Toward Quantitative Prediction of Molecular Fluorescence Quantum Efficiency:  Role of Duschinsky Rotation

Abstract

It is a highly desirable but difficult task to predict the molecular fluorescence quantum efficiency from first principles. The molecule in the excited state can undergo spontaneous radiation, conversion of electronic energy to nuclear motion, or chemical reaction. For relatively large molecules, it is impossible to obtain the full potential energy surfaces for the ground state and the excited states to study the excited-state dynamics. We show that, under harmonic approximation by considering the Duschinsky rotation effect, the molecular fluorescence properties can be quantitatively calculated from first principles coupled with our correlation function formalism for the internal conversion. In particular, we have explained the peculiar fluorescence behaviors of two isomeric compounds, cis,cis-1,2,3,4-tetraphenyl-1,3-butadiene and 1,1,4,4-tetraphenyl-butadiene, the former being nonemissive in solution and strongly emissive in aggregation or at low temperature, and the latter being strongly emissive in solution. The roles of low-frequency phenyl ring twist motions and their Duschinsky mode mixings are found to be crucial, especially to reveal the temperature dependence. As an independent check, we take a look at the well-established photophysics of 1,4-diphenylbutadiene for its three different conformers. Both the calculated radiative and nonradiative rates are in excellent agreement with the available experimental measurements.

Theoretical and experimental determination of the absorption and emission spectra of a prototypical indolenine-based squaraine dye

“…1,2 Fast growing research fields such as organic LED technology 3 and dye-sensitized solar cells (DSSC), 4 would strongly benefit from the application of robust and easy-to-use methodologies for the simulation of spectral lineshapes of organic dyes. The research in this field is quickly growing [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] (see also Borrelli et al 22 for a recent review) but standardize procedures have not yet been established, and specific computational strategies must be carefully designed and require validation and testing on several class of molecules. [23][24][25][26] In this paper we apply state of the art tools of computational spectroscopy to simulate the absorption and emission lineshapes of squaraine dyes in solution.…”

Theoretical predictions of red and near-infrared strongly emitting X-annulated rylenes

“…33 Using such formalism, we have previously rationalized the exotic aggregation induced emission phenomenon in several molecules. 34 We have also studied the effect of polyene chain length on the photophysical properties in diphenylpolyenes, 35 and we have analyzed the emission spectra for the luminescent group-14 metalloles. 36 This paper is organized as follows: (i) after this Introduction, we will describe the computational techniques for the excited states as well as the formalism of the optical spectra and excited state decay rates; (ii) then we will present the results on the excited state orderings for rylenes and heteroatom annulated rylenes, along with the molecular orbital analysis for the heteroatom bridges' effects; (iii) and finally, we will describe the emission spectra and excited state decays rates for the selected light-emitting molecules.…”

Basics of the time‐dependent wave‐packet propagation for photodissociations of polyatomic systems

“…Though this vertical excitation is usually the obvious starting point of the following time-propagation, the position may be adjusted towards a specific direction if there is a justifiable reason. For example, if the structural difference between the equilibrium structures of the ground and the target excited electronic states on the PESs used in the dynamical study is different from experimental results or from theoretical computations with a higher level of theory that was used in the production of the PESs in the current dynamical study, then adjustment of the initial position to match the more reliable geometrical reference, related to the Duschinsky rotation, [46,47] is recommendable to produce more meaningful results of dynamical simulations, as was shown in a recent publication. [48] Another example to adjust the initial position intentionally to study artifacts may be cases that include the effects of a wider range of PES in the excited electronic state than the area accessible by the vertical excitation.…”