Substituent effects on the photophysical properties of 2,9‐substituted phenanthroline copper(I) complexes: a theoretical investigation

The electronic and nuclear structures of a series of [Cu(2,9‐(X)2‐phen)2]+ copper(I) complexes (phen=1,10‐phenanthroline; X=H, F, Cl, Br, I, Me, CN) in their ground and excited states are investigated by means of density functional theory (DFT) and time‐dependent (TD‐DFT) methods. Subsequent Born‐Op...

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Vydáno v:Chemphyschem Ročník 22; číslo 5; s. 509 - 515
Hlavní autoři: Gourlaouen, Christophe, Hamano, Ai, Takano, Keiko, Daniel, Chantal
Médium: Journal Article
Jazyk:angličtina
Vydáno: Germany Wiley Subscription Services, Inc 03.03.2021
Wiley-VCH Verlag
Témata:
Asymmetry
Broken symmetry
Charge transfer
Chemical Sciences
Coordination chemistry
Coordination compounds
Copper
Copper compounds
copper(I) phenanthroline
Density functional theory
Energy
excited-state structure
Flattening
free-energy profile
Ligands
Molecular dynamics
or physical chemistry
Potential energy
substituent effects
Theoretical and
free-energy profile
copper(I) phenanthroline
substituent effects
excited-state structure
density functional theory
ISSN:1439-4235, 1439-7641, 1439-7641
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Popis
Shrnutí:The electronic and nuclear structures of a series of [Cu(2,9‐(X)2‐phen)2]+ copper(I) complexes (phen=1,10‐phenanthroline; X=H, F, Cl, Br, I, Me, CN) in their ground and excited states are investigated by means of density functional theory (DFT) and time‐dependent (TD‐DFT) methods. Subsequent Born‐Oppenheimer molecular dynamics is used for exploring the T1 potential energy surface (PES). The T1 and S1 energy profiles, which connect the degenerate minima induced by ligand flattening and Cu−N bond symmetry breaking when exciting the molecule are calculated as well as transition state (TS) structures and related energy barriers. Three nuclear motions drive the photophysics, namely the coordination sphere asymmetric breathing, the well‐documented pseudo Jahn‐Teller (PJT) distortion and the bending of the phen ligands. This theoretical study reveals the limit of the static picture based on potential energy surfaces minima and transition states for interpreting the luminescent and TADF properties of this class of molecules. Whereas minor asymmetric Cu−N bonds breathing accompanies the metal‐to‐ligand‐charge‐transfer re‐localization over one or the other phen ligand, the three nuclear movements participate to the flattening of the electronically excited complexes. This leads to negligible energy barriers whatever the ligand X for the first process and significant ligand dependent energy barriers for the formation of the flattened conformers. Born‐Oppenheimer (BO) dynamics simulation of the structural evolution on the T1 PES over 11 ps at 300 K confirms the fast backwards and forwards motion of the phenanthroline within 200–300 fs period and corroborates the presence of metastable C2 structures. The over picosecond timescale photophysics of a series of copper(I) X‐substituted phenanthroline complexes is interpreted on the basis of Gibbs free energy and potential energy profiles of the lowest S1 and T1 electronic excited states. Born‐Oppenheimer dynamics over 10 ps evidence the backwards and forwards motion of the phenanthroline ligands within a period of 200–300 fs.
Bibliografie:This article is dedicated to the scientific career of our colleague Dr. Olivier Poizat, CNRS researcher, for his outstanding contribution to excited‐state relaxation dynamics.
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ISSN:1439-4235
1439-7641
1439-7641
DOI:10.1002/cphc.202000868