Christine L. Maupin

Porphyrin sensitization of circularly polarised near-IR lanthanide luminescence: enhanced emission with nucleic acid binding

A palladium porphyrin has been covalently linked to a chiral lanthanide complex and effectively sensitises near-IR emission from Nd and Yb; sensitisation is enhanced in the absence of oxygen and in the presence of a nucleic acid.

Ground and excited state chiroptical properties of enantiopure macrocyclic tetranaphthyl lanthanide complexes: controlled modulation of the frequency and polarisation of emitted light

Circular dichroism spectroscopy has revealed that strong exciton coupling occurs between adjacent pairs of 1-naphthyl chromophores in the chiral sodium, calcium and europium complexes of the macrocyclic tetraamide L1a/b. In constitutionally isomeric complexes involving a 2-naphthyl linkage, L2a/b, intramolecular excimer formation is observed by fluorescence emission spectroscopy as being strongest in the protonated ligand itself. The terbium and europium complexes show a well-defined circularly polarised luminescence that is independent of the nature of excitation: UV excitation at 300 nm via the proximate naphthyl antennae in [Tb.L1a]3+ and [Tb.L1b]3+ followed by intramolecular energy transfer results in mirror-image circularly polarised emission spectra. The lanthanide complex serves to modulate both the frequency and polarisation of the incident light in a controlled manner.

The measurement of circularly polarized luminescence from racemic lanthanide complexes prepared in sol-gels

Abstract Circularly polarized luminescence (CPL) has been measured from rigid sol-gels containing racemic D 3 complexes of Eu(III) with 2,6-pyridine-dicarboxylate (DPA) and oxydiacetate (ODA). These complexes occur in solution and sol-gels as racemic mixtures. CPL was generated from the racemic mixture by preparing a non-racemic excited state through circularly polarized excitation. The CPL measured from the sol-gel containing Eu(DPA) 3 3− is significantly less from that measured in solution. This result is interpreted in terms of the effects of concentration depolarization.

Analysis of the temperature dependence of the racemization of Eu(III) complexes through measurement of steady-state circularly polarized luminescence

Abstract The temperature dependence of the steady-state luminescence dissymmetry ratio, g lum , has been measured for racemic Eu(III) complexes containing the terdentate ligands dipicolinate and phenylethynyl-dipicolinate. As the temperature is increased, the magnitude of the dissymmetry ratio for these species decreases due to racemization occurring during the excited state lifetime. The temperature dependence of g lum is analyzed by a non-linear curve-fitting technique to determine the activation energies for the interconversion of the enantiomers. Comparison is made with previous measurements involving time-resolved circularly polarized luminescence.

Measurement and analysis of the temperature and pressure dependence of the 7F0→5D0 excitation spectra of Eu(III) complexes with 4-phenylethynyl-2,6-pyridine-dicarboxylic acid

Abstract The pressure and temperature dependence of the 5D0→7F0 transition of Eu(III) in complexes with 4-phenylethynyl-2,6-pyridinedicarboxylic acid has been measured at various metal to ligand ratios. The spectra have been fit to a sum of Lorentzian peaks, and the temperature dependence used to determine ΔH for the equilibrium reaction for formation of the tris complex from the bis complex. The pressure dependence of the 5D0→7F0 transitions corresponding to the bis and tris species is analyzed in order to determine the associated difference in volume, ΔV, between reactants and products.

Quantitative determination of Eu(III) complex speciation in aqueous complexes of Eu(III) with oxydiacetic acid using 5D0 → 7F0 excitation spectroscopy

Abstract In this work we report on the use of 7 F 0 → 5 D 0 excitation spectroscopy in determination of the concentration of the mono-, bis-, and tris-complexes of Eu(III) with the terdendate ligand oxydiacetic acid (ODA) for various metal/ligand ratios. For each of these complexes a separate resolvable excitation peak is observed. Each of the peaks can be fit to a normalized Lorentzian lineshape function, and a multiplicative factor may be determined that is proportional to the concentration. Comparison is made with results from conventional potentiometric measurements, and the potential for the use of this procedure in other systems is discussed.

Stereodifferentiation and base-pair selectivity in the binding of Δ and Λ cationic lanthanide complexes to [(CG)6]2, [(AT)6]2 and CT-DNA

Metal- and ligand-based luminescence, absorption and circular dichroism difference spectroscopy signal the extent and nature of binding of enantiopure Δ and Λ cationic lanthanide complexes to [(CG)6]2 and [(AT)6]2.

Synthesis, NMR, relaxometry and circularly polarised luminescence studies of macrocyclic monoamidetris(phosphinate) complexes bearing a remote chiral centre

Lanthanide complexes of macrocyclic monoamidetris(phosphinate) ligands are partially hydrated in aqueous solution. Introduction of a chiral centre into the amide group leads to the formation of only two non-interconverting complex diastereoisomers (2∶1 for α-phenylethyl and 4∶1 for α-1-naphthylethyl). Proton, 31P NMR and circularly polarised luminescence studies indicated that the configuration at the chiral carbon centre determines the helicity of the layout of the pendent arms and the macrocyclic ring conformation, with an RRR or SSS configuration preferred at the phosphorus centres.

Effect of pressure on the enantioselective quenching of the luminescence from rac-tris(2,6-pyridinecarboxylato)terbium(III) by resolved tris(1,10-phenanthroline)ruthenium(II)

The rate of the enantioselective quenching of the luminescence from rac-tris(2,6-pyridinecarboxylato)terbium(III) by resolved tris(1,10-phenanthroline)ruthenium(II) increases with pressure when the reaction is carried out in water, but decreases with pressure in methanol.