Formation of ameso-Tetraphenylsecochlorin and a Homoporphyrin with a Twist

Abstract

The osmium tetroxide-mediated dihydroxylation of meso-tetraphenylporphyrin leads to the formation of the vic-diol meso-tetraphenyl-2,3-vic-diol-2,3-chlorin. The corresponding Ni(II) complex was converted by lead tetraacetate into (meso-tetraphenyl-2,3-secochlorinato-2,3-dialdehyde)nickel(II). This novel pigment undergoes an almost quantitative, intramolecular double acetal formation when treated with methanol in the presence of acid to produce a porphyrinoid in which one pyrrolic unit is formally replaced by a six-membered ring. An X-ray crystal structure determination, the first for such a homoporphyrin, reveals the severely twisted conformation of its chromophore.

Aza-deficient porphyrin as a ligand

“…Porphyrin may be regarded as an diaza [18] annulene with two nitrogen and two ethylene bridges (4b). Some arguments point out different models to be of preference: a [20]annulene dication bridged with two neutral and two negatively charged nitrogen bridges (4c) or tetraaza [16]annulene dianion with dicarbon bridges (4a) [10,11].…”

“…In independent studies concerning a catabolism of chlorophyll a related porphyrinoid was detected. Thus in a two-step oxidation reaction of nickel porphyrin complex, dihydroxylation and then cleavage of ␤-␤ bond took place and yielded aromatic 2,3-secochlorin-2,3-dione nickel complex for both, octaethyl and tetraphenyl (8) derivatives [15,16].…”

Axial Imidazole Binding Strengths in Porphyrinoid Cobalt(III) Complexes as Studied by Tandem Mass Spectrometry

“…Free base diolchlorins 4 and 8 were prepared by OsO 4 -mediated dihydroxylation of the corresponding porphyrins [37,40]. Free bases of porpholactones 2 [43], dioxoporphyrin 7 [42], indaphyrin 5 [45], and morpholinochlorin 3 [43] were made by oxidation/derivatization of free base meso-tetraphenyl-2,3-diolchlorin 4.…”

“…Metallochlorins [4]Co and [8]Co are the 2,3-dihydroxychlorin analogues to porphyrins [1]Co and [9]Co, respectively [37]. Owing to their nature as reduced porphyrins, they possess higher HOMO levels compared to porphyrins [38].…”

Synthetic approaches to asymmetric phthalocyanines and their analogues

“…Peripheral oxidation transformation is a very popular approach for preparation of asymmetric functionalized porphyrins, [244][245][246][247][248][249][250][251][252][253][254][255] but so far has only limited application in phthalocyanine chemistry. Thus, octa(dimethylamino)-substituted tetraazaporphyrins 79 can be oxidized by manganese(IV) oxide to form two different seco-porphyrazines 80 and 81 (Scheme 27A).…”