Porous Metal–Organic Framework Catalyzing the Three-Component Coupling of Sulfonyl Azide, Alkyne, and Amine

The robustly porous metal–organic framework MOF–Cu₂I₂(BTTP4) (BTTP4 = benzene-1,3,5-triyl triiso­nicotinate) was shown to work as an efficiently heterogeneous catalyst for the three-component coupling of sulfonyl azides, alkynes, and amines, leading to the formation of <i>N</i>-sulfonyl amidines in good yields. MOF–Cu₂I₂(BTTP4) can be recycled by simple filtration and reused at least four times without any loss in yield. Studies of the ligand effects on the three-component coupling reactions showed that BTTP4 could enhance the rate, as well as the chemoselectivity, when aromatic alkynes were employed. The catalytic process has been thoroughly studied by means of single-crystal and powder X-ray diffraction, gas and solvent adsorption, in situ ¹H NMR and FT-IR spectroscopy, X-ray photoelectron spectra (XPS), and ICP analysis of Cu leaching

Porous Metal–Organic Framework Catalyzing the Three-Component Coupling of Sulfonyl Azide, Alkyne, and Amine

The robustly porous metal–organic framework MOF–Cu₂I₂(BTTP4) (BTTP4 = benzene-1,3,5-triyl triiso­nicotinate) was shown to work as an efficiently heterogeneous catalyst for the three-component coupling of sulfonyl azides, alkynes, and amines, leading to the formation of <i>N</i>-sulfonyl amidines in good yields. MOF–Cu₂I₂(BTTP4) can be recycled by simple filtration and reused at least four times without any loss in yield. Studies of the ligand effects on the three-component coupling reactions showed that BTTP4 could enhance the rate, as well as the chemoselectivity, when aromatic alkynes were employed. The catalytic process has been thoroughly studied by means of single-crystal and powder X-ray diffraction, gas and solvent adsorption, in situ ¹H NMR and FT-IR spectroscopy, X-ray photoelectron spectra (XPS), and ICP analysis of Cu leaching

A CdSO₄‑Type 3D Metal–Organic Framework Showing Coordination Dynamics on Cu²⁺ Axial Sites: Vapochromic Response and Guest Sorption Selectivity

A unique 2-fold interpenetrated CdSO₄ coordination network of the formula {[Cu₂(4-pmpmd)₂(CH₃OH)₄(opd)₂]·2H₂O}_<i>n</i> [4-pmpmd = <i>N</i>,<i>N</i>′-bis­(4-pyridylmethyl)­phenyldiimide; opd = <i>o</i>-phthalic acid] has been synthesized and characterized by IR spectra, thermogravimetric (TG) analyses, elemental analyses, and single crystal and powder X-ray diffraction methods. The metal–organic framework (MOF) exhibits reversible dehydration and rehydration in a single-crystal-to-single-crystal (SC–SC) process. Moreover, the dehydrated material, having coordinatively unsaturated Cu²⁺ sites, can encapsulate CH₃OH molecules with a color change, again in a reversible SC–SC fashion, and shows selective adsorption of CO₂ over N₂ and H₂. This feature of obvious color variation induced by the presence of small hydroxylic molecules is highly promising for detecting hydroxylic molecules through a simple sensing mechanism. In addition, the MOF selectively interacts with hydroxylic guests and shows sorption selectivity for water, methanol, ethanol, and <i>n</i>-propanol over benzene guests. Notably, this compound shows complete selectivity in adsorption for <i>n</i>-propanol over 2-propanol owing to the effect of shape exclusion

Cyclometalated Platinum(II) Complexes of 1,3-Bis(1‑<i>n</i>‑butylpyrazol-3-yl)benzenes: Synthesis, Characterization, Electrochemical, Photophysical, and Gelation Behavior Studies

