Lanthanide perchlorate complexes of 4-nitroquinoline-1-oxide and 5-nitroisoquinoline-2-oxide

Novel complexes of lanthanide perchlorates with 4-nitroquinoline-1-oxide (NQNO) and 5-nitroisoquinoline-2-oxide (NIQNO) have been prepared and characterized. The complexes have the general formulaeLn(NQNO)8(ClO4)3 (whereLn=La-Nd), Ln(NQNO)7(ClO4)3 (whereLn=Gd-Yb),Ln(NIQNO)9(ClO4)3 (whereLn=La-Nd), andLn(NIQNO)7(ClO4)3 (whereLn=Gd-Yb). The IR, proton NMR spectral data indicate the coordination of the N—O group of the ligands to he lanthanide ions.

Complexes of lanthanide perchlorates with two new O,N,O ligands derived from antipyraldehyde and acetic and benzoic acid hydrazides

Antipyrine is a well known ligand for lanthanides (I). A forage through the organic literature of pyrazolones reveals that the 4-position of antipyrine is amenable to a wide variety of organic reactions. It should thus be possible to introduce suitable functional groups at this position and design new multidentate ligands for metal ions. It is also found that the coordination chemistry of lanthanides is much less well developed and far fewer ligands have been used for complexation with lanthanide ions compared to that of the d-transition metal ions. Keeping these points in view we have reported earlier, complexes of lanthanides with a bidentate ligand N,N-diethyl-antipyrine-4-carboxamide (2). In this communication we report the synthesis of two new ligands from Schiff base condensation of antipyraldehyde and the hydrazides of acetic and benzoic acids and the complexes formed by these hydrazones with lanthanide perchlorates.

Complexes of lanthanide perchlorates with two new " O,N,O " ligands derived from antipyraldehyde and acetic and benzoic acid hydrazides

Antipyrlne is a well known llgand for lanthanldes (i). A forage through the organic literature of pyrazolones reveals that the 4-position of antipyrlne is amenable to a wide variety of organic reactions. It should thus be possible to introduce suitable functional groups at this position and design new multidentate ligands for metal ions. It is also found that the coordination chemistry of lanthanides is much less well developed and far fewer ligands have been used for complexation with lanthanide ions compared to that of the d-transition metal ions.

Lanthanide Sulfate Frameworks: Synthesis, Structure, and Optical Properties

Layered lanthanide sulfate compounds with three different structures have been prepared and characterized. The compounds C10H10N2] La(SO4)(2)]center dot 2H(2)O (I), C10H10N2] La(SO4)(2)(H2O)(2)](2) (Ha), C10H10N2]Pr(SO4)(2)(H2O)(2)](2) (IIb), C10H10N2]Nd-2(SO4)(4)(H2O)(2)](2) (IIIa), C10H10N2]Sm-2(SO4)(4)(H2O)(2)](2) (IIIb), and C10H10N2]Eu-2(SO4)(4)(H2O)(2)] 2 (IIIC) have anionic lanthanide sulfate layers separated by protonated bipyridine molecules. The layers are formed by the connectivity between the lanthanide polyhedra and sulfate tetrahedra. The formation of a two-dimensional La-O-La layer (la), Pr-O-Pr chains (IIb), and a tetramer cluster (IIIa) is noteworthy. The compounds exhibit honeycomb (I), square (IIa, IIb), and honeycomb (IIIa-IIIc) net arrangements, when the connectivity between the lanthanide ions is considered. Optical studies indicate the observation of characteristic metal-centered emission at room temperature. The Nd compound (IIIa) exhibits a two-photon upconversion behavior.

Enhancing the photocytotoxic potential of curcumin on terpyridyl lanthanide(III) complex formation

