Silver(i) complexes of bis- and tris-(pyrazolyl)azine derivatives - dimers, coordination polymers and a pentametallic assembly

Silver(i) complexes of 2,4,6-tri(pyrazol-1-yl)pyridine (tpp), 2,4,6-tri(pyrazol-1-yl)pyrimidine (tpym), 2,4,6-tri(pyrazol-1-yl)-1,3,5-triazine (tpt) and 2,4-di(pyrazol-1-yl)-1,3,5-triazine (bpt) are reported. Dinuclear [Ag2(μ-tpp)2(MeCN)2][BF4]2·2MeCN and [Ag2(μ-tpym)2(MeCN)2][BF4]2 are formed from approximately planar [AgL(NCMe)]+ (L = tpp or bpym) centres, which dimerise via apical interactions to the pendant pyrazolyl donor on each ligand. Two polymeric solvatomorph phases [Ag2(μ-tpp)2][BF4]2·nMeNO2 were obtained by crystallising AgBF4 and tpp from nitromethane solution. One is composed of the same dimeric [Ag2(μ-tpp)2]2+ motif as the MeCN solvates, but with semibridging pyrazolyl substitutents replacing the solvent ligands. The other form has helicate [Ag2(μ-tpp)2]2+ dimers linked into chains by unsupported AgAg interactions. In contrast, [Ag5(μ3-tpym)4][BF4]5·2MeNO2 contains discrete pentametallic assemblies, of a flattened [Ag4(μ-tpym)4]4+ molecular square centred by the fifth silver ion. Three helical or linear 1D coordination polymer topologies are described for [Ag(μ-tpt)]X (X- = BF4- or ClO4-), where ditopic tpt ligands bind one silver ion in a [2 + 1] geometry and the other in bidentate, [1 + 1] or monodentate fashion. Finally, [Ag(bpt)]BF4 is a polymer of square planar silver ions linked by bis-bidentate bpt ligands. Most of the tpt and bpt structures include short anionπ contacts to the ligand triazinyl rings. Electrospray mass spectra confirm the oligomeric nature of the Ag/tpym and tpt complexes in MeNO2 solution.

A new triazine bearing a pyrazolone group capable of copper, nickel, and zinc chelation

Interest in inorganic applications of triazines is growing. In this report, metal complexes of copper(ii), nickel(ii), and zinc(ii) and a novel class of chelates composed of a triazine ring substituted with a hydrazine group and pyrazolone are evaluated using spectrophotometric methods, single crystal X-ray diffractometry, and electrochemistry. Complexes with copper(ii) include a single chelate and chloride ion(s)/water to satisfy a trigonal bipyramidal coordination sphere. The nickel(ii) and zinc(ii) complexes are composed of two chelating groups that adopt an octahedral geometry around the metal ion. Irreversible redox activity was observed with the copper(ii) complex but no redox activity was observed with the ligand alone or zinc(ii) and nickel(ii) complexes. Use of the coumarin carboxylic acid assay shows that the ligand motif is capable of preventing redox cycling of copper in biological conditions and could thus serve as an antioxidant preventative agent. Cellular toxicity studies show that the new triazine molecule could have therapeutic applications in the μM concentration range based on the measured EC₅₀ = 1.183 ± 0.002 mM. Altogether this work shows that by merging triazine chemistry into inorganic compounds, there is potential to explore a range applications thanks to the new architecture.

A new triazine bearing a pyrazolone moiety and metalation with first row transition metals, copper(ii), nickel(ii), and zinc(ii) is explored.

A Co(ii) 1D coordination polymer constructed from 1,3-bisbenzyl-2-oxoimidazoline-4,5-dicarboxylic acid: crystal structure and magnetic properties

A new complex involving 1,3-bisbenzyl-2-oxoimidazoline-4,5-dicarboxylic acid (H₂L) and a cobalt(ii) metal ion designated [Co(L)(H₂O)₂]_n has been synthesized under solvothermal conditions and characterized.

Geometry variation in porous covalent triazine polymer (CTP) for CO2 adsorption

Covalent triazine-based organic polymers (CTPs), a sub class of covalent organic polymers (COPs), are promising materials for CO₂ adsorption although the impact of their dimensionality on the trapping process is not well-understood.

Iron(II) Complexes of 2,4-Dipyrazolyl-1,3,5-triazine Derivatives-The Influence of Ligand Geometry on Metal Ion Spin State

Seven [FeL₂][BF₄]₂ complex salts were prepared, where L is a 6-substituted 2,4-di(pyrazol-1-yl)-1,3,5-triazine (bpt) derivative. The complexes are all crystallographically high-spin, and exhibit significant distortions from an ideal D_2d-symmetric coordination geometry. In one case, an unusual type of metal ion disorder was observed among a cubic array of ligands in the crystal lattice. The complexes are also high-spin between 3 and 300 K in the solid state and, where measured, between 239 and 333 K in CD₃CN solution. This result is unexpected, since homoleptic iron(II) complexes of related 2,6-di(pyrazol-1-yl)pyridine, 2,6-di(pyrazol-1-yl)pyrazine, and 2,6-di(pyrazol-1-yl)pyrimidine derivatives often exhibit thermal spin-crossover behavior. Gas-phase density functional theory calculations confirm the high-spin form of [Fe(bpt)₂]²⁺ and its derivatives is stabilized relative to iron(II) complexes of the other ligand types. This reflects a weaker Fe/pyrazolyl σ-bonding interaction, which we attribute to a small narrowing of the chelate ligand bite angle associated with the geometry of the 1,3,5-triazinyl ring. Hence, the high-spin state of [Fe(bpt)₂]²⁺ centers does not reflect the electronic properties of its heterocyclic ligand donors but is imposed by the bpt ligand conformation. A high-spin homoleptic iron(III) complex of one of the bpt derivatives was also synthesized.

Crystal structures and photocatalytic properties of two novel iodoplumbate hybrids templated by multivalent organic cations

Two novel multivalent organic cation-templated iodoplumbate hybrids with trinuclear or 1D anionic structures and good photocatalytic performances are reported.