A new end-on azido-bridged dicopper(II) complex; syntheses, structure, solvatochromism, magnetic properties, and DFT study

A new asymmetric azido-bridged dinuclear copper(II) complex with formula [L(N₃)Cu(μ_N,N-N₃)]₂, L = N,N-dimethyl-N′-benzyl-ethylenediamine, has been synthesized and characterized structurally and magnetically. Single-crystal structural analysis reveals the Cu(II) ions are linked by two end-on azido nitrogen atoms. The copper(II) ions adopt s penta-coordinated geometry that is intermediate between square pyramidal and trigonal bipyramidal (τ = 0.528). Variable temperature magnetic susceptibility data were collected and fitted to the appropriate equations derived from the Hamiltonian H = −JS ₁ S ₂ that show antiferromagnetic intradimer interactions with J = −1.0 cm⁻¹ through the end-on azido bridges between the metal centers. To rationalize the magnetic behavior, a DFT calculation has been performed within the broken symmetry framework. The analyses of the magnetic orbital interaction and spin distribution indicate the nature of the magnetic properties of the complex. The complex is solvatochromic and its solvatochromism was investigated by visible spectroscopy. To explore the mechanism of interaction between the solvent molecules and the complex, different solvent parameters were utilized and analyzed by a statistical method using the multiple linear regression (MLR) method. It was found that the hydrogen bond donation (β) and polarity/polarizability (π*) parameters of the solvents lead to the solvatochromism property.