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A series of bench-stable Co(II) complexes containing hydrazone Schiff base ligands were evaluated in terms of their activity and selectivity in carbon-carbon multiple bond transfer hydrogenation. These cobalt complexes, especially a Co(II) precatalyst bearing pyridine-2-yl-N(Me)N=C-(1-methyl)imidazole-2-yl ligand, activated by LiHBEt3, were successfully used in the transfer hydrogenation of substituted styrenes and phenylacetylenes with ammonia borane as a hydrogen source. Key advantages of the reported catalytic system include mild reaction conditions, high selectivity and tolerance to functional groups of substrates. [ABSTRACT FROM AUTHOR]

Boron complexes with Schiff‐base [4]helicene ligands were synthesized. These complexes were characterized by NMR spectroscopy and their helical molecular structures were unequivocally established by X‐ray diffraction (XRD) analysis. The helical boron complexes exhibited efficient photoluminescence under UV irradiation, and the circularly polarized luminescence (CPL) properties were investigated for optically pure samples. Density functional theory (DFT) calculations were conducted to further understand their photophysical properties including chiroptical responses. [ABSTRACT FROM AUTHOR]

Two new nickel(II) and cobalt(II) complexes, [Ni(MPAFA)3](BF4)2 (I) and [Co(MPAFA)3](BF4)2 (II) were synthesized from a pyrazole containing 'NN' bidentate Schiff-base ligand, N-(furan-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPAFA) (L). The complexes I and II were characterized by various physico-chemical and spectral parameters. Both I and II were 1:3 (M:L) coordination complexes and behaving as 1:2 electrolytes. Single crystal X-ray diffraction studies revealed that both of them were distorted octahedral in nature with a N6 donor set. The binding interactions of the complexes with CT-DNA were studied by UV-Vis and fluorescence spectroscopic methods. I was found to bind with CT-DNA in a partial intercalative mode, whereas II bound via the groove-like manner in solutions. The ligand and the complexes were shown to have potential photocatalytic activity in degrading methylene-blue (MB) under UV-Vis light irradiation. [ABSTRACT FROM AUTHOR]

ABSTRACT: Mononuclear complex of composition [ZnII(L)].2H2O (1) (H2L = 2-((Z)-(2-(2-(2-((Z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino)phenoxy)ethoxy)phenylimino)methyl)-4,6-di-tert‑butylphenol) has been synthesized and characterized. In the complex 1, the ZnII at the center is coordinated by two imine nitrogen atoms, two phenolate oxygen atoms and one ether oxygen atom from the ligand, resulting in a distorted square-pyramidal ZnN2O3 coordination geometry. Complex 1 is photoluminescence active with stokes shift of 115 nm. Geometrical parameters were computed using the Density Functional Theory (DFT) method, specifically B3LYP, with the 6–311G++(d,p) basis sets. The charge distribution within the molecule was visualized through Molecular Electrostatic Potential (MEP) surface analysis. The energy levels of the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) were determined that revealing substantial charge transfer within the molecule. Hirshfeld surface analysis was conducted in both three-dimensional (3D) and two-dimensional (2D) perspectives to investigate the electron distribution on the molecular surface. The Electron Localization Function (ELF) Figure was utilized to investigate the degree of relative electron localization within the molecule. Moreover, a Fukui functional analysis was employed to identify potential sites for chemical attack by different substituents. The process involved in the creation of the molecular electrostatic potential (MEP), followed by the generation of a three-dimensional color-coded visualization to emphasize reactive areas. In the realm of biological investigation, four separate receptors such as 5HL1, 8BSK, 6UJM and 6UL9 were utilized for molecular docking analyses. These analyses aimed to evaluate interactions between ligands and proteins, as well as to uncover potential resemblances among drugs.

In this work, the synthesis and structure of an antimony complex with an aromatic, asymmetric tridentate ligand without an Sb-C bond were studied. Ethoxy(2-salicylidenaminophenolato)antimony(III) was studied with NMR, UV-Vis, and IR spectroscopy and the molecular structure was determined by single crystal X-ray diffraction. The antimony atom is formally tetracoordinate in this molecule. Coordinative unsaturation becomes visible in the solid-state structure where intermolecular Sb...O interactions supplement the coordination sphere of the antimony atom to be hexacoordinated. Quantum chemical calculations were performed in order to obtain a better understanding of the bond properties in the antimony complex. These show a spherical distribution of the lone pair at antimony and polar shared bonds from antimony to the heteroatoms of the tridentate ligand. [ABSTRACT FROM AUTHOR]

The title compound, C28H23NO4Si, crystallizes in the monoclinic space group P21/c. The silicon complex consists of a tridentate dinegative Schiff base ligand bound to a diphenylsilyl unit. The coordination geometry of the pentacoordinate silicon atom is a distorted trigonal bipyramid.

The organic–inorganic lead halide hybrids comprising semiconducting perovskite components and organic modules have proven to be promising candidates for optoelectronic applications. The modulation of the inorganic components as optical centres by diverse organic cationic templates is under intense investigation. Herein, we successfully prepared new one-dimensional lead halide hybrid perovskites [L1]2n[Pb2Cl6]n∞·nH2O (1) and [PbBr2(L2)]n∞·0.5nH2O (2), and the dimeric complex [PbBr2(L3)]2 (3) in water media. In 1, 2-(2-hydroxyethyl)-2H-imidazo[1,5-a]pyridinium cation [L1]+ resulted from the oxidative condensation–cyclization between formaldehyde, ethanolamine and 2-pyridinecarbaldehyde (2-PCA); the polydentate Schiff base ligands L2 and L3 formed in the in situ condensation of 2-PCA and ethanolamine or ethylenediamine, respectively. The lead chloride hybrid 1 contains the previously unreported type of a [Pb2Cl6]∞ double chain constructed from three-edge- and five-edge-sharing PbCl6 octahedra, and cations forming π-bonded stacks aligned along the inorganic wires. In the crystal of 2, pairs of the double-side organically decorated [PbBr2(L2)]∞ chains built of corner-sharing PbBr3N2O octahedra arrange hydrophilic channels to host water molecules. In the solid state, the identically stacked dimers of 3 form columns parallel to the ab plane with the Pb2Br4 moieties in the column being strictly coplanar. Hirshfeld surface analysis was used to rationalize the packing patterns through hydrogen bonds of O−H···O/Cl and C−H···O/Cl types with the involvement of OH groups of [L1]+, L2 and water molecules in 1 and 2, as well as C–H∙∙∙Br hydrogen bonding in 2 and 3. The QTAIM analysis of non-covalent interactions in 1–3 was performed. According to the analysis of the solid-state UV–visible reflectance spectra by a Tauc plot, the optical band gap values of 1, 2 and 3 as direct gap semiconductors were estimated to be 3.36, 3.13 and 2.96 eV, respectively. [ABSTRACT FROM AUTHOR]

