Spectroscopic study of Tb3+(beta-diketonate)3: alpha-cyclodextrin inclusion compounds in aqueous solution

Abstract

Neste trabalho descrevemos a síntese de β-dicetonatos de Tb 3+ e o aumento de sua solubilidade em água através da formação de compostos de inclusão em α-ciclodextrina (α-CD). Os complexos [Tb(ppa) 3 (H 2 O) 2 ] e [Tb(ppa) 3 (phen)] (ppa=3-fenil-2,4-pentanodiona; phen = fenantrolina) foram sintetizados, caracterizados e a seguir incluídos em α-ciclodextrina. A inclusão foi confirmada por 1 H NMR e a estequiometria de associação determinada pelo método de Job. Nos espectros de excitação, os comprimentos de onda dos máximos de intensidade dos compostos de inclusão em solução aquosa [Tb(ppa) 3 (H 2 O) 2 ]:α-CD e [Tb(ppa) 3 (phen)]:α-CD apresentaram-se deslocados em 15 e 60 nm, respectivamente, com relação aos comprimentos de onda dos máximos dos complexos não incluídos. Nos espectros de emissão, as bandas características do Tb 3+ foram observadas mesmo após a inclusão dos compostos em α-CD. In this work we describe how the inclusion of Tb 3+ β-diketonate chelates into the hydrophobic cavity of α-cyclodextrin enhances the solubility of the complexes in aqueous medium and leads to changes in their photophysical properties. To this end, the complexes [Tb(ppa) 3 (H 2 O) 2 ] and [Tb(ppa) 3 (phen)] (ppa=3-phenyl-2,4-pentanedione; phen = phenantroline) were synthesized and characterized, and they were then included into α-cyclodextrin pockets. This inclusion was confirmed by 1 H NMR spectroscopy and the stoichiometry was determined by means of the Job method. In the excitation spectra, the maximum intensity wavelength of the inclusion compounds [Tb(ppa) 3 (H 2 O) 2 ]: α-CD and [Tb(ppa) 3 (phen)]:α-CD were displaced 15 and 60 nm respectively when compared with the non-CD starting complexes. The typical Tb 3+ emission bands were maintained after inclusion of the complexes into α-CD and their subsequent solubilization in aqueous medium.

Structure, Thermal Properties and Photoluminescence of Terbium and Dysprosium Mixed‐Ligand Complexes with Dimethyl‐N‐Trichloroacetylamidophosphate and 2,2’‐Bipyridine

“…The emission lifetime was measured by monitoring the most intense terbium transition 5 D 4 → 7 F 5 and was found to be equal to 2.0–2.2 ms, depending on the excitation wavelength (320 and 290 nm, respectively). The obtained values are among the highest values known for mixed‐ligand CAPh‐based tris ‐complexes [17,28,39] and significantly higher compared to mixed‐ligand terbium complexes with β‐diketones [40–42] . This could be due to reduced high energy vibrations in the chelating fragment of the CAPh compared to β‐diketones.…”

“…The obtained values are among the highest values known for mixed-ligand CAPh-based triscomplexes [17,28,39] and significantly higher compared to mixedligand terbium complexes with β-diketones. [40][41][42] This could be due to reduced high energy vibrations in the chelating fragment of the CAPh compared to β-diketones. The dependence of lanthanides luminescence lifetime upon excitation wavelength is a widespread phenomenon.…”

Formation of Aggregate-Free Gold Nanoparticles in the Cyclodextrin-Tetrachloroaurate System Follows Finke–Watzky Kinetics

“…The signal of the H 3 proton of α-cyclodextrin also shifted after the encapsulation of a terbium complex with an aromatic ligand. Its coordinated water did not appear in the NMR spectrum in D 2 O [54]. After the encapsulation of gold nanoclusters, the same H 3 proton became even more shielded than H 5 and H 6 [43].…”

Recent advances in lanthanide spectroscopy in Brazil

“…Other investigations on the luminescence properties of lanthanide-based systems with NPs, nanorods or systems assembled using sol-gel techniques have been reported in the literature [17,22,27,33,34,38,40,43,45,49,50,60,61,67,73,78,82,88,93,107,[127][128][129]133,136,140,142,143,149,163,[169][170][171]176,178,201,211,212,214,[235][236][237][238][239][240][241][242][243][244][245]…”