Exploring the Effects of Axial Pseudohalide Ligands on the Photophysical and Cyclic Voltammetry Properties and Molecular Structures of Mg^II Tetraphenyl/porphyrin Complexes

Abstract

The (meso-tetraphenylporphyrinato)magnesium(II) complexes with azido (1), cyanato-N (2), and thiocyanato-N (3) ligands were prepared by using 2.2.2-cryptand to solubilize the azide, cyanato, and thiocyanato salts in dichloromethane solvent. These species were characterized by UV/Vis and IR spectroscopy, mass spectrometry, and electrochemistry. The first reduction potential and the two first oxidation potentials of the porphyrin rings of these species are not affected by the nature of the axial ligand, and an unusual third irreversible oxidation of the porphyrin ring is observed. The anodic behavior of the magnesium azide derivative is complicated by the appearance of additional signals for ligand-centered electron transfers that originate from the release of the azido ligand of 1. The room-temperature fluorescence spectra of the magnesium complexes 1-3 indicate that the Soret and Q bands are not particularly affected by the nature of the axial ligands. The quantum yields of the S 1 ǞS 0 fluorescence are between 0.10 and 0.19, and the fluorescence lifetimes range between 3.7 and 6.1 ns at room temperature. Complexes 1-3 crystallize in the monoclinic crystal system in the same space

Synthesis, molecular structure, photophysical properties and spectroscopic characterization of new 1D-magnesium(II) porphyrin-based coordination polymer

“…2 and 3, respectively. As reported in the literature, magnesium metalloporphyrins with monodentate axial ligands are generally exist as five-coordinated species [Mg(Porph)(X)] (X = neutral or anionic ligand) [39][40][41]. In few cases there exit also as six-coordinated derivatives [Mg(Porph)(L) 2 ] (L = neutral axial monodentate ligand) i.e.…”

Insights on the UV/Vis, Fluorescence, and Cyclic Voltammetry Properties and the Molecular Structures of ZnII Tetraphenylporphyrin Complexes with Pseudohalide Axial Azido, Cyanato‐N, Thiocyanato‐N, and Cyanido Ligands

“…We speculate that the redshifts in the spectra of 1 – 4 are due to the significant porphyrin deformations of our derivatives (see Crystallographic Section). Unlike the redshifted Soret bands of the pentacoordinate pseudohalide(tetraphenylporphyrinato)zinc(II) complexes mentioned above, the related magnesium(II) complexes [Mg(TPP)(X)] – (X = N 3 – , NCO – , or NCS – )20 show practically no shift of the Soret band compared to those of neutral [Mg(TPP)(L)] derivatives [L = imidazole (Him), pyridine (py), etc. ].…”

“…The luminescence decays were analyzed with the FLUOFIT software from Picoquant. The emission quantum yields were determined at room temperature by the optically dilute method with samples in CH 2 Cl 2 solutions 20. [Zn(TPP)] in air‐equilibrated CH 2 Cl 2 solution was used as a quantum yield standard ( φ = 0.031).…”

Magnesium Tetra(phenylethynyl)porphyrin: Stepwise Synthetic Route, Crystal Structures, and Longer Singlet Excited‐State Lifetime than Zinc Congener

“…The absorption maxima of the Q‐band absorptions of 1 a and 1 b were located at 698 and 686 nm, respectively, and were redshifted compared to the Q‐band absorption of Mg‐TIPSTEP at 679 nm . Overall, the absorption bands were redshifted compared to magnesium tetraphenylporphyrin (Mg‐TPP, 608 nm) . The molar absorption coefficient of 1 a in the range of the Soret‐band absorption exceeded 600 000 dm 3 mol −1 cm −1 .…”