A. Varnek et al., Switching Ca2+/Ba2+ to Ba2+/Ca2+ potentiometric selectivities of podands with phosphoryl-containing terminal groups: A molecular modelling study, J INCL P MA, 37(1-4), 2000, pp. 407-421
Citations number
42
Categorie Soggetti
Chemistry
Journal title
JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY
It has been shown experimentally that the Ca2+/Ba2+ potentiometric selectiv
ity of phosphoryl-containing podand R-O-(CH2-CH2-O)(n)-R, R = -C6H4-P(O)Ph-
2, n = 3 (I), switches to Ba2+/Ca2+ when the ligand contains the longer pol
yether chain, n = 5 (II). Here, we report molecular dynamics and free energ
y perturbation simulations performed using the amber 4.1 program on the com
plexes (LM2+)-M-. (M2+ = Ca2+, Sr2+ and Ba2+, L = I and II) in the gas phas
e in order to gain a microscopic insight into structural and energy binding
properties of podands as a function of n. Mixed QM/MM (PM3/AMBER) calculat
ions were performed to analyse the role of polarisation effects on the comp
lexation selectivity of podands. It is shown that an increase of n does not
affect the interactions of M2+ with phosphine oxide groups, but leads to l
ess efficient interactions of small cations with the polyether chain. Calcu
lated potentiometric selectivities of I (Ca2+ > Ba2+) and II (Ba2+ > Ca2+)
are in agreement with the experimental data.