Chemical modification utilizing a terminal structure exposed on the specific surface of polymer-metal complex nanocrystals

It has been difficult to selectively modify the surface of molecular crystals by chemical reactions because they usually have no reaction points on their surfaces. In this paper, focusing on the unique nanocrystal surface of the polymer metal complex (PMC) [{Cu₂(μ-Br)₂(PPh₃)₂}(μ-bpy)]_n having an exposed reactive terminal chain, we successfully modified the surface of PMC nanocrystals (NCs) through an alkylation reaction. Interestingly, after the alkylation reaction, the luminescence spectrum of PMC NCs blue-shifted, and the luminescence quantum yield increased. PMC NCs with a large specific surface area showed optically peculiar or characteristic properties compared with the corresponding bulk crystals. PMC NCs have high potential as a new class of luminescent materials due to their surface effect.

We modified the surface of polymer metal complex nanocrystals (PMC NCs) with the alkylation reaction by utilizing coordinatively unsaturated bipyridine ligands exposed on the (010), and successfully changed the luminescence properties of PMC NCs.     

Experimental and computational preference for phosphine regioselectivity and stereoselective tripodal rotation in HOs3(CO)8(PPh3)2(μ-1,2-N,C-η1,κ1-C7H4NS)

The site preference for ligand substitution in the benzothiazolate-bridged cluster HOs₃(CO)₁₀(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (1) has been investigated using PPh₃. 1 reacts with PPh₃ in the presence of Me₃NO to afford the mono- and bisphosphine substituted clusters HOs₃(CO)₉(PPh₃)(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (2) and HOs₃(CO)₈(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (3), respectively. 2 exists as a pair of non-interconverting isomers where the PPh₃ ligand is situated at one of the equatorial sites syn to the edge-bridging hydride that shares a common Os–Os bond with the metalated heterocycle. The solid-state structure of the major isomer establishes the PPh₃ regiochemistry at the N-substituted osmium center. DFT calculations confirm the thermodynamic preference for this particular isomer relative to the minor isomer whose phosphine ligand is located at the adjacent C-metalated osmium center. 2 also reacts with PPh₃ to give 3. The locus of the second substitution occurs at one of the two equatorial sites at the Os(CO)₄ moiety in 2 and gives rise to a pair of fluxional stereoisomers where the new phosphine ligand is scrambled between the two equatorial sites at the Os(CO)₃P moiety. The molecular structure of the major isomer has been determined by X-ray diffraction analysis and found to represent the lowest energy structure of the different stereoisomers computed for HOs₃(CO)₈(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS). The fluxional behavior displayed by 3 has been examined by VT NMR spectroscopy, and DFT calculations provide evidence for stereoselective tripodal rotation at the Os(CO)₃P moiety that serves to equilibrate the second phosphine between the two available equatorial sites.

The site preference for PPh₃ substitution in HOs₃(CO)₁₀(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (1) has been investigated.     

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.     

Copper(i) pyrimidine-2-thiolate cluster-based polymers as bifunctional visible-light-photocatalysts for chemoselective transfer hydrogenation of α,β-unsaturated carbonyls

The photoinduced chemoselective transfer hydrogenation of unsaturated carbonyls to allylic alcohols has been accomplished using cluster-based MOFs as bifunctional visible photocatalysts. Assemblies of hexanuclear clusters [Cu₆(dmpymt)₆] (1, Hdmpymt = 4,6-dimethylpyrimidine-2-thione) as metalloligands with CuI or (Ph₃P)CuI yielded cluster-based metal organic frameworks (MOFs) {[Cu₆(dmpymt)₆]₂[Cu₂(μ-I)₂]₄(CuI)₂}_n (2), {[Cu₆(dmpymt)₆]₂[Cu₂(μ-I)₂]₄}_n (3), respectively. Nanoparticles (NPs) of 2 and 3 served both as photosensitizers and photocatalysts for the highly chemoselective reduction of unsaturated carbonyl compounds to unsaturated alcohols with high catalytic activity under blue LED irradiation. The photocatalytic system could be reused for several cycles without any obvious loss of efficiency.

The photoinduced chemoselective transfer hydrogenation of unsaturated carbonyls to allylic alcohols has been accomplished using cluster-based MOFs as bifunctional visible photocatalysts.     

