Molecular recognition with C-clamp porphyrins: Synthesis, structural, and complexation studies

Abstract

Porphyrin-based molecular clefts equipped with a strategically positioned carboxylic group have been synthesized. These ditopic porphyrins exhibit excellent binding affinity for many neutral substrates. X-ray structures of a porphyrin-water inclusion complex and a Zn(porphyrin)-methanol complex reveal how the carboxylic group interacts with substrates via H-bonding. Multipoint recognition is demonstrated in the differential binding of 1,2,3- versus 1,2,4-triazole, suggesting the possible use of such receptors to separate heterocyclic bases.

Synthesis and Characterization of a Novel Phenol‐tailed Porphyrin Ligand and Its Iron(III) Complex

“…Notably, there are no observable signals for OH and NH protons, which is probably due to fast exchange among them. Similar case has also been reported by Liang et al7 For [Fe(L)], the spectrum shows resonances in the far‐upfield and far‐downfield region because of the paramagnetic metal iron(III) 6. According to the positions and intensities, the pyrrole proton signals are assigned at δ = 80.31 and 88.33 ppm, which is typical for a five‐coordinate high‐spin (tetraphenyl‐porphyrinato)iron(III) complex 8.…”

Molecular Recognition of Amines and Amino Esters by Zinc Porphyrin Receptors: Binding Mechanisms and Solvent Effects

“…Therefore the longer flexible methylene chains of the receptors help discriminate these amino esters. To date, a number of zinc porphyrins were reported to bind amino esters, − but much reduced affinity toward Leu-OMe and PhGly-OMe is unprecedented. Several zinc tetraarylporphyrins having bulky substituents at the 2 and 6 positions of the aryl groups do not show weak affinity toward Leu-OMe or PhGly-OMe. ,, The origin of the weak affinity of Leu-OMe and PhGly-OMe is not clear, but it is probably due to a mechanism in which the bulky side chain group of these guests forced the guest molecule to adopt an unfavorable conformation such as the undesirable orientation of the ester groups .…”

“…Therefore the longer flexible methylene chains of the receptors help discriminate these amino esters. To date, a number of zinc porphyrins were reported to bind amino esters, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] but much reduced affinity toward Leu-OMe and PhGly-OMe is unprecedented. Several zinc tetra-arylporphyrins having bulky substituents at the 2 and 6 positions of the aryl groups do not show weak affinity toward Leu-OMe or PhGly-OMe.…”

Activation Energy of Proton Exchange Processes of Deuteroporphyrin IX Dimethyl Ester with Water in C6D6 Medium Based on DOSY Data

“…D NH при переносе протона с молекулы порфирина на молекулу воды увеличивается только в случае разрушения ассоциата порфирин-вода, поэтому наблюдаемая Е а (NH) связана только с процессами высвобождения воды. Определенная нами Е а (NH) находится в пределах значения единичной энергии водородной связи для взаимодействий с водой порфиринов, описанных в литературе [1,23,24] (от 10 до 20 кДж/моль). На основании литературных данных [17] можно предположить протекание обмена через цис-таутомер, как изображено на Схеме 1 применительно к диметиловому эфиру дейтеропорфирина IX.…”