In this work, the synthesis and structure of an antimony complex with an aromatic, asymmetric tridentate ligand without an Sb-C bond were studied. Ethoxy(2-salicylidenaminophenolato)antimony(III) was studied with NMR, UV-Vis, and IR spectroscopy and the molecular structure was determined by single crystal X-ray diffraction. The antimony atom is formally tetracoordinate in this molecule. Coordinative unsaturation becomes visible in the solid-state structure where intermolecular Sb…O interactions supplement the coordination sphere of the antimony atom to be hexacoordinated. Quantum chemical calculations were performed in order to obtain a better understanding of the bond properties in the antimony complex. These show a spherical distribution of the lone pair at antimony and polar shared bonds from antimony to the heteroatoms of the tridentate ligand.

A mixed-valent trinuclear complex with 1,3-bis(5-chlorosalicylideneamino)-2-propanol (H3clsalpr) was synthesized, and the crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. The molecule is a trinuclear CoIII-CoII-CoIII complex with octahedral geometries, having a tetradentate chelate of the Schiff-base ligand, bridging acetate, monodentate acetate coordination to each terminal Co3+ ion and four bridging phenoxido-oxygen of two Schiff-base ligands, and two bridging acetate-oxygen atoms for the central Co2+ ion. The electronic spectral feature is consistent with the mixed valent CoIII-CoII-CoIII. Variable-temperature magnetic susceptibility data could be analyzed by consideration of the axial distortion of the central Co2+ ion with the parameters Δ = –254 cm−1, λ = –58 cm−1, κ = 0.93, tip = 0.00436 cm3 mol−1, θ = –0.469 K, gz = 6.90, and gx = 2.64, in accordance with a large anisotropy. The cyclic voltammogram showed an irreversible reduction wave at approximately −1.2 V·vs. Fc/Fc+, assignable to the reduction of the terminal Co3+ ions. [ABSTRACT FROM AUTHOR]

The organic–inorganic lead halide hybrids comprising semiconducting perovskite components and organic modules have proven to be promising candidates for optoelectronic applications. The modulation of the inorganic components as optical centres by diverse organic cationic templates is under intense investigation. Herein, we successfully prepared new one-dimensional lead halide hybrid perovskites [L1]2n[Pb2Cl6]n∞·nH2O (1) and [PbBr2(L2)]n∞·0.5nH2O (2), and the dimeric complex [PbBr2(L3)]2 (3) in water media. In 1, 2-(2-hydroxyethyl)-2H-imidazo[1,5-a]pyridinium cation [L1]+ resulted from the oxidative condensation–cyclization between formaldehyde, ethanolamine and 2-pyridinecarbaldehyde (2-PCA); the polydentate Schiff base ligands L2 and L3 formed in the in situ condensation of 2-PCA and ethanolamine or ethylenediamine, respectively. The lead chloride hybrid 1 contains the previously unreported type of a [Pb2Cl6]∞ double chain constructed from three-edge- and five-edge-sharing PbCl6 octahedra, and cations forming π-bonded stacks aligned along the inorganic wires. In the crystal of 2, pairs of the double-side organically decorated [PbBr2(L2)]∞ chains built of corner-sharing PbBr3N2O octahedra arrange hydrophilic channels to host water molecules. In the solid state, the identically stacked dimers of 3 form columns parallel to the ab plane with the Pb2Br4 moieties in the column being strictly coplanar. Hirshfeld surface analysis was used to rationalize the packing patterns through hydrogen bonds of O−H···O/Cl and C−H···O/Cl types with the involvement of OH groups of [L1]+, L2 and water molecules in 1 and 2, as well as C–H∙∙∙Br hydrogen bonding in 2 and 3. The QTAIM analysis of non-covalent interactions in 1–3 was performed. According to the analysis of the solid-state UV–visible reflectance spectra by a Tauc plot, the optical band gap values of 1, 2 and 3 as direct gap semiconductors were estimated to be 3.36, 3.13 and 2.96 eV, respectively.

Two polymorphic FeII coordination polymers [FeIIL (TPPE)0.5] 1) and [(FeII3L3 (TPPE)1.5)] 2), were obtained from a redox-active tetrathiafulvalene (TTF) functionalized ligand [H2L = 2,2’-(((2-(4,5-bis-(methylthio)-1,3-dithiol-2-ylidene)benzo(d) (1,3) dithiole-5,6-diyl)bis-(azanediyl))bis-(meth anylylidene)) (2E,2E')-bis(3-oxobutanoate)] and a highly luminescent connector {TPPE = 1,1,2,2-tetrakis[4-(pyridine-4-yl)phenyl]-ethene}. Complex 1 has a layered structure where the TPPE uses its four diverging pyridines from the TPPE ligand are coordinated by the trans positions to the flat TTF Schiff-base ligand, and complex 2 has an unprecedented catenation of layers within two interpenetrated frameworks. These coordination polymers reserved the redox activity of the TTF unit. Complex 1 shows gradual spin transition behavior without hysteresis. And the fluorescence intensity of TPPE in 1 changes in tandem with the spin crossover (SCO) transition indicating a possible interplay between fluorescence and SCO behavior.