Titanium phosphonate oxo-alkoxide “clusters”: solution stability and facile hydrolytic transformation into nano titania

Titanium (oxo-) alkoxide phosphonate complexes were synthesized using different titanium precursors and tert-butylphosphonic acid (tBPA) as molecular models for interaction between phosphonates and titania surfaces and to investigate the solution stability of these species. Reflux of titanium(iv) ethoxide or titanium(iv)(diisopropoxide)bis(2,4-pentadionate) with tert-butylphosphonic acid in toluene–ethanol mixture or acetone yielded seven titanium alkoxide phosphonate complexes; [Ti₅(μ₃-O)(μ₂-O)(μ-HOEt)₂(μ-OEt)₃(μ₂-OEt)(μ₃-tBPA)₃(μ₃-HtBPA)(μ₂-tBPA)₂(μ₂-HtBPA)]·3EtOH, 1, [Ti₄O(μ-OEt)₅(μ₂-OEt)₇(μ₃-tBPA)], 2, [Ti₄(μ₂-O)₂(μ-OEt)₂(μ-HOEt)₂(μ₂-tPBA)₂(μ₂-HtPBA)₆]·4EtOH, 3, [Ti₄(μ₂-O)₂(μ-OEt)₂(μ-HOEt)₂(μ₂-tPBA)₂(μ₂-HtPBA)₆]·2EtOH, 4, [Ti₆(μ₂-O)(μ₃-O)₂(μ₂-OEt)₅(μ-OEt)₆(μ₃-tBPA)₃(μ₃-HtBPA)], 5, [Ti₄(μ-ⁱOPr)₄(acac)₄(μ₂-tBPA)₄], 6 and [Ti₅(μ₄-O)(μ₂-O)₃(μ₂-OEt)₄(μ-OEt)₆(μ-HOEt)(μ₃-tBPA)]₂, 7. The binding mode of tBPA to the titanium oxo-core were either double or triple bridging or a combination of the two. No monodentate or chelating coordination was observed. ³¹P NMR spectrometry of dissolved single crystals indicates that 1 and 5 retain their solid-state structures in solution, the latter even on moderate heating, while 6 and 7 dissolved into several other forms. The complexes were found to be sensitive towards hydrolysis, proceeding in a topotactic fashion with densification of the material into plates and lamellae resulting finally in “core–shell” nanoparticles with a crystalline core (anatase) and an amorphous outer shell upon contact with water at room temperature as observed by HRTEM and AFM analyses. ³¹P NMR data supported degradation after addition of water to solutions of the complexes. Hydrolysis under different conditions affords complex oxide structures of different morphologies.

Oligonuclear Ti(iv) oxo-alkoxide-phosphonate complexes, produced by reaction of tBuPO(OH)₂ with Ti(OR)₄, are easily topotactically hydrolyzed forming intricate nanostructures.     

1,2,3-Triazole based bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)-phenyl)-4-phenyl-1H-1,2,3-triazole: an ambidentate ligand with switchable coordination modes

The reaction of 1-(2-bromophenyl)-4-phenyl-1H-1,2,3-triazole (1) with Ph₂PCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2). Bisphosphine 2 exhibits ambidentate character in either the κ²-P,N or κ²-P,P coordination mode. Treatment of 2 with [M(CO)₄(piperidine)₂] (M = Mo and W) yielded κ²-P,N and κ²-P,P coordinated Mo⁰ and W⁰ complexes [M(CO)₄(2)] [M = W-κ²-P,N (4); Mo-κ²-P,P (5); W-κ²-P,P (6)] depending on the reaction conditions. Formation and stability of κ²-P,P coordinated Mo⁰ and W⁰ complexes were assessed by time dependent ³¹P{¹H} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe₂)] afforded the hetero-bimetallic complex [μ-PN,P-{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂AuCl)}-κ²-P,N}W(CO)₄] (7). The 1 : 1 reaction between 2 and [CpRu(PPh₃)₂Cl] yielded [(η⁵-C₅H₅)RuCl{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-κ²-P,P] (8), whereas the similar reaction with [Ru(η⁶-p-cymene)Cl₂]₂ in a 2 : 1 molar ratio produced a cationic complex [(η⁶-p-cymene)RuCl{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-κ²-P,N]Cl (9). Similarly, treatment of 2 with [M(COD)(Cl)₂] (M = Pd and Pt) in a 1 : 1 molar ratio yielded Pd^II and Pt^II complexes [{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}-κ²-P,P}PdCl₂] (10) and [{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}-κ²-P,P}PtCl₂] (11). The reaction of 2 with 2 equiv. of [AuCl(SMe₂)] afforded [Au₂Cl₂{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-μ-P,P] (12). Most of the complexes have been structurally characterized. Palladium complex 10 shows excellent catalytic activity towards Cu-free Sonogashira alkynylation/cyclization reactions.

