Microcalorimetric determination of thermodynamic parameters for ionophore-siderophore host-guest complex formation

被引:13
作者
Trzaska, SM [1 ]
Toone, EJ [1 ]
Crumbliss, AL [1 ]
机构
[1] Duke Univ, Dept Chem, Durham, NC 27708 USA
关键词
D O I
10.1021/ic9908571
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Thermodynamic parameters (Delta H, Delta S, and Delta G) were determined by microcalorimetry in wet chloroform for host-guest assembly formation involving second-sphere complexation of the siderophore ferrioxamine B by crown ether (18-crown-6, cis-dicyclohexano-18-crown-6, benzo-18-crown-6) and cryptand (2.2.2 cryptand) hosts. Similar data were also collected for the same hosts with the pentylammonium ion guest, which corresponds to the pendant pentylamine side chain of ferrioxamine B. Host-guest assembly formation constants (K-a) obtained from microcalorimetry agree with values obtained indirectly from chloroform/water extraction studies in those cases where comparable data are available. On the basis of a trend established by the pentylammonium guest, an enhanced stability relative to the crown ethers is observed for the assembly composed of ferrioxamine B and 2.2.2 cryptand that is due to entropic effects. Trends in Delta H and Delta S with changes in host and guest structure are discussed and attributed directly to host-guest complex formation, as solvation effects were determined to be insignificant (Delta C-p = 0).
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页码:1071 / 1075
页数:5
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