One-Step Template-Directed Synthesis of a Macrocyclic Tetraarylporphyrin Hexamer Based on Supramolecular Interactions with a C₃-Symmetric Tetraarylporphyrin Trimer

Abstract

Taking into consideration the model geometry of the macrocyclic hexaporphyrin 1 as a host molecule, the structure of a benzene-centered porphyrin trimer bearing pyridine rings at the apical positions has been designed with the aim to use the latter as a template for the synthesis of its own host. Indeed, in the presence of the porphyrin trimer 5, the yield of the cyclization of a linear porphyrin hexamer, as a precursor of 1, could be improved from 8 to 30% (variable yield) to 50% (reproducible yield). Even the condensation of equimolecular amounts of porphyrin monomers 20b and 21b in the presence of 5 led--probably through a loose preorganized complex between the latter and the Zn(II) chelate 20b--to the formation of 1 in only five steps from 19, as compared with 13 steps of the synthesis via linear porphyrin hexamer in the absence of template. As evidenced by 1H NMR spectroscopic analysis of the supramolecular complex between 5 and an analogue of 1b in which all H-atoms at the pyrrole rings have been replaced by deuterium, in the presence of unlabeled 1b, a rapid dissociation and recombination of the host and guest molecules forming the supramolecular complex takes place even at low temperature (-40 degrees C). As at 55 degrees C all six Zn(II) porphyrinate rings of the complex 1b + 5 become magnetically equivalent in the 500 MHz 1H NMR time scale, approximate kinetic data for the ligand exchange process could be obtained.

Supramolecular Organization of Porphyrins and Phthalocyanines by Use of Biomimetic Coordination Methodology

“…103 Gossauer and coworkers investigated the importance of the geometry of a directing template molecule. 104 A macrocyclic porphyrin wheel 48 was synthesized Multiple binding of the porphyrin substrate(s) and a directing template ensures straightforward methodology to construct a desired macrocyclic wheel.…”

Two‐Dimensional Oligo(phenylene‐ethynylene‐butadiynylene)s: All‐Covalent Nanoscale Spoked Wheels

“…In those cases the noncovalent interior scaffold is either intended as a reinforcement of a flexible macrocycle [22] or-more commonly-as a temporary template in order to facilitate cyclization. [23] We applied the benefits of covalent template synthesis by using a star-shaped precursor molecule as a template. Scheme 1 presents the straightforward synthetic pathway to all-covalent 2D oligo(phenyl-A C H T U N G T R E N N U N G ene-ethynylene-butadiynylA C H T U N G T R E N N U N G ene)s (2D-OPEBs) relying on a highyield template-directed sixfold acetylene dimerization in the final step.…”

Template‐Directed Synthesis of a π‐Conjugated Porphyrin Nanoring

“…[1][2][3] Linear conjugated porphyrin oligomers show strong long-range electronic coupling, [4][5][6] and rich nonlinear optical behavior, [7] thereby providing a motivation for the synthesis of cyclic conjugated porphyrin oligomers. Although many cyclic porphyrin oligomers have been investigated, [8][9][10][11][12][13][14] the vast majority of them lack a complete p-conjugation pathway around the whole macrocycle. The only previously reported conjugated cyclic porphyrin oligomers are the square arrays from the research groups of Sugiura [13] and Osuka.…”

“…Cyclic porphyrin oligomers are particularly amenable to template-directed synthesis by pyridine-zinc ligation, [8][9][10][11] so a key step in our synthesis of cyclic octamer 1 was the design and synthesis of a complementary octadentate ligand 2. This template has a calculated nitrogen-nitrogen distance (between two opposite pyridyl-N atoms) of 29.6 , which is close to the ideal nitrogen-nitrogen distance of 29.0 for a template matching the cavity of cyclic octamer 1 (calculated assuming a Zn À N bond length of 2.2 and a displacement of the zinc atom by 0.3 from the plane of the porphyrin ring).…”