Mixed-ligand Lanthanide Complexes Research Articles

Synthesis, crystal structure and photophysical properties of mixed-ligand lanthanide complexes with 1,3-diketonates bearing pyrazole moieties and 1,10-phenanthroline

Three novel lanthanide complexes based on 1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)propane-1,3-dionate (L), namely [Ln(L)3(phen)] (Ln = Gd, Yb, Lu; phen = 1,10-phenanthroline) were synthesized and characterized by spectroscopy and single crystal X-ray study that revealed a monomeric nature for the three compounds. Comparison of the molecular parameters has been made with analogous [Ln(diketonate)3(N2-donor)] species. The peculiarities of the coordination polyhedron and the photophysical properties for the three complexes were discussed. It has been found that, despite relatively high energy of triplet state of the ligand L (T1 = 22,000 cm−1) unfavorable for sensibilization of Yb3+ ion, the ytterbium complex is noticeable luminescent. The emission Stark-splitted maximum in photoluminescence spectrum of [Yb(L)3(phen)] is peaked at 980 nm (NIR-region) and photoluminescence quantum yield (PLQY) is about 0.3%.

Mixed-ligand complexes of lanthanides derived from an α-hydroxycarboxylic acid (benzilic acid) and 1,10-phenanthroline: Physicochemical properties and anticancer activity

The reactions of [Ln(NO3)3·6H2O] (Ln = Pr and Sm), [SmCl3·6H2O] and [Nd(OAc)3·xH2O] with benzilic acid (H2ben) and 1,10-phenanthroline (phen) as an auxiliary ligand in basic media yielded isostructural, nine-coordinate complexes (monoclinic system, space group P21/n) of the type [Ln(Hben)3(phen)2(H2O)]·DMF·H2O (where Ln = Pr(III), Nd(III) and Sm(III)). In the structures, the monodeprotonated Hben− ligand connects the metal centres monodentately through the deprotonated carboxylate oxygen, and bidentately via the hydroxy oxygen and the carboxylate group oxygen. Additional stability of the crystal structures is provided by intra- and inter-molecular OH⋯O interactions, CH⋯O contacts, CH⋯π and parallel-displaced aromatic π⋯π interactions. The electronic absorption spectra of the complexes show π → π* transitions of the bidentate aromatic phen, as well as Laporte-forbidden 4f-4f transitions. Anticancer screen indicated that phen, and the Pr(III) and Nd(III) complexes, significantly reduced MCF-7 cell proliferation (p < 0.05). 1,10-Phenanthroline also exerted cytotoxic effects in HEC-1A cells (p < 0.05).

Mixed-ligand lanthanide complexes constructed by flexible 1,3-propanediaminetetraacetate and rigid terephthalate

Coordination polymers (CPs) of mixed-ligand lanthanide complexes [Ln2(1,3-pdta)(TPA)(H2O)2]n·nH2O [Ln = La, 1; Ce, 2; Pr, 3; Nd, 4] (1,3-H4pdta = 1,3-propanediaminetetraacetic acid; H2TPA = terephthalic acid) were hydrothermally synthesized with flexible 1,3-pdta and rigid TPA ligands. Moreover, lanthanide propanediaminetetraacetates [Ln(1,3-Hpdta)(H2O)]2n·nH2TPA·xH2O [Ln = Sm, 5; Gd, 6] with multi-layered structures were also obtained. In 1–4, both 1,3-pdta and TPA coordinate with lanthanide ions through carboxyl oxygen and nitrogen atoms. In 5 and 6, only 1,3-Hpdta coordinates with the central lanthanide ion, where one nitrogen atom in 1,3-Hpdta is protonated, and TPAs are crystallized as H2TPA with the central multi-layered structures of [Ln(1,3-Hpdta)(H2O)]2n through very strong hydrogen bonds [2.504(4) Å]. Solid-state 13C NMR analysis of 1 revealed the coordination of carboxyl groups. However, the methylene groups of 1,3-pdta showed an obvious upfield shift, which can be attributed to the effects of the phenyl ring in TPA ligand. The successful synthesis of these mixed-ligand lanthanides provides a rational design of such lanthanide CPs with flexible and rigid ligands.

