Photoconductive properties and electronic structure in 3,5-disubstituted 2-(2′-pyridyl)pyrroles coordinated to a Pd(II) salicylideneiminate synthon

The synthesis and the electrochemical, photophysical, structural, and photoconductive properties of three new heteroleptic Pd(II) complexes with various 3′,5′- disubstituted-2-(2′-pyridil) pyrroles H(N^N) as coordinated ligands are reported. The coordination of the metal center was completed by a functionalized Schiff base H(O^N) used as an ancillary ligand. The [(N^N)Pd(O^N)] complexes showed highly interesting photoconductive properties which have been correlated to their electronic and molecular structures. Theoretical density functional theory (DFT) and time-dependent DFT calculations were performed, and the results were confronted with the organization in crystalline phase, allowing to point out that the photoconductive properties are mainly a consequence of an efficient intramolecular ligand-to-metal charge transfer, combined to the proximity between the central metal and the donor moieties in the solid-state molecular stacks. The reported results confirm that these new Pd(II) complexes form a novel class of organometallic photoconductors with intrinsic characteristics suitable for molecular semiconductors applications.Supported by Ministero dell’Istruzione, dell’Universitàe della Ricerca by the ELIOTROPO.Peer reviewe

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

The electronic structure of five complexes [M(oXHpz)] [M = Ni2+; oXHpz2- = 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 Ni2+ is (dx2-y2)0(dxy)2(dxz,dyz)4(dz2)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

Mono-molecular isomerization processes of aluminium tris (8-hydroxy-quinolinate) (Alq3): a DFT study of gas-phase reaction paths

Density Functional Theory has been applied to investigate isomerization processes of aluminum tris(8-hydroxyquinolinate) (Alq3). Both mer–fac isomerization and mer-Alq3 chirality inversion have been reported. This represents an attempt to describe phenomena which could take place during Alq3 amorphous-films deposition or during solid-state changes of phase. Furthermore, it represents the opportunity to apply modern theoretical methodologies to shed light on the general problem of isomerizations in tris–chelate complexes which were widely studied experimentally and by approximate theoretical methods in the seventies and in part of the eighties

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

The electronic structure of five complexes [M(oXHpz)] [M = Ni2+; oXHpz2- = 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 d. functional approach. All the geometries have been obtained minimizing the total intramol. energy using a nonlocal hybrid functional (B3LYP) at the 6-31g* level. The electronic configuration of Ni2+ is (dx2-y2)0(dxy)2(dxz,dyz)4(dz2)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 d. functional theory approach, excited states of Ni(oXHpz) [X = CH2, NH, O, S, Se,] complexes have been studied and compared with available exptl. UV-vis spectra. [on SciFinder(R)