During the synthesis of 1,10‐phenanthroline derivatives sterically hindered in the 2 and/or 9 positions, serendipity led to the discovery of a new substitution pattern on phenanthroline with good and reproducible yields. When toluene was used as a solvent and the aryl‐lithio reagents generated with tBuLi, after a first substitution at the 2 position, a benzyl substituent was regioselectively introduced at the 7 position. It is proposed that the benzyllithium reagent is formed by reaction with the solvent and that the steric hindrance on the intermediates controls the nucleophilic addition. Among the complexes prepared (Pd(II), Cu(I)) with these new ligands, a chiral copper(I) complex exhibits spontaneous resolution in the solid state.
In this study, a series of new heteroleptic copper(I) bis(diimine) complexes are described. Using one highly hindered phenanthroline ligand and a second less-hindered diimine ligand led to unexpected results. Following a two-step one-pot method to obtain heteroleptic copper(I) complexes, an almost perfect tetrahedral coordination geometry around the copper(I) ion was obtained in several cases, despite the fact that at least one ligand was not sterically encumbered near the coordination site (at the position α to the nitrogen atoms of the ligand). This was demonstrated in the solid state by resolution of crystal structures, and these findings, corroborated by calculations, showed that the non-covalent interactions between the two diimine ligands present in these complexes were governing these structural features. The electronic properties of all complexes were also determined and the fluorescence lifetimes of two complexes were compared.
We report the synthesis of new vanadyl porphyrins bearing
peripheral
coordination sites. By using palladium(II) or platinum(II) as connecting
ions, porphyrin dimers were isolated and characterized by X-ray crystallography.
These paramagnetic species were studied by electronic spectroscopy
and continuous wave electron paramagnetic resonance (CW EPR). Large
bathochromic shifts were observed by comparing porphyrin monomers
and dimers showing that electronic delocalization was present as demonstrated
earlier for diamagnetic compounds. Despite the large distance (>14
Å) between the two vanadyl centers in these dimers, small dipolar
interactions between the two paramagnetic ions could be determined.
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