The electronic excited states of a model organic endoperoxide: A comparison of TD-DFT and ab initio methods

Corral, Inés; González, Leticia

doi:10.1016/j.cplett.2007.08.067

Cited by 9 publications

(2 citation statements)

References 27 publications

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“…The CC2 Franck–Condon excitation energies were calculated by using the TZVPP basis sets and the resolution of the identity (RI-J) approximation . The RI-CC2/TZVPP method is much more accurate in general than the more popular time-dependent DFT method and is thus preferred whenever applicable. , The CD spectra were simulated by summing the Gaussian function for each transition from more robust length-gauge representations where the bandwidth at 1/e height is fixed at 0.4 eV. This bandwidth was chosen to better match the experimental bandwidth, intensity, or both from our previous experiences.…”

Section: Resultsmentioning

confidence: 99%

Axial Chirality of Donor–Donor, Donor–Acceptor, and Tethered 1,1′-Binaphthyls: A Theoretical Revisit with Dynamics Trajectories

2011

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The circular dichroism (CD) spectra of (R)-2,2'-dimethoxy-1,1'-binaphthyl (DD) and its untethered and tethered donor-acceptor analogues (DA and DA7-DA9) were investigated experimentally and theoretically. The experimental CD spectra of DD and DA resembled each other in several aspects, displaying a positive-positive-negative Cotton effect pattern in the (1)L(b)-(1)L(a) region and a strong negative couplet at the (1)B(b) band, but significantly differed in transition energy and rotatory strength. The couplet amplitude (A) of the main band was 1.6 times larger in DA than in DD, despite the comparable extinction coefficients and seemingly analogous conformations. An additional positive Cotton effect was observed at the CT (CT) band for donor-acceptor binaphthyl DA. Our theoretical prediction of the CD spectra of binaphthyls involves three sequential first principle quantum mechanics (QM) calculations. Thus, the geometry optimizations of a series of conformers with varying dihedral angles were performed by the dispersion-corrected DFT-D method using the B97-D functional and the TZV2P basis set. The potential curve as a function of the dihedral angle (θ) was obtained by using the SCS-MP2/TZVPP single-point energy calculations with and without application of the solvent correction. The CD spectrum of each conformer was independently calculated by the second-order approximate coupled cluster calculation (CC2 method) using the TZVPP basis sets and the resolution of the identity (RI-J) approximation. The (net) theoretical CD spectrum was obtained by averaging over all possible conformers, where the dynamics trajectories based on the relative SCS-MP2 energies were taken into account. By using 17 possible conformers at θ varying from 50 to 130° by 5° intervals, the experimental CD spectra were successfully reproduced in a quantitative manner, enabling us to characterize properly almost all of the important spectral features and chiroptical properties. The two-state model, reported previously, turned out to have led to the right answer with wrong reasons. The couplet sign and amplitude A are critical functions of θ and can be used not only for (qualitatively) determining the absolute configuration but also for quantitatively analyzing the binaphthyl conformations. The angle dependence of A was already argued in the classical coupled oscillator and exciton chirality theories to provide reasonable structure elucidations but only in a qualitative or semiquantitative manner. Our method is able to predict the A value quantitatively as a function of θ. For tethered binaphthyls DA7-DA9, particular care should be exercised in the conformational assessment based on the classical treatment because the amplitude A was shown to be significantly affected by the existence of the tether itself. In the present method, the couplet amplitude A was nicely related to the dihedral angle θ of DA and DD by the state-of-the-art ab initio calculations, enabling us to gain the quantitative information about the conformation of axially chiral binaphth...

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Section: Resultsmentioning

confidence: 99%

Axial Chirality of Donor–Donor, Donor–Acceptor, and Tethered 1,1′-Binaphthyls: A Theoretical Revisit with Dynamics Trajectories

2011

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“…In passing we note that this configuration mixture was also observed in the S 1 state of an endoperoxide of smaller size. 34 According to our MS-CASPT2 calculations this transition lies at 3.85 eV and it is characterized by a very weak oscillator strength. In the light of these results, the experimental spectrum of APO 16 can be assigned as follows.…”

Section: Analysis Of the Spectrum And Comparison With Experimental Datamentioning

confidence: 98%

Theoretical investigation of anthracene‐9,10‐endoperoxide vertical singlet and triplet excitation spectra

Corral

González

2008

J Comput Chem

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The electronic absorption spectrum of anthracene-9,10-endoperoxide (APO) has been investigated by means of multiconfigurational multi-state second order perturbation theory on complete active space self-consistent field wavefunctions (MS-CASPT2/CASSCF) and two single reference methods: time-dependent density functional theory (TD-DFT) and coupled cluster of second order (CC2). After testing several active spaces and basis sets, a CAS (14,12) active space together with an ANO-S basis set was found an appropriate choice to describe the vertical singlet and triplet electronic states of APO. Unfortunately, TD-DFT and CC2 methods cannot reproduce the MS-CASPT2 and experimental spectrum. Our MS-CASPT2//CASSCF(14,12)/ANO-S calculations predict a predominant pi*(OO)sigma*(OO) character for the lowest singlet excited state S(1) at 3.85 eV. Accordingly, the lowest singlet state of APO should be responsible for homolysis of the endoperoxide group. The next two absorbing excited states, experimentally proposed to be responsible for singlet oxygen production and therefore connected to the biological interest of APO, have been computed vertically at 4.34 and 4.59 eV and assigned to pi(CC)pi*(CC) and pi*(OO)pi*(CC) transitions, respectively. The vertical triplet electronic spectrum follows the singlet vertical spectrum ordering. The high density of triplet and singlet excited states of different nature within few eV points to the possibility of intersystem crossings between potential energy surfaces of different multiplicity.

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Singlet oxygen generation versus O–O homolysis in phenyl-substituted anthracene endoperoxides investigated by RASPT2, CASPT2, CC2, and TD-DFT methods

2012

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The electronic excited states of a model organic endoperoxide: A comparison of TD-DFT and ab initio methods

Cited by 9 publications

References 27 publications

Axial Chirality of Donor–Donor, Donor–Acceptor, and Tethered 1,1′-Binaphthyls: A Theoretical Revisit with Dynamics Trajectories

Axial Chirality of Donor–Donor, Donor–Acceptor, and Tethered 1,1′-Binaphthyls: A Theoretical Revisit with Dynamics Trajectories

Theoretical investigation of anthracene‐9,10‐endoperoxide vertical singlet and triplet excitation spectra

Singlet oxygen generation versus O–O homolysis in phenyl-substituted anthracene endoperoxides investigated by RASPT2, CASPT2, CC2, and TD-DFT methods

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