Diacetic Acid Research Articles

A comparative study on PVC based sensors in determination of.

The proposed work described the synthesis of neutral ionophores; 4,8-diaza-3,3,10,10-tetramethyl-1,2-dithiacyclodecane (S1), 5,8-diaza-3,3,10,10-tetramethyl-1,2 dithiacyclodecane-N,N''-diacetic acid (S2) and N,N''-bis(2,2-dimethyl-2-mercaptoethyl)ethylenediamine-N,N-diacetic acid (S3) used for comparative analysis in determination of molybdenum(v) as PVC-based membrane sensors. The best result was obtained with sensor no. 7 based on S3 ionophore with membrane composition (w/w, mg%); 5.0(S) : 30.0(PVC) : 5.0(KTpClPB) : 60.0(o-NPOE) showing a working range of 2.3 × 10-7-1.0 × 10-2 M with a detection limit of 1.2 × 10-7 M and a toleration of non-aqueous media up to 15% with slope of 11.7 mV/decade of activity. The sensor no. 7 can also be used to assess the Mo(v) concentration in different natural samples (water bodies, soils, root nodules and urine samples) with comparative analysis of ETAAS and spectrophotometric methods. The proposed sensor no. 7 can be used 2.5 months without any distortion in results after that leaching of ionophore was observed from the membrane phase in aqueous solutions of Mo(v). The proposed sensor has shown a good dynamic response time of 11 s.

Peculiar structural findings in coordination chemistry of malonamide–N,N′-diacetic acid

Unprecedented structural features are found in the coordination chemistry of malonamide–N,N′-diacetic acid. A type of supramolecular interaction involving non-aromatic rings—metallorings—designated as Metal Organic Ring interaction (MORi) is crystallographically well established.

The Effect and Counter-Effect of Impurities on Crystallization of an Agrochemical Active Ingredient: Stereochemical Rationalization and Nanoscale Crystal Growth Visualization

The molecular mechanisms underpinning the effects of impurities (reaction byproduct) on the crystallization of N-phosphonomethyl glycine (PMG), a common herbicide, are presented. The impurities, iminobismethylene phosphonic acid (IMPA) and amino methyl phosphonic acid (AMPA), were incorporated into PMG crystals by selectively adsorbing onto the (100) face, and subsequently, caused major reduction in the growth rate of this face of the crystal. In contrast, the impurity N-phosphonomethyl imino diacetic acid (PIDA), with a lower binding affinity to PMG crystals, did not affect the crystal habit significantly. These experimental results are rationalized based on stereospecific interaction of the impurities with the PMG crystal and binding energy calculations. Interestingly, when PIDA is present along with IMPA or AMPA in the crystallizing solution, it produced a beneficial effect by counteracting the habit-modifying effects of the other two impurities. In situ monitoring of crystal growth from pure and impur...

Coordination chemistry of the heterotopic 1,2-phenylenebis(thio)diacetic acid ligand: Rhodium(I), palladium(II) and nickel(II) complexes

Starting from the heterotopic multidentate ligand 1,2-phenylenebis(thio)diacetic acid (1), cis-rac-[PdCl2{1,2-(HOOCCH2S)2C6H4-κ2S,S′}] (2), cis-rac-[Rh{1,2-(HOOCCH2S)2C6H4-κ2S,S′}(cod)]BF4 (3) and cis-rac-[Ni{1,2-(OOCCH2S)2C6H4-κ4O,O′S,S′}{cis-(C3H4N2)}2] (4) were prepared and characterised by X-ray diffraction and conventional spectroscopic techniques. Compounds 1–4 show extensive hydrogen-bonded networks (XH⋯O, X=O, N) in the solid state.