MIXED-LIGAND ACETYLACETONATE COMPLEXES OF LANTANUM (III) AND GADOLINIUM (III) WITH CARBOXYLIC ACIDS AND ACETONITRILE OR DIMETHYLFORMAMIDE

This paper presents the study of mixed-ligand complexes of Ln(III), which are used as volatile precursors in CVD processes for the preparation of lanthanide-containing films and coatings. New mixed-ligand acetylacetonate complexes of lanthanides (III) with acetic (propionic) acid and acetonitrile or dimethylformamide were synthesized and investigated by physic-chemical methods of analysis (elemental analysis, differential thermal analysis, IR spectroscopy, powder X-ray diffraction). Using mixed-ligand complexation, the properties of the initial lanthanide β-diketonates (in particular, chemical and thermal stability) can be changed significantly.&#x0D; To assess the stability of the synthesized mixed-ligand complexes, their quantum-chemical modeling was performed using the semi-empirical method Sparkle/PM7. Standard changes of the Gibbs energy ∆G0298 were calculated for the solution reaction of (1) synthesis of mixed-ligand complexes and (2) substitution of one of the β-diketonate ligands in the Ln(III) tris-acetylacetonates dihydrates by an acetate ion or propionate ion. The ∆G0298 values for the syntesis reaction mainly increases with increasing donor basicity and decreasing ionic radii Ln(III) in the La&gt;Gd&gt;Lu series. For all mixed ligand complexes of Ln(III), the heats of formation are negative, which indicates their thermodynamic stability in solution.&#x0D; It was established that the obtained complexes have the same composition of the general formula [Ln(AA)2·L·2D], where Ln (III) = La, Gd; НАА- acetylacetonе; L - anion of acetic (HAc) or propionic (HРrop) acids, D- acetonitrile (AN), dimethylformamide (DMFA).&#x0D; The results of the thermal analysis confirm the computational data: in the case of the lanthanum mixed-ligand complexes, the carboxylic acid is coordinated to the central ion through bridging carboxylate-ions, which contributes to the formation of oligomers. The lanthanum mixed-ligand complexes are not volatile due to their oligomeric structure. On the other hand, similar gadolinium complexes are monomeric and sublimate at 180 - 350 °C.

Mixed-ligand lanthanide complexes with acylpyrazolones and phosphorus-containing ligands

The reactions of lanthanum acetylacetonate with various phosphorus-containing pesticides, toxic gases, and products of their hydrolysis are modeled by quantum-chemical methods. In the most cases, the enthalpy of substitution for water by organophosphorus compounds is negative. The complexes are studied in solutions using ethyl (diethoxyphosphoryl) acetate as a model compound. The mixed-ligand lanthanide complexes with acylpyrazolones and ethyl (diethoxyphosphoryl) acetate are synthesized. The crystal structure is determined for the samarium complex.

Macrocyclic lanthanide(III) complexes of iminophenol Schiff bases and carboxylate anions: Syntheses, structures and luminescence properties

The mixed-ligand lanthanide(III) complexes derived from the tetraiminodiphenolate (L1H2) or octaiminotetraphenolate (L2H4) macrocyclic ligands and acetate (OAc−) or benzoate (OBz−) anions have been synthesized and structurally characterized. With the ligand combination L1H2 and OBz−, either the dimeric complexes [{Ln(L1H2)}2(μ2-η1:η1-OBz)4](ClO4)2 (Ln=La (1), Nd (2) and Eu (3)) or the monomeric complexes [Ln(L1H2)(η2-OBz)2](ClO4)·n solvent (Ln=Tb (4), Lu (5) and Y (6)) have been obtained. The X-ray crystal structures of 1, 4 and 6 have been determined, of which 4 and 6 have the same structure. L1H2 and OAc− combination affords the dimeric complexes [{Ln(L1H2)(η2-OAc)(μ-OAc)}2](ClO4)2 (Ln=La (7), Nd (8) and Y (9)) and the structure of 9 has been determined. In complexes 1–9, L1H2 uses two imino nitrogens and the two phenolate oxygens for metal coordination, while the other two uncoordinated imine nitrogens are protonated and intramolecularly hydrogen-bonded to the phenolate oxygens. The metal centre in all the cases is 8-coordinate and has distorted square antiprism geometry. With the octaiminotetraphenolate macrocyclic ligand (L2H4) dinuclear complexes of composition [Ln2(L2H4)(OAc)2(NO3)4]·nH2O (Ln=La (10), Pr (11), Nd (12) and Y (13)) have obtained. The structures determined for 11 and 12 have shown that they are isostructural and there are two independent molecules (A and B) in the unit cell. The molecule A has the bond types [Ln2(L2H4)(η2-OAc)2(η2-NO3)2(η1-NO3)2] and its 9-coordinate metal centre obtains a tricapped trigonal prismatic geometry, while the molecule B is [Ln2(L2H4)(η2-OAc)2(η2-NO3)4] whose 10-coordinate metal centre has a sphenocorona geometry. In these compounds, four uncoordinated imine nitrogens are protonated and hydrogen-bonded to the phenolate oxygens. The luminescence spectra of [{Eu(L1H2)}2(μ-OBz)4]2+ (32+) in acetonitrile (at 298K) and in acetonitrile-toluene glassy matrix (at 77K) have been studied.

