Selective Supramolecular Recognition of Nitroaromatics by a Fluorescent Metal–Organic Cage Based on a Pyridine-Decorated Dibenzodiaza-Crown Macrocyclic Co(II) Complex

Two isomorphous fluorescent (FL) lantern-shaped metal–organic cages 1 and 2 were prepared by coordination-directed self-assembly of Co(II) centers with a new aza-crown macrocyclic ligand bearing pyridine pendant arms (Lpy). The cage structures were determined using single-crystal X-ray diffraction analysis, thermogravimetric, elemental microanalysis, FT-IR spectroscopy, and powder X-ray diffraction. The crystal structures of 1 and 2 show that anions (Cl– in 1 and Br– in 2) are encapsulated within the cage cavity. 1 and 2 bear two coordinated water molecules that are directed inside the cages, surrounded by the eight pyridine rings at the “bottom” and the “roof” of the cage. These hydrogen bond donors, π systems, and the cationic nature of the cages enable 1 and 2 to encapsulate the anions. FL experiments revealed that 1 could detect nitroaromatic compounds by exhibiting selective and sensitive fluorescence quenching toward p-nitroaniline (PNA), recommending a limit of detection of 4.24 ppm. Moreover, the addition of 50 μL of PNA and o-nitrophenol to the ethanolic suspension of 1 led to a significant large FL red shift, namely, 87 and 24 nm, respectively, which were significantly higher than the corresponding values observed in the presence of other nitroaromatic compounds. The titration of the ethanolic suspension of 1, with various concentrations of PNA (>12 μM) demonstrated a concentration-dependent emission red shift. Hence, the efficient FL quenching of 1 was capable of distinguishing the dinitrobenzene isomers. Meanwhile, the observed red shift (10 nm) and quenching of this emission band under the influence of a trace amount of o- and p-nitrophenol isomers also showed that 1 could discriminate between o- and p-nitrophenol. Replacement of the chlorido with a bromido ligand in 1 generated cage 2 which was a more electron-donating cage than 1. The FL experiments showed that 2 was partially more sensitive and less selective toward NACs than 1

Dynamic NMR and Computational Studies Inform the Conformational Description of Dendrillane Terpenes from the Nudibranch <i>Goniobranchus coi</i>

Two new oxygenated terpenes (1 and 2) have been characterized from the Australian nudibranch Goniobranchus coi. Broadened 1H NMR signals, together with the absence of individual carbon NMR signals, complicated analysis of 5,9-epoxydendrillolide A (1); increasing the temperature to 323 K revealed the missing NMR signals. Low-temperature 1H NMR experiments provided an activation barrier of ∼15 kcal mol–1 and, together with DFT calculations, supported interconversion of a twist chair conformer with two different chair conformers. X-ray crystallographic analysis coupled with biosynthetic reasoning suggested a (5R, 8S, 9R, 13R, 14R, 15R, 16R) configuration. Ketone 2 demonstrated similar dynamic conformational processes to 1

sj-cif-2-npx-10.1177_1934578X211055025 - Supplemental material for Oxygenated Sesquiterpenes From the Indo-Pacific Nudibranch <i>Ardeadoris rubroannulata</i>: Structure Revision of Pu’ulenal

Supplemental material, sj-cif-2-npx-10.1177_1934578X211055025 for Oxygenated Sesquiterpenes From the Indo-Pacific Nudibranch Ardeadoris rubroannulata: Structure Revision of Pu’ulenal by Patrick T. Narbutas, Gregory K. Pierens, Jack K. Clegg and Mary J. Garson in Natural Product Communications</p

Self-Assembly of a Metallomacrocycle Templated by Iron(II)

An unusual discrete heteronuclear metallomacrocycle was designed and synthesized via metal-ion-directed self-assembly by an iron(II) template. The formation of this metallomacrocycle was demonstrated by X-ray crystallography, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, and NMR spectroscopy

Dynamic NMR and Computational Studies Inform the Conformational Description of Dendrillane Terpenes from the Nudibranch <i>Goniobranchus coi</i>

Two new oxygenated terpenes (1 and 2) have been characterized from the Australian nudibranch Goniobranchus coi. Broadened 1H NMR signals, together with the absence of individual carbon NMR signals, complicated analysis of 5,9-epoxydendrillolide A (1); increasing the temperature to 323 K revealed the missing NMR signals. Low-temperature 1H NMR experiments provided an activation barrier of ∼15 kcal mol–1 and, together with DFT calculations, supported interconversion of a twist chair conformer with two different chair conformers. X-ray crystallographic analysis coupled with biosynthetic reasoning suggested a (5R, 8S, 9R, 13R, 14R, 15R, 16R) configuration. Ketone 2 demonstrated similar dynamic conformational processes to 1

sj-docx-1-npx-10.1177_1934578X211055025 - Supplemental material for Oxygenated Sesquiterpenes From the Indo-Pacific Nudibranch <i>Ardeadoris rubroannulata</i>: Structure Revision of Pu’ulenal

