Structure and Magnetic Properties of Two Lanthanide 1,4‐Phenylenediacetate Compounds

The reactions of Ln (NO 3 ) 3 with 1,4‐phenylenediacetic acid (H 2 PDA) under hydrothermal conditions produced two isostructural lanthanide coordination polymers with the empirical formula [ Ln 2 (PDA) 3 (H 2 O)] · 2H 2 O [ Ln = Nd ( 1 ), Sm ( 2 )]. Single‐crystal X‐ray diffraction analyses revealed that both contain one‐dimensionalmetal carboxylato chains, which are further connected by the–CH 2 C 6 H 4 CH 2 – spacers of PDA 2– ligands to yield a three‐dimensional metal‐organic framework. Magnetic susceptibilities of 1 and 2 were measured. The experimental χ m T value of both compounds decreases continuously with decreasing temperature over the whole temperature range. The best least‐squares fit of the experimental data of 1 to a theoretical equation in the temperature range of 70–300 K gives the zero‐field splitting parameter Δ = 2.21 cm –1 and the magnetic interaction between the Nd III ions 2 zJ ′ = –1.97 cm –1 , which indicates the presence of antiferromagnetic interaction between the Nd III ions. The experimental χ m T value of 2 at 2 K is much smaller than the expected value for two free Sm III ions ( 6 H 5/2 , g = 2/7) in the ground state, indicating that an antiferromagnetic interaction possibly exists between Sm III ions at low temperature. Fitting the magnetic data of 2 above 110 K based on an equation deduced from the Sm III ion in a monomeric system with free‐ion approximation gave a spin‐orbit coupling parameter λ = 192(2) cm –1