Temperature Dependent Emission Properties of Rhenium(I) Tricarbonyl Complexes Containing Alkyl- and Aryl-Substituted Phenanthrolines as Ligands

Abstract

The results of the temperature dependence in fluid solution of the emission behavior of a series of [Re(L-L)-(CO)3py]+ complexes 4,7, 4, 2, 4', 5, 2, and phen) are presented along with an interpretation which assigns the lowest excited state as 3MLCT, with a contribution from a higher-energy, shorter-lived state of unknown character. The emission lifetime of [Re(3,4,7,8-Me4phen)(C0)3py]+ actually increases with temperature, reaches a maximum at approximately 230 K, and then decreases in the usual manner. This behavior is attributed to population of the lowest 3LC state, which in this complex lies just above the 3MLCT emitting state and below the upper state.

Electronic absorption, resonance Raman and excited-state resonance Raman spectroscopy of rhenium(I) and copper(I) complexes, with substituted dipyrido[3,2-a : 2′,3′-c]phenazine ligands, and their electron reduced products

“…51 By considering the emission and ESRR data it is possible to obtain a clearer picture of the formulation of the excited state present 5 ns after laser excitation.…”

Relativistic effects in spectroscopy and photophysics of heavy-metal complexes illustrated by spin–orbit calculations of [Re(imidazole)(CO)3(phen)]+

“…All other values as in Table 2 (i) The major TRIR feature corresponds to the aA and bA states, whereas the "minor" one is due to the third state cA . The expected population ratio ( fourth state bA provides the thermally activated decay pathway, ubiquitous in Re I carbonyl diimines [81,82]. However, this interpretation does not explain why the IR spectra of the "minor" and "major" states are so different [14].…”

Synthesis, characterization, photophysical and electrochemical properties of fac-tricarbonyl(4,7-dichloro-1,10-phenanthroline)rhenium(I) complexes

“…Additionally, intense effort has been dedicated to better understand the effect of the position and attachment of electron withdrawing/donating groups to ligands on the mechanistic events after excitation 15,[17][18][19][20][21] , which can contribute to a deeper comprehension of their emissive properties. For instance, electron withdrawing groups attached to polypyridyl ligands promote stabilization of 3 MLCT Re→NN excited state energy level (metal-to-ligand charge-transfer) 15,17,19,[21][22][23][24] . On the other hand, electron donating groups, such as methyl, promote destabilization of 3 MLCT Re→NN excited state energy level and at the same time reduces the energy of ligand-centered excited state, 3 IL NN 19,21,23 .…”

“…For instance, electron withdrawing groups attached to polypyridyl ligands promote stabilization of 3 MLCT Re→NN excited state energy level (metal-to-ligand charge-transfer) 15,17,19,[21][22][23][24] . On the other hand, electron donating groups, such as methyl, promote destabilization of 3 MLCT Re→NN excited state energy level and at the same time reduces the energy of ligand-centered excited state, 3 IL NN 19,21,23 . The rhenium polypyridyl complexes show a dominant 3 MLCT emission, but some 3 IL character could be also evident to a lesser or greater degree, depending on the coordinated NN ligand.…”