Calix[2]thia[4]phyrin: An Expanded Calixphyrin with Aggregation-Induced Enhanced Emission and Anion Receptor Properties

Abstract

The synthesis of calix[2]thia[4]phyrin 3, a core-modified expanded calixphyrin, by an efficient synthetic route is reported. 3 exhibits an aggregation-induced enhanced emission (AIEE) phenomenon upon addition of increasing amounts of water. This is attributed to the restricted intramolecular rotation of the meso-aryl rings present on the sp(3) bridging carbons. SEM studies revealed the formation of aggregation in an acetonitrile/water mixture with an average diameter of the aggregate in the range 0.38-2.08 μm. The photoluminescence quantum yield of 3 in 9:1 water/acetonitrile is 5-fold higher than the quantum yield in acetonitrile alone. Single-crystal X-ray analysis of 3 revealed a chairlike conformation stabilized by N-H···N and C-H···π intramolecular hydrogen-bonding interactions. Fluorine atoms on the meso-pentafluorophenyl groups are involved in C-H···F intermolecular hydrogen-bonding interactions to generate a two-dimensional supramolecular assembly in the solid state. In the diprotonated state, 3 has affinity for anions and forms 1:1 complexes with SO4(2-), NO3(-), Cl(-), and ClO4(-) in solution. The tetrahedral anions bind more strongly than the other anions. Single-crystal X-ray structure studies of the ClO4(-) anion complex with 3 revealed the formation of both 1:1 and 1:2 complexes in the solid state, with the host and the guest being held together by N-H···O hydrogen-bonding interactions.

Organic Fluorine as a Hydrogen-Bond Acceptor: Recent Examples and Applications

“…32 Another example of the ability for hydrogen bonds to direct crystal structures was found by Chandrashekar and co-workers. 33 The authors observed by X-ray crystallography the formation of a supramolecular assembly of calixphyrins held by intermolecular C-H Nath and Baruah studied the crystal structures of two fluorine-substituted bis-phenols. 34 Depending on the solvent used for the crystallization of bis-phenol 13 ( Figure 12), one of two polymorphs can be obtained.…”

Stable core-modified calixsmaragdyrins: synthesis, structure and specific sensing of the hydrogen sulfate ion

“…However, the anion sensing properties of these macrocycles have not been studied. 8 A perusal of the literature revealed that the reports on core-modified expanded calixphyrins 9 are very scarce to understand their complete potential for anion sensing applications. In 1999, Chandrashekar and coworkers 10 reported first stable core-modified meso-aryl smaragdyrins such as 5,10,19-triphenyl-25-oxasmaragdyrin 1a and 5,10,19-triphenyl-25-thiasmaragdyrin 1b (Scheme 1) which contain four pyrrole rings and one furan/thiophene ring that are connected via three methine bridges and two direct bonds.…”

Synthesis and specific fluoride binding properties of expanded dithiacalixphyrins

“…The macrocycles 3a-c were prepared by condensing one equivalent of 4 with one equivalent of appropriate dipyrromethane 5 in CH 2 Cl 2 in the presence of 0.1 equivalent of TFA under a N 2 atmosphere at room temperature for 1 h followed by oxidation with DDQ in air for additional 1 h. TLC analysis showed mainly one major red spot and absorption spectroscopy showed one broad band at ∼450 nm indicating the formation of a macrocycle. 7,[13][14][15][23][24][25][26][27][28] The crude compound was subjected to alumina column chromatography and afforded the macrocycles 3a-c as orange red solids in 16-19% yields. Although we expected the formation of an expanded macrocycle containing one meso-sp 3 carbon such as compound 6 (Scheme 1), the X-ray structure of one of the macrocycles and detailed NMR studies indicated the formation of an expanded dithiacalixphyrin having two meso sp 3 carbons such as macrocycles 3a-c.…”