Platinum-(diphenylamino styryl benzylazanediyl) diacetic acid derivatives nanocomposites: Synthesis and catalytic applications

Pt-(diphenylamino styryl benzylazanediyl) diacetic acid derivatives nanocomposites were synthesized via the alcohol reduction method and used as catalysts for hydrogenation of benzaldehydes including benzaldehyde, 3-phenoxybenzaldehyde, 4-hydroxybenzaldehyde, 4-anisaldehyde, and 4-dimethylaminobenzaldehyde. The nanocomposites characterized by UV-Vis, XRD and TEM have mean sizes of platinum cores from 1.8 to 2.9 nm. The size depends on the molar ratio of platinum and the organic compound in the nanocomposites. The Pt nanocomposites are stable not only in the colloidal solution but also during the catalytic hydrogenation process. The results of the catalytic hydrogenation of benzaldehyde derivatives demonstrate that the catalytic activity of the nanocomposites is much higher than that of Pt nanoparticles stabilized by Frechet-type dendrimers under the same reaction conditions. High activity of the catalysts may be attributed to the relatively open dendritic shell of the nanocomposite, which provides large tunnels for the substrates moving from the surface to the active sites.

Synthesis, Crystal Structure, and Characterization of a New Zinc Complex with Flexible Ligand (4-Amino-1,2,4-triazole-3,5-diyldithio)diacetic Acid and 4,4′-Bipyridine

A new zinc coordination polymer, [Zn(atda)(4,4′-bipy)]n (H2atda = (4-amino-1,2,4-triazole-3,5-diyldithio)diacetic acid, 4,4′-bipy = 4,4′-bipyridine), was synthesized by rheological phase reaction method and characterized by elemental analysis, IR, UV and single-crystal X-ray diffraction. The results reveal that it possesses three-dimensional (3D) solid-state structure. The Zn(II) inos are interlinked by bridging of atda2 ligands and 1D [Zn(atda)]n double chains are constructed, which are further connected together by the coordination of 4,4′-bipy molecules and 2D double layered structure are generated. Hydrogen-bonding interaction exists between the layers, resulting in the formation of 3D supramolecular structure. In addition, thermal stability and fluorescent property were studied.

Synthesis and biodistribution of a novel 99mTc complex of HYNIC-conjugated metronidazole as a potential tumor hypoxia imaging agent

A conjugate of 6-hydrazinopyridine-3-carboxylic acid (HYNIC) with the amino analogue of metronidazole (MN) was synthesized through a multiple-step reaction. HYNIC-MN could be labeled easily and efficiently with 99mTc using N-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine (tricine) and ethylenediamine -N,N′-diacetic acid (EDDA) as coligands to form the 99mTc–HYNIC–MN complex in high yield (>95%). Its partition coefficient indicated that it was a good hydrophilic complex. The tumor cell experiment showed that the 99mTc–HYNIC–MN complex had a certain hypoxic selectivity. The biodistribution studies of 99mTc–HYNIC–MN in Kunming mice bearing S180 tumor showed a favorable tissue distribution profile with high tumor uptake, and low or negligible accumulation in non-target organs, suggesting 99mTc–HYNIC–MN would be a novel potential tumor hypoxia imaging agent.

Determination of Solvatochromic Regression Coefficients for the Molybdenum(VI) Complex with Ethylenediamine‐N,N′‐diacetic Acid by Using Kamlet‐Abboud‐Taft Equation

AbstractThe Solver, Microsoft Excel 2000 powerful optimization package, has been used to perform non‐linear least‐squares curve fitting on the basis of Gauss‐Newton method for the calculation of solvatochromic regression coefficients for the complexation of molybdenum(VI) with ethylenediamine‐N,N′‐diacetic acid and dissociation constants at 25°C and constant ionic strength 0.1 mol·L−1 sodium perchlorate in different aqueous solutions of methanol. A combination of potentiometric and UV spectrophotometric methods have been used for experimental studies. Non specific and specific solute‐solvent interactions were interpreted by correlating the equilibrium data with solvent parameters using the Kamlet‐Abboud‐Taft solvatochromic equation. Finally the influence of the solvent on the stability of the complex was discussed on the basis of the correlation results and the contribution of α (hydrogen‐bond donor acidity), β (hydrogen‐bond acceptor basicity) and π* (dipolarity/polarizability) parameters.