This paper describes the synthesis of a triazole based bisphosphine and its transition metal chemistry and catalytic utility in Cu-free Sonogashira alkynylation/cyclization reaction.     

Vanillin-crosslinked chitosan/ZnO nanocomposites as a drug delivery system for 5-fluorouracil: study on the release behavior via mesoporous ZrO2–Co3O4 nanoparticles modified sensor and antitumor activity

Herein, a series of vanillin-crosslinked chitosan (Vn-CS) nanocomposites (NCs) containing various contents of ZnO nanoparticles (NPs) was prepared and characterized via FTIR spectroscopy, XRD, TGA, SEM and TEM. Changing the weight% of ZnO NPs in the prepared NCs resulted in an improvement in their antibacterial activity against Gram-negative and Gram-positive bacteria strains compared with the unmodified CS, and the encapsulation efficiency of 5-fluorouracil (5-FU) was found to be in the range of 61.4–69.2%. Subsequently, the release of 5-FU was monitored utilizing the mesoporous ZrO₂–Co₃O₄ NPs modified carbon paste sensor via the square-wave adsorptive anodic stripping voltammetry (SW-AdASV) technique. Also, the release mechanism of 5-FU from each NC was studied by applying the zero-order, first-order, Hixson–Crowell and Higuchi models to the experimental results. The cytotoxicity of prepared NCs and 5-FU-encapsulated NCs was evaluated against the HePG-2, MCF-7 and HCT-116 cancer cell lines, in addition to the WI-38 and WISH normal cell lines using the MTT assay. Notably, 5-FU/CV₁₀ NC exhibited the highest antitumor activity towards all tested cancer cell lines and a moderate activity against WI-38 and WISH normal cell lines with IC₅₀ values of 28.02 ± 2.5 and 31.65 ± 2.7 μg mL⁻¹, respectively. The obtained nanocomposites exhibited suitable selectivity with minimum toxicity against normal cells.

Herein, a series of vanillin-crosslinked chitosan (Vn-CS) nanocomposites (NCs) containing various contents of ZnO nanoparticles (NPs) was prepared and characterized via FTIR spectroscopy, XRD, TGA, SEM and TEM.     

Antibiofilm and Membrane-Damaging Potential of Cuprous Oxide Nanoparticles against Staphylococcus aureus with Reduced Susceptibility to Vancomycin

The antimicrobial effects of copper ions and salts are well known, but the effects of cuprous oxide nanoparticles (Cu₂O-NPs) on staphylococcal biofilms have not yet been clearly revealed. The present study evaluated Cu₂O-NPs for their antibacterial and antibiofilm activities against heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) and vancomycin-intermediate S. aureus (VISA). Nanoscaled Cu₂O, generated by solution phase technology, contained Cu₂O octahedral nanoparticles. Field emission electron microscopy demonstrated particles with sizes ranging from 100 to 150 nm. Cu₂O-NPs inhibited the growth of S. aureus and showed antibiofilm activity. The MICs and minimum biofilm inhibitory concentrations ranged from 625 μg/ml to 5,000 μg/ml and from 2,500 μg/ml to 10,000 μg/ml, respectively. Exposure of S. aureus to Cu₂O-NPs caused leakage of the cellular constituents and increased uptake of ethidium bromide and propidium iodide. Exposure also caused a significant reduction in the overall vancomycin-BODIPY (dipyrromethene boron difluoride [4,4-difluoro-4-bora-3a,4a-diaza-s-indacene] fluorescent dye) binding and a decrease in the viable cell count in the presence of 7.5% sodium chloride. Cu₂O-NP toxicity assessment by hemolysis assay showed no cytotoxicity at 625 to 10,000 μg/ml concentrations. The results suggest that Cu₂O-NPs exert their action by disruption of the bacterial cell membrane and can be used as effective antistaphylococcal and antibiofilm agents in diverse medical devices.     

