Antiferromagnetic Mixed-Valence Cu(I)–Cu(II) Two-Dimensional Coordination Polymers Constructed by Double Oximato Bridged Cu(II) Dimers and Cu^ISCN Based One-Dimensional Anionic Chains

Abstract

One dinuclear Cu­(II) complex [Cu2L2 2(EtOH)0.5­(ClO4)]­(ClO4) (1) has been synthesized by reacting an oxime-based tridentate Schiff base ligand, 3-[2-(diethylamino)­ethylimino]­butan-2-one oxime (HL2), with CuII(ClO4)2, whereas the reaction of another similar ligand, 3-[2-(dimethylamino)­ethylimino]­butan-2-one oxime (HL1), and this ligand (HL2) with CuII(ClO4)2 in the presence of NaSCN yielded two rare mixed-valence Cu­(I)–Cu­(II) two-dimensional (2D) coordination polymers, 2 ∞[{(CuII 2L1 2)}­{CuI 4(μ1,3-SCN)2­(μ1,1,3-SCN)4}] n (2) and 2 ∞[{(CuII 2L2 2)}­{CuI 2(μ1,3-SCN)2­(μ1,1,3-SCN)2}] n (3), respectively. The presence of SCN– during the synthesis of the complexes induces reduction of a part of the Cu­(II) to Cu­(I) giving rise to these two novel mixed-valence 2D coordination polymers 2 and 3. All three complexes have been structurally and magnetically characterized. In complex 1, the square pyramidal Cu­(II) atoms are joined by the double oximato bridges. On the other hand, the railroad track-like 2D sheet of 2 and stair-like arrangement of the 2D layer of 3 have been constructed by the connection of one-dimensional (1D) anionic chains ([CuI 2(SCN)3] n n– in 2 and [CuI(SCN)2] n n– in 3) through the cationic oximato bridged dinuclear units ([CuII 2L1 2]2+ in 2 and [CuII 2L2 2]2+ in 3) via the sulfur atom of the thiocyanato ligand. In both complexes, Cu­(I) and thiocyanato ligand form 1D infinite chains, but their different stoichiometry and coordination environments around the copper centers result in different structures. Variable-temperature (2–300 K) magnetic susceptibility measurements show that complexes 1–3 exhibit a strong antiferromagnetic interaction between two Cu­(II) ions via N,O oximato bridges with J values −549.6, −578.7, and −663.8 cm–1, respectively.

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications

“…Antiferromagnets frequently exhibit such spin canting, where the spin carriers are linked by monoatomic bridges . Further, the most frequently encountered magnetic properties in 2D MOFs is the antiferromagnetic ordering, and this is dominated in the Cu­(II) containing 2D MOFs. − ,,− Several Mn­(II) and Co­(II), ,− ,− ,− and a few Fe­(II) and Ni­(II) 2D MOFs with mostly containing (4,4) grid structures have also exhibit this antiferromagnetic ordering. ,− ,− …”

Crystal structure of bis(N-(1-(pyrazin-2-yl)ethylidene)nicotinohydrazonato-κ3 N,N′,O)copper(II) C24H20N10O2Cu

“…All chemicals were purchased except for (E)-N′-(1-(pyrazin-2yl)ethylidene)nicotinohydrazide (HL), which was synthesized according to the literature [3]…”

Unusual mixed-valence CuII/CuI coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole and thiocyanate: Synthesis, structural characterization and antimicrobial in vitro activity assessment

“…In addition, we were interested in coligand thiocyanate because it is well known that thiocyanate can also partially reduce in situ, Cu II to Cu I and thus leads to mixed valence Cu(I/II)-thiocyanate coordination polymers. This type of mixed-valence complex is more interesting than those of Fe or Co because the copper (I) and copper (II) metal centers prefer different geometries and the two oxidation states are very labile and stereo chemically flexible [39,40]. On the other hand, the chemistry of mixed-valence Cu II /Cu I coordination complexes are gaining popularity due to its great applications in various fields like as biological activity [41,42], electronic properties [43,44] and electrical conductivity [45,46].…”