Search

A bidentate boron Lewis acid based on 1,8‐diethynylanthracene has been studied in detail with respect to its adduct formation with diamines and diphosphanes of different linker lengths between the donor functions. A clear correlation between the linker length of the bifunctional base and the formation of 1 : 1 adducts, 1 : 2 adducts or oligomers was found. The adducts were characterized in solution by NMR titration experiments and structurally by X‐ray diffraction. In addition, adduct formation and competition experiments of the host system with ZR3 (Z=N, P; R=H, Me) demonstrated the generally higher stability of alkylphosphane adducts compared to alkylamine adducts with boron functions. The results provide a general insight into the adduct formation of bidentate Lewis acids with guests of different sizes as well as the differences in stability between borane‐amine and borane‐phosphane adducts. [ABSTRACT FROM AUTHOR]

This article explores the use of pyrazolopyridine ligands in transition-metal-catalyzed reactions. These ligands have a wide range of effects and have been used in various oxidative and reductive reactions, as well as in applications such as solar cells and organic light-emitting diodes. The article discusses the synthesis of these ligands and their role in facilitating the formation of C-C and C-heteroatom bonds. It also provides specific examples of their use in different catalytic reactions, highlighting the importance of ligand design. The article encourages further research into the potential of pyrazolopyridine ligands in catalytic processes. [Extracted from the article]

A bidentate chiral dithiol (diBINAS) is utilised to bridge Au25 nanoclusters to form oligomers. Separation by size allows the isolation of fractions that are stable thanks to the bidentate nature of the linker. The structure of the products is elucidated by small‐angle X‐ray scattering and calculated using density functional theory. Additional structural details are studied by diffusion‐ordered nuclear magnetic resonance spectroscopy, transmission electron microscopy and matrix‐assisted laser desorption/ionization time of flight mass spectrometry. Significant changes in the optical properties are analysed by UV/Vis and fluorescence spectroscopies, with the latter demonstrating a strong emission enhancement. Furthermore, the emergent chiral characteristics are studied by circular dichroism. Due to the geometry constraints of the nanocluster assemblies, diBINAS can be regarded as a templating molecule, taking a step towards the directed self‐assembly of metal clusters. [ABSTRACT FROM AUTHOR]

Cisplatin (cis-diamminedichloroplatinum(II)) is a potent chemotherapeutic agent commonly used to treat cancer. However, its use also leads to serious side effects, such as nephrotoxicity, ototoxicity, and cardiotoxicity, which limit the dose that can be safely administered to patients. To minimize these problems, dendrimers may be used as carriers for cisplatin through the coordination of their terminal functional groups to platinum. Here, cisplatin was conjugated to half-generation anionic PAMAM dendrimers in mono- and bidentate forms, and their biological effects were assessed in vitro. After preparation and characterization of the metallodendrimers, their cytotoxicity was evaluated against several cancer cell lines (A2780, A2780cisR, MCF-7, and CACO-2 cells) and a non-cancer cell line (BJ cells). The results showed that all the metallodendrimers were cytotoxic and that the cytotoxicity level depended on the cell line and the type of coordination mode (mono- or bidentate). Although, in this study, a correlation between dendrimer generation (number of carried metallic fragments) and cytotoxicity could not be completely established, the monodentate coordination form of cisplatin resulted in lower IC50 values, thus revealing a more accessible cisplatin release from the dendritic scaffold. Moreover, most of the metallodendrimers were more potent than the cisplatin, especially for the A2780 and A2780cisR cell lines, which showed higher selectivity than for non-cancer cells (BJ cells). The monodentate G0.5COO(Pt(NH3)2Cl)8 and G2.5COO(Pt(NH3)2Cl)32 metallodendrimers, as well as the bidentate G2.5COO(Pt(NH3)2)16 metallodendrimer, were even more active towards the cisplatin-resistant cell line (A2780cisR cells) than the correspondent cisplatin-sensitive one (A2780 cells). Finally, the effect of the metallodendrimers on the hemolysis of human erythrocytes was neglectable, and metallodendrimers' interaction with calf thymus DNA seemed to be stronger than that of free cisplatin. [ABSTRACT FROM AUTHOR]

Two copper(II) complexes of 4-chloro- and 4-dimethylaminobenzaldehyde nicotinic acid hydrazones were prepared and characterized by elemental analysis, mass spectrometry, infrared and electron spectroscopy and conductometry. These rare examples of bis(hydrazonato)copper(II) complexes are neutral complex species with copper(II) center coordinated with two monoanionic bidentate O,N-donor hydrazone ligands coordinated in enol-imine form. The interaction of hydrazone ligands and corresponding copper(II) complexes with CT DNA and BSA was investigated. Copper(II) complexes are slightly effective in binding the DNA than pristine hydrazones. The results indicate groove binding or moderate intercalation which are not significantly affected by the nature of substituent at hydrazone ligands. On contrary, affinities of two copper(II) complexes toward BSA significantly differs and depends on the nature of the substituent, however in absence of thermodynamic data difference in nature of binding forces cannot be excluded. The complex bearing electron-withdrawing 4-chloro substituent has larger affinity toward BSA compared to 4-dimethyamino analogue. These findings were theoretically supported by molecular docking study. [ABSTRACT FROM AUTHOR]

Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with Ln(NO3)3·xH2O (Ln = Gd and Dy; x = 6 and 5, respectively) and LnCl3·6H2O (Ln = Nd, Gd and Dy). The crystal structures of the former two Ln(III) nitrate complexes are isostructural and the coordination sphere is composed of three monodentate HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin polyhedra geometric type. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5059 and 2.2816 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate Schiff base ligands [Ln-Ophenolate distances range from 2.229(4) to 2.2797(18) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6530 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolate oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H···Cl interactions present and O-H···N hydrogen bonds are also observed in the crystal packing. [ABSTRACT FROM AUTHOR]

