Characterization of Rose Bengal-N,N{sup {prime}}-dimethyl-4,4{sup {prime}}-bipyridinium complexes and their separation in aqueous SiO{sub 2} colloids: Photophysical properties of Rose Bengal in the microheterogeneous system
- Hebrew Univ. of Jerusalem (Israel)
- National Renewable Energy Laboratory, Golden, CO (United States)
Rose Bengal, Rb{sup 2{minus}}, forms crystalline 1:1 and 2:1:1 complexes with N, N{sup {prime}}-dimethyl-4,4{sup {prime}}-bipyridinium, MV{sup 2+}. In the 1:1 complex the two components are coplanar with charge neutralization within the complex structure. In the 2:1:1 complex, one MV{sup 2+} unit is intercalated between two Rb{sup 2-} units and the second MV{sup 2+} unit is positioned externally to this sandwich structure and acts in charge neutralization. In both complexes, electrostatic interactions, charge-transfer interactions, and {pi}-interactions stabilize the intermolecular assemblies. In solution, Rb{sup 2-} and MV{sup 2+} form initially the 1:1 intermolecular complex [Rb{sup 2-}...MV{sup 2+}]; K{sub a(298K)} = 9000 {plus_minus} 500, {Delta}H{degrees} = 36.62 {plus_minus} 2 KJ{center_dot}mol{sup {minus}1}, and {Delta}S = -0.048 {plus_minus}0.0025 KJ{center_dot}mol{sup {minus}1}{center_dot}K{sup {minus}1}. In the presence of added silica colloid, the [Rb{sup 2{minus}}...MV{sup 2+}] complex is separated through the selective association of MV{sup 2+} to the negatively charged colloid interface; K{sub a(298K)} = 140000 {plus_minus} 20000 m{sup {minus}1}. Flash photolysis experiments reveal that only free MV{sup 2+} is operative in the quenching of {sup 3}Rb{sup 2{minus}}; k{sub q}=4.7 {plus_minus} 1 x 10{sup 9} M {sup {minus}1}{center_dot}s{sup {minus}1}. 11 refs., 6 figs., 4 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 273614
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 14 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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