The response of electronic and energetic properties of conjugated vs aromatic molecules to an external uniform electric field

Nina Sadlej-Sosnowska

doi:10.1007/s11224-019-01345-6

Abstract

The susceptibility of electric and energetic properties of two sets of molecules to perturbation in a uniform electric field was investigated. The molecules of one set were deca-1,3,5,7-pentaene terminated with two functional groups, R1 and R2; those of the second set were 4-R1-4′-R2-p-diphenylbenzenes, with R1 and R2 being the same as in the polyene set. The polyene and aromatic molecules had similar lengths of the system of conjugated bonds between the two most extreme carbon atoms. Dipole moments were used as determinants of the overall charge transfer within the molecules. The electric field was directed along the main (longest) axes of the molecules from the negative pole to the positive. Comparison of the effect of the charge relocation in both sets of conjugated molecules revealed that the charge transfer imposed by the electric field was more efficient in the polyenes than in the aromatic compounds; however, for the molecule pairs with the same R1 and R2, reversal of the dipole moment direction falls at the same field strength. Parabolic dependence of the molecules’ energy as a function of field strength can also be interpreted in terms of the response of electron density to an electric field.

Highlights

There are a number of papers dealing with the impact of a homogeneous electric field on the structural and electronic properties of molecules
The dipole moments of the polyene and aromatic compounds were calculated in the absence of an external electric field (Table 1)
The plots of dipole moments against E, for data calculated at the CAM-B3LYP, are shown in Fig. 6 for one, the most interesting system, (R1=NO2 and R2=NH2)

Summary

Introduction

There are a number of papers dealing with the impact of a homogeneous electric field on the structural and electronic properties of molecules. Our first aim was to present and compare two ways of calculation of the field strength (E0) sufficient to reset to zero the overall dipole moment of a molecule. This convention is the same as applied in Gaussian input. The distances between two terminal C atoms, calculated for the two structures without substituents, where the terminal bonds were C-H instead of C-R1 and C-R2, were 11.47 Å for diphenylbenzene and 11.12 Å (in deca-1,3,5,7,9pentaene)

Results

Conclusion

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