Two dinuclear LnIII‐based clusters, namely [Dy2L2(NO3)2(DME)4] (1) and [Gd2L2(NO3)2(DME)4] (2) [H2L = (E)‐2‐((2‐hydroxybenzylidene)amino)phenol] were obtained under hydrothermal condition. Two LnIII ions are bridged by two phenolic hydroxyl oxygen atoms, and the distances of them are 3.829 Å (Dy1–Dy1A) and 3.860 Å (Gd1–Gd1A). Two Dy1–O–Dy1A and Gd1–O–Gd1A angles are 109.4° and 109.8°, respectively. Magnetic studies reveal a weak antiferromagnetic interaction between Gd ions in complex 2, and single‐molecule magnet behavior for 1 with Ueff = 49.9 K and τ0 = 1.54 × 10–6 s. [ABSTRACT FROM AUTHOR]

Hg(II) coordination complexes containing the tridentate N-(2-methoxyphenyl)-1-(pyridin-2-yl)methanimine ligand were synthesized by using template synthesis approach and characterized using spectroscopic techniques and single crystal X-ray crystallography. The molecular structure and supramolecular features of these compounds were investigated using geometrical, Hirshfeld surface analyses, and theoretical calculations. The supramolecular architecture of these coordination complexes is governed by a combination of π–π, C–H⋯π, and C–H⋯X–M hydrogen bonding interactions. This study may provide further insight into the understanding of the coordination chemistry of Hg(II) containing multidentate Schiff-base ligand and the role of weak non-covalent interactions in the solid-state structure of coordination compounds. [ABSTRACT FROM AUTHOR]

2-Hydroxy-3-methoxybenzaldehyde (L1), 3-amino-1,2-propanediol (L2), trimethylacetic acid (pivalate) and Ln(NO3)3·6H2O were reacted at 80 °C to obtain two hexanuclear clusters [Ln6(HL)2(μ3-OH)2(μ3-OCH3)2(C5H9O2)10(CH3OH)2]·X (Ln = Gd (1, X = 4CH3OH), Er (2)), respectively. The aldehyde group of ligand HL1 is coupled with the amino group of HL2 to obtain 2-(2,3-dihydroxpropyliminomethyl)6-methoxyphenol (H3L). The coordination mode adopted by ligand L3− is μ4-L-k8O1,O2:O2,N1,O3:O3:O3,O4. Trimethylacetic acid adopts three different coordination modes in the six-nuclear cluster. The metal center Ln1 is in the N1O8 coordination environment, and both Ln2 and Ln3 are in the O8 coordination environment. Each of the hexanuclear complex is constructed with Ln3 triangular motifs as building blocks, and the six Ln(III) ions are arranged in a chair-shaped conformation. In magnetization studies of 1 exhibited a large magnetocaloric effect of 20.0 J kg−1 K−1 at 4 K for ΔH = 5 T. [ABSTRACT FROM AUTHOR]

Tetranuclear hetero-metal MnIII 2NiII 2 complexes, [Mn2Ni2(L)4(OAc)2] (1) and [Mn2Ni2(L)4 (NO3)2] (2) [H2L = N-(2-hydroxymethylphenyl)-5,6-benzosalicylideneimine], have been synthesized and characterized by X-ray crystal structure analyses, infrared spectra, and elemental analyses. The structure analyses revealed that the complexes have a defective double-cubane metal core connected by 3-alkoxo bridges. Complexes consist of two bis--alkoxo bridged MnIIINiII heteronuclear units making a dimer-of-dimers structure. The double-cubane cores are significantly distorted due to an effect of syn-syn mode acetato or nitrato bridges. Magnetic measurements indicate that weak antiferromagnetic interactions (Mn-Ni = 0.66 ~ 4.19 cm-1) are dominant in the hetero-metal core. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hexanuclear heterometallic (FeIII 2 LnIII 4) (LnIII = GdIII; TbIII; DyIII and HoIII) complexes are described. • Magnetic studies reveal predominantly antiferromagnetic interactions among the paramagnetic metal centers. • Magnetic anisotropy is present in all the complexes except the GdIII analogue. • Mössbauer measurements confirm the non-magnetic ground state of the central FeIII 2 fragments) in these complexes. • ac Susceptibility measurements upto to 2 K do not reveal the presence of an out-of-phase signal. Abstract Hexanuclear heterometallic (FeIII 2 LnIII 4) (LnIII = GdIII; TbIII; DyIII and HoIII) complexes in a butterfly-shaped core are described. Two of the FeIII ions form part of the body and a pair of lanthanides are present in the wings. Detailed magnetic studies of all the complexes have been carried out which reveal predominantly antiferromagnetic interactions among the paramagnetic metal centers. The M vs H/T plots show the presence of magnetic anisotropy (except for the GdIII analogue) in these complexes. On the other hand, ac susceptibility measurements down to 2 K do not reveal the presence of an out-of-phase signal. Mössbauer measurements confirm the non-magnetic ground state of the central FeIII 2 fragments and absence of the transfer field from the DyIII to FeIII. [ABSTRACT FROM AUTHOR]

Graphical abstract Seven dinuclear lanthanide complexes 1–7 have been synthesized with hydroxyl-rich ligand. Complex 5 exhibits frequency dependence of the ac -susceptibility typical of single-molecule magnets. Abstract Seven dinuclear lanthanide complexes of formulae Ln 2 L 2 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), Ho 2 L 2 ·MeCN (6) and Er 2 L 2 ·MeCN (7) (H 3 L = 2-{[bis(2-hydroxy-3-ethoxybenzyl)(aminoethyl)amino]methyl}phenol) have been synthesized by the reactions of Ln(NO 3) 3 ∙6H 2 O with the hydroxyl-rich ligand H 3 L in MeCN/NEt 3 solution. The structures of the isostructural complexes 1–7 were determined by single-crystal X-ray crystallography. X-ray crystallography analyses reveal that each compound is neutral and consists of two metal centers and two triply-deprotonated ligands. The two Ln(III) atoms in 1–7 are doubly bridged by two phenolato oxygen atoms of two L3− ligands. Each of the two lanthanide ions is seven-coordinated and possesses capped trigonal prism geometry. Dc magnetic susceptibility studies in the 2–300 K range reveal probably weak antiferromagnetic interaction for 3–7. Complex 5 exhibits frequency dependence of the ac -susceptibility typical of single-molecule magnets. [ABSTRACT FROM AUTHOR]

Graphical abstract Three lanthanide complexes were fabricated and characterized. 3 displays slow relaxation of the magnetization. Abstract Three dinuclear lanthanide complexes: {[Ln 2 (L) 2 (tmhd) 2 (CH 3 OH) 2 ]· n CH 3 OH} (Ln = Sm (1 , n = 1), Eu (2 , n = 0), Dy (3 , n = 0); H 2 L = 2-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide, tmhd = 2,2,6,6-tetramethylheptane-3,5-dione) were fabricated and structurally characterized. Compounds 1 – 3 are isostructural belonging to the tetragonal system with space group I 4(1)/ a. Magnetic studies indicated that slow magnetic relaxation behaviors were observed in 3 , with energy barrier (Δ E / k B) of 53.97 K and τ 0 = 4.61 × 10−7 s. Additionally, solid-state luminescence measurements reveal that 2 and 3 display the characteristic lanthanide luminescence at room temperature. [ABSTRACT FROM AUTHOR]

