Solid state structures and solution behaviour of tetranuclear lanthanide() carbonate-bridged coordination compounds of chiral 3 + 3 amine macrocycle

The linking of two dinuclear macrocyclic units of large triphenolic hexaazamine by two carbonate anions results in the formation of dimeric tetranuclear Sm( iii ), Eu( iii ) and Gd( iii ) complexes. These complexes were initially obtained serendipitously by fixation of atmospheric carbon dioxide and subsequently obtained in a rational way by the application of carbonate salts. The X-ray crystal structures of these isomorphic complexes show highly folded conformation of the macrocycle. This type of conformation is also confirmed by 2D NMR spectra of the Sm( iii ) complex. The ESI-MS and NMR spectra reveal also that these carbonate complexes exist in solution in two different forms that are in a concentration-dependent dynamic equilibrium. A family of complexes [Ln 4 (H L R ) 2 (CO 3 ) 2 (NO 3 ) 2 (H 2 O) 4 ](NO 3 ) 2 were prepared. The solid-state structures of these complexes were compared with their solution behaviour.