). This stereoregular polymer is thermally robust, with a high glass-transition temperature of 280 °C, and is resistant to all common organic solvents. Other half-sandwich RE catalysts of the series are also highly active and produce polymers with a similarly high isotacticity. Intriguingly, even simple homoleptic hydrocarbyl RE complexes, RE(CH2SiMe3)3(THF)2 (RE = Sc, Y, Dy, Lu), also afford highly isotactic polymer PβMMBL, despite their much lower polymerization activity, except for the Lu complex, which maintains its high activity for both types of complexes. Computational studies of both half-sandwich and simple hydrocarbyl yttrium complexes have revealed a stereocontrol mechanism that well explains the observed high stereoselectivity of βMMBL polymerization by both types of catalysts. Specifically, the experimental stereoselectivity can be well rationalized with a monometallic propagation mechanism through predominantly chain-end stereocontrol in the coordination–addition polymerization. In this mechanism, formation of an isotactic polymer chiefly originates from interactions between the methyl groups on the chiral β-C atom of the five-membered ring of both the coordinated monomer and the last inserted βMMBL unit of the chain, and the auxiliary ligand on the metal makes a negligible contribution to the stereocontrol of the polymerization.

Biochemical investigation of yttrium(III) complex containing 1,10-phenanthroline: DNA binding and antibacterial activity

Characterization of the interaction between yttrium(III) complex containing 1,10-phenanthroline as ligand, [Y(phen)2Cl(OH2)3]Cl2⋅H2O, and DNA has been carried out by UV absorption, fluorescence spectra and viscosity measurements in order to investigate binding mode. The experimental results indicate that the yttrium(III) complex binds to DNA and absorption is decreasing in charge transfer band with the increase in amount of DNA. The binding constant (Kb) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), were calculated according to relevant fluorescent data and Vant’ Hoff equation. The results of interaction mechanism studies, suggested that groove binding plays a major role in the binding of the complex and DNA. The activity of yttrium(III) complex against some bacteria was tested and antimicrobial screening tests shown growth inhibitory activity in the presence of yttrium(III) complex.

8-Quinolinolate complexes of yttrium and ytterbium: molecular arrangement and fragmentation under laser impact

New 8-quinolinolate (Q) complexes of yttrium (1) and ytterbium (2) were synthesized by the reactions of Cp3Y and Yb[N(SiMe3)2]3 with 3 equiv. of 8-hydroxyquinoline in a DME solution. Single crystal X-ray analysis revealed the trinuclear molecular structure of the compounds Ln3Q9. The LDI-TOFMS investigation displayed that under the laser impact the compounds split off Q(-) anions to give Ln3Q8(+), Ln2Q5(+) and LnQ3(+) moieties. In the negative mode spectra the anions Q(-) and LnQ4(-) were observed. The DFT calculations showed the decreased stability of cationic Ln-quinolinolate as compared with their anionic counterparts. Complex 2 which is used as an emitter in a three-layer OLED displayed a metal-centered emission at 979 nm and an intensity of 50 μW cm(-2) at 15.5 V.