title: New Investigations of Geometric, Electronic, and Spectroscopic Properties of Tetrapyrrolic Macrocycles by a TD-DFT Approach. Carbon, Nitrogen, and Chalcogen (O, S, Se) Peripheral Substitution Effects on Ni(II) Porphyrazinato Complexes.
abstract: The electronic structure of five complexes [M(oXHpz)] [M = Ni(2+); oXHpz(2)(-) = 2,3,7,8,12,13,17,18-octakis-substituted (X = CH2, NH, O, S, Se)-5,10,15,20-tetraazaporphyrinate dianion] has been investigated using a density functional approach. All the geometries have been obtained minimizing the total intramolecular energy using a nonlocal hybrid functional (B3LYP) at the 6-31g* level. The electronic configuration of Ni(2+) is (dx(2)-y(2))(0)(dxy)(2)(dxz,dyz)(4)(dz(2))(2). Optimized geometries exhibit a planar conformation and are all above the threshold for ruffling, which is described by a Ni-Np bond distance of 1.85-1.87 Å for sterically unhindered porphyrazines. Indeed, the smallest bond distance is 1.880 Å for Ni(oOHpz). Peripheral substituents yield modifications to the "core" of the macrocycle and to the energy levels, changing σ and π interactions. Furthermore, within a time-dependent density functional theory approach, excited states of Ni(oXHpz) [X = CH2, NH, O, S, Se,] complexes have been studied and compared with available experimental UV-vis spectra.
authors.affiliation: Faculty of Sciences, Section of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands, and LaMI, Dipartimento di Chimica and LaSCAMM, INSTM Sezione Basilicata, Università della Basilicata, Via N. Sauro 85, 85100 Potenza, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Infante
authors.affiliation: Faculty of Sciences, Section of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands, and LaMI, Dipartimento di Chimica and LaSCAMM, INSTM Sezione Basilicata, Università della Basilicata, Via N. Sauro 85, 85100 Potenza, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lelj