Functional molecular system design

The challenge now is to design individual POM cluster molecules that can interact both with each other and with the macroscale (as shown in Figure 2.12), in a desired fashion in response to inputs and environmental effects, so that a functioning molecular system is really constructed. 

For a molecular system, 4 is a function of the positions f the electrons and thenu 1 within the molecule, which we will designate as r and R, respectively These h are a shorthand for the set of component vectors describing the position of each particle. We ll use subscripted versions of theig to denote the vector correspondin to a particular electron or nucleus r, andR/. Note that electrons are treated individually, while each nucleus is treated as an aggregate the component nucleon.s are not treated individually. 

This review article attempts to summarize and discuss recent developments in the studies of photoinduced electron transfer in functionalized polyelectrolyte systems. The rates of photoinduced forward and thermal back electron transfers are dramatically changed when photoactive chromophores are incorporated into polyelectrolytes by covalent bonding. The origins of such changes are discussed in terms of the interfacial electrostatic potential on the molecular surface of the polyelectrolyte as well as the microphase structure formed by amphiphilic polyelectrolytes. The promise of tailored amphiphilic polyelectrolytes for designing efficient photoinduced charge separation systems is afso discussed. 

The design of functionalized polymers with a specific utilization is seen in new polysiloxanes used by Zeldin (p. 199) as phase transfer catalysts. Novel functional polyphosphazenes have been reported as well by Allcock (p. 250). The introduction of transition metal cyclopentadienyl, metal carbonyl and carborane moieties into polyphosphazene macromolecules is representative of truly novel chemistry achieved after careful model studies with corresponding molecular systems. 

The characterization of molecular systems containing 1,2,4-triazole moieties has continued to employ familiar spectroscopic techniques, supplemented by more recent developments in the field. Other techniques, including electrochemistry, have also been described for triazoles that have been designed for or deployed in specific, applied environments such functional molecules are described later in this chapter. 

A detailed discussion of the theoretical evaluation of the adiabatic correction for a molecular system is beyond the scope of this book. The full development involves, among other matters, the investigation of the action of the kinetic energy operators for the nuclei (which involve inverse nuclear masses) on the electronic wave function. Such terms are completely ignored in the Born-Oppenheimer approximation. In order to go beyond the Born-Oppenheimer approximation as a first step one can expand the molecular wave function in terms of a set of Born-Oppenheimer states (designated as lec (S, r ))... 

Explicitly correlated wave functions described above have been specifically designed for two-electron molecular systems. As it was demonstrated in the previous section these functions give the energies which appear to be superior to the variational energies reported. Therefore several attempts have been made to extend this approach to many-electron molecules. The James-Coolidge (JC) type of function has been extended to three- and four-electron diatomic molecules by Clary and... 

Let us focus on molecular systems for which we know molecular Hamiltonian models, H(q,Q). Electronic and nuclear configuration coordinates are designated with the vectors q and Q, respectively x = (q,Q) = (qi,..., qn, Qi,---, Qm- For an n-electron system, q has dimension 3n Q has dimension 3m for an m-nuclei system. The wave function is the projection in configuration space of a particular abstract quantum state, namely P(x) P(q,Q), and base state func-... 

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