title: Structural and vibrational properties of tetraoxaporphyrin dication, the oxygen analogue of porphyrin, and of isoelectronic diprotonated porphyrin.
abstract: Structural calculations by means of the density functional method have been performed on tetraoxaporphyrin dication and on isoelectronic diprotonated porphyrin as well as on the sulfur and carbon analogues of porphyrin. A detailed study of the stable conformations of these compounds is reported starting with the most symmetrical conformations and lowering the symmetry along the vibrational coordinates with imaginary frequency. The calculated geometries are related to experimental structures available from X-ray diffraction studies. The Raman spectra of tetraoxaporphyrin dication exciting with micro-Raman instrumentation at 785 nm and of diprotonated porphyrin in near-resonance conditions with the Soret band have been measured. The correlation between frequencies calculated with the DF/B3-LYP/cc-pVDZ procedure for porphyrin, diprotonated porphyrin, and tetraoxaporphyrin dication has allowed for making a vibrational assignment for the latter two systems in excellent agreement with experiment using a single frequency scale factor.
authors.affiliation: Dipartimento di Chimica, Universita di Firenze, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
authors.forename: Ivana
authors.initials: I
authors.lastname: Jelovica
authors.forename: Laura
authors.initials: L
authors.lastname: Moroni
authors.forename: Cristina
authors.initials: C
authors.lastname: Gellini
authors.forename: Pier Remigio
authors.initials: PR
authors.lastname: Salvi
authors.forename: Nada
authors.initials: N
authors.lastname: Orlić
mesh_terms: D002412:Cations / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D011522:Protons; D012680:Sensitivity and Specificity; D013059:Spectrum Analysis, Raman / Q000379:methods; D045568:Tetraoxanes / Q000737:chemistry*; D014732:Vibration
chemical_list: D002412:Cations; D011166:Porphyrins; D011522:Protons; D045568:Tetraoxanes; D010100:Oxygen