Cerium(IV)−Lanthanide(III)−Pyridine-2,6-dicarboxylic Acid System: Coordination Salts, Chains, and Rings

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.

Self‐Assembly of Hexanuclear Clusters of 4f and 5f Elements with Cation Specificity

“…Furthermore, the rare earth series offers the advantage of having exquisitely tunable ionic radii that enables sequential modifications in the properties of compounds derived from these elements. Examples of such tetravalent f element clusters include hexanuclear Ce IV carboxylates that can be used as oxidants in organic synthesis [13] and mixed Ce IV /Ln III clusters where both metal-based and ligand-based luminescence occur; [14] 5f element clusters are far more rare. However, dodecanuclear thorium clusters with a nitride core have [ been described.…”

Alkaline‐Earth (Mg–Ba) Coordination Networks Built Around the Tris(dipicolinato)cerate(3–) Ion: Highly Hydrated Networks That Survive Dehydration

“…The Sr-O bond lengths are in the range 2.27-2.28 (O dipic ) and 2.33-2.38 Å (O w ). In the case of the Ce IV -Sr-dipic system studied earlier, [5,7] two 1D polymers (single-and double-stranded) were formed that could be interconverted in solution. Due to serious disorder of the Sr2 atom as well as its coordinated water molecules, the Sr2-O distances are not accurate.…”

“…[1] The spores generally contain equimolar amounts of Ca 2+ and dipic 2-; the crystal structure of the resulting complex has been known [2] since 1968. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] We have previously reported coordination polymers formed by the alkaline-earth (AE) ions Ca, Sr and Ba with the [Ce IV (dipic) 3 ] 2ion. [3] The capacity of dipicH 2 to link various metal ions into coordination clusters, polymers and networks has also been probed to some extent.…”

“…Moreover, the diverse aspects of the coordination chemistry of dipicH 2 with regard to its chelating and bridging modes are by now well investigated. [4][5][6][7] In this study, we treated (NH 4 ) 2 Ce(NO 3 7 Ce-(dipic) 3 NO 3 ]·H 2 O (4). [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] We have previously reported coordination polymers formed by the alkaline-earth (AE) ions Ca, Sr and Ba with the [Ce IV (dipic) 3 ] 2ion.…”

Crystal structure of {(oxalato)-bis-[(pyridine-2,6-di-carboxylato)-diaqua)- indium(III)]}dihydrate: [In(C2O4)(C7H3N1O4)2(H2O)4]·2H2O, C16H18In2N2O18

“…Many complexes, constructed from oxalic acid or pyridine-2,6-dicarboxylic acid ligands with potential as functional materials in magnetism, catalysis and photo-luminescence, have been synthesized [4][5][6][7]. Af ew complexes containing mixed oxalate and pyridine-2,6-dicarboxylate ligands have also been reported [8].Inthese complexes the oxalate ligands were introduced in form of oxalic acid.…”