A new series of cyclometalated platinum­(II) complexes of N^C^N ligands, where N^C^N = 1,3-bis­(1-<i>n</i>-alkylpyrazol-3-yl)­benzene (bpzb), namely, [Pt­(bpzb)­Cl] (<b>1</b> and <b>2</b>) and [Pt­(bpzb)­(CC–R)] (<b>3</b>–<b>10</b>) (R = C₆H₅, C₆H₄–OCH₃-<i>p</i>, C₆H₄–NO₂-<i>p</i>, C₆H₄–NH₂-<i>p</i>, 4-cholesteryl phenyl carbamate, and cholesteryl methylcarbamate) were synthesized and characterized. Their electrochemical and photophysical properties were investigated. Two of the platinum­(II) complexes were also structurally characterized by X-ray crystallography, and short intermolecular C–H···Pt contacts were observed. Vibronic-structured emission bands originating from triplet IL (³IL) excited states of the bpzb ligands with mixing of some ³MLCT [dπ­(Pt)→π*­(bpzb)] character were observed in solution state. Interestingly, complex <b>5</b> shows a low-energy emission that is derived from the involvement of the <i>p</i>-nitrophenylethynyl ligand. Complex <b>9</b> with hydrophobic cholesteryl 4-ethynylphenyl carbamate ligand was found to form stable metallogels in several organic solvents, which are responsive to mechanical sonication and thermal stimuli and show circular dichroism activity

Electrospun Hierarchical TiO₂ Nanorods with High Porosity for Efficient Dye-Sensitized Solar Cells

Ultraporous anatase TiO₂ nanorods with a composite structure of mesopores and macropores fabricated via a simple microemulsion electrospinning approach were first used as photoanode materials for high-efficiency dye-sensitized solar cells (DSSCs). The special multiscale porous structure was formed by using low-cost paraffin oil microemulsion droplets as the soft template, which can not only provide enhanced adsorption sites for dye molecules but also facilitate the electrolyte diffusion. The morphology, porosity, and photovoltaic and electron dynamic characteristics of the porous TiO₂ nanorod based DSSCs were investigated in detail by scanning electron microscopy (SEM), N₂ sorption measurements, current density–voltage (<i>J</i>–<i>V</i>) curves, UV–vis diffuse reflectance spectra, electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS), and open-circuit voltage decay (OCVD) measurements. The results revealed that, although fewer amounts of dyes were anchored on the porous TiO₂ nanorod films, they exhibited stronger light scattering ability, fast electrolyte diffusion, and extended electron lifetime compared to the commercial P25 nanoparticles. A power conversion efficiency of 6.07% was obtained for the porous TiO₂ nanorod based DSSCs. Moreover, this value can be further improved to 8.53% when bilayer structured photoanode with porous TiO₂ nanorods acting as the light scattering layer was constructed. This study demonstrated that the porous TiO₂ nanorods can work as promising photoanode materials for DSSCs

Metal-Directed Assembly of Hexameric Ring, Dimeric Ring and 1D Chain from a Branched Tripodal Ligand

