Polyamine Containing Complexes

For the bis-complex of diethylenetriamine, [Co(dien)2], three topological isomers, s-fac (trans-/flc), u-fac (cis-fac) and mer, are shown in Fig. 3.12. In addition, the u-fac and rmr isomers are resolvable The complex containing three isomers was prepared by different methods the reaction of [Co(C03)3] and dien in the presence of activated charcoal (A), the reaction of [CoBr(NH3)5] and dien in the presence of activated charcoal (B), aerial oxidation of a Co —dien mixture in the presence of activated charcoal (C), and the reaction of mer-[CoCl3(dien)] and dien in the absence of activated charcoal (D). From a SP-Sephadex column (Na form) with 0.15 mol/dm sodium (+)-tartrate, the fastest moving species was s-fac, the middle one u-fac, and the slowest one mer isomer. The formation ratio of s-fac u-fac mer was found to be 16 25 59 for method A, and 7 30 63 for method B and C. The method D produced only u-fac mer = 8 92. 

These three isomers were separated on a column of P-cellulose, too. When 1-butanol saturated with water served as the solvent, 1-butanol cone. HCl water (200 15 15) eluted mer, s-fac and u-fac in this order. The resolutions of the u-fac and mer isomers were completely achieved on SE-Sephadex with 0.15 mol/dm sodium (-l-)-tartrato-antimonate(III), the (-I-) and (—) enantiomers being eluted in this order. Since the mer isomer racemizes quickly in neutral or alkaline solution, all the operations were performed in an aqueous solution acidified with 0.01 mol/dm HCl. 

By chromatographic separation, Keene and Searle determined equilibrium distributions of the three geometrical isomers of the complex prepared by aerial oxidation over activated charcoal. The results are cited, in part, in Table 3.3. 

Solvent Counterion [Co], M Added salt Isomer proportions % s-fac u-fac mer 

The environmental parameters such as solvent, counterion, added salt and pH more or less affect the isomer proportions. Under the usual preparative conditions at 18 °C, the proportions are s-fac u-facinter = 7 28 65 for aqueous solutions with Cl or Br as anion, indicating the preference of meridional coordination of dien over facial coordination. On the other hand, the addition of an oxy anion, PO4 or SeOf , increases the proportion of the s-fac isomer at the expense of the mer one, the proportion of the u-fac remaining nearly constant. The enhanced proportion of the s-fac is ascribed to the differential specific associations between the oxy anion and the three isomeric cations, the interaction magnitudes being in the order s-fac u-fac mer. This interpretation is similar to the A-[Co(en)3] —POJ ion pair model proposed by Mason and Norman 

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Condensation reactions of aromatic aldehydes with a,cu-polyamines lead to Schiff bases, if the polyamine involved contains only primary amino groups or to imidazolidines, if the polyamine contains a secondary amino group. Condensation of 2-pyridinecarboxaldehyde 7V-oxide with triethylenetetramine yields derivative (31), with two imidazolidine rings, which in the presence of Cu11 undergoes a ring-opening reaction due to the formation of a complex.42... 

The peraza macrocycles, in general, form more stable complexes with a variety of metal ions than do the open-chain polyamines containing the same number of amine groups. This characteristic is called the macrocyclic effect. Triaza-crowri macrocycles, in nearly every case, form 1 1 complexes with metal ions that are thermodynamically more stable than those with dieth-ylenetriamine. Only complexes of the open-chain triamine with and Hg- are more stable than those with the cyclic triamines (Bianchi et al., 1991). Triaza-9-crown-3 (23) forms stronger complexes with most cations than the larger triazacyclodecane (24), triazacycloundecane (25), or triazacyclo-dodecane (26) (Bhula et al., 1988 Chaudhuri and Wieghardt, 1987). 

Dissociation of the polyamine salt adduct must be achieved to liberate the salt and recover the polyamine. With complexes of the N-permethylated polyethylene polyamines, it is convenient (on a small scale) to dissociate the complex by dissolving it in aqueous potassium hydroxide. The tertiary polyamine is generally extracted from this mixture without difficulty. Dissolution of the complexes containing primary polyamines likewise leads to dissociation. However, high solubility of the primary polyamines in water creates a recovery problem. With complexes containing primary amine functions, it is preferable, and generally... 

Thermal dissociation of tren NaBr was studied, and the results are summarized in Table IX. In these experiments thermal dissociation was done by extracting the solid complex in a Soxhlet apparatus with a high-boiling hydrocarbon solvent. The solvent was Isopar G, an isoparaffinic distillation fraction boiling at 159° to 177 °C. During the extraction the hot solvent bathes the complex and causes its dissociation. The insoluble salt is simultaneously separated from the polyamine which dissolves in the hot solvent. When the hydrocarbon-tren solution is cooled, a phase separation occurs since polyamines containing primary (and secondary) nitrogens have low solubilities in paraffins at ambient temperature (5). 

Aliphatic polyamines, amine adducts and polyamides react with epoxide resins at normal temperatures to give complexes with outstanding chemical resistance. Paints based on this type of reaction must be supplied in two separate containers, one containing the epoxide resin and the other the curing agent , the two being mixed in prescribed proportions immediately before use. 

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 dissociation rate constant measures directly the value of k 2 in (4.52). The strain resident in multi-ring complexes is clearly demonstrated by some hydrolysis rate studies of nickel(II) complexes. The AFT values for the first bond rupture for Ni(II)-polyamine complexes fall neatly into groups. They are highest for en, containing the most strain-free ring (84 kJ mol ), about 75 kJ mol for complexes with terdentate ligands and only —63 kJ mol for complexes of quadridentate and quinquedentate amines and with NH3 itself. See also Ref. 109. 

In addition to vitamins and minerals, tubers contain a complex assortment of other small molecules, many of which are phytonutrients. These include polyphenols, flavonols, antho-cyanins, phenolic acids, carotenoids, polyamines, glycoalkaloids, tocopherols, calystegines, and sesquiterpenes. 

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