Whereas the close associations of cesium ion with organochlorine compounds have been previously documented, the present report is the first attempt to exploit these interactions to create a trichloroethylene (TCE)-selective sensor. Gold monolayer-protected clusters peripherally functionalized with Cs+ ions were used to prepare a chemiresistance film on MEMS-fabricated interdigitated electrodes. Vapor sensing properties of the cesium-rich chemiresistor were determined using a panel of chlorinated hydrocarbons including TCE as well as polar and non-polar VOCs for comparison. The sensor was selective and highly sensitive toward VOCs containing a 1,2-dichloro group at concentrations as low as 0.1 ppm. The results suggest the key interaction contributing to sensor response is a bidentate, metallocycle-like coordination of the 1,2-dichloro group to the cesium cations at the sensor surface. [Display omitted] • Gold monolayer-protected clusters peripherally functionalized with Cs+ ions were synthesized to prepare a chemiresistor sensor. • Vapor sensing properties of the cesium-rich chemiresistor were determined using a panel of chlorinated hydrocarbons. • The sensor was selective and highly sensitive toward VOCs containing a 1,2-dichloro group \. • The key interaction contributing to sensor response is a metallocycle-like coordination of the 1,2-dichloro group to cesium cations. [ABSTRACT FROM AUTHOR]

Abstract Starting from 1,2‐diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis‐acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing −SiClMe2, −SiCl2Me, −SiCl3, −B(C6F5)2, −AlBis2 (Bis=bis(trimethylsilyl)methyl) and −GaEt2 as the corresponding functional units. In all cases, the Lewis acid functionalisation was carried out twice and the products were obtained in good to excellent yields. In the case of the twofold gallium Lewis acid, a different structural motif in the form of a polymer‐like chain was observed in the solid state. All new bidentate Lewis acids were characterised by multinuclear NMR spectroscopy, CHN analysis and X‐ray diffraction experiments.

Monomeric [Cu(DACH)(L)]2+ (DACH=1,2‐diaminocyclohexane) heteroleptic copper(II) complexes (1–4) on reaction with diphenyl phosphate yielded dinuclear phosphate bridged copper(II) complexes [Cu2L2(dpp)3]+ (5–7), [dpp=diphenyl phosphate; L=bpy (5), Phen (6), 5, 6 dimethyl phenanthroline, (7)] and a tetra‐nuclear [Cu4(2,9‐dmp)2(dpp)4(OH)2]2+ complex (8) (2, 9 dmp=2, 9 dimethyl phenanthroline). Interestingly, isomeric ligands 5,6‐dmp and 2,9‐dmp yielded dinuclear complex 7 and tetra‐nuclear complex 8 triggered by steric effects. Even though the initial combination contains mixed bidentate ligands, the resulting complexes have only one type of bidentate ligand around the copper(II) ions. These reactions involve ligand expulsion to form the phosphate bridged complexes. All the phosphate bridged complexes 5–8 were characterized by elemental analysis, absorption spectrum, FT‐IR, ESI‐MS, and single‐crystal XRD. The molecular structures show Cu(II) in square pyramidal/trigonal bipyramidal geometry with phosphate in μ‐1,3‐bridging mode. All complexes exhibit intra‐antiferromagnetic interactions with negative J values from variable temperature magnetic susceptibility study by SQUID measurements. [ABSTRACT FROM AUTHOR]

In this study, firstly, the vibrational analysis of the bidentate coordination of the title ions to metal was theoretically performed as combined with group-theoretical analysis. In the calculation, the DFT method with B3LYP functional was used at the DEF2-TZVP level set and, cobalt, nickel, and copper were chosen as metal. As expected, the coordination of the ions to the metal atom lowered the symmetry and so, the splitting of degenerate modes occurred together with the appearance of IR inactive modes. The calculated frequencies for all the modes were given together with their symmetry species in tables. These results showed that all the splitting bands of the degenerate modes are nearly center-out, and if the intensity of degenerate mode is high the intensities of its splitting bands are also high or vice versa. Then, to compare, some metal complexes with bidentate and unidentate ligands were optimized and, their calculated frequencies were given together with their corresponding experimental data in tables. From these results, it was concluded that the vibrational frequency value of the M-O stretching mode is lower in the unidentate than in the bidentate complexes due to the decreasing of the force constant, and the splitting bands of degenerate modes are larger in the bidentate than in the unidentate complexes.

Sulphur-nitrogen(SN) donor thiosemicarbazone ligand [(Z)-N-ethyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide] and its Pt(II) complex were synthesized by condensation method. The compounds were structurally characterized by elemental analysis CHNS, FT-IR, and NMR analysis. The elemental analyses data for the compounds were in good agreement with the theoretical values. The melting point of the complex was higher than the ligand, as expected. The FT-IR spectral data reflect a bidentate bonding of thiosemicarbazone ligand to Pt(II) ion through thioketo sulfur and azomethine nitrogen. The docking results (theoretical results) of these compounds show that the binding energy between DNA and Pt(II) complex was found to be less than that of the Schiff base ligand (L) in the sense that it has higher stability at various stages and angles. The strength of docking between DNA and Pt(II) complex was also found to be that stronger than the Schiff base ligand (L).

