Tridentate Nitrogen Ligand as a Tool for the Construction of Well-Defined Rare Earth Trichloride Complexes

LnCl3(THF)3 (Ln = Y, La ÷ Nd, Sm ÷ Lu) readily react with the tridentate 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3tach) ligand to form mono- or binuclear lanthanide trichloride complexes, depending on the stoichiometry of the reaction and the ionic radius of the metal: mononuclear pseudosandwich [LnCl3(Me3tach)2], (Ln = Y, La ÷ Ho) or binuclear complexes [Ln2Cl6(Me3tach)3], or [LnCl3(Me3tach)(THF)]2 (Ln = Sm, Tb). Detailed analysis of the NMR data of [LnCl3(Me3tach)2] complexes with paramagnetic lanthanide ions showed that their structures remained unchanged in the toluene solution. A series of isomorphous complexes [LnCl3(Me3tach)(Py)2] (Ln = La, Sm, Tb, Er, Lu; Py = pyridine) have been obtained by the recrystallization of either mononuclear or binuclear complexes from pyridine. Complexes of terbium and europium ions with the Me3tach ligand exhibit relatively high quantum yields of metal-centered luminescence (0.39 and 0.32, respectively).

Bis(η5-cyclo-penta-dien-yl)(2-{[(2-meth-oxy-phen-yl)imino]-meth-yl}phenolato-κ3 O,N,O')terbium

The air- and moisture-sensitive title compound, [Tb(C5H5)2(C14H12NO2)], was synthesized from tris-(cyclo-penta-dien-yl)(tetra-hydro-furan)-terbium and 2-{[(2-meth-oxy-phen-yl)imino]-meth-yl}phenol. Each Tb atom is coordinated by two cyclo-penta-dienyl ligands in an η5-coordination mode and by one N and two O atoms of the organic ligand in a tridentate κ3 O,N,O'-mode.

Diarylphosphate as a New Route for Design of Highly Luminescent Ln Complexes

Organophosphate-chloride complexes [{(2,6-ⁱPr₂C₆H₃-O)₂POO}₂LnCl(CH₃OH)₄]·2CH₃OH, Ln = Nd (1), Eu (2), Gd (3), and Tb (4) have been obtained and structurally characterized. Their reaction with 2,2':6',2″-terpyridine leads to the formation of 1:1 adducts ([{(2,6-ⁱPr₂C₆H₃-O)₂POO}₂LnCl(terpy)(H₂O)₂(CH₃OH)], Ln = Eu (5), Gd (6), Tb (7) with exception of Nd, where tris-diisopropylphenylphosphate complex [{(2,6-ⁱPr₂C₆H₃-O)₂POO}₃Nd) (terpy)(H₂O)(CH₃OH)] (8) was obtained due to the ligand metathesis. A bright luminescence observed for the Eu and Tb organophosphate complexes is the first example of an application of organophosphate ligands for 4f-ions luminescence sensitization. Photophysical properties of all complexes were analyzed by optical spectroscopy and an energy transfer scheme was discussed. A combination of two types of ligands into the coordination sphere (phosphate and phenanthroline) allows designing the Eu surrounding with very high intrinsic quantum yield QEuEu (0.92) and highly luminescent Ln complexes for both visible and near-infrared (NIR) regions.

Crystal structure of tris-[bis-(2,6-diiso-propyl-phen-yl) phosphato-κO]penta-kis-(methanol-κO)europium methanol monosolvate

The mononuclear title complex, [Eu(C24H34O4P)3(CH4O)5]·CH4O, (1), has been obtained as a minor product in the reaction between EuCl3(H2O)6 and lithium bis-(2,6-diiso-propyl-phen-yl) phosphate in a 1:3 molar ratio in a methanol medium. Its structure exhibits monoclinic (P21/c) symmetry at 120 K and is isostructural with the La, Ce and Nd analogs reported previously [Minyaev et al. (2018a ▸). Acta Cryst. C74, 590-598]. In (1), all three bis-(2,6-diiso-propyl-phen-yl) phosphate ligands display the terminal κ1 O-coordination mode. All of the hy-droxy H atoms are involved in O-H⋯O hydrogen bonding, exhibiting four intra-molecular and two inter-molecular hydrogen bonds. Photophysical studies have demonstrated luminescence of (1) with a low quantum yield.

