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In this work, a new type of zinc(II) coordination polymer {[Zn(HIDC)(BBM)0.5]·H2O} n (Zn-CP) was synthesized using 4,5-imidazoledicarboxylic acid (H3IDC) and 2,2-(1,4-butanediyl)bis-1,3-benzimidazole (BBM) under hydrothermal conditions. Its structure has been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction analysis. The Zn(II) ion is linked by the HIDC2− ligand to form a zigzag chain by chelating and bridging, and then linked by BBM to form a layered network structure. Adjacent layers are further connected by hydrogen bond interaction to form a 3-D supramolecular framework. The solid-state fluorescence performance of Zn-CP shows that compared with free H3IDC ligand, its fluorescence intensity is significantly enhanced.

A new silver(I) complex of the type [Ag2(mbbp)2](pic)2·DMF·CH3OH [mbbp = 2,6-bis( N-methylbenzimidazol-2-yl)pyridine] is synthesized and analyzed using a range of spectroscopic and crystallographic techniques. This compound contains cationic Ag2(mbbp)2 dimers, in which the crossed eight-shaped structure is formed by two mbbp ligands bridging two silver(I) centers and Ag–Ag bonds. Two-dimensional supramolecular networks of the silver(I) complex are connected by π···π interactions and hydrogen bonds. Hirshfeld analyses are performed to support the aforementioned intermolecular interactions. The effect of π···π stacking interactions on the fluorescence properties of the complex is investigated. Cyclic voltammetry indicates two irreversible redox processes. In addition, an antioxidant assay in vitro demonstrates that the silver(I) complex displays excellent scavenging activity toward hydroxyl radicals.

Bis(N-ethylbenzimidazol-2-ylmethyl)allylamine (EtAIDB) and its two complexes, [Mn(EtAIDB)Cl2] (1) and [Zn(EtAIDB)Cl2] (2), have been synthesized and characterized by elemental analyses, molar conductivities, UV–Visible and IR spectra. The crystal structures of both complexes have been determined by X-ray single crystal diffraction. The coordination environment of Mn(II) in 1 is a five-coordinate distorted trigonal bipyramid with a N3Cl2 ligand set, while 2 is a four-coordinate twisted tetrahedral geometry. Structural and Hirshfeld surface analysis reveals that these two complexes are dimers formed by π···π interactions. The antioxidant activity was determined by superoxide methods in vitro, indicating that 1 exhibited potential antioxidant properties.

Three new metal complexes, namely: [Mn(AIDB)Cl2]·DMF (1), [Zn(AIDB)Br2]·CH3OH (2) and [Co(AIDB)Cl2]·CH3OH (3) having a ligand bis(benzimidazol-2-ylmethyl)allylamine (AIDB), have been synthesized in high yields and characterized by elemental analyses, molar conductivities, IR, UV–Vis spectra and single-crystal X-ray diffraction. The structural analysis revealed that all the three complexes 1–3 have five-coordinated trigonal bipyramid geometry where the degree of distorting is 1>3>2. In vitro antioxidant activity assay demonstrates that the complexes 1 and 3 display high scavenging activity against hydroxyl (OH·) and superoxide (O2−·) radicals.

BackgroundTemporal interference (TI) stimulation is a new technique of noninvasive brain stimulation. Envelope-modulated waveforms with two high-frequency carriers can activate neurons in target brain regions without stimulating the overlying cortex, which has been validated in mouse brains. However, whether TI stimulation can work on the human brain has not been elucidate.ObjectiveTo assess the effectiveness and safety aspect of the envelope-modulated waveform of TI stimulation on human primary motor cortex (M1).MethodsParticipants attended three sessions of 30-min TI stimulation at 2 mA during a random reaction time task (RRTT) or a serial reaction time task (SRTT). Motor cortex excitability was measured before and after TI stimulation.ResultsIn the RRTT experiment, only 70 Hz TI stimulation had a promoting effect on the reaction time (RT) performance and excitability of the motor cortex compared to sham stimulation. Meanwhile, compared with the sham condition, only 20 Hz TI stimulation significantly facilitated motor learning in the SRTT experiment, which was significantly positively correlated with the increase in motor evoked potential.ConclusionThese results indicate that the envelope-modulated waveform of TI stimulation has a significant promoting effect on human motor functions, experimentally suggesting the effectiveness of TI stimulation in humans for the first time and pave the way for further explorations.

Reaction of bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) with Ce(NO3)3 afforded a new Ce(III) complex with composition [Ce(H2L)(NO3)3] (1). Complex 1 reacts with zinc acetate and terephthalic acid to prepare complex 2, [Zn4Ce2(L)4(terephthalate)2][Ce(DMF)(NO3)5]. They have been characterized by elemental analysis, UV/Vis and IR spectroscopy, and single-crystal X-ray diffraction. The structure analysis revealed that 1 is mononuclear, whereas 2 is d-f heteronuclear. The fluorescence properties of the ligand and complexes 1 and 2 were studied in the solid state. The significantly blue-shifted emissions and enhancement of fluorescence in 1 and 2 relative to the ligand were attributed to coordination of ligand with metal ions. The results show that the structure and fluorescence of the Ce(III) complexes can be modified by introducing Zn(II) ion and auxiliary ligand terephthalate.

