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1.
Inorg Chem ; 56(5): 2742-2749, 2017 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-28211688

RESUMO

In this Article, we report the self-assembly of lanthanide complexes formed with two new tripodal ligands, L2 and L3, where binding strands are connected to a rigid triptycene anchor. The pyridine moieties are functionalized with methoxy and PEG groups to enhance ligand solubility and to evaluate the effect of these substituents on lanthanide coordination. These ligands were successfully synthesized and characterized, and their coordination properties were examined along the lanthanide series through speciation studies with NMR and ESI-MS. Well-defined tetranuclear complexes are formed with both ligands, but their stabilities with heavier lanthanides are considerably reduced, especially for complexes with L3. This is attributed to a destabilizing effect of pending PEG arms in combination with increased steric hindrance between binding strands upon complexation with smaller cations. The sensitization of lanthanide luminescence in tetranuclear complexes occurs despite one water molecule being coordinated to a metal ion.

2.
Inorg Chem ; 53(24): 12848-58, 2014 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-25415587

RESUMO

Tyrosinase (Ty) is a copper-containing enzyme widely present in plants, bacteria, and humans, where it is involved in biosynthesis of melanin-type pigments. Development of Ty inhibitors is an important approach to control the production and the accumulation of pigments in living systems. In this paper, we focused our interest in phenylthiourea (PTU) and phenylmethylene thiosemicarbazone (PTSC) recognized as inhibitors of tyrosinase by combining enzymatic studies and coordination chemistry methods. Both are efficient inhibitors of mushroom tyrosinase and they can be considered mainly as competitive inhibitors. Computational studies verify that PTSC and PTU inhibitors interact with the metal center of the active site. The KIC value of 0.93 µM confirms that PTSC is a much more efficient inhibitor than PTU, for which a KIC value of 58 µM was determined. The estimation of the binding free energies inhibitors/Ty confirms the high inhibitor efficiency of PTSC. Binding studies of PTSC along with PTU to a dinuclear copper(II) complex ([Cu2(µ-BPMP)(µ-OH)](ClO4)2 (1); H-BPMP = 2,6-bis-[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) known to be a structural and functional model for the tyrosinase catecholase activity, have been performed. Interactions of the compounds with the dicopper model complex 1 were followed by spectrophotometry and electrospray ionization (ESI). The molecular structure of 1-PTSC and 1-PTU adducts were determined by single-crystal X-ray diffraction analysis showing for both an unusual bridging binding mode on the dicopper center. These results reflect their adaptable binding mode in relation to the geometry and chelate size of the dicopper center.


Assuntos
Agaricus/enzimologia , Cobre/química , Inibidores Enzimáticos/química , Monofenol Mono-Oxigenase/antagonistas & inibidores , Feniltioureia/química , Tiossemicarbazonas/química , Agaricus/química , Agaricus/efeitos dos fármacos , Complexos de Coordenação/química , Complexos de Coordenação/metabolismo , Cobre/metabolismo , Cristalografia por Raios X , Inibidores Enzimáticos/farmacologia , Humanos , Levodopa/metabolismo , Modelos Moleculares , Monofenol Mono-Oxigenase/química , Monofenol Mono-Oxigenase/metabolismo , Oxirredução/efeitos dos fármacos , Feniltioureia/farmacologia , Tiossemicarbazonas/farmacologia
3.
Inorg Chem ; 50(18): 8926-36, 2011 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-21846119

RESUMO

The boron dipyrrin (Bodipy) chromophore was combined with either a free-base or a Zn porphyrin moiety (H(2)P and ZnP respectively), via an easy synthesis involving a cyanuric chloride bridging unit, yielding dyads Bodipy-H(2)P (4) and Bodipy-ZnP (5). The photophysical properties of Bodipy-H(2)P (4) and Bodipy-ZnP (5) were investigated by UV-Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. The comparison of the absorption spectra and cyclic voltammograms of dyads Bodipy-H(2)P (4) and Bodipy-ZnP (5) with those of their model compounds Bodipy, H(2)P, and ZnP shows that the spectroscopic and electrochemical properties of the constituent chromophores are essentially retained in the dyads indicating negligible interaction between them in the ground state. In addition, luminescence and transient absorption experiments show that excitation of the Bodipy unit in Bodipy-H(2)P (4) and Bodipy-ZnP (5) into its first singlet excited state results in rapid Bodipy to porphyrin energy transfer-k(4) = 2.9 × 10(10) s(-1) and k(5) = 2.2 × 10(10) s(-1) for Bodipy-H(2)P (4) and Bodipy-ZnP (5), respectively-generating the first porphyrin-based singlet excited state. The porphyrin-based singlet excited states give rise to fluorescence or undergo intersystem crossing to the corresponding triplet excited states. The title complexes could also be used as precursors for further substitution on the third chlorine atom on the cyanuric acid moiety.


Assuntos
Compostos de Boro/química , Porfirinas/química , Compostos de Boro/síntese química , Técnicas Eletroquímicas , Transferência de Energia , Modelos Moleculares , Porfirinas/síntese química , Análise Espectral
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