Graphical abstract The three novel Fe(III) compounds of the formula [FeL 2 ]X (where X = Clˉ (1), PF 6 ˉ (2), NO 3 ˉ (3), and L is a photoactive ligand, (4)-4-(((2-(ethylamino)ethyl)imino)methyl)-3-hydroxyphenyl 4-bromobenzoate) was synthesized and studied by means of electron paramagnetic resonance (EPR) and pulsed laser irradiation. The Fe3+ ions in these compounds are in a high-spin state. A thorough analysis of the EPR data suggests that compounds 1 and 2 undergo an order-disorder ferroelectric phase transition, and below the phase transition temperature (T c = 100 and 200 K for compounds 1 and 2 , respectively) a nonzero average electric dipole moment appears. It was also shown that, whereas the chloride and hexafluorophosphate anions are able to form a network of hydrogen bonds between the [FeL 2 ]X units (ionic pairs), which enable an electric dipole ordering in the sample, the nitrate anions, in contrast, tend to form hydrogen bonds inside the ionic pair. This conclusion is evidenced by the observed EPR spectra, which are different for compound 3 and are not indicative of the existence of an order-disorder ferroelectric phase transition. The EPR data obtained upon irradiation of compound 1 show that photoexcitation in the UV region at 5 K destroys hydrogen bonds and converts cationic complexes into ligand-to-metal charge transfer (LMCT) states , in which the iron is ferrous, and the unpaired electron is located on the salicylidene moieties. The LMCT states decay back to the ferric one, and ferric complexes further form the most stable (LT) phase structure. Abstract A series of three novel Fe(III) compounds of the formula [FeL 2 ]X (where X = Cl− (1) , PF 6 − (2) , NO 3 – (3), and L is a photoactive ligand, (4)-4-(((2-(ethylamino)ethyl)imino)methyl)-3-hydroxyphenyl 4-bromobenzoate) was synthesized and studied by means of electron paramagnetic resonance (EPR) and pulsed laser irradiation. The Fe3+ ions in these compounds are in a high-spin state. A thorough analysis of the EPR data suggests that compounds 1 and 2 undergo an order–disorder ferroelectric phase transition, and below the phase transition temperature (T c = 100 and 200 K for compounds 1 and 2 , respectively) a nonzero average electric dipole moment appears. To get an insight into molecular structure of Fe3+ ions and their supramolecular organization in low-temperature (LT) and high-temperature (HT) phases of compounds 1 and 2 , a series of density functional theory calculations was performed. On the basis of our findings, the LT- and HT-phase structures were proposed for these compounds. It was also shown that, whereas the chloride and hexafluorophosphate anions are able to form a network of hydrogen bonds between the [FeL 2 ]X units (ionic pairs), which enable an electric dipole ordering in the sample, the nitrate anions, in contrast, tend to form hydrogen bonds inside the ionic pair. This conclusion is evidenced by the observed EPR spectra, which are different for compound 3 and are not indicative of the existence of an order–disorder ferroelectric phase transition. The EPR data obtained upon irradiation of compound 1 show that photoexcitation in the UV region at 5 K destroys hydrogen bonds and converts cationic complexes into ligand-to-metal charge transfer (LMCT) states, in which the iron is ferrous, and the unpaired electron is located on the salicylidene moieties. The LMCT states decay back to the ferric one, and ferric complexes further form the most stable (LT) phase structure. [ABSTRACT FROM AUTHOR]

Graphical abstract The magnetic properties of solutions of three Fe(III) complexes, [Fe(salten)Cl], [Fe(salten)(Pic)]BPh 4 and [Fe(acen)(Him) 2 ]BPh 4 , in CH 2 Cl 2 were studied. The paramagnetic contribution of the complex molecules to the volume magnetic susceptibility of the solution was measured by NMR spectroscopy. The temperature dependences of μ eff for the three solutions of the complexes were obtained. In the solution of the first complex only the high-spin state S = 5/2 was observed. The solutions of the second and the third complexes demonstrated an incomplete spin-crossover between the low-spin S = 1/2 and the high-spin S = 5/2 states, the latter of them being mainly low-spin. It was revealed that in solutions of the last two complexes the spin-crossover has a greater slope than that in the solid state. Abstract The magnetic properties of solutions of three Fe(III) complexes, [Fe(salten)Cl], [Fe(salten)(Pic)]BPh 4 and [Fe(acen)(Him) 2 ]BPh 4 , in CH 2 Cl 2 were studied. The paramagnetic contribution of the complex molecules to the volume magnetic susceptibility of the solution was measured by NMR spectroscopy. The temperature dependences of μ eff for the three solutions of the complexes were obtained. In the solution of the first complex only the high-spin state S = 5/2 was observed. The solutions of the second and the third complexes demonstrated an incomplete spin-crossover between the low-spin S = 1/2 and the high-spin S = 5/2 states, the latter of them being mainly low-spin. It was revealed that in solutions of the last two complexes the spin-crossover has a greater slope than that in the solid state. [ABSTRACT FROM AUTHOR]

Abstract: Reactions of lanthanide nitrate, nickel nitrate, and polyhydroxyl Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L) gave rise to a family of butterfly heterotetranuclear 3d-4f clusters formulated as [Ln2Ni2(H2L)2(μ3-OCH3)2(CH3CN)2(NO3)4]·2CH3OH·2H2O [Ln = Pr (1), Sm (2), Eu (3), Tb (4), Er (5)]. Single-crystal X-ray diffraction (XRD) reveals these complexes crystallize in the monoclinic space group P21/c. Both Ln1 and its symmetric Ln1A are coordinated to nine oxygen atoms and consist of two ligands with the same coordination mode μ3.η1:η2:η1:η2:η1, two nitrate ions and one μ3-OCH3. The five heterotetranuclear Ni2IILn2III complexes display a central planar butterfly topology. The vertices of the body positions of the butterfly are occupied by NiII ions in all five complexes, which have been characterized by single-crystal X-ray diffraction, infrared spectroscopy, element analyses, powder X-ray diffraction and thermal gravimetric analyses. The magnetic properties of the complexes have been studied. The results show that complexes 1-3, and 5 exhibit antiferromagnetic exchange between the paramagnetic species, and 4 shows strong ferromagnetic interaction.Graphical Abstract: We have shown the successful design and assembly of a new family of tetranuclear, dicationic, heterometallic Ni2IILn2III complexes characterized by a butterfly-type topology. The results might be promoting the rational design and synthesis of 3d-4f molecule-base magnets materials with fascinating topologies and magnetic behaviours. [ABSTRACT FROM AUTHOR]