Lanthanide(III) complexes Ln(R-tpy)(cur)(NO3)(2)] (Ln = La(III) in 1, 2; Gd(III) in 5, 6) and Ln(R-tpy)(scur)(NO3)(2)] (Ln = La(III) in 3, 4; Gd(III) in 7, 8), where R-tpy is 4'-phenyl-2,2':6',2 `'-terpyridine (ph-tpy in 1, 3, 5, 7), 4'-(1-pyrenyl)-2,2':6',2 `'-terpyridine (py-tpy in 2, 4, 6, 8), Hcur is curcumin (in 1, 2, 5, 6) and Hscur is diglucosylcurcumin (in 3, 4, 7, 8), were prepared and their DNA photocleavage activity and photocytotoxicity studied. Complexes La(ph-tpy)(cur)(NO3)(2)] (1) and Gd(ph-tpy)(cur)(NO3)(2)] (5) were structurally characterized. The complexes in aqueous-DMF showed an absorption band near 430 nm and an emission band near 515 nm when excited at 420 nm. The complexes are moderate binders to calf-thymus DNA. They cleave plasmid supercoiled DNA to its nicked circular form in UV-A (365 nm) and visible light (454 nm) via O-1(2) and (OH)-O-center dot pathways. The complexes are remarkably photocytotoxic in HeLa cells in visible light (lambda = 400-700 nm) and are non-toxic in the dark. FACScan analysis of the HeLa cells treated with 2 and 4 showed cell death via an apoptotic pathway. Nuclear localization of 1-4 is evidenced from confocal imaging on HeLa cells. The hydrolytic instability of curcumin gets significantly reduced upon binding to the lanthanide ions while retaining its photocytotoxic potential.

The interface makes a difference: lanthanide ion coated vesicles hydrolyze phosphodiesters

Lanthanide ions are strong Lewis acids. Their complexation to a variety of ligands can further enhance their Lewis acidity allowing the hydrolysis of phosphoesters and even DNA. We show that the interaction of lanthanide ions with vesicles from zwitterionic phosphatidylcholine lipids gives supramolecular structures in which the metal ion is loosely coordinated to the surface. This assembly provides a high density of Lewis-acidic metal centres, which hydrolyze phosphodiesters with enhanced rates.

Three-dimensional 3d-4f heterometallic polymers containing both azide and carboxylate as co-ligands

The hydrothermal reaction of Ln(NO3)(3), Ni(NO3)(2), NaN3, and isonicotinic acid (L) yielded two novel 3-D coordination frameworks (1 and 2) of general formula [Ni(2)Ln(L)(5)(N-3)(2)(H2O)(3)] center dot 2H(2)O (Ln = Pr(III) for 1 and Nd(III) for 2), containing Ni-Pr or Ni-Nd hybrid extended three-dimensional networks containing both azido and carboxylate as co-ligands. Both the compounds are found to be isostructural and crystallize in monoclinic system having P2(1)/n space group. Here the lanthanide ions are found to be nonacoordinated. Both bidentate and monodentate modes of binding of the carboxylate with the lanthanides have been observed in the above complexes. Variable temperature magnetic studies of the above two complexes have been investigated in the temperature range 2-300 K which showed dominant antiferromagnetic interaction in both the cases and these experimental results are analyzed with the theoretical models. (c) 2008 Elsevier B.V. All rights reserved.

Mechanisms of transmembrane cation transport studied by nuclear magnetic resonance spectroscopy

Several molecules like ionophores, vitamins, ion-binding cyclic peptides, acidic phospholipids, surfactants are known to expose the inner side of vesicles, to the externally added cations. Whereas ionophores and certain other systems bring about these changes by a selective transport (influx) of the cation by specialized mechanisms known as the carrier and channel mechanism, other systems cause lysis and vesicle fusion. These systems have been successfully studied using1H,31 P and13C nuclear magnetic resonance spectroscopy after the demonstration, fifteen years ago, of the ability of paramagnetic lanthanide ions to distinguish the inside of the vesicle from the outside. The results of these ’nuclear magnetic resonance kinetics’ experiments are reviewed.

Photocytotoxic Lanthanum(III) and Gadolinium(III) Complexes of Phenanthroline Bases Showing Light-Induced DNA Cleavage Activity

