The electronic states of a Nile red fluorescent dye molecule in an aqueous solution are studied using the time-dependence density functional theory. Transitions between these states corresponding to absorption of dye molecules in the visible region of the spectrum are investigated. The performed calculations showed the absence of twisting of the aminodiethyl group upon excitation of the molecule due to absorption of a photon. The photoinduced charge transfer was found to be insignificant. The dipole moments of the ground and excited states are calculated and analyzed from the point of view of the theory of solvatochromism.
Nile red, time-dependence density functional theory, polarizable continuum model, electronic transitions, molecular orbitals, solvatochromism
1. Reichardt C. Solvatochromic Dyes as Solvent Polarity Indicators. Chem. Rev., 1994, vol. 94, pp. 2319-2358.
2. Deye J.F., Berger T.A., Anderson A.G. Nile Red as a Solvatochromic Dye for Measuring Solvent Strength in Normal Liquids and Mixtures of Normal Liquids with Supercritical and Near Critical Fluids. Anal. Chem., 1990, vol. 62, pp. 615-622.
3. Kawski A., Bojarski P., Kuklinski B. Estimation of ground- and excited-state dipole moments of Nile Red dye from solvatochromic effect on absorption and fluorescence spectra. Chem. Phys. Lett., 2008, vol. 463, pp. 410-412.
4. Freidzon A.Ya., Safonov A.A., Bagaturyants A.A., Alfimov M.V. Solvatofluorochromism and Twisted Intramolecular Charge-Transfer State of the Nile Red Dye. Int. J. Quant. Chem., 2012, vol. 112, pp. 3059-3067.
5. Han W.-G., Liu T., Himo F., Toutchkine A., Bashford D., Hahn K.M., Noodleman L. A Theoretical Study of the UV/Visible Absorption and Emission Solvatochromic Properties of Solvent-Sensitive Dyes. ChemPhysChem, 2003, vol. 4, pp. 1084-1094.
6. Murugan N.A., Kongsted J., Rinkevicius Z., Agren H. Color modeling of protein optical probes. Phys. Chem. Chem. Phys., 2012, vol. 14, pp. 1107-1112.
7. Murugan N.A., Rinkevicius Z., Agren H. Modeling Solvatochromism of Nile Red in Water. Int. J. Quant. Chem., 2011, vol. 111, pp. 1521-1530.
8. Marazzi M., Gattuso H., Monari A. Nile blue and Nile red optical properties predicted by TD-DFT and CASPT2 methods: static and dynamic solvent effects. Theor. Chem. Acc., 2016, vol. 135, p. 57.
9. Ray A., Das S., Chattopadhyay N. Aggregation of Nile Red in Water: Prevention through Encapsulation in β-Cyclodextrin. ACS Omega, 2019, vol. 4, pp. 15-24.
10. Foresman J.B., Frisch A.E. Exploring Chemistry with Electronic Structure Methods, 3rd ed. Gaussian, Inc., Wallingford, CT, 2015.
11. Cossi M., Barone V. Time-dependent density functional theory for molecules in liquid solutions. J. Chem. Phys., 2001, vol. 115, pp. 4708-4717.
12. Scalmani G., Frisch M.J. Continuous surface charge polarizable continuum models of solvation. I. General formalism. J. Chem. Phys., 2010, vol. 132, p. 114110.
13. Cohen A.J., Handy N.C. Dynamic correlation. Mol. Phys., 2001, vol. 99, pp. 607-615.
