Photo-induced DNA cleavage activity and remarkable photocytotoxicity of lanthanide(III) complexes of a polypyridyl ligand

Lanthanide(III) complexes [Ln(pyphen)(acac)(2)(NO3)] (1, 2), [Ln(pydppz)(acac)(2)(NO3)] (3, 4) and [La(pydppz)(anacac)(2)(NO3)] (5), where Ln is La(III) (in 1, 3, 5) and Gd(III) (in 2, 4), pyphen is 6-(2-pyridyl)-1,10-phenanthroline, pydppz is 6-(2-pyridyl)-dipyrido[3,2-a:2',3'-c] phenazine, anacac is anthracenylacetylacetonate and acac is acetylacetonate, were prepared, characterized and their DNA photocleavage activity and photocytotoxicity studied. The crystal structure of complex 2 displays a GdO6N3 coordination. The pydppz complexes 3-5 show an electronic spectral band at similar to 390 nm in DMF. The La(III) complexes are diamagnetic, while the Gd(III) complexes are paramagnetic with seven unpaired electrons. The molar conductivity data suggest 1 : 1 electrolytic nature of the complexes in aqueous DMF. They are avid binders to calf thymus DNA giving K-b in the range of 5.4 10(4)-1.2 x 10(6) M-1. Complexes 3-5 efficiently cleave supercoiled DNA to its nicked circular form in UV-A light of 365 nm via formation of singlet oxygen (O-1(2)) and hydroxyl radical (HO center dot) species. Complexes 3-5 also exhibit significant photocytotoxic effect in HeLa cancer cells giving respective IC50 value of 0.16(+/- 0.01), 0.15(+/- 0.01) and 0.26 +/-(0.02) mu M in UV-A light of 365 nm, while they are less toxic in dark with an IC50 value of >3 mu M. The presence of an additional pyridyl group makes the pydppz complexes more photocytotoxic than their dppz analogues. FACS analysis of the HeLa cells treated with complex 4 shows apoptosis as the major pathway of cell death. Nuclear localization of complex 5 having an anthracenyl moiety as a fluorophore is evidenced from the confocal microscopic studies.

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.

Design and synthesis of near-IR luminescent mesoporous materials covalently linked with tris(8-hydroxyquinolinate) lanthanide(III) complexes

By using the bifunctional ligand, 8-hydroxyquinoline-functionalized organosilane (Q-Si), the new mesoporous material Q-MCM-41 covalently bonded with 8-hydroxyquinoline was synthesized. Through the ligand exchange reaction, the new near-infrared (NIR) luminescent mesoporous LnQ(3)-MCM-41 (Ln = Er, Nd, Yb) materials were prepared by linking the lanthanide quinolinate complexes to the ordered mesoporous Q-MCM-41 material. The LnQ(3)-MCM-41 materials were characterized by powder X-ray diffraction and N-2 adsorption/desorption, and they all show the characteristic mesoporous structure of MCM-41 with highly uniform pore size distributions.

Near-infrared emission from novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15

A novel mesoporous material covalently bonded with 8-hydroxyquinoline (HQ) was synthesized (designated as Q-SBA-15). The 5-formyl-8-hydroxyquinoline grafted to.(3-aminopropyl)triethoxysilane, that is, alkoxysilane modified 8-hydroxyquinoline (Q-Si), was used as one of the precursors for the preparation of the Q-SBA-15 material. On the basis of the other function of the Q-Si of coordinating to lanthanide (Ln) ions, for the first time, the LnQ(3) complexes (Ln = Er, Nd, Yb) have been covalently bonded to the SBA-15 materials.