Synthesis, characterization and biological evaluation of a novel series of mixed ligand complexes of lanthanides(III) with 4[N-(furfural)amino]antipyrine semicarbazone as primary ligand and diphenyl sulfoxide as secondary ligand

A novel series of complexes of lanthanides(III) with 4[N-(furfuralamino]antipyrine semicarbazone (FFAAPS) as the primary ligand and diphenyl sulfoxide (DPSO) as the secondary ligand with the general composition LnX3(FFAAPS)nDPSO (X = NO3 -, n = 1; X = NCS- or ClO4 -, n = 2; Ln = La3+, Pr3+, Nd3+, Sm3+, Gd3+, Tb3+, Dy3+ or Ho3+), is reported. All the synthesized complexes were characterized through various physico-chemical techniques i.e. elemental analysis, conductance measurements and magnetic susceptibilities, spectroscopic and thermal studies. The coordinated FFAAPS behaved as tridentate N,N,O-donor, while DPSO acted as unidentate oxygen donor. Nitrates were bicovalently bonded, while the thiocyanate was coordinated through N-atom. Perchlorate ions did not participate in the coordination sphere. The absorption bands of the representative Pr(III), Nd(III) and Sm(III) complexes in the visible and near infrared region appeared due to transitions from the ground levels to the excited J-levels of 4f-configuration. From the hypersensitive bands, the nephelauxetic effect (β) was calculated. And from the β-values, the covalence factor (b1/2), Sinha parameter (δ%) and the covalency angular overlap (η) were calculated. The ligand and the corresponding lanthanide(III) complexes were simultaneously screened for their antibacterial and antifungal activities. Thermal stabilities of these complexes were studied by thermogravimetric analysis. Depending on the nature of the anionic ligands, the coordination number of the lanthanide(III) in the case of nitrate or thiocyanate complexes was ten, while it was seven in the case of perchlorate complexes.

Synthesis and investigations of mixed-ligand lanthanide complexes with N,N′-dipyrrolidine-N′′-trichloracetylphosphortriamide, dimethyl-N-trichloracetylamidophosphate, 1,10-phenanthroline and 2,2′-bipyrimidine

Coordination compounds with general formula [Ln(L 1) 3phen], where Ln = Nd, Eu, Er, Yb, HL 1 = N,N′-dipyrrolidine-N′′-trichloracetylphosphortriamide, phen = 1,10-phenanthroline; [Ln(L 1) 3bpm], where Ln = La, Nd, Eu, Gd, Er, Y, bpm = 2,2′-bipyrimidine and [{Ln(L 2) 3} 2(μ-bpm)], where Ln = La, Nd, Eu, Gd, Er, Y, HL 2 = dimethyl-N-trichloracetylamidophosphate have been synthesized and characterized by means of IR and UV–Vis spectroscopy. Crystal structures of [Nd(L 1) 3phen] ( 1), [Nd(L 1) 3bpm] ( 2) and [{Nd(L 2) 3} 2(μ-bpm)] ( 3) have been determined. It was found, that in the deprotonated form the phosphoryl ligands (L 1) − and (L 2) − are coordinated to the neodymium atoms in a bidentate manner via the oxygen atoms of the phosphoryl and the carbonyl groups with formation of six-membered metallocycles. In the case of compounds 1 and 2 the 1,10-phenanthroline (or 2,2′-bipyrimidine) molecules are coordinated to the metals in a bidentate manner via the nitrogen atoms. In contrast 2,2′-bipyrimidine acts in the bidentate-bridge mode forming binuclear complex 3. Variable-temperature magnetic susceptibility measurements of 3 and [{Gd(L 2) 3} 2(μ-bpm)] ( 4) reveal a weak antiferromagnetic interaction between the two magnetic centres, whereas in the case of [{Eu(L 2) 3} 2(μ-bpm)] ( 5) the presence of spin–orbit coupling leads to a deviation from the Curie and Curie–Weiss laws.

