Synthesis,crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd3+ and Tb3+) complexes with one-dimensional wave chain structure

Two isomorphic heterometallic 3d–4f cluster-based materials, formulated [Gd₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (1) and [Tb₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (2) (abbreviation: {Ln₈Cr₄}: Ln = Gd³⁺ (1); Tb³⁺ (2); HIN = isonicotinic acid), were achieved by hydro-/solvothermal method through using the ligand HIN. X-ray diffraction analysis illustrates eight lanthanide ions (Ln = Gd³⁺, Tb³⁺) and four transition-metal ions (Cr³⁺) of {Ln₈Cr₄} were constructed from two classical “drum-like” {Ln₄Cr₂} structures associated by organic ligands HIN, displaying a one-dimensional wave chain structure, which is rare. The magnetic properties of {Gd₈Cr₄} were inspected and showed the existence of antiferromagnetic coupling interactions between contiguous metal ions. On top of this, the magnetic entropy change of ΔS_m can attain 23.40 J kg⁻¹ K⁻¹ (44.90 mJ cm⁻³ K⁻¹) at about 3 K and ΔH = 7 T. Besides, fluorescence measurements of {Tb₈Cr₄} display typical characteristic Tb-based luminescence.

Two heterometallic cluster {Ln₈Cr₄} were constructed from two classical “drum-like” {Ln₄Cr₂} building units associated by organic ligands HIN, displaying 1D wave chain structure. The MCE values for {Gd₈Cr₄} at 3 K and 7 T is 23.40 J kg⁻¹ K⁻¹.     

Binuclear and tetranuclear Zn(ii) complexes with thiosemicarbazones: synthesis,X-ray crystal structures,ATP-sensing,DNA-binding,phosphatase activity and theoretical calculations

Two Zinc(ii) complexes [Zn₄(L¹)₄]·2H₂O (1) and [Zn₂(L²)₂]·2H₂O (2) of pyruvaldehydethiosemicarbazone ligands are reported. The complexes were characterized by elemental analysis, IR, NMR, UV-vis spectroscopy and by single-crystal X-ray crystallography. X-ray crystal structure determinations of the complexes show that though Zn : ligand stoichiometry is 1 : 1 in both the complexes, the molecular unit is tetranuclear for 1 and binuclear for 2. Both the complexes show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium in the presence of other anions like AcO⁻, NO₃⁻, F⁻, Cl⁻, H₂PO₄⁻, HPO₄²⁻ and P₂O₇²⁻. The UV-titration experiments of complexes 1 and 2 with ATP results in binding constants of 2.0(±0.07) × 10⁴ M⁻¹ and 7.1(±0.05) × 10³ M⁻¹ respectively. The calculated detection limits of 6.7 μM and 1.7 μM for 1 and 2 respectively suggest that the complexes are sensitive detectors of ATP. High selectivity of the complexes is confirmed by the addition of ATP in presence of an excess of other anions. DFT studies confirm that the ATP complexes are more favorable than those with the other inorganic phosphate anions, in agreement with the experimental results. Phosphatase like activity of both complexes is investigated spectrophotometrically using 4-nitrophenylphosphate (NPP) as a substrate, indicating the complexes possess significant phosphate ester hydrolytic efficiency. The kinetics for the hydrolysis of the substrate NPP was studied by the initial rate method at 25 °C. Michaelis–Menten derived kinetic parameters indicate that rate of hydrolysis of the P–O bond by complex 1 is much greater than that of complex 2, the k_cat values being 212(±5) and 38(±2) h⁻¹ respectively. The DNA binding studies of the complexes were investigated using electronic absorption spectroscopy and fluorescence quenching. The absorption spectral titrations of the complexes with DNA indicate that the CT-DNA binding affinity (K_b) of complex 1 (2.10(±0.07) × 10⁶ M⁻¹) is slightly greater than that of 2 (1.11(±0.04) × 10⁶ M⁻¹). From fluorescence spectra the apparent binding constant (K_app) values were calculated and they are found to be 5.41(±0.01) × 10⁵ M⁻¹ for 1 and 3.93(±0.02) × 10⁵ M⁻¹ for 2. The molecular dynamics simulation demonstrates that the Zn(ii) complex 1 is a good intercalator of DNA.

A binuclear and a tetranuclear zinc(ii) of pyruvaldehyde thiosemicarbazone show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH₃CN–H₂O (9 : 1) medium. The DNA binding and phosphatase activities of the complexes are also reported.     