Cisplatin (cis-diamminedichloroplatinum(II)) is a potent chemotherapeutic agent commonly used to treat cancer. However, its use also leads to serious side effects, such as nephrotoxicity, ototoxicity, and cardiotoxicity, which limit the dose that can be safely administered to patients. To minimize these problems, dendrimers may be used as carriers for cisplatin through the coordination of their terminal functional groups to platinum. Here, cisplatin was conjugated to half-generation anionic PAMAM dendrimers in mono- and bidentate forms, and their biological effects were assessed in vitro. After preparation and characterization of the metallodendrimers, their cytotoxicity was evaluated against several cancer cell lines (A2780, A2780cisR, MCF-7, and CACO-2 cells) and a non-cancer cell line (BJ cells). The results showed that all the metallodendrimers were cytotoxic and that the cytotoxicity level depended on the cell line and the type of coordination mode (mono- or bidentate). Although, in this study, a correlation between dendrimer generation (number of carried metallic fragments) and cytotoxicity could not be completely established, the monodentate coordination form of cisplatin resulted in lower IC50 values, thus revealing a more accessible cisplatin release from the dendritic scaffold. Moreover, most of the metallodendrimers were more potent than the cisplatin, especially for the A2780 and A2780cisR cell lines, which showed higher selectivity than for non-cancer cells (BJ cells). The monodentate G0.5COO(Pt(NH3)2Cl)8 and G2.5COO(Pt(NH3)2Cl)32 metallodendrimers, as well as the bidentate G2.5COO(Pt(NH3)2)16 metallodendrimer, were even more active towards the cisplatin-resistant cell line (A2780cisR cells) than the correspondent cisplatin-sensitive one (A2780 cells). Finally, the effect of the metallodendrimers on the hemolysis of human erythrocytes was neglectable, and metallodendrimers’ interaction with calf thymus DNA seemed to be stronger than that of free cisplatin.

Organotin(IV) complexes are gaining major attention as drug candidates, accordingly we have synthesized a cluster of novel diorganotin(IV) complexes R2SnClL (where R is Me, Et, n-Bu and Ph) of Schiff base ligands 2-{[4-(4-bromo-phenyl)-thiazol-2-ylimino]-methyl}-phenol (HL1), 4-{[4-(4-bromo-phenyl)-thiazol-2-ylimino]-methyl}-benzene-1,3-diol (HL2), 2-{[4-(4-bromo-phenyl)-thiazol-2-ylimino]-methyl}-4-nitro-phenol (HL3) and 2,4-dibromo-6-{[4-(4-bromo-phenyl)-thiazol-2-ylimino]-methyl}-phenol (HL4). The structural elucidation of the compounds was done by using different spectroscopic techniques (UV–Vis, FT-IR, 1H, 13C and 119Sn NMR), mass spectrometry, melting point and molar conductance measurement. The spectroscopic data recommend that Schiff bases are bidentate (NO) in nature and bind to tin metal via azomethine nitrogen, phenolic oxygen atom and have pentacoordinated environment around central tin metal. To check the biological utility, the synthesized compounds were tested for antimicrobial activity against different bacterial and fungal strains using serial dilution method and inhibitory activity noted in terms of MIC values (μmol/mL) which displayed that the complexes were more efficient than corresponding Schiff bases and complex 20 (Ph2SnClL4) was most active antimicrobial agent. The compounds were also evaluated for cytotoxic activity against human cancer cell lines- A549 (Lung), PC-3 (Prostate), MDA-MB-231 (Breast), MIA PaCa-2 (pancreas) and human normal cell line fR2 by using MTT method. The results of cytotoxic activity showed that compounds 5, 6, 7, 10, 11 and 14 are active and compounds 10 and 11 having IC50 values ranging from 0.01 to 1.42 μM are almost equally potent to the standard drug doxorubicin against all examined cell lines and are even less toxic against normal cell line. Diorganotin(IV) complexes of 4-(4-bromophenyl)thiazol-2-amine and salicylaldehyde derivatives were synthesized. Complex 20 (Ph2SnClL4) is most active antimicrobial agent, and complex 11 (Bu2SnClL2) is most efficient cytotoxic agent against tested human cancerous cell lines. [ABSTRACT FROM AUTHOR]

Complexes of La(III), Ce(III), Nd(III) and Gd(III) with mixed Ligand of 2-aminopurene and L-ascorbic acid derivative were prepared in aqueous ethanol. The two types of mixed ligand complexes [M(AA)(ADE)(H2O)2]+ and [M(IPAA) (ADE)(H2O)2]+ have been synthesized. All complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, IR, UV-VISSIBLE, NMR, ESR and Mass spectral studies. IR spectra of the complexes reveal that the complex formation occurred through both nitrogen and oxygen atoms. On the basis of electronic spectral data and magnetic susceptibility measurement octahedral geometry has been proposed for the complexes. The ESR spectral data of the M (III) complexes showed that the metal-ligand bonds have considerable covalent character. The electrochemical behaviour of mixed Ligand M(III) complexes was studied which showed that complexes of IPAA appear at more positive potential as compared to those for corresponding AA complexes. In addition, biological activity of the synthesised metal complexes against Salmonella typhi, Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae bacteria and Aspergillus niger, Aspergillus flavus, Fusarium oxisporium and Trichoderma viride fungi respectively were examined in-vitro. Some of the metal complex displayed pounced biological activity. [ABSTRACT FROM AUTHOR]

Starting from 1,2‐diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis‐acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing −SiClMe2, −SiCl2Me, −SiCl3, −B(C6F5)2, −AlBis2 (Bis=bis(trimethylsilyl)methyl) and −GaEt2 as the corresponding functional units. In all cases, the Lewis acid functionalisation was carried out twice and the products were obtained in good to excellent yields. In the case of the twofold gallium Lewis acid, a different structural motif in the form of a polymer‐like chain was observed in the solid state. All new bidentate Lewis acids were characterised by multinuclear NMR spectroscopy, CHN analysis and X‐ray diffraction experiments. [ABSTRACT FROM AUTHOR]

