Novel erbium(III) fluorinated b-diketonate complexes with N,N-donors for optoelectronics: from synthesis to solution-processed devices† Pablo Mart´ ın-Ramos, a Manuela Ramos Silva, * b Carmen Coya, c Carlos Zaldo, d ´ Angel Luis ´ Alvarez, c Susana ´ Alvarez-Garc´ ıa, d Ana M. Matos Beja b and Jes´ us Mart´ ın-Gil e Three novel ternary Er 3+ complexes emitting in the C band transmission window for fiber optic communications have been synthesised and their structures have been elucidated by single crystal X-ray diffraction. The fluorinated b-diketonate ligand, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, combines a good absorption cross-section in the ultraviolet region with reduction of non-radiative quenching of the Er 3+ emission, while the rigidity and bulkiness of the three different N,N-donors (2,2 0 -bipyridine, bathophenanthroline and 5-nitro-1,10-phenanthroline) have a pronounced impact on the emission intensity of luminescence. Furthermore, the choice of the ancillary ligand also determines the efficiency of the antenna effect, leading to complete quenching of the ligand-associated visible emission for the optimized complex with 5-nitro-1,10-phenanthroline. Solution processed 1.54 mm organic light-emitting diodes have been manufactured and characterized for this complex, confirming the aforementioned complete resonant energy transfer from the ligands to the Er 3+ ion. The features of the reported device fabrication show a simple way to obtain large area NIR-OLEDs. Introduction In recent years the research effort in luminescent lanthanide complexes with organic ligands has resulted in a great variety of materials for organic light-emitting diodes (OLEDs), 1 erbium doped ber ampliers (EDFAs) 2 and sensory technology. 3 The unique properties of lanthanide ions include narrow emission in the near infrared (NIR) range, large Stoke shis and long luminescence lifetimes, and arise from their [Xe]4f n electronic congurations with many spectroscopic terms and energy levels. Erbium ion (Er 3+ ) is of particular interest due to its emission in the C-band (1.53–1.565 mm) of the silica optical telecommunication window. Although f–f electronic transitions are forbidden by parity and spin rules, leading to very small absorption cross-sections and therefore low molar absorptivities, the lanthanide emission can be effectively sensitized via energy transfer from certain ligands used as “antennas” for ultraviolet-blue light. 4 The commonly accepted mechanism for such sensitization entails light absorption into the singlet state of the ligand, followed by population of the ligand triplet states via intersystem crossing (ISC), intramolecular energy transfer from the ligand triplet states to the emissive state(s) of the lanthanide, and nally characteristic light emission from the lanthanide. 5 Efficient ligand to lanthanide energy transfer requires a good overlap between the triplet level phosphorescence of the ligand and the ground state absorption of some energy levels of the considered lanthanide. The most favourable ligands for complexes with Eu 3+ – and to a lesser extent with Tb 3+ and Tm 3+ – have been widely studied in connection with their visible emissions; however, the optimum ligands for lanthanides with infrared emissions are less studied. 6 In particular, 1.5 mm emission of Er 3+ has been reported for different molecular systems (including macrocyclic ligands, acyclic ligands and heterometallic functional assemblies) 7 but it is still required to explore new Er 3+ complexes to optimize their NIR emissivity. b-Diketonates are amongst the sensitising ligands used. 8 Nevertheless, in contrast to their technological interest, the number of reliable NIR devices demonstrated is negligible. This is due to the fact that such organic ligands contain O–H and a Higher Technical School of Telecommunications Engineering, Universidad de Valladolid, Campus Miguel Delibes, Paseo Bel´ en 15, 47011 Valladolid, Spain. E-mail: pablo.martin.ramos@alumnos.uva.es; Tel: +34 983 252833 b 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 c Escuela Superior de Ciencias Experimentales y Tecnolog´ ıa (ESCET), Universidad Rey Juan Carlos, 28933 Madrid, Spain. E-mail: carmen.coya@urjc.es d Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana In´ es de la Cruz, 3, 28049 Madrid, Spain. E-mail: cezaldo@icmm.csic.es e 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 909018–909020. For crystallographic data in CIF or other electronic format. see DOI: 10.1039/c3tc00649b Cite this: DOI: 10.1039/c3tc00649b Received 16th November 2012 Accepted 18th February 2013 DOI: 10.1039/c3tc00649b www.rsc.org/MaterialsC This journal is ª The Royal Society of Chemistry 2013 J. Mater. Chem. 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