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A novel ligand design based on diketonate binding units is represented for the assembly of neutral tris- and quadruple-stranded dinuclear lanthanide complexes with interesting luminescent properties. The sensitizing properties of the ligands are investigated by luminescence spectroscopy.

The synthesis and characterization of near-infrared (NIR) emitting complexes of Nd(III), Er(III) and Yd(III) based on hexacoordinate lanthanide ions with an aryl functionalized imidodiphosphinate ligand, tpip, are described. The results indicate the effective shielding of the lanthanide by the twelve phenyl groups of the tpip ligands and the reduction of high-energy vibrations in close proximity to the lanthanide, which are the two important features in the design of NIR emitting lanthanide complexes.

The assembly of lanthanide and transition metal building blocks that lead to metallohairpins is introduced. Intercalating groups are present in the Ln- Pt2 metallohairpins that direct the complex to DNA recognition leading to considerable DNA stiffening with high LD values.

Lanthanide complexes based on bis(amides) of diethylenetriaminepentaacetic acid with thiol functionalities are modified with 2,2'-dipyridyl disulilde to give activated complexes that can selectively react with thiol-functionalized complexes to form heterometallic lanthanide macrocycles. The preparation and full characterization of the polyaminocarboxylate ligands N,N"-bis- [p-thiophenyl(aminocarbonyl)]diethylenetriamine-N,N',N"-triacetic acid (H3L") and the activated N,N"-bis[p-(pyridyldithio)- [phenyl(aminocarbonyl)] ]diethylenetriamine-N,N',N1'-triacetic acid (H3!]') and the complexes LaL", NdLX, SInLx, EULx, GdLX, Dy!]', ThLX, ErLX, and YbLX are reported. The luminescence properties of the LnL" complexes emitting in the visible (where Ln = Dy3+, .p3+ Eu3±, and Sm3+) are examined by steady-state and time-resolved photoluminescence, and the triplet state energy level of GdLX was estimated to be 24100 cm' from the 0-0 band of the 77K phosphorescence spectrum. Near-infrared emission was detected for the NdLX, YbLX and Er!]' complexes, demonstrating the versatility of the thiophenol chromophore. The assembly of purely heterometallic EuThLx2 macrocycles by reaction of Eu!] with ThL was followed by UV-vis absorption spectroscopy, monitoring the characteristic absorption peak of pyridyl-2-thione at 353 nm. Analysis of the solution by mass spectrometry reveals the formation of purely heterometallic macrocycle EuThLx2. This is in contrast with the results obtained by dynamic self-assembly under oxidative conditions, where we observe a statistical mixture of macrocyclic complexes of Eu2!]'2, Th2Lx2, and EuThLx2. The EuThLx2 macrocycle displays dual color emission, incorporating the characteristicf-f transitions of Eu3+ and Th3+. Investigation into the time-resolved photophysical properties of EuThLx2 reveals energy transfer from Tb3+ to Eu3+, facilitated by the different conformations of the macrocycle in solution. [ABSTRACT FROM AUTHOR]

In this paper we demonstrate that the effect of aromatic C--F substitution in ligands does not always abide by conventional wisdom for ligand design to enhance sensitisation for visible lanthanide emission, in contrast with NIR emission for which the same effect coupled with shell formation leads to unprecedented long luminescence lifetimes. We have chosen an imidodiphosphinate ligand, N-{P,P-di(pentafluorophinoyl)}-P,P-dipentafluorophenylphosphinimidic acid (HF20tpip), to form ideal fluorinated shells about all visible- and NIR-emitting lanthanides. The shell, formed by three ligands, comprises twelve fully fluorinated aryl sensitiser groups, yet no-high energy X--H vibrations that quench lanthanide emission. The synthesis, full characterisation including X-ray and NMR analysis as well as the photophysical properties of the emissive complexes [Ln(F20tpip)3], in which Ln=Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y, Gd, are reported. The photophysical results contrast previous studies, in which fluorination of alkyl chains tends to lead to more emissive lanthanide complexes for both visible and NIR emission. Analysis of the fluorescence properties of the HF20tpip and [Gd(F20tpip)3] reveals that there is a low-lying state at around 715 nm that is responsible for partially quenching of the signal of the visible emitting lanthanides and we attribute it to a pi-sigma* state. However, all visible emitting lanthanides have long lifetimes and unexpectedly the [Dy(F20tpip)3] complex shows a lifetime of 0.3 ms, indicating that the elimination of high-energy vibrations from the ligand framework is particularly favourable for Dy. The NIR emitting lanthanides show strong emission signals in powder and solution with unprecedented lifetimes. The luminescence lifetimes of [Nd(F20tpip)3], [Er(F20tpip)3] and [Yb(F20tpip)3] in deuteurated acetonitrile are 44, 741 and 1111 micros. The highest value observed for the [Yb(F20tpip)3] complex is more than half the value of the Yb ion radiative lifetime.

The potentially pentadentate ligand 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1:1 M:L complexes with labile metal ions, although [CuL1] and [NiL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1:2 complex [Co(L1)(HL1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1:2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cu(II) complex [Cu2L1(2)] forms, as well as a trinuclear Ni(II) complex [Ni(3)(L1)2(OAc)2(MeOH)2]. Moreover, in the presence of added H2dipic, the tetranuclear complex [Cu4(L1)2(dipic)2(OH2)2] is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand pi-stacking (inter-ring distances of 3.2-3.8 A) of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione (acac), each of the two pairs of adjacent monodentate ligands in [Ni3(L1)2(OAc)2(OH2)2] have been shown to be available for substitution without destroying the helical structure, to form [Ni3(L1)2(acac)2], also characterized by a crystal structure.