Polyamine macrocyclic ligand

Complexation of Cd with a series of polyamine macrocycles, but also related open-chain polyamines, comprising or attached to the 2,2 -bipyridine (bipy) and 1,10-phenanthroline (phen) moieties, has been studied by combined UV/vis spectrometry and potentiometry.24 Formation constants and distribution diagrams of the species present have been evaluated. As a result the thermodynamic stabilities, i.e., the formation constants, are lower for the bipy- and phen-contain-ing ligands than those for Cd complexes with aliphatic oligoaza macrocycles containing the same number of N donors. The probable reason is loss of flexibility of the ligands caused by the size and stiffness of the inserted heteroaromatic moieties. 

The deprotection of the polyamine-thioethers 40a,b can also be accomplished in similar good yields with Li/naphthalene in THF (214). Cleavage of the thioether functions also commenced with [PdCl2(NCMe)2] in the case of 40b (216), and it is likely that the other macrobicycles will also undergo this metal-ion mediated cleavage reaction as well (Scheme 2). Note that this reaction cleaves only one of the two thioether bonds forming a macrocyclic ligand with one thiophenolate and one vinyl-thioether moiety, as... 

Fig. 32. Mononuclear Ni(II) and Zn(II) complexes of acyclic and macrocyclic polyamine-thiophenolate ligands (224).

The Cr—C bond exerts a considerable (ca. 0.1 A) solid-state trans elongation (Table I), and the trans effect is implicated in the enhanced substitution lability of the trans aqua ligand. A variety of chelating systems can be used to form [L6CrR]2+ cations, including diamines (63), polyamines, macrocyclic N4 ligands, acac, bipy, and polycarboxylates such as nta, edta (64), and hedtra. 

A 1,10-phenanthroline-containing polyamine macrocycle (78) was designed to complex with Zn2+ ion and, because of the rigidity of the phenanthroline moiety, leave some free binding sites at the metal for ligands such as water, which easily depro-tonate to give stable hydroxo species. The hydrolysis of methyl acetate in the gas phase by such a monohydroxy-Zn(II) complex [Zn(78)(OH)]+ has been investigated by quantum mechanical procedures and some pathways delineated.78... 

The in situ synthesis of macrocyclic ligands by condensation of 2,6-diacetylpyridine with polyamines in the presence of metal ions represents one of the early demonstrations of the template effect . Curry and Busch reported the first penta-and hexadentate macrocycles (79 and 80)47), both of which are cyclized in the presence of iron(II) chloride tetrahydrate. The two ligands were isolated as highly... 

There are also systematic trends in stability constants when frve-memberedpolyamine rings are replaced by six-membered rings, or when linear polyamine ligands are replaced by macrocyclic ligands of a similar strain see Chelate Effect). These effects can be well accounted for in terms of enthalpy contributions to the formation constant. ... 

In some of the earliest experiments involving in situ macrocyclic ligand synthesis, it was shown that the reaction of 2,6-diacetylpyridine with certain polyamines in the presence of metal ions leads to the preparation of new macrocyclic complexes. As is often the case with Schiff-base condensations of the type, the addition of a small amount of acid catalyzes the reaction. Thus treatment of 2,6-diacetylpyridine with 3,3 -diaminodipropylamine [A-(3-aminopropyl)-l,3-pro-panediamine] in the presence of nickel(II) leads to the isolation of nickel complexes of the macrocyclic ligand (Me2-Pyo[14] trieneN4). " ... 

The uses of the aza-erown macrocycles are multiplying as shown above. New research is reported almost daily. The titles of a few recent articles are instructive (1) Macrocyclic Polyamines [IbjN, and [21]N4 Synthesis and a Study of Their ATP Complexation by P Nuclear Magnetic Resonance Spectroscopy (Prakash et al., 1991) (2) Removal of Dyes from Solution with the Macrocyclic Ligands (Buschmann et al., 1991a, 1991b) (3) Iron-Cyclam Complexes as Catalysts for the Epoxidation of Olefins by 30% Aqueous Hydrogen Peroxide in Acetonitrile and Methanol (Nam et al.,... 

Cabbiness and Margerum have given preliminary accounts of the effect of macrocyclic structures on the rate of formation and dissociation of Cu + complexes. They have compared the rates of reaction of aquo-copper with the somewhat flexible fourteen-membered macrocyclic ligand shown (7 also similar macrocycles), with a comparable open-chain polyamine (2,3,2-tet), and with a porphyrin ligand (haematoporphyrin... 

Eabbrizzi has also reported an assay (IDA) for the recognition of His, in this case based on a dicopper complex and polyamine macrocycle 51, in combination with three different dyes. A Cu(II) complex was also described by Anslyn for the sensing of His, although, in this case, the mechanism is the metal stripping from a ligand-Cu-fluorescein complex by His to form a 2 1 His Cu(II) complex, with the concomitant release of free unquenched fluorescein. ... 

The S-oxygenation of the hexaamine-dithiophenolate macrocycles should provide a potential entry into the novel class of binucleating polyamine-disulfonate and -disulfinate macrocycles. Indeed, such ligands can be prepared by the oxidation of dinuclear nickel complexes of the parent hexaaza-dithiopheno-late macrocycles followed by the decomposition of the oxidation products in acidic solution. The dinuclear nickel complexes [Nin2(L36)(L )]+ (L = Cr (70) and OAc (71)) of the hexaaza-diphenylsulfonate ligand (L36)2- (Fig. 38) are obtained by... 

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