Supplemental material, sj-docx-1-npx-10.1177_1934578X211055025 for Oxygenated Sesquiterpenes From the Indo-Pacific Nudibranch Ardeadoris rubroannulata: Structure Revision of Pu’ulenal by Patrick T. Narbutas, Gregory K. Pierens, Jack K. Clegg and Mary J. Garson in Natural Product Communications</p

Self-Assembly of a Metallomacrocycle Templated by Iron(II)

An unusual discrete heteronuclear metallomacrocycle was designed and synthesized via metal-ion-directed self-assembly by an iron(II) template. The formation of this metallomacrocycle was demonstrated by X-ray crystallography, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, and NMR spectroscopy

Cobalt(II), Copper(II), and Zinc(II) Framework Systems Derived from Ditopic Pyridyl-Acetylacetone and Pyridyl-Pyrazole Ligands

The synthesis of two new bifuctional ligand sytems incorporating two different “classical” coordination units connected by a bent (but flexible) thioether linkage is reported. The new systems are the β-diketone-pyridyl derivative, 3-(pyridin-4-ylthio)pentane-2,4-dione (L), and its hydrazine condensation product, the pyridyl-pyrazole species 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)pyridine (L). Both systems were designed for use in metal−organic framework studies. With L1, four metal-containing products were crystallized, [Cu(L1−H)2]n (1), {[Cu(L1−H)2]·0.5H2O·CHCl3}n (2), {[Zn(L1−H)2]·2H2O}n (3), and [Zn(L1−H)2]·2MeOH}n (4); these display three different array types. Compound 1 incorporates 5-coordinate Cu(II) ions with square pyramidal stereochemistry. The β-diketonato groups from two ligands coordinate in the basal plane with the apical position occupied by a pyridyl nitrogen from a third ligand that bridges to an adjacent copper center. Propagation of this coordination motif produces a 1D chain. In 2, which is a pseudo-polymorphic phase of 1, each Cu(II) ion is 6-coordinate with each metal center being bound by two bidentate β-diketonato groups and two pyridyl donors from four different ligands in a cis configuration. The ligand arrangement bridges each metal to four others producing an infinite 2D rhombic grid [(4,4) net]. The grids stack to form channels containing disordered water and chloroform molecules; the solvent-accessible space is 33% of the crystal volume. Crystals of 3 are isostructural with 2, except that they incorporate water as the only solvate in the channels. The solvent-accessible voids constitute 22% of the crystal volume, reflecting closer packing of adjacent grids. A TGA study showed that the water molecules are removed by 375 K and that the resulting desolvated complex is stable up to 573 K. Compound 4 is a pseudo-polymorph of 3 in which the 6-coordinate Zn(II) coordination is similar to that in 3 but with polymeric connectivity producing a chiral [8,4] type 3D network (space group P41212). Helical channels corresponding to 25% of the crystal volume run parallel to the 4-fold axes and are occupied by methanol guests. With 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)pyridine (L2), an extended array consisting of zwitterionic [Co(L2+H)Cl3]n (5) units linked by hydrogen bonds and the metal-linked molecular framework species{[Zn(L2)Cl2]·0.5H2O}n (6) were obtained. The cobalt center in 5 is tetrahedrally coordinated by three chloride ions and a pyrazole nitrogen from (L2+H); the protonation is present at the pyridyl nitrogen atom. This protonated pyridyl nitrogen forms a charge-assisted hydrogen bond of type N−H+···Cl with a coordinated chloride from an adjacent complex to yield a hydrogen-bonded chainlike array. Intermolecular N−H···Cl hydrogen bonds also exist between the non-deprotonated pyrazole nitrogen and adjacent chloro ligands. Each tetrahedral Zn(II) center in 6 is coordinated to two chloride ions, a pyridyl nitrogen from one L2 ligand and a pyrazole nitrogen from another. Each L2 thus bridges adjacent Zn(II) centers, forming 1D polymeric chains that aggregate in the crystal to produce narrow channels occupied by water molecules

Cobalt(II), Copper(II), and Zinc(II) Framework Systems Derived from Ditopic Pyridyl-Acetylacetone and Pyridyl-Pyrazole Ligands

