This paper reports on chemical and spectral studies of the macrocyclic uranyl complexes dioxocyclopentakis (l-imi-noisoindolinato) uranium (VI), SPCUO2, and dioxocyclopentakis (l-imino-5-methylisoindolinato) uranium (VI), MesSPcUO2. These expanded, five-subunit analogues of phthalocyanines were synthesized in template reactions from uranyl salts and the corresponding phthalonitriles. The conditions for a high-yield synthesis are critical and include a polar solvent (e. g., dimethylformamide), high temperatures, and strict exclusion of water. Phthalocyanine, PcH2, is a side product of the reaction with the source of protons being the solvent. Attempts to displace the uranyl ion from SPcU02 with acids or other metal ions (Mn+) invariably result in macrocycle contraction to produce PcH2 or PcMn-2and phthalonitrile. 1H NMR studies reveal the five-subunit macrocycle to be stereochemically dynamic. The analysis of ring current induced 1H N MR shifts indicates considerably reduced π electron derealization in SPcUO2 compared to PcM derivatives. The electronic spectrum of SPcUO2 exhibits strong absorption maxima at 4240 and 9140 A. With the aid of Pariser-Parr-Pople SCF LCAO CI tt electron molecular orbital calculations, the electronic structure of the macrocycle and the origin of the spectral transitions can be shown to be closely analogous to phthalocyanine systems. Many of the chemical and spectral properties of SPcUO2 and Me5SPcUO2 reflect the severe buckling and strain within the macrocyclic ligand.
ASJC Scopus subject areas
- Colloid and Surface Chemistry