Macrotricycles cylindrical

Macropolycyclic ligands, 2,942 classification, 2,917 metal complexes binding sites, 2, 922 cavity size, 2,924 chirality, 2, 924 conformation, 2,923 dimensionality, 2, 924 electronic effects, 2, 922 shaping groups, 2,923 structural effects, 2,922 molecular cation complexes, 2,947 molecular neutral complexes, 2,952 multidentate, 2,915-953 nomenclature, 2,920 Macro tetrolide actins metal complexes, 2,973 Macrotricycles anionic complexes, 2,951 cylindrical... 

Multidentate Macrocyclic and Macropolycyclic Ligands 21.3.5.3 Macrotricycles 21.3.5.3.1 Cylindrical macrotricycles... 

The first cylindrical macrotricyclic ligands synthesized were (52a) and SSa-d).58 70 Cryptands in which the two monocycles are even farther apart as a result of bridging naphthyl, biphenyl and. related groups have also been reported.188,1 9 The smaller macrocycle (52a) forms complexes with a variety of metal cations, including two silver(I) ions.69,70 190 Crystal data results for the latter complex indicate both Ag+ ions are located slightly out of the plane of the macrocycles (undoubtedly the result of macrocyclic size constraints), but within the central main cavity, with an Ag—Ag distance of 3.88 A.191... 

Fig. 2. Some macropolycyclic structures (a) macrocyclic, (b) macrobicyclic, (c) cylindrical macrotricyclic, and (d) spherical macrotricyclic. L-j- = 5, 8, 8 and 9, respectively [1.27].

For dissymmetric cylindrical macrotricyclic coreceptors that bind ammonium ions see A. D. Hamilton and P. Kazanjian, Tetrahedron Lett. 1985,26, 5735 K. Saigo, R.-J. Lin, M. Kubo, A. Youda and M. Hasegawa, Chem. Lett. 1986,519. 

Macrotricyclic cryptates may have either spherical or cylindrical topology (90). The cylindrical ligands, such as 5, are formed by linking together two macrocycles and define three cavities, two lateral and one central cavity inside the macrotricycle (18,19,91, 92). The macrotricyclic ligands of spherical topology are Particularly well suited for com-plexation of alkali cations as they define a spherical cavity (93, 94). Ligand 10, for example, contains a spherical cavity (diameter 3.4 A)... 

The high-dilution method (for technical details see for example Ref. 21) has been used not only to form simple cryptands, but also in the syntheses of more complex systems — cylindrical macrotricyclic molecules24), lateral macrobicycles 25), spherical macrotetracyclic systems 26), and speleands 27). Nevertheless, the important drawback of the method is the last step, e.g. reduction with diborane. That means only compounds which do not interfere with this reagent can be formed in this manner. Also, even a small contamination of the solvents and reactants with water has a significant influence on the yield. 

Ballardini et al. have reported detailed photophysical studies with a cylindrical macrotricyclic receptor (Figure 77) and its complexes with protons, ammonium ions and [Pt(NH3)2(bipy)]2+ [103],... 

The ability of monocyclic crown-ether derivatives with steric barriers to discriminate [47,48] between MeNH and MejCNH cations has already been discussed. Recently the cylindrical doubly bridged macrotricycles [59,60,61] (31-40) and the triply bridged macrotetracycle [62] (41), based upon the iV, A -diaza-12-crown-4 and -15-crown-5, and the A, A -diaza- and A/, A, A"-triaza-18-crown-6 units shown in Fig. 4, have been found to exhibit remarkable chain-length selectivity... 

The above-described spherical macrotricyclic cryptand 13 was designed for the ammonium cation, whereas the series of cylindrical macrotricycles 15 (Fig. 15) was... 

Cylindrical macrotricyclic molecules (19) are ditopic coreceptors constructed on two binding subunits, two macrocycles, linked by two bridges. When the macrocycles chosen are able to bind -NHJ groups, diammonium substrates may be expected to form mononuclear dihapto cryptates of type (20) by inclusion into the central molecular cavity of the tricyclic receptor. 

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