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

Abstract

Alkaline‐earth (AE)/cerium(III)‐based heterometallic coordination compounds of the biologically important ligand dipicolinic acid (dipicH2), namely [Mg(H2O)6]2[Ce(dipic)3][Ce(dipic)2(H2O)3]·2H2O (1), [Ca3(H2O)12Ce2(dipic)6]·6H2O (2), [Sr3(H2O)16Ce2(dipic)6]·4H2O (3) and [Ba2(H2O)7Ce(dipic)3NO3]·H2O (4), have been obtained by the reduction of an aqueous solution of (NH4)2Ce(NO3)6·6H2O in the presence of dipicH2 and alkaline‐earth oxides or carbonates. This series demonstrates the role of AE ions in controlling the topology of coordination networks based on the [Ce(dipic)3]3– anion. Compound 1 is a zero‐dimensional ionic compound, the crystal structure of compound 2 is based on a mixed four‐connected 3D network, compound 3 presents ladder‐shaped chains running along a crystallographic axis, and layers of squeezed CeBa6 pentagonal pyramids interconnected by nitrates generate a mixed five‐ and six‐connected network in 4. A thermal analysis showed that all four compounds exhibit reversible water‐uptake capacity and the basic nature of the frameworks could be intact up to at least 120 °C.

Ce(III)‐Based Coordination‐Complex‐Based Efficient Radical Scavenger for Exceptional Durability Enhancement of Polymer Application in Proton‐Exchange Membrane Fuel Cells and Organic Photovoltaics

“…First, the coordination complex [Ca 3 (H 2 O) 12 Ce 2 (dipic) 6 ]·6H 2 O ( 1 ), with a Ce 3+ is surrounded by three dipicolinate ligands containing [Ce(dipic) 3 ] 3− (dipicH 2 = dipicolinic acid) moiety, was synthesized according to the previous literature. [ 8 ] The dipicolinate ligand, a common pincer‐type ligand, contains two carboxylic acid groups with a pyridine group in the middle which can be an excellent linker for the coordination networks. For comparison, a coordination complex containing bidentate picolinate ligands, Na 2 [Ce(pic) 5 ]·picH·4H 2 O ( 2 ), with a Ce 3+ is surrounded by five picolinate ligands containing [Ce(pic) 5 ] 2− (picH = picolinic acid), was also prepared.…”

“…Initial geometries were obtained from their corresponding X‐ray crystal structures reported in the literature. [ 8,9 ] The structures were optimized at the same level of theory (6‐31 G(d,p)), and the optimized structures are shown in Figure a.…”

“…[ 12 ] For compounds 1 and 2 , monomeric cerium moieties of [Ce(dipic) 3 ] 3− and [Ce(pic) 5 ] 2− were selected for calculation, and the initial geometry for structure optimization was taken from the reported crystal structure. [ 8,9 ] The Ce 4+/3+ redox potentials for Ce complexes 1 , 2 , 3 , and ceric ammonium nitrate (CAN, [Ce(NO 3 ) 6 ] 2− ) were calculated against ferrocene (Fc + /Fc). [ 12 ] The calculated redox potentials ( E Ce 4+/3+ , Figure 1d) for 1 , 2, and 3 were −0.232, −0.002, and 0.54 V Fc+/Fc , respectively, which were lower than that of CAN (1.344 V Fc+/Fc ).…”

“…Ce Complex 1: The synthetic procedure was adopted from the previous literature. [8] In an aqueous solution containing Ce(NO 3 ) 3 •6H 2 O (0.868 g, 2 mmol), a methanolic suspension of dipicH 2 (1 g, 6.0 mmol) was added slowly. The solution was stirred for 10 min, and the pH was adjusted to 6-7 by the slow addition of CaO powder, and the mixture was furtherly stirred for 15 min at 80 C. Yellow precipitation was filtered through a glass frit and the yellow powder was dissolved in excess hot water.…”

Spherical octanuclear clusters in a Na–Ln–dipic system – encapsulation of a nitrate ion and incorporation of water nonamers and dodecamers

“…Compound 1 could be prepared also by starting with ammonium ceric nitrate and using vanadyl acetylacetonate or sodium sulphite as a reducing agent in a manner analogous to the previously reported preparation of alkaline earth/CeIJIII) complexes. 7 The nitrate-free cluster was obtained using this method by reducing ammonium ceric sulphate in the presence of dipicolinic acid. All crystals had a hexagonal block morphology reflecting the underlying trigonal symmetry.…”