Cryptates dinuclear

Similarly, by Schiff-base condensation reactions have been used to generate free cryptands from triamines and dicarbonyls in [2+3] condensation mode. These ligands react with silver(I) compounds to give dinuclear or trinuclear macrocyclic compounds where Ag Ag interactions may be present. Thus, with a small azacryptand a dinuclear complex with a short Ag- Ag distance (55) is found.498 With bigger azacryptand ligands also dinuclear complexes as (56) are achieved but without silver-silver interaction. 65,499-501 A heterobinuclear Ag1—Cu1 cryptate has also been... 

The subject molecules are obtained as dinuclear copper complexes with the octa-aza cryptate ligands L1 and L2 shown in Scheme 1. 

In comparison, both the free ligand and the dinuclear Cu(I) cryptate of an analogous macrobicyclic structure possessing a diphenylmethane group as a central unit display only two resonances for the CH2CH2 fragment, as is the case here only for the complexes 91 and 92. This points to the special conformation features of the free macrobicycles 89 and 90. 

F. Fages, J.-P. Desvergne, H. Bouas-Laurent, J.-M. Lehn, J. P. Konopelski, P. Marsau, and Y. Barrans, Synthesis and fluorescence emission properties of a bis-anthracenyl macrotricyclic ditopic receptor. Crystal structure ofits dinuclear rubidium cryptate, J. Chem. Soc., Chem. Commun. 655(1990). 

Cryptands, 42 122-124, 46 175 nomenclature, 27 2-3 topological requirements, 27 3-4 Cryptate, see also Macrobicyclic cryptate 12.2.2], 27 7-10 applications of, 27 19-22 cylindrical dinuclear, 27 18-19 kinetics of formation in water, 27 14, 15 nomenclature, 27 2-3 spherical, 27 18 stability constants, 27 16, 17 Crystal faces, effect, ionic crystals, in water, 39 416... 

Avecilla, F. de Bias, A. Bastida, R. Fenton, D. E. Mahia, J. Macias, A. Platas, C. Rodriguez, A. Rodriguez-Blas, T. The template synthesis and X-ray structure of the first dinuclear lanthanide(III) iminophenolate cryptate. Chem. Commun. 1999, 125-126. 

Figure 32 Schematic representation of dinuclear cryptates of genera) formula [Ni2L](C104)2...

Fig. 5. Some dinuclear cryptates of macropolycyclic cryptands resulting from connection of chelating, tripodal, and macrocyclic subunits [3.24].

Lateral macrobicycles are dissymmetric by design thus, monoelectronic reduction of the Cu(ll) ion bound to the [12]-N2S2 macrocyclic subunit in the bis-Cu(ll) cryptate 45, gives a mixed valence Cu(i)-Cu(ll) complex [4.6]. Macrotricycle 46 forms a dinuclear Cu(ll) cryptate that acts as a dielectronic receptor and exchanges two electrons in a single electrochemical wave [4.7]. Complexes of type 47 combine a redox centre and a Lewis acid centre for the potential activation of a bound substrate [4.8]. 

Menif, R. Reibenspies, J. Martell, A. E. Synthesis, protonation constants, and copper(II) and cobalt(II) binding constants of a new octaaza macrobicylic cryptand (MX)3crystal structures of the cryptand and of the carbonato-bridged dinuclear copper(II) cryptate, Inorg. Chem. 1991, 30, 3446-3454. 

With the cylindrical cryptands, each macrocycle may bind one cation so that both mono- and dinuclear cryptates may be formed. Although the 12-membered (N202) macrocycles of ligand 5 are too small to bind two cations within each of the macrocycles, variable temperature 13C-NMR measurements have revealed intramolecular cation exchange between identical sites at the top and bottom of this cryptand, for Ca2+, Sr2+, and Ba2+. Cation jump between the two sites is fast with respect to intermolecular cation exchange, modeling the elementary jump processes of cations between binding sites in membrane channels (91). 

Fie. 10. Crystal structure of the dinuclear cryptate (Na -ll C (reproduced with permission). 

Cryptand 193 forms a cryptate containing two copper(II) ions. The reduction potentials of the two ions would be expected to be vastly different, because the Cu2 + complex of 194 is reduced at a potential 500 mV less positive than the Cu2 + complex of 195. This is indeed found to be the case. The dinuclear Cu2+ complex of 193 undergoes a one-electron reduction at +550 mV, The second Cu2+ ion is reduced at +70 mV. Therefore, the first reduction must be that of the Cu2+ ion complexed by the [12]-N2S2 subunit, resulting in the facile formation of a Cu(I)-Cu(II) mixed valence dinuclear cryptate (196). This system suggests the possibility of the formation of heterometallic dinuclear complexes120). 

Many Class II complexes are known for which the EPR signal shows localization occurring at low temperatures (169,170) but only one (167) other synthetic example in which the seven-line signal is still evident at 77 K is known. Delocalization is most evident in systems in which the ligand imposes very similar geometry at both copper centers and the small, dinuclear cryptate achieves this very effectively. The properties observed are those of the encapsulated [Cu(1.5)-Cu(1.5)] unit and are independent of the details of ligand structure. 

Polyaza macrobicyclic cryptands synthesis, crystal structures of a cyclophane type macrobicyclic cryptand and of its dinuclear copper(I) cryptate, and anion binding features, J. Jazwinski, J.-M. Lehn, D. Lilienbaum, R. Ziessel, J. Guilhem and... 

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