Metal nitrilotriacetates

Firestone MK, JM Tiedje (1975) Biodegradation of metal-nitrilotriacetate complexes by a Pseudomonas species mechanism of reaction. Appl Microbiol 29 758-764. 

Kamoto and collaborators [150] designed and synthesized a new tum-on fluorescent probe 54, which is excitable by visible light (kex 490 nm), based on a fluorescein derivative 55. It is composed of a metal-nitrilotriacetic (NTA) complex as the hexahistidine tag recognition site, fluorescein as the fluorophore, and a linker. 

An ionophoretic method was described by Tewari [41] for the study of equilibria in a mixed ligand complex system in solution. This method is based on the movement of a spot of metal ion in an electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of the primary ligand (nitrilo-triacetate) was kept constant, while that of the secondary ligand (penicillamine) was varied. The stability constants of the metal nitrilotriacetate-penicillamine complexes have been found to be 6.26 0.09 and 6.68 0.13 (log K values) for the Al(III) and Th(IV) complexes, respectively, at 35 °C and an ionic strength of 0.1 M. 

Metal nitrilotriacetates React with tryptophan leading to mixed complexes containing the metal, nitrilo-triacetate and tryptophan in the ratio 1 1 1 2)... 

Fig. 15-3 Mixed ligand and multi-dentate complexes (a) a hypothetical Me(OH)Cl° complex (b) nitrilotriacetate chelate of a divalent metal ion in a tetrahedral configuration.

According to R. Brdicka and K. Vesely the carbonyl form of formaldehyde is reduced and the limiting kinetic current is given by the rate of the chemical volume reaction of dehydration. An analogous situation occurs for the equilibria among complexes, metal ions and complexing agents if the rates of complex formation and decomposition are insufficient to preserve the equilibrium. A simple example is the deposition of cadmium at a mercury electrode from its complex with nitrilotriacetic COO"... 

White, V. and Knowles, C., Effect of metal complexation on the bioavailability of nitrilotriacetic acid to Chelatobacter heintzii ATCC 29600, Arch Microbiol, 173 (5), 373-382, 2000. 

Use transition metal sequestrants such as phosphonates or nitrilotriacetic acid in the formulation containing peroxygen bleaches, since transition metals can catalyze the decomposition of peroxide. 

Avoid using builders like sodium nitrilotriacetate or sodium tripolyphosphate as they will corrode metals. 

Concerns about the effect of TPP on eutrophication have led many states, cities, and regional governments to ban the use of the compound in syndets. Such bans have caused serious problems for detergent manufacturers, however, because no entirely satisfactory substitute for TPP has yet been found. Two promising candidates are the sodium salt of nitrilotriacetic acid, 3Na, N(CH2C02)3 , or NTA and ethylenediaminetetraacetic acid (EDTA). Both of these compounds act in much the same way as TPP, that is, by sequestering metal ions. Other builders that have been incorporated into syndet formulations include sodium carbonate, synthetic zeolites, borates, and organic polymers known as polycarboxylates. 

Nitrilotriacetic acid (NTA) [N(CH2COOH)3] is a complexant for many metal ions (see Sec. 2.9.1.2 for information on this compound). The sodium or potassium salts of NTA have been used to complex Cd for CD of CdSe from selenosulphate solutions [10,87]. The rate of film growth depends on many factors, as discussed in Chapter 3 experimental details for CdSe deposition from this solution are given in Chapter 2. However, growth times are generally longer than for... 

These molecules are flexible because rotation about single bonds is free, so they can wrap themselves around a metal ion to obtain four comfortable donor-atom-to-metal links within five-membered rings. Nitrilotriacetic acid is easily synthesized industrially from ammonia, formaldehyde, and hydrocyanic acid (the Strecker synthesis) and therefore is potentially an inexpensive but effective chelating agent. 

The most common and best known chelant is ethylenediaminetetraacetic acid (EDTA). The related compounds diethylenetriaminepentaacetic acid (DTPA) and nitrilotriacetic acid (NTA) are also well known (Figure 10.2). EDTA is a powerful chelant that complexes strongly with most metal ions to form six-coordinate complexes. It has therefore become the first choice in most applications. Indeed, a search of the bathroom cabinet will spot EDTA on the ingredient list of many personal care formulations. DTPA is also a powerful chelant, but tends to be used more often in industrial settings. NTA has only four binding sites and is used more often where hardness ions require control, such as in cleaning, for example, hard surface cleaners, dishwashing, and the dairy industry. 

As an alternative to acid washing, soils can also be flushed with chelating agents. Examples of effective chelating agents include ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), both of which readily bind and solubilize metals. Using this approach, Peters Shem (1992) have recently reported on the removal of lead from a contaminated soil. In this study, 0.1M EDTA removed 60% of the lead in a soil containing 10 000 mg lead/kg. 

Figure 12-4 Structures of analytically useful chelating agents. Nitrilotriacetic acid (NTA) tends to form 2 1 (ligand metal) complexes with metal ions, whereas the others form 1 1 complexes.

An alternative is to prepare a metal ion buffer from the metal and a suitable ligand. For example, consider the reaction of Ca2+ with nitrilotriacetic acid (NTA) at a pH high enough for NTA to be in its fully basic form (NTA3-) ... 

The formation of 1 1 complexes between ethylenediamine-N, N1 -diacetic acid (edda) and Zn11 or Cd11 have been studied by calorimetric (AH) and potentiometric techniques.389 Earlier studies had omitted to allow for protonation reactions of the ethanoato groups in the ligand. Thermodynamic parameters for edda lie between those of nitrilotriacetate and triethylenetetra-mine. Edda appears to undergo a slow metal-ion-catalyzed hydrolysis in aqueous acid solution. 

---