Exploring the Spatial Arrangement of Simple 18-Membered Hexaazatetraamine Macrocyclic Ligands in Their Metal Complexes.

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)]OAc·7HO·EtOH and [DyL(Cl)]Cl·2HO, where L and L are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their moieties. [DyL(OAc)]OAc·7HO·EtOH represents the first crystallographically characterized lanthanoid complex of L, while [DyL(Cl)]Cl·2HO contributes to increasing the scarce number of Ln compounds containing L. Furthermore, the crystal structure of L·12HO was solved, and it was compared with those of other related macrocycles previously published. Likewise, the crystal structures of the Dy complexes were compared with those of the lanthanoid and -metal complexes of other 18-membered donor macrocycles. This comparison showed some effect of the spacers employed, as well as the influence of the size of the ancillary ligands and the metal ion. Additionally, the distinct folding behaviors of these macrocycles influenced their coordination geometries. Moreover, the luminescent properties of [DyL(OAc)]OAc·7HO·EtOH and [DyL(Cl)]Cl·2HO were also investigated, showing that both complexes are fluorescent, with the emission being sensitized by the ligands.