Excited-state relaxation dynamics of Re(I) tricarbonyl complexes with macrocyclic phenanthroline ligands studied by time-resolved IR spectroscopy

Two sets of supramolecular rhenium carbonyl-phenanthroline complexes were prepared: fac-[Re(Cl)(CO)(3)(N,N)] and fac-[Re(Etpy)(CO)(3)(N,N)](+), where N,N is 2,9-di-anisyl-1,10-phenanthroline (dap) or two related macrocyclic ligands, where the two anisyl groups are connected by a polyether chain of d...

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Vydané v:Dalton transactions : an international journal of inorganic chemistry číslo 20; s. 3941
Hlavní autori: Blanco-Rodríguez, Ana María, Towrie, Michael, Collin, Jean-Paul, Zális, Stanislav, Vlcek, Antonín
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: England 01.01.2009
Predmet:
Ligands
Macrocyclic Compounds - chemistry
Molecular Structure
Phenanthrolines - chemistry
Quantum Theory
Rhenium - chemistry
Spectrophotometry, Infrared
ISSN:1477-9226
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Shrnutí:Two sets of supramolecular rhenium carbonyl-phenanthroline complexes were prepared: fac-[Re(Cl)(CO)(3)(N,N)] and fac-[Re(Etpy)(CO)(3)(N,N)](+), where N,N is 2,9-di-anisyl-1,10-phenanthroline (dap) or two related macrocyclic ligands, where the two anisyl groups are connected by a polyether chain of different length and rigidity (m27, m30), which wraps around and above the equatorial Re(CO)(2) group. The excited-state character and relaxation dynamics of these complexes were investigated by picosecond time-resolved IR spectroscopy in the spectral region of C[triple bond, length as m-dash]O stretching vibrations, nu(CO). The results were interpreted with the aid of DFT and TD-DFT calculations of the molecular structures and electron-density redistribution upon excitation. [Re(Cl)(CO)(3)(phen-macrocycle)] in CH(2)Cl(2) have the same type of lowest excited state as analogous acyclic phen or bpy complexes, that is a mixed Re(CO)(3)-->phen and Cl-->phen MLCT/XLCT, together with some pipi*(phen) IL character. Its relaxation dynamics are qualitatively similar to those of phen or bpy complexes. However, relaxation of [Re(Cl)(CO)(3)(m30)] shows a slow kinetics component ( approximately 22 ps) which arises from confined local solvent molecules and/or from conformational movements of the flexible m30 polyether ring. In contrast, attaching anisyl groups at the 2 and 9 phen positions in [Re(Etpy)(CO)(3)(phen-macrocycle)](+) effectively "freezes" excited-state relaxation in MeCN, regardless of the presence of the macrocyclic ring. The lowest excited triplet state has a mixed MLCT/IL character. Restricting the solvent access to the excited chromophore clearly affects both the character and dynamics of the lowest excited state.
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ISSN:1477-9226
DOI:10.1039/b820748h