Studies on the solution structures of lanthanide(III) complexes of DTPA-BIN by NMR

The solution structures of diamagnetic lanthanide (III) complexes of DTPA-BIN (Ln = La, Y, Lu, Sc) have been investigated by H-1 NMR, C-13 NMR and 2D NMR. For each complex, two or more species of asymmetric conformations with little distinction were identified at room temperature. And their solution structures vary with the radius of the central metals. NMR spectra support the hypothesis that Sc3+ with smaller radius formed an eight-coordinated structure with DTPA-BIN, La3+ with larger radius formed nine- or ten-coordinated structures with DTPA-BIN, and Y (DTPA-BIN) and Lu (DTPA-BIN) had nine-coordinated solution structures. The solution structure of Gd (DTPA-BIN) was obtained from the similarity of radius between Gd3+ and Y3+, which is a nine-coordinated structure formed by three nitrogens, three acetate oxygens, two acetyl oxygens, one water molecule and a gadolinium(III) cation.

Structural characterization and luminescence studies of new lanthanide(III) complexes with nicotinic and isonicotinic acid N-oxides

Four new polymeric lanthanide(III) complexes of nicotinic acid N-oxide and isonicotinic acid N-oxide have been synthesized and structurally determined. In the isomorphous compounds [(Ln(L-1)(3) (H2O)(2))(n)]. 4nH(2)O(HL1 = nicotinic acid N-oxide; Ln = Eu, 1; Ln = Er, 2) the lanthanide(III) ions form infinite double chains along the b direction through the coordination of bridging carboxylate and N-oxide groups. The chains are cross-linked through hydrogen bonds between aqua ligands and uncoordinated N-oxide groups and between aqua ligands and lattice water molecules, to form a three-dimensional network. [(Eu(L-2)(2)-(H2O)(4))(n)](NO3)(n). nH(2)O (HL2 = isonicotinic acid N-oxide, 3) has a polymeric structure in which the europium (III) ions are connected into infinite chains by pairs of syn-syn carboxylate groups. Adjacent chains are interlinked by hydrogen bonds between aqua ligands and N-oxide groups to form a layer parallel to the (100) plane, and such layers are connected by hydrogen bonds between nitrate anions and aqua ligands, and between oxide groups and lattice water molecules, into a three-dimensional network. In [(Er-2(L-2)(4)(H2O)(10))](NO3)(2). H2O, 4, dinuclear units are inter-linked into a three-dimensional network through hydrogen bonding between aqua ligands and N-oxide groups of both bidentate bridging and unidentate L-2 ligands. Factors affecting the formation of coordination chains and dinuclear units are discussed. Luminescence properties of 1 and 3 have also been studied. (C) 1998 Elsevier Science Ltd. All rights reserved.

Synthesis and luminescence properties of lanthanide(III) chelates with polyacid derivatives of thienyl-substituted terpyridine analogues

Two new polyacid derivative ligands of thienyl-substituted terpyridine analogues, N,N,N-1,N-1-[4'-(2"'-thienyl)-2,2':6',2"-terpyridine-6,6"-diyl]bis(methylenenitrilo) tetrakis(acetic acid) (TTTA) and N,N,N-1,N-1-[2,6-bis(3'-amino-methyl-1'-pyrazolyl)-4-(2"-thienyl)pyridine] tetrakis(acetic acid) (BTTA), were synthesized, and the luminescence properties of their Eu3+ and Tb3+ chelates were investigated. The Eu3+ chelates of the two ligands are strongly luminescent having luminescence quantum yields of 0.150 (TTTA-Eu3+) and 0.114 (BTTA-Eu3+), and lifetimes of 1.284 ms (TTTA-Eu3+) and 1.352 ms (BTTA-Eu3+), whereas their Tb3+ chelates are weakly luminescent. The TTTA-Eu3+ chelate was used for streptavidin (SA) labeling, and the labeled SA was used for time-resolved fluoroirnmunoassay of insulin in human sera. The method gives the detection limits of 33 pg ml(-1). (C) 2003 Elsevier B.V. All rights reserved.

