Acetylen‐Cumulen‐Porphyrinoide

Abstract

Das Synthesekonzept fur 12 grundete auf der Erwartung, daD der acetylenische Dipyrroldialdehyd 10 sich mittels niedervalentem Titan@' unter Bildung des echten tetrapyrrolischen Makrocyclus 11 reduktiv kuppeln laDt und 11 ein dem N, N'-Dihydroporphycen [71 analoges Verhalten zeigt, indem es spontan unter Luftoxidation zum Acetylen-Cumulen-Porphycen 12 weiterreagiert. Die eigentliche Aufgabe ware damit auf die Synthese von 10 reduziert. Um zu 10 zu gelangen, wurde der bekannte Pyrrolaldehyd 5

Furan-Based Porphyrins: Tetraoxa[4n+2]porphyrin Dications with 18π-, 22π-, or 26π-Electron Systems

“…The NMR and UV/Vis spectra of 9 correspond to those of the known octaethyltetradehydro[22]-porphyrin-(2.2.2.2) in its doubly protonated form. [14] For the synthesis of the tetraoxa [26]porphyrin-(3.3.3.3) dication, as the octaethyl derivative 13 for reasons of solubility, we followed the route illustrated in Scheme 2, which was based on porphyrin chemistry methodology. [2] The starting aldehyde 10 was obtained by vinylogous Vilsmeier formylation of 3,4-diethylfuran with 3-(N,N-dimethylami- no)acrolein and phosphorus oxychloride in dichloromethane at 0 8C (pale yellow crystals; m.p.…”

β‐Octamethoxy‐Substituted 22π and 26π Stretched Porphycenes: Synthesis, Characterization, Photodynamics, and Nonlinear Optical Studies

“…[8] To improvethe yield of the desired product, we employed amodified Glaser-Hay coupling protocol, in which oxidative coupling of 9a and 9b in the presence of ac atalytic amount of [PdCl 2 (PPh 3 ) 2 ]a nd CuI with ab ase under an oxygen atmosphere led to the desired diacetylene-bridged bipyrroledialdhydes 11 a and 11 b in 94 and 95 %y ield at room temperature, respectively.M cMurry coupling of 10 b with Zn/TiCl 4 in the presenceo fC uCl under reflux conditions, followed by oxidation in air gave desired b-octamethoxy 22p-acetylene-cumuleneporphycene 4 in very poor yield with reduced 22pb -octamethoxy[22]porphyrin-(2.2.2.2) 6 as the major product. [3] Because the 3,4-dimethoxypyrrole analogue is ah ighly activated system,w ep erformed the McMurry coupling reactionb ys low addition of 10 b at room temperature and this modification led to the formationofthe desired product 4 as the major product and reducedp roducts as am inor component. Although it was difficult to purify the mixture of products by columnc hromatography,w ec ould obtain pure compound 4 in 26 %y ield (Scheme 1), by simply washing with hexane andc hloroform (1:1).…”

“…(18 %). [3] Syntheses of 26p-b-octasubstituted acetylene-cumuleneporphycenes (2 and 5)w ere achieved by McMurry coupling of diacetylene-bridged bipyrroledialdhydes 11 a and 11 b under reflux conditions;t his led to the formation of compounds 2 and 5 both in 17 %y ield. Again our method led to the formation of 2 in much highery ield than that reported by Vogel et al (9 %).…”

“…The UV/Vis absorptions pectra of 4 and 5 show marginal changes in the absorptionm aximac ompared with their ethyl analogues. [3,5] However, there is ad iscernible differencei nt he spectralp atterns, in particular, in the Q-band region, where the methoxy derivatives display the second band as the most intense one of the three, whereas for the ethyl analogues,t he lowest energyb and is the mosti ntenseo ne. Again the effect of substituentsi sm ore apparent in the case of [22]porphyrin-(2.2.2.2), with the absorption spectrum of 6 showingt he lowest energy Qb and blueshifted by about 17 nm compared with that of 3.…”

“…[2] In this direction, core expansion of porphycenes by using an even number of bridging meso-carbon atoms between the constituent pyrrole units was reported by Vogel et al in 1990. [3] Owing to the occurrence of pairwise linearC sp 2C sp C sp C sp 2 structural units, the resultant macrocycles are called acetylene-cumulene porphyrinoids, whereas the corresponding reduced product [ 22]porphyrin-(2.2.2.2) [4] is named astretched porphycene,owing to its closer relationship to porphycene. Although these macrocycles were anticipated to have potential utility as an effective photosensitizer for photodynamict herapy( PDT), previousr eports showed limitations in their application because of their low triplete nergyg ap, and hence, poor singlet oxygen generation ability.…”