Macrocyclic Ligands - Web del Profesor
Macrocyclic Ligands - Web del Profesor
Macrocyclic Ligands - Web del Profesor
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2.1.5 Bis-Macrocycles<br />
Bis-macrocycles (10) provide another mechanism for<br />
achieving complexation of more than one metal ion. They<br />
are joined by a bridge linking two simple macrocycles. 13,23<br />
Me<br />
N N<br />
N<br />
N<br />
(CH 2) 2<br />
N<br />
Me<br />
(10)<br />
2.2 Polythia, Polyphospha, and Polyarsa Macrocycles<br />
Polythia macrocycles (11), the thioether analogs of the<br />
crown ethers, have been known since the 1930s. 24 These are<br />
the most extensively studied macrocycles in line after the<br />
polyoxa and polyaza macrocycles.<br />
S<br />
S<br />
S<br />
S<br />
N<br />
(11) (12)<br />
The ‘pure’ polyphospha macrocycles (12) (as opposed to<br />
the mixed donor phospha macrocycles) were first reported in<br />
1975. 25 These macrocycles have been found to complex a<br />
variety of transition metals, but have not received the same<br />
attention as the more readily accessible polyaza and polyoxa<br />
macrocycles.<br />
The polyarsa macrocycles (13) comprise one of the least<br />
common type of macrocycles. 26<br />
P<br />
P<br />
P<br />
P<br />
As<br />
As<br />
As<br />
MACROCYCLIC LIGANDS 3<br />
(13)<br />
2.3 Mixed Donor Macrocycles<br />
As<br />
As<br />
As<br />
2.3.1 Simple Mixed Donor Macrocycles<br />
The simple mixed donor macrocycles (14) at one time were<br />
the major source of study of the influence of the incorporation<br />
of ‘soft’ phosphorus and arsenic donors into macrocycles. 27<br />
Mixed oxygen–nitrogen macrocycles have been studied quite<br />
extensively, since they serve as bridges for examining the<br />
coordination tendencies of the aza macrocycles and the oxa<br />
crown ethers. 13<br />
P<br />
P<br />
2.3.2 Cryptands<br />
O<br />
O<br />
HN<br />
HN<br />
HN<br />
N<br />
O<br />
O O<br />
O<br />
(14) (15)<br />
Cryptands (15) are bicyclic macrocycles which can contain<br />
a variety of donor atoms with bridgehead nitrogen atoms. 5<br />
They are highly selective for alkali and alkaline earth<br />
metal ions.<br />
2.3.3 Compartmental <strong>Ligands</strong><br />
Compartmental ligands (16) are macrocyclic ligands (as<br />
well as nonmacrocyclic ligands) which contain ‘compartments’<br />
for housing more than one metal ion. 28 Only the<br />
macrocyclic counterparts will be treated here.<br />
O<br />
O<br />
N