Abstract
Two synthetic protocols for the introduction of fluorine atoms into resorcinarene-based cavitands, at the lower and upper rim, respectively, are reported. Cavitand 1, bearing four fluorocarbon tails, and cavitand 2, which presents a fluorine atom on the para position of a diester phosphonate phenyl substituent, were synthesized and their complexation abilities toward the model guest sarcosine methyl ester hydrochloride were evaluated via NMR titration experiments. The effect of complexation on the 19F NMR resonance of the probe is evident only in the case of cavitand 2, where the inset of the cation-dipole and H-bonding interactions between the P=O bridges and the guest is reflected in a sizable downfield shift of the fluorine probe.
Highlights
IntroductionCavitands [1] are programmable abiotic receptors capable of hosting shape-complementary guests through specific weak interactions, such as hydrogen bonding, π-π stacking, CH-π and cation-π interactions.Their remarkable and versatile molecular recognition properties have been exploited in many different fields, including catalysis [2,3,4,5], crystal engineering [6], molecular grippers [7], protein recognition [8,9], responsive nanostructures [10,11], self-diagnostic polymers [12] and sensing [13,14].Expanding further the application fields of cavitands requires the exploration of new synthetic pathways for the introduction of specific reporting units
Fluorocarbon-footed tetraphosphonate cavitand 1 was prepared from resorcinarene 4, bearing
The present study describes two possible synthetic ways to introduce fluorine probes in tetraphosphonate cavitands, at the lower and upper rim, respectively
Summary
Cavitands [1] are programmable abiotic receptors capable of hosting shape-complementary guests through specific weak interactions, such as hydrogen bonding, π-π stacking, CH-π and cation-π interactions.Their remarkable and versatile molecular recognition properties have been exploited in many different fields, including catalysis [2,3,4,5], crystal engineering [6], molecular grippers [7], protein recognition [8,9], responsive nanostructures [10,11], self-diagnostic polymers [12] and sensing [13,14].Expanding further the application fields of cavitands requires the exploration of new synthetic pathways for the introduction of specific reporting units. Cavitands [1] are programmable abiotic receptors capable of hosting shape-complementary guests through specific weak interactions, such as hydrogen bonding, π-π stacking, CH-π and cation-π interactions Their remarkable and versatile molecular recognition properties have been exploited in many different fields, including catalysis [2,3,4,5], crystal engineering [6], molecular grippers [7], protein recognition [8,9], responsive nanostructures [10,11], self-diagnostic polymers [12] and sensing [13,14]. The discrimination between different analytes was possible only when the interactions with the tungsten were strong enough to produce static structures on the NMR time scale and peaks at precise chemical shifts
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