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Artigo em Inglês | MEDLINE | ID: mdl-32558120


A nanoring-rotaxane supramolecular assembly with a Cy7 cyanine dye (hexamethylindotricarbocyanine) threaded along the axis of the nanoring was synthesized as a model for the energy transfer between the light-harvesting complex LH1 and the reaction center in purple bacteria photosynthesis. The complex displays efficient energy transfer from the central cyanine dye to the surrounding zinc porphyrin nanoring. We present a theoretical model that reproduces the absorption spectrum of the nanoring and quantifies the excitonic coupling between the nanoring and the central dye, thereby explaining the efficient energy transfer and demonstrating similarity with structurally related natural light-harvesting systems.

Chem Sci ; 9(4): 1042-1049, 2018 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-29675151


The selective mitochondrial localisation of the Λ enantiomer of three different emissive europium(iii) complexes in NIH 3T3 and MCF7 cells contrasts with the behaviour of the Δ enantiomer, for which a predominant lysosomal localisation was observed by confocal microscopy. In each case, cell uptake occurs via macropinocytosis.

J Am Chem Soc ; 139(40): 14166-14172, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-28884581


Bleaney's long-standing theory of magnetic anisotropy has been employed with some success for many decades to explain paramagnetic NMR pseudocontact shifts, and has been the subject of many subsequent approximations. Here, we present a detailed experimental and theoretical investigation accounting for the anomalous solvent dependence of NMR shifts for a series of lanthanide(III) complexes, namely [LnL1] (Ln = Eu, Tb, Dy, Ho, Er, Tm, and Yb; L1: 1,4,7-tris[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane), taking into account the effect of subtle ligand flexibility on the electronic structure. We show that the anisotropy of the room temperature magnetic susceptibility tensor, which in turn affects the sign and magnitude of the pseudocontact chemical shift, is extremely sensitive to minimal structural changes in the first coordination sphere of L1. We show that DFT structural optimizations do not give accurate structural models, as assessed by the experimental chemical shifts, and thus we determine a magnetostructural correlation and employ this to evaluate the accurate solution structure for each [LnL1]. This approach allows us to explain the counterintuitive pseudocontact shift behavior, as well as a striking solvent dependence. These results have important consequences for the analysis and design of novel magnetic resonance shift and optical emission probes that are sensitive to the local solution environment and polarity.

Chem Commun (Camb) ; 52(91): 13349-13352, 2016 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-27786315


Chiral image contrast is demonstrated using enantiopure Eu(iii) complexes that emit right or left-handed circularly polarised light of opposite sign, at selected wavelengths.

Dalton Trans ; 43(15): 5721-30, 2014 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-24557335


The synthetic utility of europium complexes with three coordinated 4-bromopyridyl groups for chromophore elaboration has been assessed in palladium-catalysed Sonogashira coupling reactions, and in copper(i) mediated click reactions of the triazide derivative, generated in situ. The crystal structure of the Eu complex of a p-OMe-phenyl substituted triazole at 100 K is reported in which the pendant triazole sensitising moieties interdigitate in the solid-state lattice. The triazole complex can be separated into Δ and Λ enantiomers by chiral HPLC but is weakly emissive in methanol (ε 5.5 mM(-1) cm(-1); λexc 320 nm; ϕ 0.2%), contrasting with a set of four alkynyl-aryl derivatives which are one thousand times brighter and absorb strongly with broad absorption maxima in the range 332 to 360 nm. An enantiopure europium complex gives an intense CPL signal in solution that is the strongest yet reported.