Ultraviolet Absorption Spectra of Substituted Phenols: A Computational Study†

Abstract

Vertical excitation energies for electronic transitions from the ground state to the first two excited states of phenol, mono- and disubstituted methoxyphenols and methyl-substituted phenols have been characterized with the Time-Dependent Density Functional Theory (TD-DFT), the Complete Active Space Self-Consistent Field method (CASSCF) and the Coupled Cluster with Single and Double Excitations Equation-of-Motion approach (CCSD-EOM) to simulate and interpret experimental ultraviolet absorption spectra. While CASSCF excitation energies for the first two transitions either are grossly overestimated or exhibit a weak correlation with experimental data, both TD-DFT and CCSD-EOM perform very well, reproducing the spectral shifts of both the primary band and secondary band observed upon substitution. The conformational dependence of the calculated excitation energies is generally smaller than the shifts caused by substitution.

Quinone–hydroquinone complexes as model components of humic acids: Theoretical studies of their structure, stability and Visible–UV spectra

“…We see that CIS, a Hartree-Fock based method, seriously overestimates the transition energies, while CIS(D) (CIS with double substitution corrections; Head-Gordon et al, 1994) still slightly overestimates them but time-dependent hybrid B3LYP calculations give quite accurate results, when compared with the highly accurate (and much more costly) CASPT2 calculations and with experiment. Similar trends have been seen in other systems (Tossell, 2004;Zhang et al, 2006). Since we need to extend our calculations to the D:A complex H 2 Q/Q and eventually to more complicated systems with substituents, TD B3LYP seems both an accurate and a computationally feasible method.…”

“…To evaluate Visible-UV absorption spectra we use timedependent density functional theory (TDDFT; Bauernschmitt and Ahlrichs, 1996;Stratmann and Scuseria, 1998), typically using a B3LYP functional and a 6-311+G(2d,p) basis. This has become the method of choice for calculating electronic spectra of large molecules because of its accuracy and computational efficiency (Furche and Ahlrichs, 2002;Jacquemin et al, 2006;Zhang et al, 2006). Such methods have recently been used by others within the geosciences (Boily and Seward, 2005).…”

Spiropyran-based reversible, light-modulated sensing with reduced photofatigue

“…38 It is also noted from previous work that o-methoxy substitution of phenols leads to a lengthening of the equivalent O-H bond and shortening of the C-O bond. 37 Encouraged by these findings, we prepared films made incorporating the two derivatives (SP1 and SP2) and studied their H + binding behaviour. A small piece of the film was cut, exposed to UV light for 1 min thereby trnasforming SP1 and SP2 into MC1 and MC2, respectively, and then immersed in universal buffer of known pH.…”

“…36,37 13 The optimized geometries of MC1, MC2, MC1-H + and MC2-H + generated using this approach, including relevant bond lengths, are shown in Figure 4. From the geometry optimized structures in Figure 4 we can estimate the relevant bond lengths.…”

Spectroscopic characterization of oceanic dissolved organic matter isolated by reverse osmosis coupled with electrodialysis

“…transparent to solar radiation; Helms et al, 2008). Thus, the NMR signal in this spectral region could be due to compounds containing single rings (or rings connected by non-conjugated structures such as peptides or proteins containing tyrosine or phenylalanine) that absorb at shorter wavelengths than condensed aromatic compounds (Zhang et al, 2006), single-ring aromatic compounds that are substituted with electron-withdrawing groups (Stubbins et al, 2008), or olefinic or isoprenoid moieties, which contain some sp 2 hybridized carbons but absorb at wavelengths shorter than the solar irradiance cut-off (~295 nm).…”