Calix[4]pyrroles as ligands: recent progress with a focus on the emerging p-block element chemistry

Abstract

Calix[4]pyrroles are readily synthesized in one step from pyrroles and ketones. For several decades, these macrocycles have been exploited as powerful anion receptors or ligands for transition and rare-earth metals....

Calix[4]pyrrolato gallate: square planar-coordinated gallium(iii) and its metal–ligand cooperative reactivity with CO2 and alcohols

“…1A ). 17 While a close-to-planar neutral tetracoordinated gallium atom was recently reported in a pyridine diimine-supported complex, 18 anionic and truly square planar-coordinated gallium, and the reactivity of this compound class, remains elusive.…”

Recent developments in calix[4]pyrrole (C4P)-based supramolecular functional systems

“…In another report, the research team of Wezenberg installed a photo-switchable stiff-stilbene moiety as a strap to construct a photo-switchable strapped C4P-based chloride ion receptor (20), commencing from an easily accessible starting material, namely 6-carboxy-1-indanone ( 14), as detailed in Scheme 1. 77 The 1 H-NMR, UV-Vis and ITC studies carried out in acetonitrile and DMSO solvents confirmed that the strapped C4Pbased receptor (20) in its Z-isomeric form exhibited strong binding affinity (K a = 1.6 × 10 5 M −1 ) towards the chloride anion, as the tetrabutylammonium (TBA) salt, thereby constructing an anion-receptor complex (21 − ). However, the photo-switching of 21 − from the Z-form into the E-isomeric form through irradiation at 365 nm developed strain in the stiff-stilbene strap, and hence drastically reduced the binding affinity of 20 towards a chloride anion (K a = 2.0 × 10 2 M −1 ), as revealed by 1 H-NMR titrations (Scheme 1).…”

“…[1][2][3][4][5][6][7][8] Among the numerous supramolecular receptors, 9,10 the non-aromatic tetrapyrrolic synthetic macrocyclic receptor (C4P) has emerged as significant receptor and ligand for diverse purposes owing to its structural variety, easy one-pot synthesis, and recognition ability towards anions, ion-pairs, neutral molecules, and metal ions of fundamental importance. [11][12][13][14][15][16][17][18][19][20][21][22][23] Adolf von Baeyer (1835-1917, a German Chemist, Noble Prize in Chemistry, 1905) is credited for the discovery of the parent C4P in 1886 through the acid-mediated condensation of pyrrole with acetone in a single step (Fig. 1).…”

Calix[4]pyrrolato Stannate(II): A Tetraamido Tin(II) Dianion and Strong Metal‐Centered σ‐Donor

“…More recently, the calix[4]pyrrole ligand enabled the synthesis of planar, tetracoordinated Al III[16] and Si IV[17] complexes and transferred concepts like element ligand cooperativity, ligand‐to‐metal‐charge‐transfer and C−H agostic interactions into the p ‐block. [18] However, no complexes of calix[4]pyrroles with low‐valent p ‐block elements have been described so far. Herein we present the synthesis of calix[4]pyrrolato stannate(II) [2] 2− as the first dianionic, tetraamido Sn II , and its chemistry as a nucleophile and strong σ‐donor.…”