New pyrimidine Schiff base Fe(III) complexes, [Fe III (HL) 2 ]ClO 4 ·2CH 3 CN·2H 2 O ( 1 ), [Fe III (HL) 2 ]BF 4 ·H 2 O ( 2 ) and [Fe III (HL) 2 ]PF 6 ·CH 3 OH ( 3 ) (H 2 L = 2-(pyrimidin-2-ylhydrazonomethyl)phenol), have been synthesized and characterized by single-crystal X-ray diffraction, magnetic, thermogravimetric and UV–vis spectroscopy. Structural data of complexes 1 – 3 indicate that they are all mononuclear and the coordination configuration of central Fe(III) ions is N 4 O 2 octahedron. The Fe-O and Fe-N bond distances are in the range of 1.886–1.924 Å and 2.130–2.170 Å, respectively, typical of the high-spin Fe(III) at 273 K (complex 1 ) or 293 K (complexes 2 and 3 ). Magnetic studies show that complex 1 exhibits the spin crossover behavior with a hysteretic loop of 13 K ( T 1/2 ↓ = 144 K and T 1/2 ↑ = 157 K), while complexes 2 and 3 are high spin down to 5 K. [ABSTRACT FROM AUTHOR]

Reaction of pentadentate Schiff-base ligands, 1,3-bis(3-methoxysalicylideneamino)-2-propanol (H3msap) with manganese(II) salts afforded tetranuclear mixed-valent manganese complexes, [Mn4(msap)2(CH3CO2)3(CH3O)(H2O)]·H2O (1) and [Mn4(msap)2(C6H5CO2)3(CH3O)] (2), which were characterized by elemental analysis, infrared and diffused reflectance spectra and temperature dependence of magnetic susceptibilities (4.5–300 K). Single-crystal X-ray crystallography of these complexes showed that four manganese atoms are chelated by two Schiff-base ligands and further coordinated by syn–syn bridging, syn–anti bridging, and monodentate or bidentate-carboxylato groups, forming a Y-shaped cluster made up of two MnII and two MnIII atoms. Diffused reflectance spectra are featureless, showing broad bands around at near-UV and visible regions. Magnetic moments decrease with lowering of temperature, showing an antiferromagnetic behavior of these complexes. [ABSTRACT FROM AUTHOR]

The new polydentate Schiff-base oxime (1E,1`E)-2hydroxy-3-((E)-(2-((E)-2hydrxy3-((E)-(hydroxyimino)methyl)-5-methylbenzyldeneamino)ethylimino)methyl)-5methylbenzaldehyde oxime H4L and its binuclear metal complexes with Mn(II), Fe(II), Co(II) and Cu(II) are reported. The reaction of 2,6 diformyl–4–methyl phenol with hydroxyl amine hydrochloride in mole ratios of 1:1 gave the precursor (E)-2-hydroxy-3((hydroxyimino)methyl)-5-methylbenzaldehyde. Condensation reaction of precursor with ethylenediamine in mole ratios of 2:1 gave the new N4O2 Schiff-base oxime ligand H4L. Upon complex formation, the ligand behaves as a tribasic hexadantate species. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed tetrahedral geometries for Mn(II), Fe(II), Co(II) complexes and square planar geometry about Cu(II) complex of general formulae [M2(HL)](Cl)(H2O). Molecular structure of the for Mn(II), Fe(II), Co(II) complexes has been optimised by CS Chem 3D Ultra Molecular Modeling and Analysis Program and supported four coordinate geometry.

This article discloses a method for altering Schiff base to ester in the generative process of binuclear Ln-complexes with U eff of 61.7 k at zero dc field for Dy-complex. In this article, three [Ln 2 ] complexes, [Ln 2 (dbm) 4 (L′) 2 ] (Ln = Tb (1), Dy(2), Ho(3)), were reported. Static and dynamic magnetic analysis of complexes 1 – 3 revealed that complex 2 possessed effective energy barrier of 61.7 K at zero dc field, suggesting single-molecule magnet (SMM) behavior. Besides, the coordinated ligand HL′ in the three complexes (HL′ = methyl-8-hydroxyquinoline-2-carboxylate) was not original but transformed from Schiff-base HL (HL = 2-[[(1,2,4-triazole)-4-imino]methyl]-8-hydroxy-quinoline) during the coordination process. As the best knowledge of us, this kind of ligand-exchange is rare in organic chemistry and in coordination chemistry. [Display omitted] Three [Ln 2 ] complexes, [Ln 2 (dbm) 4 (L′) 2 ] (Ln = Tb(1), Dy(2), Ho(3)), were synthesized, and structurally and magnetically analysed. The structural analysis revealed that a rare ligand-transformation in the field of organic chemistry and coordination chemistry occured during the coordination process, where the original Schiff-base ligand HL (2-[[(1,2,4-triazole)-4-imino]methyl]-8-hydroxy-quinoline) was transformed to coordinated ligand HL′ (methyl-8-hydroxyquinoline-2-carboxylate). Static and dynamic magnetic analysis of 1 – 3 demonstrated single-molecule magnet (SMM) behavior for complex 2 with effective energy barrier of 61.7 K at zero dc field. [ABSTRACT FROM AUTHOR]

