Interactions of praseodymium and neodymium with nucleosides and nucleotides: absorption difference and comparative absorption spectral study.

The interactions of praseodymium(III) and neodymium(III) with nucleosides and nucleotides have been studied in different stoichiometry in water and water-DMF mixtures by employing absorption difference and comparative absorption spectrophotometry. The 4f-4f bands were analysed by linear curve analysis followed by gaussian curve analysis, and various spectral parameters were computed, using partial and multiple regression method. The magnitude of changes in both energy interaction and intensity were used to explore the degree of outer and inner sphere coordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Crystalline complexes of the type [Ln(nucleotide)2(H2O)2]- (where nucleotide--GMP or IMP) were characterized by IR, 1H NMR, 31P NMR data. These studies indicated that the binding of the nucleotide is through phosphate oxygen in a bidentate manner and the complexes undergo substantial ionisation in aqueous medium, thereby supporting the observed weak 4f-4f bands and lower values for nephelauxetic effect (1-beta), bonding (b) and covalency (delta) parameters derived from coulombic and spin orbit interaction parameters.     

New complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin

New solid complex compounds of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin were synthesized. The molecular formula of the complexes is Ln(C₁₅H₉O₇)₃ · nH₂O, where Ln is the cation of lanthanide and n = 6 for La(III), Sm(III), Gd(III) or n = 8 for Ce(III), Pr(III), Nd(III) and Eu(III). Thermogravimetric studies and the values of dehydration enthalpy indicate that water occurring in the compounds is not present in the inner coordination sphere of the complex. The structure of the complexes was determined on the basis of UV-visible, IR, MS, ¹H NMR and ¹³C NMR analyses. It was found that in binding the lanthanide ions the following groups of morin take part: 3OH and 4CO in the case of complexes of La, Pr, Nd, Sm and Eu, or 5OH and 4CO in the case of complexes of Ce and Gd. The complexes are five- and six-membered chelate compounds.     

Solution studies of lanthanide (III) complexes based on 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and 1,10-phenanthroline Part-I: Synthesis, H NMR, 4f-4f absorption and photoluminescence

Solution studies on the complexes of the type [Ln(hfaa)₃(phen)₂] (Ln = La, Pr and Nd) and [Ln(hfaa)₃phen] (Ln = Nd, Ho, Er and Yb; hfaa stands for the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and phen stands for 1,10-phenanthroline) are presented. These complexes are synthesized in high yields by an in situ method in which hfaa, ammonium hydroxide, lanthanide chlorides and phen were allowed to react in 3:3:1:1 molar ratio in ethanol. In the case of neodymium both eight- and ten-coordinate complexes are isolated. The paramagnetic shifts of the methine protons of β-diketone have their sign opposed to those of paramagnetic shifts of phen protons and the shifts are dominated by dipolar interactions. The inter- and intramolecular shift ratios have been calculated and discussed. The 4f-4f absorption spectra of the complexes of Pr, Nd, Ho and Er are analyzed. The eight- and ten-coordinate neodymium complexes display distinctively different band shapes of the ⁴G_5/2,²G_7/2 ← ⁴I_9/2 hypersensitive transition. The efficient energy transfer from ligand to Pr(III) is reflected by strong red luminescence of this complex at room temperature.     

Spectroscopic studies on the interaction of Au(III) with nucleosides,nucleotides, and dimethyl phosphate

A series of complexes of Au(III) with nucleosides and nucleotides and their methyl derivatives in different stoichiometry have been prepared. Ultraviolet, visible, ir, and nmr studies have been performed to determine the site of binding of these ligands with the metal ion. In (1:4) Au(III): guanosine complex, N₇ is the binding site, whereas at 1:1 complex, a bidentate type of chelation through C₆O and N₇ is observed. C₆-NH₂ is favored over N₁ as coordinating site at all stoichiometry in the adenosine complex. Inosine binds through N₁ at r = 1. In cytidine, N₁ is the binding site, whereas thymidine reacts only at high pH. In the case of nucleotides a bidentate type of chelation through the phosphate and the ring nitrogen occurs. The phosphate binding ability of Au(III) was further confirmed by studying the interaction of Au(III) with dimethyl phosphate—a conformational analog of the phosphate backbone in DNA chain.     

