Orbital Angular Momentum Contribution to the Magneto-Optical Behavior of a Binuclear Cobalt(II) Complex

Abstract

We report magnetic and magnetic circular dichroism investigations of a binuclear Co(II) compound. The Hamiltonian of the system involves an isotropic exchange interaction dealing with the real spins of cobalt(II) ions, spin-orbit coupling, and a low-symmetry crystal field acting within the (4)T(1g) ground manifold of each cobalt ion. It is shown that spin-orbit coupling between this ground term and the low-lying excited ones can be taken into consideration as an effective g factor in the Zeeman part of the Hamiltonian. The value of this g factor is estimated for the averaged experimental values of Racah and cubic ligand field parameters for high-spin cobalt(II). The treatment of the Hamiltonian is performed with the use of a irreducible tensor operator technique. The results of the calculation are in good agreement with experimental observations. Both a large effective g factor for the ground state and a large temperature-independent part of the magnetic susceptibility arise because of a strong orbital contribution to the magnetic behavior of the Co(II) dimer.

Double‐CO32− Centered [CoII5] Wheel and Modeling of Its Magnetic Properties

“…The solution electrical conductivity and electronic spectra were obtained by using a Unitech type U131C digital conductivity meter with a solute concentration of about 10 À3 m and a Shimadzu 1601 UV-Vis-NIR spectrophotometer, respectively. 1 H and 13 C NMR spectra were recorded in CDCl 3 with a Bruker AC 200 NMR Spectrometer using TMS as the internal standard. Variable-temperature magnetic susceptibility data were obtained with a Quantum Design MPMS5 SQUID magnetometer.…”

“…The latter has been taken into account in recent models making use of various diagonalization techniques or even providing approximate analytical expressions of the paramagnetic susceptibility for dinuclear Co II complexes. [11][12][13] More recently, some of us have proposed a convenient model to treat the magnetic exchange within polynuclear clusters of axially distorted six-coordinate cobalt(II) ions invoking a perturbational approach, which greatly reduces the size of the matrices to be diagonalized. [14] We report here the synthesis and structure of a rare [Co II 5 ] wheel, assembled by the bridging action of the Schiffbase ligand Hbpp (2,6-bis(phenyliminomethyl)-4-methylphenol, Scheme 1) [15] and the template effect of two carbonate ions, with the formula [Co 5 - (1).…”

Use of magnetic circular dichroism to study dinuclear metallohydrolases and the corresponding biomimetics

“…Several MCD studies of dinuclear complexes, which serve as structural and spectroscopic models of dinuclear hydrolases, have been reported in recent years (Ostrovsky et al 2006;Johansson et al 2008;Larrabee et al 2008Larrabee et al , 2009Xavier et al 2009;Ostrovsky et al 2009;Daumann et al 2013Daumann et al , 2014. Most of these studies have focussed on dicobalt complexes; the exceptions were Fe(III)Co(II) and Ga(III)Co(II) complexes (Xavier et al 2009).…”

“…Two of the bridging acetate groups are µ-1,3. The third acetate is bound to one Co(II) ion in a bidentate fashion, and one of the two oxygen atoms also bridges the Co(II) ions in µ-1,1 fashion (Ostrovsky et al 2006). The MCD spectrum of this complex is typical of those for six-coordinate Co(II), a band centred at 510 nm arising from the 4 T 1g → 4 T 1g (P) transition in the parent O h symmetry that is split into three partially resolved peaks.…”

High-spin Co(II) in monomeric and exchange coupled oligomeric structures: Magnetic and magnetic circular dichroism investigations

“…(5), the spin-orbit interaction between the 4 T 1g ground state and any excited state is neglected. After accounting for this interaction [35] the g 0 value in Eq. (5) must be replaced by g 0 + g, where g depends on the Racah and cubic crystal field parameters as well as on the one-electron spin-orbit coupling constant.…”