Mandelohydroxamic acid as ligand for copper(II) 15-metallacrown-5 lanthanide(III) and copper(II) 15-metallacrown-5 uranyl complexes

The formation of pentanuclear copper(ii) complexes with the mandelohydroxamic ligand was studied in solution by electrospray ionization mass spectrometry (ESI-MS), absorption spectrophotometry, circular dichroism and H-1 NMR spectroscopy. The presence of lanthanide(iii) or uranyl ions is essential for the self-assembly of the 15-metallacrown-5 compounds. The negative mode ESI-MS spectra of solutions containing copper(II), mandelohydroxamic acid and lanthanide(iii) ions (Ln = La, Ce, Nd, Eu, Gd, Dy, Er, Tm, Lu, Y) or uranyl in the ratio 5:5:1 showed only the peaks that could be unambiguously assigned to the following intact molecular ions: {Ln(NO3)(2)[15-MCuIIN(MHA)-5](2-)}(-) and {Ln(NO3)[15-MCCuIIN(MHA)-5](3-)}(-), where MHA represents doubly deprotonated mandelohydroxamic acid. The NMR spectra of the pentanuclear species revealed only one set of peaks indicating a fivefold symmetry of the complex. The pentanuclear complexes synthesized with the enantiomerically pure R- or S-forms of mandelohydroxamic acid ligand, showed circular dichroism spectra which were mirror images of each other. The pentanuclear complex made from the racemic form of the ligand showed no signals in the CD spectrum. The UV/ Vis titration experiments revealed that the order in which the metal salts are added to the solution of the mandelohydroxamic acid ligand is crucial for the formation of metallacrown complexes. The addition of copper(ii) to the solutions containing mandelohydroxamic acid and neodymium(iii) in a 5:1 ratio lead to the formation of a pentanuclear complex in solution. In contrary, titration of lanthanide(iii) salt to the solution containing copper(ii) and mandelohydroxamic acid did not show any evidence for the formation of pentanuclear species. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Study of the luminescence of tris(2-thenoyltrifluoroacetonato)lanthanide(III) complexes covalently linked to 1,10-phenanthroline-functionalized hybrid sol-gel glasses

The solubility and uniform distribution of lanthanide complexes in sol-get glasses can be improved by covalently linking the complexes to the sol-gel matrix. In this study, several lanthanide beta-diketonate complexes (Ln = Nd, Sm, Eu, Tb, Er, Yb) were immobilized on a 1,10-phenanthroline functionalized sol-gel glass. For the europium(Ill) complex, a sol-gel material of diethoxydimethylsilane (DEDMS) with polymer-like properties was derived. For the other lanthanide complexes, the sol-gel glass was prepared by using a matrix of tetramethoxysilane (TMOS) and DEDMS. Both systems were prepared under neutral reaction conditions. High-resolution emission and excitation spectra were recorded. The luminescence lifetimes were measured. (c) 2004 Elsevier B.V. All rights reserved.

Intense near-infrared luminescence of anhydrous lanthanide(III) iodides in an imidazolium ionic liquid

Anhydrous neodymium(III) iodide and erbium(Ill) iodide were dissolved in carefully dried batches of the ionic liquid 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(12)mim][Tf2N]. Provided that the ionic liquid had a low water content, intense near-infrared emission could be observed for both the neodymium(III) ion and for the erbium(III) ion. Luminescence lifetimes have been measured, and the quantum yield of the neodymium(III) sample has been measured. Exposure of the hygroscopic samples to atmospheric moisture conditions caused a rapid decrease of the luminescence intensities. (C) 2004 Elsevier B.V. All rights reserved.

Lanthanide(III) nitrobenzenesulfonates as new nitration catalysts: The role of the metal and of the counterion in the catalytic efficiency

