CHAPTER 9 . Binding Ability of Inorganic Major Components of Sea Water
231
For example:
btc 4 - + Bl.l17+ = B(btc)2.883n = 4
H 3 (mlt)3- + B1.l17+ = BH 3 (mlt)1.883- n = 3
The simplest relationship between 10gK and n is:
10gK = 0.37 (±om) n 312 (1 ~ n ~ 5)
(9.6)
Inspection of stability data revealed some other interesting trends: (i) stability is
inversely proportional to the length of the alkyl chain. If we consider malonate, succinate and azelate we have /3110 = 48, 18 and 9 M- 1 , respectively: the decreasing function
is not linear, owing to the higher flexibility of longer chains; (ii) the higher stability of
oxydiacetate and trioxydiacetate is due to the involvement of the ethereal group in the
co-ordination. This is consistent with previous findings on the stability of calcium
complexes of oxydiacetate and trioxydiacetate (De Stefano et al. 1999d, 2000C).
Figure 9.4 shows the speciation diagram vs. pH for the tca system in artificial sea
water (BA) at S = 35. In this system, it can be observed that all the species show high
yields (>20%) and that at pH > 7, the sum of B(tca) 1.883- plus B 2 (tca)O.766- is >90%.
The same holds for the btc-BA system with a higher yield (except for the tri-protonated complex), and at pH> 7 we have -100% of the ligand as B(btc)2.883- and
B 2 (btc) 1.766-. Formation percentages are strongly dependent on the number of carboxylic groups in the ligand; to illustrate this trend quantitatively, in Fig. 9.5 we plotted
~(species) % vs. salinity, at pH 8.2 for mono-, di-, tri- and tetra-carboxylic ligands.
Percentages increase with n: for mellitate, at pH > 5, a 100% yield is always observed.
9.3.1.2
Phenols
A study carried out on the interaction of phenol and some of its derivatives in artificial sea water (Demianov et al. 1995) shows that phenols in artificial sea water form
the weak species BLo. ll7 + (Table 9.8), with a mean stability of 1.3 M- 1 . This stability is
somewhat lower than that of mono-carboxylic ligands, but is still comparable (same
order of magnitude).
9.3.1.3
Amines
Amines are quite an important class of ligands, present as trace components in all biological fluids and natural waters. In particular, open chain polyamines have been widely
studied owing to their strong ability to bind several metal cations (Perrin 1979; Pettit
and Powell 1997; Martell and Smith 1997) and to form fairly stable species, in their
protonated form, with organic and inorganic polyanions (Daniele et al. 1997). Amino
compounds play an important role in reactions with sugars (or their derivatives) in
natural waters leading to polymerized products (Bremmer 1967; Stevenson and Butler 1969) containing several amino groups along a linear chain, whose composition is
231
For example:
btc 4 - + Bl.l17+ = B(btc)2.883n = 4
H 3 (mlt)3- + B1.l17+ = BH 3 (mlt)1.883- n = 3
The simplest relationship between 10gK and n is:
10gK = 0.37 (±om) n 312 (1 ~ n ~ 5)
(9.6)
Inspection of stability data revealed some other interesting trends: (i) stability is
inversely proportional to the length of the alkyl chain. If we consider malonate, succinate and azelate we have /3110 = 48, 18 and 9 M- 1 , respectively: the decreasing function
is not linear, owing to the higher flexibility of longer chains; (ii) the higher stability of
oxydiacetate and trioxydiacetate is due to the involvement of the ethereal group in the
co-ordination. This is consistent with previous findings on the stability of calcium
complexes of oxydiacetate and trioxydiacetate (De Stefano et al. 1999d, 2000C).
Figure 9.4 shows the speciation diagram vs. pH for the tca system in artificial sea
water (BA) at S = 35. In this system, it can be observed that all the species show high
yields (>20%) and that at pH > 7, the sum of B(tca) 1.883- plus B 2 (tca)O.766- is >90%.
The same holds for the btc-BA system with a higher yield (except for the tri-protonated complex), and at pH> 7 we have -100% of the ligand as B(btc)2.883- and
B 2 (btc) 1.766-. Formation percentages are strongly dependent on the number of carboxylic groups in the ligand; to illustrate this trend quantitatively, in Fig. 9.5 we plotted
~(species) % vs. salinity, at pH 8.2 for mono-, di-, tri- and tetra-carboxylic ligands.
Percentages increase with n: for mellitate, at pH > 5, a 100% yield is always observed.
9.3.1.2
Phenols
A study carried out on the interaction of phenol and some of its derivatives in artificial sea water (Demianov et al. 1995) shows that phenols in artificial sea water form
the weak species BLo. ll7 + (Table 9.8), with a mean stability of 1.3 M- 1 . This stability is
somewhat lower than that of mono-carboxylic ligands, but is still comparable (same
order of magnitude).
9.3.1.3
Amines
Amines are quite an important class of ligands, present as trace components in all biological fluids and natural waters. In particular, open chain polyamines have been widely
studied owing to their strong ability to bind several metal cations (Perrin 1979; Pettit
and Powell 1997; Martell and Smith 1997) and to form fairly stable species, in their
protonated form, with organic and inorganic polyanions (Daniele et al. 1997). Amino
compounds play an important role in reactions with sugars (or their derivatives) in
natural waters leading to polymerized products (Bremmer 1967; Stevenson and Butler 1969) containing several amino groups along a linear chain, whose composition is