A DFT Study of Vibrational Spectra and Mutagenicity Predictions of Mononitrated Fluoranthenes

Abstract

The Raman and infrared (IR) spectra of the mononitrated fluoranthenes (1-, 2-, 3-, 7-, and 8-nitrofluoranthene), important environmental pollutants that induce mutagenic/carcinogenic effects upon mammalian and bacterial cells, were studied via density functional theory, using optimized geometries at the B3LYP/6-311+G(d,p) and PBE0/6-311+G(d,p) levels of theory. The predicted harmonic vibrational frequencies were used in normal mode assignments. To validate the spectra, experimental fluoranthene and 3-nitrofluoranthene were used to benchmark the predicted spectra. The scaled harmonic frequencies below 2000 cm⁻¹are in good agreement to experiment to <5 cm⁻¹and 10 cm⁻¹or better at the B3LYP/6-311+G(d,p) and PBE0/6-311+G(d,p) levels, respectively. The high intensity nitro asymmetric/symmetric stretch modes (ν_asym/ν_symNO₂), ν(C‒C) and ν(C‒H) stretch frequencies were then considered, and used in distinguishing nitrofluoranthene isomers. The ν_sym(NO₂) frequency shifts are correlated to the observed mutagenic potencies, thus shedding light on their relative reactivity. The observed differential mutagenic-vibrational correlations, and implications of the ν_NO2shifts/biological mutagenic potencies between nitrofluoranthene isomers are then discussed.

Supplemental materials are available for this article. Go to the publisher's online edition of Polycyclic Aromatic Compounds to view the supplemental file.

Key Words:

• DFT
• dipole moments
• infrared-mutagenicity correlations
• IR/Raman spectra
• nitrofluoranthenes
• potential energy distributions
• symmetric/asymmetric nitro stretch

Acknowledgments

Financial Support from the Stephen F. Austin State University Faculty Research Grant (ORSP # 114110 and Research minigrants), the Robert A. Welch Foundation Grant Number AN-0008, and the SFASU Chemistry Department is acknowledged. We thank Professor Michael A. Janusa, for practical and personal support.