The effect of the morpholinium ionic liquid anion on the catalytic activity of Rh (or Pt) complex–ionic liquid systems in hydrosilylation processes

Studies were performed on the catalytic activity for olefin hydrosilylation shown by three rhodium complexes, [{Rh(μ-OSiMe₃)(cod)}₂] (I), [{Rh(μ-Cl)(cod)}₂] (II) and [RhCl(PPh₃)₃] (III), and three platinum complexes, [Pt(PPh₃)₄] (IV), [Pt(PPh₃)₂Cl₂] (V) and PtCl₄ (VI), immobilized in a series of different anion-containing morpholinium ionic liquids. The effect of the kind of anion (its nucleophilic character) on the activity, stability and possibility of a catalytic system with multiple uses in the hydrosilylation process has been established. In the case of the best systems it was possible to reuse the same catalyst sample 10 times almost without any decrease in the activity and a TON value over 99 000 was obtained.

Rhodium and platinum complexes were immobilized in morpholinium ionic liquids, the effect of which on the catalytic activity was determined.     

Three new metal coordination polymers of bifunctional imidazolate/tetrazolate bridges: the only example of a three-dimensional framework based on rare [Co4(μ3-OH)2(μ2-Cl)2]4+ mixed oxo-chloro-clusters

Three new metal coordination polymers [Ni(μ₂-L)₂(H₂O)₂]_n(1, HL = 1-tetrazole-4-imidazole-benzene), [Co(μ₂-L)₂]_n (2), and [Co₄(μ₃-OH)₂(μ₂-Cl)₂(μ₅-L)₂(μ₂-L)₂]_n·7nH₂O (3) were hydrothermally synthesized and structurally characterized. 1 displays a neutral [Ni(μ₂-L)₂(H₂O)₂]_n chain built up from the Ni²⁺ ions bridged by deprotonated L⁻ ligands, while 2 shows another rare neutral [Co(μ₂-L)₂]_n chain based on Co²⁺ ions connected by two different coordination modes of the L⁻ ligand. 3 exhibits a rare [Co₄(μ₃-OH)₂(μ₂-Cl)₂]⁴⁺ mixed oxo-chloro-cluster-based three-dimensional framework with large elliptical channels, which are filled by unprecedented chilopod [(H₂O)₇]_n chains. Both 1 and 2 show antiferromagnetic behavior, while 3 exhibits unusual spin-canting.

The interconnection of rare [Co₄(μ₃-OH)₂(μ₂-Cl)₂]⁴⁺ mixed oxo-chloro-clusters and bifunctional bridges gives a new three-dimensional framework with unusual spin-canting behavior.     

A new synthetic route for the preparation of [Os3(CO)10(μ-OH)(μ-H)] and its reaction with bis(diphenylphosphino)methane (dppm): syntheses and X-ray structures of two isomers of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] and [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)]

The triosmium cluster [Os₃(CO)₁₀(μ-OH)(μ-H)] containing bridging hydride and hydroxyl groups at a common Os–Os edge was obtained in good yield (ca. 75%) from the hydrolysis of the labile triosmium cluster [Os₃(CO)₁₀(NCMe)₂] in THF at 67 °C. [Os₃(CO)₁₀(μ-OH)(μ-H)] reacts with dppm at 68 °C to afford the isomeric clusters 1 and 2 with the general formula [Os₃(CO)₈(μ-OH)(μ-H)(μ-dppm)] that differ by the disposition of bridging dppm ligand. Cluster 1 is produced exclusively from the reaction of [Os₃(CO)₁₀(μ-OH)(μ-H)] with dppm in CH₂Cl₂ at room temperature in the presence of added Me₃NO. Heating cluster 1 at 81 °C furnishes 2 in a process that likely proceeds by the release of one arm of the dppm ligand, followed by ligand reorganization about the cluster polyhedron and ring closure of the pendent dppm ligand. The oxo-capped [Os₃(CO)₇(μ₃-CO)(μ₃-O)(μ-dppm)] (3) has been isolated starting from the thermolysis of either 1 or 2 at 139 °C. Reactions of [Os₃(CO)₁₀(μ-dppm)] with ROH (R = Me, Et) in the presence of Me₃NO at 80 °C furnish [Os₃(CO)₈(μ-OH)(μ,η¹,κ¹-OCOR)(μ-dppm)] (4, R = Me; 5, R = Et). Clusters 1–5 have been characterized by a combination of analytical and spectroscopic studies, and the molecular structure of each product has been established by X-ray crystallography. The bonding in these products has been examined by electronic structure calculations, and cluster 1 is confirmed as the kinetic product of substitution, while cluster 2 represents the thermodynamically favored isomer.

The cluster [Os₃(CO)₁₀(μ-OH)(μ-H)] was obtained in 75% from the hydrolysis of [Os₃(CO)₁₀(NCMe)₂].     

Spontaneous in situ generation of photoemissive aurophilic oligomers in water solution based on the 2-thiocytosine ligand

Complexes [Au(S-2-thiocytosinate)(PMe₃)] (2, 2-thiocytosine = 4-amino-2-mercaptopyrimidine) and [Au(S-2-thiocytosine)(PMe₃)](CF₃CO₂) (3) have been prepared by the reaction of [Au(acac)(PMe₃)] (1, acac = acetylacetonate) or [Au(OCOCF₃)(PMe₃)] with 2-thiocytosine, respectively. The equimolecular mixture of complexes 1 and 3 also produces [{Au(PMe₃)}₂(μ-S,N¹-2-thiocytosinate)](CF₃CO₂) (4), which features two distinct [Au(PMe₃)]⁺ groups coordinated to the S and N¹ atoms of the heterocycle. Complex 4 experiences a ligand redistribution process in water solution that liberates [Au(PMe₃)₂](CF₃CO₂) and a brightly coloured and luminescent species of [Au_n(μ-S,N¹-2-thiocytosinate)_n] stoichiometry, presumably as a tetraauracycle (n = 4).

The doubly-aurated [{Au(PMe₃)}₂(μ-S,N¹-2-thiocytosinate)]⁺ cation breaks up in water solution to form a strongly-coloured and photoluminescent neutral aurophilic oligomer.     

In Vitro Activity of Solithromycin against Erythromycin-Resistant Streptococcus agalactiae

The in vitro antibacterial activity of solithromycin (CEM-101) against macrolide-resistant isolates (n = 62) of Streptococcus agalactiae (group B streptococcus [GBS]) was determined. Phenotypic characterization of macrolide-resistant strains was performed by double-disc diffusion testing. A multiplex PCR was used to identify the erm(B), erm(TR), and mef(A/E) genes, capsular genotypes, and alpha-like (Alp) protein genes from the GBS strains. Determination of MIC was carried out using the microdilution broth method. The Etest method was used for penicillin, azithromycin, clarithromycin, and erythromycin. Solithromycin had a MIC₅₀ of ≤0.008 μg/ml and a MIC₉₀ of 0.015 μg/ml against macrolide-susceptible S. agalactiae. These MICs were lower than those displayed by penicillin (MIC₅₀ of 0.032 μg/ml and MIC₉₀ of 0.047 μg/ml), the antibiotic agent of choice for prophylaxis and treatment of GBS infections. Against macrolide-resistant S. agalactiae, solithromycin had a MIC₅₀ of 0.03 μg/ml and a MIC₉₀ of 0.125 μg/ml. Against erm(B) strains, solithromycin had a MIC₅₀ of 0.03 μg/ml and a MIC₉₀ of 0.06 μg/ml, while against mef(A) strains, it had a MIC₅₀ of 0.03 μg/ml and a MIC₉₀ of 0.125 μg/ml. Most erythromycin-resistant GBS strains were of serotype V (64.5%) and associated significantly with alp2-3. Moreover, a statistically significant association was observed between the constitutive macrolide-lincosamide-streptogramin B resistance (cMLS_B) phenotype and the erm(B) gene-carrying strains, the alp2-3 gene and the M phenotype, and the mef(A/E) gene and epsilon. Overall, our results show that solithromycin had lower or similar MICs than penicillin and potent activity against macrolide-resistant strains independent of their genotype or phenotype, representing a valid therapeutic alternative where β-lactams cannot be used.     

