Macrocycles amines

Tolman (144, 202) and Wieghardt (203, 204) and their co-workers used amine macrocycles with a 1,4,7-triazacyclononane backbone and one, two, or three phenol pendent arms (Table VIII). In all cases, square-base pyramidal (phenolate)copper(II) precursor complexes were isolated and in many instances structurally characterized by X-ray crystallography. Depending on the number of coordinated phenolates, these complexes are reversibly one-electron oxidized yielding the (phenoxyl)copper(II) species that were characterized in solution by UV-vis, EPR, and RR spectroscopy. 

A Ru =0 complex with a Nspy (N = tertiary amine) macrocyclic ligand, [Ru (0)(CR-... 

In addition to their thermodynamic stability, complexes of macrocyclic ligands are also kinetically stable with respect to the loss of metal ion. It is often very difficult (if not impossible) to remove a metal from a macrocyclic complex. Conversely, the principle of microscopic reversibility means that it is equally difficult to form the macrocyclic complexes from a metal ion and the free macrocycle. We saw earlier that it was possible to reduce co-ordinated imine macrocycles to amine macrocyclic complexes in order to remove the nickel from the cyclam complex that is formed, prolonged reaction with hot potassium cyanide solution is needed (Fig. 6-24). 

Receptors for anions vary widely, and are in many instances either the same or modified versions of the ligands that bind transition metal ions [5-20], For example, poly amine macrocycles can bind transition metal ions, while poly ammonium macrocycles bind anions. In many instances the same ligand can bind either a transition metal ion [21-24] or an anion [25-29],... 

Hossain, M. A. Kang, S. O. Powell, D. Bowman-James, K. A new class of amide/quatemized amine macrocycles and die chelate effect, Inorg. Chem. 2003, 42, 1397-1399. 

More recently, a series of amido-amine macrocyclic receptors, 40-43, was developed by Bowman-James et al. (Scheme 9.9). Because of the presence ofboth binding motifs, these receptors, like many of their congeners, were seen to bind dihydrogen... 

Fig. 4 Thermodynamic macrocyclic effect complexation equilibria involving the Nin aqua.ion and the champions of non-cyclic tetra-amines 1 (2.3.2-tet) and of the tetra-amine macrocycles 2 (cyclam)...

It is interesting to note that the geometry and stability of the model complex are more important than the particular identity of the donors in modeling the hydrolytic zinc enzymes. Ligands such as L2 (32) appear to be closer mimics of the active site donors than the amine macrocycles but the water molecule in [Zn(L2)(H20)] " has a p/C, of 8.3. 

Kinetically inert low-spin cobalt (III) clathrochelates are reversibly reduced by accepting one electron to yield kinetically labile cobalt(II) complexes. In the case of the usual amines (for instance, ammonia), the reduction is, as a rule, accompanied by irreversible decay of the amine cobalt complex. This reaction is slower for chelating amines macrocyclic and especially macrobicyclic amines produce complexes with cobalt(II) ion that are stable over a long time. This fact facilitates the study of the reduction of cobalt(III) complexes to cobalt(II) ones. In most cases, the reactions of macrobicyclic ligands do not interfere with this process. 

It is noteworthy that extraction may be both a research tool and an ultimate goal in host-guest chemistry, the latter case being still rather rare. As a tool, extraction is common since the works of Cram and co-workers [28-33], who introduced and widely used it for the determination of association constants for amine-macrocycle complexation (see also the review by Cram and Trueblood in Ref. 8). This technique may be summarized as follows. 

Tanaka K, Asakura A, Muraoka T, Kalicki P, Urbanczyk-Lipkowska Z. Asymmetric direct aldol reactions catalyzed by chiral amine macrocycle-metal(II) complexes under solvent-free conditions. N J Chem 2013 37 2851-5. 

The macrocycle 51 can be converted into 52 by addition of an excess of Cd salt to the complex of 51 with Ba. Upon reduction with NaBH4, the resulting [3 + 3] amine macrocycle was the only product observed [55]. 

Electrochemical detection has matured considerably in recent years and is routinely used by many laboratories, often for a very specific biomedical application. The most popular applications include acetylcholine, serotonin, catecholamines, thiols and disulfides, phenols, aromatic amines, macrocyclic antibiotics, ascorbic acid, nitro compounds, hydroxylamines, and carbohydrates. As the last century concluded, it is fair to say that many applications for which LC-EC would be an obvious choice are now pursued with LC-MS-MS. This only became practical in the 1990s and is clearly a more general method applicable to a wider variety of substances. In a similar fashion, LC-MS-MS has also largely supplanted LC-F for new bioanalytical methods. Nevertheless, there remain a number of key applications for these more traditional detectors known for their selectivity (and therefore excellent detection limits). 

The interlocking of secondary amines with polyether macrocycles enables amines to activate H2 in the presence of B(CgF5)3. DF calculations show that the amine-macrocycle complex both preorganizes a frustrated Lewis pair minimum for H2 activation and stabilizes the product through strong hydrogen bonds. ... 

The Crowns were found in the U.S.A. The Cryptates , a more recent French discovery, are mixed ether-amine macrocycles that not merely encircle the salts of inorganic cations, as Crowns do, but actually surround them in all directions, leading to somewhat tighter binding (Lehn, Sauvage, and Dietrich, 1970), and to very strong binding of strontium vts d vis calcium. Of the alkali metals, potassium is often preferred to sodium and lithium. 

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