Substituent Effects on the Absorption and Fluorescence Properties of Anthracene

Abstract

Substitution can be used to efficiently tune the photophysical properties of chromophores. In this study, we examine the effect of substituents on the absorption and fluorescence properties of anthracene. The effects of mono-, di-, and tetrasubstitution of electron-donating and -withdrawing functional groups were explored. In addition, the influence of a donor-acceptor substituent pair and the position of substitution were investigated. Eleven functional groups were varied on positions 1, 2, and 9 of anthracene, and on position 6 of 2-methoxyanthracene and 2-carboxyanthracene. Moreover, the donor-acceptor pair NH/COH was added on different positions of anthracene for additional studies of doubly substituted anthracenes. Finally, we looked into quadruple substitutions on positions 1,4,5,8 and 2,3,6,7. Vertical excitation energies and oscillator strengths were computed using density functional theory with the hybrid CAM-B3LYP functional and 6-311G(d) basis set. Correlations between the excitation energies or oscillator strengths of the low-lying bright L state and the Hammett sigma parameter, σ, of the substituents were examined. The energy is red-shifted for all cases of substitution. Oscillator strengths increase when substituents are placed along the direction of the transition dipole moment of the bright L excited state. Substitution of long chain conjugated groups significantly increases the oscillator strength in comparison to the cases for other substituents. In addition, the results of quadruply substituted geometries reveal symmetric substitution at the 1,4,5,8 positions significantly increases the oscillator strength and can lower the band gap compared to that of the unsubstituted anthracene molecule by up to 0.5 eV.

Solvent dependence of cyanoindole fluorescence lifetime

“…We find that (1) the absorption spectra of these cyanoindoles, except that of 3-CNI, are significantly different from that of indole, (2) 2-CNI and 3-CNI are only weakly fluorescent, (3) solvents with strong hydrogen-bond donating ability, such as H 2 O and trifluoroethanol (TFE), significantly reduce the fluorescence lifetimes of 5-CNI, 6-CNI and 7-CNI, whereas in solvents with strong hydrogen-bond accepting ability, such as dimethyl sulfoxide (DMSO) and formamide (FA), these indole derivatives exhibit the longest fluorescence decay kinetics, and (4) the fluorescence lifetime of 4-CNI affords a unique dependence on solvent, with that measured in H 2 O being the longest. Taken together, we believe that these spectroscopic and kinetic results will not only help identify which cyanotryptophan to use for a given biological application, but also provide valuable experimental data for QM calculations of the substitution effect [38] to compare. Moreover, like that demonstrated previously for 5-CNI (and 5-cyanotryptophan) [39], we believe that the nitrile stretching vibrations of the other cyanoindoles also afford useful infrared applications [40].…”

Substituent Effects on the Solubility and Electronic Properties of the Cyanine Dye Cy5: Density Functional and Time-Dependent Density Functional Theory Calculations

“…In previous computational studies, researchers have used density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to calculate the structural and electronic properties of organic molecules [29][30][31]. Fothergill et al successfully used TD-DFT to calculate the vibrationally-resolved Cy5 monomer absorption spectrum that yielded a max absorption energy within 0.007 eV of experimental values [29].…”

Triplet‐State Position and Crystal‐Field Tuning in Opto‐Magnetic Lanthanide Complexes: Two Sides of the Same Coin

“…However, the consequences of the inductive effect exerted by specific moieties do not end there. On a more general level, the electron‐cloud distribution governs a number of properties of the chemical species, which encompass, but are not limited to, conductivity, reactivity, as well as catalytic and optical activity …”

“…On am ore general level, the electron-cloud distribution governs an umber of properties of the chemical species, which encompass, but are not limited to, conductivity, [1][2][3] reactivity, [4,5] as well as catalytic [6][7][8] and optical activity. [9][10][11][12][13] In the context of metal complexes, the choice of ligands containing different atoms-thus possessing ad istinctive electron-cloud distribution-enables the preparation of chemical species with tailored properties. Indeed, the interaction betweenp urposely designed ligands and the selectedm etal centrei sp ivotalt oe nsure the observation of features, such as sensitised photoluminescence [14,15] and magnetic anisotropy.…”