title: A hexaaza macrocyclic ligand containing acetohydrazide pendants for Ln(III) complexation in aqueous solution. Solid-state and solution structures and DFT calculations.
abstract: Lanthanide complexes of a hexaaza macrocyclic ligand containing acetohydrazide pendants (L) have been synthesised (Ln = La-Er, except Pm), and structural studies have been carried out both in the solid state and in aqueous solution. Attempts to isolate the complexes of the heaviest Ln(iii) ions (Ln = Tm-Lu) were unsuccessful. The crystal structures of the ligand and its lanthanum complex have been determined by single-crystal X-ray crystallography. The X-ray crystal structure of [La(L)](3+) shows the metal ion being ten-coordinate, with the acetohydrazide pendants situated alternatively above and below the plane of the macrocycle. The two five membered chelate rings formed by the ethylenediamine moieties adopt (deltadelta) [or (lambdalambda)] conformations. The [Ln(L)](3+) complexes have been characterised by means of density-functional theory (DFT) calculations (B3LYP model). The structures obtained from these theoretical calculations are in very good agreement with the experimental solution structures, as obtained from paramagnetic NMR measurements on the Ce(iii), Pr(III), Nd(III) and Eu(III) complexes. The complexes adopt in aqueous solution a D(2) structure with the ligand adopting a (deltadelta) [or (lambdalambda)] conformation.
authors.affiliation: Departamento de Química Inorgánica, Facultade de Química, Universidade de Santiago de Compostela, Avda das Ciencias s/n., E-15782, Santiago de Compostela, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Núñez
authors.forename: Rufina
authors.initials: R
authors.lastname: Bastida
authors.forename: Alejandro
authors.initials: A
authors.lastname: Macías
authors.forename: Marta
authors.initials: M
authors.lastname: Mato-Iglesias
authors.forename: Carlos
authors.initials: C
authors.lastname: Platas-Iglesias
authors.forename: Laura
authors.initials: L
authors.lastname: Valencia
mesh_terms: D000465:Algorithms; D001386:Azides / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D047028:Macrocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D001386:Azides; D005029:Ethylenediamines; D028581:Lanthanoid Series Elements; D008024:Ligands; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D012996:Solutions; D014867:Water