pubs.acs.org/cm Published on Web 10/16/2009 r 2009 American Chemical Society Chem. Mater. 2009, 21, 5099–5111 5099 DOI:10.1021/cm901901j Ligand-Assisted Rational Design and Supramolecular Tectonics toward Highly Luminescent Eu 3þ -Containing Organic-Inorganic Hybrids Patrı´cia P. Lima, † Filipe A. Almeida Paz, ‡ Rute A. S. Ferreira, † V. de Zea Bermudez, § and Luı´s D. Carlos* ,† † Departamento de Fı´sica and ‡ Departamento de Quı´mica, Universidade de Aveiro CICECO, 3810-193 Aveiro, Portugal, and § Departamento de Quı´mica and CQ-VR, Universidade de Tr  as-os Montes e Alto Douro, 5001-801 Vila Real, Portugal Received June 30, 2009. Revised Manuscript Received September 4, 2009 The ligands-assisted rational design of a Eu 3þ -containing organic-inorganic hybrid (di-ureasil) displaying the highest emission quantum yield (0.60 ( 0.06) reported so far is introduced. Two new lanthanide complexes were synthesized in which the metal (Eu 3þ or Gd 3þ ) first coordination sphere is formed by three β-diketonate ligands (btfa is the 4,4,4-trifluoro-l-phenyl-1,3-butanedionate ion) and two methanol (MeOH) molecules. The complexes also comprise the bpeta (1,2-bis(4-pyridyl)ethane) ligand. The Eu 3þ complex crystal structure, determined by single crystal X-ray diffraction, confirms the hydrogen bonding ability, the high conformational flexibility and the versatile binding mode of the N, N 0 -bidentate bpeta in the architecture of the crystals. The bpeta spacers act as bridges, promoting the formation of supramolecular dimeric [Eu(btfa) 3 (MeOH) 2 ] 2 bpeta 2 species via the establishment of highly directional and strong hydrogen-bonds between the bpeta N atoms and the OH groups of the MeOH molecules. The synthesis of the Eu 3þ -doped di-ureasils is an efficient three-step concerted process that results in the destruction of the bpeta-driven self-assembled dimeric units and the formation of a new complex in which the di-ureasil structure plays the role of ligand: (i) one or two labile MeOH molecules are released from the ion local environment and replaced by the oxygen atoms of the carbonyl groups of the urea cross-links; (ii) an increase in the degree of order of the poly(oxyethylene) (POE) chains occurs concomitantly; (iii) the bpeta ligand remains in the neighborhood of the newly formed Eu 3þ complex. The synergy between the absorption ability of the btfa and bpeta cromophores and the hybrid’s emitting centers creates additional and efficient bpeta-to-hybrid and bpeta-to-btfa transfer channels that optimize the metal sensitization process contributing for the large measured emission quantum yield. Introduction Over the past decade the interest in lanthanide-contain- ing organic-inorganic hybrids has grown considerably with the concomitant fabrication of materials with tun- able attributes and offering modulated properties. The potential of these materials relies on the possibility of fully exploiting the synergy between the intrinsic characteris- tics of sol-gel derived hosts (e.g., highly controlled purity, easy shaping and patterning, easy control of the refractive index, excellent optical quality, photosensitiv- ity, encapsulation of large amounts of emitting centers isolated from each other and protected by the host), and the luminescence features of trivalent lanthanide ions (Ln 3þ ) (e.g., high emission quantum yield, narrow band- width and long-lived emission, large Stokes shifts, li- gand-dependent luminescence sensitization). Promising applications may be envisaged, such as light-emitting devices, active waveguides in the visible (vis) and near IR (NIR) spectral regions, active coatings, and bio- medical actuators and sensors, opening up exciting direc- tions in materials science and related technologies with significant implications in the integration, miniaturiza- tion, and multifunctionalization of devices. 1-5 The research activity in this field has been essentially focused on amorphous organic-inorganic siloxane- based hybrids, either incorporating added lanthanide compounds (ionic salts 6-8 or organic complexes 9-14 ) or formed through the covalent attachment bonding *Corresponding author. Tel: þ351-234-370946. Fax: þ351-234-378197. E-mail: lcarlos@ua.pt. (1) Carlos, L. D.; Ferreira, R. A. S.; de Zea Bermudez, V.; Ribeiro, S. J. L. Adv. Mater. 2009, 21, 509. (2) Escribano, P.; Julian-Lopez, B.; Planelles-Arago, J.; Cordoncillo, E.; Viana, B.; Sanchez, C. J. Mater. Chem. 2008, 18, 23. (3) Carlos, L. D.; Ferreira, R. A. S.; de Z. Bermudez, V. In Hybrid Materials; Kickelbick, G., Ed.; Wiley-VCH: Weinheim, Germany, 2007; pp. 337-400. (4) Sanchez, C.; Julian, B.; Belleville, P.; Popall, M. J. Mater. Chem. 2005, 15, 3559. (5) Sanchez, C.; Lebeau, B.; Chaput, F.; Boilot, J. P. Adv. Mater. 2003, 15, 1969. (6) Carlos, L. D.; Ferreira, R. A. S.; de Zea Bermudez, V.; Molina, C.; Bueno, L. A.; Ribeiro, S. J. L. Phys. Rev. B 1999, 60, 10042. (7) Carlos, L. D.; Messaddeq, Y.; Brito, H. F.; Ferreira, R. A. S.; Bermudez, V. D.; Ribeiro, S. J. L. Adv. Mater. 2000, 12, 594. (8) Ferreira, R. A. S.; Carlos, L. D.; Goncalves, R. R.; Ribeiro, S. J. L.; de Zea Bermudez, V. Chem. Mater. 2001, 13, 2991. (9) Binnemans, K. In Handbook on the Physics and Chemistry of Rare Earths; Gschneidner, Jr., K. A., Bunzli, J. C. G., Pecharsky, V. K., Eds.; Elsevier: Amsterdam, 2005; Vol. 35, Chapter 225, pp. 107-272. (10) Lima, P. P.; Ferreira, R. A. S.; Freire, R. O.; Paz, F. A. A.; Fu, L.; J unior, S. A.; Carlos, L. D.; Malta, O. L. ChemPhysChem 2006, 7, 735.