Electronic and resonance Raman spectra of iron(II)—tetraazamacrocyclic complexes containing N-heterocyclic ligands

✍ Scribed by Henrique E. Toma; Eduardo Stadler; Paulo S. Santos

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 378 KB
• Volume: 44
• Category: Article
• ISSN: 1386-1425
• DOI: 10.1016/0584-8539(88)80183-1

✦ Synopsis

The adducts of the meso-5,5,7,12,12,14-hexamethyl-1,4,8,1 1-tetraazacyclotetradeca-1,4,8,1 ltetraene iron(H) complex with N-heterocyclic ligands exhibit three characteristic absorption bands in the ranges 690-640, 505470 and 435-340 nm. Using excitation wavelengths coinciding with the low energy band, a selective enhancement of the Raman vibrational modes of the macrocyclic ligand is observed, supporting the assignment of a metal-to-diimine charge-transfer transition. The high energy band is strongly dependent on the nature and pK, of the axial ligands. Excitation at this band leads to the enhancement of the N-heterocyclic vibrational modes in the Raman spectra, indicating a metal-to-(N-heterocycle) chargetransfer transition. The intermediate band exhibits weak resonance Raman activity. Its intensity depends on the proximity of the high energy band and is consistent with the occurrence of an intensity stealing mechanism.