• Syntheses and characterizations of a new schiff base ligand and its two Ni(II) complexes have been reported. • X-ray crystallographic study has confirmed the structures of the ligand molecule and its two Ni(II) complexes. • Anticancer activity of the ligand and complexes against the human breast cancer cell lines MCF 7 and MDA-MB-231 have been reported. • The catalytic activity of the synthesized complexes was determined by the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). A new pyrazole containing 'NN' bidentate Schiff-base ligand, N-(furan-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPAFA) (compound I) and its two new Ni(II) complexes, [Ni(MPAFA) 2 (H 2 O) 2 ].2Cl·2H 2 O (compound II) and [Ni(MPAFA) 3 ].2ClO 4 (compound III) have been synthesized and characterized by various physico-chemical and spectral parameters viz., elemental analyses, mass, IR, NMR (1H and 13C, ligand only), UV–vis spectral parameters and X-ray crystallographic studies. Both the complexes are behaving as 1:2 electrolytic species and the primary ligand, MPAFA, acts as a neutral 'NN' bidentate one in both the complexes. IR spectral data revealed that the coordination to each of the metal center in both II and III , takes place through the pyrazolyl (tertiary) ring nitrogen and the azomethine nitrogen atom. X-ray data have revealed that both II and III are octahedral in nature and confirmed a NiN 4 O 2 and NiN 6 octahedral coordination, respectively. Ni(II) ion has formed two sets of complexes; in II , two molecules of ligand and two water molecules are coordinated to the metal forming a mixed ligand complex (1:2 complex), while in III , three ligand molecules are coordinated to the metal (1:3 complex). The ligand and the Ni(II) complexes reported here have been tested for their catalytic and anticancer activities. II and III have been found to be efficient in reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of sodium borohydride (NaBH 4) as a reducing agent; and are more potent cytotoxic agents and stronger anti-cancer materials against the breast cancer cell lines MCF7 and MDA-MB-231 than the primary ligand system. [Display omitted] [ABSTRACT FROM AUTHOR]

Tetranuclear hetero-metal MnIII2NiII2 complexes, [Mn2Ni2(L)4(OAc)2] (1) and [Mn2Ni2(L)4(NO3)2] (2) [H2L = N-(2-hydroxymethylphenyl)-5,6-benzosalicylideneimine], have been synthesized and characterized by X-ray crystal structure analyses, infrared spectra, and elemental analyses. The structure analyses revealed that the complexes have a defective double-cubane metal core connected by μ3-alkoxo bridges. Complexes consist of two bis-μ-alkoxo bridged MnIIINiII heteronuclear units making a dimer-of-dimers structure. The double-cubane cores are significantly distorted due to an effect of syn–syn mode acetato or nitrato bridges. Magnetic measurements indicate that weak antiferromagnetic interactions (Mn-Ni = −0.66 ~ −4.19 cm–1) are dominant in the hetero-metal core.

This paper reports the synthesis, crystal structures, and thermal behavior of two zinc-gadolinium (3d-4f) coordination polymers by adjusting the connectivity of a secondary building unit ( SBU) with two pyridyl-carboxylic acids as linkers. As a SBU, the Zn-Gd compartment compound, [ ZnGd(L)( NO3 )( CH3CN)( H2O)4]( NO3 )2( H2O) ( H2L = 1,3-bis((3-methoxysalicylidene)amino)propane), was used. Under microwave heating conditions, the SBU reacted with 4-pyridinepropionic acid (4-Hppa) and 4-pyridinecarboxylate (4-Hpca) to create a 1D polymer, [ ZnGd(L)( NO3 )2(4-ppa)( EtOH)], and a 2D polymer, [ ZnGd(L)( NO3 )2(4-pca)], respectively. Dimensionality of the products appeared to depend on the continuity of π conjugation of the external linking ligand. [ABSTRACT FROM AUTHOR]

The Pd(II) bis(benzonitrile) complex [Pd(PhCN) 2 Cl 2 ] reacted with a mixture of 2-hydroxy-3-methoxybenzaldehyde, 1,3-diaminopropane, and triethylamine in acetonitrile to produce [Pd(L 1 )Cl] (HL 1 = ( E )-2-(((3-aminopropyl)imino)methyl)-6-methoxyphenol) ( 1 ), which contains an imine–amine-type macrocyclic ligand and a chloro ligand. Complex 1 was converted into a cyclohexane-like palladacycle, [Pd(NH 2 CH 2 CH 2 CH 2 NH 2 )Cl 2 ] ( 2 ), when heated in acetonitrile at 80 °C for 60 h. The palladium compartment complex [Pd(L 2 )] (H 2 L 2 = N , N ′-bis(3-methoxysalicylidenimino-1,3-diaminopropane) ( 3 ) was obtained from the free bis(imine) ligand (H 2 L 2 ) and [Pd(PhCN) 2 Cl 2 ] or Pd(OAc) 2 in methanol. All complexes were structurally characterized by X-ray diffraction. Complex 3 is the first structurally characterized palladium compartment complex, in which the compartment ligand has an inner N 2 O 2 and an outer O 2 O′ 2 compartments. The coordination geometry of the palladium metal in all complexes ( 1 – 3 ) can be best described as square-planar. [ABSTRACT FROM AUTHOR]

A series of neutral lanthanide alkoxide complexes stabilized by a new salen-type Schiff-base ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of lactide were explored. Amine elimination reactions of N -methyl- N ′, N ″-bis(3,5-di- tert -butylsalicylidene)-2,2′-diaminodiethylamine (LH 2 ) with Ln[N(SiMe 3 ) 2 ] 3 (Ln = Sm, Nd, La) in a 1:1 M ratio in THF, followed by reactions with 1 equiv of alcohols ( t BuOH, EtOH and CH 3 OCH 2 CH 2 OH), produced lanthanide alkoxide complexes LLn(O t Bu)(THF) (Ln = Sm ( 1 ), Nd ( 2 ), La ( 3 )), [LSm( μ -OEt)] 2 ( 4 ) and [LSm( μ -OCH 2 CH 2 OCH 3 )] 2 ( 5 ), respectively, whereas the same reaction with Yb[N(SiMe 3 ) 2 ] 3 gave an unexpected homoleptic complex L 2 Yb 2 ( μ -L) ( 6 ). X-ray structural determination showed that complexes 1 – 3 have a THF-solvated monomeric structure, whereas complexes 4 – 6 have an unsolvated dimeric structure. All lanthanide alkoxide complexes can efficiently initiate the ring-opening polymerization (ROP) of L -LA and rac -LA. The polymerization kinetics of L -LA initiated by complex 1 has been studied in detail and the first-order kinetic dependence on both l -lactide concentration and initiator concentration was found. Furthermore, all complexes showed moderate stereoselectivity for rac -LA polymerization to afford heterotactic-rich polylactides. [ABSTRACT FROM AUTHOR]

