Eighteen new lanthanide transition metal heterobimetallic compounds, Ln 2 Co(TeO 3 ) 2 (SO 4 ) 2 (Ln = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu) and Ln 2 Zn(TeO 3 ) 2 (SO 4 ) 2 (Ln = Sm, Gd, Dy, Ho, Er, or Yb), have been prepared. They crystallize in triclinic space group P1̅ with two different structural topologies occurring because of a reduction in the Ln 3+ coordination number from eight to seven with the smallest lanthanides, Yb 3+ and Lu 3+ . Magnetic susceptibility studies of compounds with diamagnetic lanthanides and lanthanide-like ions suggest that antiferromagnetic interactions occur between the Co 2+ ions. Similarly, the replacement of Co 2+ with Zn 2+ yields Ln 2 Zn(TeO 3 ) 2 (SO 4 ) 2 (Ln = Gd, Dy, Ho, or Er), and these materials allow for the resolution of the nature of the interactions between lanthanide ions. The data suggest that the short-range Ln 3+ ···Ln 3+ interactions are ferromagnetic. However, a wide range of ferroand antiferromagnetic interactions occur between the Ln 3+ and the Co 2+ cations, with several compounds exhibiting short-range magnetic correlations below 25 K. The results are discussed and contrasted with those recently reported for the related Ln 2 Cu-(TeO 3 ) 2 (SO 4 ) 2 family.
■ INTRODUCTIONHeterometallic coordination compounds, particularly those containing 3d/4f metals, have received an increased level of attention in recent years because of their potential applications in single-molecule magnets (SMMs), 1 ion exchange, 2 gas storage, 3 fluorescence, 4 and optical sensing. 5 The importance of mixed 3d/4f materials is exemplified by their extraordinary magnetic properties as shown by the strongest permanent magnets known, SmCo 5 and Nd 2 Fe 14 B. These latter materials combine the anisotropy of certain lanthanide ions with the itinerant ferromagnetism of transition metals. 6 The introduction of different spin carriers within the same structure type can lead to a vast array of magnetic interactions in heterobimetallic compounds. 7 The diversity of coordination environments exhibited by lanthanides allows a different arrangement between the metal ions, resulting in a variety of magnetic exchange pathways. 8 Orthogonal magnetic orbitals of two different spin carriers can more readily lead to ferromagnetic interactions than in homometallic systems. 9 In addition, a large number of 3d/4f heteronuclear clusters have been reported with magnetic properties that differ greatly from those of homometallic materials. 10 Via investigation of these 3d/4f heterobimetallic systems, important features of molecular magnetism, including the magnetocaloric effect (MCE), 1d quantum tunneling, 1c and slow magnetization relaxation, 11 have been realized.We have recently explored the reactions of oxoanions with large bond hyperpolarizabilities with lanthanides to probe structural discontinuities and atypical optical and magnetic properties. 12 Tellurites are particularly rich for a variety of reasons, including variable coordination numbers, the presence of a stereochemically active lo...