Coexistence of two magnetic sublattices in 2D transition metal nitroprussides, T(L)2[Fe(CN)5NO] with T = Mn, Co, Ni; L = 2-ethylimidazole, Imidazo[1,2-a]pyridine

Abstract

Transition metal nitroprussides form an interesting family of coordination polymers with 3D and 2D structural modifications. The 2D series has a Hofmann-like structure and can be formed from a large set of organic pillar molecules (L). This contribution reveals the coexistence of antiferromagnetic order within the inorganic layer T[Fe(CN)₅NO] of the titled 2D solids, and a weak ferromagnetic-like interaction between the paramagnetic metal centers (T) from adjacent layers, T-(L)₂-T. The latter interaction is possible through the π-π stacking and hydrogen bonding between pillar (L) molecules. SQUID magnetic data recorded for the titled solids are consistent with such a model of coexistence of two magnetic sublattices. IR and Raman spectra, as well as structural studies from powder XRD patterns, complemented the information derived from the magnetic measurements. The metal (T) polarizing power determines the charge subtraction from the molecular ring, favoring a stronger dipole-dipole coupling and more significantly π-π stacking. From the experimental data obtained, the regularities regarding the roles of both metal and pillars, as well as solid crystal structures, were rationalized.