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Electron density and electrostatic potential-based characteristics of molecular plasmons in polyacenes

preprint
submitted on 26.10.2017 and posted on 27.10.2017 by Mishu Paul, Balanarayan Pananghat
Plasmonic modes in single-molecule systems have been previously identified by scaling two-electron interactions while calculating excitation energies [Bernadotte et al., J. Phys. Chem. C, 2013, 117, 1863]. Analysis of transition dipole moments for states of polyacenes based on configuration interaction [Guidez et al., J. Phys. Chem. C, 2013, 117, 21466.] was yet another method characterizing molecular plasmons. The principal features in the electronic absorption spectra for polyacenes are a low-intensity, lower-in-energy peak (denoted as α) and a high-intensity, higher-in-energy peak (β ). From our calculations using time-dependent density functional theory (TD-DFT) at B3LYP/cc-pVTZ basis, both the peaks were found to result from the same set of electronic transitions (HOMO-n to LUMO and HOMO to LUMO+n, where n varies as the number of fused rings increases). In this work, the excited states of polyacenes, naphthalene through pentacene, have been analysed using electron densities and molecular electrostatic potential (MESP) topography. The bright and dark plasmonic states involve the least electron rearrangement, as compared to other excited states. Quantitatively, the MESP topography indicates that the variance in MESP values as well as displacement in minima positions (calculated with respect to the ground state) are lowest for plasmonic states. This suggests a resemblance between the plasmonic and ground state electronic density profiles and electrostatic potential topographies. On the other hand, a high electron-rearrangement characterizes a single particle excitation. The molecular plasmon can be called an excited state most similar to the ground state in terms of one-electron properties.

Funding

IISER Mohali ; SERB, Department of Science and Technology (DST), India

History

Topic

  • Computational chemistry and modeling
  • Theory

Email Address of Submitting Author

balanarayan@iisermohali.ac.in

Email Address(es) for Other Author(s)

mishupaul@iisermohali.ac.in , mishupaul1234@gmail.com

Institution

Indian Institute of Science Education and Research (IISER) Mohali, Punjab-140306.

Country

India

ORCID For Submitting Author

0000-0002-6024-2349

Declaration of Conflict of Interest

No conflict of Interest

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