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The nature of the ternary complexes formed in aqueous media at ambient pH on reversible binding of acetate, lactate, citrate, and selected amino acids and peptides to chiral diaqua europium, gadolinium, or ytterbium cationic complexes is examined. The polarizability of the axial donor plays the dominant role in determining the magnetic anisotropy factor that defines the spectral form and dipolar NMR shift of these monocapped square antiprismatic Eu and Yb complexes.

Crystal structures and CD and absorption spectra of simple heterobimetallic transition metal binaphtholates are discussed with information on syntheses. Seven-coordinate rare earth metal complexes with the (LnM(sub.3)(binaphtholate)(sub.3)(OH(sub.2)THF(sub.6)) form where M is an alkali metal and Ln is a lanthanide ion have been isolated and studied and are called heterobimetallic. They have lanthanide ions with the alkali metal ions of the three THF(sub.2)M(super.+) units coordinated to the oxygen atoms of adjacent binaphtholates. The compounds catalyze various reactions.

Metal complexes of a new chiral N2O2 tetradentate ligands H2L1 and H2L2 have been synthesized from chiral precursors. X-ray crystallography was used in studying the crystal structures of both ligands which coordinate from the Ni(II) to the Cu(II) ions. They have C2 symmetry, have hard tertiary nitrogen and alcohol(ate) donors and with central chelate units that incorporate the 1R,2R-diaminocyclohexane unit. Their chiral centers and attached substituents can be altered to allow performance comparisons with related complexes.

The complexes formed from one, two and three electron reduction of delta-(Ru bpy3)2+ and delta-(Os bpy3)2+ were examined by obtaining their electronic absorption and circular dichroism spectra. The results showed that the added electrons are localized on individual bipyridine ligands. The luminescence spectra of the triply reduced species were also obtained.

The electrochemical analysis of iron(2) complexes of 2,2'-bipyridine, 2,2'-bipyrimidine, 1,10-phenanthroline and 2, 2':6',2''-terpyridine showed that all the complexes undergo a three-step one-electron reversible reduction except for terpyridine complexes which involve a two-step one-electron reduction. Moreover, all the four complexes featured a single one-electron reversible oxidation with electrochemical potentials ranging from +0.785 to +1.036. In addition, the application of ultraviolet-vis-near-infrared spectroscopy in the examination of the products provided reliable results.

A study was conducted to examine the magnetic properties of the compound [[C[(N[H.sub.2]).sub.3]].sub.8]{[Co.sub.4][(cit).sub.4]}.4[H.sub.2]O, which contains an anionic cobalt(II) cubane single-molecule magnet [{[Co.sub.4][(cit).sub.4]}.sup.8-] with [S.sub.4] symmetry. The cobalt(II) citrate cubane compound was observed to display distinct, frequency-dependent peaks in the out-of-phase component of the ac magnetic susceptibility and magnetization versus field hysteresis loops that are temperature and sweep rate dependent.

The formation of novel, highly symmetrical, coordination-driven lanthanide self-assemblies, or bundles ('The Trinity Sliotar') from simple chiral pyridyldiamide ligands (S,S) and (R,R) is described. It is shown that the chirality of these ligands is transferred during the self-assembly to give either [DELTA] or [LAMDA] metal stereochemistry.

The hybrid azomacrocycle, which are the crown ether receptors, can be readily produced using well-established synthetic procedures. The crown ether is designed to act as a host toward biologically relevant guests, whereas the macrocycle can coordinate a zinc(II) or a copper(II) ion.

The first circular dichroism (CD) measurements on carbon K-edge absorption spectrum of methyloxirane in the vapor phase are discussed. This dichroism agrees with previous calculations, which indicates a considerable hybridization that occurs between the core 1s and the valence molecular states.

The lanthanide directed self-assembly of chiral amphiphilic 2,6-pyridinedicarboxylic acid based ligands 1 and 2 with various Ln(CF3SO3)3 (Ln = TbIII, SmIII, LuIII, DyIII) salts was studied in CH3CN and evaluated with the expected 1 : 3 and 1 : 1 Ln : Ligand species forming in solution. Ligand chirality was retained and transferred, as depicted by circular dichroism (CD) and circularly polarised luminescence (CPL) measurements (for TbIII and SmIII), to the lanthanide centre upon complexation with high dissymmetry factor values for the SmIII complexes obtained (glum = −0.44 and 0.29 and 0.45 and −0.23 for the 4G5/2→6H5/2 and the 4G5/2→6H7/2 transitions of Sm·13 and Sm·23, respectively). The ability of the complexes to form stable Langmuir monolayers at the air–water interface was also established while Langmuir–Blodgett films of Tb·L3 and Sm·L3 exhibited lanthanide luminescent emission. [ABSTRACT FROM AUTHOR]

A study is conducted to explain the symmetric coupling of two carbon-di-oxide molecules. These molecules are merged electrochemically to form the oxalate anion.

