Figure - available from: Chemistry - A European Journal
This content is subject to copyright. Terms and conditions apply.
¹H NMR spectra of aromatic regions in atropisomers 2 and 3 (d6‐DMSO or CDCl3); ΔT represents atropisomeric thermal interconversion; Hashtag symbol marks chloroform signal.
Source publication
![a) Graphical representation of easily accessible meta‐positions[9] and...](publication/356356450/figure/fig1/AS:11431281246264571@1716321453244/a-Graphical-representation-of-easily-accessible-meta-positions9-and-sterically_Q320.jpg)
Inspired by the rigidified architecture of ‘picket‐fence’ systems, we propose a strategy utilizing strain to impose intramolecular tension in already peripherally overcrowded structures leading to selective atropisomeric conversion. Employing this approach, tuneable shape‐persistent porphyrin conformations were acquired exhibiting distinctive supra...
Citations
Cite this article: Kohnhorst, S. A. (2022, May). Supramolecular structure of five-coordinate [(4-methyl-2,6-dinitrophenolato)(octaethylporphinato)iron(III)] heme complex. Abstract The crystallographic and spectroscopic characterization of the phenolate complex of [(4-methyl-2,6-dinitrophenolato)(2,3,7,8,12,13,17,18-octaethylporphinato)Fe(III)], [Fe III (OEP)(DNOC)] is reported. The 4-methyl-2,6-dinitrophenol (DNOC) ligand was coordinating with the Fe III (OEP) moiety through the phenylato-O-atom. The complex crystallizes in the triclinic P-1 with Z=2. The crystallographic information showed the average Fe-Np distance of 2.053(18) Å, with the Fe displacement from the 24 atoms porphyrin plane of 0.41(6) Å, and the Fe-O distance of 1.881(15) Å showing a five-coordinate square-pyramidal geometry. The characteristic of the formation of the Fe-O bond was found near 537 cm-1 for IR spectra and the 4 band was near 534 cm-1 for Raman spectra. The major supramolecular interactions involved an intermolecular hydrogen bond C-H···O with a minimum distance of 2.732(5) Å, and the shortest plane-plane contact distance of 3.689(3) Å. The FT-IR characteristic showed the new band near 3400 cm-1 , which was broadened due to the formation of hydrogen bonds. The role of these weak C-H···O hydrogen bonds concerted to stabilized the crystal packing in the heme complex. Thus, the number of excellent hydrogen bond acceptors of the axial ligand contributes to its supramolecular structure.
Porphyrins are variously substituted tetrapyrrolic macrocycles, with wide-ranging biological and chemical applications derived from metal chelation in the core and the 18π aromatic surface. Under suitable conditions, the porphyrin framework can deform significantly from regular planar shape, owing to steric overload on the porphyrin periphery or steric repulsion in the core, among other structure modulation strategies. Adopting this nonplanar porphyrin architecture allows guest molecules to interact directly with an exposed core, with guest-responsive and photoactive electronic states on the porphyrin allowing energy, information, atom and electron transfer within and between these species. This functionality can be incorporated and tuned by decoration of functional groups and electronic modifications, with individual deformation profiles adapted to specific key sensing and catalysis applications. Nonplanar porphyrins are assisting breakthroughs in molecular recognition, organo- and photoredox catalysis; simultaneously bio-inspired and distinctly synthetic, these molecules offer a new dimension in shape-responsive host-guest chemistry. In this review, we have summarized the synthetic methods and design aspects of nonplanar porphyrin formation, key properties, structure and functionality of the nonplanar aromatic framework, and the scope and utility of this emerging class towards outstanding scientific, industrial and environmental issues.
Recently prochiral solvating agents (pro-CSA) became a spotlight for the detection of enantiopurity by NMR. Chemical shift non-equivalency in achiral hosts introduced by the presence of chiral guests yields observable resonance signal splitting (Δδ) correlating to the enantiomeric excess (e.e.). In this work, symmetry is our lens to explain porphyrin-based supramolecular receptor activity in a chiral environment. Based on extensive NMR analyses of the atropisomeric receptors, the host symmetry is shown to be affected by porphyrin nonplanarity and further desymmetrized in the presence of a chiral guest. As such, the exposed porphyrin inner core (N–H), with its strong hydrogen bond abilities, for the first time, has been exploited in enantiomeric composition analysis. Our approach in e.e. detection by N–H signals appearing in a previously underutilized region of the spectrum (below 0 ppm.), shows chemical shift splitting (Δδ) three times more sensitive to enantiomeric compositions than previously reported systems.
Recently prochiral solvating agents (pro-CSA) became a spotlight for the detection of enantiopurity by NMR. Chemical shift non-equivalency in achiral hosts introduced by the presence of chiral guest yields observable resonance signal splitting correlating to the enantiomeric excess (e.e.). In this work, symmetry is our lens to explain porphyrin-based supramolecular receptors’ activity in a chiral environment. Based on extensive NMR analyses of the atropisomeric receptors, host symmetry is shown to be affected by porphyrin nonplanarity and further desymmetrized in the presence of a chiral guest. We have formulated a simple, symmetry-based protocol that can be used to identify pro-CSA candidates. As such, the exposed porphyrin inner core (N–H), with its strong hydrogen bond abilities, for the first time, has been exploited in enantiomeric composition analysis. Our approach in e.e. detection by N–H signals appearing in a previously underutilized region of the spectrum (below 0 ppm.), shows chemical shifts (the e.e. dependent splitting) three times more sensitive to enantiomeric compositions than previously reported systems. The findings are complemented by extensive 2D NMR studies, including the first reporting of e.e. dependent in non-hydrogen NMR, and supporting by density functional theory (DFT) calculations.