A series of new polyoxometalate-based metal–organic complexes with different rigid pyridyl-bis(triazole) ligands: assembly,structures and electrochemical properties

Five new polyoxometalate (POM)-based metal–organic complexes (MOCs) with different rigid pyridyl-bis(triazole) ligands, namely, H{Co₂(Hpyttz-I)₂(H₂O)₆[CrMo₆(OH)₆O₁₈]}·8H₂O (1), {Co₂(H₂pyttz-I)₂(H₂O)₄[TeMo₆O₂₄]}[Co(H₂O)₆]·3H₂O (2), {Co₃(Hpyttz-II)₂(H₂O)₆[γ-Mo₈O₂₆]}·10H₂O (3), {Ni₃(Hpyttz-II)₂(H₂O)₆[γ-Mo₈O₂₆]}·10H₂O (4), {Ni₃(Hpyttz-III)₂(H₂O)₈[γ-Mo₈O₂₆]}·10H₂O (5) (H₂pyttz-I = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H₂pyttz-II = 3-(pyrid-3-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H₂pyttz -III = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a two-dimensional (2D) supramolecular network based on the binuclear complex unit: [Co₂(Hpyttz-I)₂(H₂O)₆ [CrMo₆(OH)₆O₁₈]]. Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex: {Co₂(H₂pyttz-I)₂(H₂O)₄[TeMo₆O₂₄]}²⁻, the discrete [Co(H₂O)₆]²⁺ units act as counter cations. Complexes 3 and 4 are isostructural with different center metals (M = Co or Ni), the adjacent γ-Mo₈O₂₆⁴⁻ anions are linked by the M^II ions to form a 1D M-γ-Mo₈O₂₆ inorganic chain. Then 1D M-γ-Mo₈O₂₆ inorganic chains are linked together by the 1D metal–organic M-(Hpyttz-II) chains to form a 3D framework. In complex 5, γ-Mo₈O₂₆⁴⁻ anions are bridged by the Ni^II ions to give a 1D Ni-γ-Mo₈O₂₆ inorganic chain, the adjacent 1D Ni-γ-Mo₈O₂₆ chains are connected through [Ni(Hpyttz-III)₂] units to form a 2D layer. The effect of POM type and coordination site of the ligands on the structures of the title complexes were discussed. The title complexes 1, 2 and 5 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid. In addition, the redox potentials of complexes 1, 2 and 5 are highly sensitive to pH and may be used as a kind of potential pH sensor.

Two novel Anderson-type and three octamolybdate (γ-Mo₈O₂₆) polyoxometalate-based metal–organic complexes were synthesized and structurally characterized. The electrochemical and bifunctional electrocatalytic behaviors of the title compounds have been investigated in detail.     

Carbazole-based bis-imidazole ligand-involved synthesis of inorganic–organic hybrid polyoxometalates as electrochemical sensors for detecting bromate and efficient catalysts for selective oxidation of thioether

Considering the potential application on preparing electrode and catalyst materials of inorganic–organic hybrid polyoxometalates, a bis-imidazole ligand with carbazole as a connector, 3,6-di(1H-imidazol-1-yl)-9H-carbazole (L), was used for preparing inorganic–organic hybrid polyoxometalates. As a result, three complexes formulated by [NiL₂(Mo₂O₇)] (1), [Cu(H₂O)₂(HL)₂ (β-Mo₈O₂₆)]·H₂O (2) and [Ni₂(H₂O)₄L₂ (CrMo₆(OH)₅O₁₉)]·6H₂O (3) were obtained successfully. Structural analysis indicated that the different polyoxoanions and metal ions showed important influences on the formation of structures. In the presence of Ni²⁺ ions and heptamolybdate, a 2D network constructed from Ni²⁺ ions and L ligands was formed in complex 1, in which the [Mo₄O₁₄]⁴⁻ polyoxoanions were encapsulated. But the use of Cu²⁺ ions led to a 1D chain of complex 2, which was composed of [β-Mo₈O₂₆]⁴⁻ polyoxoanions and mononuclear {CuL₂} units. By utilizing [CrMo₆(OH)₅O₁₉]⁴⁻ as the inorganic building block, complex 3 showed a 2D (4, 4)-connected layer. Complexes 1–3 could be employed as electrode materials for sensing bromate with the limits of detection of 0.315 μM for 1, 0.098 μM for 2 and 0.551 μM for 3. Moreover, these complexes showed efficient catalytic activity for the selective oxidation of thioethers.

Three inorganic–organic hybrid polyoxometalates were prepared using a bis-imidazole ligand featuring carbazole as a connector, exhibiting not only diverse structures, but also good electrochemical sensing activities for bromate, as well as efficient catalytic performances for oxidation of thioether.     