Wide-bandgap NiO nanoparticles (NPs) of 15 nm to 30 nm were synthesized by a facile sol–gel technique in basic medium from the precursor salt followed by calcination at 700°C. As-prepared NPs were used as an inorganic counterpart in the construction of sulfonic-acid-functionalized porphyrin (SAP)-based dye-sensitized solar cells (DSSCs). The procedure involved adsorption of SAP on NiO NPs by thoroughly mixing SAP aqueous solution with a suspension of NiO NPs for 18 h at room temperature. Successful chemisorption of SAP on NiO NPs was confirmed by Fourier-transform infrared, ultraviolet–visible absorption, and fluorescence emission spectroscopy. The fabricated nanohybrid assembly presented incident photon to current conversion efficiency of up to 0.2% for the optimum mixing composition of 30 µL SAP with 0.25 mg/mL NiO NPs in deionized water. The facile and ultrasafe nanofabrication method described herein represents a progressive step towards sustainable DSSC research. [ABSTRACT FROM AUTHOR]

A series of transition metal (II) complexes with general formula [M(L1−4)2(H2O)2] (where M = Co(II), Ni(II), Cu(II) and Zn(II)) was synthesized by the reaction of metal(II) acetates with hydrazones [HL1–HL4] obtained from condensation of tetralone with hydrazide derivatives. The characterization of synthesized compounds (1–20) was done by using elemental analysis, different spectral studies (UV–Vis, 1H NMR, 13C NMR, FT-IR, mass, ESR and fluorescence), magnetic susceptibility, molar conductance measurement and thermal (DTA, TGA and DTG) analysis. The characterization results suggested the bidentate nature of the hydrazones, which chelate with the metal ion via nitrogen of (C=N) group and deprotonated carbonyl oxygen in the enolized form, resulting in stable, non-volatile octahedral complexes. The antimicrobial potential of the compounds was evaluated against four bacterial, i.e. (S. aureus, B. subtilis, P. aeruginosa and E. coli), and two fungal species, i.e. (A. niger and C. albicans), by a serial dilution method with complexes 15 and 16 as most active compounds against microbes. All the compounds were also tested for its cytotoxicity (in vitro) against three human cancer cell lines (A549, HeLa and MCF-7) and one normal cell line (L6) by the MTT assay, which focussed on an increased activity of compounds 7 and 15 towards A549, MCF-7 and HeLa cancer cell line with IC50 values ranging from 10.76 to 16.42 μg/mL, and compounds were found to be non-toxic towards L6 cell line as compared to the standard drug doxorubicin. The results demonstrated that complexation enhanced the biological activity of compounds. The synthesized compounds (1–20) were screened for antitumor activities against A549, MCF7, Hela cancer cell lines. Copper complex (7) and (15) was found to be the most active antitumor agent and less toxic against L6—Rat myoblast normal cell line than standard doxorubicin. [ABSTRACT FROM AUTHOR]

In this article, a series of coordination complexes of Co(II), Ni(II), Cu(II) and Zn(II) metals were prepared by four novel Schiff base ligands (E)-N'-(4-(prop-2-yn-1-yloxy)benzylidene)benzohydrazide (HL1), (E)-4-chloro-N'-(4-(prop-2-yn-1-yloxy)benzylidene)benzohydrazide (HL2), (E)-N'-((2-(benzyloxy)naphthalen-1-yl)methylene)benzohydrazide (HL3), (E)-N'-((2-(benzyloxy)naphthalen-1-yl)methylene)-4-chlorobenzohydrazide (HL4) obtained by the condensation reaction of benzoic acid hydrazide/4-chloro benzoic acid hydrazide with oxy derivatives of 2-hydroxy-1-napthaldehyde/4-hydroxy benzaldehyde. The proposed structure of the complexes have been established by spectroscopic and analytical techniques like C, H, N and metal analysis, FT-IR, 1H and 13C NMR, mass, UV-Vis, EPR, fluorescence, molar conductance, magnetic susceptibility and TGA which concluded that Schiff bases act as bidentate NO donor ligands coordinating through nitrogen atom of azomethine linkage and uninegative oxygen atom of carbonyl group in enolic form and resulting in complexes of the type [M(L1–4)·(CH3COO)·3H2O] in 1:1 molar ratio. The synthesized compounds were screened for their in vitro antimicrobial activities against two gram +ve bacteria i.e. S. aureus and S. gordonii; two gram -ve bacteria i.e. E. coli and P. aeruginosa and two fungal strains i.e. A. niger and C. albicans and found that metal chelates were more noxious than their parent Schiff bases. The copper(II) complex 19 was found to be the highest noxious antimicrobial active compound. The compounds were also assessed for their antioxidant activity and found that the complexes are more potent and show excellent efficiency in decolorizing the DPPH purple colored solution than their free ligands. The complexes 6, 7, 10, 11, 14, 15, 18, 19 were found to be excellent antioxidants and copper(II) complexes were the most potent antioxidant compounds with lowest IC50 values (2.04–2.56 µM)) among all the tested compounds. Total 20 compounds of Schiff bases transition metal complexes were synthesized and characterized. The copper complex (19) was found to be highest antimicrobial against Streptococcus gordonii, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Candida albicans. The copper(II) complex (11) exhibits outstanding and highest antioxidant activity (IC50= 2.04 µM). [ABSTRACT FROM AUTHOR]

We report an air-stable bisboron complex as an efficient catalyst for the inverse electron-demand Diels–Alder (IEDDA) reaction of 1,2-diazine as well as 1,2,4,5-tetrazine. Its stability towards air and moisture was demonstrated by NMR studies enabling its application in organic transformations without glovebox. A one-pot procedure for its synthesis was developed starting from 1,2-bis(trimethylsilyl)benzene greatly enhancing its practicality. Comparative reactions were carried out to evaluate its catalytic activity in IEDDA reactions of diazine including phthalazine as well as 1,2,4,5-tetrazine.

