RESUMO

A new class of lanthanide mixed-carboxylate ligands compounds with formula {[Ln2 (phthgly)4 (bdc)(H2 O)6 ]·(H2 O)4 }∞ , labelled as Ln3+ : Eu (1) and Gd (2) coordination polymers (CP) were synthesized under mild reaction conditions between lanthanide nitrate salts and a solution of N-phthaloylglycine (phthgly) and terephthalic (bdc) ligands. The (1) and (2) coordination polymers were formed by symmetric binuclear units, in which phthgly and bdc carboxylate ligands are coordinated to the lanthanide ions by different coordination modes. Surprisingly, all organic ligands participate in hydrogen bonding interactions, forming an extremally rigid crystalline structure. The red narrow emission bands from the 5 D0 →7 FJ transitions of the Eu3+ ion show a high colour purity. The intramolecular energy transfer process from L→Eu3+ ion has been discussed. The experimental intensity parameters (Ω2,4 ) reflect lower angular distortion and polarizability of the chemical environment around the metal ion compared with other Eu3+ compounds reported in the literature. This novel class of coordination polymer offers a more attractive platform for developing luminescent functional materials for different applications.

Assuntos

Elementos da Série dos Lantanídeos , Compostos Organometálicos , Ácidos Ftálicos , Elementos da Série dos Lantanídeos/química , Compostos Organometálicos/química , Polímeros/química , Modelos Moleculares , Cristalografia por Raios X , Ligantes , Ácidos Carboxílicos

RESUMO

Luminescent organic-inorganic hybrids containing lanthanides (Ln3+) have been prominent for applications such as luminescent bio-probes in biological assays. In this sense, a luminescent hybrid based on dense silica (SiO2) nanospheres decorated with Eu3+ ß-diketonate complexes using dibenzoylmethane (Hdbm) as a luminescent antenna was developed by using a hierarchical organization in four steps: (i) anchoring of 3-aminopropyltriethoxysilane (APTES) organosilane on the SiO2 surface, (ii) formation of a carboxylic acid ligand, (iii) coordination of Eu3+ to the carboxylate groups and (iv) coordination of dbm- to Eu3+. The hybrid structure was elucidated through the correlation of thermogravimetry, silicon nuclear magnetic resonance and photoluminescence. Results indicate that the carboxylic acid-Eu3+-dbm hybrid was formed on the surface of the particles with no detectable changes on their size or shape after all the four steps (average size of 32 ± 7 nm). A surface charge of -27.8 mV was achieved for the hybrid, assuring a stable suspension in aqueous media. The Eu3+ complex provides intense red luminescence, characteristic of Eu3+5D0→7FJ electronic transitions, with an intrinsic emission quantum yield of 38%, even in an aqueous suspension. Therefore, the correlation of luminescence, structure, particle morphology and fluorescence microscopy images make the hybrid promising for application in bioimaging.