scholarly journals The Low Lying Double-Exciton State of Conjugated Diradicals: Assessment of TDUDFT and Spin-Flip TDDFT Predictions

Computation ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 68 ◽  
Author(s):  
Canola ◽  
Dai ◽  
Negri
Keyword(s):  
Excited State ◽  
Molecular Orbital ◽  
Density Functional ◽  
Photophysical Properties ◽  
Exciton State ◽  
Reference Configuration ◽  
Singlet Ground State ◽  
Distinctive Character ◽  
Spin Flip ◽  
Potential Applications

Conjugated singlet ground state diradicals have received remarkable attention owing to their potential applications in optoelectronic devices. A distinctive character of these systems is the location of the double-exciton state, a low lying excited state dominated by the doubly excited HOMO,HOMOLUMO,LUMO configuration, (where HOMO=highest occupied molecular orbital, LUMO=lowest unoccupied molecular orbital) which may influence optical and other photophysical properties. In this contribution we investigate this specific excited state, for a series of recently synthesized conjugated diradicals, employing time dependent density functional theory (TDDFT) based on the unrestricted parallel spin reference configuration in the spin-flip formulation (SF-TDDFT) and standard TD calculations based on the unrestricted antiparallel spin reference configuration (TDUDFT). The quality of computed results is assessed considering diradical and multiradical descriptors, and the excited state wavefunction composition.

scholarly journals The Low Lying Double-Exciton State of Conjugated Diradicals: Assessment of TDUDFT and Spin-Flip TDDFT Predictions

2019 ◽  
Author(s):  
Sofia Canola ◽  
Yasi Dai ◽  
Fabrizia Negri
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Photophysical Properties ◽  
Exciton State ◽  
Reference Configuration ◽  
Singlet Ground State ◽  
Distinctive Character ◽  
Spin Flip ◽  
Doubly Excited ◽  
Potential Applications

Conjugated singlet ground state diradicals have received remarkable attention owing to their potential applications in optoelectronic devices. A distinctive character of these systems is the location of the double exciton state, a low lying excited state dominated by the doubly excited H,H→L,L configuration, which may influence optical and other photophysical properties. In this contribution we investigate this specific excited state, for a series of recently synthesized conjugated diradicals, employing time dependent density functional theory based on the unrestricted parallel spin reference configuration in the spin-flip formulation (SF-TDDFT) and standard TD calculations based on the unrestricted antiparallel spin reference configuration (TDUDFT). The quality of the computed results is assessed considering diradical and multiradical descriptors and the excited state wavefunction composition.

scholarly journals Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3904
Author(s):  
Kaveendra Maduwantha ◽  
Shigeyuki Yamada ◽  
Kaveenga Rasika Koswattage ◽  
Tsutomu Konno ◽  
Takuya Hosokai
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Density Functional Theory Calculations ◽  
Time Resolved ◽  
Excited State Dynamics ◽  
Unique Material ◽  
Potential Applications ◽  
Time Resolved Photoluminescence

Room-temperature phosphorescent (RTP) materials have been attracting tremendous interest, owing to their unique material characteristics and potential applications for state-of-the-art optoelectronic devices. Recently, we reported the synthesis and fundamental photophysical properties of new RTP materials based on benzil, i.e., fluorinated monobenzil derivative and fluorinated and non-fluorinated bisbenzil derivative analogues [Yamada, S. et al., Beilstein J. Org. Chem. 2020, 16, 1154–1162.]. To deeply understand their RTP properties, we investigated the excited-state dynamics and photostability of the derivatives by means of time-resolved and steady-state photoluminescence spectroscopies. For these derivatives, clear RTP emissions with lifetimes on the microsecond timescale were identified. Among them, the monobenzil derivative was found to be the most efficient RTP material, showing both the longest lifetime and highest amplitude RTP emission. Time-resolved photoluminescence spectra, measured at 77 K, and density functional theory calculations revealed the existence of a second excited triplet state in the vicinity of the first excited singlet state for the monobenzil derivative, indicative of the presence of a fast intersystem crossing pathway. The correlation between the excited state dynamics, emission properties, and conformational flexibility of the three derivatives is discussed.

scholarly journals Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks

2020 ◽  
Author(s):  
Kaveendra Maduwantha ◽  
Shigeyuki Yamada ◽  
Kaveenga Rasika Koswattage ◽  
Tsutomu Konno ◽  
Takuya Hosokai
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Density Functional Theory Calculations ◽  
Time Resolved ◽  
Excited State Dynamics ◽  
Unique Material ◽  
Potential Applications ◽  
Time Resolved Photoluminescence

Room-temperature phosphorescent (RTP) materials have been attracted tremendous interest owing to their unique material characteristics and potential applications for state-of-the-art optoelectronic devices. Recently, we have reported a synthesis and fundamental photophysical properties of new RTP materials based on benzil, i.e., fluorinated monobenzil derivative and fluorinated and non-fluorinated bisbenzil derivative analogues [Yamada, S. et al, Beilstein J. Org. Chem. 2020, 16, 1154–1162.]. To further understand their RTP properties, here we investigated the excited-state dynamics and photostability of the derivatives by means of time-resolved and steady-state photoluminescence spectroscopies. For these derivatives, clear RTP emissions with lifetimes on the microsecond timescale were identified. Among them, the monobenzil derivative was found to be the most efficient RTP material, showing both the longest lifetime and highest amplitude RTP emission. Time-resolved photoluminescence spectra measured at 77 K and density functional theory calculations revealed the existence of a second excited triplet state in the vicinity of the first excited singlet state for the monobenzil derivative, indicative of the presence of a fast intersystem crossing pathway. A discussion of the correlation between the excited state dynamics, emission properties, and conformational flexibility of the three derivatives is presented.

