Comparative parametric method 6 (PM6) and Recife model 1 (RM1) study of trans-stilbene

Abstract

In this paper, we report a comparative parametric method 6 (PM6) and Recife model 1 (RM1) study of trans-stilbene in its ground and (excited) singlet, triplet and ionic (positive and negative polarons and bipolarons) states. We evaluated the accuracy of the recently developed PM6 and RM1 comparing the obtained results with other semi-empirical, ab initio methods and available experimental data. PM6 and RM1 predict non-planar ground and singlet states for trans-stilbene, in agreement with the PM5 and the Austin model 1. On the other hand, the PM3 predicts planar configurations, which is in agreement with the available experimental data. PM6 and RM1 overestimate the cis–trans isomerisation energy as well as the ionisation potential of both cis- and trans-stilbene. In spite of the developments of these new methods, PM3 continues to be the only one of these methods to correctly predict the conformation of stilbene.

Keywords:

• trans-stilbene
• PM6
• RM1
• semi-empirical methods

Acknowledgements

The authors acknowledge the financial support of the Brazilian Agencies CNPq, IMMP/MCT, THEO-NANO, CAPES, FAPESP and Fundação Araucária.

Notes

1. Email: [email protected]

2. Email: [email protected]

3. Email: [email protected]