Considering the importance of silylene ligands in transition metal‐mediated catalytic reactions, we have scrutinized eight novel monodentate (1–4) and bidentate (1′‐4′) derivatives of 2,5‐diX‐cyclopentasilylene‐2,4‐dienes (X = NH2, OH, PH2, and SH), at M06/6‐311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom (1Rh‐4Rh and 1′Rh‐4′Rh, respectively), thermodynamic and structural parameters such as complexation energy (ΔECom), singlet‐triplet energy gap (ΔEs‐t), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH2 > OH > PH2 > SH), the σ‐donor strength and ligand flexibility increase. Structures 1 and 1′ turn out as the most nucleophilic species for showing the highest nucleophilicity (N = 5.47 and 5.40 eV, respectively). Furthermore, they exhibit the highest proton affinity values (PA = 271.46 and 271.23 kcal/mol, respectively). The results indicate that bidentate coordination mode of silylene leads to a stronger Si‐Rh complex. The overall orders of σ‐donation ability for monodentate and bidentate silylene ligands are 1 > 2 > 3 > 4 and 1′ > 2′ > 3′ > 4′, respectively. [ABSTRACT FROM AUTHOR]

Three organotin (IV) derivatives PhPO3HSnBu2Cl, SnBu2Ph2PO2Cl3/2H2O, Sn(PhPO3)Cl22H2O obtained on allowing PhPO3H2 or propylammonium PhPO3H to react with SnBu2Cl2, SnCl22H2O and two adducts [(C6H5CH2)2NH2]3O2C(CH2)2PO33SnPh3Cl, [CyNH3(HO2POCH2-N(CH2CO2H)2]2 3SnCl4.2H2ONH4Cl obtained on allowing (C6H5CH2)NH2)3O2C(CH2)2PO3 or [CyNH3(HO2POCH2-N(CH2 CO2H)2]2 and SnPh3Cl or SnCl22H2O to react in ethanolic media have been characterized by elemental analyses, infrared and Mossbauer techniques. The suggested structures, while considering the anionic counterpart, are discrete, dimeric, double and triple metallic components or of infinite chain types, the anion behaving as a monochelating, a bichelating or a bidentate ligand. In OH containing structures, when extra hydrogen bonds are considered, supramolecular architectures may be obtained. [ABSTRACT FROM AUTHOR]

It has recently been proposed that recalcitrant dissolved organic carbon (DOC) in groundwater plays a potent etiological role in the peculiar distribution of chronic kidney disease of unknown etiology (CKDu). This study aims to elucidate the interactions of Ca2+ and SO 4 2− with a model organic fraction of humic acid (SHA) to determine the possible relationship of CKDu incidence with the DOC in drinking water. XPS and FT-IR methods respectively determined the surface functional groups and chemical composition of protonated dissolved organic carbon (HDOC) in a CKDu high-risk zone (HR) of Sri Lanka and in SHA. Higher surface C composition (87.9%) and lower O (11.4%) were observed for HDOC from the HR region than for SHA (C: 73.8%, O: 24.7%). Aromatic C with less O-containing functional groups was observed in HDOC. The IR band at 1170 cm−1 confirms the formation of organic sulfonate (C–SO 3 -) on SHA. A band at 1213 cm−1 due to organic sulfonate in HDOC from the CKDu HR region was also identified. The IR band at 866 cm−1 evidenced the formation of CaCO 3 on SHA above pH 7.4. XPS data confirmed the presence of sulfur oxidation states corresponding to SO 3 2− and SO 4 2− at 168.9 eV and 170.1 eV binding energies, respectively. The binding energies at 347 eV and 351 eV for Ca 2p 3/2 and Ca 2p 1/2 eV, respectively, confirmed the bidentate complexation of Ca2+ with COO− and sulfonate groups on SHA. The organic sulfonate formed is postulated as a uremic toxicant. Image 1 [ABSTRACT FROM AUTHOR]

Copper-catalyzed and organocopper-involved reactions are of great significance in organic synthesis. To have a deep understanding of the reaction mechanisms, the structural characterizations of organocopper intermediates become indispensable. Meanwhile, the structure-function relationship of organocopper compounds could advance the rational design and development of new Cu-based reactions and organocopper reagents. Compared to the mono-carbonic ligand, the C,N- and C,C-bidentate ligands better stabilize unstable organocopper compounds. Bidentate ligands can chelate to the same copper atom via η2-mode, forming a mono-cupra-cyclic compounds with at least one acute C-Cu-C angle. When the bidentate ligands bind to two copper atoms via η1-mode at each coordinating site, the bimetallic macrocyclic compounds will form nearly linear C-Cu-C angles. The anionic coordinating sites of the bidentate ligand can also bridge two metals via μ2-mode, forming organocopper aggregates with Cu-Cu interactions and organocuprates with contact ion pair structures. The reaction chemistry of some selected organocopper compounds is highlighted, showing their unique structure–reactivity relationships.

In the title compound, [Mo(C10H12N2O)(CO)4], the molybdenum(0) center is surrounded by a bidentate diimine [4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline] and four carbonyl ligands in a distorted octahedral coordination geometry. The diimine ligand coordinates via the two nitrogen atoms.

1,1′-Biisoquinolines are a class of bidentate nitrogen donor ligands in the heterocyclic diimine family. This review briefly discusses their properties and the key synthetic pathways available and then concentrates upon their coordination behaviour. The ligands are of interest as they exhibit the phenomenon of atropisomerism (hindered rotation about the C1–C1′ bond). A notation for depicting the stereochemistry in coordination compounds containing multiple stereogenic centers is developed. The consequences of the chirality within the ligand on the coordination behaviour is discussed in detail.

