Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study

Abstract

Articles you may be interested inElectronic spectra and photodissociation of vinyl chloride: A symmetry-adapted cluster configuration interaction study J. Chem. Phys. 124, 034312 (2006) Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study Electronic structures of azaindole were studied using symmetry-adapted cluster configuration interaction theory utilizing Dunning's cc-pVTZ basis set augmented with appropriate Rydberg spd functions on carbon and nitrogen atoms. The results obtained in the present study show good agreement with the available experimental values. Importantly, and contrary to previous theoretical studies, the excitation energy calculated for the important n-π * state agrees well with the experimental value. A recent study by Pratt and co-workers concluded that significant mixing of π-π * and n-π * states leads to major change in the magnitude and direction of the dipole moment of the upper state vibrational level in the 0,0 + 280 cm −1 band in the S 1 ← S 0 transition when compared to that of the zero-point level of the S 1 state. The present study, however, shows that all the four lowest lying excited states,n-π * , and π-σ * , cross each other in one way or another, and hence, significant state mixing between them is likely. The upper state vibrational level in the 0,0 + 280 cm −1 band in the S 1 ← S 0 transition benefits from this four-state mixing and this can explain the change in magnitude and direction of the dipole moment of the S 1 excited vibrational level. This multistate mixing, and especially the involvement of π-σ * state in mixing, could also provide a route for hydrogen atom detachment reactions. The electronic spectra of benzimidazole, a closely related system, were also investigated in the present study. C 2015 AIP Publishing LLC. [http://dx

Low-Lying ππ* States of Heteroaromatic Molecules: A Challenge for Excited State Methods

“…The patterns of the L a and L b states for the set of Scheme are less systematic than in the oligoacene series. The presence of heteroatom(s) induces some variations on the nature of the ππ* transitions, such as character mixing with nearby πσ* and nπ* states, or between the L a and L b states . For compound VIII, a moiety frequently found in organic electronics, there is even an ambiguity in determining the character of L a and L b since both states belong to the same irreducible representation and, therefore, mix (see the SI for the assignment used herein).…”

“…Therefore, the L a -L b problem originates from the description of both states. Indole (a building block of tryptophan amino acid) and several structurally related compounds were found to behave similarly. − Indeed, it was shown that both hybrid and meta -GGA functionals predict a wrong ordering of the L a and L b ππ* states, whereas range-separated hybrid functionals, despite providing a qualitatively correct ordering of the states, predict much too small energy gaps compared to the experimental values. The inversion of the L a and L b states was also spotted for 9H-adenine by comparing TD-DFT estimates to high level reference values obtained with wave function-based approaches, such as EOM-CCSD­(T) (equation of motion-coupled cluster singles and doubles with perturbative triples) or CASPT2 (complete active space second-order perturbation theory), even though the ambiguity still remains in this case .…”

Pre-Dewar structure modulates protonated azaindole photodynamics

“…1 for the atom numbering) are excellent blue emitters for organic lightemitting diodes (OLEDs). 4 Although one can find a handful of articles on 7-azaindole as an isolated monomer, [5][6][7][8] in dimeric forms 5,[9][10][11][12][13] and in water and alcohol clusters, 11,[14][15][16][17][18][19][20] only one recent article 21 to date shed light upon the photophysical relaxation mechanism of nazaindole molecules by studying gas-phase excited-state dynamics. Experiments and theoretical calculations have also been devoted 16,18,[22][23][24] to understanding the excited-state proton transfer and tautomerization mechanism of 7-azaindole with solvent molecules.…”

Weak Dewar bond modulates protonated azaindole photodynamics

“…Experimental spectral width and derived lifetimes of n-AIH + isomers from Ref. 25 Although one can find a handful of articles on 7-azaindole in isolated monomer, [5][6][7][8] in dimeric forms 5,[9][10][11][12][13] and water and alcohol clusters, 11,[14][15][16][17][18][19][20] only one recent article 21 to date shed light upon the photophysical relaxation mechanism of n-azaindole molecules by studying gasphase excited-state dynamics. Experiments and theoretical calculations have also been devoted 16,18,[22][23][24] to understanding the excited-state proton transfer and tautomerization mechanism of 7-azaindole with solvent molecules.…”