To explore the influencing effect of different transition metal ions on the coordination geometries and structural architectures of metal–organic complexes with the same ligand, 10 new coordination compounds of a monobranched tripodal ligand <i>N</i>-[<i>N</i>′-(carboxymethyl)benzimidazol-2-ylmethyl]-<i>N</i>,<i>N</i>-bis(benzimidazol-2-ylmethyl)amine (HAcNTB), namely, [Co₆(AcNTB)₆]·6ClO₄·36H₂O (<b>Co-ClO</b>_<b>4</b>), [Co₆(AcNTB)₆]·6BF₄·9H₂O·3CHCl₃ (<b>Co-BF</b>_<b>4</b>), [Zn₆(AcNTB)₆]·6ClO₄·2CHCl₃·15H₂O (<b>Zn-ClO</b>_<b>4</b>), [Zn₆(AcNTB)₆]·6BF₄·52H₂O (<b>Zn-BF</b>_<b>4</b>), [Ni₂(AcNTB)₂(H₂O)₂]·2ClO₄·2CH₃OH·2H₂O (<b>Ni-ClO</b>_<b>4</b>), [Ni₂(AcNTB)₂(H₂O)₂]·2BF₄·4CH₃OH (<b>Ni-BF</b>_<b>4</b>), {[Mn(AcNTB)(CH₃OH)]·ClO₄·H₂O}_<i>n</i> (<b>Mn-ClO</b>_<b>4</b>), {[Mn(AcNTB)(CH₃OH)]·BF₄·H₂O}_<i>n</i> (<b>Mn-BF</b>_<b>4</b>), {[Cd(AcNTB)(CH₃OH)]·ClO₄·H₂O}_<i>n</i>] (<b>Cd-ClO</b>_<b>4</b>), {[Cd(AcNTB)(CH₃OH)]·BF₄·H₂O}_<i>n</i> (<b>Cd-BF</b>_<b>4</b>) have been synthesized and characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction. In isomorphous complexes <b>Co-ClO</b>_<b>4</b>, <b>Co-BF</b>_<b>4</b>, <b>Zn-ClO</b>_<b>4</b>, and <b>Zn-BF</b>_<b>4</b>, the metal centers (Zn²⁺ and Co²⁺) are five-coordinated in a trigonal bipyramid geometry, leading to formation of hexameric rings through linkage of six metals and six ligands without coordination of anion and solvent molecules. In isomorphous complexes <b>Ni-ClO</b>_<b>4</b> and <b>Ni-BF</b>_<b>4</b>, the metal centers (Ni²⁺) prefer a six-coordinated octahedral geometry, resulting in dinuclear rings through connection of two metals and two ligands with water molecule participating in coordination. While in the isomorphous complexes <b>Mn-ClO</b>_<b>4</b>, <b>Mn-BF</b>_<b>4</b>, <b>Cd-ClO</b>_<b>4</b>, and <b>Cd-BF</b>_<b>4</b>, the metal centers are seven-coordinated to form one-dimensional (1D) chain, showing an irregularly distorted geometry with water or methanol solvents entering coordination sphere. The coordination geometric preference of different metal ions with respect to the metal ionic radii and coordination numbers play an important role in determining the assembly fashions. Density functional theory (DFT) calculations have been performed to track the stability effects obtained by the metal ions in different coordination environments

Anion Modulated Structural Diversification in the Assembly of Cd(II) Complexes Based on a Balance-like Dipodal Ligand