Supplemental material, sj-pdf-2-chl-10.1177_1747519820978588 for Synthesis, structure, fluorescence, electrochemical, and antioxidant studies of a new silver(I) complex with 2,6-bis(N-methylbenzimidazol-2-yl)pyridine by Lixian Xia, Xinzhao Xia, Geng Zhang, Yancong Wu, Huilu Wu and Jianhua Xu in Journal of Chemical Research

Supplemental material, sj-pdf-1-chl-10.1177_1747519820978588 for Synthesis, structure, fluorescence, electrochemical, and antioxidant studies of a new silver(I) complex with 2,6-bis(N-methylbenzimidazol-2-yl)pyridine by Lixian Xia, Xinzhao Xia, Geng Zhang, Yancong Wu, Huilu Wu and Jianhua Xu in Journal of Chemical Research

Although previous studies have reported correlations between alpha oscillations and the “retention” sub-process of working memory (WM), no direct causal evidence has been established in human neuroscience. Here, we developed an online phase-locking closed-loop transcranial alternating current stimulation (tACS) system capable of precisely controlling the phase difference between tACS and concurrent endogenous oscillations. This system permits both up- and down-regulation of brain oscillations at the target stimulation frequency, and is here applied to empirically demonstrate that parietal alpha oscillations causally relate to WM retention. Our experimental design included both in-phase and anti-phase alpha-tACS applied to 39 participants during the retention intervals of a modified Sternberg paradigm. Compared to in-phase alpha-tACS, anti-phase alpha-tACS decreased both WM performance and alpha activity. Moreover, the in-phase tACS-induced changes in WM performance were positively correlated with alpha oscillatory activity. These findings strongly support a causal link between alpha oscillations and WM retention, and illustrate the broad application prospects of phase-locking tACS.

Two new one-dimensional (1D) double-chain Ag(I) coordination polymers, namely: {[Ag(Hcn)(bpy)]·2CH3OH}n (1), [Ag2(Hidc)(H2O)2]n (2) (Hcn = 2-hydroxycinnamate, bpy = 4,4′-bipyridine, Hidc = 4,5-imidazoledicarboxylate), were synthesized by volatilization method and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectra. Single-crystal analyses show that although two Ag(I) CPs are both 1D double-chain structure constructed by Ag-Ag bonds, CP 1 is linear, while CP 2 is zigzagged. This difference in the structure may be due to the symmetry of the repeat unit of the Ag(I) CPs and the linkage pattern of the Ag-Ag bonds, in which the repeat unit of CP 1 is symmetric, whereas that of CP 2 is asymmetric. The fluorescence properties of the ligands and CPs 1-2 in the solid-state were studied. The fluorescence peaks of the two Ag(I) CPs were weakened compared to the ligands, which is attributed to ligand-centered fluorescence. The partial quenching of the aggregates may be due to the Ag-Ag interactions. In addition, cyclic voltammograms of CPs 1-2 indicated an irreversible Ag+/Ag couple with the order of reversibility being 1 > 2.

Three heteronuclear Cd–Ln clusters based on open-chain ether Schiff (bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) and niacin (NA), with composition [Cd6Ln4L5 (OAc)5(NA)5(CH3OH)5](NO3)4·x(CH3OH)·y(CH2Cl2) (1 Ln = Sm, x = 1, y = 1; 2 Ln = Eu, x = 0, y = 1; 3 Ln = Tb, x = 2, y = 1), have been synthesized and structural characterizated. The structure analysis reveals that 1–3 contain the similar sandwich-type polycationic unit [Cd6Ln4L5(OAc)5(NA)5(CH3OH)5]4+. Solid-state luminescence studies show that the emission peaks of the H2L ligand located in the range of 340 ~ 373 nm in 1–3. The characteristic emission peaks of Sm3+ ion appear in cluster 1, but there is no Eu3+ or Tb3+ ion emission peak in clusters 2 and 3. The fluorescence spectra of 1–3 in N,N-dimethylformamide (DMF) solution only appear emission peaks of π*→π transition of [CdL] coordination units, but characteristic emission peaks of Ln3+ ions didn’t emerge. It is possible that the DMF molecules impeded the energy transfer from [CdL] coordination units to the lanthanum(III) ions. Moreover, antioxidation properties indicate that H2L and 1–3 have outstanding biological activity in scavenging oxygen free radicals.

