Synthesis, Tuning of the Stereochemistry, and Physical Properties of Cobalt(II) Tropocoronand Complexes

Mapping the Stereochemistry and Symmetry of Tetracoordinate Transition‐Metal Complexes

“…Indeed, Poli [73] has proposed that the high-spin quartet state prefers the tetrahedral geometry, whereas the low-spin doublet prefers square-planar structures. Lippard and co-workers [116] prepared a series of Co II tropocoronand complexes with variable size of the macrocyclic ligands, achieving in this way a tuning of the stereochemistry from distorted square planar for the smaller macrocycles to distorted tetrahedral for the larger ones. These authors showed that the nearly square planar complexes have low spin, whereas the nearly tetrahedral ones have high-spin configurations.…”

“…Furthermore, for Co II and Ni II the distortion from square planar to tetrahedral is accompannied by a change in the spin state. [116,131,162] …”

Synthesis and magnetic studies of μ-oxalato-bridged copper(II)-M(III)-copper(II) (M=Cr and Fe) heterotrinuclear complexes

“…In fact, the present complexes [Cu 2 Cr(ox) 3 (tmen 2 )ClO 4 (1) and [Cu 2 Fe(ox) 3 (tmen) 2 ]ClO 4 (2) have the same skeleton of the oxalate bridging structure and the same terminal ligand, thus, their IR and coordination environment are also similar. The only difference between [Cu 2 Cr(ox) 3 (tmen) 2 ]ClO 4 and [Cu 2 Fe(ox) 3 (tmen) 2 ]ClO 4 is that the central metal ion is chromium(III) in the former case and iron(III) in the latter. The essential difference between the sign of the exchange parameter J in the two complexes indicates that the kinds of metal ions may affect the nature of the exchange interaction.…”

“…Interests in the syntheses and magnetic properties of heteropolynuclear complexes containing different paramagnetic centers are fundamental requirement, [1][2][3][4][5][6][7][8] not only for gaining some insight into the structural and electronic-structural factors causing spin-exchange interaction between paramagnetic centers and the pathway of electron transfer in biological systems, but also for obtaining information about designing and synthesizing molecular-based ferromagnets and for investigating the spin-exchange mechanism between paramagnetic metal ions. So far, much effort has been devoted to the development of multiatom bridging ligands that can afford magnetic interactions.…”

“…In this paper, two new m-oxalato-bridged heterometal trinuclear complexes formulated [Cu 2-Cr(ox) 3 (tmen) 2 ]ClO 4 (1) and [Cu 2 Fe(ox) 3 (tmen) 2 ]-ClO 4 (2), where ox is oxalato dianions; tmen stands for N,N,N 0 ,N 0 -tetramethylethylenediamine, have been synthesized and characterized by using potassium tris(oxalato)chromium(III) trihydrate (K 3 [Cr(ox) 3 ] Á 3H 2 O) and potassium tris(oxalato)iron(III) trihydrate (K 3 [Fe(ox) 3 ] Á 3H 2 O), respectively, as polyatomic bridging ligands. The cryomagnetic properties of the two heterotrinuclear complexes were measured in the temperature range 4.2-300 K to investigate the electronicstructural variation of the metal ions effects upon the nature of spin-exchange interaction between the paramagnetic centers.…”