Nature and composition of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Dy(III) and Ho(III) complexes of embelin

The isolation and characterization of nine polymeric complexes of the general formula [M(L)_1.5S₂]_n (where M is the metal ion, L the ligand and S the solvent, C₂H₅OH) of La(III) and Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Ho(III) with.the biologically active compound embelin using elemental and thermal analysis, infrared and electronic spectral studies is reported.     

Absorption and emission spectra of neodymium(III) and europium(III) complexes

The absorption and emission spectra of several complexes of neodymium(III) and europium(III) ions have been examined in order to obtain reliable information relating to coordination number, nature of bonding and symmetry around the lanthanide ion. It has been found that steric factors may force the polyhedron of coordination towards geometries less favourable by ligand–ligand repulsion. In general, no correlation has been found to exist between the low intensity of the hypersensitive transitions and high symmetry or low symmetry and high intensity. The results have pointed out the role of covalency in hypersensitivity.     

Interaction of saccharides with rare earth metal ions: synthesis and characterisation of Pr(III)- and Nd(III)-saccharide complexes

A number of complexes are synthesised with Pr(III) and Nd(III) employing the mono- and disaccharides, D-glucose, D-galactose, D-mannose, D-arabinose, D-ribose, D-xylose, maltose and lactose. The complexes are characterised by various spectral and analytical techniques, and based on these data, appropriate structures were assigned for all complexes.     

Covalent binding of LTA(4) to nucleosides and nucleotides

Leukotriene A(4) (LTA(4)) is a chemically reactive conjugated triene epoxide that is formed by 5-lipoxygenase and is an intermediate in the formation of the biologically active eicosanoids leukotriene B(4) and leukotriene C(4). The present study was undertaken to determine whether or not LTA(4) could serve as an electrophilic species that nucleosides and nucleotides could attack, ultimately resulting in a covalent adduct. Electrospray ionization mass spectrometry and tandem mass spectrometry were used to study the covalent binding of LTA(4) with uridine, cytidine, adenosine, and guanosine. The reaction with guanosine was found to yield five major and at least six minor adduct species. Reversed phase HPLC and mass spectrometric data suggested that the guanosine attacked LTA(4) either at carbon-12 or carbon-6 with opening the epoxide at carbon-5 to yield a series of adducts characterized by the molecular anion [M-H](-) at m/z 600.3. Reactions of LTA(4) with mixtures of nucleosides and nucleotides revealed that guanine-containing nucleosides were the most reactive toward LTA(4). The facility of the reaction of guanine with LTA(4) raises the possibility that this intermediate of leukotriene biosynthesis formed on or near the cellular nuclear envelope may react with nucleosides and nucleotides present in RNA or DNA.     

Theoretical and spectroscopic evidence for coordination ability of 3,3'-benzylidenedi-4-hydroxycoumarin. New neodymium (III) complex and its cytotoxic effect

Theoretical and spectroscopic studies of 3,3'-benzylidenedi-4-hydroxycoumarin (bhc) have been performed. B3LYP/6-31G* calculations reproduced the experimental molecular structure of bhc and showed two O-H...O asymmetrical intramolecular hydrogen bonds with O...O distances 2.638 and 2.696 A. The calculated Fukui functions and Molecular Electrostatic Potential for bhc and its deprotonated form, bhc(2-), predicted that the most probable reactive sites for electrophilic attack and hydrogen bonds are the carbonyl oxygens, followed by the hydroxyl oxygens. The coordination ability of 3,3'-benzylidenedi-4-hydroxycoumarin has been proved in a complexation reaction with neodymium (III) ion. The new neodymium (III) complex of bhc was studied by elemental analyses, conductivity and other physical properties, mass spectra, (1)H, (13)C NMR, UV-Vis and IR spectroscopy. The data obtained are in agreement with the metal:ligand ratio of 1:1, and the formula Nd(bhc(2-))(OH)(H(2)O), where bhc(2-)=C(25)H(14)O(6)(2-). The vibrational analysis of the neodymium (III) complex, free bhc, and its monomeric building block, 4-hydroxycoumarin, showed that in the Nd(III) complex the ligand coordinates to the metal ion through both deprotonated hydroxyl groups. The participation of both carbonyl groups in coordination to the metal ion was confirmed by the significant shift of nu(C=O) to lower wavenumber. The evaluation of the cytotoxic activity of the new Nd(III) complex on SKW-3 and HL-60/Dox cells revealed, that it is a potent cytotoxic agent and should be subset further to more detailed pharmacological and toxicological study.     