Two new Cd(II) coordination polymers (CPs), {[Cd(BBM)Cl2]·CH3OH}n (1) and [Cd2(BBM)2(isophthalate)2]n (2) (BBM = 2,2-(1,4-butanediyl)bis-1,3- benzimidazole), have been obtained from hydrothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV-Vis spectra. The CP 1 displays a one-dimensional (1D) square wave chain structure connected by BBM ligands, whereas CP 2 is a 2D layer network. The structure analysis revealed that the selection of anions with different coordination modes realizes the control of the structure of the cadmium coordination polymer. Weak hydrogen bonds and π···π interactions are the major driving forces in the crystal packing of the two coordination polymers. Hirshfeld surface analysis reveals detailed scrutiny of intermolecular interactions experienced by each complex. In addition, the fluorescence properties of the ligands and CPs 1-2 in the solid-state were studied. The fluorescence peaks of the two Cd(II) CPs were weakened compared to the free ligands, which is attributed to ligand-centered fluorescence. The partial quenching of the aggregates may be due to the π···π stacking and heavy atom effect.

Two heteronuclear Zn-Eu and Cd-Eu complexes with open-chain ether Schiff base ligand (bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) and isonicotinate (IN), with composition [Zn2EuL2(OAc)(IN)](NO3)•(CH2Cl2) (1) and {[CdEuL(IN)(OAc)(NO3)(CH3OH)]•3(CH2Cl2)}n (2), have been synthesized and characterized. The structure analysis reveals that the Zn-Eu complex is heterotrinuclear cluster and lanthanide ion acts as a joint bridging of two Zn-L coordination units, whereas the Cd-Eu complex is infinite 1D zigzag coordination polymer formed by Cd-Eu-L secondary units through bridging of isonicotinate. Fluorescence properties of complexes 1–2 in the solid state and DMF solution at room temperature were studied. It has been found that the emission spectra of complexes 1–2 do not exhibit corresponding EuIII ion characteristic emission bands and the fluorescence properties of complexes 1–2 are different due to the introduction of different transition metal ions. Antioxidant properties of the ligand and complexes 1–2 were also studied, the results showed that the ligand and complexes 1–2 display high scavenging activity against hydroxyl (OH•) and superoxide (O2−•) radicals, and the order of the activity is complex 2 > complex 1 > H2L. Therefore, the structures and properties of d -f heteronuclear complexes can be adjusted by selecting different transition metal ions such as ZnII and CdII ions.

Two open-chain ether Schiff base d-f heteronuclear complexes with bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) and isonicotinate (IN), with composition [Zn2DyL2(OAc)(IN)](NO3)·2(CH3OH)·(CH2Cl2) and {[CdDyL(IN)(OAc)(NO3)(CH3OH)]·3(CH2Cl2)}n, have been synthesized by interfacial diffusion methods and further performed structural characterization. The structure analysis revealed that Zn-Dy complex is heterotrinuclear complex and DyIII ion acts as a joint bridging of two ZnL coordination units, whereas Cd-Dy complex is infinite 1D zigzag coordination polymer formed by CdDyL secondary units through bridging of isonicotinate. Fluorescence properties of 1-2 in the solid state and DMF solution at room temperature were also studied. It has been found that the emission spectra of complexes 1-2 do not exhibit corresponding DyIII ion characteristic emission peaks and the emission bands of complexes 1-2 are different due to the introduction of different transition metal ions. Antioxidation properties of the ligand and 1-2 were also studied, showing that the order of antioxidant activity is complex 2 > complex 1 > H2L. Thus, the structures and properties when constructing d-f heteronuclear complexes could be adjusted by selecting different transition metal ions such as ZnII ions and CdII ions.

Two series of heteronuclear Zn-Ln and Cd-Ln complexes with open-chain ether Schiff base ligand (bis(5-bromine-3-methoxysalicylidene)-3-oxapentane- 1,5-diamine (H2L) and isonicotinate (IN), with composition [Zn2LnL2(OAc)(IN)](NO3)·x(CH3OH)·y(CH2Cl2) (1 Ln = Sm, x = 1, y = 0; 2 Ln = Tb, x = 0, y = 2) and {[CdLnL(IN)(OAc)(NO3)(CH3OH)]·3(CH2Cl2)}n (3 Ln = Sm; 4 Ln = Tb), have been synthesized by interfacial diffusion methods and further performed structural characterization. The structure analysis revealed that two Zn-Ln complexes are heterotrinuclear clusters and lanthanide metal ion acts as a joint bridging of two ZnL coordination units, whereas two Cd-Ln complexes are infinite one dimensional zigzag coordination polymers formed by CdLnL secondary units through asymmetric coordination bridging isonicotinate. Luminescence properties of 1–4 in the solid state and N, N-dimethylformamide (DMF) solution at room temperature were also studied. It has been found that the Sm3+ complexes 1 and 3 exhibit corresponding Sm3+ ion characteristic emission in the solid state, but the L2− ligand can’t sensitize the Tb3+ ion in complexes 2 and 4. Finally, the structures and luminescence properties of d-f heteronuclear complexes can be adjusted by selecting different transition metals such as zinc and cadmium.