Lanthanide complexes of formulation [La(B)(2)(NO3)(3)] (1-3) and [Gd(B)(2)(NO3)(3)] (4-6), where B is a N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1, 4),dipyrido[3,2-d2',3'-f]quinoxaline (dpq in 2,5) and dipyrido[3,2-a2',3'-c]phenazine (dppz in 3, 6), have been prepared, characterized from physicochemical data, and their photoinduced DNA and protein cleavage activity studied The photocytotoxicity of the dppz complexes 3 and 6 has been studied using HeLa cancer cells. The complexes exhibitligand centered bands in the UV region The dppz complexes show thelowest energy band at 380 nm in N,N-dimethylformamide (DMF) The La(III)complexes are diamagnetic. The Gd(III) complexes (4-6) have magneticmoments that correspond to seven unpaired electrons The complexes are1(.)1 electrolytic in aqueous DMF The dpq and dppz complexes in DMFshow ligand-based reductions. The complexes display moderate binding propensity to calf thymus DNA giving binding constant values in the range of 5.7 x 10(4)-5.8 x 10(5) M-1 with a relative order. 3, 6 (dppz)> 2, 5 (dpq) > 1, 4 (phen) The binding data suggest DNA surface and/or groove binding nature of the complexes. The complexes do not show any hydrolytic cleavage of plasmid supercoiled pUC19 DNA. The dpq and dppz complexes efficiently cleave SC DNA to its nicked circular form onexposure to UV-A light of 365 nm at nanomolar complex concentration. Mechanistic studies reveal the involvement of singlet oxygen (O-1(2)) and hydroxyl radical (HO center dot) as the cleavage active species.The complexes show binding propensity to bovine serum albumin (BSA)protein giving K-BSA values of similar to 10(5) M-1. The dppz complexes 3 and 6 show BSA protein cleavage activity in UV-A light of 365 nm The dppz complexes 3 and 6 exhibit significant photocytotoxicity in HeLa cells giving respective IC50 values of 341 nM and 573 nM in UV-A light of 365 nm for an exposure time of 15 min (IC50 > 100 mu M in dark for both the complexes) Control experiments show significant dark and phototoxicity of the dppz base alone (IC50 = 413 nM in light with 4 h incubation in dark and 116 mu M in dark with 24 h incubation). A significant decrease in the dark toxicity of the dppz base is observedon binding to the lanthanide ions while retaining similar phototoxicity.

Photoluminescence of Sr(2-x)Ln(x)CeO(4+x/2) (Ln = Eu, Sm or Yb) prepared by a wet chemical method

A wet chemical route is developed for the preparation of Sr2CeO4 denoted the carbonate-gel composite technique. This involves the coprecipitation of strontium as fine particles of carbonates within hydrated gels of ceria (CeO2.xH(2)O, 40ions. The effect of next-nearest-neighbor (NNN) environment on the Ce4+-O2- CT emission is studied by doping with Eu3+, Sm3+ or Yb3+ which in turn, have unique charge-transfer associated energy levels in the excited states in oxides. Efficient energy transfer occurs from Ce4+-O2- CT state to trivalent lanthanide ions (Ln(3+)) if the latter has CT excited states, leading to sensitizer-activator relation, through non-resonance process involving exchange interaction. Yb3+-substituted Sr2CeO4 does not show any line emission because the energy of Yb3+-O2- CT level is higher than that of the Ce4+-O2- CT level. Sr2-xEuxCeO4+x/2 shows white emission at xless than or equal to0.02 because of the dominant intensities of D-5(2)-F-7(0-3) transitions in blue-green region whereas the intensities of D-5(0)-F-7(0-3) transitions in orange-red regions dominate at concentrations xgreater than or equal to0.03 and give red emission. The appearance of all the emissions from D-5(2), D-5(1) and D-5(0) excited states to the F-7(0-3) ground multiplets of Eu3+ is explained on the basis of the shift from the hypersensitive electric-dipole to magnetic-dipole related transitions with the variation in site symmetry with increasing concentration of Eu3+. White emission of Sr2-x SmxCeO4+x/2 at xless than or equal to0.02 is due the co-existence of Ce4+-O2- CT emission and (4)G(4)(5/2)-H-6(J) Sm3+ transitions whereas only the Sm3+ red emission prevails for xgreater than or equal to0.03. The above unique changes in PL emission features are explained in terms of the changes in NNN environments of Ce4+. Quenching of Ce4+-O2- CT emission by other Ln(3+) is due to the ground state crossover arising out of the NNN interactions.

