Binuclear cryptates. Synthesis and binuclear cation inclusion complexes of bis-tren macrobicyclic ligands

SummaryThe crystal structures of four anion cryptates [X-c BT-6H'I formed by the protonated macrobicyclic receptor BT-6H+ with F-, C1-, Br-and N; have been determined. They provide a homogeneous series of anion coordination patterns with the same ligand. The small F--ion is tetra-coordinated, while C1-and Br-are bound in an octahedron of H-bonds. The non-complementarity between these spherical anions and the ellipsoidal cavity of BT-6H+ is reflected in ligand distortions. Structural complementarity is achieved for the linear triatomic substrate N;, which is bound by two pyramidal arrays of three H-bonds, each interacting with a terminal N-atom of N;. The formation constants of the complexes formed by BT-6H' with a variety of anions (halides, N;, NO;, carboxylates, SO:-, HPO:-, AMP2-, ADP3-, ATP4-, P,O:-) have been determined. Very strong complexations are found, as well as marked electrostatic and structural effects on stability and selectivity; in particular the binding of F-, C1-, Br-and N; may be analyzed in terms of the crystal structure data. The cryptand BT-6H+ is a molecular receptor containing an ellipsoidal recognition site for linear triatomic substrates of size compatible with the size of the molecular cavity. Further developments of various aspects of anion coordination chemistry are considered.

show abstract

“…The synthesis of the macrobicyclic molecule BT has been reported earlier [16] mole) in 5 ml EtOH was added. Precipitation rapidly occurred.…”

Section: Experimental Partmentioning

confidence: 99%

Molecular Recognition in Anion Coordination Chemistry. Structure, Binding Constants and Receptor‐Substrate Complementarity of a Series of Anion Cryptates of a Macrobicyclic Receptor Molecule

Dietrich¹,

Guilhem

Lehn³

et al. 1984

Helvetica Chimica Acta

225

115

View full text Add to dashboard Cite

show abstract

“…The macrocyclic Obisdien used was synthesized by a modification of the method previously described 5,6 . Zinc (II) nitrate hexahydrate (Zn(NO3)2.6H2O), magnesium(II) nitrate hexahydrate (Mg(NO3)2.6H2O), HCl, sodium sulfate, sodium selenite and sodium selenate, were reagents grade materials.…”

Section: Methodsmentioning

confidence: 99%

Equilibrium studies of ternary complexes formed by bromide, sulfate, selenite and selenate ions with Zn2+, Mg2+ and 1, 4, 7, 13, 16, 19-hexaaza- 10, 22- dioxacyclotetracosane (obisdien)

Silva¹,

Lamotte²,

Donard³

et al. 1997

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

SeO3²> SO4(2-) > Br-. O sistema envolvendo os complexos de Obisdien:Mg(II) apresenta três espécies com o íon brometo, quatro espécies com o íon sulfato, cinco espécies com o íon selenito e cinco com o íon selenato. A variação da constante de associação para este sistema é o mesmo observado no sistema anterior: SeO4(2-) > SeO3² > SO4(2-) > Br-. Cálculos de mecânica molecular mostram que os complexos de Obisdien dizinco(II) e dimagnésio(II) adotam várias conformações de baixa energia com diferentes separações Zn-Zn e Mg-Mg permitindo a coordenação dos ânions SeO4(2-), SeO3(2-), SO4(2-), Br- e OH-.]]>

show abstract

“…Our own work on dinuclear macrocyclic cryptates has been concerned mainly with ligands containing two chelating subunits of the diethylene triamine type: the hexaaza-dioxacompound [241-N6o2, 1,and the two macrocycles bearing two diagonally disposed pyridine groups A precursor of macrocycle had been described earlier (15); another route has now also been developped (16). The synthetic scheme leading to compound is shown in Figure 4; a similar path has been used for compound (17 (20).…”

Section: El) J)mentioning

confidence: 99%

Dinuclear cryptates: dimetallic macropolycyclic inclusion complexes: concepts - design - prospects

Lehn¹

1980

Pure and Applied Chemistry

276

100

View full text Add to dashboard Cite

-Macropolycyclic structures possessing receptor sites for several substrates may present a variety of new properties compared to single site receptors. Inclusion of two metal cations yields dinuclear cryptates in which the geometrical arrangement and the properties of the cations depend on the features of the ligand: the nature of the binding sites, of the subunits by which the cations are complexed, of the framework which connects the subunits. Three main classes of macropolycycles are considered: bis-chelating macrocycles, macrobicycles of either axial bis-tripodal or lateral chelating-macrocyclic type, cylindrical macrotricycles. The design of these structures is analyzed with respect to the choice and effect of binding sites, subunits and framework,on the properties of the cryptates foriied complexation and redox features, cation-cation interaction at short distances, formation of cascade complexes by fixation of substrates on the bound cations. Dinuclear cryptates of each type have been obtained, as well as several bridged species. Their structural, physical and chemical properties are discussed. The prospects of these type of complexes are outlined especially with respect to the design of polynuclear cryptates, catalysis of multicenter-multielectronic processes, biomimesis of metalloproteins and of biological redox processes.Macropolycyclic structures are able to provide suitable frameworks for the arrangement in space of several receptor sites, allowing the binding of several substrates or the multiple binding of a single polyfunctional substrate. They delineate molecular cavities into which the substrates penetrate, forming inclusion complexes, cryptates, whose geometry may be regulated via ligand design (1). In addition to the functions displayed by single site (monotopic) molecular receptors (1) (recognition, catalysis, transport), the simultaneous or successive participation of several sites to substrate binding by multisite (polytopic) receptors provides an entry into higher forms of molecular behaviour, cooperativity, allostery and regulation. Such co-systems may display successive binding of different substrates yielding "cascade" complexes (2-5).Polytopic receptors may be symmetric or dissymetric, contain equivalent or non-equivalent binding subunits; they may complex identical (homonuclear complexes) or different (heteronuclear complexes) substrates , inorganic metal cations, organic or biological molecular cations, inorganic or organic molecular anions as well as neutral molecules.Among the great variety of species which can be imagined, we shall limit our present discussion to dinuclear complexes formed by inclusion of two metal cations into a macropolycyclic ligand containing two binding subunits, i.e. the topic will be concerned with our work on dinuclear cryptates of metal cations.In these complexes, the distance and arrangement of the cations may be monitored via the design of the ligand. They provide a novelapproach to the study of cation-cation 2441 Unauthenticated Download Date ...

show abstract

Binuclear cryptates. Synthesis and binuclear cation inclusion complexes of bis-tren macrobicyclic ligands

Cited by 133 publications

References 0 publications

Molecular Recognition in Anion Coordination Chemistry. Structure, Binding Constants and Receptor‐Substrate Complementarity of a Series of Anion Cryptates of a Macrobicyclic Receptor Molecule

Molecular Recognition in Anion Coordination Chemistry. Structure, Binding Constants and Receptor‐Substrate Complementarity of a Series of Anion Cryptates of a Macrobicyclic Receptor Molecule

Equilibrium studies of ternary complexes formed by bromide, sulfate, selenite and selenate ions with Zn2+, Mg2+ and 1, 4, 7, 13, 16, 19-hexaaza- 10, 22- dioxacyclotetracosane (obisdien)

Dinuclear cryptates: dimetallic macropolycyclic inclusion complexes: concepts - design - prospects

Contact Info

Product

Resources

About