Anion−π Interactions: Generality, Binding Strength, and Structure

Anion−π interactions have been systematically studied using tetraoxacalix[2]­arene[2]­triazine 1, an electron-deficient and cavity self-tunable macrocyclic host, as an electron-neutral molecular probe. As revealed by electrospray ionization mass spectrometry (ESI-MS), fluorescence titration and X-ray crystallography, tetraoxacalix[2]­arene[2]­triazine has been found to form 1:1 complexes with four typical polyatomic anions of different geometries and shapes in the gaseous phase, in solution, and in the solid state. The association constants for the formation of anion−π complexes in acetonitrile are in the range of 239 to 16950 M–1, following the order of 1·NO3– > 1·BF4– > 1·PF6– > 1·SCN–. X-ray molecular structures of the complexes showed that two opposing triazine rings of tetraoxacalix[2]­arene[2]­triazine act as a pair of tweezers to interact with the included anions through cooperative anion−π and lone-pair electron−π interactions. The generality of anion−π interactions and diverse anion−π interaction motifs can provide a new dimension in the study of molecular recognition and self-assembly. Moreover, this study potentiates the effect of anion−π interactions in chemical and biological systems, especially those involving anion and electron-deficient aromatic species

A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative, and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011 to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state. The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular chemistry

A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative, and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011 to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state. The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular chemistry

A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative, and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011 to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state. The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular chemistry

A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative, and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011 to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state. The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular chemistry

Anion−π Interactions: Generality, Binding Strength, and Structure

Anion−π interactions have been systematically studied using tetraoxacalix[2]­arene[2]­triazine <b>1</b>, an electron-deficient and cavity self-tunable macrocyclic host, as an electron-neutral molecular probe. As revealed by electrospray ionization mass spectrometry (ESI-MS), fluorescence titration and X-ray crystallography, tetraoxacalix[2]­arene[2]­triazine has been found to form 1:1 complexes with four typical polyatomic anions of different geometries and shapes in the gaseous phase, in solution, and in the solid state. The association constants for the formation of anion−π complexes in acetonitrile are in the range of 239 to 16950 M^–1, following the order of <b>1</b>·NO₃^– > <b>1</b>·BF₄^– > <b>1</b>·PF₆^– > <b>1</b>·SCN^–. X-ray molecular structures of the complexes showed that two opposing triazine rings of tetraoxacalix[2]­arene[2]­triazine act as a pair of tweezers to interact with the included anions through cooperative anion−π and lone-pair electron−π interactions. The generality of anion−π interactions and diverse anion−π interaction motifs can provide a new dimension in the study of molecular recognition and self-assembly. Moreover, this study potentiates the effect of anion−π interactions in chemical and biological systems, especially those involving anion and electron-deficient aromatic species

Anion−π Interactions: Generality, Binding Strength, and Structure

Anion−π interactions have been systematically studied using tetraoxacalix[2]­arene[2]­triazine <b>1</b>, an electron-deficient and cavity self-tunable macrocyclic host, as an electron-neutral molecular probe. As revealed by electrospray ionization mass spectrometry (ESI-MS), fluorescence titration and X-ray crystallography, tetraoxacalix[2]­arene[2]­triazine has been found to form 1:1 complexes with four typical polyatomic anions of different geometries and shapes in the gaseous phase, in solution, and in the solid state. The association constants for the formation of anion−π complexes in acetonitrile are in the range of 239 to 16950 M^–1, following the order of <b>1</b>·NO₃^– > <b>1</b>·BF₄^– > <b>1</b>·PF₆^– > <b>1</b>·SCN^–. X-ray molecular structures of the complexes showed that two opposing triazine rings of tetraoxacalix[2]­arene[2]­triazine act as a pair of tweezers to interact with the included anions through cooperative anion−π and lone-pair electron−π interactions. The generality of anion−π interactions and diverse anion−π interaction motifs can provide a new dimension in the study of molecular recognition and self-assembly. Moreover, this study potentiates the effect of anion−π interactions in chemical and biological systems, especially those involving anion and electron-deficient aromatic species

A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative, and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011 to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state. The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular chemistry

Synthesis and Structure of Functionalized Homo Heteracalix[2]arene[2]triazines: Effect of All Heteroatom Bridges on Macrocyclic Conformation

A number of unprecedented homo heteracalix[2]­arene[2]­triazines were synthesized by means of a fragment coupling approach. Two directional nucleophilic substitution reactions of <i>N</i>-Boc-protected 1,3-dihydrazobenzene with cyanuric acid chloride and 2-butoxy-4,6-dichloro-1,3,5-triazine led to hydrazo-linked trimers, which underwent an efficient macrocyclic condensation reaction with functionalized resorcinol derivatives to afford (NHNBoc)₂,O₂-calix­[2]­arene­[2]­triazine macrocycles, which contain a functional group either on the upper rim or the lower rim. The use of 1,3-phenylenediamines instead of resorcinol in the reaction produced (NR)₂,(NHNBoc)₂-calix­[2]­arene­[2]­triazines. Postmacrocyclization modifications such as a nucleophilic substitution reaction of chloro on triazine by amines and the removal of Boc from hydrazo moieties produced homo calix[2]­arene[2]­triazine derivatives. In the solid state, (NHNR)₂,O₂-bridged calix[2]­arene[2]­triazines with and without a substituent on the upper rim position and (NMe)₂,(NHNBoc)₂-calix­[2]­arene­[2]­triazine adopted a typical partial cone conformation while the heavily twisted 1,3-alternate conformational structures were observed for both (NHNBoc)₂,O₂-calix­[2]­arene­[2]­triazines bearing a functional group on the lower rim position and (NH)₂,(NHNBoc)₂-calix­[2]­arene­[2]­triazine. In solution, all synthesized homo heteracalix[2]­arene[2]­triazines existed as the mixture of different macrocyclic conformers, which underwent slow interconversions at room temperature relative to the NMR time scale

Anion−π Interactions: Generality, Binding Strength, and Structure

Anion−π interactions have been systematically studied using tetraoxacalix[2]­arene[2]­triazine <b>1</b>, an electron-deficient and cavity self-tunable macrocyclic host, as an electron-neutral molecular probe. As revealed by electrospray ionization mass spectrometry (ESI-MS), fluorescence titration and X-ray crystallography, tetraoxacalix[2]­arene[2]­triazine has been found to form 1:1 complexes with four typical polyatomic anions of different geometries and shapes in the gaseous phase, in solution, and in the solid state. The association constants for the formation of anion−π complexes in acetonitrile are in the range of 239 to 16950 M^–1, following the order of <b>1</b>·NO₃^– > <b>1</b>·BF₄^– > <b>1</b>·PF₆^– > <b>1</b>·SCN^–. X-ray molecular structures of the complexes showed that two opposing triazine rings of tetraoxacalix[2]­arene[2]­triazine act as a pair of tweezers to interact with the included anions through cooperative anion−π and lone-pair electron−π interactions. The generality of anion−π interactions and diverse anion−π interaction motifs can provide a new dimension in the study of molecular recognition and self-assembly. Moreover, this study potentiates the effect of anion−π interactions in chemical and biological systems, especially those involving anion and electron-deficient aromatic species