1 research outputs found
Comparison of Inverse and Regular 2‑Pyridyl-1,2,3-triazole “Click” Complexes: Structures, Stability, Electrochemical, and Photophysical Properties
Two inverse 2-pyridyl-1,2,3-triazole
“click” ligands, 2-(4-phenyl-1<i>H</i>-1,2,3-triazol-1-yl)Âpyridine
and 2-(4-benzyl-1<i>H</i>-1,2,3-triazol-1-yl)Âpyridine, and
their palladiumÂ(II), platinumÂ(II), rheniumÂ(I), and rutheniumÂ(II) complexes
have been synthesized in good to excellent yields. The properties
of these inverse “click” complexes have been compared
to the isomeric regular compounds using a variety of techniques. X-ray
crystallographic analysis shows that the regular and inverse complexes
are structurally very similar. However, the chemical and physical
properties of the isomers are quite different. Ligand exchange studies
and density functional theory (DFT) calculations indicate that metal
complexes of the regular 2-(1-<b>R</b>-1<i>H</i>-1,2,3-triazol-4-yl)Âpyridine
(<b>R</b> = phenyl, benzyl) ligands are more stable than those
formed with the inverse 2-(4-<b>R</b>-1<i>H</i>-1,2,3-triazol-1-yl)Âpyridine
(<b>R</b> = phenyl, benzyl) “click” chelators.
Additionally, the <i>bis</i>-2,2′-bipyridine (bpy)
rutheniumÂ(II) complexes of the “click” chelators have
been shown to have short excited state lifetimes, which in the inverse
triazole case, resulted in ejection of the 2-pyridyl-1,2,3-triazole
ligand from the complex. Under identical conditions, the isomeric
regular 2-pyridyl-1,2,3-triazole rutheniumÂ(II) bpy complexes are photochemically
inert. The absorption spectra of the inverse rheniumÂ(I) and platinumÂ(II)
complexes are red-shifted compared to the regular compounds. It is
shown that conjugation between the substituent group <b>R</b> and triazolyl unit has a negligible effect on the photophysical
properties of the complexes. The inverse rheniumÂ(I) complexes have
large Stokes shifts, long metal-to-ligand charge transfer (MLCT) excited
state lifetimes, and respectable quantum yields which are relatively
solvent insensitive