Synthesis and Properties of Conjugated Porphyrins with a Diacetylene Spacer

Abstract

A series of (porphyrin)–(C≡C)2–C6H4–R1 (R1 = NO2, H, Me, and OMe) were synthesized by the oxidative coupling of ethynyl porphyrins and phenylacetylenes in the presence of copper(II) acetate in pyridine. Electronic and electrochemical spectra of the compounds with R1 = H, Me, and OMe are quite similar, while pronounced change was observed for the compound with R1 = NO2, especially for the meso-substituted one, indicating that intramolecular charge transfer is responsible for the difference.

Conjugated dimers of nickel(II) octaethylporphyrin linked by extended meso,meso-alkynyl bridges. II Redox properties and electronic spectra of electrogenerated anions and dianions

“…The spectra of the dianions of 18 and 19 still conform to the pattern established by the dimers 1, 11È14, 16 and 17, i.e., they display the collapsed and split Soret region, and the intense band near 11 000 cm~1. Remarkably, the spectrum of the dianion of 15 is almost identical to that of the comparable monomer 4.6 The spectrum of [15]2ĩ s therefore essentially a superposition of two monomeric alkynyl-NiOEP monoanion units, especially with respect to the low intensity of the radical anion marker band near 11 000 cm~1.…”

“…In interrupted alkyne-linked species such as m-phenylene 15, the spectra of both the neutral molecule and its dianion are basically those of two non-interacting porphyrins, with typically intense Soret and weak Q band proÐles. The Soret band of [15]0 shows a very small splitting of ca. 550 cm~1, within the expectations of through-space excitonic coupling, rather than through-bond conjugative interaction.…”

“…This explains three observations : (i) electronic spectra of [18]0 and [19]0 do not have the characteristic " strongly-coupled Ï yne-linked appearance,1 (ii) the mixed-valence monoanions are unobservable, and (iii) the corresponding dianions do have the intense near-IR signature band. The dianions of the trans-ethene-linked dimers 20 (M \ Ni) have electronic spectra of the " non-interacting Ï H 2 , pattern exempliÐed by [15]2~, i.e., their near-IR bands are weaker than the bands in the Soret region.21 This is presumably because with such a short bridge the linkage region is congested by two sets of Ñanking ethyl groups, thus preventing coplanarity even in the dianions. The longer bridges in 18 and 19 apparently separate the OEP units sufficiently to permit conjugation, and hence the intense signature band, to be switched on when the occupancy of reaches two.…”

Dimers and Model Monomers of Nickel(II) Octaethylporphyrin Substituted by Conjugated Groups Comprising Combinations of Triple Bonds with Double Bonds and Arenes. 1. Synthesis and Electronic Spectra

“…4,5 There has since been a flurry of activity in the field of alkynesubstituted porphyrins, including dimers and oligomers with alkyne-containing bridges. [6][7][8][9][10][11][12][13][14][15][16][17] Anderson has reported arrays of up to 10 porphyrins linked by butadiyne bridges, 6,7 while Lin et al have described ethyne-bridged dimers and trimers. 9,10 These syntheses involved palladium-catalyzed couplings of terminal alkynes or alkynyl organometallics with various halides, as well as standard alkyne oxidative couplings.…”

Synthesis, characterization and cation-induced dimerization of new aza-crown ether-appended metalloporphyrins

“…And the small magnitude of the effect is resulted from the weak conjugation of the porphyrin system with a phenyl substituent due to its nearly orthogonal position. 32 The fluorescence quantum yields of aza-crowned porphyrins ZnP,3 and ZnP,5 (0.5 × 10 −6 M), determined relative to ZnTMsPTMS (zinc 5,10,15-tri-mesityl-20-trimethylsilylacetylene porphyrin), 42 are 0.059 and 0.030 respectively. The decrease of quantum yield of ZnP,5 can be attributed to the increase of the electron transfer to the porphyrin core from unshared electron pairs of nitrogens from two aza-crown ether units in comparison to the one unit in ZnP,3.…”