Five Ru(II)‐NC complexes were tested as catalysts for α‐alkylation of unactivated amides using alcohols as alkylating agents, and complex {(C5H4N)‐(C6H4)}RuCl(CO)(PPh3)2 (1) showed the highest activity. With 0.5 mol% catalyst loading, a series of α‐alkylated amides were isolated at 80 °C within 6 hours. Furthermore, under similar conditions, complex 1 was also active for α‐alkylation of unactivated esters with alcohols, and the reaction time was shortened to 1.5 hours. The catalytic performance of 1 is comparable to the best reported catalyst. [ABSTRACT FROM AUTHOR]

Abstract Influenza A virus carries hundreds of trimeric hemagglutinin (HA) proteins on its viral envelope that interact with various sialylated glycans on a host cell. This interaction represents a multivalent binding event that is present in all the current receptor binding assays, including those employing viruses or precomplexed HA trimers. To study the nature of such multivalent binding events, we fused a superfolder green fluorescent protein (sfGFP) to the C-terminus of trimeric HA to allow for direct visualization of HA–receptor interactions without the need for additional fluorescent antibodies. The multivalent binding of the HA–sfGFP proteins was studied using glycan arrays and tissue staining. The HA–sfGFP with human-type receptor specificity was able to bind to a glycan array as the free trimer. In contrast, the HA–sfGFP with avian-type receptor specificity required multimerization by antibodies before binding to glycans on the glycan array could be observed. Interestingly, multimerization was not required for binding to tissues. The array data may be explained by the possible bivalent binding mode of a single human-specific HA trimer to complex branched N-glycans, which is not possible for the avian-specific HA due to geometrical constrains of the binding sites. The fact that this specificity pattern changes upon interaction with a cell surface probably represents the enhanced amount of glycan orientations and variable densities versus those on the glycan array. Graphical abstract Unlabelled Image Highlights • Human-type HA proteins use bidentate binding to attach to branched N-glycans. • Avian-type HA proteins require HA multimerization to bind to avian-type receptors in a glycan-array format. • Avian-type HA proteins can interact as a single trimer with avian-type receptors on the surface of respiratory tissue. [ABSTRACT FROM AUTHOR]

Six new tin (IV), antimony (III) and antimony (V) adducts and complexes have been synthesized. Discrete structures were suggested on the basis of infrared data. Within the structures, the anion behaves as a bidentate, monochelating and monodentate, monodentate and tri O-chelating ligand. The environments around metallic centres are octahedral. Considering preamble of extra hydrogen bonds in compounds containing water molecules and/or OH groups, supramolecular architectures may be given rise. [ABSTRACT FROM AUTHOR]

C 6 H 5 Se - Na + (generated in-situ by NaBH 4 reduction of (C 6 H 5 Se) 2 ) on reaction with bromo benzylacetate under N 2 atmosphere results in the formation of phenylseleno benzylacetate ( L ) as viscous oil. Its complexes having the formula [ZnCl 2 (L)] ( 1 ), [CdCl 2 (L)] ( 2 ), [HgCl 2 (L)] ( 3) have been prepared. L and its complexes 1 – 3 were characterized on the basis of physico-chemical and spectral (FT-IR, Mass, 1 H, 13 C, DEPT 135° and 77 Se NMR) studies. Powder XRD diffraction pattern revealed the crystalline nature of ligand and complexes 1–3 . Heteroditopic ligand L (Se, O) ligates solely through Se and O in complexes 1–3 and adopts bidentate mode of coordination. Using DFT-based optimization of structures, bond length, bond angle, HOMO-LUMO energy gaps and molecular electrostatic potential maps (MEP) of L and complexes 1–3 were theoretically calculated at the B3LYP/LANL2DZ level of theory. HOMO-LUMO energy gap was calculated which allowed the calculation of relative properties like chemical hardness, chemical inertness, chemical potential, nucleophilicity and electrophilicity index of the synthesized products. Experimentally obtained results (IR and NMR) showed a good correlation with those of the theoretical ones. [ABSTRACT FROM AUTHOR]

Nine new molybdato adducts and complexes have been synthesized and studied by infrared spectroscopy. The suggested structures are discrete or infinite chain, the molybdate behaving as a bidentate, mono-, bi- or tetrachelating ligand, the environment around the tin (IV) centre being octahedral or trigonal bipyramidal. In water containing compounds, when extra intermolecular O-H…O or O-H…Cl hydrogen bonds are considered, supramolecular architectures may be obtained.

On allowing PhPO3H2 to react with SnPh3Cl in ethanolic media, OC[OPOSnPh3OEt]2 is obtained by cetonization, desarylation and esterification, has been studied by infrared technic. A discrete structure has been suggested on the basis of infrared data, the anion behaving as a bidentate ligand, the environment around the tin centres being tertrahedral.

