title: Step by Step Assembly of Polynuclear Lanthanide Complexes with a Phosphonated Bipyridine Ligand.
abstract: The synthesis of the octadentate ligand L (LH8= ((([2,2'-bipyridine]-6,6'-diylbis(methylene))bis(azanetriyl))tetrakis(methylene))tetrakis(phosphonic acid)) is reported. The coordination of L with various lanthanide cations was monitored by absorption and luminescence spectrophotometric titration experiments (Ln = Tb, Yb), potentiometry (Ln = La, Eu, Lu), and mass spectrometry (Ln = Tb). It was found that L forms very stable mononuclear (LnL) species in aqueous solutions (log K = 19.80(5), 19.5(2), and 19.56(5) for La, Eu, and Lu, respectively) with no particular trend along the series. Spectroscopic data showed the Ln cations to be enclosed in the cavity formed by the octadentate ligand, thereby shielding the metal from interactions with water molecules in the first coordination sphere. When more than one equivalent of cations is added, the formation of polynuclear [(LnL)2Lnx] complexes (x = 1-3) can be observed, the presence of which could be confirmed by electrospray and MALDI mass spectrometry experiments. DFT modeling of the mononuclear (LnL) complexes indicated that the coordination of the cation in the cavity of the ligand results in a very asymmetric charge distribution, with a region of small negative electrostatic potential on the hemisphere composed of the chromophoric bipyridyl moiety and an electron-rich domain at the opposite hemisphere around the four phosphonate functions. DFT further showed that this polarization is most likely at the origin of the strong interactions between the (LnL) complexes and the incoming additional cations, leading to the formation of the polynuclear species.1H and31P NMR were used to probe the possible exchange of the lanthanide complexed in the cavity of the ligand in D2O, revealing no detectable exchange after 4 weeks at 80 °C and neutral pD, therefore pointing out an excellent kinetic inertness.
authors.affiliation: Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, Institut Pluridisciplinaire Hubert Curien (IPHC, UMR 7178), CNRS-Université de Strasbourg,, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex, France.|Laboratoire d'électrochimie des Matériaux Moléculaires et des Complexes, LEMMC, Faculté de Technologie, Université de Sétif-1 , Sétif, Algeria.
authors.forename: Nabila
authors.initials: N
authors.lastname: Souri
authors.affiliation: Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, Institut Pluridisciplinaire Hubert Curien (IPHC, UMR 7178), CNRS-Université de Strasbourg,, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex, France.
authors.forename: Pingping
authors.initials: P
authors.lastname: Tian
authors.affiliation: Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, Institut Pluridisciplinaire Hubert Curien (IPHC, UMR 7178), CNRS-Université de Strasbourg,, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Lecointre
authors.affiliation: Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, Institut Pluridisciplinaire Hubert Curien (IPHC, UMR 7178), CNRS-Université de Strasbourg,, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex, France.
authors.forename: Zoé
authors.initials: Z
authors.lastname: Lemaire
authors.affiliation: Laboratoire d'électrochimie des Matériaux Moléculaires et des Complexes, LEMMC, Faculté de Technologie, Université de Sétif-1 , Sétif, Algeria.
authors.forename: Salah
authors.initials: S
authors.lastname: Chafaa
authors.affiliation: Laboratoire de Spectrométrie de Masse Bio-Organique, IPHC, UMR 7178, CNRS-Université de Strasbourg, ECPM , 25, rue Becquerel, 67087 Strasbourg, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Strub
authors.affiliation: Laboratoire de Spectrométrie de Masse Bio-Organique, IPHC, UMR 7178, CNRS-Université de Strasbourg, ECPM , 25, rue Becquerel, 67087 Strasbourg, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Cianférani
authors.affiliation: Laboratoire de Chimie Bioorganique et Médicinale, UMR 7509, CNRS-Université de Strasbourg, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex 02, France.
authors.forename: Mourad
authors.initials: M
authors.lastname: Elhabiri
authors.affiliation: Universidade da Coruña , Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química Fundamental, Facultade de Ciencias, 15071 A Coruña, Galicia, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.affiliation: Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, Institut Pluridisciplinaire Hubert Curien (IPHC, UMR 7178), CNRS-Université de Strasbourg,, ECPM , 25, rue Becquerel, 67087 Strasbourg Cedex, France.
authors.forename: Loïc J
authors.identifier: http://orcid.org/0000-0003-0328-9842
authors.initials: LJ
authors.lastname: Charbonnière