Synthesis, radiochemical and biological characteristics of 99mTc-8-hydroxy-7-substituted quinoline complex: a novel agent for infection imaging

2,2′-[(8-hydroxyquinolin-7-yl)methylazanediyl]diacetic acid (HQMADA) was synthesized via reaction of 8-hydroxyquinoline with iminodiacetic acid in presence of paraformaldehyde with a yield of 27%. The obtained compound was well characterized via different analytical techniques. Labeling of the synthesized compound with technetium-99m in pertechnetate form (99mTcO4−) in the presence of stannous chloride dihydrate was carried out via chelation reaction. The reaction parameters that affect the labeling yield such as HQMADA concentration, stannous chloride dihydrate concentration, pH of the reaction mixture, and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of 99mTc-HQMADA complex (91.9%) was obtained by using 1.5 mg HQMADA, 50 μg SnCl2·2H2O, pH 8 and 30 min reaction time. Biodistribution studies in mice were carried out in experimentally induced infection in the left thigh using E. coli. 99mTc-HQMADA complex showed higher uptake (T/NT = 5.5 ± 0.3) in the infectious lesion than the commercially available 99mTc-ciprofloxacin (T/NT = 3.8 ± 0.8). Biodistribution studies for 99mTc-HQMADA complex in Albino mice bearing septic and aseptic inflammation models showed that 99mTc-HQMADA complex able to differentiate between septic and aseptic inflammation.

Cell-Trappable Quinoline-Derivatized Fluoresceins for Selective and Reversible Biological Zn(II) Detection

The synthesis and spectroscopic characterization of two new, cell-trappable fluorescent probes for Zn(II) are presented. These probes, 2-(4,5-bis(((6-(2-ethoxy-2-oxoethoxy)quinolin-8-yl)amino)methyl)-6-hydroxy-3-oxo-3H-8 xanthen-9-yl)benzoic acid (QZ2E) and 2,2'-((8,8'-(((9-(2-carboxyphenyl)-6-hydroxy-3-oxo-3H-xanthene-4,5-diyl)bis(methylene))bis(azanediyl))bis(quinoline-8,6-diyl))bis(oxy))diacetic acid (QZ2A), are poorly emissive in the off-state but exhibit dramatic increases in fluorescence upon Zn(II) binding (120 ± 10-fold for QZ2E, 30 ± 7-fold for QZ2A). This binding is selective for Zn(II) over other biologically relevant metal cations, toxic heavy metals, and most first-row transition metals and is of appropriate affinity (K(d1)(QZ2E) = 150 ± 100 μM, K(d2)(QZ2E) = 3.5 ± 0.1 mM, K(d1)(QZ2A) = 220 ± 30 μM, K(d2)(QZ2A) = 160 ± 80 μM, K(d3)(QZ2A) = 9 ± 6 μM) to reversibly bind Zn(II) at physiological levels. In live cells, QZ2E localizes to the Gogli apparatus where it can detect Zn(II). It is cell-membrane-permeable until cleavage of its ester groups by intracellular esterases produces QZ2A, a negatively charged acid form that cannot cross the cell membrane.

The Cholecystokin Provocation HIDA Test: Recreation of Symptoms is Superior to Ejection Fraction in Predicting Medium-Term Outcomes

BackgroundThe 99m technetium labelled hepato imino diacetic acid (HIDA) scan is widely used in the investigation of patients with typical biliary pain but whose trans-abdominal ultrasound scan (US) is normal. Although the standard measure by which the HIDA scan is deemed positive is the presence of an ejection fraction (EF) of <35% following provocation with cholecystokinin (CCK), there still remains debate as to the usefulness of this measure. The aim of this study was to compare the roles of EF and symptom provocation following CCK infusion in relation to the outcome following laparoscopic cholecystectomy (LC). More specifically, we aimed to review the resolution of symptoms for our significant population of patients with normal HIDA scan EFs for whom surgery has traditionally been deemed inappropriate. Patients and MethodsAll patients undergoing LC for a presumed diagnosis of biliary dyskinesia were identified from a prospectively maintained database. Data were collected regarding pre-operative symptoms, EF and symptom provocation during the CCK HIDA scan, histological findings, early symptomatic outcome, and medium-term follow-up. ResultsDuring the period from March 2006 to October 2009, 42 patients with biliary symptoms but a negative US were referred for assessment by a single surgeon. There were 31 women and 11 men with a mean age of 39.0±12.6 years. All underwent a CCK HIDA scan of which 17 were positive with an EF <35% and the remaining 25 were negative. All patients reported recreation of symptoms following administration of CCK. All gallbladders were delivered intact for histological assessment and all but one showed evidence of chronic cholecystitis. At each postoperative visit, approximately 2 weeks following the procedure, all patients reported resolution of symptoms. After a mean of 18.7±12.1 months symptom recurrence had been noted in only one of 42 (2.4%). ConclusionsThe CCK HIDA scan is a useful study in the investigation of acalcalous cholecystitis; however, we would suggest that recreation of symptoms following CCK provocation is superior to EF for the identification of underlying chronic cholecystitis. Indeed, a normal gallbladder ejection fraction does not necessarily rule out a biliary aetiology of symptoms for this patient population.

