The Synthesis, Structures and Chemical Properties of Macrocyclic Ligands Covalently Bonded into Layered Arrays
- Texas A&M University, College Station, TX
OAK-B135 The immobilization of crown ethers tends to limit the leveling effect of solvents making the macrocycles more selective. In addition immobilization has the added advantage of relative ease of recovery of the otherwise soluble crown. We have affixed CH2PO3H2 groups to azacrown ethers. The resultant phosphorylated macrocycles may spontaneously aggregate into crystalline supramolecular linear arrays or contacted with cations produce layered or linear polymers. In the linear polymers the metal and phosphonic acids covalently bond into a central stem with the macrocyclic rings protruding from the stem as leaves on a twig. Two types of layered compounds were obtained with group 4 metals. Monoaza-crown ethers form a bilayer where the M4+ plus phosphonic acid groups build the layer and the rings fill the interlayer space. 1, 10-diazadiphosphonic acids cross-link the metal phosphonate layers forming a three-dimensional array of crown ethers. In order to improve diffusion into these 3-D arrays they are spaced by inclusion of phosphate or phosphate groups. Two series of azamacrocylic crown ethers were prepared containing rings with 20 to 32 atoms. These larger rings can complex two cations per ring. Methylene phosphonic acid groups have been bonded to the aza ring atoms to increase the complexing ability of these ligands. Our approach is to carry out acid-base titrations in the absence and presence of cations to determine the pKa values of the protons, both those bonded to aza groups and those associated with the phosphonic acid groups. From the differences in the titration curves obtained with and without the cations present we obtain the stoichiometry of complex formation and the complex stability constants. Some of the applications we are targeting include phase transfer catalysis, separation of cations and the separation of radioisotopes for diagnostic and cancer therapeutic purposes.
- Research Organization:
- Texas A&M University, College Station, TX
- Sponsoring Organization:
- USDOE Office of Science and Technology (OST) (EM-50)
- DOE Contract Number:
- FG03-00ER15086
- OSTI ID:
- 816105
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ATOMS
CATALYSIS
CATIONS
CHEMICAL PROPERTIES
CROWN ETHERS
DIFFUSION
ETHERS
NEOPLASMS
PHOSPHATES
PHOSPHONATES
PHOSPHONIC ACIDS
POLYMERS
PROTONS
RADIOISOTOPES
SOLVENTS
STABILITY
STOICHIOMETRY
SYNTHESIS
TITRATION