New Multicomponent Porous Architecture of Self-Assembled Porphyrins/Calixarenes Driven by Nickel Ions

A new multicomponent material with nanoporous structure has been synthesized by co-crystallization of a mixture of cationic <i>meso</i>-tetrakis­(4-<i>N</i>-methylpyridyl)­porphyrin (H₂T₄) and <i>meso</i>-tri­(4-<i>N</i>-methylpyridyl)­porphyrin (H₂T₃py) with polyanionic 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis­(hydroxylcarbonylmethoxy)­calix[4]­arene (C₄TsTc) in the presence of Ni²⁺ ions. The structural analysis indicates that the overall architecture is assembled by interpenetrated two-dimensional (2D) meshes where the nodes are built up by a central tetracationic H₂T₄ porphyrin with arms hosted in sulphonated rims of four cavitands. The approximately 2D square network is formed by Ni²⁺ ions bridging the calixarene carboxylate rims in a tail-to-tail fashion. The central H₂T₄ stacks with two external H₂T₃py molecules having the neutral pyridine arm <i>N</i>-coordinated to Ni²⁺ ions. These metal centers interconnect the orthogonal 2D meshes by further coordination of calixarene–carboxylate groups. Self-organization of the new multicomponent material, featuring large channels (60% of volume accessible to solvent molecules) and potential readily accessible metal active sites, has been driven by both supramolecular host–guest recognition and coordinative assembly. The thermal behavior of native and nickel-containing crystals was studied by hot stage microscopy and differential scanning calorimetry. The decomposition temperatures of the multicomponent materials, 465–470 °C, are about 100 °C higher than those of the single building blocks

New Multicomponent Porous Architecture of Self-Assembled Porphyrins/Calixarenes Driven by Nickel Ions

A new multicomponent material with nanoporous structure has been synthesized by co-crystallization of a mixture of cationic <i>meso</i>-tetrakis­(4-<i>N</i>-methylpyridyl)­porphyrin (H₂T₄) and <i>meso</i>-tri­(4-<i>N</i>-methylpyridyl)­porphyrin (H₂T₃py) with polyanionic 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis­(hydroxylcarbonylmethoxy)­calix[4]­arene (C₄TsTc) in the presence of Ni²⁺ ions. The structural analysis indicates that the overall architecture is assembled by interpenetrated two-dimensional (2D) meshes where the nodes are built up by a central tetracationic H₂T₄ porphyrin with arms hosted in sulphonated rims of four cavitands. The approximately 2D square network is formed by Ni²⁺ ions bridging the calixarene carboxylate rims in a tail-to-tail fashion. The central H₂T₄ stacks with two external H₂T₃py molecules having the neutral pyridine arm <i>N</i>-coordinated to Ni²⁺ ions. These metal centers interconnect the orthogonal 2D meshes by further coordination of calixarene–carboxylate groups. Self-organization of the new multicomponent material, featuring large channels (60% of volume accessible to solvent molecules) and potential readily accessible metal active sites, has been driven by both supramolecular host–guest recognition and coordinative assembly. The thermal behavior of native and nickel-containing crystals was studied by hot stage microscopy and differential scanning calorimetry. The decomposition temperatures of the multicomponent materials, 465–470 °C, are about 100 °C higher than those of the single building blocks

Selective Binding of Spherical and Linear Anions by Tetraphenyl(thio)urea-Based Dihomooxacalix[4]arene Receptors

Three novel tetra­(thio)­ureido dihomo­oxa­calix­[4]­arene anion receptors (phenylurea <b>4a</b>, phenylthiourea <b>4b</b>, and <i>tert</i>-butylurea <b>4c</b>) were synthesized and obtained in the cone conformation in solution, as shown by NMR studies. The X-ray crystal structure of <b>4c</b> is reported. The host–guest properties of these receptors toward several anions were investigated by ¹H NMR titrations. Phenylurea <b>4a</b> displayed a very efficient binding toward the spherical F^– and Cl^– anions, and the linear CN^– (log <i>K</i>_ass = 3.46, 3.50, and 4.02, respectively). In comparison to related bidentate phenylurea dihomooxacalix[4]­arenes, tetraphenylurea <b>4a</b> is more preorganized and the higher number of hydrogen bond donor sites provides a remarkable enhancement of its binding efficiency

Trans and Cis Effects of Axial Fluoroalkyl Ligands in Vitamin B₁₂ Analogues: Relationship between Alkyl- and Fluoroalkyl-Cobalamins

