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Origin of the Photoinduced Geometrical Change of Copper(I) Complexes from the Quantum Chemical Topology View
Author(s) -
GutiérrezArzaluz Luis,
RamírezPalma David Ignacio,
RamírezPalma Lillian G.,
BarqueraLozada José Enrique,
Peon Jorge,
CortésGuzmán Fernando
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201804596
Subject(s) - chemistry , chemical physics , excited state , metal , atomic physics , copper , valence (chemistry) , electron transfer , electron , photoexcitation , ligand field theory , molecular physics , photochemistry , physics , ion , organic chemistry , quantum mechanics
Copper(I) complexes (CICs) are of great interest due to their applications as redox mediators and molecular switches. CICs present drastic geometrical change in their excited states, which interferes with their luminescence properties. The photophysical process has been extensively studied by several time‐resolved methods to gain an understanding of the dynamics and mechanism of the torsion, which has been explained in terms of a Jahn–Teller effect. Here, we propose an alternative explanation for the photoinduced structural change of CICs, based on electron density redistribution. After photoexcitation of a CIC (S 0 →S 1 ), a metal‐to‐ligand charge transfer stabilizes the ligand and destabilizes the metal. A subsequent electron transfer, through an intersystem crossing process, followed by an internal conversion (S 1 →T 2 →T 1 ), intensifies the energetic differences between the metal and ligand within the complex. The energy profile of each state is the result of the balance between metal and ligand energy changes. The loss of electrons originates an increase in the attractive potential energy within the copper basin, which is not compensated by the associated reduction of the repulsive atomic potential. To counterbalance the atomic destabilization, the valence shell of the copper center is polarized (defined by ∇ 2 ρ ( r ) and ∇ 2 V ne ( r )) during the deactivation path. This polarization increases the magnitude of the intra‐atomic nuclear–electron interactions within the copper atom and provokes the flattening of the structure to obtain the geometry with the maximum interaction between the charge depletions of the metal and the charge concentrations of the ligand.