Heptacopper(II) and dicopper(II)-adenine complexes: synthesis, structural characterization, and magnetic properties

Abstract

The syntheses, crystal structures, and magnetic properties of two new copper(II) complexes with molecular formulas [Cu 7 (μ 2 -OH 2 ) 6 (μ 3 -O) 6 (adenine) 6 ](NO 3 ) 2 ·6H 2 O (1) and [Cu 2 (μ 2 -H 2 O) 2 (adenine) 2 (H 2 O) 4 ](NO 3 ) 4 ·2H 2 O (2) are reported. The heptanuclear compound is composed of a central octahedral CuO 6 core sharing edges with six adjacent copper octahedra. In 2, the copper octahedra shares one equatorial edge. In both compounds, these basic copper cluster units are further linked by water bridges and bridging adenine ligands through N3 and N9 donors. All copper(II) centers exhibit Jahn-Teller distorted octahedral coordination characteristic of a d 9 center. The study of the magnetic properties of the heptacopper complex revealed a dominant ferromagnetic intra-cluster interaction, while the dicopper complex exhibits antiferromagnetic intra-dimer interactions with weakly ferromagnetic inter-dimer interaction.

1D and 3D supramolecular structures exhibiting weak ferromagnetism in three Cu(II) complexes based on malonato and di-alkyl-2,2’-bipyridines

“…Hydrogen-bond magnetic interactions have been reported previously for other Cu(II) complexes and polymers, including malonate or its derivatives and have been described exhibiting both antiferromagnetic behavior [32,41,42] and ferromagnetic exchange [26,29,40,[43][44][45]. Therefore, according to the above mentioned, the obtained values for the exchange coupling constant (vide supra) for the three complexes are in agreement with those recently reported for Cu(II) complexes having hydrogen bonding or other intermolecular interactions [46][47][48][49][50][51].…”

Porous Supramolecular Architectures Based on π-Stacking Interactions between Discrete Metal-Adenine Entities and the Non-DNA Theobromine/Caffeine Nucleobases

“…This behavior and the obtained superexchange values are similar to those published for other similar whell-shaped copper(II) heptameric entities in which the outer metal atoms are ferromagnetically coupled to each other and antiferromagnetically coupled to the central atom. 4,20 As previously stated, the dehydration procedure gives rise to a substantial reorganization of the crystal structure of compound 1. In order to get some insight on the persistence of the heptanuclear entity after this structural rearrangement, the magnetic characterization of an activated sample of compound 1 was accomplished (Figure S7).…”

Quantum correlations and Bell’s inequality violation in a Heisenberg spin dimer via neutron scattering

“…The study of molecular magnetic materials is typically done through the approach of the magnetic parameters of a Hamiltonian model, by the fit of some thermodynamic properties, e.g., magnetic susceptibility, internal energy, and specific heat [17,[31][32][33][34]. For a given Hamiltonian model, one can evaluate the inelastic structure factor, which allows a sensitive test of the assumed model, since their properties are affected by the relative positions of the metallic centers of a sample material [32].…”

“…The study of the magnetic properties of molecular materialsis typically done approximating magnetic parameters of a Hamiltonian model by the fit of some thermodynamic properties, such as magnetic susceptibility, internal energy and specific heat [17,[31][32][33][34]. In this context, correlation functions have great importance in describing these properties; in addition, they can be directly measurable, e.g., in neutron scattering experiments via structure factors.…”