Synthesis, crystal structures and theoretical study of mixed ligand complexes of lanthanides acetylacetonates with o-phenanthroline and 2,2′-dipyridyl: The unexpected inverted electrostatic trend in stability

Synthesis of mixed ligand complexes [Lu(acac) 3phen] 1 and [Lu(acac) 3dipy] 2 was carried out. Complexes 1 and 2 have mononuclear structures with six oxygen atoms and two nitrogen atoms in the coordination sphere of the central Lu 3+ ion. Theoretical calculations of structures and properties of mixed ligand complexes [Ln(acac) 3Q] (where Ln=La, Gd, Lu; Q=phen, dipy) were performed at the DFT/B3PW91 level. The natural bond orbital analysis (NBO) was used to characterize the electronic structures of complexes. The features of crystal structures of complexes [Ln(acac) 3Q] in lanthanide row were explained taking into account the bond nature. The influence of both nature of central lanthanide ion and neutral additional ligand on structures and properties of complexes under investigation is discussed. The Ln(acac) 3—Q bond energy was found to be decreased from La-based complexes to Lu-based compounds. Thus, the unexpected inverted electrostatic trend, i.e. a decrease in stability along the lanthanide series, has been found out.

NMR Studies of Mixed-Ligand Lanthanide Complexes in Solution: Pseudorotation and Ring Inversion of 18-Crown-6 Molecule in Cerium Subgroup Chelates

1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO3)3(18-crown-6)] (I), [Pr(NO3)3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C2 symmetry axis, the second one with ΔH‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.

NMR Studies of Mixed-Ligand Lanthanide (III) Complexes. Peculiarities of Molecular Structure, Dynamics and Paramagnetic Properties for Cerium Subgroup Chelates with Crown Ethers

The molecular structure, dynamics and paramagnetic properties of the complex cations [Ln(ptfa)2 (18-crown-6)]+ in deuterated toluene were studied for Ln = La, Ce, Pr and Nd. The activation enthalpy values of 68 ± 5, 55 ± 15 and 60 ± 13 kJ mol-1 for the 18-crown-6 conformationalinversion processes for the complexcations of Ce, Pr and Nd, respectively,were obtained. Quantitativeinvestigation of the lanthanide-induced chemical shifts shows a monotonic change of a spatial structure and magnetic susceptibility in comparison with the Bleaney predicted dependence. The free energy of molecular inversion activation for 18-crown-6 molecules in the complex cation [Ln(fod)2(18-crown-6)]+ is 74 ± 9 kJ mol-1 at 363 K, which is a little more than the value of the free energy of activation 64 ± 9 kJ mol-1 at 363 K in the complex cation [Ln(ptfa)2(18-crown-6)]+.

NMR study of mixed-ligand lanthanide complexes. Dynamic structure of cerium beta-diketonates with AN 18-crown-6 macrocycle

NMR study of mixed-ligand lanthanide complexes. Dynamic structure of cerium beta-diketonates with AN 18-crown-6 macrocycle

Heterobimetallic single-source precursors for MOCVD. Synthesis and characterization of volatile mixed ligand complexes of lanthanides, barium and magnesium β-diketonates with d-element containing ligands

Several heterobimetallic complexes of general formula [(M 1 Q) m M 2 (dik) n ], where (M 1 Q) is Cu(salen) or Ni(salen) and M 2 (dik) n is a lanthanide tris(β-diketonate) or an alkali-earth element bis(β-diketonate) with more or less fluorinated diketonato(-) ligands, have been prepared and structurally characterized. Some of them were submitted to thermal and mass spectrometry analyses, and to isothermal vacuum sublimation tests, in view of their potential use as MOCVD single-source precursors for the deposition of heterobimetallic materials. The study stresses upon the influence of the nature of the diketone. of the M 2 cation, and of chemical modification of the salen ligand on the thermal behaviours of the complexes. Some preliminary CVD experiments are also described.

Mixed-ligand lanthanide complexes—X. Interaction of trivalent lanthanides with 1,10-phenanthroline and thiocyanate in alcohol

The interaction of trivalent lanthanide thiocyanates and phen in ethanol results in the formation of the complexes of the type [Ln(phen) 3(SCN) 3], where Ln = La, Pr, Nd, Sm and Eu; and [Ln(phen) 3 (SCN) 3(H 2O)], where Ln = Dy, Ho, Er and Yb. The complexes have been characterized by elemental analyses, molar conductance, IR spectra and thermal analyses. The complexes behave as non-electrolytes in methanol. TGA showed the presence of coordinated water in the case of the heavier lanthanides making them ten-coordinate. The NMR spectra of the complexes of La, Pr, Nd, Sm, Eu and Yb have been studied in DMSO- d 6 and pyridine- d 5. The complexes do not dissociate in DMSO and retain their coordination number. The chemical shift ratios are constant for different phen protons which indicates dipolar nature of the shift. Pyridine coordinates without displacing any ligand and increases the coordination number of the lighter lanthanides from nine to ten.