Reaction of a balance-like dipodal ligand 2,6-bis­(pyridiyl) hexahydro-4,8-ethenopyrrolo [3,4-f]­isoindole-1,3,5,7-tetrone (3-pybtd) with various Cd­(II) salts afforded eight complexes, namely, [Cd₂(3-pybtd)₂(NO₃)₄(C₂H₅OH)₂(H₂O)₂] (<b>1</b>), [Cd₂(3-pybtd)₂(SiF₆)₂(DMF)₄(H₂O)₂]­(H₂O)₄·(DMF)₂ (<b>2</b>), {[Cd­(3-pybtd)₂(H₂O)₄]­(ClO₄)₂}_<i>n</i> (<b>3</b>), {[Cd­(3-pybtd)₂(OTf)₂]·THF}_<i>n</i> (<b>4</b>), {[Cd­(3-pybtd)₂(SCN)₂]·(H₂O)₂}_<i>n</i> (<b>5</b>), [Cd­(3-pybtd)­(OTs)₂(DMF)₂]_<i>n</i> (<b>6</b>), [Cd­(3-pybtd)₂(OTs)₂]_<i>n</i> (<b>7</b>), and {[Cd₂(3-pybtd)₂Cl_10/3]­[CdCl_8/3]·(H₂O)₃}_<i>n</i> (<b>8</b>). Complexes <b>1</b> and <b>2</b> are zero-dimensional (0D) square-like or olive-like dimeric M₂L₂ metallacycles, showing a pair of shape-modified molecular rectangles due to different conformations of the ligands and coordination orientation of the metal centers. Complexes <b>3</b>–<b>5</b> are one-dimensional (1D) looplike chains composed of olive-like M₂L₂ metallacycle building units as in <b>2</b>, showing 0D → 1D dimension increase via ligand addition, while complex <b>8</b> is a three-dimensional (3D) framework retaining the same olive-like M₂L₂ metallacycle, showing 0D → 3D dimension increase via linkage of μ_<i>3</i><i>-</i>Cl bridged Cd­(II) clusters. Complex <b>6</b> is a wave-like M_<i>n</i>L_<i>n</i> chain, possessing the same ML building units as in <b>1</b> but showing 0D → 1D dimension increase via ring-opening polymerization. Replacement of DMF molecules from the coordination sphere in <b>6</b> by the ligands resulted in a two-dimensional (2D) (4, 4) network of <b>7</b>, showing 1D → 2D dimension increase from <b>6</b> via ligand addition or 1D → 2D dimension increase from <b>3</b>–<b>5</b> via ring-opening polymerization. Complexes <b>3</b>–<b>5</b> also represent a series of supramolecular isomorphs displaying anion exchange properties. Electrospray ionization mass spectrometry (ESI-MS) studies in solution suggest that the discrete and infinite structures in <b>1</b>, <b>6</b>, and <b>7</b> are assembled from the same monomeric ML building blocks, which crystallize in a different way to lead to structural diversification via dimerization or polymerization during the crystallization

Tuning Spin–Spin Coupling in Quinonoid-Bridged Dicopper(II) Complexes through Rational Bridge Variation

Bridged metal complexes [{Cu­(tmpa)}₂­(μ-L¹_–2H)]­(ClO₄)₂ (<b>1</b>), [{Cu­(tmpa)}₂­(μ-L²_–2H)]­(ClO₄)₂ (<b>2</b>), [{Cu­(tmpa)}₂­(μ-L³_–2H)]­(BPh₄)₂ (<b>3</b>), and [{Cu­(tmpa)}₂­(μ-L⁴_–2H)]­(ClO₄)₂ (<b>4</b>) (tmpa = tris­(2-pyridyl­methyl)­amine, L¹ = chloranilic acid, L² = 2,5-dihydroxy-1,4-benzoquinone, L³ = (2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, L⁴ = azophenine) were synthesized from copper­(II) salts, tmpa, and the bridging quinonoid ligands in the presence of a base. X-ray structural characterization of the complexes showed a distorted octahedral environment around the copper­(II) centers for the complexes <b>1</b>–<b>3</b>, the donors being the nitrogen atoms of tmpa, and the nitrogen or oxygen donors of the bridging quinones. In contrast, the copper­(II) centers in <b>4</b> display a distorted square-pyramidal coordination, where one of the pyridine arms of each tmpa remains uncoordinated. Bond-length analyses within the bridging ligand exhibit localization of the double bonds inside the bridge for <b>1</b>–<b>3</b>. In contrast, complete delocalization of double bonds within the bridging ligand is observed for <b>4</b>. Temperature-dependent magnetic susceptibility measurements on the complexes reveal an antiferromagnetic coupling between the copper­(II) ions. The strength of antiferromagnetic coupling was observed to depend on the energy of the HOMO of the bridging quinone ligands, with exchange coupling constants <i>J</i> in the range between −23.2 and −0.6 cm^–1 and the strength of antiferromagnetic coupling of <b>4</b> > <b>3</b> > <b>2</b> > <b>1</b>. Broken-symmetry density functional theory calculations (DFT) revealed that the orientation of magnetic orbitals in <b>1</b> and <b>2</b> is different than that in <b>3</b> and <b>4</b>, and this results in two different exchange pathways. These results demonstrate how bridge-mediated spin–spin coupling in quinone-bridged metal complexes can be strongly tuned by a rational design of the bridging ligand employing the [O] for [NR] isoelectronic analogy

