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Updated: Jun 18, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Cerium(IV)-lanthanide(III)-pyridine-2,6-dicarboxylic acid system: coordination salts, chains, and rings
1School of Chemistry, University of Hyderabad, Hyderabad-500 046, India.
Abstract:
A series of new heterometallic compounds containing cerium(IV) and lanthanide(III) with pyridine-2,6-dicarboxylic acid (dipicH(2)) have been synthesized. Depending on the Ln(III) ion and preparation conditions, we obtained four types of compounds. Type-I: one-dimensional coordination polymer, [Ln(dipicH)(H(2)O)(4)Ce(dipic)(3)].7H(2)O; Ln = La (1), Ce (2), or Pr (3). Type-II: ionic compound, [Ln(dipicH)(H(2)O)(6)][Ce(dipic)(3)].7H(2)O; Ln = Nd (4), Sm (5), Eu (6), Gd (7), or Dy (8). Type-III: octanuclear cluster incorporating a six-membered coordination ring, [Ln(H(2)O)(7)Ln(dipic)(H(2)O)(4)(Ce(dipic)(3))(2)](2).nH(2)O; Ln = La (9) n = 24, Ce (10) n = 24, Pr (11) n = 24, or Nd (12) n = 26. Type-IV: hexanuclear cluster incorporating a four-membered coordination ring, [(Ln(H(2)O)(5))(2)(Ce(dipic)(3))(4)(2H(+))].nH(2)O; Ln = Nd (13) n = 34, Sm (14) n = 26, Eu (15) n = 26, or Gd (16) n = 26. Crystal structures were determined for compounds 1-16. Tb and heavier lanthanides all form compounds isomorphous with Type-IV compounds. The observed structural variety is a consequence of the interplay of lanthanide contraction and kinetic effects involving water molecules, free as well as clusters, ranging in size from 6 to 26. A metal-centered luminescence sensitized by dipic ligand was observed in compounds containing Eu(III) and Dy(III) ions. Direct chelation, as opposed to bridging coordination, leads to enhanced luminescence. Resolved EPR spectra were observed for the Gd(III) compounds which are dependent on the coordination environment.
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