Facet-, composition- and wavelength-dependent photocatalysis of Ag2MoO4

Faceted β-Ag₂MoO₄ microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO). Both serve as solvents for the liquid-phase synthesis and surface-active agents for the formation of faceted microcrystals. Due to its reducing properties, truncated β-Ag₂MoO₄@Ag octahedra are obtained in DEG. The synthesis in DMSO allows avoiding the formation of elemental silver and results in β-Ag₂MoO₄ cubes and cuboctahedra. Due to its band gap of 3.2 eV, photocatalytic activation of β-Ag₂MoO₄ is only possible under UV-light. To enable β-Ag₂MoO₄ for absorption of visible light, silver-coated β-Ag₂MoO₄@Ag and Ag₂(Mo_0.95Cr_0.05)O₄ with partial substitution of [MoO₄]²⁻ by [CrO₄]²⁻ were prepared, too. The photocatalytic activity of all the faceted microcrystals (truncated octahedra, cubes, cuboctahedra) and compositions (β-Ag₂MoO₄, β-Ag₂MoO₄@Ag, β-Ag₂(Mo_0.95Cr_0.05)O₄) is compared with regard to the photocatalytic decomposition of rhodamine B and the influence of the respective faceting, composition and wavelength.

Faceted β-Ag₂MoO₄ microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO).     

Triangulo-{ErIII3} complex showing field supported slow magnetic relaxation

The triangulo-{Er₃} complex [Er₃Cl(o-van)₃(OH)₂(H₂O)₅]Cl₃·nH₂O (n = 9.4; H(o-van) = o-vanillin) (1) was generated by an in situ method. The isolated Er(iii) complex 1 was characterized by elemental analysis and molecular spectroscopy. The results of single crystal X-ray diffraction studies have shown that 1 is built up of trinuclear [Er₃Cl(o-van)₃(OH)₂(H₂O)₅]³⁺ complex cations, chloride anions and water solvate molecules. Within the complex cation the three Er(iii) central atoms are placed at the apexes of a triangle which are bridged by three (o-van)⁻ ligands with additional chelating functions and two μ₃-OH⁻ ligands. Additionally five aqua and one chlorido ligands complete the octa-coordination of the three Er(iii) atoms. AC susceptibility measurements reveal that the compound exhibits slow magnetic relaxation with two relaxation modes.

The triangulo-{Er₃} complex [Er₃Cl(o-van)₃(OH)₂(H₂O)₅]Cl₃·nH₂O (n = 9.4; H(o-van) = o-vanillin) (1) was generated by an in situ method.     

Synthesis,crystal structures and spectroscopic properties of pure YSb2O4Br and YSb2O4Cl as well as Eu3+- and Tb3+-doped samples

The quaternary halide-containing yttrium(iii) oxidoantimonates(iii) YSb₂O₄Cl and YSb₂O₄Br were synthesised through solid-state reactions from the binary components (Y₂O₃, Sb₂O₃ and YX₃, X = Cl and Br) at 750 °C in evacuated fused silica ampoules with eutectic mixtures of NaX and CsX (X = Cl and Br) as fluxing agents. YSb₂O₄Cl crystallizes tetragonally in the non-centrosymmetric space group P42₁2 with unit-cell parameters of a = 773.56(4) pm and c = 878.91(6) pm, whereas YSb₂O₄Br is monoclinic (space group: P2₁/c) with a = 896.54(6) pm, b = 780.23(5) pm, c = 779.61(5) pm and β = 91.398(3)°, both for Z = 4. The two new YSb₂O₄X compounds contain [YO₈]¹³⁻ polyhedra, which are connected via four common edges to form layers (d(Y³⁺–O²⁻) = 225–254 pm) without any Y³⁺⋯X⁻ bonds (d(Y³⁺⋯X⁻) > 400 pm). Moreover, all oxygen atoms belong to ψ¹-tetrahedral [SbO₃]³⁻ units, which are either connected to four-membered rings [Sb₄O₈]⁴⁻ in the chloride (Y₂[Sb₄O₈]Cl₂ for Z = 2) or endless chains in the bromide (Y_1/2(SbO₂)Br_1/2 for Z = 8) by common vertices. With distances of 307 pm in YSb₂O₄Cl and 326 pm in YSb₂O₄Br there are not even substantial bonding Sb³⁺⋯X⁻ (X = Cl and Br) interactions at work. Luminescence spectroscopy on samples doped with trivalent europium and terbium showed an energy transfer from the oxidoantimonate(iii) moieties as the sensitizer in the host structure onto the lanthanoid activators.

The oxygen atoms of the two new compounds belong to ψ₁-tetrahedral [SbO₃]³⁻ units, which are either vertex-connected to four-membered rings in YSb₂O₄Cl or to endless chains in YSb₂O₄Br. Eu³⁺- and Tb³⁺-doped samples show red or green luminescence.     