<b>CF₂HCbl</b>, <b>CF₃Cbl </b>, and <b>CF₃CH₂Cbl</b> have been synthesized and characterized in solution by ¹H NMR and UV–vis spectroscopy, and their X-ray crystal structures have been determined using synchrotron radiation. The structure of <b>CF₃CH₂Cbl</b> is reported for the first time, whereas those of <b>CF₂HCbl</b> and <b>CF₃Cbl</b> are re-examined to obtain more precise structural data. Comparison of the structural data obtained with the alkylcobalamin analogues, MeCbl and EtCbl, indicates that the Co–C and Co–NB3 bond lengths are shorter in the fluoroalkylcobalamins. The structural data of the fluoroalkylcobalamins previously reported in the literature had been conflicting in this regard. Thus, a much less dramatic shortening of the two axial bonds was found for <b>CF₃Cbl</b>, whereas in the case of <b>CF₂HCbl</b>, the Co–NB3 bond length is shorter than in MeCbl. Direct comparison of the structures of <b>CF₃CH₂Cbl</b> and EtCbl indicates a large distortion of the axial fragment in the former case that can be attributed to steric effects. A number of previously reported correlations of the effect of the β-ligand on the structure and properties of cobalamins are re-examined in light of the present results. Particular emphasis is placed on the axial fragment. This analysis substantially confirms and, with the new data reported here, adjusts and expands the data set for correlations between trans and cis influences of the β-ligand of cobalamins and their structure (Co–X and Co–NB3 distances and corrin fold angle) and properties (UV–vis spectra, NMR spectra, and p<i>K</i>_base‑off)

Trans and Cis Effects of Axial Fluoroalkyl Ligands in Vitamin B₁₂ Analogues: Relationship between Alkyl- and Fluoroalkyl-Cobalamins

<b>CF₂HCbl</b>, <b>CF₃Cbl </b>, and <b>CF₃CH₂Cbl</b> have been synthesized and characterized in solution by ¹H NMR and UV–vis spectroscopy, and their X-ray crystal structures have been determined using synchrotron radiation. The structure of <b>CF₃CH₂Cbl</b> is reported for the first time, whereas those of <b>CF₂HCbl</b> and <b>CF₃Cbl</b> are re-examined to obtain more precise structural data. Comparison of the structural data obtained with the alkylcobalamin analogues, MeCbl and EtCbl, indicates that the Co–C and Co–NB3 bond lengths are shorter in the fluoroalkylcobalamins. The structural data of the fluoroalkylcobalamins previously reported in the literature had been conflicting in this regard. Thus, a much less dramatic shortening of the two axial bonds was found for <b>CF₃Cbl</b>, whereas in the case of <b>CF₂HCbl</b>, the Co–NB3 bond length is shorter than in MeCbl. Direct comparison of the structures of <b>CF₃CH₂Cbl</b> and EtCbl indicates a large distortion of the axial fragment in the former case that can be attributed to steric effects. A number of previously reported correlations of the effect of the β-ligand on the structure and properties of cobalamins are re-examined in light of the present results. Particular emphasis is placed on the axial fragment. This analysis substantially confirms and, with the new data reported here, adjusts and expands the data set for correlations between trans and cis influences of the β-ligand of cobalamins and their structure (Co–X and Co–NB3 distances and corrin fold angle) and properties (UV–vis spectra, NMR spectra, and p<i>K</i>_base‑off)

Trans and Cis Effects of Axial Fluoroalkyl Ligands in Vitamin B₁₂ Analogues: Relationship between Alkyl- and Fluoroalkyl-Cobalamins

<b>CF₂HCbl</b>, <b>CF₃Cbl </b>, and <b>CF₃CH₂Cbl</b> have been synthesized and characterized in solution by ¹H NMR and UV–vis spectroscopy, and their X-ray crystal structures have been determined using synchrotron radiation. The structure of <b>CF₃CH₂Cbl</b> is reported for the first time, whereas those of <b>CF₂HCbl</b> and <b>CF₃Cbl</b> are re-examined to obtain more precise structural data. Comparison of the structural data obtained with the alkylcobalamin analogues, MeCbl and EtCbl, indicates that the Co–C and Co–NB3 bond lengths are shorter in the fluoroalkylcobalamins. The structural data of the fluoroalkylcobalamins previously reported in the literature had been conflicting in this regard. Thus, a much less dramatic shortening of the two axial bonds was found for <b>CF₃Cbl</b>, whereas in the case of <b>CF₂HCbl</b>, the Co–NB3 bond length is shorter than in MeCbl. Direct comparison of the structures of <b>CF₃CH₂Cbl</b> and EtCbl indicates a large distortion of the axial fragment in the former case that can be attributed to steric effects. A number of previously reported correlations of the effect of the β-ligand on the structure and properties of cobalamins are re-examined in light of the present results. Particular emphasis is placed on the axial fragment. This analysis substantially confirms and, with the new data reported here, adjusts and expands the data set for correlations between trans and cis influences of the β-ligand of cobalamins and their structure (Co–X and Co–NB3 distances and corrin fold angle) and properties (UV–vis spectra, NMR spectra, and p<i>K</i>_base‑off)