CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
Solvent effects on the photophysical properties of Bu4N[(4,4′-bpy)Re(CO)3(bpy-5,5′-diCOO)] complex. A combined experimental and computational study
HECTOR H. MARTINEZ SAAVEDRA; FABRICIO RAGONE; CARLOS A. FRANCA; GUSTAVO T. RUIZ; PEDRO M. DAVID GARA; EZEQUIEL WOLCAN
JOURNAL OF ORGANOMETALLIC CHEMISTRY
ELSEVIER SCIENCE SA
Lugar: Amsterdam; Año: 2016 vol. 817 p. 26 - 26
The photophysical properties of the complex Bu4N[(4,4´-bpy)Re(CO)3(bpy-5,5´-diCOO)] were studied in protic and aprotic media with the aid of steady-state and time-resolved techniques and TD-DFT calculations. The absorption spectrum as well as the steady state and time resolved luminescence of the Re(I) complex display a marked solvent effect. The highest and lowest energy absorption bandsexperience a bathochromic shift as the polarity of the solvent decreases. In addition, the lowest energy band broadens. Two luminescence bands were observed around 430 and 600 nm in protic organic solvents like alcohols. The high energy emission is observed solely in aqueous solutions, while in aprotic solvents only the low energy luminescence is detected. TD-DFT calculations allowed us toidentify the main electronic transitions in the low energy region as 1MLLCTRe(CO)3®4,4´-bpy and 1MLLCTRe(CO)3®bpy-5,5´-diCOO. The simulated absorption spectra of the Re(I) complex in H2O, protic (EtOH, MeOH) and aprotic (CHCl3, CH2Cl2, CH3CN) organic solvents follow the experimental absorption spectra with reasonable accuracy both in position and relative intensities. The magnitude of the calculated dipole moment (m) increases with the dielectric constant of the solvent (er). Besides, the energy of 1MLLCTRe(CO)3®4,4´-bpy also increases with er. However, the energy of the 1MLLCTRe(CO)3®bpy-5,5´-diCOO transition is rather insensitive to er. This disparity is attributed to the fact that the 1MLLCTRe(CO)3®4,4´-bpy transition is nearly parallel to the orientation of m while the 1MLLCTRe(CO)3®bpy-5,5´-diCOO transition is almost perpendicular to it. Unrestricted TD-DFT calculations were successfullyapplied to the triplet species. It is observed that in the triplet state the Re-N distances are shortened while Re-C distances are elongated relative to the ground state. The calculated emission energy by TDDFT and/or D(SCF) methods was compared to the experimental emission maximum in chloroform. All the experimental results as well as the theoretical calculations indicate that solvent effects on the steadystate and time resolved luminescence of the Re(I) complex can be accounted by the coexistence of 3MLLCTRe(CO)3®4,4´-bpy, 3MLLCTRe(CO)3®bpy-5,5´-diCOO and 1IL excited states.