Synthesis and properties of a POM-based trinuclear copper(ii) triazole framework

A novel POM-based trinuclear copper(ii) triazole framework, namely, [H₂{Cu₆(trz)₆(μ₃-OH)₂}Mo₅O₁₈]·3H₂O (1) was isolated using a hydrothermal method, which displays a 3D network constructed from trinuclear copper(ii) units and triazole ligands with [Mo₅O₁₈]⁶⁻ anions as templates. 1 has been identified by single crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and FT-IR. Magnetic studies indicate that antiferromagnetic interactions exist in 1. In addition, 1 exhibits good Lewis acid catalytic activity for the synthesis of cyclohexanone ethylene ketal with 95% conversion. The HOMO–LUMO gap (E_g) of 1 is 2.34 eV calculated using the Kubelka–Munk equation (Fhν)^0.5, indicating that its forbidden bandwidth belongs to the semiconductor category. Visible-light photodegradation of RhB catalyzed by 1 was investigated, which shows high activity with an above 98% degradation rate.

A novel POMs-based trinuclear copper(ii) triazole framework, namely, {[H₂Cu₆(trz)₆(μ₃-OH)₂]} [Mo₅O₁₈]·3H₂O (1) was isolated by hydrothermal method, which displays remarkable Lewis acid catalytic activity and photocatalytic activity.     

Hexanuclear Cu3O–3Cu triazole-based units as novel core motifs for high nuclearity copper(ii) frameworks

The asymmetric 3,5-disubstituted 1,2,4-triazole ligand H₂V (5-amino-3-picolinamido-1,2,4-triazole) by reaction with an excess of Cu(ii) perchlorate (Cu : H₂V being 12 : 1) has produced a novel hexanuclear {Cu₆(μ₃-O/H)(HV/V)₃} fragment, with one triangular Cu₃(μ₃-O/H) group connected to three peripheral single Cu(ii) ions through a cis–cis–trans bridging mode of the ligand, which is the building block of the three structures described here: one hexanuclear, [Cu₆(μ₃-O)(HV)₃(ClO₄)₇(H₂O)₉]·8H₂O (1), one dodecanuclear, [Cu₁₂(μ₃-O)₂(V)₆(ClO₄)₅(H₂O)₁₈](ClO₄)₃·6H₂O (2), and one tetradecanuclear 1D-polymer, {[Cu₁₄(μ₃-OH)₂(V)₆(HV)(ClO₄)₁₁(H₂O)₂₀](ClO₄)₂·14H₂O}_n (3), the last two containing hexanuclear subunits linked by perchlorato bridges. The Cu–Cu av. intra-triangle distance is 3.352(2) Å and the Cu(central)–Cu(bridged external) av. distance is 5.338(3) Å. The magnetic properties of the hexanuclear “Cu₃O–3Cu” cluster have been studied, resulting as best fit parameters: g = 2.18(1), J(intra-triangle) = −247.0(1) cm⁻¹ and j(central Cu^II – external Cu^II) = −5.15(2) cm⁻¹.

The novel hexanuclear {Cu₆(μ₃-O/H)(HV/V)₃} fragment is the building block of the hexanuclear, the dodecanuclear and the tetradecanuclear-1D-polymeric structures described here.     

Tuning slow magnetic relaxation behaviour in a {Dy2}-based one-dimensional chain via crystal field perturbation

Two novel {Dy₂}-based one dimensional chain compounds {[Dy₂(H₃L)₄(OAc)₆]·2MeOH}_n (1) and {[Dy₂(H₃L)₄(OAc)₄(NCS)₂]·2MeOH}_n (2) (H₃L = 1,3-bis(2-hydroxynaphthalenemethyleneamino)-propan-2-ol) have been prepared under solvothermal conditions. Crystal structure analyses indicate that 1 and 2 feature similar 1D chain structures bearing dinuclear secondary building units. The difference between these two structures is that one chelated acetate ligand of Dy(iii) ion in 1 is replaced by one monodentate coordinated NCS⁻ ion in 2, leading to their different coordination numbers and geometry configurations to Dy(iii) ion. Magnetic properties indicate that 1 and 2 display slow magnetic relaxation behavior with an effective energy barrier of 16.44(2) K in 1 and 8.02(2) K in 2, respectively, which is maybe attributed to the subtle crystal field perturbation of Dy(iii) ions.

Two novel {Dy₂}-based one dimensional chain compounds with similar structures have been prepared and subtle crystal field of Dy(iii) ion can perturb their slow magnetic relaxation behaviors.     

Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters

We have structurally characterized a number of lithiated calix[4]arenes, where the bridge in the calix[4]arene is thia (–S–, L^SH₄), sulfinyl (–SO–, L^SOH₄), sulfonyl (–SO₂–, L^SO2H₄), dimethyleneoxa (–CH₂OCH₂–, L^COCH₄) or methylene (–CH₂–, LH₄). In the case of L^4SH₄, interaction with LiOtBu led to the isolation of the complex [Li₈(L^4S)₂(THF)₄]·5THF (1·5THF), whilst similar interaction of L^4SOH₄ led to the isolation of [Li₆(L^4SOH)₂(THF)₂]·5(THF) (2·5THF). Interestingly, the mixed sulfinyl/sulfonyl complexes [Li₈(calix[4]arene(SO)(SO₂)(SO_1.68)₂)₂(THF)₆]·8(THF) (3·8THF) and [Li₅Na(L^SO/3SO2H)₂(THF)₅]·7.5(THF) (4·7.5(THF) have also been characterized. Interaction of LiOtBu with L^SO2H₄ and L^COCH₄ afforded [Li₅L^4SO2(OH)(THF)₄]·2THF (5·2THF) and [Li₆(L^COC)₂(HOtBu)₂]·0.78THF·1.22hexane (6·0.78THF·1.22hexane), respectively. In the case of LH₄, reaction with LiOtBu in THF afforded a monoclinic polymorph [LH₂Li₂(thf)(OH₂)₂]·3THF (7·3THF) of a known triclinic form of the complex, whilst reaction of the de-butylated analogue of LH₄, namely de-BuLH₄, afforded a polymeric chain structure {[Li₅(de-BuL)(OH)(NCMe)₃]·2MeCN}_n (8·2MeCN). For comparative catalytic studies, the complex [Li₆(L^Pr)₂(H₂O)₂]·hexane (9 hexane), where L^Pr2H₂ = 1,3-di-n-propyloxycalix[4]areneH₂, was also prepared. The molecular crystal structures of 1–9 are reported, and their ability to act as catalysts for the ring opening (co-)/polymerization (ROP) of the cyclic esters ε-caprolactone, δ-valerolactone, and rac-lactide has been investigated. In most of the cases, complex 6 outperformed the other systems, allowing for higher conversions and/or greated polymer M_n.

Novel Li-calix[n]arene complexes (n = 3, 4) having (–S–), (–SO–), (–SO₂–), (–CH₂OCH₂–) or (–CH₂–) bridges have been synthesized and fully characterized. Their catalytic activity in the ring opening polymerization of lactones has been studied.     

Novel tetrahedral cobalt(ii) silanethiolates: structures and magnetism

Three heteroleptic complexes of Co(ii) tri-tert-butoxysilanethiolates have been synthesized with piperidine [Co{SSi(OtBu)₃}₂(ppd)₂] 1, piperazine [Co{SSi(OtBu)₃}₂(NH₃)]₂(μ-ppz)·2CH₃CN 2, and N-ethylimidazole [Co{SSi(OtBu)₃}₂(etim)₂] 3. The complexes have been characterized by a single-crystal X-ray, revealing their tetrahedral geometry on Co(ii) coordinated by two nitrogen and two sulfur atoms. Complexes 1 and 3 are mononuclear, whereas 2 is binuclear. The spectral properties and thermal properties of 1–3 complexes were established by FTIR spectroscopy for solid samples and TGA. The magnetic properties of complexes 1, 2, and 3 have been investigated by static magnetic measurements and X-band EPR spectroscopy. These studies have shown that 1 and 3, regardless of the similarity in structure of CoN₂S₂ cores, demonstrate different types of local magnetic anisotropy. Magnetic investigations of 2 reveal the presence of weak antiferromagnetic intra-molecular Co(ii)–Co(ii) interactions that are strongly influenced by the local magnetic anisotropy of individual Co(ii) ions.

Structural, spectral and thermal properties of three tetrahedral Co(ii) silanethiolates were established by XRD, FTIR for solid samples and TGA. The magnetic properties were investigated by static magnetic measurements and X-band EPR spectroscopy.     

Enhancing the quantum yield of singlet oxygen: photocatalytic degradation of mustard gas simulant 2-chloroethyl ethyl sulfide catalyzed by a hybrid of polyhydroxyl aluminum cations and porphyrin anions

By combining the anionic salt meso-tetra(4-carboxyphenyl)porphyrin (TCPP⁴⁻) and the Keggin polyoxometalate cation cluster [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺via a simple ion-exchange method, a hybrid (C₄₈H₂₆N₄O₈)[Al₁₃O₄(OH)₂₄(H₂O)₁₂]₂(OH)₁₀·18H₂O (Al₁₃–TCPP) was prepared and thoroughly characterized as a prototype of polyoxometalate–porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES). The experimental results showed that the catalytic degradation rate of CEES in the presence of Al₁₃–TCPP reached 96.16 and 99.01% in 180 and 90 min in methanol and methanol–water solvent mixture (v/v = 1 : 1), respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and solvent mixture were 39.8 min, −0.017 min⁻¹ and 14.7 min, −0.047 min⁻¹. Mechanism analysis indicated that under visible light irradiation in air, CEES was degraded through a combination of oxidation and alcoholysis/hydrolysis in methanol and the methanol–water solvent mixture. The superoxide radical (O₂˙⁻) and singlet molecular oxygen (¹O₂) generated by Al₁₃–TCPP selectively oxidized CEES into a non-toxic sulfoxide. The singlet oxygen capture experiments showed that Al₁₃–TCPP (Φ = 0.236) had a higher quantum yield of singlet oxygen generation than H₄TCPP (Φ = 0.135) under visible light irradiation in air. The material Al₁₃–TCPP has good reusability, and the degradation rate of CEES can still reach 98.37% after being recycled five times.