(1R,2S,4r)-1,2,4-Tri-phenyl-cyclo-pentane-1,2-diol and (1R,2S,4r)-4-(2-meth-oxy-phen-yl)-1,2-di-phenyl-cyclo-pentane-1,2-diol: application as initiators for ring-opening polymerization of ∊-caprolactone

Reductive cyclization of 1,3,5-triphenyl- and 3-(2-meth-oxy-phen-yl)-1,5-di-phenyl-pentane-1,5-diones by zinc in acetic acid medium leads to the formation of 1,2,4-tri-phenyl-cyclo-pentane-1,2-diol [1,2,4-Ph3C5H5-1,2-(OH)2, C23H22O2, (I)] and 4-(2-meth-oxy-phen-yl)-1,2-di-phenyl-cyclo-pentane-1,2-diol [4-(2-MeOC6H4)-1,2-Ph2C5H5-1,2-(OH)2, C24H24O3, (II)]. Their single crystals have been obtained by crystallization from a THF/hexane solvent mixture. Diols (I) and (II) crystallize in ortho-rhom-bic (Pbca) and triclinic (P ) space groups, respectively, at 150 K. Their asymmetric units comprise one [in the case of (I)] and three [in the case of (II)] crystallographically independent mol-ecules of the achiral (1R,2S,4r)-diol isomer. Each hydroxyl group is involved in one intra-molecular and one inter-molecular O-H⋯O hydrogen bond, forming one-dimensional chains. Compounds (I) and (II) have been used successfully as precatalyst activators for the ring-opening polymerization of ∊-caprolactone.

Bis[μ-bis-(2,6-diiso-propyl-phen-yl) phosphato-κ2 O:O']bis-[(2,2'-bi-pyridine-κ2 N,N')lithium] toluene disolvate and its catalytic activity in ring-opening polymerization of ∊-caprolactone and l-dilactide

The solvated centrosymmmtric title compound, [Li2(C24H34O4P)2(C10H8N2)2]·2C7H8, was formed in the reaction between {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) and 2,2'-bi-pyridine (bipy) in toluene. The structure has monoclinic (P21/n) symmetry at 120 K and the asymmetric unit consists of half a complex mol-ecule and one mol-ecule of toluene solvent. The diaryl phosphate ligand demonstrates a μ-κO:κO'-bridging coordination mode and the 2,2'-bi-pyridine ligand is chelating to the Li+ cation, generating a distorted tetra-hedral LiN2O2 coordination polyhedron. The complex exhibits a unique dimeric Li2O4P2 core. One isopropyl group is disordered over two orientations in a 0.621 (4):0.379 (4) ratio. In the crystal, weak C-H⋯O and C-H⋯π inter-actions help to consolidate the packing. Catalytic systems based on the title complex and on the closely related complex {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) display activity in the ring-opening polymerization of ∊-caprolactone and l-dilactide.

Crystal structure of bis-(μ2-meth-anolato-κO:κO)hexa-methyl-bis-(μ2-tri-phenyl-acetato-κO:κO')bis-(μ2-tri-phenyl-acetato-κ2 O,O':κO)dialuminiumdi-lanthanum toluene tetra-solvate

The title compound, [Al2La2(C20H15O2)4(CH3)6(CH3O)2]·4CH3C6H5 or [{La(Ph3CCOO)2(Me3AlOMe)}2]·4CH3C6H5, was formed in a reaction between lanthanum tris-(tetra-methyl-aluminate) and tri-phenyl-acetic acid (1:1) with unintended partial oxidation. The tri-phenyl-acetate ligand exhibits μ2-κ1 O:κ1 O' bridging and μ2-κ2 O,O':κ1 O semi-bridging coordination modes, forming a dimeric La2(μ-OCO)4 core. The semi-bridging tri-phenyl-acetate group provides additional bonding with an La3+ cation via the π-system of one of its phenyl rings. The tri-methyl-meth-oxy-aluminate anion, which is coordinated to the La3+ cation by its O atom, displays a rather long La-CMe bond. Two toluene mol-ecules are each disordered over two orientations about centres of symmetry with site occupancy factors of 0.5. The title compound represents the first example of an LnIII complex containing both alkyl alkoxide aluminate and π-bounded arene fragments.