scholarly journals Excited State Dynamics of 8-Vinyldeoxyguanosine in Aqueous Solution Studied by Time-Resolved Fluorescence Spectroscopy and Quantum Mechanical Calculations

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 824
Author(s):  
Lara Martinez-Fernandez ◽  
Thomas Gustavsson ◽  
Ulf Diederichsen ◽  
Roberto Improta
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Radiative Decay ◽  
Decay Channel ◽  
Photophysical Properties ◽  
Time Resolved ◽  
Td Dft ◽  
Bonding Properties ◽  
Purine Ring ◽  
Vinyl Group

The fluorescent base guanine analog, 8-vinyl-deoxyguanosine (8vdG), is studied in solution using a combination of optical spectroscopies, notably femtosecond fluorescence upconversion and quantum chemical calculations, based on time-dependent density functional theory (TD-DFT) and including solvent effect by using a mixed discrete-continuum model. In all investigated solvents, the fluorescence is very long lived (3–4 ns), emanating from a stable excited state minimum with pronounced intramolecular charge-transfer character. The main non-radiative decay channel features a sizeable energy barrier and it is affected by the polarity and the H-bonding properties of the solvent. Calculations provide a picture of dynamical solvation effects fully consistent with the experimental results and show that the photophysical properties of 8vdG are modulated by the orientation of the vinyl group with respect to the purine ring, which in turn depends on the solvent. These findings may have importance for the understanding of the fluorescence properties of 8vdG when incorporated in a DNA helix.

Understanding the Excited State Photophysics of Pyrrolopyrrole-Dione Isomers and Derivatives Using Time-Dependence Density Functional Theory

2017 ◽  
Vol 05 (03) ◽  
pp. 1750009
Author(s):  
Teck Lip Dexter Tam ◽  
Ting Ting Lin ◽  
Steven Lukman
Keyword(s):  
Density Functional Theory ◽  
Photodynamic Therapy ◽  
Excited State ◽  
Time Dependence ◽  
Density Functional ◽  
Photophysical Properties ◽  
Cost Effective ◽  
Time Dependent ◽  
Functional Theory ◽  
Dependent Density

The ability to understand and predict excited state photophysics is vital for the development of photo- and electroluminescence materials, as well as light harvesting materials and photodynamic therapy. Herein, we demonstrate that single determinant time-dependent density functional theory can be computationally cost-effective and has the ability to explain both experimental singlet and triplet dynamics of pyrrolo[3,4-[Formula: see text]]pyrrole-1,4-dione and pyrrolo[3,2-b]pyrrole-2,5-dione isomers with intriguing photophysical properties. We also used the methodology to predict the photophysical properties of pyrrolo[3,4-c]pyrrole-1,3-dione and a hypothetical hybrid pyrrolo[3,4-b]pyrrole-2,4-dione isomers.

scholarly journals Benchmarking Density Functional Approximations for Excited-State Properties of Fluorescent Dyes

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7434
Author(s):  
Anna M. Grabarz ◽  
Borys Ośmiałowski
Keyword(s):  
Excited State ◽  
Density Functional ◽  
Fluorescent Dyes ◽  
Dipole Moments ◽  
Photophysical Properties ◽  
Excitation Energies ◽  
Data Set ◽  
Vertical Excitation ◽  
A Minor ◽  
Vertical Excitation Energies

This study presents an extensive analysis of the predictive power of time-dependent density functional theory in determining the excited-state properties of two groups of important fluorescent dyes, difluoroboranes and hydroxyphenylimidazo[1,2-a]pyridine derivatives. To ensure statistically meaningful results, the data set is comprised of 85 molecules manifesting diverse photophysical properties. The vertical excitation energies and dipole moments (in the electronic ground and excited states) of the aforementioned dyes were determined using the RI-CC2 method (reference) and with 18 density functional approximations (DFA). The set encompasses DFAs with varying amounts of exact exchange energy (EEX): from 0% (e.g., SVWN, BLYP), through a medium (e.g., TPSSh, B3LYP), up to a major contribution of EEX (e.g., BMK, MN15). It also includes range-separated hybrids (CAM-B3LYP, LC-BLYP). Similar error profiles of vertical energy were obtained for both dye groups, although the errors related to hydroxyphenylimidazopiridines are significantly larger. Overall, functionals including 40–55% of EEX (SOGGA11-X, BMK, M06-2X) ensure satisfactory agreement with the reference vertical excitation energies obtained using the RI-CC2 method; however, MN15 significantly outperforms them, providing a mean absolute error of merely 0.04 eV together with a very high correlation coefficient (R2 = 0.98). Within the investigated set of functionals, there is no single functional that would equally accurately determine ground- and excited-state dipole moments of difluoroboranes and hydroxyphenylimidazopiridine derivatives. Depending on the chosen set of dyes, the most accurate μGS predictions were delivered by MN15 incorporating a major EEX contribution (difluoroboranes) and by PBE0 containing a minor EEX fraction (hydroxyphenylimidazopiridines). Reverse trends are observed for μES, i.e., for difluoroboranes the best results were obtained with functionals including a minor fraction of EEX, specifically PBE0, while in the case of hydroxyphenylimidazopiridines, much more accurate predictions were provided by functionals incorporating a major EEX contribution (BMK, MN15).

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