Magnetite nanoparticles were surface-modified with mercaptoacetic acid (MAA), complexed with Zn(II), and then treated with the dual Schiff base (referred to as imine-based ligand; IBL; obtained by reaction of p-aminobenzoic acid and 2,3-butanedione) to give particles with an architecture of type FeO@MAA@IBL. These are shown to be viable sorbents for magnetic solid phase extraction of organochlorine pesticides (OCPs) from seawater samples. Efficient extraction of the OCPs probably is due to lone pair-π, π-complexation and π-interactions. The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FT-IR and energy-dispersive X-ray spectroscopy. The effects of the volumes of sample, sorbent dosage and eluent, adsorption and desorption times, and the salinity of the sample on the extraction efficiencies were optimized. The OCPs (heptachlor, aldrin, dieldrin, p,p'-DDE and p,p'-DDT) were quantified by gas chromatography with microelectron capture detection. Under optimal conditions, the limit of detections range was between 1.0 and 1.9 ng L. The enrichment factors are between 84.1 and 99.9 %. The sorbent was applied to the rapid extraction of trace quantities of OCPs from seawater samples and gave good relative recoveries (78 to 108 %) and relative standard deviations (<8.3 %). [ABSTRACT FROM AUTHOR]

The μ-oxo-bridged Fe(III) dimer complex [{Fe(4-MeOL1)}(μ-O)]∙HOCH, (H-4-MeOL1 = N, N′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), 1 is synthesized and characterized by single crystal X-ray diffraction. Complex 1 contains a [{Fe(4-MeOL1)}2(μ-O)] dimeric unit with a methanol solvent molecule of crystallization. Each Fe(III) ion has a distorted square-pyramidal coordination geometry. In the basal plane, the Fe(III) atom is coordinated by two N and two O atoms of the Schiff base ligand. The apical position is occupied by a bridging O ion, linking another Fe(III) ion in the complex. There are intermolecular C-H...O and C-H...π interactions among the dinuclear complexes. [ABSTRACT FROM AUTHOR]

Substituted pyrazole containing Schiff-base ligand, 5-methyl-3-formylpyrazole-N-(2′-methylphenoxy)methyleneimine, (MPzOA), afforded three new Cd(II) complexes, [Cd(MP z OA)Cl 2 ] 2 .CH 3 OH ( I ), [Cd(MP z OA) 2 (H 2 O) 2 ](ClO 4 ) 2 ( II ) and [Cd(MP z OA)(H 2 O)(NO 3 ) 2 ] ( III ). In the reported complex species the coordination number and geometry of Cd(II) vary. In complex I and II, Cd(II) adopts six and in ( III ) it adopts eight coordination modes, with prismatic, octahedral and distorted dodecahedral geometry, respectively. All the complexes are characterized by IR, 1 H NMR, UV–Vis spectral parameters and X-ray analyses. The complexes have 1D, 2D and 3D supramolecular frameworks formed by non-covalent interactions, like hydrogen bonding, π … π stacking, C–H … π interactions. [ABSTRACT FROM AUTHOR]

[Display omitted] A new Schiff-base ligand, 4-[(4-oxo-4,5-dihydro-1,3-thiazol-2-yl)hydrazono]methylphenyl 4-methylbenzenesulfonate (L), and its Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized. Elemental analysis, NMR spectroscopy, mass spectra, FT-IR analysis, molar conductivity, magnetic susceptibility tests and electronic spectra (UV-vis.) were all used to describe the ligand and its metal complexes. The complexes of Ni(II) and Zn(II) were found to have a tetrahedral structure, whereas those of Fe(III), Co(II) and Cu(II) exhibited an octahedral structure. The geometry of the ligand and its metal complexes was investigated by density functional theory (DFT) calculations at the B3LYP/6-311G(d, p) and LanL2dz levels of theory, respectively. To round out the picture, we evaluated not only the overall energy but also the HOMO and LUMO molecular orbitals and the molecular electrostatic potential (MEP). The synthetic analogues were tested for their in vitro antibacterial and antifungal efficacy against various pathogens using the disc diffusion method. The research shows that the metal complexes are more effective against these diseases than the free ligand. In addition, the DPPH method was used to measure the antioxidant activity in vitro. The antioxidant activity of each complex was higher than that of its free corresponding ligand. Molecular docking was carried out to determine the interactions between the complexes and the probable binding sites of Human Peroxiredoxin 2 Oxidized (PDB ID: 5IJT) and Escherichia coli (PDB ID: 3t88) receptors. [ABSTRACT FROM AUTHOR]

The reactions of equimolar amounts oftrans-[ReOC13(PPh3)2] ortrans-[Re(NPh)(PPh3)2Cl3] with a Schiff base formed by condensation of 2-hydroxy-4-methoxybenzaldehyde and ethanolamine (H2L) result in the formation ofcis-[ReO(HL)PPh3Cl2] (1a) andtrans-[Re(NPh)(HL)(PPh3)Cl2] (2b), respectively, in good yields.1aand2bhave been characterized by a range of spectroscopic and analytical techniques. The X-ray crystal structures of1aand2breveal that1ais an octahedralcis-Cl,Cloxorhenium(V) complex, while2bis atrans-Cl,Clphenylimidorhenium(V) complex. The complexes are weakly emissive at room temperature with quantum yields of 10−4. Density functional theory calculations of the electronic properties of the complexes were performed and are in agreement with the experimental results. The complexes display quasi-reversible Re(V)/Re(VI) redox couples in acetonitrile. There is reasonable agreement between the experimental and calculated redox potentials of1aand2b. [ABSTRACT FROM PUBLISHER]

Cobalt(III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H2sbba) and N-salicylidene-2-hydroxy-5-chlorobenzylamine (H2scba), [n-(C4H9)4N][Co(sbba)2] (I) and [n-(C4H9)4N][Co(scba)2] (II ), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P21/n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4)◦, V = 4208.2(14) Å3, Dx = 1.295 g cm−3, and Z = 4. The R1 [I > 2σ(I)] and ωR2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra(n-butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba2− ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N2O4 donor set. [ABSTRACT FROM AUTHOR]

A new dinuclear Fe(III) complex, [Fe(5-MeOL1)(OH)(CHO)]•2(CHOH), [H-5-MeOL1 = N, N′-bis(5-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine], 1 has been synthesized and characterized by single crystal structure analysis. The structure of 1 consists of two Fe(III) centers with one tetradentate schiff base ligand (NO) which are bridged by dihydroxo/dimethoxo groups to yield a FeO core. Complex 1 exhibits weak antiferromagnetic exchange interaction between Fe(III) ions with J = −0.21 cm. [ABSTRACT FROM AUTHOR]