Simulation of micellar enhanced ultrafiltration by multiple solute model

Multiple solute ultrafiltration models in micellar enhanced ultra filtration (MEUF) have been studied, for experimental results of selective separation of Cu (II) and Co (II) with anionic surfactant, sodium dodecyl sulfate (SDS) and imino diacetic acid (IDA) as chelating agent using synthetic waste water. This model is based on mass balance analysis coupled with the filtration theory, resistance-in-series model and gel polarization model. This model is characterized by the parameters, membrane resistance Rm, membrane permeability Pm, back transport coefficient Kb, Kbi and mass transfer coefficient ki. These parameters are estimated by using the Levenberg–Marquardt method coupled with the Gauss–Newton algorithm.Due to cross currents caused by the superficial velocity, some solutes are removed from the membrane surface and go into the bulk known as back transport effect. Hence back transport coefficient plays significant role in explaining the extent of micellization. The simulation results show a good agreement with the experimental data of permeate quality and flux. The consideration of negligible gel thickness is suitable for dilute solutions.

ChemInform Abstract: Structure of the Product Obtained by Methylphosphorylation of Ethylenediamine-N,N′-diacetic Acid.

ChemInform Abstract: Structure of the Product Obtained by Methylphosphorylation of Ethylenediamine-N,N′-diacetic Acid.

Coordination polymers and hydrogen-bonded assemblies of 2,2′-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid with ammonium, lanthanum and zinc cations

We report the synthesis of the 2,2'-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid (TALH(4)) ligand and the structures of its adducts with ammonium, namely diammonium 2,2'-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetate, 2NH(4)(+).C(14)H(12)O(10)(2-), (I), lanthanum, namely poly[[aquabis[mu(4)-2,2'-(2-carboxylatomethyl-5-carboxymethyl-1,4-phenylenedioxy)diacetato]dilanthanum(III)] monohydrate], {[La(2)(C(14)H(11)O(10))(2)(H(2)O)].H(2)O}(n), (II), and zinc cations, namely poly[[{mu(4)-2,2'-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}zinc(II)] trihydrate], {[Zn(C(14)H(12)O(10))].3H(2)O}(n), (III), and poly[[diaqua(mu(2)-4,4'-bipyridyl){mu(4)-2,2'-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}dizinc(II)] dihydrate], {[Zn(2)(C(14)H(10)O(10))(C(10)H(8)N(2))(H(2)O)(2)].2H(2)O}(n), (IV), the formation of all four being associated with deprotonation of TALH(4). Adduct (I) is a diammonium salt of TALH(2)(2-), with the ions located on centres of crystallographic inversion. Its crystal structure reveals a three-dimensional hydrogen-bonded assembly of the component species. Reaction of TALH(4) with lanthanum trinitrate hexahydrate yielded a two-dimensional double-layer coordination polymer, (II), in which the La(III) cations are nine-coordinate. With zinc dinitrate hexahydrate, TALH(4) forms 1:1 two-dimensional coordination polymers, in which every Zn(II) cation is linked to four neighbouring TALH(2)(2-) anions and each unit of the organic ligand is coordinated to four different tetrahedral Zn(II) cation connectors. The crystal structure of this compound accommodates molecules of disordered water at the interface between adjacent polymeric layers to give (III), and it has been determined with low precision. Another polymer assembly, (IV), was obtained when zinc dinitrate hexahydrate was reacted with TALH(4) in the presence of an additional 4,4'-bipyridyl ligand. In the crystal structure of (IV), the bipyridyl and TAL(4-) entities are located on two different inversion centres. The ternary coordination polymers form layered arrays with corrugated surfaces, with the Zn(II) cation connectors revealing a tetrahedral coordination environment. The two-dimensional polymers in (II)-(IV) are interconnected with each other by hydrogen bonds involving the metal-coordinated and noncoordinated molecules of water. TALH(4) is doubly deprotonated, TALH(2)(2-), in (I) and (III), triply deprotonated, viz. TALH(3-), in (II), and quadruply deprotonated, viz. TAL(4-), in (IV). This report provides the first structural characterization of TALH(4) (in deprotonated form) and its various supramolecular adducts. It also confirms the potential utility of this tetraacid ligand in the formulation of coordination polymers with metal cations.