Rational Surface Engineering of Anatase Titania Core–Shell Nanowire Arrays: Full-Solution Processed Synthesis and Remarkable Photovoltaic Performance

The high-performance of a well-aligned 1D nanostructured electrode relies largely on a smart and rational modification with other active nanomaterials. Herein, we present a facile solution-based route to fabricate a well-aligned metal oxide-based core–shell hybrid arrays on TCO substrate. Demonstrated samples included nanowire@nanoparticle (TNW@NP) or nanowire@nanosheet (TNW@NS) with a unique porous core/shell nanowire arrays architecture in the absence or presence of DETA during the solvothermal treatment process. The “alcoholysis” and “ripening” growth mechanism is proposed to explain the formation of honeycomb-like nanosheets shell on nanowires core. Based on careful control of experimental condition, a novel double layered TiO₂ photoanode (DL-TNW@NS-YSHTSs) consisting of 16 μm thick TNW@NS under layer and 6 μm thick yolk–shell hierarchical TiO₂ microspheres (YSHTSs) top layer can be obtained, exhibiting an impressive PCE over 10% at 100 mW cm^–2, which can be attributed to the well-organized photoanode composed of hierarchical core–shell arrays architecture and yolk–shell hollow spheres architecture with synergistic effects of high dye loading and superior light scattering for prominent light harvesting efficiency

Tuning Spin–Spin Coupling in Quinonoid-Bridged Dicopper(II) Complexes through Rational Bridge Variation

Bridged metal complexes [{Cu­(tmpa)}₂­(μ-L¹_–2H)]­(ClO₄)₂ (<b>1</b>), [{Cu­(tmpa)}₂­(μ-L²_–2H)]­(ClO₄)₂ (<b>2</b>), [{Cu­(tmpa)}₂­(μ-L³_–2H)]­(BPh₄)₂ (<b>3</b>), and [{Cu­(tmpa)}₂­(μ-L⁴_–2H)]­(ClO₄)₂ (<b>4</b>) (tmpa = tris­(2-pyridyl­methyl)­amine, L¹ = chloranilic acid, L² = 2,5-dihydroxy-1,4-benzoquinone, L³ = (2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, L⁴ = azophenine) were synthesized from copper­(II) salts, tmpa, and the bridging quinonoid ligands in the presence of a base. X-ray structural characterization of the complexes showed a distorted octahedral environment around the copper­(II) centers for the complexes <b>1</b>–<b>3</b>, the donors being the nitrogen atoms of tmpa, and the nitrogen or oxygen donors of the bridging quinones. In contrast, the copper­(II) centers in <b>4</b> display a distorted square-pyramidal coordination, where one of the pyridine arms of each tmpa remains uncoordinated. Bond-length analyses within the bridging ligand exhibit localization of the double bonds inside the bridge for <b>1</b>–<b>3</b>. In contrast, complete delocalization of double bonds within the bridging ligand is observed for <b>4</b>. Temperature-dependent magnetic susceptibility measurements on the complexes reveal an antiferromagnetic coupling between the copper­(II) ions. The strength of antiferromagnetic coupling was observed to depend on the energy of the HOMO of the bridging quinone ligands, with exchange coupling constants <i>J</i> in the range between −23.2 and −0.6 cm^–1 and the strength of antiferromagnetic coupling of <b>4</b> > <b>3</b> > <b>2</b> > <b>1</b>. Broken-symmetry density functional theory calculations (DFT) revealed that the orientation of magnetic orbitals in <b>1</b> and <b>2</b> is different than that in <b>3</b> and <b>4</b>, and this results in two different exchange pathways. These results demonstrate how bridge-mediated spin–spin coupling in quinone-bridged metal complexes can be strongly tuned by a rational design of the bridging ligand employing the [O] for [NR] isoelectronic analogy