Lanthanide(III) complexes of p-nitrobenzenesulfonic acid, Ln(p-NBSA)(3), m-nitrobenzenesulfonic acid, Ln(m-NBSA)(3), and 2,4-nitrobenzenesulfonic acid, Ln(2,4-NBSA)(3), were prepared, characterized and examined as catalyst for the nitration of benzene, toluene, xylenes, naphthalene, bromobenzene and chlorobenzene. The initial screening of the catalysts showed that lanthanum(III) complexes were more effective than the corresponding ytterbium(III) complexes, and that catalysts containing the bulky 2,4-NBSA ligand were less effective than the catalyst containing p-NBSA (nosylate) or m-NBSA ligands. Examination of a series of Ln(p-NBSA)(3) and Ln(m-NBSA)(3) catalysts revealed that there is a clear correlation between the ionic radii of the lanthanide(III) ions and the yields of nitration, with the lighter lanthanides being more effective. The X-ray single crystal structure of Yb(m-NBSA)(3).6H(2)O shows that two m-NBSA ligands are directly bound to the metal centre while the third ligand is not located in the first coordination sphere, but it is hydrogen bonded to one of the water molecules which is coordinated to ytterbium(III). NMR studies suggest that this structure is preserved under the conditions used in the nitration reaction. The structure of Yb(m-NBSA)(3) is markedly different from the structure of the well-known ytterbium(III) triflate catalyst. The coordination of the nitrobenzenesulfonate counterion to the lanthanide(III) ion suggests that steric effects might play an important role in determining the efficiency of these novel nitration catalysts. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

The coordination chemistry of 1,2,4-triazinyl bipyridines with lanthanide(III) elements - implications for the partitioning of americium(III)

It has been established that 6-(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (R,hemi-BTPs) have properties which are intermediate between those of the terpyridines and the bis(1,2,4-triazin-3-yl)pyridines (BTPs). However, they resemble the terpyridines much more closely than the BTPs. It has been shown that Et, hemi-BTP when dissolved in TPH-a dodecane-like solvent-is a selective reagent for the separation of americium(III) from europium(III). Solution NMR in acetonitrile largely confirmed the crystallographic results. There was no evidence for a 1 : 3 complex cation, or for significant differences between metal(III)-N distances for the pyridine and 1,2,4-triazine rings. Intramolecular hydrogen bonding plays a crucial role in the formation of metal coordination spheres, which explains the differences between the terpyridyl, R,hemi-BTPs and the BTPs. Protonation of the R,hemi-BTPs facilitates a conformational change which is necessary for complexation.

Interaction of 6,6′′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2′:6′,2′′-terpyridine (CyMe4-BTTP) with some trivalent ions such as lanthanide(iii) ions and americium(iii)

The new ligand 6,6 ''-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)2,2':6 ',2 ''-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2':6',2 ''-terpyridine. Detailed NMR and mass spectrometry studies indicate that the ligand forms 1 : 2 complexes with lanthanide(III) perchlorates where the aliphatic rings are conformationally constrained whereas 1 : 1 complexes are formed with lanthanide(III) nitrates where the rings are conformationally mobile. An optimized structure of the 1 : 2 solution complex with Yb(III) was obtained from the relative magnitude of the induced paramagnetic shifts. X-Ray crystallographic structures of the ligand and of its 1 : 1 complex with Y(III) were also obtained. The NMR and mass spectra of [Pd(CyMe4-BTTP)](n)(2n+) are consistent with a dinuclear double helical structure (n = 2). In the absence of a phase-modifier, CyMe4-BTTP in n-octanol showed a maximum distribution coefficient of Am(III) of 0.039 (+/-20%) and a maximum separation factor of Am(III) over Eu(III) of 12.0 from nitric acid. The metal(III) cations are extracted as the 1 : 1 complex from nitric acid. The generally low distribution coefficients observed compared with the BTBPs arise because the 1 : 1 complex of CyMe4-BTTP is considerably less hydrophobic than the 1 : 2 complexes formed by the BTBPs. In M(BTTP)(3+) complexes, there is a competition between the nitrate ions and the ligand for the complexation of the metal.

[Pr(NO3)3L]: a mononuclear ten-coordinate lanthanide(III) complex with a tetradentate di-Schiff base

The novel praseodymium(III) complex [Pr(NO3)3L] (1), where L=N,N′-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine, has been obtained by direct reaction of the Schiff base and the metal salt; the gadolinium(III) homologue has also been prepared and so far characterized only spectroscopically. The crystal structure resembles those reported for hexadentate macrocyclic Schiff bases.