An insight into the disorder properties of the α-cyclodextrin polyiodide inclusion complex with Sr2+ ion: Dielectric, DSC and FT-Raman spectroscopy studies

Vasileios G. Charalampopoulos (1) , John Christofer Papaioannou (2) , Kyriakos Viras (1) , Haido Stefania Karagianni (3) , Glikeria Kakali (3)

1 NKUA - National and Kapodistrian University of Athens
2 Chemistry
3 NTUA - National Technical University of Athens [Athens]

At T < 250 K, the polyiodide inclusion complex (α-cyclodextrin)2∙Sr0.5∙I5∙17H2O displays two separate relaxation processes due to both the frozen-in proton motions in an otherwise ordered H-bonding network and the order-disorder transition of some normal H-bonds to flip-flop ones. At T > 250 K, the ac-conductivity is dominated by the combinational contributions of the disordered water network, the mobile Sr2+ ions, the polyiodide charge-transfer interactions and the dehydration process. The evolution of the Raman spectroscopic data with temperature reveals the coexistence of four discrete pentaiodide forms. In form (I) (I-3∙I2↔I2∙I-3), the occupancy ratio (x/y) of the central I- ion differs from 50/50. In form (IIa) (I2∙I-∙I2) x/y = 50/50, whereas in its equivalent form (IIb) (I2∙I-∙I2)* as well as in form (III) (I-3∙I2), x/y = 100/0 (indicative of full occupancy). Via slow cooling and heating the inverse transformations (I) ® (IIa) and (IIa) ® (I) occur, respectively.

Mots clés: Physical Sciences

Vasileios G. Charalampopoulos, John Christofer Papaioannou, Kyriakos Viras, Haido Stefania Karagianni, Glikeria Kakali. An insight into the disorder properties of the α-cyclodextrin polyiodide inclusion complex with Sr2+ ion: Dielectric, DSC and FT-Raman spectroscopy studies. Supramolecular Chemistry, 2010, 22 (9), pp.499. ⟨10.1080/10610278.2010.487563⟩. ⟨hal-00599229⟩