From Mono- to Polynuclear Coordination Complexes with a 2,2′-Bipyrimidine-4,4′-dicarboxylate Ligand

Abstract

The coordination properties of the ligand 2,2′-bipyrimidine-4,4′-dicarboxylic acid (H2 bpd) with lanthanide­(III) ions (Ln = Eu, Tb, or Lu) were investigated. The syntheses of the H2 bpd ligand and its salts, [K2(bpd)­(H2O)2] (1) and [(AlkNH)­Lu­(bpd)2] (Alk = Et, Hex, or en), are described. In the presence of LnCl3 salts (Ln = Lu, Eu, or Tb), the formation of [Ln­(bpd)2]− and [Ln­(bpd)­(H2O) x ]+ species was assessed by 1H nuclear magnetic resonance (NMR), spectrophotometry, and spectrofluorometric titrations in aqueous solution. The solid state structure of 1, [K­(H2O)2]­[Lu­(bpd)2] (2), and [(Et3NH)­Lu­(bpd)2] (3) could be determined by X-ray diffraction, showing the ligand to act as a tetradentate unit with formation of three five-membered chelate rings around the central Ln­(III). With the aim of building polynuclear assemblies, the coordination between [Lu­(bdp)2]− and [Lu­(tta)3(H2O)] units (tta = thenoyltrifluoroacetylacetonate) was also investigated. In methanol, 1H NMR titration experiments revealed the formation of complex mixtures from which two new species could be identified, [Lu2(bpd)­(tta)4] (4) and H­[Lu­(bpd)­(tta)2] (5), as confirmed by their solid state structure analysis. Using highly lipophilic cations in chloroform, the octametallic complex [enH]4[Lu8(bpd)4(tta)18] (6) could be isolated and its X-ray structure determined.

Selective Complexation and Separation of Uranium(VI) from Thorium(IV) with New Tetradentate N,O-Hybrid Diamide Ligands: Synthesis, Extraction, Spectroscopy, and Crystallographic Studies

“…Synthesis. The specific synthetic procedures of Et-Tol-BPDA, 4,4′-dimethyl-2,2′-bipyrimidine, 30 and 2,2′-pyrimidine-4,4′-dicarboxylic acid 38 are described in the Supporting Information.…”

“…First, 2chloro-4-methyl pyrimidine (3) was converted to 4,4′dimethyl-2,2′-bipyrimidine (4) by the Tiecco coupling reaction, according to the reported literature. 30 Compound 4 was then oxidized with potassium permanganate at 90 °C, followed by treatment with hydrochloric acid to generate 2,2′bipyrimidine-4,4′-dicarboxylic acid (5) in a yield of 65%. 38 After refluxing dicarboxylic acid 5 with thionyl chloride in the presence of a catalytic amount of N,N-dimethylformamide for 3 h, the remaining diacyl chloride 6 was obtained by removing the excess thionyl chloride and solvent and then reacted with N-ethyl-p-toluidine and triethylamine in tetrahydrofuran to provide Et-Tol-BPymDA in a reasonable yield of 45%.…”

“…The past decade has witnessed a flourishing development of actinide/lanthanide complexation and separation by employing N,O-hybrid ligands based on rigid N-heterocyclic skeletons. − Shi et al reported a tetradentate N,O-hybrid ligand, N , N ′-diethyl- N , N ′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), with well-preorganized amide oxygen and nitrogen atoms, which exhibits good extraction ability and selectivity toward actinides over lanthanides . More recently, Zabierowski et al reported that 2,2′-bipyrimidine-4,4′-dicarboxylic acid could bind to lanthanides to form stable complexes, in which the pyrimidine nitrogen atoms and carboxylic oxygen atoms involved in coordination on the same molecule always lie approximately in the same plane.…”

“…The past decade has witnessed a flourishing development of actinide/lanthanide complexation and separation by employing N,O-hybrid ligands based on rigid N-heterocyclic skeletons. − Shi et al reported a tetradentate N,O-hybrid ligand, N , N ′-diethyl- N , N ′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), with well-preorganized amide oxygen and nitrogen atoms, which exhibits good extraction ability and selectivity toward actinides over lanthanides . More recently, Zabierowski et al reported that 2,2′-bipyrimidine-4,4′-dicarboxylic acid could bind to lanthanides to form stable complexes, in which the pyrimidine nitrogen atoms and carboxylic oxygen atoms involved in coordination on the same molecule always lie approximately in the same plane. It thus can be envisaged that this kind of N,O-hybrid ligand would show preferential coordination toward U­(VI) over Th­(IV) as the coordination of uranyl ions merely occurs in the equatorial plane, − while thorium ions always exhibit spherical coordination with a wide range of coordination numbers (5–12). , Until now, employing N,O-hybrid ligands for U­(VI)/Th­(IV) separation still remains a rarely explored territory .…”

Upconversion in a d–f [RuYb3] Supramolecular Assembly

“…Capitalizing on the success of CS of Tb by Yb in hetero-polynuclear clusters, , we hypothesized that hetero-polynuclear species comprising Yb complexes associated to a metal complex exhibiting an MLCT transition should be of interest to design new UC devices (Scheme c). Here, we report on the synthesis and characterization of [(Ru­(bpm) 3 )­(LnL 3 ) 3 ]­[BAr F 4 ] 2 hetero-tetranuclear d–f complexes (hereafter referred to as RuLn 3 ), in which three LnL 3 entities (Ln = Yb or Lu, L = ttfa = thenoyltrifluoroacetylacetonate) are linked to a Ru center by a bridging 2,2′-bipyrimidine (bpm) ligand , (Scheme ) using a weakly coordinating [BAr F 4 ] (tetrakis­(3,5- bis -(trifluoromethyl)­phenyl)­borate) anion. A full spectroscopic analysis of the up- and downshifting energy transfer processes is presented, revealing the first example of f → d upconverting molecular device in solution.…”