Metallkomplexe mit Tetrapyrrol-Liganden. 68. Synthese wasserl�slicher Osmium-Porphyrin-Komplexe

Metal complexes with tetrapyrrole ligands: Part LXXVII. New osmium complexes of the 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin

The synthesis and characterization of new alkali-soluble osmium tetraphenylporphyrinates, complexes of the 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Os ( tH 4 cpp ) L 2 and Os ( tH 4 cpp ) LL ' (2a–j), is described. 2a–j are obtained from the corresponding new osmium porphyrinates Os ( tmecpp ) L 2 and Os ( tmecpp ) LL '(1a–k) by alkaline saponification and precipitation with hydrochloric acid. In fact, the osmium(II) porphyrinates 2c–f as well as 2i–j are oxidized to the osmium(III) porphyrinates Os ( tH 3 cpp ) L 2(3c–f) and Os ( tH 3 cpp ) LL '(3i–j) in the presence of air, as confirmed by UV-vis spectroscopy.

Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase

In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples Os(III)HRP/Os(IV)HRP, Os(IV)HRP/Os(V)HRP and Os(V)HRP/Os(VI)HRP. The midpoint potentials differ dependent on the electrode material used with E(1/2) (Os(III/IV)) of -0.4 V (ITO) and -0.25 V (GC), E(1/2) (Os(IV)/(V)) of -0.16 V (ITO) and +0.10 V (GC), and E(1/2) (Os(V/VI))of +0.18 V (ITO), respectively. Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher.

Contributions to the chemistry of anionic water-soluble tetraarylporphyrins and their metal complexes

Recent contributions to the coordination chemistry of tetraanionic water-soluble tetraarylporphyrins, namely 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, [1]4−, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, [2]4−, and 5,10,15,20-tetrakis(4-hydroxidophosphorylmethylphenyl)porphyrin, [ H 43]4−, are reported. Problems with the isolation of sodium and potassium salts of [2]4− are discussed. The tetraphosphonoporphyrin H 8[3] is precipitated as a dihydrochloride H 8[3]·2 HCl , its metal complexes H 8[3-M] as such. The synthesis of salts containing Ce and Os complexes of [1]4−, Al , Ga , In , Ge , Sn , As , Sb , Mn , Mo , W , Re , Os , and Pt complexes of [2]4−, and Ni , Cu , Zn , Pt and Os complexes of [ H 43]4− as documented in publications and doctoral theses from the Darmstadt laboratory are reviewed. Some properties of the new complex salts are reported. The results of crystal structure determinations of the potassium salt of tetrakis(4-sulfonatophenyl)porphyrinatoplatinate(II), K 8[2-Pt]2·10 DMSO ·6 H 2O· C 7 H 8, and the mixed sodium-potassium salt of tetrakis(4-sulfonatophenyl)porphyrinatoaluminate, K 2 Na [ Al ( DMSO )2( tpps 4)]·8( DMSO )·2 H 2 O , are shown.