Tetramines cyclic

Tetraazaporphyrin, octaphenyl-metallation, 858 Tetraazaporphyrins synthesis, 857 Tetraethylenepentamine metal complexes, 56 Tetraglycine metal complexes, 764 Tetraketones metal complexes, 399 1,3,5,7-Tetraketones metal complexes, 400 Tetramines cyclic... 

Fig. 6 Cyclic voltammogram for an acetonitrile solution initially containing a dimeric Cu 2(L)2 complex involving a tetramine ligand that favors the monomeric Cu" L + upon oxidation. The second cycle, which features both pairs of oxidation and reductions waves, is depicted here. The peaks at lower potential represent the monomeric redox couple while those at the more positive potential are for the dimer. Reproduced with permission from Ref. 125. Copyright 2001 American Chemical Society.

Endicott and coworkers have measured the Cu(III/II) potentials of a few macro-cyclic tetramine complexes in acetonitrile [196-198]. These values are very positive, suggesting that the Cu(III) complexes tend to undergo spontaneous reduction. Margerum and coworkers were the first to demonstrate that Cu(II) complexes with... 

The 12-membered cyclic tetramines, the smallest tetraaza macrocycles, have a cavity size too... 

The tetraza macrocycle (150 LH4), with four ethanoate groups, is readily prepared by treatment of the cyclic tetramine with bromoethanoic acid.1101 Its complex [ZnLH2j utilizes two amino N atoms and two carboxylates as ligands. The fully deprotonated complex may be prepared in solution by treatment with NaOH. 

For many Cu11 tetramine complexes a correlation between the enthalpy of formation and the band maximum in the d-d spectrum has been observed and attributed to the common presence of tetragonal diaquo species.31 Values for cyclic amines follow this correlation, both AHe and the band energy having maximum values for [14]aneN4, with deviations for n — 12 and n = 15 attributable to distortions from tetragonal geometry. 

Complexes of several cyclic tetramines with Ni11 exist in aqueous solution as an equilibrium between singlet ground state, square planar species and triplet ground state, diaquo species (see Table 2).32... 

The rates of the formation reaction (1) in non-aqueous solvents for a variety of cyclic tetramines are comparable with those for non-cyclic polyamines.33 In aqueous solution, where protonated amine species predominate, the rates of reactions (2) are slower for the cyclic amines, the effect becoming more pronounced as the protonation number, I, increases. For different metal ions the rates parallel the water exchange rates (Cu2+ > Zn2+ > Co2+ > Ni2+), and for any particular ion the rates do not vary systematically with ring size.34... 

Table 2 Thermodynamic Date for Complexes of Cyclic Tetramines ...

All hydrocarbons take up nitrogen, forming probably cyclical polyamines methane and ethylene hydrocarbons seem to give tetramines and acetylene hydrocarbons, diamines. 

N-Nitration. RDX, 5, is a cyclic nitramine obtained by the nitration of hexamethylene tetramine (HMT) in the presence of an excess of concentrated nitric acid. RDX is formed by the nitration of the three outside nitrogen atoms of HMT with removal of the internal nitrogen and methylene (-CH2-) groups. RDX is produced along with ammonium nitrate (NH4NO3) and formaldehyde (HCHO) as by-products. However, another molecule of RDX can be produced by adding NH4NO3, HCHO, and acetic acid (Eqs. 12.8 and 12.9) [1]. 

Based on the cyclic-blocking moieties and other substituent groups, subtype-selective muscarinic antagonists can be classified into eight groups (l)tricyclic benzodiazepines, (2) benzothiazepines, (3) quinuclidines, (4) poly-methylene tetramines, (5)indenes, ( 6)sila-difenidols, (7) diphenylacetyloxy derivatives, and (.8) himbacine akaloids. 

Of the actinides, plutonium is potentially a particularly dangerous biological hazard because of the chemical and biological similarities between Pu(IV) and Fe(III). With this similarity in mind, a series of tetracatechol ligands with both linear and cyclic tetramines as backbone were synthesized in accordance with the general scheme outlined above 24,118) (see Fig. 7a and b). The eight-coordinate nature of Pu(IV)... 

According to the modular approach, components of the fluorosensor can be changed at will. For instance, it could be of some interest to replace the quad-ridentate receptors of systems 4 and 5 by their cyclic counterparts, to obtain 6 and 7 [8]. The reason of the interest is that, ceteris paribus, cyclic ligands form more stable metal complexes than their open-chain analogues (the thermodynamic macrocyclic effect [12]). The tetramine receptor in 6 has the skeleton of the classical 14-membered macrocycle cyclam, whereas the receptor subunit of 7 refers to the other well-known object of macrocyclic chemistry dioxocyclam. 

An even more convincing demonstration of the complexation selectivity of sodium iodide for the branched tetramine, iso-HMTT, was obtained in the second experiment. The polyamine mixture in that instance contained 9.2% iso-HMTT along with 82% n-HMTT and 9.1% of the combined cyclic TMTT isomers. The sample also contained traces of TMED and PMDT (Compounds 1 and 2 in Table I) it represents a typical N-permethylated commercial TETA fraction. In this case, complexation with ca. 7.7 mole % sodium iodide suspended in benzene gave a polyamine chelate that still contained 97.3% iso-HMTT. 

In another experiment involving an initial tetramine mixture similar to that used in experiment 2 of Table IV, virtually all the iso-HMTT was removed by complexation with sodium iodide in pentane. Fractional vacuum distillation of the remaining tetramine mixture separated n-HMTT from the cyclic TMTT isomers. Gas-chromatographic analysis showed that the polyamine recovered this way was more than 99% n-HMTT. 

Polyalkylene polyamines are typical by-products in the amination of dihydroxy compounds. Some of these oligomers, e. g. diethylenetriamine and triethylene-tetramine, are valuable compounds they are produced industrially from ethanol-amine (sometimes directly from ethylene oxide) and ammonia or a mixture of ammonia and ethylenediamine. Over a Ni-Re boride catalyst the selectivity for diethylenetriamine was ca 25 %, almost independent of the conversion [27]. Higher temperatures favored the formation of worthless cyclic products, mainly piperazine and its N-alkylated derivatives (Scheme 9). Recycling the cyclic byproducts can minimize their formation and the higher oligomers can be decomposed to useful dimers and trimers [26]. 

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