Dipyrimidine–copper(II) dinitrate complexes showing magnetic interactions

Abstract

Crystals of Cu(II)(NO(3))(2)(pm)(3) (1), and two crystalline forms of Cu(II)(NO(3))(2)(H(2)O)(2)(pm)(2), (2) and (3), showed ferromagnetic, antiferromagnetic and paramagnetic interactions at extremely low temperatures, respectively. Crystal structure analyses revealed that the complexes were catena-dinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]-(pyrimidine-N(1))copper(II), [Cu(NO(3))(2)(pm)(2)](n), catena-diaquadinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]copper(II), [Cu(NO(3))(2)(H(2)O)(2)(pm)](n), and diaquadinitratodipyrimidinecopper(II), Cu(NO(3))(2)(H(2)O)(2)(pm)(2) for (1), (2) and (3), respectively. In (1) the Cu atom is coordinated by the two nitrates and N atoms of the non-bridging pyrimidine and bridging pyrimidine to form a one-dimensional coordination polymer. The complex is a five-coordinated square pyramid and can be regarded as a pseudo-seven-coordinated complex, since other short non-bonding Cu.O contacts are observed. In the crystals of (2) the pyrimidine bridges the Cu atoms to form a one-dimensional coordination chain. On the other hand, complex (3) is not a coordination polymer. It is important to form a coordination polymer for the appearance of the magnetic interactions. Types of coordination of the bridging organic moieties should also play an important role in magnetic properties. Magnetic measurements of (1) and (2) show that they are good examples of uniform S = 1/2 ferro- and antiferromagnetic Heisenberg chains with exchange parameters 2J/kB = +1.8 and -36 K, respectively.

One‐Dimensional Chains Formed by First‐Row Transition Metal(II) Nitrates and Pyrimidine – Influence of Water Coordination on Structural Reliability

“…Each metal node is connected to six adjacent nodes within the sheet using a total of eight hydrogen bonds, utilising all four water hydrogen atoms (two for each H 2 O), and both coordinated NO 3 -anions participating in two hydrogen bonds each. These hydrogen-bonded sheets are then crosslinked by the pyrimidine ligands into a three-dimensional network of 3 6 .4 18 .5 3 .6 topology ( Figure 4). A single-crystal diffraction study of 5 revealed a highly related structure to that observed in 1-4.…”

Synthesis, characterization and X-ray structural studies of four copper (II) complexes containing dinuclear paddle wheel structures

“…The apical positions of the octahedral coordination polyhedron are occupied by the N of a AMPY molecule (the Cu1 -N1 distance being 2.2724(18) Å and the Cu atom of the dimer). The Cu-N ax distance in unsubstituted pyrimidine containing copper complexes lies in range of (2.033 (4) Å and 2.025 (4) Å) [29,30]. The copper atoms are displaced from the respective basal planes towards the apical nitrogen atoms by 0.176 Å, and the Cu–Cu separation within the dimer was found to be 2.6691(5) Å, is typical for the dinuclear paddle wheel type of copper coordination compounds.…”

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

“…The above given examples indicate that the concept of spin polarization, which almost always works in organic chemistry to predict ferromagnetic interactions and to rationally develop new high-spin compounds, cannot be applied in a straight-forward manner to transition metal complexes. Several theoretical investigations were performed to get insight into the question why the concept of spinpolarization cannot be applied that simply to transition metal complexes [63,67,92,93]. Karafiloglou already showed for organic diradicals that not only the spin polarization, but also exchange and superexchange interactions contribute to the overall coupling [56].…”