Taming the excited state reactivity of imines – from non-radiative decay to aza Paternò–Büchi reaction

2021 ◽  
Author(s):  
Sunil Kumar Kandappa ◽  
Lakshmy Kannadi Valloli ◽  
Sapna Ahuja ◽  
Jayachandran Parthiban ◽  
J. Sivaguru
Keyword(s):  
Excited State ◽  
Radiative Decay ◽  
Photophysical Properties

This review highlights the excited state characteristics of imines and processes that govern their photochemical and photophysical properties.

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.

scholarly journals Theoretical studies on the photophysical properties of luminescent pincer gold(iii) arylacetylide complexes: the role of π-conjugation at the C-deprotonated [C^N^C] ligand

2015 ◽  
Vol 6 (5) ◽  
pp. 3026-3037 ◽  
Author(s):  
Glenna So Ming Tong ◽  
Kaai Tung Chan ◽  
Xiaoyong Chang ◽  
Chi-Ming Che
Keyword(s):  
Excited State ◽  
Radiative Decay ◽  
Photophysical Properties ◽  
Theoretical Studies

The facile non-radiative decay for gold(iii) complexes is due to the thermally accessible3LLCT, but not the usually assumed3dd excited state.

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 Studies on Photophysical Properties of Mono-carbonyl Curcumin Analogues: Experimental and Theoretical approach

2018 ◽  
Vol 34 (4) ◽  
pp. 2170-2179
Author(s):  
Manjula Rayanal ◽  
Prasad Pralhad Pujar ◽  
Sridhar D
Keyword(s):  
Excited State ◽  
Ground State ◽  
Dipole Moments ◽  
Photophysical Properties ◽  
Stokes Shift ◽  
Solvent Polarity ◽  
Frontier Molecular Orbital ◽  
Curcumin Analogues ◽  
Td Dft ◽  
Ground State Dipole Moments

The solvatochromic fluorescence behaviour of mono-carbonyl curcumin analogues has been studied in ten different solvents ranging from non-polar to polar. The solvent effect on the spectral properties of analogues has been discussed. The ground state dipole moments were estimated experimentally by Bilot-Kawski equation which is a function of Stokes shift with the solvent polarity parameters and Guggenheim method and theoretically by TD-DFT studies. The excited state dipole moment was determined using Bilot-Kawski equations. The excited state dipole moments for the two molecules were found to be higher than their corresponding ground state dipole moments. Theoretically Frontier molecular orbital (HOMO/ LUMO) energies were determined by Gaussian 09 W software using TD-DFT.

Effect of number and different types of proton donors on excited-state intramolecular single and double proton transfer in bipyridine derivatives: theoretical insights

2020 ◽  
Vol 44 (19) ◽  
pp. 8018-8031
Author(s):  
Komsun Chaihan ◽  
Nawee Kungwan
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Vibrational Mode ◽  
Photophysical Properties ◽  
Reaction Energy ◽  
Topology Analysis ◽  
Double Proton Transfer ◽  
And Topology ◽  
Proton Donors ◽  
Different Types

Intra-HBs are strengthened upon photoexcitation, confirmed by red-shift in vibrational mode and topology analysis. Number and type of donors result in difference in photophysical properties. Occurrence of ESIPT depends on barrier and reaction energy.

scholarly journals Photophysical Properties of Spirobifluorene-Based o-Carboranyl Compounds Altered by Structurally Rotating the Carborane Cages

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4135
Author(s):  
Seonah Kim ◽  
Hyunhee So ◽  
Ji Hye Lee ◽  
Hyonseok Hwang ◽  
Hyoshik Kwon ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Photophysical Properties ◽  
High Energy ◽  
Low Energy ◽  
Radiative Decays ◽  
Absorption Bands ◽  
Molecular Features ◽  
Td Dft ◽  
Structural Fluctuations ◽  
Energy Emissions

9,9′-Spirobifluorene-based o-carboranyl compounds C1 and C2 were prepared and fully characterized by multinuclear nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The solid-state structure of C1 was also determined by single-crystal X-ray diffractometry. The two carboranyl compounds display major absorption bands that are assigned to π−π* transitions involving their spirobifluorene groups, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene groups. While C1 only exhibited high-energy emissions (λem = ca. 350 nm) in THF at 298 K due to locally excited (LE) states assignable to π−π* transitions involving the spirobifluorene group alone, a remarkable emission in the low-energy region was observed in the rigid state, such as in THF at 77 K or the film state. Furthermore, C2 displays intense dual emissive patterns in both high- and low-energy regions in all states. Electronic transitions that were calculated by time-dependent-DFT (TD-DFT) for each compound based on ground (S0) and first-excited (S1) state optimized structures clearly verify that the low-energy emissions are due to ICT-based radiative decays. Calculated energy barriers that are based on the relative energies associated with changes in the dihedral angle around the o-carborane cages in C1 and C2 clearly reveal that the o-carborane cage in C1 rotates more freely than that in C2. All of the molecular features indicate that ICT-based radiative decay is only available to the rigid state in the absence of structural fluctuations, in particular the free-rotation of the o-carborane cage.

An oxygen-bridged triarylamine polycyclic unit based tris-cyclometalated heteroleptic iridium(iii) complex: correlation between the structure and photophysical properties

2019 ◽  
Vol 48 (14) ◽  
pp. 4596-4601 ◽  
Author(s):  
Qiuxia Li ◽  
Xinghua Zhang ◽  
Yibo Cao ◽  
Chao Shi ◽  
Peng Tao ◽  
...  
Keyword(s):  
Excited State ◽  
Photophysical Properties ◽  
Complex Correlation

A novel oxygen-bridged triarylamine polycyclic based tris-cyclometalated heteroleptic iridium(iii) complex has been prepared and shows unusual excited state properties.

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