Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Abstract

Condensation of 2,4-bis(phenylhydroxymethyl)furan with pyrrole and p-toluylaldehyde formed, instead of the expected 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin, a pyrrole addition product [(H,pyr)OCPH]H(2); this product can formally be considered as an effect of hydrogenation of 3-(2'-pyrrolyl)-5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin ([(pyr)OCPH]H). The new oxacarbaporphyrinoid presents the (1)H NMR spectroscopy features of an aromatic molecule, including the upfield shift of the inner H21 atom. Insertion of NiCl(2) or PdCl(2) into [(H,pyr)OCPH]H(2) gave two structurally related organometallic complexes, [(pyr)OCP]Ni(II)] and [(pyr)OCP]Pd(II)], in which the metal ions are bound by three pyrrolic nitrogens and the trigonally hybridized C21 atom of the inverted furan. The reaction of [(H,pyr)OCPH]H(2) with silver(I) acetate yields a stable Ag(III) complex [(C(2)H(5)O,pyr)OCP]Ag(III)] substituted at the C3 position by the ethoxy and pyrrole moieties. The macrocyclic frame of [(H,pyr)OCPH]H(2) is conserved. Addition of trifluoroacetic acid to [(C(2)H(5)O,pyr)OCP]Ag(III)] yielded a new aromatic complex [(pyr)OCP]Ag(III)](+). The structures of [(pyr)OCP]Ni(II)] and [(C(2)H(5)O,pyr)OCP]Ag(III)] have been determined by X-ray crystallography. In both molecules the macrocycles are only slightly distorted from planarity and the nickel(II) and silver(III) are located in the NNNC plane. The dihedral angle between the macrocyclic and appended-pyrrole planes of [(pyr)OCP]Ni(II)] reflects the biphenyl-like arrangement with the NH group pointing out toward the adjacent phenyl ring on the C5 position. Tetrahedral geometry around the C3 atom was detected for [(C(2)H(5)O,pyr)OCP]Ag(III)]. The Ni[bond]C and Ag[bond]C bond lengths are similar to other nickel(II) or silver(III) carbaporphyrinoids where the trigonal carbon atom coordinates the metal ion. The trend detected in the (13)C chemical shifts for the appended-pyrrole resonances has been rationalized by the extent of effective conjugation between the macrocycle and the appended pyrrole moiety controlled by the hybridization of the C3 atom and the metal ion oxidation state. The dianionic or trianionic macrocyclic core of the pyrrole-appended derivatives is favored to match the oxidation state of nickel(II), palladium(II), or silver(III), respectively.

meso-Arylporpholactones and their Reduction Products

“…Pawlicki and Latos-Grazynski reported the total synthesis of 17 , the carbaporphyrin analogue to 3-methoxy-2-oxachlorin 13-OEt . 44,45 This reaction is in contrast to our ‘breaking and mending of porphyrin’ strategy toward porpholactones 5 . Like 13-OEt (see below), 2-oxa-21-carbachlorin 17 possesses a chlorin-like spectrum (λ Soret = 437 nm and four Q-bands with λ max = 672 nm).…”

Reactivity of Silole within a Core‐Modified Porphyrin Environment: Synthesis of 21‐Silaphlorin and its Conversion to Carbacorrole

“…HMQC and HMBC connectivities found for the cyclopentadiene moiety of iso-8. verA C H T U N G T R E N N U N G (III) inverted porphyrin [Ag À N22, 2.06(2); Ag À N23, 2.08(2); AgÀN24, 2.03(2); and AgÀC21, 2.04(2)], [67] silverA C H T U N G T R E N N U N G (III) benzocarbaporphyrin [AgÀN22, 2.038(4); AgÀN23, 2.084(4); Ag À N24, 2.046(4); Ag À C21, 2.015(4)], [68] silverA C H T U N G T R E N N U N G (III) double N-confused porphyrin [AgÀC21, 2.011(7); AgÀC22, 1.987(2); AgÀN23, 2.064(5); and AgÀN24, 2.047(7)], [69] silverA C H T U N G T R E N N U N G (III) O-confused oxaporphyrin with appended pyrrole ring [Ag À N22, 2.031(5); Ag À N23, 2.069(5); Ag À N24, 2.042(5); Ag À C21, 2.020(7)], [19] and silverA C H T U N G T R E N N U N G (III) carabaporpholactone [Ag À C21, 2.013(5); Ag À N22, 2.020(4); Ag À N23, 2.038(4); Ag À N24, 2.039 (4)]. [17] A comparison of the structural data, although limited to the five available examples of silverA C DFT calculations: One question requiring an answer is why the oxidation of 21-silaphlorin leads to a iso-carbacorrole …”

“…This strategy resulted in formation of thia and oxa analogues of N-confused porphyrin in which the sulfur or oxygen is located on the periphery of the macrocycle. [14][15][16][17][18][19] Finally, interchanging a nitrogen atom with a bmethine group transforms the regular heteroporphyrin into the N-confused isomer. [20,21] In general, a reaction between 2,5-bis(arylhydroxymeth-A C H T U N G T R E N N U N G yl)heterocyclopentadiene and pyrroles produced a variety of 5,10,15,20-tetraphenyl-21,23-diheteroporphyrins.…”

“…[20,21] The use of X-confused derivatives 2,4-bis(arylhydroxymethyl)heterocyclopentadiene instead of a regular counterpart afforded X-confused heteroporphy-A C H T U N G T R E N N U N G rins. [15,17,19] The recent seminal reports by Matano and coworkers on the synthesis of 21-phospha-23-thiaporphyrin, [29] phosphole-containing calixpyrroles [30] and calixpyrins [31] presented the replacement of nitrogen by phosphorous for the very first time. This remarkable step in the field of coremodified porphyrins provides an incentive to search for porphyrinoids that contain a built-in non-trivial heteroatom.…”

Two Macrocycles in One Shot: Synthesis, Spectroscopy, Photophysics, and Tautomerism of 23‐Oxahemiporphycene and 21‐Oxacorrole‐5‐carbaldehyde

“…[7] All of the features noted above maket he chemistry of porphyrinh eteroanalogues very promising in the context of possible skeleton modifications, formation of complexes, and potential applications,a sw as briefly summed up in ar ecent review. [8] However,d espite the broadi nterest in this group of compounds, heteroanalogueso fk nown porphyrin isomers:i nvertedporphyrin, [9,10] porphycene, [11] hemiporphycene, [12,13] isoporphycene, [14] andc orrphycene [15] have been explored only in the case of porphycene [16] and inverted porphyrin [17][18][19][20] skeletons.…”