A hybrid Al₁₃–TCPP was thoroughly characterized as a prototype of polyoxometalate–porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES).     

A family of 3d metal clusters based on N–N single bonds bridged quasi-linear trinuclear cores: the Mn analogue displaying single-molecule magnet behavior

The reactions of the diacylhydrazine ligands N,N′-bisalicyl-2,6-pyridine dicarbohydrazide (H₆sphz) and N,N′-bis(3-methoxysalicyl)-2,6-pyridine dicarbohydrazide (H₆msphz) with various 3d metal salts, afforded a series of coordination clusters, namely, [Mn^III₂Mn^II(sphz)(acac)₂(CH₃OH)₄] (1, acac⁻ = acetylacetone anions), [Ni^II₃(msphz)(Py)₄] (2, Py = pyridine), [Cu^II₆(sphz)₂(Py)₄] (3) and [Cu^II₆(msphz)₂(Py)₄]·2DMF·2H₂O (4). Cluster 1 and 2 are single ligand assembled quasi-linear trinuclear structures. Both 3 and 4 consist a pair of quasi-linear {Cu₃} cores, which are linked together by two crossed ligands. The adjacent 3d metal ions in all trinuclear cores of 1–4 are bridged by N–N single bonds of ligands, which convey ferromagnetic (FM) interactions between 3d metal centers of 1, and antiferromagnetic (AFM) interactions between those of 2–4. In particular, the FM interactions and linear arrangement of mixed-valence Mn centers in 1 result in a large spin ground states value (S_T) of 13/2, as well as single-molecule magnet (SMM) behavior of slow relaxation and hysteresis of magnetization.

A family of 3d metal clusters featuring N–N single bonds bridged quasi-linear trinuclear cores were designed and synthesized. The Mn analogue represents a very rare case of quasi-linear 3d SMM using N–N single bonds as magnetic coupling pathways.     

Two zinc(ii) coordination polymers based on flexible co-ligands featuring assembly imparted sensing abilities for Cr2O72− and o-NP

Two new Zn(ii) coordination complexes, formulated as [Zn(opda)(pbib)] (1) and [Zn(ppda)(pbib)(H₂O)] (2), (H₂opda = 1,2-phenylenediacetic acid, H₂ppda = 1,4-phenylene-diacetic acid, pbib = 1,4-bis(1-imidazoly)benzene), have been synthesized. The opda ligands extend a 1D chain containing (Zn-pbib) polymer chains into a 2D layer in 1. In 2, the ppda ligands link Zn(ii) atoms to form a 2D network, then the rigid bis(imidazole) ligands give rise to the 3D structure. The fluorescence property application and mechanisms of two complexes for detecting Cr₂O₇²⁻ and o-NP have been researched. For two complexes, the high quenching percentage in low concentration aqueous solution are 95.75% (Cr₂O₇²⁻, 1), 95.28% (Cr₂O₇²⁻, 2) and 97.56% (o-NP, 1), 96.59% (o-NP, 2). Compared with 2, complex 1 has higher quenching percentage, this could be because 1 is a 3D supramolecular with a large hole. The detection limits have been measured to be 2.992 × 10⁻⁷ M (Cr₂O₇²⁻, 1), and 4.372 × 10⁻⁷ M (Cr₂O₇²⁻, 2), 2.103 × 10⁻⁷ M (o-NP, 1), 1.862 × 10⁻⁷ M (o-NP, 2), respectively. The emissions of two complexes could be effectively and selectively quenched by o-NP and Cr₂O₇²⁻, showing their potential as multi-responsive luminescent sensors.

Two zinc(ii) complexes exhibit the different architectures, and they have been shown to be excellent discriminative probe for the highly selective and sensitive detection of Cr₂O₇²⁻ and o-NP based on their sensitive fluorescence quenching.     