Serologic and chemical differentiation of human lambda III light chain variable regions

Human lambda L chains of a major V lambda subgroup, V lambda III, have been differentiated serologically and chemically into three V lambda III sub-subgroups designated V lambda IIIa, V lambda IIIb, and V lambda IIIc. Antisera prepared against lambda III Bence Jones proteins were obtained that recognized distinctive V lambda III-related epitopes expressed by monoclonal lambda III L chains. After appropriate absorption, these reagents were rendered specific for three distinct populations of lambda III proteins--lambda IIIa, lambda IIIb, and lambda IIIc. The antisera were used in comparative immunodiffusion analyses of 28 monoclonal lambda III L chains, 10 of which were classified as lambda IIIa, 4 as lambda IIIb, and 14 as lambda IIIc. The isotypic nature of the three lambda III sub-subgroups was demonstrated serologically through analyses of lambda-chains derived from the serum IgG molecules of normal individuals. The amino acid sequences of five serologically classified lambda III chains, which included members of the three V lambda III sub-subgroups, had been previously determined. This information, in addition to our establishment of the complete (or virtually complete) V region sequence of 15 and the partial sequence of eight other lambda IIIa, lambda IIIb, and lambda IIIc proteins, made it possible to correlate chemical data with serologic classification. Proteins within each of the three serologically-classified lambda III sub-subgroups typically possessed a high degree (approximately 83%) of intra-sub-subgroup sequence homology that included both framework and complementarity determining region residues. Furthermore, within the framework and complementarity determining regions, sub-subgroup-specific residues were identified. Taken together, these data reveal that the human V lambda III genome consists of (at least) three distinct V lambda IIIa, V lambda IIIb, and V lambda IIIc germline genes that encode for lambda IIIa, lambda IIIb, and lambda IIIc L chains, respectively.     

N,N′-Ethylene-bis(3-methoxysalicylideneimine) mononuclear (4f) and heterodinuclear (3d–4f) metal complexes: Synthesis, crystal structure and luminescent properties

The stepwise synthesis of mononuclear (4f) and heterodinuclear (3d–4f) Salen-like complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, reactions of ligand H₂L and Ln(NO₃)₃ · 6H₂O give rise to three mononuclear lanthanide complexes Ln(H₂L)(NO₃)₃ [H₂L = N,N′-ethylene-bis(3-methoxysalicylideneimine), Ln = Nd (1), Eu (2) and Tb (3)], in which N,N′-ethylene-bis(3-methoxysalicylideneimine) acts as tetradentate ligands with the O₂O₂ set of donor atoms capable of effective coordination. These species are fairly stable and have been isolated. Then, addition of Cu(Ac)₂ · H₂O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes Cu(L)Ln(NO₃)₃ · H₂O [Ln = Nd (4) and Eu (5)] where the Cu(II) ion is inserted to the inner N₂O₂ cavity. Luminescent analysis reveals that complex 3 exhibits characteristic metal-centered fluorescence of Tb(III) ion. However, the characteristic luminescence of both Sm(III) and Eu(III) ions is not observed both in solution and solid state of the complexes.     

Triamminemonoaquocobalt(III) complexes of pyrophosphate and adenosine diphosphate (ADP)

Cobalt(III)H2O(NH3)3 pyrophosphate has been shown by proton and 31P nuclear magnetic resonance (NMR) to be a facial bidentate complex. Cobalt(III)H2O(NH3)3 adenosine diphosphate has been resolved into lambda and delta isomers by chromatography on cycloheptaamylose. Both the lambda and delta forms are a pair of isomers that are not separated by cycloheptaamylose, reverse phase high-pressure liquid chromatography (HPLC), or cation exchange chromatography. These isomers presumably represent syn- and anti-arrangement of coordinated water and adenosine.     