The theory of XNCD is discussed and the circular dichroism is shown to be due to the interference between the allowed electric dipole and electric quadrupole transition moments. For the study of both molecular and crystal structural enantiomorphism, this new spectroscopy represents as a useful extension to techniques.

Chiral lanthanide-based supramolecular structures have gained significant importance in view of their application in imaging, sensing and other functional purposes. We have designed chiral C2-symmetrical ligands (L) based on the use of two 2,6-pyridine-dicarboxylic-amide moieties (pda), that differ from one another by the nature of the diamine spacer groups (from 1,3-phenylenedimethanamine (1(S,S), 2(R,R)) and benzene-1,3-diamine (3(S,S), 4(R,R)) to much bulkier 4,4′-(cyclohexane-1,1-diyl)bis(2,6-dimethylaniline) (5(S,S), 6(R,R))) between these two pda units. The self-assembly between L and Eu(iii) ions were investigated in CH3CN solution at low concentration whereby the changes in the absorbance, fluorescence and Eu(iii)-centred emission spectra allowed us to model the binding equilibria occurring in the solution to the presence of [Eu:L2], [Eu2:L2], [Eu2:L3] assemblies and reveal their high binding constant values. The self-assembly in solution were also studied at higher concentration by following the changes in the 1H NMR spectra of the ligands upon Eu(iii) addition, as well as by using MALDI-MS of the isolated solid state complexes. The chiroptical properties of the ligands were used in order to study the structural changes upon self-assembly between the ligands and Eu(iii) ions using circular dichroism (CD) and circularly polarised luminescence (CPL) spectroscopies. The photophysical properties of [Eu2:L3] complexes were evaluated in solution and showed a decrease of luminescence quantum yield when going from the ligand with smaller (1(S,S)) to bulkier (5(S,S)) linker from ∼5.8% to ∼2.6%. While mass-spectrometry revealed the possible formation of trinucler assemblies such as [Eu3:L3] and [Eu3:L2]. [ABSTRACT FROM AUTHOR]

The use of X-ray natural circular dichroism (XNCD) to measure the isolated pre-edge transition of a transition metal complex is described. Chiral multiple scattering paths which are responsible for CD in the photoelectron continuum adsorption are identified.

Here we have investigated the influence of the antenna group position on both the formation of chiral amphiphilic EuIII-based self-assemblies in CH3CN solution and, on the ability to form monolayers on the surface of quartz substrates using the Langmuir-Blodgett technique, by changing from the 1-naphthyl ( 2( R), 2( S)) to the 2-naphthyl ( 1( R), 1( S)) position. The evaluation of binding constants of the self- assemblies in CH3CN solution was achieved using conventional techniques such as UV/Visible and luminescence spectroscopies along with more specific circular dichroism (CD) spectroscopy. The binding constants obtained for EuL, EuL2 and EuL3 species in the case of 2-naphthyl derivatives were comparable to those obtained for 1-naphthyl derivatives. The analysis of the changes in the CD spectra of 1( R) and 1( S) upon addition of EuIII not only allowed us to evaluate the values of the binding constants but the resulting recalculated spectra may also be used as fingerprints for assignment of the chiral self-assembly species formed in solution. The obtained monolayers were predominantly formed from EuL3 (≈85 %) with the minor species present in ≈15 % EuL2. [ABSTRACT FROM AUTHOR]

A series of enantiomeric 2,6-bis(1,2,3-triazol-4-yl)pyridines (btp)-containing ligands was synthesized by a one-pot two-step copper-catalyzed amine/alkyne click reaction. The EuIII- and TbIII-directed self-assembly formation of these ligands was studied in CH3CN by monitoring their various photophysical properties, including their emerging circular dichroism and circularly polarized luminescence. The global analysis of the former enabled the determination of both the stoichiometry and the stability constants of the various chiral supramolecular species in solution. [ABSTRACT FROM AUTHOR]