Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Complexes of NiII, CuII, ZnII, and CoIII containing the 1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide (L) and the 2,4-tert-butylacetylacetonide (DPM) ligands have been synthesized and characterized. The absorption optical spectra of these species and of the corresponding ML2 complexes in coordinating solvents are compared with those of metal-phthalocyanines (MPc) and hydrogen-phthalocyanine (H2Pc), respectively. The comparison shows a close similarity, especially for the nickel-containing species, in the low-energy spectral region where the first π→π* transitions occur (Q band). The Q band position of the pyrrolizinato complexes is much more dependant on the metal than is the case for MPc. For the same metal, the Q band position is also dependant on the M-N bond lengths in the molecular plane. For M = Ni, a reduction of this distance causes a red-shift of the Q band and a decrease of its maximum intensity. These conclusions are based on the X-ray molecular structure of the solvent-free NiL(DPM) complex and its pyridine solvate NiL(DPM)(Pyr)2 · 2 Pyr and on their solvatochromism. A symmetry-based correlation diagram between the frontier orbitals of the pyrrolizinato-complexes and the phthalocyanines is proposed.
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