Through-bond contributions

The accuracy of an additivity scheme can be increased by going from atomic contributions through bond contributions to group contributions. 

Originally the constant for the field/inductive effect was called the inductive constant ((jj). The field (through-space) contribution is, however, clearly larger than the inductive effect proper, i. e., the through-bond contribution. 

V. Russo, C. Curutchet and B. Mennucci, Towards a molecular scale interpretation of excitation energy transfer in solvated bichromophoric systems. II. The through-bond contribution, J. Phys. Chem. B, 111 (2007) 853-863. 

Note that the opposed signs of the through-space and through-bond contributions are a result of the nodal properties of the orbitals x and Xb- As is seen in Figure 4.25a, they have a node separating the main part of the orbital from the minor conjugatively delocalized part. However, the presence of the node... 

Although numerical calculations show that through-bond interactions normally dominate SOC in saturated biradicals [11], the results for ethylene and trimethylene indicate that both the through-space and the through-bond contributions exhibit a similar dependence on the rotation of the radical centers. This suggests the use of a "through-space" model [46] for a rationalization of this structural dependence, much in the spirit of the Salem-Rowland model [7] that was developed at a time when numerical results were not available. 

From these analyses, it can be seen that effective electronic communication may occur between the metal centers through the band states of the Ru metal core when a conjugated spacer is used to link the ferrocene moieties onto the particle surface, whereas saturated linkers diminish drastically the intervalence transfer at mixed valence. Additionally, the nanoparticle-mediated intervalence transfer appears to be primarily dominated by through-bond contributions rather than direct overlap between the metal centers. 

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