Coordination polymers of Ln(III): Synthesis, characterization, catalytic and antimicrobial aspects

Coordination polymers of HEAP-ED with La(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III) and Dy(III) metal ions have been synthesized and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, FTIR, NMR, scanning electronic microscopy (SEM) and thermogravimetric analyses. Catalytic activity of selected coordination polymers was examined for pharmaceutical important organic synthesis. Antimicrobial activity of isolated Ln(III) coordination polymers against Escherichia coli, Bacillus subtilis, Staphylococcus aureus (bacteria) and Saccharomyces cerevisiae (yeast) were measured. It was observed from the study that the Ln(III) coordination polymers acted as an efficient and effective catalysts and antimicrobial agents.     

New binuclear model compounds for the study of the 4f-4f exchange interaction

Two new homobinuclear 4f-4f complexes, [Ln^III(L)₃]₂, (Ln=Pr 1; Gd 2) have been synthesized (L⁻=2,6-diformyl-4-methylphenolato). The crystallographic investigation of 1 reveals centrosymmetric binuclear entities with the metallic centers connected by two of the anionic ligands. The praseodymium ions are bridged by the phenoxo oxygen atoms. One carbonyl group of a bridging molecule is coordinated to one Pr(III) ion, while the other one is coordinated to the second Pr(III) ion. The other four L⁻ ions act as terminal chelated ligands, through the phenoxo oxygen atom and one carbonyl group. The distance between the Pr(III) ions within the binuclear entity is 4.0711(4) Å. The supramolecular solid-state architecture is sustained by a system of π-π interactions. The cryomagnetic study of 2 reveals a very weak antiferromagnetic interaction between the Gd(III) ions (J=−0.053 cm⁻¹, ).     

Ultraviolet and magnetic-circular-dichroic spectroscopic studies of Gd(III) complexed with diethylenetriaminepentaacetic acid. A contrast agent for NMR imaging

Sensitive probes are required for studying the biochemistry of Gd(III) contrast agents used in magnetic resonance imaging. We show that complexation of Gd(III) by diethylenetriamine-N,N,N',N',N"-pentaacetic acid (DTPA) in aqueous solution can be readily determined from the sharp 4f-4f bands for free and bound Gd(III) in the range 270-282 nm, and, with greater sensitivity, from the associated magnetic-circular-dichroic spectra.     

Heteroleptic phthalocyaninato-[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth(III) triple-deckers: synthesis and spectroscopic characterization

The homo-dinuclear heteroleptic phthalocyaninato-[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth(III) triple-decker complexes (Pc)M[Pc(OC₈H₁₇)₈]M[Pc(OC₈H₁₇)₈] (M=Pr, Nd, Sm, Eu, Tb, Dy, Y, Ho, Er, Tm) (1a–10a) and (Pc)M[Pc(OC₈H₁₇)₈]M(Pc) (M=Nd, Sm, Eu, Tb, Dy, Y, Ho, Er, Tm) (2b–10b) were obtained by condensation of bis(phthalocyaninato) rare earths M[Pc(OC₈H₁₇)₈]₂ (M=Pr, Nd, Sm, Eu, Tb, Dy, Y, Ho, Er, Tm), Li₂(Pc) and M(acac)₃·nH₂O (M=Pr, Nd, Sm, Eu, Tb, Dy, Y, Ho, Er, Tm). These novel compounds were characterized by ¹H NMR, mass, electronic absorption (UV–Vis), and IR spectroscopic methods.     

Synthesis,electrochemistry and spectroscopy of lanthanide(III) homodinuclear complexes bridged by polyazine ligands

Six new complexes [Eu(tta)₃]₂bpm, [Er(tta)₃]₂bpm, [Tb(tta)₃]₂bpm, [Er(tta)₃]₂dpp, Pr(tta)₃bpm and Nd(tta)₃bpm (tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, bpm = 2,2′-bipyrimidine, dpp = 2,3-bis(2-pyridyl)pyrazine) were prepared and studied. The electronic absorption spectra of the complexes display tta π → π* transitions in the UV region. Cyclic voltammetry of the complexes show an irreversible reduction followed by a reversible reduction both associated with the tta ligand. Eu(III) reduction in the homodinuclear [Eu(tta)₃]₂bpm complex occurs as an irreversible reduction at less negative potentials than the tta-based reductions. Emission spectra of the Eu(III) and Tb(III) bimetallics are typical of this type of bonding motif with ligand centered (tta) absorptions resulting in 4f–4f transitions in the visible and near infrared region.     

