Crystal Engineering and Photomagnetic Studies of CN-Bridged Coordination Polymers Based on Octacyanidometallates(IV) and [Ni(cyclam)]2

A series of new CN-bridged coordination networks of different dimensionality and topology was obtained through the modification of reaction conditions between [Ni(cyclam)]²⁺ (cyclam = 1,4,8,11-tetraazacyclotetradecane) and [W(CN)₈]^4–. The factors determining the reaction pathway are temperature and addition of the LiCl electrolyte. The products include three negatively charged frameworks incorporating Li⁺ guests: the 1D Li₂[Ni(cyclam)][W(CN)₈]·6H₂O (1) straight chain, the 1D Li₂[Ni(cyclam)][W(CN)₈]·2H₂O (2) zigzag chain, and the 2D Li₂[Ni(cyclam)]₃[W(CN)₈]₂·24H₂O (3) honeycomb-like network, as well as the 3D two-fold interpenetrating [Ni(cyclam)]₅[Ni(CN)₄][W(CN)₈]₂·11H₂O (4) network and the 1D [Ni(cyclam)][Ni(CN)₄]·2H₂O (5) chain, which result from partial decomposition of the starting complexes. Together with the previously characterized 3D [Ni(cyclam)]₂[W(CN)₈]·16H₂O (6) network, they constitute the largest family of CN-bridged coordination polymers obtained from the same pair of building blocks. All compounds exhibit paramagnetic behavior because of the separation of paramagnetic nickel(II) centers through the diamagnetic polycyanidometallates. However, the presence of the photomagnetically active octacyanidotungstate(IV) ions allowed observation of the magnetic superexchange after the violet light excitation (405 nm) for compound 3, which constitutes the first example of the photomagnetic effect in a Ni^II–[W^IV(CN)₈] system. The photomagnetic investigations for fully hydrated and dehydrated sample of 3, as well as for the isostructural octacyanidomolybdate(IV)-based network are discussed.

Six coordination networks of different dimensionality and topology can be obtained from the same pair of building blocks: [Ni(cyclam)]²⁺ and [W(CN)₈]⁴⁻ depending on reaction conditions. The negatively charged 2D Li₂[Ni(cyclam)]₃[W(CN)₈]₂·nH₂O microporous network is the first example of the photomagnetic effect in a Ni^II−[W^IV(CN)₈] system.

An intramolecular relay catalysis strategy for Knoevenagel condensation and 1,3-dipolar cycloaddition domino reactions

A relay catalysis strategy was established by using a bifunctional catalyst which was prepared by immobilization of organic chains containing secondary amine and Cu(ii) complex onto silica-coated nano-Fe₃O₄. The simply prepared nanoparticles acted as efficient, intramolecular relays and magnetically recyclable base-metal bifunctional catalysts for Knoevenagel condensation and 1,3-dipolar cycloaddition domino reactions to prepare 5-substituted 1H-tetrazoles with excellent yields.

A magnetically recoverable bifunctional catalyst was synthesized and effectively used in Knoevenagel condensation and 1,3-dipolar cycloaddition domino reactions.

PbII-catalyzed transformation of aromatic nitriles to heptanitrogen anions via sodium azide: a combined experimental and theoretical study

Under hydrothermal conditions, an open-chain N₇³⁻ anion stabilized in a metal–organic framework (MOF) was achieved for the first time via the in situ reaction of 4-fluorobenzonitrile and sodium azide with Pb²⁺ ion as catalyst. The anion with C_2h symmetry in the MOF was studied by FT-IR, single-crystal XRD and theoretical calculations. Thermal analysis results demonstrated the stability of the anion in the MOF below 430 °C and a high energy content of 8.61 kJ g⁻¹. The anion is also a good reducing agent. It can easily react with basic KMnO₄ solution. Moreover, the present study indicates that the Pb²⁺ ion activates the azide rather than nitrile in the in situ reaction of nitriles with azides to form polynitrogen and this mechanism is a distinct contradiction with the previous results in which the nitrile reacts with azide in the presence of transition metal ions. Our findings may open a new avenue towards the synthesis and capture of polynitrogen compounds.

Heptanitrogen anion: a chain of seven nitrogen atoms stabilized in a MOF has been isolated for the first time.