Comparison of 68Ga-siderophores for imaging Aspergillus fumigatus infections with PET

NH2 where NO2A=,4,7-triazacyclononane-1,4,-diacetic acid and X=Paraaminobenzoic acid, 6-aminohexanoic acid, 8-aminooctanoic acid and 9nonanoic acid. All of the new conjugates were radiolabeled and purified by reverse-phase high-performance liquid chromatography. Complete and full characterization of Cu-BBN conjugates was done using electrospray-ionization mass spectrometry. Competitive displacement binding assays indicated that all of the conjugates exhibited IC50s in the nM range in human, prostate PC-3 cells. Biodistribution studies using these new conjugates in rodents bearing PC-3 xenografted tumors indicated rapid clearance of targeting vector from blood with high uptake and retention in tumors. Molecular imaging studies in rodents produced high-contrast, high-quality micro-positron emission tomography images with very high tumor-to-background ratios. doi:10.1016/j.nucmedbio.2010.02.012

{2-[2-(Carboxymethoxy)phenoxy]acetato}[2,2′-(o-phenylenedioxy)diacetic acid]sodium 4,4′-bipyridine hemisolvate monohydrate

In the title compound, [Na(C10H9O6)(C10H10O6)]·0.5C10H8N2·H2O, the Na atom is eight-coordinated in an distorted dicapped-octa­hedral geometry by eight O atoms from a 2-(2-carb­oxy­meth­oxy­phen­oxy)acetate (o-BDOAH) anion and a 2,2′-(o-phenyl­enedi­oxy)diacetic acid (o-BDOAH2) mol­ecule. The uncoordinated 4,4′-bipyridine mol­ecule is arranged around an inversion center and exhibits rotational disorder. A three-dimensional supra­molecular network is built up in the crystal through O—H⋯O and O—H⋯N hydrogen bonds between the uncoordinated water mol­ecule, the uncoordinated 4,4′-bipyridine mol­ecule and the sodium complex mol­ecule.

Efficient Methanolytic Cleavage of Phosphate, Phosphonate, and Phosphonothioate Esters Promoted by Solid Supported Lanthanide Ions

The methanolyses of three neutral organophosphorus esters, namely paraoxon (O,O-diethyl O-p-nitrophenyl phosphate (12), O-ethyl O-p-nitrophenyl methylphosphonate (13), O-ethyl S-3,5-dichlorophenyl methylphosphonothioate (14, a model for VX), and an anionic phosphonate ester, O-hydrogen S-3,5-dichlorophenyl methylphosphonothioate (15, a model for a toxic hydrolytic decomposition product of VX known as EA2192)), promoted by solid supported lanthanide ion catalysts (La3+, Sm3+, Eu3+, Yb3+) were investigated at 25 °C under sspH controlled conditions in methanol. The supports were derived from commercially available chlorobenzylated silica and chloromethylated polystyrene functionalized with two chelating ligands, iminodiacetic acid (IDA) and ethylenediamine-N,N′-diacetic acid (EDDA), followed by exposure to Ln3+ ions. The catalysts showed good activity at two investigated sspH values of 8.8 and 11 (in methanol). Despite the fact that the methoxide promoted reactions for the four substrates span a range of ∼20...

