Free energy of complexation

Duan, W. Wang, O. Donini, P. Cieplak, J. Srinivasan, D. A. Case, and T. E. Cheatham, HI, Calculating structures and free energies of complex molecules Combining molecular mechanics and continuum models, Acc. Chem. Res. 33 889 (2000). 

The relative magnitude of the two concentrations evidently depends on the magnitude of the equilibrium constants and of the concentrations of M and X. Two further points need to be made, (i) It is likely that the formation of 3 from 2 will be favoured, i.e., the equilibrium constant will be enhanced, by a statistical factor akin to an entropy of mixing, (ii) For the species 2 there is no front and back , the MP+BM is symmetrical, and therefore the probability of the propagation, i.e., the, is twice as great as it would be for XP+BM, even if the free energy of complexing is the same for X and M. 

Correlation of structures of diastereomeric complexes with estimated enthalpic and entropic contributions to free energy of complexation (0°C) ... 

Table 2 Binding constants (Xa, L mol ) and free energies of complexation (-AG°, kj mol ) for complexes of 12b with alkali metal cations ...

Figure 16 Correlation between gas phase basicity PA and free energy of complexation with phenol AGH for substituted pyridines (Reproduced with permission from <78JPCI268 ...

Table 6. Association constants and free energies of complexation for complexes of 16 with dihydroxybenzene derivatives in CDCI3 at 298 2K...

Table t. Dependence of the dissociation constant of interpolymer complexes K and of free energy of complex formation AFb on the ratio y between the number of oxyelglene units of PEG in the network and the number of MAA units of PMAA... 

Table 3.19 Free energy of complexation, (— AG° / kcal mol-1) of neutral and cationic guests (iodide salts) by chiral receptor 3.108 (20 °C, borate buffer, pD = 9, CDC13 solution).50...

The lack of correlation with enthalpic (i.e. bond length-related) data highlights the complexity of the system, and the need to consider solvation/desolvation-related effects as contributing significantly to the free energies of complexation. 

Remarkably, enhanced binding by the chelate effect is occasionally seen not in free energies of complexation the association constants of e.g. amino acids with sulfonatocalix[4]arenes are quite close the ones observed with phenol-4-sulfonic acid as single host unit Only AH shows an advantage of the macrocycle with AH = 30 compared to 1 kJ/mol, compensated by a much smaller entropy disadvantage with the smaller monomeric host, which changes from e.g. TAS = -12 kJ/mol to favorable +12 kJ/mol.[34]... 

Kollman PA, Massova I, Reyes C, Kuhn B, Huo S, Chong L, Lee M, Lee T, Duan Y, Wang W, Donini O, Cieplak P, Srinivasan J, Case DA, Cheatham III TE(2000) Calculating structures and free energies of complex molecules combining molecular mechanics and continuum models, Acc Chem Res, 33 889-897... 

Figure 10.3. The [2]pseudorotaxanes [1 2] 4PF6-[1 6] 4PF6 and their association constants (KJ and free energies of complexation (-AG0) in MeCN at 25 °C.

The component analysis described above shows that the aromatic cleft in 34 contributes 4.2 kcal mol-1 toward the free energy of complexation of 9-propyladenine (50). An alternative approach to determining the contribution made by the aromatic cleft would be to measure the free energy obtained in a complex between 50 and a molecular tweezer containing an aromatic cleft, but no carboxylic acid group. This analysis, which has been carried out using molecular tweezer 11,... 

It has been shown lately that the free energy of complex formation in a series of metal atoms varies linearly with the total ionization energy (M -> M2+ + 2e) of the central atom. H. Irving and R. J. P. Williams, Nature, 162 (1948) 746 L. H. Ahrens, Nature, 169 (1952) 463 W. S. Fyfe, J. Chem. Soc., 1952, 2018. 

In such a case AGioi — AGr. This means that the free energy of complex formation is reflective of lanthanide-ligand interaction. Thus the value of AHioi and ASioi can be interpreted to a first approximation in terms of hydrational changes [29]. 

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