Molecular structure and paramagnetic properties of Tris-diisobutyl- dithiophosphinate complexes of europium(III) with 2,2 0 -Bipyridyl in solution using NMR Sergey P. Babailov a,⇑ , Anna V. Goryunova a , Andrey V. Dudnikov b a A.V. Nikolaev’s Institute of Inorganic Chemistry of the Siberian Branch of the Russian Academy of Sciences, Av. Lavrentyev 3, Novosibirsk 630090, Russia b G.I. Budker’s Institute of Nuclear Physics, the Siberian Branch of the Russian Academy of Sciences, Av. Lavrentyev 3, Novosibirsk 630090, Russia highlights " Tris-diisobutyl-dithiophosphinate complexes of europium(III) with 2,2 0 -Bipyridyl are of great interest as promising luminescent sensors for biology and medicine. 1 H and 13 C NMR measurements are reported for the CDCl 3 solution of [Eu(2,2 0 -Bipy)(i-DBDTPh) 3 ] complex. The analysis of the structural parameters found by relaxation spectroscopy NMR testifies that the bipyridyl and i-DBDTPh anions are in the first coordination sphere of a Ln cation. The found experimental results indicate that the structure of these complexes in solution is similar to that one in the solid state (known from the X-ray crystal structure data). Paramagnetic complex investigated in the paper represents the new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution. article info Article history: Received 5 April 2012 Received in revised form 4 June 2012 Accepted 4 June 2012 Available online 23 June 2012 Keywords: Lanthanide-induced shifts Lanthanides Paramagnetic lanthanide complexes Relaxation spectroscopy of NMR Magnetic resonance thermometric sensors Luminescent sensors abstract Tris-diisobutyl-dithiophosphinate complexes of europium(III) with 2,2 0 -Bipyridyl are of great interest as promising luminescent sensors for biology and medicine. 1 H and 13 C NMR measurements are reported for the CDCl 3 solution of [Eu(2,2 0 -Bipy)(i-DBDTPh) 3 ] complex. The analysis of the structural parameters found by relaxation spectroscopy NMR testifies that the bipyridyl and i-DBDTPh anions are in the first coordination sphere of a Ln cation. The found experimental results indicate that the structure of these complexes in solution is similar to that one in the solid state (known from the X-ray crystal structure data). Paramagnetic complex investigated in the paper represents the new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Information about the molecular dynamics, structure and para- magnetic properties of the lanthanide coordination compounds is the basis of now existing technology to get preparation for photo- dynamic therapy, contrast reagents for medical magnetic reso- nance imaging (MRI), and sensors for biology and medicine. Nuclear magnetic resonance (NMR) establishes itself as a good method to get such information in solutions. In particular, NMR study of the lanthanide complexes at different temperatures lets one to detect the molecular dynamics and to determine the para- magnetic properties [1,2]. By NMR methods we have earlier stud- ied the molecular structure of paramagnetic bis-diisobutyl- dithiophosphinate (i-DBDTPh) lanthanide complexes with 1,10- phenanthroline ([Ln(1,10-Phen)(i-DBDTPh) 2 (NO 3 )]) in CDCl 3 solution (where Ln = Lu and Eu) [3]. But the temperature examin- ations have not been conducted, moreover, it has been done a small number of examinations for Eu complexes compared to the number of examinations done with the other lanthanide cations. Thus, it is of scientific interest to study the molecular structure and paramagnetic properties of the related [Ln(2,2 0 -Bipy) (i-DBDTPh) 3 ] complexes in CDCl 3 solution dependent on tempera- ture (where Ln = La and Eu). It is known that Fermi contact contributions to the lanthanide- induced chemical shifts (LISs) are proportional to 1/T (Curie’s law), and in the theoretical paper by Bleaney, it was predicted that the pseudocontact contributions to LIS should be proportional to 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2012.06.003 ⇑ Corresponding author. Tel.: +7 383 3308957; fax: +7 3832 3309489. E-mail address: babajlov@niic.nsc.ru (S.P. Babailov). Journal of Molecular Structure 1028 (2012) 107–109 Contents lists available at SciVerse ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc