Macrocyclic Ligands - Web del Profesor

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