Absorption and fluorescence properties of oligothiophene biomarkers from long-range-corrected time-dependent density functional theory

Abstract

The absorption and fluorescence properties in a class of oligothiophene push-pull biomarkers are investigated with a long-range-corrected (LC) density functional method. Using linear response timedependent density functional theory (TDDFT), we calculate excitation energies, fluorescence energies, oscillator strengths, and excited-state dipole moments. To benchmark and assess the quality of the LC-TDDFT formalism, an extensive comparison is made between LC-BLYP excitation energies and approximate coupled cluster singles and doubles (CC2) calculations. When using a properly-optimized value of the range parameter, , we find that the LC technique provides an accurate description of charge-transfer excitations as a function of biomarker size and chemical functionalization. In contrast, we find that re-optimizing the fraction of Hartree Fock exchange in conventional hybrid functionals still yields an inconsistent description of excitation energies and oscillator strengths for the two lowest excited states in our series of biomarkers. The results of the present study emphasize the importance of a distance-dependent contribution of exchange in TDDFT for investigating excited-state properties.2

Tuning Range-Separated Density Functional Theory for Photocatalytic Water Splitting Systems

“…20,35,40,42,50,52,53,[59][60][61][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82] The accuracy of optimally tuned range-separated functionals was critically tested in ref 61 for basis set variation as well as prediction of relative energies of spin states, binding energies, and the form of potential energy surfaces.…”

Assessment of asymptotically corrected model potentials for charge-transfer-like excitations in oligoacenes

“…In particular, some of these situations occur in the asymptotic regions of atoms and molecules, where the LDA or GGA XC potential exhibits an exponential decay, instead of the correct −1/r decay. Accordingly, LDA and GGAs (i.e., semilocal density functionals) severely underestimate high-lying Rydberg excitation energies [7][8][9][10], and completely fail for charge-transfer (CT) excitation energies [10][11][12][13][14][15] and excitations in completely symmetrical systems where no net CT occurs [16].…”

Short- and long-range corrected hybrid density functionals with the D3 dispersion corrections

“…Even if the asymptote problems can be properly resolved by the recently developed semilocal density functionals with correct asymptotic behavior [42][43][44][45][46] and asymptotically corrected model XC potentials [47][48][49][50][51], the SIE problems may remain unresolved [52]. Besides, semilocal density functionals are inaccurate for charge-transfer (CT) excitation energies [41,42,[52][53][54][55][56][57][58][59][60][61], due to the lack of a space-and frequency-dependent discontinuity in the adiabatic XC kernel adopted in TDDFT [62].…”