Exploiting oriented attachment in stabilizing La3+-doped gallium oxide nano-spindles

Retaining the morphology of gallium oxide nanostructures during structural transformations or after doping with lanthanide ions is not facile. Here we report on the sonochemical synthesis of nearly monodisperse similar to 550 nm long nano-spindles of undoped and La-doped alpha-GaOOH. The transformation of as-prepared undoped and La-doped alpha-GaOOH powders into the corresponding undoped and La-doped Ga2O3 phases (alpha and beta) was achieved by carrying out controlled annealing at elevated temperatures under optimized conditions. The formation of gallium oxide nano-spindles is explained by invoking the phenomenon of oriented attachment, as amply supported by electron microscopy. Interestingly, the morphology of the gallium oxide nano-spindles remained conserved even after doping them with more than 1.4 at% of La3+ ions. Such robust structural stability could be attributed to the oriented attachment-type growth observed in the nano-spindles. The as-prepared samples and the corresponding annealed ones were thoroughly characterized by powder X-ray diffraction (PXRD), electron microscopy (SEM, TEM, and STEM-EDS) and X-ray photoelectron spectroscopy (XPS). Finally, photoluminescence from the single-crystalline undoped and La-doped beta-Ga2O3 was explored.

Complexes of lanthanide nitrates with 2-N-(6-picoIyl)-benzamide

New complexes of lanthanide nitrates with 2-N-(6-picolyl)-benzamide of the formulae Ln2[6-pic-BA], [NO3l6 (Ln = Y and La-Yb) have been prepared and characterised by chemical analysis, infrared, molar conductance and electronic spectral data. Molar conductance data along with IR data point to the presence of co-ordinated nitrate groups. IR spectra prove the bidentate co-ordination of the ligand to the metal ion, through the oxygen of the secondary amide and the nitrogen of the heterocyclic ring. Electronic spectral studies in the visible region suggest an eight co-ordinate geometry around the metal ions.

Complexes of lanthanide perchlorates with 2-N-(pyridyl)benzamide

New complexes of lanthanide perchlorates with 2-N-(pyridyl) benzamide (PyBA) of the type Ln(PyBA)3(ClO4)3 where Ln = Y and La---Yb have been synthesised and characterised by analyses, conductance, IR, 13C NMR (for diamagnetic complexes only) and electronic spectra. The molar conductance and IR data point to the ionic nature of the perchlorate groups in the complexes. IR data along with the 13C NMR data unequivocally proves that the coordination of the ligand to the metal ions taken place in a bidentate fashion through the oxygen of the benzamide group and the nitrogen of the heterocyclic ring. From a comparison of the visible electronic spectral shapes of the Nd3+, Ho3+ and Er3+ complexes with those reported in the literature, a 6-coordinate geometry around the metal ion has been assigned in all the complexes.

Complexes of lanthanide nitrates with O,O′,N-triisopropyl phosphoramidate

A substituted phosphoramidate has been used as a ligand to lanthanides for the first time. New complexes of lanthanide nitrates with O,O′,N-triisopropyl phosphoramidate (TIP) of the general formula Ln(TIP)3(NO3)3 where Ln=La-Yb and Y have been synthesised and characterised by chemical analysis, infrared and visible electronic spectra and electrical conductance.Infrared spectra indicate the coordination of the ligand to the metal ions through the oxygen of the P=O group. IR and conductance show that the nitrate groups are all coordinated. Electronic spectral shapes have been interpreted in terms of an eight coordinate geometry around the metal ions.

Amino acid-lanthanide interactions, Part 2. The X-ray crystal structures of lanthanide and calcium complexes of 1-amino-cyclohexane-1-carboxylic acid (Acc6)

The structures of [Nd-2(Acc(6))(H2O)(6)](ClO4)(6) .(H2O)(6) (1) [Er-2(Acc(6))(4)(H2O)(8)](ClO4)(6) .(H2O)(11) (2) and [Ca-5(Acc(6))(12)(H2O)(6)](ClO4)(10).(H2O)(4) (3) (Acc(6) = 1-aminocyclohexane-1-carboxylic acid) have been determined by X-ray crystallography. The lanthanide complexes 1 and 2 are dimeric in which two lanthanide cations are bridged by four carboxylato groups of Acc(6) molecules. In addition, the neodymium complex (1) features the unidentate coordination of the carboxyl group of an Acc(6) molecule in place of a water molecule in the erbium complex (2). The coordination number in both 1 and 2 is eight. The calcium Acc(6) complex (3) is polymeric; three different calcium environments are observed in the asymmetric unit. Two calcium ions are hexa-coordinated and one is hepta-coordinated. Considerable differences are observed between the solid state structures of Ln(III) and Ca-II complexes of Acc(6