Reaction of equimolartrans-[Re(NPh)(PPh3)2Cl3] with H2L, a 1 : 1 Schiff-base condensate of salicylaldehyde and ethanolamine, in chloroform givestrans-[Re(NPh)(HL)(PPh3)Cl2] (1a) in good yield.1ahas been characterized by C, H, and N microanalyses, FTIR and UV–vis spectra. The X-ray crystal structure of1areveals that it is an octahedraltrans-Cl,Clphenylimidorhenium(V) complex. The rhenium center has an ‘N2OCl2P’ coordination sphere.1acrystallizes in the monoclinic space group P21/c witha = 11.2391(5),b = 16.4848(7),c = 16.3761(8) Å,V = 3034.0(2) Å3andZ = 4. The electrochemical aspects of1ahave been studied. Electrochemical studies of1ain dichloromethane show a quasi-reversible Re(V) to Re(VI) oxidation at 1.128 VversusAg/AgCl. This redox potential reasonably matches the calculated redox potential, 1.186 VversusAg/AgCl. Geometry optimization of thetrans-Cl,Cl1avis-à-vis itscisanalog,cis-Cl,Cl1b, have been performed at the level of density functional theory (DFT). It is revealed that1ais more stable than1bby 21.6 kcal per mole of energy in the gas phase. [ABSTRACT FROM PUBLISHER]

The initial employment of 2-(2-hydroxy-3-methoxybenzylideneamino)phenol (H 2 L) in Mn–Ln chemistry yields four isostructural Mn III 2 Ln III 2 clusters [Mn III 2 Ln III 2 (O)L 4 (CH 3 OH) 4 (Cl) 2 ]·(Ln = Eu ( 1 ), Gd ( 2 ), Tb ( 3 ) and Dy ( 4 )). All four isostructural clusters were structurally and magnetically characterized. Structural analyses reveal that they are tetranuclear isostructural clusters, each consisting of two dinuclear Mn–Ln entities. Static magnetic studies indicate the presence of dominant ferromagnetic interactions in complexes 3 and 4 , whereas complex 2 , containing Gd, allows quantification of an antiferromagnetic interaction with J Mn–Gd = −0.41 cm −1 . Dynamic measurements reveal that 3 exhibits slow relaxation of the magnetization and 4 displays single-molecule magnet behavior with an energy barrier of Δ = 15.8 K and a pre-exponential factor of τ 0 = 7.65 × 10 −7 s, while 1 and 2 do not show any out-of-phase ac susceptibility signals. This work highlights the different contributions of the respective lanthanide ions to the overall magnetic behavior in Mn III 2 Ln III 2 systems. [ABSTRACT FROM AUTHOR]

Two novel iron(III) complexes involving pentadentate Schiff-base ligands, [Fe(L Br )(L 1 )], show temperature induced incomplete spin crossover of a gradual nature. While for the L 1 = NCSe − coligand the transition temperature (326 K or 317 K) lies above room temperature, the N 3 − coligand causes its drop down to 143 K or 140 K (two values were obtained by different models). This shift is associated with a significant decrease of the enthalpy of the transition from about Δ H = 6.1 kJ mol −1 to ca. Δ H = 1.7 kJ mol −1 , while the entropy of the transition is about Δ S = 19 J K −1 mol −1 and Δ S = 12 J K −1 mol −1 , respectively. Two analogous complexes with Cl − and NCS − coligands remain high-spin over the whole temperature range. [ABSTRACT FROM AUTHOR]

Highlights: [•] One rare example for each of CuII(UVIO2) and star-shaped CuII 3CdII compounds. [•] First examples of CuIIMIICuII-based, dicyanamide-bridged polymers (M=Zn, Ni, Co). [•] Star-shaped system here is the best star-shaped system in terms of bond distances. [•] Exploration of a less investigated Schiff base ligand. [•] An excellent correlation of d–d band position with structural parameter. [Copyright &y& Elsevier]

Highlights: [•] New mono- and binuclear CuII complexes of a sulfamethazine Schiff-base were prepared. [•] Correlation between the experimental and theoretical work was performed. [•] Mononuclear complex is less toxic than free ligand, while the binuclear one is inactive. [•] E LUMO, ΔE, dipole moment and polarizability correlate well with experimental LC50. [Copyright &y& Elsevier]

Abstract: A novel six-coordinate ruthenium(II) complex 1, formulated as [Ru(bpy)2Lb]PF6⋅C2H5OH (bpy=2,2′-bipyridine), has been obtained and characterized. Ligand Lb in 1 comes from a chiral bis-Schiff-base ligand La which is condensed between sodium(I) salt of D- or L-phenylanine and terephthaldicarboxaldehyde. It is noted that ligand La undergoes partial C=N bond cleavage of Schiff-base unit forming a free aldehyde group at one end of phenyl ring, and an unusual proton migration, a C=N double-bond shift and subsequent nonchirality at the other end simultaneously in the presence of a ruthenium(II) ion. [Copyright &y& Elsevier]

A mononuclear complex, [CuL2]·2(CH3OH) (1), and two one-dimensional (1D) coordination polymers, {[Cu3L4(CH3OH)2]·(NO3)2} n (2) and [Cd(LH)2(N3)2] n (3), having a flexible multidentate Schiff-base ligand, 2-(3-(1H-imidazol-1-yl)propyliminomethyl)phenol (LH), with multifarious coordination modes have been obtained in different solvents and pH values. Another 1D cadmium(II) coordination polymer, [Cd(apimH)2Br3] n (4) (apim=(3-aminopropyl)imidazole), is also included for comparison. A four-coordinate square-planar Cu(II) center is formed in 1 where L serves as a bidentate N,O-chelating ligand, while two five-coordinate dinuclear Cu(II) centers and one six-coordinate mononuclear Cu(II) center are alternately arranged via two tridentate ligands in 2. In contrast, six-coordinate Cd(II) centers are constructed in 3 and 4, in the absence of a base, and they are bridged by double μ 2 azide anions in an end-to-end way in 3 and alternate mono and triple μ 2 bromine anions in 4. Furthermore, FT-IR, 1H NMR, UV–Vis and fluorescence spectral comparisons between LH and its metal complexes have been studied. [ABSTRACT FROM AUTHOR]