Dalton Transactions PAPER Cite this: Dalton Trans., 2014, 43, 3121 Received 20th September 2013, Accepted 18th October 2013 DOI: 10.1039/c3dt52600c www.rsc.org/dalton Lanthanide complexes with aromatic o-phosphorylated ligands: synthesis, structure elucidation and photophysical properties† Sergey Shuvaev,* a Valentina Utochnikova, a Lukasz Marciniak, b Alexandra Freidzon, c Ilya Sinev, d Rik Van Deun, e Ricardo O. Freire, f Yan Zubavichus, g Wolfgang Grünert d and Natalia Kuzmina a Lanthanide complexes LnL 3 (Ln = Sm, Eu, Tb, Dy, Tm, Yb, Lu) with aromatic o-phosphorylated ligands (HL 1 and HL 2 ) have been synthesized and identified. Their molecular structure was proposed on the basis of a new complex approach, including DFT calculations, Sparkle/PM3 modelling, EXAFS spectroscopy and luminescent probing. The photophysical properties of all of the complexes were investigated in detail to obtain a deeper insight into the energy transfer processes. Introduction Up to now, a rich experience has been accumulated in the field of synthesis and design of luminescent lanthanide complexes. Meanwhile, the simultaneous adjustment of both the struc- tural and photophysical properties still seems to be of a great desire. One of the possible candidates on the role of such dua- listic ligands can be aromatic phosphine oxides. From the one hand, the tetrahedral co-ordination around a phosphorus atom provides the formation of three-dimensional structures, where PvO does not participate in the complexation, being just a structural junction. 1,2 The PvO bond can directly take part in complexation, either as a neutral monodentate O-donor ligand or as a chelating one by introducing an additional O-donor group in the β-position relatively to the phosphorus atom such as a hydroxyl group 3,4 or an ester substituent. 5 Moreover, bidentate imidodiphosphinates, con- taining two PvO groups, were also studied. 6,7 Therefore, both anionic and neutral ligands can be introduced into the co- ordination sphere. In the case of the lanthanide complexes a prosperous photophysical performance is tightly connected with the crystal structure of a complex. One of the main obstacles is the quenching of luminescence via vibrations of the solvent mole- cules in the inner sphere, which can be overcome by the satur- ation of the co-ordination polyhedron by ancillary ligands or by the introduction of bulky substituents, which effective shield the lanthanide ions from an external impact. Both of the ligands described in the present paper are suggested to promote dimeric or oligomeric complex for- mation instead of the mononuclear one, and they can be con- sidered as structural analogues of β-diketonates, forming binuclear complexes. 8,9 From another point of view, contrary to β-diketonates, o-phosphorylated phenols can be co-ordi- nated either in the form of chelating ligands (similarly to β-diketonates) or in the form of bridging ligands, 10 opening up wide possibilities in the construction of the co-ordination polyhedron. On the other hand, aromatic phosphine oxides are well- known sensitizers of terbium luminescence due to an appro- priate energy gap between their triplet state and the nearby resonance level 5 D 4 of terbium. 11–13 Thereby, aromatic o-phos- phorylated phenolates seem to be attractive and challenging anionic ligands from both photophysical and structural points of view. In present paper we describe the synthesis of several lantha- nide complexes LnL 3 (Ln = Sm, Eu, Gd, Tb, Dy, Tm, Yb, Lu) with o-phosphorylated phenols HL 1 and HL 2 (Fig. 1). We also † Electronic supplementary information (ESI) available. See DOI: 10.1039/c3dt52600c a Department of Materials Science, Lomonosov Moscow State University, 119991, Leninskie gory, 1/3, Moscow, Russia. E-mail: sergeyshuvaev@gmail.com; Tel: +7 495 9393836 b Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw, Poland c Photochemistry Center, Russian Academy of Sciences, ul. Novatorov 7a, Moscow 119421, Russia d Laboratory of Industrial Chemistry, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany e L 3 – Luminescent Lanthanide Lab, f-Element Coordination Chemistry, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 – building S3, B-9000 Gent, Belgium f Pople Computational Chemistry Laboratory, Department of Chemistry, UFS, 49100- 000 São Cristóvão-SE, Brazil g National Research Center “Kurchatov Institute”, 123182 Moscow, Russia This journal is © The Royal Society of Chemistry 2014 Dalton Trans. , 2014, 43, 3121–3136 | 3121 Published on 24 October 2013. Downloaded by Center of Photochemistry of the RAS on 06/04/2014 16:14:39. View Article Online View Journal | View Issue