Magnetic properties of complexes

Electronic Spectra and Magnetic Properties of Complexes of Nickel(II) ... 

Until about 20 years ago, the valence bond model discussed in Chapter 7 was widely used to explain electronic structure and bonding in complex ions. It assumed that lone pairs of electrons were contributed by ligands to form covalent bonds with metal atoms. This model had two major deficiencies. It could not easily explain the magnetic properties of complex ions. 

In this section we outline briefly the spectral and magnetic properties of complexes of the metals of Table 5. These are the properties that enable the stereo-chemical and electronic structures of metal complexes to be determined in solution and, hence in a biological environment. A study of these properties will be necessary to understand the nature of the interaction of the anti-tumour compounds with biological systems. 

In 2005, Matsuda and co-workers [20] investigated the magnetic properties of complex 93. The magnetic susceptibility measurement reveals the Mnm ion in the low-spin state (d45 = 1). However, the jJ.es at room temperature is 3.28pB, which is considerably higher than the calculated spin-only value of 2.83 pB for 5 = 1. The extraordinary pe i value should be due to the spin-orbit coupling effect. 

Relation of Energy Level Diagrams to Spectral and Magnetic Properties of Complexes... 

Chapter 11 Coordination Chemistry Bonding, Spectra, and Magnetism 387 Bonding in Coordination Compounds 391 Valence Bond Theory 391 Crystal Field Theory 394 Molecular Orbital Theory 413 Electronic Spectra of Complexes 433 Magnetic Properties of Complexes 459... 

Such effective changes are also manifest in connection with magnetic properties. On the basis of the orbital angular momentum of d-electrons, as will be examined in detail in due course, the magnetic behaviour of complexes is predicted by CFT to depart in a number of ways from that expected for the presence of electron spin alone. In fact, the magnetic properties of complexes are often rather close to the spin-only behaviour,2 28 29 and it is seen that a free-ion description of the J-orbitals is not adequate. 

Crystal field theory accounts for the magnetic properties of complexes as well as for their color. It explains, for example, why complexes with weak-field ligands,... 

The magnetic properties of complexes of these anions have been studied, particularly copper(n) complexes, and have been compared with the results obtained with analogous oxalato complexes the squarato and croconato bridges are... 

The investigation of the magnetic properties of compounds gives information concerning the valency states of the individual atoms in the compound. Before dealing with the magnetic properties of complex compounds we shall discuss briefly the magnetic properties of simpler compounds. ... 

From the valence bond point of view, formation of a complex involves reaction between Lewis bases (ligands) and a Lewis acid (metal or metal ion) with the formation of coordinate covalent (or dative) bonds between them. The model utilizes hybridization of metal s, p, and d valence orbitals to account for the observed structures and magnetic properties of complexes. For example, complexes of Pd(ll) and Pt(Il) are usually four-coordinate, square planar, and diamagnetic, and this arrangement is often found for Ni(II) complexes as well. Inasmuch as the free ion in the ground state in each case is paramagnetic (d, F), the bonding picture has to... 

Accounts for the optical and magnetic properties of complexes —> Ligands are considered to be point negative charges. 

---