Porphyrazine crowned

Nitrogen substituted porphyrazines were the second type of heteroatom-deriva-tized pz macrocycle reported and were prepared from the readily derivatized diami-nomalconitrilc (DAMN) (7). Octakis(dimethylamino)porphyrazines are extremely electron-rich systems and have been used to prepare charge-transfer complexes with Cgo, as well as to peripherally chelate metals or convert to crown appended systems (38, 39). The unsymmetrical dimethylaminoporphyrazine analogues have also been reported (29), as well as the first example of the desymmetrized seco-pz from the dimethylaminoporphyrazine (8, 40). The nitrogen substituted porphyrazines are discussed in Section V. 

Crown ethers with mixed donor sets of soft sulfur and hard oxygen heteroatoms selectively ligate heavy metal ions such as mercury and silver. Porphyrazines with thia-oxo crown units appended to the periphery were published simultaneously by Hoffman and co-workers (25) and by Nolte and co-workers (26, 27). 

Synthesis. Porphyrazines Mg[pz(A4)], A = S203 crown, 81a, and Mg[pz(A4)], A = S204 crown, 81e, (35%) were prepared by cyclizing the appropriate crown dinitrile 80. Compounds 81a and 81e were demetalated with trifluoroacetic acid and remetalated with either copper or manganese acetate to form compounds 81b-81d and 81f-81h (Scheme 16) (25-27). 

Scheme 16. Preparation of crown substituted porphyrazines. [Adapted from (25-27).]...

Structural Characterization. The crystal structure of 83 (Fig. 15) surprisingly revealed eight Ag+ ions coordinated to the periphery of the porphyrazine—four bound in an endocyclic fashion by the crown moieties, consistent with the optical data, and four coordinated to the meso pockets in a (S-N-S) tridentate coordination geometry. The lack of evidence for meso coordination in solution suggests a preference for the ligation of Ag+ by the crown moieties (25). 

Synthesis. To prepare unsymmetrical porphyrazines with n = 1-3 appended thia-oxo crowns or thia crowns, the strategy of stacking the stoichiometry... 

Scheme 18. Unsymmetrical thia-oxa and thia crown porphyrazines. [Adapted from Lange, unpublished results.]...

The unsymmetrical thiacrown porphyrazines Mg[pz(A3B)], where A = Bn, B = S3 (92a) and Mg[pz(A3B)], where A = Bn, B = S4 crown (93a) were formed by a cross-condensation of excess 3,6-dibutyl-1,2-dicyanobenzene and the corresponding thiaether crown dithiomaleonitrile derivative (91). The porphyrazines were demetalated with TFA and remetalated with either copper or nickel acetate to form Compounds 92c, 93c and 93d (16-18%). 

Optical Spectra. The optical spectra of the unsymmetrical crown porphyrazines are given in Table XXV. The spectra are typical pz spectra with two intense optical absorbance bands, a Soret band at "k < 400 nm and a Q band at X > 600 nm. The Q band is split for both the metalated and free base species, with the latter exhibiting the greater splitting due to decreased symmetry. 

Electronic Absorption Maxima for Unsymmetrical Crown Porphyrazines... 

Oxa-crown porphyrazines (21) were synthesized by the Mg(II) template cyclization of crown ether derivatives of dithiomaleonitrile and shown to possess ligation of eight Ag(I) ions by utilizing both the crown ether and meso-pocket coordination sites [95AG(E)2020]. An improved preparation and the coordination chemistry with Ag(I) of oxa-crown derivatives of dithiomaleonitrile have been reported [95IC2300]. 

Hoffman et al. have reported the synthesis of tetrakis-, tris-, and monothiacrown ethers containing a tetra-azaporphyrin unit 139-152. The first porphyradine crown ethers were prepared by the Mgz+ template cyclization of the appropriate crowned derivative of dithiomaleonitrile 32 and 33 to afford 139 and 143, respectively, in ca. 35% yields. Treatment of 139 and 143 with trifluoroacetic acid provided the metal-free porphyrazines 140 and 144, respectively. Subsequent reaction with Ni(OAc)2 or Cu(OAc)2 quantitatively produced 141, 142, 145, and 146 (Scheme 21). 

They have also prepared mono- 147-149 and tris-crown ethers 150-152 containing the tetraazaporphyrin unit. Singly crowned porphyrazine 147 was prepared by the reaction of >15 equiv of 1,2-dicyanobenzene and 1 equiv of 33 under classic Linstead macrocyclization conditions. On the other hand, tris-crowned porphyrazine 150 was prepared by the reaction of 3 equiv of 32 and 1 equiv of l,2-dicyano-l,2-bis(l 1-hydroxyundecylthio)ethylene. Rapid complexa-tion of Ag+ was observed for 147-149, with weaker complexation of Hg2+ and Na+ observed only by MS. There was... 

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