Narrow Results

The spectra of porphyrins meso-substituted by 4-dimethylaminophenyl groups and protonated at the central pyrrole nitrogens show strong new bands in the visible (450–600 nm) and far-red (700–780 nm). On complete protonation the observed spectra are essentially normal except for enhanced intensity in the farthest red band at ∼ 650 nm. The new bands observed with partial protonation have been qualitatively interpreted as hyperporphyrin spectra due to transitions from 'the filled π orbitals on the amino nitrogen atoms… to the porphyrin LUMOs' [Ojadi ECA, Linschitz M, Gouterman M, Walter RI, Lindsey JS, Wagner RW,]. We now report spectra calculated using the CAChe computer program package. The best structures are determined by energy minimization using a semi-empiral AM1 algorithm; a semi-empirical INDO/CI calculation is then used to obtained the excited state transition energies and intensities. The calculated spectra, although generally blue-shifted compared to experiment, reproduce the hyperporphyrin spectra in those cases where they are observed. In these cases, in contrast to species with normal porphyrin spectra, the HOMO or HOMO-1 is not an orbital on the porphyrin ring but is rather a π-orbital on the unprotonated amino nitrogen that extends over the associated phenyl ring. The calculations suggest that the hyperporphyrin transitions are of Ph(π) → Por(π*) origin, where Ph(π) is an orbital on the phenylamine substitutent and Por(π*) is a LUMO on the porphyrin. It is further suggested that in the fully protonated species the intensity enhancement of the farthest red band in an otherwise normal porphyrin spectrum may relate to phenyl character in the HOMO or HOMO-1.

Oxoferryl porphyrin π-cation radical active sites of compound I intermediates which are found in enzymes such as peroxidases and catalases have been extensively modeled by oxidized synthetic metalloporphyrins. The electronic symmetry states of these compounds were initially assigned on the basis of electronic absorption data. In recent years new experimental and theoretical results have become available which have led to a re-evaluation and modification of the original assignments. A historical perspective of these developments is provided in the context of recent NMR, resonance Raman, and other spectroscopic data and theoretical calculations for the synthetic models and enzymatic systems.

In a terminating band, the nucleon number changes in a specific orbital not only lead to deformation changes of the band but also the type of the band termination is impressed. In this work, we consider the role of the orbitals near the Fermi surface in some of the nuclei with $A\sim 160$; such as Dy ($Z=66$), Ho ($Z=67$) and Er ($Z=68$) isotopes. Our results show that the contribution of the number of the proton holes in the core is very effective to energy cost at the end of the rotational bands and then, termination type. Change the number of the protons on high-$j$ orbitals ($h_{11/2}$) in $N=88$ isotones and also, the neutrons on high-$j$$i_{13/2}$ and low-$j$$f_{7/2}{h}_{9/2}$ neutron orbitals do not affect in the type of termination. They cause only to move up or down the terminating bands in energy.