Table 2. Thermodynamic Data (kJ mol–1) for Protonation of L2, L2-Me, L2-Me3, L1,30L1-Me,30 and L1-Me3,30 Determined in 0.15 M NaClO4 at 298.1 ± 0.1 K.
|
L2 |
L2-Me |
L2-Me3 |
||||
|---|---|---|---|---|---|---|
| reactiona | ΔH° | TΔS° | ΔH° | TΔS° | ΔH° | TΔS° |
| H–1L– + H+ ⇄ H(H–1L) | –40.2(7)b | 21.9(7) | –39.9(4) | 25.8(4) | –38.8(3) | 23.6(3) |
| H(H–1L) + H+ ⇄ H2(H–1L)+ | –41.0(8) | 9.5(8) | –41.3(4) | 9.2(4) | –39.0(3) | 7.5(3) |
| H2(H–1L)+ + H+ ⇄ H2L2+ | –22.1(5) | 9.2(5) | –24.7(5) | 7.9(5) | –10.3(4) | 16.8(4) |
| H2L2+ + H+ ⇄ H3L3+ | –4.0(2) | 9.0(3) | –2.1(5) | 10.6(5) | – | – |
|
L1 |
L1-Me |
L1-Me3 |
||||
|---|---|---|---|---|---|---|
| ΔH° | TΔS° | ΔH° | TΔS° | ΔH° | TΔS° | |
| L + H+ ⇄ HL+ | –42.6(2) | 17.6(2) | –39.5(5) | 19.6(5) | –31.3(5) | 30.8(5) |
| HL+ + H+ ⇄ H2L2+ | –44.6(3) | 0.8(3) | –48.3(7) | –2.1(7) | –39.2(6) | –2.9(6) |
| H2L2+ + H+ ⇄ H3L3+ | –3.1(4) | 7.7(4) | 0.5(9) | 13.4(9) | – | – |
a
H–1L corresponds to the ligands with deprotonated pyridinol moiety.
b
Values in parentheses are standard deviations in the last significant figure.