A series of [Re-2(mu-ER)(2)(CO)(6)(mu-pydz)] complexes have been synthesized (E = S, R = C6H5, 2; E = O, R = C6F5, 3; C6H5, 4; CH3, and 5; H, 6), starting either from [Re(CO)(5)O3SCF3] (for 2 and 4), [Re-2(mu-OR)(3)(CO)(6)](-) (for 3 and 5), or [Re-4(mu(3)-OH)(4)(CO)(12)] (for 6). Single-crystal diffractometric analysis showed that the two mu-phenolato derivatives (3 and 4) possess an idealized C-2 symmetry, while the mu-benzenethiolato derivative (2) is asymmetrical, because of the different conformation adopted by the phenyl groups. A combined density functional and time-dependent density functional study of the geometry and electronic structure of the complexes showed that the lowest unoccupied molecular orbital (LUMO) and LUMO +1 are the two lowest-lying pi* orbitals of pyridazine, whereas the highest occupied molecular orbitals (HOMOs) are mainly constituted by the "t(2g)" set of the Re atoms, with a strong Re-(mu-E) pi* character. The absorption spectra have been satisfactorily simulated, by computing the lowest singlet excitation energies. All the complexes exhibit one reversible monoelectronic reduction centered on the pyridazine ligand (ranging from -1.35 V to -1.53 V vs Fc(+)lFc). The benzenethiolato derivative 2 exhibits one reversible two-electron oxidation (at 0.47 V), whereas the OR derivatives show two close monoelectronic oxidation peaks (ranging from 0.85 V to 1.35 V for the first peak). The thioderivative 2 exhibits a very small electrochemical energy gap (1.9 eV, vs 2.38-2.70 eV for the OR derivatives), and it does not show any photoluminescence. The complexes containing OR ligands show from moderate to poor photoluminescence, in the range of 608-708 nm, with quantum yields decreasing (ranging from 5.5% to 0.07%) and lifetimes decreasing (ranging from 550 ns to 9 ns) (3 > 4 > 6 approximate to 5) with increasing emission wavelength. The best emitting properties, which are closely comparable to those of the dichloro complex (1), are exhibited by the pentafluorophenolato derivative (3).

Electrochemical, computational, and photophysical characterization of new luminescent dirhenium-pyridazine complexes containing bridging OR or SR anions / A. Raimondi, M. Panigati, D. Maggioni, L. D'Alfonso, P. Mercandelli, P. Mussini, G. D'Alfonso. - In: INORGANIC CHEMISTRY. - ISSN 0020-1669. - 51:5(2012), pp. 2966-2975.

Electrochemical, computational, and photophysical characterization of new luminescent dirhenium-pyridazine complexes containing bridging OR or SR anions

A. Raimondi
Primo
;
M. Panigati
Secondo
;
D. Maggioni;P. Mercandelli;P. Mussini
Penultimo
;
G. D'Alfonso
Ultimo
2012

Abstract

A series of [Re-2(mu-ER)(2)(CO)(6)(mu-pydz)] complexes have been synthesized (E = S, R = C6H5, 2; E = O, R = C6F5, 3; C6H5, 4; CH3, and 5; H, 6), starting either from [Re(CO)(5)O3SCF3] (for 2 and 4), [Re-2(mu-OR)(3)(CO)(6)](-) (for 3 and 5), or [Re-4(mu(3)-OH)(4)(CO)(12)] (for 6). Single-crystal diffractometric analysis showed that the two mu-phenolato derivatives (3 and 4) possess an idealized C-2 symmetry, while the mu-benzenethiolato derivative (2) is asymmetrical, because of the different conformation adopted by the phenyl groups. A combined density functional and time-dependent density functional study of the geometry and electronic structure of the complexes showed that the lowest unoccupied molecular orbital (LUMO) and LUMO +1 are the two lowest-lying pi* orbitals of pyridazine, whereas the highest occupied molecular orbitals (HOMOs) are mainly constituted by the "t(2g)" set of the Re atoms, with a strong Re-(mu-E) pi* character. The absorption spectra have been satisfactorily simulated, by computing the lowest singlet excitation energies. All the complexes exhibit one reversible monoelectronic reduction centered on the pyridazine ligand (ranging from -1.35 V to -1.53 V vs Fc(+)lFc). The benzenethiolato derivative 2 exhibits one reversible two-electron oxidation (at 0.47 V), whereas the OR derivatives show two close monoelectronic oxidation peaks (ranging from 0.85 V to 1.35 V for the first peak). The thioderivative 2 exhibits a very small electrochemical energy gap (1.9 eV, vs 2.38-2.70 eV for the OR derivatives), and it does not show any photoluminescence. The complexes containing OR ligands show from moderate to poor photoluminescence, in the range of 608-708 nm, with quantum yields decreasing (ranging from 5.5% to 0.07%) and lifetimes decreasing (ranging from 550 ns to 9 ns) (3 > 4 > 6 approximate to 5) with increasing emission wavelength. The best emitting properties, which are closely comparable to those of the dichloro complex (1), are exhibited by the pentafluorophenolato derivative (3).
Settore CHIM/03 - Chimica Generale e Inorganica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/190862
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