Different coordination modes of trans-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in rare-earth complexes: influence of the metal cation radius and the number of ligands on steric congestion and ligand coordination modes

A simple and effective synthetic route to homo- and heteroleptic rare-earth (Ln = Y, La and Nd) complexes with a tridentate Schiff base anion has been demonstrated using exchange reactions of rare-earth chlorides with in-situ-generated sodium (E)-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in different molar ratios in absolute methanol. Five crystal structures have been determined and studied, namely tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ³O¹,N,O²)lanthanum, [La(C₁₄H₁₂NO₂)₃], (1), tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ³O¹,N,O²)neodymium tetrahydrofuran disolvate, [La(C₁₄H₁₂NO₂)₃]·2C₄H₈O, (2)·2THF, tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-κ³O¹,N,O²;κ³O¹,N,O²;κ²N,O¹-yttrium, [Y(C₁₄H₁₂NO₂)₃], (3), dichlorido-1κCl,2κCl-μ-methanolato-1:2κ²O:O-methanol-2κO-(μ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ³O¹,N,O²:2κO¹)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-1κ³O¹,N,O²;2κ³O¹,N,O²-diyttrium-tetrahydrofuran-methanol (1/1/1), [Y₂(C₁₄H₁₂NO₂)₃(CH₃O)Cl₂(CH₄O)]·CH₄O·C₄H₈O, (4)·MeOH·THF, and bis(μ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ³O¹,N,O²:2κO¹)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato-2κ³O¹,N,O²)sodiumyttrium chloroform disolvate, [NaY(C₁₄H₁₂NO₂)₄]·2CHCl₃, (5)·2CHCl₃. Structural peculiarities of homoleptic tris(iminophenoxide)s (1)-(3), binuclear tris(iminophenoxide) (4) and homoleptic ate tetrakis(iminophenoxide) (5) are discussed. The nonflat Schiff base ligand displays μ₂-κ³O¹,N,O²:κO¹ bridging, and κ³O¹,N,O² and κ²N,O¹ terminal coordination modes, depending on steric congestion, which in turn depends on the ionic radii of the rare-earth metals and the number of coordinated ligands. It has been demonstrated that interligand dihedral angles of the phenoxide ligand are convenient for comparing steric hindrance in complexes. (4)·MeOH has a flat Y₂O₂ rhomboid core and exhibits both inter- and intramolecular MeO-H...Cl hydrogen bonding. Catalytic systems based on complexes (1)-(3) and (5) have demonstrated medium catalytic performance in acrylonitrile polymerization, providing polyacrylonitrile samples with narrow polydispersity.

(2R,3R)-1,4-Dioxa-spiro-[4.4]nonane-2,3-di-carb-oxy-lic and (2R,3R)-1,4-dioxa-spiro-[4.5]decane-2,3-di-carb-oxy-lic acids

The title compounds, C9H12O6 and C10H14O6, were formed by careful hydrolysis of the corresponding diethyl esters. Their single crystals were grown from an ethyl acetate/hexane mixture. Crystals of both compounds have monoclinic (P21) symmetry with a single mol-ecule in the asymmetric unit. Both crystal structures are very similar and display four -CO-OH⋯O=C(OH)- hydrogen bonds, forming a two-dimensional double-layered framework.

Polyphenylcyclopentadienyl Ligands as an Effective Light-Harvesting π-Bonded Antenna for Lanthanide +3 Ions

A new approach to design "antenna-ligands" to enhance the photoluminescence of lanthanide coordination compounds has been developed based on a π-type ligand-the polyphenyl-substituted cyclopentadienyl. The complexes of di-, tri-, and tetraphenyl cyclopentadienyl ligands with Tb and Gd have been synthesized and all the possible structural types from mononuclear to di- and tetranuclear complexes, as well as a coordination polymer were obtained. All types of the complexes have been studied by single-crystal X-ray diffraction and optical spectroscopy. All terbium complexes are luminescent at ambient temperature and two of them have relatively high quantum yields (50 and 60%). Analysis of energy transfer process has been performed and supported by quantum chemical calculations. The role of a low-lying intraligand charge transfer state formed by extra coordination with K⁺ in the Tb³⁺ ion luminescence sensitization is discussed. New aspects for design of lanthanide complexes containing π-type ligands with desired luminescence properties have been proposed.

Synthesis and characterization of an Fe(i) cage complex with high stability towards strong H-acids

The new iron(i) dioximate showed an unrivaled stability towards strong acids. This calls for a reassessment of the electrocatalytic activity of similar low-valent Co and Fe cage complexes, which have shown to be effective HER electrocatalysts.

An efficient route for design of luminescent composite materials based on polyethylene containing europium dibenzoylmethanate

A Eu-doped luminescent composite material based on polyethylene has been developed and studied by optical spectroscopy, luminescence intensity mapping, and SEM.

