モンテカルロ計算ソルバ 
クラウンエーテルの溶液中での構造
- The 13C-NMR study of the amine substituted 12-crown ?O3N and its Li+ and Na+ complexes. K.Hori H.Tsukube, J. Incl. Phen. Mol. Rec. Chem., 32, 311-329, 1998.
- The Li complex in the MeCN solution, the chemical shift of both ring and arm carbon changed depend on equivalent of molar ratio of crown ether and Li. On the other hand, the Na+ complex shows the change on chemical shift of ring carbon, but a little on the arm carbon.
- In the MeOH solution, the chemical shift of the ring carbon changed depending on the equivalent of molar ratio both of Li and Na complex.
Calculations of the difference in free energy of solvation
Potential Energies depending on the positionof the metal ion.
- For the energy profiles depending on the cation position, We calculate the energy of the each complex coordination.
- The each curves of this graph showed the 1 water coordinated Li-complex, the 2 waters and the 3or 4 waters. These curves indicated the change of the coordination number of solvents depending on the cation position from the center of the crown ring.
- The energy profiles are made of connecting the stable points on the graph. The energy profiles in the MeCN were calculated in the same way.
Energy profiles depending on the Li+ position in aqueous and MeCN solution.
It seems that the crown ether coordinate to Li+ in MeCN solution, and that the Li+ complex was dissociated into 1 and tetra solvated Li complex in aqueous solution.
Energy profiles depending on Na+ position in aqueous and MeCN solution.
Conclusion
- The procedure described in the present study estimates both the flexibility of a cyclic molecule and free energy differences among the conformers in the solutions. Iits showed good results which consistent with the solvent effects and the difference between the conplexes of Li+ and Na+.
- It was confirmed that the relative stability of conformers of the (12-crown-O3N)M+ complex in solutions are similar to that in vacuum in the case that the conformers have similar coordination environment, that is, the same coordination number in the complex. This is because “similar” conformers are similarly solvated; however, we cannot use energy differences in a vacuum as being equal to those in solutions when complexes have different coordination environments.
- As the FEP method cannot estimate such a large energy as the hydration energy of M+, we have to construct proper models, in which all the large stabilization energies are estimated within the quantum chemical motif. In the present case, four water molecules constructing the first solvation shell of M+ were included in the ab initio MO and DFT calculations.
- The present calculations showed how the coordination environment around alkali cation changes when it forms a complex with substituted 12-crown-O3N in the solutions.