Interaction of some fluorinated nucleic acid components with praseodymium: an absorption spectral approach

Absorption difference and comparative absorption spectrophotometric studies on praseodymium(III) and fluorouracil, fluorocytosine, fluoroadenine, fluorothymine, fluorouridine, fluorocytidine, fluoroadenosine and fluorothymidine systems at pH approximately 5.5 and in different stoichiometries in 80% DMF medium have been carried out. Magnitudes of spectral parameters, viz. Coulombic (Fk), spin-orbit (zeta 4f), nephelauxetic (beta), bonding (b), intensity (T lambda Judd-Ofelt), and oscillator strength (P) and their variation have provided information on the binding mode of these biomolecules in terms of outer and inner sphere complexation, degree of covalency and extent of 4f orbital involvement. Preliminary ultrasonic studies have indicated that these biomolecules behave as structure breakers, hence weak ligands in aqueous medium, while strengthening water structure in semi-nonaqueous medium. The analysis of the isolated solid complexes has suggested octa- and nona-coordination for praseodymium(III) in fluorinated nucleic bases and fluorinated nucleoside complexes.     

Interaction of Fe(III)- and Zn(II)-tetra(4-sulfonatophenyl) porphyrins with ionic and nonionic surfactants: aggregation and binding

Interactions of the water soluble Fe(III)- and Zn(II)-tetra(4-sulfonatophenyl) porphyrins, FeTPPS(4) and ZnTPPS(4), with ionic and nonionic micelles in aqueous solutions have been studied by optical absorption, fluorescence, resonance light-scattering (RLS), and 1H NMR spectroscopies. The presence of three different species of both Fe(III)- and Zn(II)TPPS(4) in cationic cetyltrimethylammonium chloride (CTAC) solution has been unequivocally demonstrated: free metalloporphyrin monomers or dimers (pH 9), metalloporphyrin monomers or aggregates (possibly micro-oxo dimers) bound to the micelles, and nonmicellar metalloporphyrin/surfactant aggregates. The surfactant:metalloporphyrin ratio for the maximum nonmicellar aggregate formation is around 5-8 for Fe(III)TPPS(4) both at pH 4.0 and 9.0; for Zn(II)TPPS(4) this ratio is 8, and the spectral changes are practically independent of pH. In the case of zwitterionic N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and non-ionic polyoxyethylene lauryl ether (Brij-35) and t-octylphenoxypolyethoxyetanol (Triton X-100), the nonmicellar aggregates were not observed in the pH range from 2.0 to 12.0. Binding constants were calculated from optical absorption data and are of the order of 10(4) M(-1) for both CTAC and HPS, values which are similar to those previously obtained for the porphyrin in the free base form. For Brij-35 and Triton X-100 the binding constant for ZnTPPS(4) at pH 4.0 is a factor of 3-5 lower than those for CTAC and HPS, while in the case of FeTPPS(4) they are two orders of magnitude lower. Our data show that solubilization of ZnTPPS(4) within nonpolar regions of micelles is determined, in general, by nonspecific hydrophobic interactions, yet it is modulated by electrostatic factors. In the case of FeTPPS(4), the electrostatic factor seems to be more relevant. NMR data indicated that Fe(III)TPPS(4) is bound to the micelles predominantly as a monomer at pH 4.0, and at pH 9.0 the bound aggregated form (possibly micro-oxo dimers) remains. The metalloporphyrins were incorporated into the micelles near the terminal part of their hydrocarbon chains, as evidenced by a strong upfield shift of the corresponding peaks of the surfactants.     

Spectroscopic studies on the interaction of quercetin-terbium(III) complex with calf thymus DNA

The interaction of native calf thymus DNA (CT-DNA) with quercetin-terbium(III) [Q-Tb(III)] complex at physiological pH was monitored by UV absorption spectrophotometry, circular dichroism, fluorescence spectroscopy, and viscosimetric techniques. The complex displays binding properties to the CT-DNA and was found to interact with CT-DNA through outside binding, demonstrated by a hypochromic effect of Q-Tb(III) on the UV spectra of CT-DNA and the calculated association constants (K). Also, decrease in the specific viscosity of CT-DNA, decrease in the fluorescence intensity of Q-Tb(III) solutions in the presence of increasing amounts of CT-DNA, and detectable changes in the circular dichroism spectrum of CT-DNA are other evidences to indicate that Q-Tb(III) complex interact with CT-DNA through outside binding.