Jean-Claude Bunzli - Lanthanide complexes with a calix[8]arene bearing phosphinoyl pendant arms

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  Puntus,L.N., Chauvin,A.S., Varbanov,S., Bunzli,J.C.G.   European Journal of Inorganic Chemistry  2007 (16) 2315-2326

  Abstract: The phosphinoyl-substituted   macrocyclic receptor B(8)bL(8), derived from   p-tert-butylcalix[8]arene, was synthesized and its structure was   studied in solution. According to temperature-dependent H-1 and   P-31 NMR spectroscopic data, the calix[8]arene adopts a so-called   in-out cone conformation. To investigate the influence of the   narrow rim substitution, interaction with trivalent lanthanide   ions, Ln(III) (Ln = La, Eu, Tb, Lu), was probed by MS, UV/Vis and   NNIR spectroscopic titrations. Although both 1:1 (in the presence   of triflate) and. 2:1 (in the presence of nitrate) Ln:B(8)bL(8)   complexes could be isolated in the solid state, the major species   present in methanol is the 1:1 complex, irrespective of the   anion. NNIR spectroscopic data point to a common conformation for   the 1:1 complexes in solution, the lanthanide ions being   coordinated by four of the eight phosphinoyl arms, with a   coordination sphere completed by methanol molecules or by nitrate   ions, as ascertained by IR and MS spectra. The ligand displays a   weak absorption at 360 nm that can be assigned to an intraligand   charge-transfer (ILCT) state, which is very sensitive to   coordination. Photophysical data of the Eu-III 2:1 complex point   to both metal ion sites providing a very similar chemical   environment for the lanthanide ions, with no coordinated water,   which is contrary to what is observed for the 1:1 complex. The   use of optical electronegativity to predict the energy of the   charge-transfer states in the lanthanide systems with   inequivalent ligands is discussed and extensive analysis of the   vibronic satellites of the Eu(D-5(0)-> F-J) transitions   ascertains conclusions drawn on the Eu-III coordination. ((c)   Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany,   2007)

  Address (URL): J INORG CHEM

 

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