Self-assembly of a rare high spin FeII/PdII tetradecanuclear cubic cage constructed via the metalloligand approach

Polynuclear heterobimetallic coordination cages in which different metal cations are con-nected within a ligand scaffold are known to adopt a variety of polyhedral architectures, many of which display interesting functions. Within the extensive array of coordination cages incorporating Fe(II) centres reported so far, the majority contain low-spin (LS) Fe(II), with high-spin (HS) Fe(II) being less common. Herein, we present the synthesis and characterisation of a new tetradecanu-clear heterobimetallic [Fe8 Pd6 L8 ](BF4 ]28 (1) cubic cage utilising the metalloligand approach. Use of the tripodal tris-imidazolimine derivative (2) permitted the formation of the tripodal HS Fe(II) metalloligand [FeL](BF4)2·CH3 OH (3) that was subsequently used to form the coordination cage 1. Magnetic and structural analyses gave insight into the manner in which the HS environment of the metalloligand was transferred into the cage architecture along with the structural changes that accompanied its occupancy of the eight corners of the discrete cubic structure

Lanthanide mononuclear complexes with a tridentate Schiff base ligand : structures, spectroscopies and properties

A series of six lanthanide mononuclear complexes with a julolidine-quinoline based tridentate Schiff base ligand have been synthesized and structurally characterized. The complexes [NdL 2 (CH 3 OH)(NO 3 )]·CH 3 OH (1) and [LnL 2 (NO 3 )] [Ln = Eu (2), Gd (3), Dy (4), Ho (5), Lu (6)] {HL (C 22 H 21 N 3 O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} all have mononuclear structures with a metal to ligand ratio of 1:2. The Ln(III) ions are nine-fold coordinated by two tridentate Schiff base ligands and a bidentate nitrate anion except for complex 1 in which Nd(III) ion is ten-fold coordinated with an additional MeOH molecule. The coordination of a bidentate nitrate anion makes chirality to the complexes with equal enantiomers presence in the solid state. Lanthanide contraction has been observed with the average Ln–O/Ln–N bond lengths decreasing along the lanthanide series. Vibrational modes (2–5), electronic structures (1–3), thermal stability (2) and magnetic properties (3) have been further investigated and reported

Constructing coordination nanocages : the metalloligand approach

The focus on this mini-review is on the use of metalloligands for the construction of discrete self-assembled, polyhedral metallo-cages. This metalloligand approach employs metal bound multifunctional ligand building blocks that display predetermined, well-defined electronic and structural preferences that facilitate the rational design and construction of both homo- and heteronuclear cages. The assembled cages exhibit a variety of defined topologies that, for example, range from trigonal bipyramidal to rhombododecahedral

Dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI) complexes with a tridentate Schiff base ligand

The complexation of a julolidine–quinoline based tridentate ligand with three oxo-metal ions, dioxovanadium(V), oxo-rhenium(V) and dioxo-uranium(VI), has been investigated with four new complexes being synthesised and structurally characterised. (VO2L)•2/3H2O (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8- ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} has a VO2L neutral mononuclear structure with a five-fold coordinated vanadium metal centre in a distorted trigonal bipyramidal geometry. (ReOL2)2(ReCl6)•7DMF (2) [DMF = dimethylformamide] exhibits a mixed valent rhenium complex with a (ReOL2)+ cationic unit in a distorted octahedral metal coordination geometry, charge balanced with (ReCl6)2 ̅ anions. [(UO2)L(H2O)2]2•2(NO3)•HL•4H2O (3) and [(UO2)L(CH3OH)2](NO3)•CH3OH (4) both have (UO2L)+ cationic mononuclear structures with either coordinated water or methanol molecules in pentagonal bipyramidal coordination geometries for the uranium metal centres. Intra-/intermolecular interactions including hydrogen bonding and π–π interactions are common and have been discussed. In addition, optical absorption and photoluminescence properties have been investigated

Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)

The in situ Schiff base condensation of 2-acetylpyrazine with tris(2-aminoethyl)amine in the presence of zinc(II) perchlorate was carried out in absolute ethanol and 95 % ethanol, respectively. Two new tripodal metalloligands, 1 and 2, were isolated. The formation of complexes 1 and 2 has been verified by NMR, mass spectral studies and X-ray (for 2), with the evidence indicating that a zinc ion is incorporated in the tripodal cavity defined by the tren backbone in each case. However the products differed in the number of Schiff base condensation reactions that had occurred. While the use of absolute ethanol resulted in condensation at all three primary amine sites of tris(2-aminoethyl)amine, employing 95 % ethanol yielded condensation at only one of the primary amine sites. These different outcomes can be ascribed, at least in part, to the effect of the different water contents in the respective reaction solvents resulting in a shift of the dynamic equilibrium involving imine formation towards the precursor amine and ketone reagents. In 1, steric considerations dictate that the three uncoordinated pyrazine nitrogen donors will have their coordination vectors oriented in a mutually divergent manner suitable for coordination to three different metal centres when acting as a metalloligand while for 2, the X-ray structure confirms that the single uncoordinated (pendent) pyrazine nitrogen is also oriented for ready coordination to a second metal centre

