Catalytic Applications of Pyridine‐Containing Macrocyclic Complexes

Abstract

The introduction of a pyridine moiety into the skeleton of a polyazamacrocyclic ligand affects both the thermodynamic properties and the coordination kinetics of the resulting metal complexes. These features have attracted great interest from the scientific community in recent years. The field of application of pyridine‐containing macrocyclic ligands ranges from biology to supramolecular chemistry, encompassing MRI, molecular recognition, materials and catalysis. In this microreview we provide a perspective of the catalytic applications of metal complexes of pyridine‐containing macrocycles, including an account of investigations from the authors' laboratories dealing with stereoselective C–C and C–O bond‐forming reactions. The increased conformational rigidity imposed by the pyridine ring allowed for the isolation and characterisation of metal complexes in high oxidation states and the study of their relevance in oxidation reactions. On the other hand, the very different conformations accessible upon the metal coordination and the easily tuneable synthesis of the macrocyclic ligands have been exploited in stereoselective synthesis.

Controlling Selectivity in Alkene Oxidation: Anion Driven Epoxidation or Dihydroxylation Catalysed by [Iron(III)(Pyridine‐Containing Ligand)] Complexes

“…13 C NMR analyses were performed with the same instruments at 75.5, and 100 MHz, and attached proton test (APT) sequence was used to distinguish the methine and methyl carbon signals from those arising from methylene and quaternary carbon atoms. The glassware was previously dried in an oven at 110°C and was set with cycles of vacuum and nitrogen.…”

“…The coupling constants (J) are expressed in hertz (Hz), and the chemical shifts (δ) in ppm. 13 C NMR analyses were performed with the same instruments at 75.5, and 100 MHz, and attached proton test (APT) sequence was used to distinguish the methine and methyl carbon signals from those arising from methylene and quaternary carbon atoms. All 13 C NMR spectra were recorded with complete proton decoupling.…”

“…The 1 H NMR signals of the ligand described in the following have been attributed by correlation spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) techniques. Assignments of the resonance in 13 C NMR were made using the APT pulse sequence and heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) techniques. EPR measurements were performed on powder samples with a Bruker ELEXSYS spectrometer equipped with an ER4102ST standard regular cavity at X band (9.55 GHz) frequency at room temperature and at 77 K using a cold finger Quartz Dewar cooled by liquid nitrogen, The derivative dP/dHof power P adsorbed was recorded as a function of the static magnetic field H. Low resolution MS spectra were recorded with instruments equipped with electron ionization (EI), ESI/ion trap (using a syringe pump device to directly inject sample solutions), or fast atom bombardment (FAB) (for Pc-L and metal complexes) sources.…”

“…In the past few years, we have reported the synthesis of a series of pyridine-based 12-membered tetraaza-macrocyclic ligands (Pc-L) [13] and the application of their copper(I) [14] and silver(I) [15] complexes in catalysis. Spurred by the very recent reports on the generation of a highly reactive iron species by reaction of peracetic acid with a ferrous complex ([Fe II (CF 3 SO 3 ) 2 (PyNMe 3 )], Figure 1a), [16] we became interested in exploring the coordination properties of our Pc-L ligands with iron.…”

Sensing Zn2+ in Aqueous Solution with a Fluorescent Scorpiand Macrocyclic Ligand Decorated with an Anthracene Bearing Tail

“…Scorpiand type aza-macrocyclic ligands, that is aza-macrocyclic ligands with coordinating tails [1], and their metal complexes have attracted considerable interest thanks to the numerous uses they have been tested for, including but not limited to various biomedical applications [2,3] (MRI contrast agents [4,5], radioisotopes complexation and radiolabelling [6][7][8][9], radiotherapy [10][11][12][13][14], chelation therapy [15][16][17], antiproliferative treatments [18][19][20][21], enzyme mimicking [22][23][24][25][26][27][28][29]), catalysis [30][31][32][33][34][35][36] and chemosensing [37][38][39][40][41][42][43].…”