Electron spin pictorial representation

Fig. 3.1. Pictorial representation of the motions causing nuclear relaxation electron spin relaxation (A), molecular rotation (B) and chemical exchange (C). It can be seen that the electron dipolar field at the nucleus fluctuates with time in direction (A), intensity (C) or both (B).

Since we agreed that a bond needs not necessarily involve only two AOs on two centers, we must agree on some pictorial representation of a bond. This bond diagram is in Fig. 3.2, and shows two spin-paired electrons in general orbitals 9 and cp2, by a line connecting these orbitals. This bond diagram represents the wave function in Equation 3.12... 

As we discussed earlier, the electron has both particle-like and wave-like properties. Thus, the picture of an electron as a spinning charged sphere is, strictly speaking, just a useful pictorial representation that helps us understand the two directions of magnetic field that an electron can j... 

We can also represent the electron configuration of the hydrogen atom using an orbital diagram, which is a pictorial representation of the electron configuration that shows the spin of the electron (see Figure 1.30) ... 

In this kind of representation, which we will call an orbital diagram, each orbital is denoted by a box and each electron by a half arrow. A half arrow pointing upward (1) represents an electron with a positive spin magnetic quantum number (n s = +1), and a half arrow pointing downward (, ) represents an electron with a negative spin magnetic quantum number (wig = — ). This pictorial representation of electron spin is quite convenient. In fact, chemists and physicists often refer to electrons as "spin-up" and "spin-down" rather than specifying the value for tUg. 

The simple pictorial representation for the distribution of spins between the <2, and e, orbitals suggests for the d and d electron configurations the existence of a third ground state of intermediate multiplicity, viz. (f2,) (e,) with S= and (f2g) (Cg) with S=l, respectively. Thus, in the d configuration, iron(II) phthalocyanine [122] now is a well documented example for an 5= 1 ground state. Similarly, bis(diethyldithiocarbamato)iron(III) chloride is probably the best known case of an S= compound with the configuration d [123,124], For additional examples the reader is referred to the tables. 

Figure 6.15 Configuration assignment from pictorial representation - from left to right, electrons in the p-orbitals are labelled a, b, or c with the corresponding if the spin is meanwhile, electrons in the 5-orbital are labeled s or s.

Fig. 14.19. Pictorial description of the DA and D+A" structures. For a large donor-acceptor distance the electronic ground state is described by the DA structure (a). Structure D+A already becomes very important for the intermediate stage (I). This structure, belonging to the acceptor-donor picture, is shown (b) in the VB representation, where the opposite spins of the electrons remind us that we have the corresponding covalent structure.

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