Determination of Cu2+ in drinking water using a hydroxyjulolidine-dihydroperimidine colorimetric sensor

A new and highly efficient colorimetric Cu2+ chemosensor HL, synthesized by condensation between 8-hydroxyjulolidine-9-carboxaldehyde and 1,8-diaminonaphthalene, has been rationally designed and thoroughly studied. In a buffered aqueous methanol mixture, interactions between HL and Cu2+ produce an intense visible band at 421 nm, considerably red-shifted (~ 100 nm) from the peak maxima of HL (320 nm). Absorbance spectrophotometry experiments pointed to an exceptional 2.3 nM limit of detection (LoD) calculated from the ratiometric response upon Cu2+ binding. Furthermore, without the aid of instrumentation an impressive 0.5 µM LoD is possible by naked-eye observations, far below the 31.5 µM (2 mg/L) guidelines for drinking water established by the World Health Organization. Spectrophotometric pH titrations allowed the determination of the equilibrium constants and speciation plots for the formation of the various chemical species of HL in the absence and presence of Cu2+, with only mononuclear complexes being found. Additional studies highlighted the selectivity of HL to Cu2+ when in the presence of other metal ions, and a 1:1 (M:L) binding stoichiometry has also been confirmed with results from Cu2+ titrations, Job’s plot and ESI-HRMS in good agreement. The Cu2+ sensing mechanism was also found to be reversible by cycling with H2Na2EDTA

High-temperature spin crossover in FeIII N4O2 complexes incorporating an [R-sal2323] backbone

Of the multitude of [FeIII(R-sal2323)]X complexes reported in the literature, only four have demonstrated spin crossover (SCO). Herein, we report four additional examples of thermal spin crossover in [FeIII(R-sal2323)]X complexes (where R = Br, NEt2, and X = ClO4-, BF4-). Magnetic susceptibility measurements reveal gradual, high-temperature spin transitions in all four compounds with onsets near room temperature. To investigate the emergence of SCO behaviors being observed in these compounds, a range of intramolecular and intermolecular structural parameters were examined. The effect that ligand substituents may have on the electronic environment, as well as the effect of counterions and various intermolecular interactions on the crystal packing, were investigated and compared to the literature of [FeIII(R-sal2323)]X compounds for which magnetic measurements are reported. This comparison found that neither intramolecular subtleties nor intermolecular interactions have a large impact on whether or not these compounds are SCO active. Instead, it is shown and proposed that many compounds in the [FeIII(R-sal2323)]X family may demonstrate SCO activity if measured to higher temperatures (above 300 K). This would provide a wide range of FeIII compounds that are SCO active near or above room temperature to be explored in future work

Characterization of bismuth trioxide nanoparticles and evaluating binding affinity with proteins

Protein-nanoparticle conjugation, or protein-corona, is important for nanomedicine, nano diagnostic, and nano therapy applications. alpha-Bismuth oxide nanoparticles (alpha-Bi2O3 NPs) were prepared from bismuth nitrate powder using the sol-gel method and characterized using various techniques, including Energy Dispersive X-Ray Spectroscopy (EDS), X-ray Diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-VIS-NIR Spectroscopy, and Brunauer-Emmett-Teller (BET). X-ray diffraction studies revealed that NPs are in the alpha phase with a monoclinic structure. The energy band gap, average surface area and crystallite size are 2.81 eV, 2.42 m(2), and 15-106 nm, respectively. Transmission electron microscopy revealed particle size is 32.21 nm, with a d-spacing of 2.529 angstrom. The surface-tovolume ratio is calculated and found to be 2.553x10(6) m (-1). For the first time, a direct protein interaction with NPs was examined with standard proteins such as bovine serum albumin (BSA), carbonic anhydrase, phosphorylase b, and total human serum proteins and analyzed using mass spectroscopy. Proteomic analysis showed that proteins such as BSA, phosphorylase b, and carbonic anhydrase exhibited a strong affinity with Bi2O3 NPs. However, it was found that there was less or no association between Annexin A6, human serum albumin, Zinc finger protein, and Bestrophin-2 with Bi2O3 NPs