Structural diversity in the coordination compounds of cobalt,nickel and copper with N-alkylglycinates: crystallographic and ESR study in the solid state

Reactions of N-methylglycine (HMeGly), N-ethylglycine-hydrochloride (H₂EtGlyCl) and N-propylglycine-hydrochloride (H₂PrGlyCl) with cobalt(ii), nickel(ii) and copper(ii) ions in aqueous solutions resulted in ten new coordination compounds [Co(MeGly)₂(H₂O)₂] (1), [{Co(MeGly)₂}₂(μ-OH)₂]·2H₂O (1d), [Cu(MeGly)₂(H₂O)₂] (2α), [Co(EtGly)₂(H₂O)₂] (3), [Ni(EtGly)₂(H₂O)₂] (4), [Cu(μ-EtGly)₂]_n (5p), [Co(PrGly)₂(H₂O)₂] (6), [Ni(PrGly)₂(H₂O)₂] (7), and two polymorphs of [Cu(PrGly)₂(H₂O)₂] (8α and 8β). Compounds were characterized by single-crystal and powder X-ray diffraction, infrared spectroscopy, thermal analysis and X-band electron spin resonance (ESR) spectroscopy. These studies revealed a wide range of structural types including monomeric, dimeric and polymeric architectures, as well as different polymorphs. In all monomeric compounds, except 2α, and in the coordination polymer 5p hydrogen bonds interconnect the molecules into 2D layers with the alkyl chain pointing outward of the layer. In 2α and in the dimeric compound 1d hydrogen bonds link the molecules into 3D structures. 1d with cobalt(iii), and 4 and 7 with nickel(ii) are ESR silent. The ESR spectra of 1, 3 and 6 are characteristic for paramagnetic high-spin cobalt(ii). The ESR spectra of all copper(ii) coordination compounds show that the unpaired copper electron is located in the d_x²−y² orbital, being in agreement with the elongated octahedral geometry.

Interactions in copper, nickel and cobalt complexes with N-methyl-, N-ethyl- and N-propylglycinate: monomers, dimer and polymers.     

Syntheses,crystal structures,magnetic properties and ESI-MS studies of a series of trinuclear CuIIMIICuII compounds (M = Cu,Ni, Co,Fe, Mn,Zn)

Six trinuclear Cu^IIM^IICu^II compounds (M = Cu, Ni, Co, Fe, Mn, Zn) derived from the Schiff base ligand, H₂L (2 + 1 condensation product of salicylaldehyde and trans-1,2-diaminocyclohexane) are reported in this investigation. The composition of the metal complexes are [{Cu^IIL(ClO₄)}₂Cu^II(H₂O)]·2H₂O (1), [{Cu^IIL(ClO₄)}{Ni^II(H₂O)₂}{Cu^IIL}]ClO₄·CH₃COCH₃ (2), [{Cu^IIL(ClO₄)}{Co^II(CH₃COCH₃)(H₂O)}{Cu^IIL(CH₃COCH₃)}]ClO₄ (3) and isomorphic [{Cu^IIL(ClO₄)}₂M^II(CH₃OH)₂] (4, M = Fe; 5, M = Mn; 6, M = Zn). Two copper(ii) ions in 1–6 occupy N₂O₂ compartments of two L²⁻ ligands, while the second metal ion occupies the O(phenoxo)₄ site provided by the two ligands, i.e., the two metal ions in both Cu^IIM^II pairs are diphenoxo-bridged. Positive ESI-MS of 1–6 reveals some interesting features. Variable-temperature and variable-field magnetic studies reveal moderate or weak antiferromagnetic interactions in 1–6 with the following values of magnetic exchange integrals (H = −2JS₁S₂ type): J₁ = −136.50 cm⁻¹ and J = 0.00 for the Cu^IICu^IICu^II compound 1; J₁ = −22.16 cm⁻¹ and J = −1.97 cm⁻¹ for the Cu^IINi^IICu^II compound 2; J₁ = −14.78 cm⁻¹ and J = −1.86 cm⁻¹ for the Cu^IICo^IICu^II compound 3; J₁ = −6.35 cm⁻¹ and J = −1.17 cm⁻¹ for the Cu^IIFe^IICu^II compound 4; J₁ = −6.02 cm⁻¹ and J = −1.70 cm⁻¹ for the Cu^IIMn^IICu^II compound 5; J = −2.25 cm⁻¹ for the Cu^IIZn^IICu^II compound 6 (J is between two Cu^II in the N₂O₂ compartments; J₁ is between Cu^II and M^II through a diphenoxo bridge).

Six homo/heterotrinuclear Cu^IIM^IICu^II (M = Mn–Zn) compounds derived from salicylaldehyde-trans-1,2-diaminocyclohexane, which is a rarely utilized ligand, are reported.     