Co0.7Zn0.3Fe2O4 nanorods were synthesized from hydrazine precursor by co-precipitation technique. Infrared and thermogravimetric-differential thermogravimetric curves of the precursor indicated the bridging bidentate nature of hydrazine and three-step thermal decomposition. The as-synthesized cobalt zinc ferrite nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, vibrating sample magnetometry and UV-diffuse reflection spectroscopy which proposed the phase structure, morphology, magnetic and optical properties. Co0.7Zn0.3Fe2O4 nanorods showed a sensible photocatalytic activity on Congo red, Malachite green, Methylene blue, Methyl red, Rhodamine B and Rose bengal under solar light at different time intervals and were magnetically separated. [ABSTRACT FROM AUTHOR]

The reaction of the potentially bidentate ambidentate N,O-donor ligands 3-hydroxy-2-pyridinecarboxylic acid (Hhpc) and 3-hydroxy-2-(hydroxymethyl)pyridine (Hhhp) with trans-[ReOCl3(PPh3)2] led to the isolation of the products [ReOCl(hpc)2] (1) (from acetonitrile) and [ReOCl2(hhp)(PPh3)] (2) (from ethanol) respectively. In both complexes hpc and hhp are coordinated as bidentate N,O-donor chelates, rather than as O,O-donor ligands. From the reaction of [Re(CO)5Cl] and Hhhp·HCl in ethanol the neutral complex fac-[Re(CO)3Cl(Hhhp)] (3) was obtained, with N,O-coordination of Hhhp. Complex 1 crystallizes in the monoclinic space group P21/n with a = 6.8782(3), b = 20.0647(8), c = 10.8692(4) Å, β = 107.545(1)°, and Z = 4. Complex 2 crystallizes in the triclinic space group P-1 with a = 7.3523(4), b = 8.1047(5), c = 19.591(1) Å, α = 91.133(2)°, β = 93.656(2)°, γ = 93.074(2)° and Z = 2. Complex 3 has monoclinic P21/c symmetry with the cell parameters a = 10.6452(5), b = 11.1372(5), c = 9.7229(5) Å, β = 106.107(2)°, and Z = 4.Graphical Abstract: The reaction of the potentially bidentate ambidentate N,O-donor ligands 3-hydroxy-2-pyridinecarboxylic acid (Hhpc) and 3-hydroxy-2-(hydroxymethyl)pyridine (Hhhp) with trans-[ReOCl3(PPh3)2] led to the isolation of the products [ReOCl(hpc)2] (from acetonitrile) and [ReOCl2(hhp)(PPh3)] (from ethanol) respectively. In both complexes hpc and hhp are coordinated as bidentate N,O-donor chelates, rather than as O,O-donor ligands. From the reaction of [Re(CO)5Cl] and Hhhp·HCl in ethanol the neutral complex fac-[Re(CO)3Cl(Hhhp)] was obtained, with N,O-coordination of Hhhp. Spectroscopic data and the X-ray crystal structures of the complexes are reported. [ABSTRACT FROM AUTHOR]

C6H5Se−Na+ (generated in situ by NaBH4 reduction of (C6H5Se)2) on reaction with ClC3H6C4H8N2ClC6H5 under N2 atmosphere results in C6H5SeC3H6C4H8N2ClC6H5 (L) as a cream-colored solid. Its 1:1 metal complexes having the general formula [MLX2], where M = Zn, Cd, Hg, and X = Cl, have been prepared. Ligand L and its complexes 1-3 are characterized on the basis of physico-chemical and spectral (FT-IR, ESI Mass, 1H, 13C, DEPT 135° 13C {1H}, and 77Se{1H} NMR) studies. IR spectroscopy revealed that L is coordinated solely through selenium and nitrogen to zinc, cadmium, and mercury ions forming a six-membered chelate ring around M(II) ions. Elemental analysis measurements along with 1H, 13C, DEPT 135° 13C {1H}, and ESI-mass data also confirm the bidentate coordination mode of the ligand. Moreover, the coordination from selenium atom is also supported by the downfield shift of signal in 77Se{1H} NMR spectroscopy. Using DFT-based optimization of structures, the HOMO-LUMO energy gaps and molecular electrostatic potential surface of ligand L and complexes 1-3 were theoretically calculated at the B3LYP/LANL2DZ level of theory. Ligand L and complexes 1-3 display significant antibacterial and antifungal activity. [ABSTRACT FROM AUTHOR]

C6H11S‐Na+ (generated insitu by reaction of NaOH with C6H11SH) on treatment with 1‐(2‐chloroethyl) piperidine hydrochloride under N2 atmosphere resulted in (1‐(2‐cyclohexyl thioethyl) piperidine) (L1) as orange solid. It's complexes having the formula [ZnCl2. L1] (1), [CdCl2. (L1)] (2) and [HgCl2. L1] (3) have been prepared. L1 and its complexes 1‐3 were characterized on the basis of physico‐chemical and spectral (FT‐IR, Mass, 1H, 13C and DEPT 135o NMR) studies. Powder XRD diffraction pattern reveals the crystalline nature of L1 and complex 1. Complexes 1‐3 adopt distorted tetrahedral geometry showing bidentate mode of coordination through S and N. Using DFT‐based optimization of structures, the HOMO‐LUMO energy gaps and molecular electrostatic potential maps (EPM) of compound L1 and complexes 1‐3 were theoretically calculated at the B3LYP/6‐311G (d, p) level of theory. HOMO‐LUMO energy gap was calculated which allowed the calculation of relative properties like chemical hardness, chemical inertness, chemical potential, nucleophilicity and electrophillicity index of the synthesized products. The experimentally obtained IR and NMR results showed a good correlation with those of the theoretical ones. Ligand L1 and complexes 1‐3 display significant antibacterial and antifungal activity. [ABSTRACT FROM AUTHOR]

A flexible bis(pyridylurea) ligand, 1,1′-[oxybis(2,1-phenylene)] bis(3-pyridin-3-ylurea) (L), has been synthesized and characterized. The interaction of L with ZnCl 2 and CdCl 2 has been investigated. In the structure of {[ZnLCl 2 ]·2DMF} n ( 1 ), the flexible ligands bridge the Zn II centers to form 1D helical chains with a pitch of 9.743 Å. The P and M helical chains are arranged equally, and the whole complex 1 is racemic. In the structure of [CdLCl 2 (DMF)] n ( 2 ), the flexible ligands bridge Cd II centers to form one-dimensional P and M helical chain structures in a similar manner. Then the chlorine atoms act as bridges in bidentate modes linking the P helical chain with M helical chain to form a 1D looped chain coordination polymer. [ABSTRACT FROM AUTHOR]

