Polynuclear molecules

This electronic interaction constitutes an important parameter as far as the properties of polynuclear molecules are concerned. 

We cite here two examples of triiron complexes which can depict well the possible intramolecular electronic interactions in polymetallic complexes. First of all we take into account that, as discussed in Chapter 2, Section 1.5.1 and Chapter 4, Section 1.3, from the electrochemical viewpoint, the existence of a mutual electronic (through-space or through-bond) interaction in molecules containing two or more redox-active centres leads to the appearance of separate electron transfer processes. There are, however, two main classes of polynuclear molecules ... 

Polynuclear manganese redox enzymes, see Manganese, redox enzymes, polynuclear Polynuclear molecules, see Metals, ions Polynuclear polysulfideraetal complexes, 31 101-102... 

Spin-crossover, definition, 32 2 Spin delocalization, polynuclear molecules, 43 182-183... 

The magnetic properties of crystals composed of aromatic polynuclear molecules may give information on the relative orientations of the benzene rings to each other. Thus, Clews and Lonsdale (1937) concluded from the magnetic anisotropy of crystals of o-diphenylbenzene that the planes of the o-phenyl groups are inclined at 50° to the plane of the main ring. 

Figure 6.5 Polynuclear molecules - two atom centres circled for VSEPR...

Given the basic shapes of mononuclear molecules, cations and anions as determined by VSEPR theory, the bonding involved can then be described by the various types of hybrid orbitals, including double and triple bonding. In polynuclear molecules, VSEPR theory can be used to determine the stereochemistry at the separate atom centres present. Consequently the bonding at these separate atom centres can still be described by the appropriate types of hybrid orbitals, including multiple bonding. 

II. Interaction between Metal Ions in Polynuclear Molecules... 

The bg therefore defines the geometrical shape of the minimum in the usual way. If the minimum figure is a plane, then the potential well is diffeomorphic to SO(3), and if it is nonplanar, then it is diffeomorphic to 0(3) and so the well is actually a symmetric double well. In either case, Klein et al. show that the eigenvalues and eigenfunctions for a polynuclear molecule can be obtained as WKB-type expansions to all orders4 of the parameter k. Hence, it is properly established that the Bom-Oppenheimer approach leads to asymptotic solutions for the full problem but, interestingly, the potential is usually a double-well one. 

In the search for catalytically active species, heterobi-and polynuclear molecules containing both U(III) and a transition metal (palladium, platinum, rhodium, or ruthenium) strongly bonded in close proximity but without a direct metal-metal bond were synthesized. Difunctional bridging ligands like cyclopentadienylphosphido ligands were used to form such complexes. 

---