High-pressure Raman study of Terephthalonitrile

The in situ high-pressure Raman spectra of Terephthalonitrile (TPN) have been investigated from ambient to 12.6GPa at room temperature. All the fundamental vibrational modes of TPN at ambient were assigned based on the first-principle calculations. A detailed Raman spectroscopy analysis revealed that TPN underwent a phase transition at ~5.3GPa. The frequencies of the TPN Raman peaks increase with increasing the pressure which can be attributed to the reduction in the interatomic distances and the escalation of effective force constants. The intensity of the C-C-C ring-out-plane deformation mode increases gradually as the frequency remains almost constant during the compression which can be explained by the existence of π-π interactions in TPN molecules. Additionally, the pressure-induced structural changes of TPN on the Fermi resonance between the C≡N out-of-plane vibration mode and the C-CN out-of-plane vibration mode have been analyzed.

New discrete iodometallates with in situ generated triimidazole derivatives as countercations (Mn+ = Ag+, Pb2+, Bi3+)

By employing solvothermal in situ N-alkylation of organic bases with alcohols, four new iodometallates were obtained, and their structures are reported.

Conversion of Arylboronic Acids to Tetrazoles Catalyzed by ONO Pincer-Type Palladium Complex

A convenient synthesis of a library of tetrazoles through a novel and operationally simple protocol effecting the direct conversion of arylboronic acids catalyzed by a new ONO pincer-type Pd(II) complex under mild reaction conditions using the readily available reagents is reported. The palladium complex was reused up to four cycles in an open-flask condition.

New in situ generated acylhydrazidate-coordinated complexes and acylhydrazide molecules: Synthesis, structural characterization and photoluminescence property

By utilizing the hydrothermal in situ acylation of organic acids with N2H4, three acylhydrazidate-coordinated compounds [Mn(L1)2(H2O)2] (L1=2,3-quinolinedicarboxylhydrazidate; HL1=2,3-dihydropyridazino[4,5-b] quinoline-1,4-dione) 1, [Mn2(ox)(L2)2(H2O)6]·2H2O (L2=benzimidazolate-5,6-dicarboxylhydrazide; HL2=6,7-dihydro-1H-imidazo[4,5-g]phthalazine-5,8-dione; ox=oxalate) 2, and [Cd(HL3)(bpy)] (L3=4,5-di(3'-carboxylphenyl)phthalhydrazidate; H3L3=6,7-dihydro-1H-imidazo[4,5-g]phthalazine-5,8-dione; bpy=2,2'-bipyridine) 3, as well as two acylhydrazide molecules L4 (L4=oxepino[2,3,4-de:7,6,5-d'e']diphthalazine-4,10(5H,9H)-dione) 4 and L5 (L5=4,5-dibromophthalhydrazide; L5=6,7-dibromo-2,3-dihydrophthalazine-1,4-dione) 5 were obtained. X-ray single-crystal diffraction analysis reveals that (i) 1 only possesses a mononuclear structure, but it self-assembles into a 2-D supramolecular network via the NhydrazineH⋯Nhydrazine and OwH⋯Ohydroxylimino interactions; (ii) 2 exhibits a dinuclear structure. Ox acts as the linker, while L2 just serves as a terminal ligand; (iii) In 3, L3 acts as a 3-connected node to propagate the 7-coordinated Cd(2+) centers into a 1-D double-chain structure; (iv) 4 is a special acylhydrazide molecule. Two OH groups for the intermediates 3,3'-biphthalhydrazide further lose one water molecule to form 4; (v) 5 is a common monoacylhydrazide molecule. Via the NhydrazineH⋯Ohydrazine, OhydroxyliminoH⋯Oacylamino and the π⋯π interactions, it self-assembles into a 2-D supramolecular network. The photoluminescence analysis reveals that 4 emits light with the maxima at 510nm.

Measurement of a new parameter representing the gas transport properties of the catalyst layers of polymer electrolyte fuel cells

The optimization of the catalyst layers is necessary for obtaining a better fuel cell performance and reducing fuel cell cost.

Structural snapshots in the copper(ii) induced azide–nitrile cycloaddition: effects of peripheral ligand substituents on the formation of unsupported μ1,1-azido vs. μ1,4-tetrazolato bridged complexes

Peripheral substituents on click-derived tripodal ligands dictate the reactivity of their copper(ii) azido complexes.