The synthesis of two new bifuctional ligand sytems incorporating two different “classical” coordination units connected by a bent (but flexible) thioether linkage is reported. The new systems are the β-diketone-pyridyl derivative, 3-(pyridin-4-ylthio)pentane-2,4-dione (L), and its hydrazine condensation product, the pyridyl-pyrazole species 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)pyridine (L). Both systems were designed for use in metal−organic framework studies. With L1, four metal-containing products were crystallized, [Cu(L1−H)2]n (1), {[Cu(L1−H)2]·0.5H2O·CHCl3}n (2), {[Zn(L1−H)2]·2H2O}n (3), and [Zn(L1−H)2]·2MeOH}n (4); these display three different array types. Compound 1 incorporates 5-coordinate Cu(II) ions with square pyramidal stereochemistry. The β-diketonato groups from two ligands coordinate in the basal plane with the apical position occupied by a pyridyl nitrogen from a third ligand that bridges to an adjacent copper center. Propagation of this coordination motif produces a 1D chain. In 2, which is a pseudo-polymorphic phase of 1, each Cu(II) ion is 6-coordinate with each metal center being bound by two bidentate β-diketonato groups and two pyridyl donors from four different ligands in a cis configuration. The ligand arrangement bridges each metal to four others producing an infinite 2D rhombic grid [(4,4) net]. The grids stack to form channels containing disordered water and chloroform molecules; the solvent-accessible space is 33% of the crystal volume. Crystals of 3 are isostructural with 2, except that they incorporate water as the only solvate in the channels. The solvent-accessible voids constitute 22% of the crystal volume, reflecting closer packing of adjacent grids. A TGA study showed that the water molecules are removed by 375 K and that the resulting desolvated complex is stable up to 573 K. Compound 4 is a pseudo-polymorph of 3 in which the 6-coordinate Zn(II) coordination is similar to that in 3 but with polymeric connectivity producing a chiral [8,4] type 3D network (space group P41212). Helical channels corresponding to 25% of the crystal volume run parallel to the 4-fold axes and are occupied by methanol guests. With 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)pyridine (L2), an extended array consisting of zwitterionic [Co(L2+H)Cl3]n (5) units linked by hydrogen bonds and the metal-linked molecular framework species{[Zn(L2)Cl2]·0.5H2O}n (6) were obtained. The cobalt center in 5 is tetrahedrally coordinated by three chloride ions and a pyrazole nitrogen from (L2+H); the protonation is present at the pyridyl nitrogen atom. This protonated pyridyl nitrogen forms a charge-assisted hydrogen bond of type N−H+···Cl with a coordinated chloride from an adjacent complex to yield a hydrogen-bonded chainlike array. Intermolecular N−H···Cl hydrogen bonds also exist between the non-deprotonated pyrazole nitrogen and adjacent chloro ligands. Each tetrahedral Zn(II) center in 6 is coordinated to two chloride ions, a pyridyl nitrogen from one L2 ligand and a pyrazole nitrogen from another. Each L2 thus bridges adjacent Zn(II) centers, forming 1D polymeric chains that aggregate in the crystal to produce narrow channels occupied by water molecules

Halogen-Bond-Modulated Organization of [Ni(terpy-ph)₂]I₂ Complexes in Heteromeric Three-Component Systems

The encapsulation of metal complexes within halogen-bonded networks may lead to modulation of their properties in the solid state without the need to chemically incorporate donor or acceptor moieties on the metal complex itself. Here, we investigate the effect of anionic halogen-bonded structure formation on the organization of arene-rich bis­(4′-phenyl-2,2′:6′,2″-terpyridine)­nickel­(II) cations, varying both the topicity and the geometry of the halogen bond donor in a heteromeric three-component system. The X-ray structures of four cocrystals (1–4), [Ni­(terpy-ph)2]­[(1,2-DITFB)4(I–)2] (1), [Ni­(terpy-ph)2]­[(1,3-DITFB)­(I–)2] (2), [Ni­(terpy-ph)2]2[(1,4 DITFB)3(I–)3]­(I–)·9H2O (3), and [Ni­(terpy-ph)2]­[(1,3,5-TITFB)2(H2O)­(I–)2]·2H2O (4), as well as the iodide salt of the parent complex [Ni­(terpy-ph)2]­I2·4H2O are reported along with characterization to assess bulk sample and phase purity. Within assemblies of complex cations, we observe the ubiquitous aryl embrace motif often seen in the crystal packing of such terpyridine complexes; however, these assemblies are separated from one another by a variety of halogen-bonded structures, including discrete supramolecular complexes, 1D chains, pseudo-2D sheets, and unusual racemic double helices. The results herein demonstrate how typical crystal packing motifs of metal terpy-ph complexes can be altered and disrupted through their incorporation into halogen-bonded heteromeric three-component systems