Reaction of NdIII and ErIII nitrate salts with a 1,3,5-tris­(dipicolylamine)-triazine (dpat) ligand yielded two unprecedented examples of [Ln­(NO3)6/5]3–/2– (Ln = Nd, Er) moieties completely encapsulated by the ligands. They are found in the two new complexes, [(H3 dpat)2]­[(Nd­(NO3)6)2]·2CH3CN (1), and the related [(H3 dpat)2]­[(Er­(NO3)5)3]·3CH3CN·2H2O (2). The structures of the complexes are similar and they crystallize in the triclinic P-1 space group with a = 12.1630(3), b = 12.2694(3), c = 17.6357(5) Å, V = 2611.10(12) Å3, and a = 14.3372(4), b = 17.1271(4), c = 25.2207(7) Å, V = 5934.7(3) Å3, respectively. Anion-π interactions, which are reported here for the first time for LnIII ion complexes, hydrogen bonding interactions and π–π stacking support the formation of the encapsulated species. Evidence of the protonated dpat ligand in 1 and 2 was found through isolation of (H2 dpat)­(NO3)2. Finally, the pH-dependent ability of the ligand to extract LaIII and nitrate ions from aqueous into toluene solution is demonstrated.

Nickel Superoxide Dismutase (NiSOD) and the A-cluster of Carbon Monoxide Dehydrogenase/Acetyl Coenzyme A Synthase (CODH/ACS) both feature active sites with Ni coordinated by thiolate and amide donors. It is likely that the particular set of donors is important in tuning the redox potential of the Ni center(s). We report herein an expansion of our efforts involving the use of 2,2′-dithiodibenzaldehyde (DTDB) as a synthon for metal-thiolate complexes to reactions with Ni complexes of N,N-dimethylethylenediamine (dmen). In the presence of coordinating counterions, these reactions result in monomeric square-planar complexes of the tridentate N2S donor ligand derived from the Schiff-base condensation of dmen and DTDB. In the absence of a coordinating counterion, we have isolated a Ni(II) complex with an asymmetric N2S2 donor set involving one amine and one imine N donor in addition to two thiolate donors. This latter complex is discussed with respect to its relevance to the active site of NiSOD.

Dipicolylamine-functionalized 1,3,5-triazine (dpat) was isolated. When reacted with LaCl 3 , compound [(LaCl 6 )(H 3 dpat)][H 2 O] 2 (1) formed, which crystallized in the monoclinic P2 1 /n space group with parameters a = 11.47 Å, b = 19.22 Å, c = 20.98 Å, V = 4652.02 Å, and β = 90.53°. When reacted with NdCl 3 , the complex [NdCl 3 (H 2 O) 4 (H 3 dpat)][Cl] 3 (MeOH) 2 (2) crystallized in the monoclinic P2 1 /n space group with unit cell parameters a = 20.05 Å, b = 12.81 Å, c = 20.64 Å, V = 5004.40 Å, and β = 110.20°.In both cases, the dpat ligand forms a bowl-shaped cavity that partially envelops the Ln III -containing central unit, which is anionic in 1 and neutral in 2. The formation of these outer-sphere complexes is supported by secondary interactions, including π−π stacking, hydrogen bonding, and anion−π between the chlorolanthanide-(III) fragment and the electron-deficient 1,3,5-triazine ring. Evidence of protonation of the pyridine rings in dpat was substantiated through the isolation of [H 2 dpat][Cl] 2 (3). This compound crystallized in the monoclinic C2/c space group with parameters a = 11.93 Å, b = 20.22 Å, c = 15.28 Å, V = 3664.97 Å, and β = 94.35°. Four pyridine rings are pairwise protonated in 3. dpat showed a moderate ability to extract La III from an aqueous to an organic phase, indicating its potential, through judicious manipulation of secondary-sphere interactions, as the starting point for efficient extractants for Ln III ions.

Two new complexes of Eu(III) and Tb(III) with the new ligand N,N ,N -(1,3,5-triazine-2,4,6-triyl)tribenzamide (TBZM) and benzoate (BA) have been isolated and crystallographically characterized. [Tb(BA) 2 (TBZM)(H 2 O)] 2 (CF 3 SO 3 ) 2 • 4CH 3 CN•2H 2 O, 1, crystallizes in the triclinic P-1 lattice with unit cell parameters a = 11.3018(8), b = 14.3390(5), c = 16.4758(5) Å, ␣ = 114.036(2) • , ␤ = 106.112(2) • , ␥ = 90.916(2) • and V = 233.40(14) Å3 . The related complex [Eu(BA) 2 (TBZM)(H 2 O)] 2 (NO 3 ) 2 •12.4H 2 O, 2, crystallizes in the triclinic P-1 lattice with unit cell parameters a = 12.2537(2), b = 13.0210(3), c = 15.7362(3) Å, ␣ = 71.083(1) • , ␤ = 80.628(1) • , ␥ = 80.910(1) • and V = 2328.55( 8) Å3 . Both complexes display the metal center with coordination number 8 in a square-antiprismatic geometry. Extensive hydrogen-bonding interactions, which extend the homobinuclear molecules into three-dimensional architectures, are present in both compounds. In the first case, triflate counter-ions, benzoate ligands and solvent water and acetonitrile molecules and, in the second case, the TBZM ligands, nitrate counter-ions and solvent water molecules are involved in these interactions. Finally, in the Eu(III) complex, the three-dimensional structure is further supported by π-π interactions involving benzamide phenyl rings and triazine rings.

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