Hydrazine-solvothermal methods to synthesize polymeric thioarsenates from one-dimensional chains to a three-dimensional framework

A series of polymeric Mn(ii)-thioarsenates [Mn(en)₃]_n[(N₂H₄)₂Mn₆(μ₆-S)(μ-N₂H₄)₂(μ₃-AsS₃)₄]_n (1), [N₂H₅]_n[{Mn(μ-N₂H₄)₂(μ-AsS₄)}·0.5en]_n (2), [Mn(μ-trien){Mn(μ-N₂H₄)(μ-AsS₃)}₂]_n (3), [{Mn(N₂H₄)}₂(μ-N₂H₄)₂{Mn(μ-N₂H₄)₂(μ-AsS₃)₂}]_n (4), [Mn₃(μ-N₂H₄)₆(μ₃-AsS₄)(μ₂-AsS₄)]_n (5), and [Mn(NH₃)₆]_n[{Mn(NH₃)(μ-AsS₄)}₂]_n (6) were synthesized using a hydrazine-solvothermal method. The thioarsenate units AsS₃ and AsS₄ coordinate to Mn(ii) ions with variable coordination modes, forming a Mn–As–S ternary cluster (1), chains (2, 4–6), and layers (3), respectively. The hydrazine molecules act as inter-cluster, intra-chain and intra-layer bridging ligands to join the Mn(ii) ions, resulting in hydrazine hybrid 1-D, 2-D, and 3-D Mn(ii)-thioarsenate moieties in 1–5. Compounds 1–6 exhibit tunable semiconducting band gaps varying in the range of 2.19–2.47 eV. Compound 1 displays stronger antiferromagnetic coupling interactions than that of compound 2.

Mn(ii)-thioarsenates [Mn(en)₃]_n[Mn₆S(N₂H₄)₄(AsS₃)₄]_n (1), [N₂H₅]_n[{Mn(N₂H₄)₂(AsS₄)}·0.5en]_n (2), [Mn(trien){Mn(N₂H₄)(AsS₃)}₂]_n (3), [Mn₃(N₂H₄)₆(AsS₃)₂]_n (4), [Mn₃(N₂H₄)₆(AsS₄)₂]_n (5), and [Mn(NH₃)₆]_n[{Mn(NH₃)(AsS₄)}₂]_n (6) were prepared in N₂H₄ by solvothermal methods.     

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.     

Microstructural analysis,magnetic properties,magnetocaloric effect,and critical behaviors of Ni0.6Cd0.2Cu0.2Fe2O4 ferrites prepared using the sol–gel method under different sintering temperatures

This work focuses on the microstructural analysis, magnetic properties, magnetocaloric effect, and critical exponents of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites. These samples, denoted as S1000 and S1200, were prepared using the sol–gel method and sintered separately at 1000 °C and 1200 °C, respectively. XRD patterns confirmed the formation of cubic spinel structures and the Rietveld method was used to estimate the different structural parameters. The higher sintering temperature led to an increased lattice constant (a), crystallite size (D), magnetization (M), Curie temperature (T_C), and magnetic entropy change (−ΔS_M) for samples that exhibited second-order ferromagnetic–paramagnetic (FM–PM) phase transitions. The magnetic entropy changed at an applied magnetic field (μ₀H) of 5 T, reaching maximum values of about 1.57–2.12 J kg⁻¹ K⁻¹, corresponding to relative cooling powers (RCPs) of 115 and 125 J kg⁻¹ for S1000 and S1200, respectively. Critical exponents (β, γ, and δ) for samples around their T_C values were studied by analyzing the M(μ₀H, T) isothermal magnetizations using different techniques and checked by analyzing the −ΔS_Mvs. μ₀H curves. The estimated values of β and γ exponents (using the Kouvel–Fisher method) and δ exponent (from M(T_C, μ₀H) critical isotherms) were β = 0.443 ± 0.003, γ = 1.032 ± 0.001, and δ = 3.311 ± 0.006 for S1000, and β = 0.403 ± 0.008, γ = 1.073 ± 0.016, and δ = 3.650 ± 0.005 for S1200. Obviously, these critical exponents were affected by an increased sintering temperature and their values were different to those predicted by standard theoretical models.