Manganese(II) complexes having the general composition Mn(L)2X2 (where L = 3‐bromoacetophenone semicarbazone, 3‐bromoacetophenone thiosemicarbazone, 1‐tetralone semicarbazone, 1‐tetralone thiosemicarbazone, flavanone semicarbazone or flavanone thiosemicarbazone and X = Cl− or ½SO42−) were synthesized. All the complexes were characterized using elemental analyses, molar conductance and magnetic moment measurements, and mass, 1H NMR, infrared, electron paramagnetic resonance and electronic spectral studies. The molar conductance of the complexes in dimethylsulfoxide lies in the range 10–20 Ω−1 cm2 mol−1 indicating their non‐electrolytic nature. All the complexes show magnetic moments corresponding to five unpaired electrons. The possible geometries of the complexes were assigned on the basis of electron paramagnetic resonance, electronic and infrared spectral studies. Some of the synthesized ligands and their complexes were screened for their antifungal activities against fungi Macrophomina phaseolina, Botrytis cinerea and Phoma glomerata using the food poison technique and their antibacterial activities against Xanthomonas campestris pv. campestris and Ralstonia solanacearum using the paper disc diffusion method. They showed appreciable activities. [ABSTRACT FROM AUTHOR]

The synthesis of homoleptic five-coordinate heteroaryl tin(IV) compounds using three chiral N-heterocyclic substituents, 2-(1-aminoethyl)benzimidazole (1), 2-(pyrrolidin-2-yl) benzimidazole (2) and 2-(1-amino-2-mercaptopropylyl)benzimidazole (3) ligands is described. It has been found that ligands 1 and 2 behave in the bidentate N,N donor fashion, however, ligand 3 behave in the bidentate N, S donor. Overall ligands furnished, with moderate yields, their corresponding complexes [(CH3)2Sn(C9H10N3)Cl] (4), [(CH3)2Sn(C9H12N3)Cl] (5) and [(CH3)2Sn(C9H10N3S)Cl] (6). The characterization of all compounds by various spectroscopic methods UV-Vis, FT-IR, NMR, RX and elemental analyses provided insights into the diversity of complex formation. [ABSTRACT FROM AUTHOR]

Eleven complexes and adduct have been synthesized and studied by infrared. The suggested structures are discrete with tetrahedral, trigonal bipyramidal, square planar or octahedral environments around Zn, Ni, Hg and Cu centres - the coordination number is eight in the yttrium compound and ten in the dysprosium one-. The maleate anion behaves as a bidentate, a monochelating, a bichelating or a tetradentate ligand while the formiate anion behaves as a monodentate ligand. For compounds containing a protonated amine or a methanol molecule, when hydrogen bonds are considered a supramolecular architecture may be obtained. [ABSTRACT FROM AUTHOR]

A new symmetrical bidentate Schiff base ligand (L) was applied for the synthesis of some new cadmium coordination compounds with general formula of [Cd(L)X2] in which X is halide and pseudo-halide. The ligand and all cadmium complexes were characterized by some techniques such as elemental analysis, FT-IR, 1H, 13C NMR, UV-Visible and molar conductance. Electrochemical behavior of ligand and Cd(II) complexes were investigated by cyclic voltammetry method. Morphology and shape of [Cd(L)Cl2] particles were depicted by SEM. Antimicrobial properties such as antibacterial and antifungal activities of the complexes as compared with ligand were checked against three Gram-negative bacteria; Escherichia coli (ATCC 25922), Pseudomunase aeroginosa (ATCC 9027) and Salmonella Spp. and two Gram-positive bacteria; Staphylococcus aureus (ATCC 6538) and Corynebacterium renale and three fungal strains including Aspergillus Niger, Penicillium chrysogenum and Candida albicans. The results revealed appropriate antibacterial and antifungal activities for all compounds, and it was also found that the coordination of ligand to Cd (II) lead to an increase in the antimicrobial activities in most of cases.

Previous work has demonstrated that a bidentate receptor containing a pair of Sn atoms can engage in very strong interactions with halide ions via tetrel bonds. The question that is addressed here concerns the possibility that a receptor of this type might be designed that would preferentially bind a polyatomic over a monatomic anion since the former might better span the distance between the two Sn atoms. The binding of Cl− was thus compared to that of HCOO−, HSO4−, and H2PO4− with a wide variety of bidentate receptors. A pair of SnFH2 groups, as strong tetrel-binding agents, were first added to a phenyl ring in ortho, meta, and para arrangements. These same groups were also added in 1,3 and 1,4 positions of an aliphatic cyclohexyl ring. The tetrel-bonding groups were placed at the termini of (-C≡C-)n (n = 1,2) extending arms so as to further separate the two Sn atoms. Finally, the Sn atoms were incorporated directly into an eight-membered ring, rather than as appendages. The ordering of the binding energetics follows the HCO2− > Cl− > H2PO4− > HSO4− general pattern, with some variations in selected systems. The tetrel bonding is strong enough that in most cases, it engenders internal deformations within the receptors that allow them to engage in bidentate bonding, even for the monatomic chloride, which mutes any effects of a long Sn···Sn distance within the receptor.

Me4NO2C-SO3H.2SnPh3Cl and enH2O2C-SO3.SnPh3Cl are obtained on allowing Me4NO2C-SO3H and enH2O2C-SO3 to react with SnPh3Cl in respectively mixed solution (ethanol/water) or ethanolic solution in specific ratios. Their infrared studies have been carried out and structures as dimers, suggested when hydrogen bonds are involved.