Novel erbium(III) complexes with 2,6-dimethyl-3,5- heptanedione and different N,N-donor ligands for ormosil and PMMA matrices doping† P. Mart´ ın-Ramos, a V. Lav´ ın, b M. Ramos Silva, * c I. R. Mart´ ın, b F. Lahoz, b P. Chamorro- Posada, a J. A. Paix~ ao c and J. Mart´ ın-Gil d Three novel complexes, [Er(dmh) 3 (bipy)], [Er(dmh) 3 bath] and [Er(dmh) 3 (5NO 2 phen)], with 2,6-dimethyl- 3,5-heptanedione (Hdmh) as the main sensitizer and either 2,2 0 -bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO 2 phen) as synergistic ligands were synthesized. Upon excitation at the maximum absorption of the ligands, the complexes show the characteristic near- infrared (NIR) luminescence of the Er 3+ ions, due to efficient energy transfer from the ligands to the central Er 3+ ion via the antenna effect. Single crystals were grown and their structures were determined showing different Er–N distances. The compound with shorter Er–N distances, [Er(dmh) 3 (5NO 2 phen)], was found to be the best light harvester and the best for transferring the energy to the lanthanide among the three studied compounds. Finally, the novel complexes have been assessed for their application in sol–gel and polymer-based waveguides and optical amplifiers through their inclusion into ormosil and polymethylmethacrylate matrices. The dispersion was successful in the bipy and 5NO 2 phen cases, with the properties of the hybrid materials mimicking those of the pure complexes. Introduction Innovation in optoelectronics is oen enabled by progress in materials science and technology based on NIR-emitting lanthanide (Ln 3+ ) ions. Among these NIR-emitting ions, Er 3+ plays a special role since it displays emission at 1.55 mm, essential for the requirements of in vivo imaging, 1 laser systems, 2 or in telecommunication industry, optical ampliers 3 and light emitting diodes. 4,5 Ln 3+ ions have relatively low absorptivities because their electronic transitions are spin forbidden and, consequently, direct excitations are rather inefficient. An interesting strategy to overcome this difficulty is to coordinate the Ln 3+ ion with light-harvesting organic ligands, which absorb light much more efficiently. Such ligands should transfer their energy to the lanthanide, which would then emit at a specic wavelength. In addition to this, the ligands also prevent water from entering the rst coordination sphere, since water molecules quench the luminescence of the lanthanides. Due to the strong absorption within a large wavelength range, b-diketones are one of the most popular ligands for lanthanide ions and, consequently, they have also been targeted as Er 3+ ion sensitizers so as to obtain efficient NIR-lumines- cence. Moreover, in order to effectively saturate the rst coor- dination sphere of the Er 3+ ion, which may quench the luminescence, ancillary ligands such as N,N-donor ligands, or synergic agents according to Rohatgi, 6 can be introduced in the complexes to be synthesized. Nonetheless, the aim of including these N,N-donors is not only to ensure the octacoordination around the ion, but also to extend the absorption spectra to the UV region. In this sense, N,N-donors have absorption spectra in the UV region which is essentially complementary to that of the b-diketonates, effectively sensitizing the complex over a wide wavelength range, 7 and enhancing the efficiency of the energy transfer from the ligands to the central Er 3+ ion. This results in an improvement in the emission intensity. 8 In addition to the weak absorptivity of lanthanide ions mentioned above, there are other issues that need to be taken into consideration regarding their practical applications: e.g., when embedded in crystalline solids, and in order to avoid any decrease in luminescence efficiency, a very good homogeneity of the crystal lattice is required, and therefore, a high temperature is necessary to synthesize homogeneous Ln 3+ -doped crystals. a Higher Technical School of Telecommunications Engineering, Universidad de Valladolid, Campus Miguel Delibes, Paseo Bel´ en 15, 47011, Valladolid, Spain. E-mail: pedcha@tel.uva.es; Tel: +34 983 185545 b MALTA Consolider Team and Department of Fundamental and Experimental Physics, Electronics and Systems, Universidad de La Laguna, E-38206 San Crist´ obal de La Laguna, Santa Cruz de Tenerife, Spain. E-mail: vlavin@ull.edu.es; Tel: +34 922 318321 c CEMDRX, Physics Department, Universidade de Coimbra, Rua Larga, P-3004-516, Coimbra, Portugal. E-mail: manuela@pollux.s.uc.pt; Fax: +351 239 829158; Tel: +351 239 410648 d Advanced Materials Laboratory, ETSIIAA, Universidad de Valladolid, Avenida de Madrid 44, 34004, Palencia, Spain. E-mail: mgil@iaf.uva.es; Tel: +34 979 108347 † CCDC 933414–933416. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c3tc30686k Cite this: J. Mater. Chem. C, 2013, 1, 5701 Received 12th April 2013 Accepted 14th July 2013 DOI: 10.1039/c3tc30686k www.rsc.org/MaterialsC This journal is ª The Royal Society of Chemistry 2013 J. Mater. Chem. C, 2013, 1, 5701–5710 | 5701 Journal of Materials Chemistry C PAPER Published on 16 July 2013. Downloaded by UNIVERSIDAD DE LA LAGUNA on 20/09/2013 15:12:50. View Article Online View Journal | View Issue