| Résumé | Nonlocal hybrid density functional theory method is used to study the structure and force field of the copper(I)�diphenanthroline cation. It is demonstrated that it possesses D2d symmetry in the S0 state, however, deformations to D2 symmetry with rotated phenanthroline rings are not costly energetically and, in fact, such D2 structure is the minimum of the T1 state. Time-dependent DFT method is utilized to calculate the excited electronic states and the visible and UV absorption spectrum. It is shown that the S3 state of B2 symmetry and of metal-to-ligand charge transfer (MLCT) character, is responsible for the ca. 470 nm visible absorption band, while dipole transitions to the S1 and S2 states are symmetry forbidden. We find four triplet electronic states closely spaced and lying just below the S1 state. The ordering and spacing of the lowest triplet and singlet excited states nicely explains the properties of the observed photoluminescence. The calculated maximum of photoluminescence of 759 nm is in a good agreement with the experiment (ca. 730 nm). |
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