Di- and triphenylacetate complexes of yttrium and europium

The significant variety in the crystal structures of rare-earth carboxylate complexes is due to both the large coordination numbers of the rare-earth cations and the ability of the carboxylate anions to form several types of bridges between rare-earth metal atoms. Therefore, these complexes are represented by mono-, di- and polynuclear complexes, and by coordination polymers. The interaction of LnCl3(thf)x (Ln = Eu or Y; thf is tetrahydrofuran) with sodium or diethylammonium diphenylacetate in methanol followed by recrystallization from a DME/THF/hexane solvent mixture (DME is 1,2-dimethoxyethane) leads to crystals of the non-isomorphic dinuclear complexes tetrakis(μ-2,2-diphenylacetato)-κ(4)O:O';κ(3)O,O':O';κ(3)O:O,O'-bis[(1,2-dimethoxyethane-κ(2)O,O')(2,2-diphenylacetato-κ(2)O,O')europium(III)], [Eu(C14H11O2)6(C4H10O2)2], (I), and tetrakis(μ-2,2-diphenylacetato)-κ(4)O:O';κ(3)O,O':O';κ(3)O:O,O'-bis[(1,2-dimethoxyethane-κ(2)O,O')(2,2-diphenylacetato-κ(2)O,O')yttrium(III)], [Y(C14H11O2)6(C4H10O2)2], (II), possessing monoclinic (P21/c) symmetry. The [Ln(Ph2CHCOO)3(dme)]2 molecule (Ln = Eu or Y) lies on an inversion centre and exhibits three different coordination modes of the diphenylacetate ligands, namely bidentate κ(2)O,O'-terminal, bidentate μ2-κ(1)O:κ(1)O'-bridging and tridentate μ2-κ(1)O:κ(2)O,O'-semibridging. The terminal and bridging ligands in (I) are disordered over two positions, with an occupancy ratio of 0.806 (2):0.194 (2). The interaction of EuCl3(thf)2 with Na[Ph3CCOO] in methanol followed by crystallization from hot methanol produces crystals of tetrakis(methanol-κO)tris(2,2,2-triphenylacetato)-κ(4)O:O';κO-europium(III) methanol disolvate, [Eu(C19H15O2)3(CH3OH)4]·2CH3OH, (III)·2MeOH, with triclinic (P-1) symmetry. The molecule of (III) contains two O,O'-bidentate and one O-monodentate terminal triphenylacetate ligand. (III)·2MeOH possesses one intramolecular and four intermolecular hydrogen bonds, forming a [(III)·2MeOH]2 dimer with two bridging methanol molecules.

A structural study of (1RS,2SR,3RS,4SR,5RS)-2,4-dibenzoyl-1,3,5-triphenylcyclohexan-1-ol chloroform hemisolvate and (1RS,2SR,3RS,4SR,5RS)-2,4-dibenzoyl-1-phenyl-3,5-bis(2-methoxyphenyl)cyclohexan-1-ol

(1RS,2SR,3RS,4SR,5RS)-2,4-Dibenzoyl-1,3,5-triphenylcyclohexan-1-ol or (4-hydroxy-2,4,6-triphenylcyclohexane-1,3-diyl)bis(phenylmethanone), C38H32O3, (1), is formed as a by-product in the NaOH-catalyzed synthesis of 1,3,5-triphenylpentane-1,5-dione from acetophenone and benzaldehyde. Single crystals of the chloroform hemisolvate, C38H32O3·0.5CHCl3, were grown from chloroform. The structure has triclinic (P1) symmetry. One diastereomer [as a pair of (1RS,2SR,3RS,4SR,5RS)-enantiomers] of (1) has been found in the crystal structure and confirmed by NMR studies. The dichoromethane hemisolvate has been reported previously [Zhang et al. (2007). Acta Cryst. E63, o4652]. (1RS,2SR,3RS,4SR,5RS)-2,4-Dibenzoyl-3,5-bis(2-methoxyphenyl)-1-phenylcyclohexan-1-ol or [4-hydroxy-2,6-bis(2-methoxyphenyl)-4-phenylcyclohexane-1,3-diyl]bis(phenylmethanone), C40H36O5, (2), is also formed as a by-product, under the same conditions, from acetophenone and 2-methoxybenzaldehyde. Crystals of (2) have been grown from chloroform. The structure has orthorhombic (Pca2₁) symmetry. A diastereomer of (2) possesses the same configuration as (1). In both structures, the cyclohexane ring adopts a chair conformation with all bulky groups (benzoyl, phenyl and 2-methoxyphenyl) in equatorial positions. The molecules of (1) and (2) both display one intramolecular O-H···O hydrogen bond.