Photochemically-Induced Radical Reactions of Zinc Phthalocyanine

Abstract

Direct measurements of the radical reaction products following the electrochemical and photochemical oxidation and reduction of a metallophthalocyanine pi-ring are reported. Electrospray mass spectrometry was used to detect the presence of the anion zinc(II) (1,4,8,11,15,18,22,25-octafluoro, 2,3,9,10,16,17,23,24-octaperfluoroisopropylphthalocyanine chloride, [ZnperF(64)Pc(-2) (Cl)](-), and its pi ring anion radical species, [ZnperF(64)Pc(-3)(Cl)](2-). This paper describes the use of ESI-MS techniques to determine the products of an on-line, photochemical radical oxidation, using CBr(4) as a sacrificial photoinduced oxidizing agent, which oxidized the radical, [ZnperF(64)Pc(-3)(Cl)](2-) species to [ZnperF(64)Pc(-2)(Cl)](-), where the complete reaction was detected directly by the mass spectrometer. This study makes use of electrospray mass spectrometry to detect the presence of an anion radical as the key component in the ring-reduced species and to monitor the immediate products of the important class of photochemical reduction and oxidation reactions in which radicals of the Zn Pc are formed in situ.

Photoreduction and light-induced triplet-state formation in a single-site fluoroalkylated zinc phthalocyanine

“…The anion radical was reported to have been obtained via the electrochemical reduction of F 64 PcZn or via its photochemical reduction using sacrificial hydrazine hydrate. 15,16 In the current work, we show that the photochemical production of reactive radical species can be achieved in ethanol without the need for an external electron donor, an observation relevant to the previously reported photocatalytic properties of F 64 PcZn in ethanol. 9…”

“…The latter was assigned based on previously reported absorption bands characteristic of this species (upward arrows, Fig. 2), which were also observed for the electrochemically reduced complex and the photo-reduced complex in the presence of sacrificial hydrazine hydrate 15,16 (Table 1). The small hypsochromic shifts of the absorption maxima are due to the change of solvent.…”

“…2) are similar to those previously reported for F 64 PcZn in DMF. 15,16 When ethanolic solutions of F 64 PcZn were irradiated with UV light generated by a Xe lamp (450 W), a clear decrease in absorbance was observed under aerobic conditions, Fig. S2; † after 60 min of irradiation, the absorbance was reduced to about 80% of the original signal intensity.…”

On‐line Monitoring Reactions by Electrospray Ionization Mass Spectrometry

“…Presumably, the metal ion was released upon charge-charge repulsion, followed by the intramolecular ionization of the leuconitrile moiety (Scheme 5.7). Stillman and coworkers [51] reported the direct measurements of the products following the photooxidation and photoreduction of a metallophthalocyanine p-ring. The same on-line photochemical ESI-MS methodology was employed in the analysis of photoallylation reactions of dicyanobenzene (DCB) by allylic silanes via photoinduced electron transfer [48].…”

Zinc: Inorganic & Coordination ChemistryBased in part on the article Zinc: Inorganic & Coordination Chemistry by Reg H. Prince which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

“…Both porphyrins and phthalocyanines can act as π -electron acceptors or donors, to give radical ligands bonded to Zn 2+ . 115 Much effort has been devoted to varying the electronic properties of ligand substituents to tune redox potentials. 116 There is currently considerable interest in assembly and self-assembly of zinc porphyrins, 117 for example the generation of a nonameric porphyrin array.…”