Nanodomain Formation in Lipid Membranes Probed by Time-Resolved Fluorescence

Time-resolved fluorescence measurements on liposomes prepared with 1 mol % pyrene-labeled lipids (PLLs) with a headgroup bearing either an alcohol (PSOH) or an imido diacetic acid (PSIDA) and 99 mol % 1-palmitoyl-2-oleyl-3-sn-phosphatidylcholines (POPC) or 99 mol % distearylphosphatidylcholine (DSPC) were performed to investigate how lipids phase separate within the membrane bilayer. Global analysis of the fluorescence decays with the fluorescence blob model (FBM) led to the conclusion that the PLLs were homogeneously distributed on the surface of POPC vesicles while the PLLs phase-separated in the DSPC vesicles. The analysis yielded the fraction of aggregated pyrenes, f(agg). The large f(agg) values found for PSIDA suggest that the imido diacetic acid headgroup of PSIDA induces self-aggregation and phase separation in both membranes. The addition of external cations such as Cu(2+) and La(3+) was shown to hinder diffusional encounters between PSIDAs. The cations seem to target preferentially unassociated PSIDAs rather than aggregated PSIDA clusters. Accounting for the quenching of pyrene by Cu(2+) enables one to use PSIDA to probe the microviscosity of the lipid membrane. Using this effect, the environment of PSIDA in the DSPC membrane was found to be about 6 times more viscous than that in the POPC membrane. This difference is attributed to the difference in viscosity of the fluid POPC membrane and the gel-like DSPC membranes.

EFFICACY OF HJB/FE3+ TO PROVIDE FE TO NECTARINE PLANTS IN CALCAREOUS SOILS

Iron (Fe) chlorosis is a widespread problem in fruit crops grown on calcareous soils. To date, the application of synthetic Fe chelates is the most effective solution to correct this problem. The aim of this work was to study the effectiveness of a new synthetic Fe chelate, HJB (N,N'-Bis(2-hydroxy-5-methylbenzyl) ethylenediamine-N,N'-diacetic acid), in providing Fe to nectarine trees grown under alkaline field conditions. HJB has a similar structure as o,oEDDHA but its synthesis may produce purer commercial products than the EDDHA process that produces o,oEDDHA combined with a mixture of regioisomers (o,pEDDHA and p,pEDDHA) and other unknown by-products. The experiment started in 2007. Nine-year-old nectarine cultivar 'Zephyr' trees (Prunus persica L. Batsch) grafted in GF677 rootstocks were used. Two treatments with two different doses (0.45 g Fe-chelate/tree and 0.90 g Fe-chelate/tree) were evaluated: a commercial EDDHA/Fe 3+ product (5.19% Fe chelated by o,oEDDHA), HJB/Fe 3+ (7.97% Fe chelated by HJB) and an untreated (-Fe) control. The Fe compounds of the +Fe treatments were apportioned into three unequal doses that were directly injected into the soil three times during the growing season. SPAD index values were measured every two weeks and leaves were sampled 36, 58, and 91 days after the first application of the +Fe treatments. Yield, fruit weight, number of fruits per tree, and fruit diameter were also determined. In the first year, HJB/Fe 3+ and EDDHA/Fe 3+ improved SPAD values compared to the -Fe control; however, no significant differences were found with respect to leaf Fe concentration or fruit yield of the +Fe treated and -Fe control trees. Currently, a second year of experimentation is being developed.

Syntheses, crystal structures and magnetic properties of 1D and 2D cobaltous coordination polymers with mixed ligands

Two new Co(II) coordination polymers with mixed ligands, {[Co(BTA) 0.5(DBI) 2]·DBI·H 2O} n ( 1) and [Co(PDA)(DBI)(H 2O)] n ( 2) (H 4BTA = benzene-1,2,4,5-tetracarboxylic acid; H 2PDA = 2,2′-(1,2-phenylene)diacetic acid; DBI = 5,6-dimethyl-1 H-benzoimidazole) have been synthesized under hydrothermal conditions, respectively. Both of them are characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analysis, single-crystal X-ray diffraction, and magnetic susceptibilities. In 1, the Co(II) ions are four-coordinated and lie in distorted tetrahedron coordination environment. 1D ladder-like chain structure is formed by the bridging BTA 4− ligand. In 2, the Co(II) ions are in slightly distorted octahedral coordination geometry, and linked by PDA 2− ligand exhibiting a 2D layer structure. Temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed that there are antiferromagnetic interactions between Co(II) ions.