This work focuses on the microstructural analysis, magnetic properties, magnetocaloric effect, and critical exponents of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites.     

Ginkgo biloba leaf polysaccharide stabilized palladium nanoparticles with enhanced peroxidase-like property for the colorimetric detection of glucose

Sensitive glucose detection based on nanoparticles is good for the prevention of illness in our bodies. However, many nanoparticles lack stability and biocompatibility, which restrict their sensitivity to glucose detection. Herein, stable and biocompatible Ginkgo biloba leaf polysaccharide (GBLP) stabilized palladium nanoparticles (Pd_n-GBLP NPs) were prepared through a green method where GBLP was used as a reducing and stabilizing agent. The results of Pd_n-GBLP NPs characterized by UV-visible spectroscopy (UV-Vis), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS) confirmed the successful preparation of Pd_n-GBLP NPs. TEM results indicated that the sizes of Pd NPs inside of Pd_n-GBLP NPs (n = 41, 68, 91 and 137) were 7.61, 9.62, 11.10 and 13.13 nm, respectively. XPS confirmed the successful reduction of PdCl₄²⁻ into Pd (0). Dynamic light scattering (DLS) results demonstrated the long-term stability of Pd_n-GBLP NPs in different buffer solutions. Furthermore, Pd₉₁-GBLP NPs were highly biocompatible after incubation (500 μg mL⁻¹) with HeLa cells for 24 h. More importantly, Pd₉₁-GBLP NPs had peroxidase-like properties and followed a ping-pong mechanism. The catalytic oxidation of substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB) by Pd₉₁-GBLP NPs was used to detect the glucose concentration. This colorimetric method had high selectivity, wide linear range from 2.5 to 700 μM and a low detection limit of 1 μM. This method also showed good accuracy for the detection of glucose concentrations in blood. The established method has great potential in biomedical detection in the future.

Ginkgo biloba leaf polysaccharide stabilized palladium nanoparticles had high stability, good biocompatibility and low detection limit for glucose.     

Silver derivatives of multi-donor heterocyclic thioamides as antimicrobial/anticancer agents: unusual bio-activity against methicillin resistant S. aureus,S. epidermidis,and E. faecalis and human bone cancer MG63 cell line

The basic aim of this study pertains to the synthesis of silver nitrate complexes and the study of their antimicrobial and anticancer bio-activity. A series of new silver(i) derivatives of N-substituted-imidazolidine-2-thiones (L-NR, R = Et, Prⁿ, Buⁿ, Ph), purine-6-thione (purSH₂), 2-thiouracil (tucH₂), pyrimidine-2-thione (pymSH) and pyridine-2-thione (pySH) of composition [Ag(S-L-NR)(PPh₃)₂(ONO₂)] {R = Et (1), Prⁿ (2), Buⁿ (3), Ph (4)}, [Ag₂(N,S-purSH₂)₂(μ-dppm)₂](NO₃)₂·2H₂O (5) (dppm = Ph₂P–CH₂–PPh₂), [Ag(L)(PPh₃)₂](NO₃) {L = N,S-purSH₂ (6); S-tucH₂ (7)}, [Ag(N,S-pymS)(PPh₃)₂](CH₃OH) (8), and [Ag(N,S-pyS)(PPh₃)₂] (9) have been synthesized and structurally characterized. These new and some previously reported complexes {[Ag₂(L-NH)₄(PPh₃)₂](NO₃)₂ (10), [Ag(L-NMe)₂(PPh₃)](NO₃) (11), and [Ag(S-bzimSH)₂(PPh₃)₂](OAc) (12), L-NH = 1,3-imidazolidine-2-thione; L-NMe = 1-methyl-3-imidazolidine-2-thione and bzimSH₂ = benzimidazoline-2-thione)} have shown moderate to high anti-microbial activity against Gram positive bacteria, namely methicillin resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (MTCC 740), and Gram negative bacteria, namely Staphylococcus epidermidis (MTCC 435), Enterococcus faecalis (MTCC 439), Shigella flexneri (MTCC 1457) and a yeast Candida albicans (MTCC 22). These complexes have also been found to be bio-safe as studied using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. The anti-tumor study of silver complexes against human osteosarcoma cell line (MG63) has shown IC₅₀ values in the range of 6–33 μM.

