Water-soluble chiral coordination polymers of Li+, Na+, K+, and Ba2+ with an anionic iron(III) complex of a L-threonine derivative and a significant red shift of visible spectra with Al3+ salt

Four salts of an anionic iron(III) bis-complex, [Fe(LL-thr)2]1-, were synthesized from water or methanol. H2LL-thr is a tridentate ligand derived from the L-threonine amino acid, and the cations used are Li+ (1), Na+ (2), K+ (3), and Ba2+ (4). Single-crystal X-ray diffraction showed that all the complexes are coordination polymers of different dimensionalities. The iron(III) complex binds to cations through its coordinated phenolate and non-coordinated carboxylate oxygen atoms. While Li+ forms a linear chain, all others have a pair of bridged cations intervening the iron(III) complexes. The 3D network of Ba2+ salt has a sizeable solvent-accessible space occupied by aquated chloride ions. The differences in circular dichroism (CD) spectra and significantly lower conductance values in water and methanol support partial retention of the polymeric nature in methanol. The visible spectra of 4 in methanol or water showed an ∼10 nm shift of the charge transfer bands from 3. However, the addition of Al3+ salt to 2 showed a significant colour shift. Further investigation confirmed that the colour shift is due to partial protonation of the complex with protons generated from salt hydrolysis. Most reports on visual aluminium detection consider aluminium's binding as the shift's source. The present results show that protonation due to hydrolysis of aluminium salt can skew the observation.

Fluorimetric determination of aqueous formaldehyde employing heating and ultrasound-assisted approach through its derivatization with a ß-diketone-nickel(2+) complex immobilized in a PMMA flow cell

Formaldehyde (FA) is a highly toxic substance present in many matrices, including freshwater as well as found in natural mechanisms such as rainfall and combustion of organic matter. Consumption of water contaminated with high levels of FA can cause severe short-term or long-term health problems. Due to these health risks, procedures are necessary to determine and quantify FA in aqua sources This paper reports on a study of fluorimetric determination of FA using a nickel(2 + )-diketonate coordination compound immobilized as a solid precursor. The compound was characterized by electronic absorption, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetry (TG), optical microscopy (OM), and scanner electron microscopy (SEM). The methodology was based on the reaction of the synthesized compound with an ammoniacal buffer generating a selective reagent for formaldehyde: fluoral-P. The product of the reaction generates 3,5-diacetyl-1,4-dihydrolutidine (DDL), which is responsible for the fluorescence of the system. Several parameters such as temperature, duration of heating time, and dilution effect with the best effects were studied to carry out FA determination. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg/L FA (R = 0.997 and n = 10), and a detection (3σ criterion) and quantification (10 σ criterion) limit estimated at 0.129 and 0.389 mg/L, respectively were achieved. The FA analysis was able to be conducted in 05 min with a relative standard deviation estimated at 1.10 %.

The effect of solvent on one-dimensional cadmium coordination polymers

We transformed one one-dimensional coordination polymer directly to another by carrying out a dissolution–recrystallization structural transformation (DRST).

Metal-organic frameworks based on the [1,1':3',1''-terphenyl]-3,3'',5,5''-tetracarboxylic acid ligand: syntheses, structures and magnetic properties

The solvothermal reactions of [1,1':3',1''-terphenyl]-3,3'',5,5''-tetracarboxylic acid (H4TPTA) with transition metal cations afforded five novel coordination polymers in the presence of three pyridine ligands (4,4'-bipy = 4,4'-bipyridine, 2,2'-bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline), namely [M(TPTA)0.5(4,4'-bpy)0.5(H2O)2]n (M = Co for (1), Ni for (2)), {[Mn2(TPTA)(2,2'-bpy)H2O]·1.5H2O}n (3), and [M(H2TPTA)(phen)]n (M = Mn for (4), Co for (5)). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Polymers 1 and 2 are isomorphous and exhibit 3D 4-fold interpenetrated networks with the point Schläfli symbol of (4(2)·10(4)) (4·10(2)). Polymer 3 shows a 2D layer framework. Polymers 4 and 5 are also isomorphous and each displays a one-dimensional (1D) chain, which further forms a 2D supramolecular architecture via inter-chain π···π interactions. Moreover, variable-temperature magnetic susceptibilities of polymers 3-5 exhibit overall weak antiferromagnetic coupling between the adjacent M(II) ions.

Solvent-mediated assembly of chiral/achiral hydrophilic Ca(ii)-tetrafluoroterephthalate coordination frameworks: 3D chiral water aggregation, structural transformation and selective CO2 adsorption

Spontaneous reactions of Ca^II with a fluorinated carboxylate ligand afford chiral/achiral hydrophilic MOF materials.

catena-Poly[tris(μ3-acetylacetonato)nickelate(II)sodium(I)]

The title complex, [NaNi(C5H7O2)3]n, contains an anionic tris(acetylacetonato)nickelate(II) unit, [Ni(acac)3](-) (acac is acetylacetonate), with a highly regular octahedral coordination geometry. The Ni(II) cation lies on a Wyckoff a site, resulting in D3 symmetry of the anion. Charge balance is provided by sodium cations, which occupy Wyckoff type b sites. Each sodium cation is surrounded by two [Ni(acac)3](-) anions, each of which is connected to the alkali metal through three O atoms, in a fac configuration. This arrangement leads to the formation of linear [Na{Ni(acac)3}]n chains along the c axis. The Ni···Na distance is 2.9211 (10) Å. The title complex is one of the few examples of heterometallic systems based on alkali and transition metal cations bridged by acetylacetonate ligands.