One-dimensional chain structures of hexanuclear uranium(iv) clusters bridged by formate ligands

Three one-dimensional chain structures of uranium(iv) hexanuclear clusters have been synthesized under hydrothermal/solvothermal conditions. Crystallographic studies disclose that the structures of [U₆O₄(OH)₄(HCOO)₁₂(H₂O)]·3H₂O (1a), [U₆O₄(OH)₄(HCOO)₁₂(HCOOH)(H₂O)]·3H₂O (1b) and (H₆C₅N)₂[U₆O₄(OH)₄(HCOO)₁₄(H₅C₅N)] (2) contain a U(iv) hexanulear core [U₆(μ₃-OH)₄(μ₃-O)₄]¹²⁺ which is decorated by terminal HCOO⁻ ligands and water (1a, 1b), HCOOH (1b) or pyridine molecules (2). These hexanuclear U(iv) clusters are further linked into zig–zag 1-D chain structures via bridging HCOO⁻ ligands. UV-vis-NIR spectra, together with bond valence calculations, indicate that all U atoms in three compounds exist as U(iv). Magnetic susceptibility data reveal that compound 2 exhibits paramagnetic characteristics.

Three one-dimensional chain structures of uranium(iv) hexanuclear clusters have been synthesized under hydrothermal/solvothermal conditions.     

Complexation and bonding studies on [Ru(NO)(H2O)5]3+ with nitrate ions by using density functional theory calculation

Complexation reactions of ruthenium–nitrosyl complexes in HNO₃ solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. The equilibrium structure of [Ru(NO)(NO₃)₃(H₂O)₂] obtained by DFT calculations reproduced the experimental Ru–ligand bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers for [Ru(NO)(NO₃)_x(H₂O)_5−x]^(3−x)+/− revealed that the complexation reactions of the ruthenium–nitrosyl complexes with NO₃⁻ proceed via the NO₃⁻ coordination to the equatorial plane toward the Ru–NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru–NO species in 6 M HNO₃ solution, such as in HLLW, by considering the association energy between the Ru–NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru–ligand coordination bonds depends on the stability of the Ru species and the Ru complex without NO₃⁻ at the axial position is more stable than that with NO₃⁻, which might be attributed to the difference in the trans influence between H₂O and NO₃⁻. Finally, we demonstrated the complexation kinetics in the reactions x = 1 → x = 2. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO₃ solution.

Density functional study on the complexation of [Ru(NO)(H₂O)₅]³⁺ with NO₃⁻ ions reproduced the stabilities of the geometrical isomers and the stepwise substitution reactivities by combining the association energy with the leaving/entering ligands.     

Molybdenum imidazole citrate and bipyridine homocitrate in different oxidation states – balance between coordinated α-hydroxy and α-alkoxy groups

Oxo and thiomolybdenum(iv/vi) imidazole hydrocitrates K₂{Mo^IV₃O₄(im)₃[Mo^VIO₃(Hcit)]₂}·3im·4H₂O (1), (Him)₂{Mo^IV₃SO₃(im)₃[Mo^VIO₃(Hcit)]₂}·im·6H₂O (2), molybdenum(v) bipyridine homocitrate trans-[(Mo^VO)₂O(H₂homocit)₂(bpy)₂]·4H₂O (3) and molybdenum(vi) citrate (Et₄N)[Mo^VIO₂Cl(H₂cit)]·H₂O (4) (H₄cit = citric acid, H₄homocit = homocitric acid, im = imidazole and bpy = 2,2′-bipyridine) with different oxidation states were prepared. 1 and 2 are the coupling products of [Mo^VIO₃(Hcit)]³⁻ anions and incomplete cubane units [Mo^IV₃O₄]⁴⁺ ([Mo^IV₃SO₃]⁴⁺) with monodentate imidazoles, respectively, where tridentate citrates coordinate with α-hydroxy, α-carboxy and β-carboxy groups, forming pentanuclear skeleton structures. The molybdenum atoms in 1 and 2 show unusual +4 and +6 valences based on charge balances, theoretical bond valence calculations and Mo XPS spectrum. The coordinated citrates in 1 and 2 are protonated with α-hydroxy groups, while 3 and 4 with higher oxidation states of +5 and +6 are deprotonated with α-alkoxy group even under strong acidic condition, respectively. This shows the relationship between the oxidation state and protonation of the α-alkoxy group in citrate or homocitrate, which is related to the protonation state of homocitrate in FeMo-cofactor of nitrogenase. The homocitrate in 3 chelates to molybdenum(v) with bidentate α-alkoxy and monodentate α-carboxy groups. Molybdenum(vi) citrate 4 is only protonated with coordinated and uncoordinated β-carboxy groups. The solution behaviours of 1 and 2 are discussed based on ¹H and ¹³C NMR spectroscopies and cyclic voltammograms, showing no decomposition of the species.

Oxo and thiomolybdenum(iv/vi) citrates, molybdenum(v) homocitrate and molybdenum(vi) citrate were obtained, showing the influence of coordinated α-hydroxy and α-alkoxy groups with different oxidation states.