Formation, Photophysics, and Photochemistry of Anionic Lanthanide(III) Mono- and Bisporphyrins

Abstract

Since water-soluble porphyrin complexes of lanthanides(III) have proved to be promising for medical applications (e.g., luminescence imaging, photodynamic therapy, and theranostics), the investigation of the formation, photophysical, and photochemical properties of such coordination compounds provides useful pieces of information for their potential usage. Steady-state and time-resolved fluorometry, UV–Vis absorption spectroscopy, and continuous-wave photolysis were utilized for this purpose. 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin formed mono- and bisporphyrin complexes with samarium(III), europium(III), and gadolinium(III) as representatives in the middle of the lanthanide series. The special photoinduced behavior of these compounds was mostly determined by the position of the metal center, which was located out of the ligand plane, thus distorting it. Besides, the photochemical and, especially, photophysical features of the corresponding mono- and bisporphyrin complexes were similar because, in the latter species, two monoporphyrins were connected by a weak metal bridge between the peripheral sulfonato substituents (tail-to-tail dimerization). The formation of these coordination compounds and the transformation reactions between the mono- and bisporphyrins were rather slow in the dark at room temperature. These processes were accelerated by visible irradiation. However, dissociation and, especially, redox degradation were the main photoreactions in these systems, although with low quantum yields. Additionally, depending on the excitation wavelength, new types of photoproducts were also detected.

Supramolecular Self-Assembly of Porphyrin and Metallosurfactant as a Drug Nanocontainer Design

“…The intensity of the Soret band decreases with the addition of LaSurf until an equimolar amount is reached, i.e., up to a TSPP:LaSurf ratio of 1:1, and this band splits into two with maxima at 404 and 418 nm with a two-fold excess of LaSurf (Figure 2a). The appearance of absorption at 404 nm indicates a formation of H-type TSPP aggregates, and the presence of an absorption band at 418 nm can be caused either by the formation of mixed TSPP-LaSurf aggregates, in which the macrocycle is folded into J-aggregates [27,54,55] or by the inclusion of lanthanum in the porphyrin cavity [56]. Moreover, with a further increase in the amount of LaSurf in a mixed solution with TSPP, the absorption value at 404 nm slightly decreases, while that at 418 nm gradually increases.…”

Effects of Temperature, Axial Ligand, and Photoexcitation on the Structure and Spin-State of Nickel(II) Complexes with Water-Soluble 5,10,15,20-Tetrakis(1-methylpyridinium-4-yl)porphyrin

“…The two groups significantly differ in their photophysical, electronic, and coordination properties. Among the out-of-plane (e.g., lanthanide) complexes, the ligand undergoes photo-oxidation and thus (transient) reduction of the central metal ion upon light absorption [ 8 ]. A large group of important reactions is those of photo-redox systems, in which various, usually normal metalloporphyrins often act only as sensitizers, e.g., in photodynamic therapy [ 9 , 10 , 11 ].…”

Hydrothermal Synthesis and Properties of Nanostructured Silica Containing Lanthanide Type Ln–SiO2 (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu)

“…Recently, lanthanides have been applied in several areas of interest [ 23 , 24 , 25 , 26 , 27 ]. They are the most active elements in catalysts for oxidative coupling of methane to form higher hydrocarbons.…”