Electronics, molecular organic

Previous expositions of photochemical laws have distinguished ptominentiy between states of singlet and triplet multiplicity (1). This distinction continues to be important with respect to photophysics of smaH organic molecules, but among inorganic and organometaHic compounds, states of other multiplicities, eg, doublet and quartet states (23), play an important role. Spin conservation characterizes electronic molecular excitations and localized... 

Carrier generators in molecular conductors have been associated for a long time to a partial charge transfer between the HOMO (or LUMO) electronic band and other chemical species. These systems are known as two-component molecular conductors. Tetrathiofulvalene derivatives are versatile systems for the formation of molecular organic conductors due to their electron donor capacity by transferring one u-electron from the HOMO orbital, and to their planar shape that promotes their stacking as a consequence of the n-n orbital overlap. The electronic properties of these salts are essentially determined by the packing pattern of the donor molecules which, in turn, depends on the counter-ion. 

Equation (2.19), which concerns a situation without processes in the biofilm, can be extended to include transformation of a substrate, an electron donor (organic matter) or an electron acceptor, e.g., dissolved oxygen. If the reaction rate is limited by j ust one substrate and under steady state conditions, i.e., a fixed concentration profile, the differential equation for the combined transport and substrate utilization following Monod kinetics is shown in Equation (2.20) and is illustrated in Figure 2.8. Equation (2.20) expresses that under steady state conditions, the molecular diffusion determined by Fick s second law is equal to the bacterial uptake of the substrate. 

Sometimes 3(d — n ) and k ) states are said to be derived from delocalized orbitals and d—d) state from localized orbitals. The shift of the chelate emission from that of the free ligand increases in the sequence Rh(III) < Ir(III) < Ru(II) and reflects increasing cf-orbital participation in the emission orbital. The decrease in the chelate emission lifetime from the free ligand values also reflect the contamination of the molecular orbitals with d-character. The role of metal complexes as quenchers of excited states of it-electrons in organic compounds can be rationalized from such considerations. Emission from Cr8+ is the basis of one of the most important solid state laser system, the Ruby laser (Figure 10.14). 

Conduction, Electronic, in Organic Molecular Solids (Kearns). . 7 282... 

See, for example, (a) M. J. S. Dewar and G. J. Gleicher, J. Amer. Chem. Soc., 87, 685 (1965) for discussion of the various approaches to tt electron molecular orbital theory, see (b) Streitwieser, Molecular Orbital Theory for Organic Chemists, and (c) L. Salem, The Molecular Orbital Theory of Conjugated Systems, W. A. Benjamin, Menlo Park, Calif., 1966. 

The driving forces for electron transfer are a high-energy level of the highest occupied molecular orbital or a steric strain of the starting molecule. Complexation of oxygen by the electron-rich organic molecule has often been indicated as the first step of the mechanism. 

Reactions of hydrated electrons with organic compounds, 7, 115 Reactivity indices in conjugated molecules, 4, 73 Refractivity, molecular, and polarizability, 3, 1... 

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