One-pot synthesis of nickel porphyrins with 2-pyridine-acetyl substituents: the unexpected Sonogashira cross-coupling products

Photophysical Investigation of Neutral and Diprotonated Free-Base Bis(Arylethynyl)porphyrins

“…While zinc, − copper, nickel, , and iron arylethynyl porphyrins have been reported, studies of free-base arylethynyl porphyrins are limited to only a few examples, ,− despite the unique functionality of metal-free porphyrins. Free-base porphyrins typically exhibit enhanced fluorescence quantum yields and excited state lifetimes relative to metalated derivatives .…”

Peripheral Covalent Modification of Inorganic and Organometallic Compounds through C−C Bond Formation Reactions

“…Lin and co-workers reported the attachment of N-methylated pyridylethynyl at the meso-positions of Zn-porphyrins, 60 and the surprising modification of 2-pyridineacetyl at the mesoposition of Ni(II)-porphyrin during the Sonogashira coupling reaction. 61 Yeh and co-workers found that the cross-coupling between 5-iodo-10,15,20-triarylporphyrin Zn(II) and HC≡ CSiMe 3 in large excess (10-50-fold) resulted in a mesoeneyne product (19 in Scheme 9) in addition to the expected meso-ethyne derivative (20), and the ratio between compounds 19 and 20 depends on the nature of Pd catalysts. 62 Feasibilities of Sonogashira coupling on the periphery of metallophthalocyanine have been demonstrated, including the formation of zinc-phthalocyanine-estradiol conjugates, 63 bis(zinc(II) phthalocyanine) bridged by perylenediimide, 64 and the dyad of zinc phthalocyanine and tin porphyrin with oligo(phenyleneethynylene) bridge.…”

“…While the Sonagashira coupling method results in expected products in good yield, formation of byproduct is frequently observed but rarely subjected to a thorough analysis. Lin and co-workers reported the attachment of N -methylated pyridylethynyl at the meso -positions of Zn-porphyrins, and the surprising modification of 2-pyridineacetyl at the meso -position of Ni(II)-porphyrin during the Sonogashira coupling reaction . Yeh and co-workers found that the cross-coupling between 5-iodo-10,15,20-triarylporphyrin Zn(II) and HC≡CSiMe 3 in large excess (10−50-fold) resulted in a meso -eneyne product ( 19 in Scheme ) in addition to the expected meso -ethyne derivative ( 20 ), and the ratio between compounds 19 and 20 depends on the nature of Pd catalysts …”