Using UV spectroscopy, we have studied the thermodynamics of extraction of metal picrates M+Pic−(M+= Li+, Na+K+, Rb+, Cs+Tl+and Ag+) and M2+(Pic−)2(M2+= Ca+, Sr+,Ba+, Pb+, and UO22+) from water to a chloroform or to a dichloromethane solution. The extractant molecules are mono-podands R-O-(CH2-O-CH2-)n-O-R containing an ether chain and terminal phosphoryl groups: R = (Ph)2P(O)-C6H4-; n = 3,4 (I - H) and R = (Ph)2P(O)-CH2-C6H4-, n = 1, 3, 4 (III - V). We found that podand displays a remarkable Ba2+/Ca2+extraction selectivity. All podands extract alkali and alkaline earth picrates in dichloromethane (as dissociated ion pairs) better than in chloroform (as non-dissociated ion pairs). Based on Molecular Dynamics simulations of the complexes IM2+and IM2+(Pic−)2in the gas phase and in chloroform we suggest that the high selectivity of I for Ba2+is due to (i) the formation of the complex with an “optimal” pseudocavity for Ba2+, in which six donor atoms of the ligand and four oxygens of the Pic−counter-ion coordinate to the cation. and, (ii) the smaller dehydration energy of Ba2+compared to other alkaline earth cations. The relative free energies of extraction obtained from simulations on the IM2+(Pic−)2complexes are in good agreement with the experimental data