A series of biosafe mixed-ligand complexes of silver with heterocyclic thioamides have been studied for their antimicrobial/anticancer activity.     

Cu2−xSe nanoparticles (Cu2−xSe NPs) mediated neurotoxicity via oxidative stress damage in PC-12 cells and BALB/c mice

Cu_2−xSe nanoparticles (Cu_2−xSe NPs) are widely used for optical diagnostic imaging and photothermal therapy due to their strong near-infrared (NIR) optical absorption. With the continuous expansion of applications using Cu_2−xSe NPs, their biosafety has received increasing attention in recent years. Cu_2−xSe NPs can enter the brain by crossing the blood–brain barrier, but the neurotoxicity of NPs remains unclear. The present investigation provides direct evidence that the toxicity of Cu_2−xSe NPs can be specifically exploited to kill rat pheochromocytoma PC-12 cells (a cell line used as an in vitro model for brain neuron research) in dose- and time-dependent manners. These cytotoxicity events were accompanied by mitochondrial damage, adenosine triphosphate (ATP) depletion, production of oxidizing species (including reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂)), as well as reductions in antioxidant defense systems (glutathione (GSH) and superoxide dismutase (SOD)). Moreover, our in vivo study also confirmed that Cu_2−xSe NPs markedly induced neurotoxicity and oxidative stress damage in the striatum and hippocampal tissues of BALB/c mice. These findings suggest that Cu_2−xSe NPs induce neurotoxicity in PC-12 cells and BALB/c mice via oxidative stress damage, which provides useful information for understanding the neurotoxicity of Cu_2−xSe NPs.

Cu_2−xSe nanoparticles (Cu_2−xSe NPs) are widely used for optical diagnostic imaging and photothermal therapy due to their strong near-infrared (NIR) optical absorption.     

Simultaneous detection of l-aspartic acid and glycine using wet-chemically prepared Fe3O4@ZnO nanoparticles: real sample analysis

An easy and reliable wet-chemical method was used to synthesize iron oxide doped zinc oxide nanoparticles (Fe₃O₄@ZnO NPs) at a low-temperature under alkaline medium. The electrochemical characteristics of Fe₃O₄@ZnO NPs were investigated by using different electrochemical techniques such as UV-vis, FTIR, XRD, FESEM, XEDS, and XPS. A sensor was fabricated by deposition of a thin covering of Fe₃O₄@ZnO NPs onto a flat dried glassy carbon electrode (GCE) with a polymer matrix with conducting characteristics (Nafion, Nf). l-Aspartic acid and glycine were detected simultaneously by using the modified GCE/Fe₃O₄@ZnO NPs/Nf sensor in enzyme free conditions. Calibration curves were found to be linear for l-aspartic acid (R² = 0.9593) and glycine (R² = 0.8617) over a broad range of detected bio-molecule concentration (100.0 pM to 100.0 mM). The analytical sensing parameters, for example sensitivity, linear dynamic range (LDR), limit of detection (LOD), and limit of quantification (LOQ), of the proposed sensor (GCE/Fe₃O₄@ZnO NPs/Nf) were calculated at two potentials (+0.4 V and +0.7 V) from the calibration plot for l-aspartic acid (126.58 pM μM⁻¹ cm², 100.0 pM to 10.0 μM, ≈97.5 pM, and 325.0 mM) and glycine (316.46 pM μM⁻¹ cm², 1.0 μM to 1.0 mM, ≈13.5 pM, and 450.0 mM), respectively, by using a reliable current–voltage (I–V) technique. The synthesis of Fe₃O₄@ZnO NPs by means of a wet-chemical route is a good advancement for the development of doped nanomaterial based sensors from the perspective of enzyme-free detection of biological molecules in health-care areas. This proposed GCE/Fe₃O₄@ZnO NPs/Nf sensor was used for the particular detection of l-aspartic acid and glycine in real samples (human and rabbit serum and urine) and found to achieve reasonable and accepted results.

An easy and reliable wet-chemical method was used to synthesize iron oxide doped zinc oxide nanoparticles (Fe₃O₄@ZnO NPs) at a low-temperature under alkaline medium.