Mixed-ligand lanthanide complexes—XI. Absorption spectra and hypersensitivity in the complexes of Pr III, Nd III, Ho III and Er III in nonaqueous solutions

Absorption spectra are reported for the mixed-ligand complexes of Pr III, Nd III, Ho III, and Er III containing ligands having nitrogen donors, in four different solvents (pyridine, DMSO, DMF and methanol). The solvents differ with respect to their donor atoms. The oscillator strengths for the hypersensitive and non-hypersensitive transitions have been determined and variations in the oscillator strengths and band shapes with respect to solvent type is rationalized in terms of ligand (solvent) structures and ligand coordination properties. Pyridine has been found most effective in promoting 4 f-4 f intensity and is the strongest ligand in a nephelauxetic sense among the solvents studied.

Synthesis and characterization of some novel hexa-coordinated mixed-ligand complexes of lanthanides with 4-(3,5-diphenyl-2-pyrazolin-1-yl) benzenesulphonic acid

Novel mixed-ligand 1,10-phenanthroline complexes of some lanthanides of the formula [M(phen) 2(DPBS) 2]·DPBS, where phen = 1,10-phenanthroline, DPBS = 4-(3,5-diphenyl-2-pyrazolin-1-yl)benzene sulphonate ion and M = lanthanide and yttrium have been synthesized by the interaction of M(phen) 2(ClO 4) 3 with HDPBS in methanol. These complexes have been characterized by elemental analyses, molar conductances, magnetic measurements, thermogravimetric analyses, XPS, IR and UV-vis spectral studies. An octahedral structure has been proposed for all the complexes, where phen is trans to phen in the equatorial position and two DPBS ligands are trans to each other at the axial positions.

Mixed-ligand lanthanide complexes—VII. Complexes of 1,10-phenanthroline and thiocyanate

The thiocyanatoaqua-tris(1,10-phenanthroline)lanthanide(III)thiocyanates, [Ln(phen) 3(H 2O)(SCN)](SCN) 2 (where Ln = La III and all trivalent lanthanides, except Pm and Lu) have been synthesized and characterized. The molar conductances, IR spectra and thermograms show the presence of both coordinated and non-coordinated thiocyanate. The complexes are eight-coordinate. Very large chemical shifts are observed in the NMR spectra of paramagnetic complexes. The interelectronic and covalency parameters calculated for the complexes show the covalent nature of bonding between the metal and the ligand. The oscillator strengths of the f-f transitions are calculated and discussed. The complexes appear to accept one solvent molecule (DMSO) and become nine-coordinate in solution.

NMR study of mixed-ligand lanthanide complexes. Structure and stoichiometry of cerium subgroup chelates with 18-membered macrocyclic polyethers

NMR study of mixed-ligand lanthanide complexes. Structure and stoichiometry of cerium subgroup chelates with 18-membered macrocyclic polyethers

Synthesis and thermal stability of mixed-ligand lanthanide complexes involving both cyclopentadienyl and two different chelate ligands—trifluoroacetato and either 8-quinolinolato or o-aminophenolato ligands

Eight new mixed-ligand lanthanide complexes of the general formula CpLnLL′ [Ln = Sm, Dy, Ho, Yb; Cp = C 5H 5; L = CF 3COOO; L′ = 8-O C 6H 3N : CHCH : C H, OC 6H 4( o-NH 2)] have been synthesized. All the complexes were characterized by elemental analysis, IR, XPS and MS spectra, showing that they are dimers with carboxylate ions as bridging groups, and the donor atom nitrogen in each complex coordinates with the metal. Their thermal stability has been studied and discussed. All these complexes are thermally unstable, and at moderately high temperatures they tend to disproportionate into a mixture of Cp 2LnL, Cp 2LnL′, LnL 3 and LnL′ 3.

NMR studies of mixed-ligand lanthanide complexes. Reaction of ?-diketonates of the yttrium subgroup with 18-crown-6

NMR studies of mixed-ligand lanthanide complexes. Reaction of ?-diketonates of the yttrium subgroup with 18-crown-6