197234-44-9Relevant academic research and scientific papers
Calixarene Metalloreceptors. Synthesis and Molecular Recognition Properties of Upper-Rim Functionalized Calix[4]arenes Containing an Organopalladium Binding Site
Cameron, Beth R.,Loeb, Stephen J.,Yap, Glenn P. A.
, p. 5498 - 5504 (1997)
The compound 5,17-bis(2-chloroacetamido)-25,26,27,28-tetrapropoxycalix[4]arene, 4, was prepared in the cone conformation by the published method. Compound 4 was reacted with α,α'-m-xylenedithiol and sodium ethoxide under high-dilution conditions in ethanol solution. The resulting macrobicyclic calix[4]arene, HL1, 5, contains a symmetrically disposed macrocyclic loop across the upper rim of the calix[4]arene. Palladation of 5 yielded [Pd(L1)(CH3CN)][BF4], 6. Similarly 5,17-bis[2-(4-(chloromethyl)phenoxy)acetamido]-25,26,27,28-tetrapropoxycalix[4] arene, 8, was used to prepare HL2, 9. Compound 9 is similar to 5 but contains an aromatic spacer group separating the xylyl fragment from the calixarene unit. Palladation of 9 yielded [Pd(L2)(CH3CN)][BF4], 11. All new compounds and complexes were characterized in solution by 1H NMR spectroscopy, and the molecular structure of 5 was verified by a single-crystal X-ray diffraction study. Compound 5 crystallized in the space group P21/c with a = 23.5095(1) A?, b = 9.9090(1) A?, c = 23.3586(1) A?, β= 91.53(1)°, V = 5439.59(8) A?3, and Z = 4. The structure was refined to R(F) = 10.13% and RW(F2) = 21.91% for 5799 reflections with F02 > 2α(F02). Compounds 6 and 11 are calix[4]arene-based metalloreceptors containing an organopalladium binding site and a hydrophobic cavity provided by the calix[4]arene. Binding of a substrate through α-bonding to the palladium center and interaction within the hydrophobic site were demonstrated in solution by 1H NMR spectroscopy. These multiple receptor-substrate interactions are used by 11 for the molecular recognition of 4-phenylpyridine in the presence of 2-phenylpyridine or 3-phenylpyridine.
