Thermodynamics of macrocycle complexation chemistry. Interactions of metal ions with double-armed N-pivot lariat ethers in methanol and methanol-water solutions at 25.0{degrees}C

Journal Article · Wed Mar 16 04:00:00 EST 1994 · Inorganic Chemistry

DOI:https://doi.org/10.1021/ic00084a006· OSTI ID:47947

Izatt, R M; Zhang, X; An, H; Zhu, C Y; Bradshaw, J S ^[1]

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1. Brigham Young Univ., Provo, UT (United States)

The log K, {Delta}H, and T{Delta}S values for interactions of Na{sup +}, K{sup +}, Cu{sup 2+}, and Ca{sup 2+} with a series of N,N`-dipivot lariat ethers have been determined from calorimetric titration data valid in 9:1 (v/v) CH{sub 3}OH/H{sub 2}O and absolute methanol at 25.0{degrees}C. Complex stability is increased greatly by introducing pendant arms containing oxygen or nitrogen atoms to the parent macrocycles. The enthalpy and entropy changes support the idea that the side arms interact with the cations. Formation of complexes of Ca{sup 2+} is both enthalpy and entropy stabilized. All other interactions are enthalpy driven, and the entrophy changes are unfavorable. Effects of pendant-arm length and substituents on the complexation of the cations are discussed on the basis of thermodynamic data. The large negative {Delta}H values for complexation of Cu{sup 2+} with lariat ethers indicate a strong interaction between Cu{sup 2+} and the nitrogen atoms of the ligands. Large entropic losses for some of the cation-ligand interactions indicate that the lariat ethers are flexible and readily change their conformations to accommodate the cations.

• Sponsoring Organization: USDOE
• DOE Contract Number: FG02-86ER13463
• OSTI ID: 47947
• Journal Information: Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 6 Vol. 33; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CALCIUM
CALORIMETRY
COPPER
ETHERS
POTASSIUM
SODIUM
THERMODYNAMIC PROPERTIES
TITRATION