L1)2 Research Articles

Functional mimic for catechol oxidase and phenoxazinone synthase: Structural, spectral, electrochemical and catalytic properties of mononuclear copper(II) complex

A promising bioinspired metallocatalyst [Cu(L1)2(L2)] (L1 = P-hydroxybenzoic acid, L2 = N1,N1-dimethylpropane-1,3-diamine) has been produced and characterized in accordance with reports. In the octahedron arrangement around the copper ion, the elongation along one axial direction and one equatorial direction results in a distorted geometry Molecular assembly shows both inter and intra molecular H-bonding along with CH---π interactions evident from the Hirhsfeld surface analysis. The fingerprint plot discloses the relative contribution of percentage of intermolecular contacts (H⋯H, C⋯H and O⋯H) in the complex. The EPR, CV, and UV analyses collectively support that the complex exhibits such activity via oxygen dependant enzymatic radical pathway. Furthermore, these activities are observed under fully aerobic conditions in which 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-amino phenol (2-AP) are used as model substrates. Michaelis-Menten analysis derived from the pseudo first-order reaction kinetics established that this complex shows extremely high catalytic activity towards 3,5- DTBC and 2-AP (Kcat 1.729 × 105 h−1 and 0.260 × 105 h−1). The suggested mechanism has been supported by UV spectra data in which formation of hydrogen peroxide by observing the appearance of spectral band at λmax 353 nm indicates the active participation of molecular oxygen in the catalytic process.

Synthesis, characterization and photo-physical studies of naphthalamide-based Ir(III) complexes

Interest in tuning the emission towards deep-red (DR) and near-infrared (NIR) regions is enhanced due to their fascinating applications in the field of organic light-emitting diodes (OLEDs), night-vision display and bio-imaging. In this regard, Naphthalimide based bidentate chromophoric ligand (L1, NIPy, 2‑butyl‑6-(pyridin-2-yl)-1H-benzo[de]isoquinoline-1,3(2H)‑dione) was utilized to prepare the DR emitting Ir(III) complexes [Ir(L1)2(L2)] (1) and [Ir(L1)2(L3)] (2) where L2 = 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine and L3 = 1-(4-fluorophenyl)-3-methyl-1H-3λ4-imidazole). Complexes have been characterized by various analytical and spectroscopic methods, and 2 was further confirmed by a single crystal X-ray diffraction method. Strong intermolecular π···π interactions between the naphthalamide units in complex 2 lead to the formation of a multi-dimensional framework. These complexes show emissions in the range of 650–700 nm at room temperature, which extends up to the near-infra-red region (800 nm). The photophysical studies were supported by DFT and TD-DFT calculations. These types of naphthalimide-based Ir(III) complexes tend to show emissions in the NIR region which has potential applications in the field of photodynamic therapy and OLEDs.

Synthesis, crystal structure and properties of Mn/Ni/Co 3D network structures based on 2, 5-bis(trifluoromethyl) terephthalic acid ligands

2,5-bis(trifluoromethyl)terephthalic acid (H2L1) as the main ligand and 1,10′-phenanthroline (L2) as the co-ligand were reacted with manganese chloride tetrahydrate (MnCl2·4H2O), nickel sulfate hexahydrate (NiSO4·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) by solvothermal reaction to give the manganese complex [Mn2(L1) 2(L2)2]n (1), the nickel complex {[Ni3(L1)3(L2)2(H2O)4]·2DMF}n (2) and the cobalt complex {[Co2(L1)2(DMF)2]·H2O}n (3). The structures were characterized and their properties studied by means of single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, ultraviolet spectroscopy, fluorescence spectroscopy, thermogravimetric analysis. The single-crystal structure analysis showed that the complexes 1–3 are infinitely extended three-dimensional network-like structures of space groups P1-, P1-, P21/n, respectively. The results of fluorescence analysis and thermogravimetric analysis showed that complexes 1–3 have good thermal stability and fluorescence properties, respectively. Complex 3 can also maintain good thermal stability at 230 °C, and the maximum fluorescence emission wavelength is 370 nm.

A stable N-containing heterocyclic carboxylic acid ligand Co-MOF for photoelectric performance and anionic dyes adsorption

Metal-organic frameworks (MOFs) are crystalline porous hybrid materials with periodic network structure and abundant active sites, which are promising adsorbents for organic pollutants. Herein, a novel Co(II)-based organic framework (Co-MOF) [Co2(L1)2(L2)] (L1 = 3-(3-carboxylphenyl) isonicotinic acid, L2 = 4, 4′-Azopyridin) was developed for selective dyes adsorption. Experiments suggest that the Co-MOF exhibits high stability, good photoelectricity and high selectivity for dyes adsorption. For dyes adsorption, the Co-MOF shows a strong adsorption to methyl orange achieving a high capacity up to 440.5 mg g−1, but shows a weak adsorption to methylene blue or rhodamine, indicating its better selectivity for anionic dyes. An insight into the selective removal of the methyl orange is being accounted for by acid-base attraction, anion-π and π–π stacking interactions, involving the Co ion, phenyl rings, and ocarboxylate of L, and the phenyl rings, and osulfonate of MO. The current work contributes to the development of future multifunctional MOF materials with the application in environment protection.

Manipulating Solvothermal Coordination-Catalyzed In Situ Tandem Reactions to Construct Dysprosium-Based Complexes with Different Shapes and Zero-Field SMM Behaviors.

By changing the coordination anions (OAc- and Cl-), reaction temperature, solvent, and ligand substituents, four Dy(III)-based complexes were obtained by directed synthesis, which are [Dy4(L1)2(L2)2(OAc)4]·4C2H5OH·3H2O (1, L1 = 1,3,4-thiadiazole-2,5-diamine, H4L2 = 6,6'-(((1,3,4-thiadiazole-2,5-diyl)bis(azanediyl))bis(((3-ethoxy-2-hydroxybenzyl)oxy)methylene))bis(2-ethoxyphen), [Dy4(L3)4(OAc)4]·C2H5OH·H2O (2, H3L3 = 2-(((5-amino-1,3,4-thiadiazol-2-yl)amino)((3-ethoxy-2-hydroxybenzyl)oxy)methyl)-6-ethoxyphenol)), [Dy6(L4)4(L5)2(μ3-OH)4(CH3O)4Cl4]Cl2 (3, H2L4 = 2-hydroxy-3-methoxybenzaldehyde, H2L5 = 2-(((5-amino-1,3,4-thiadiazol-2-yl)amino)(hydroxy)methyl)-6-methoxyphenol), and [Dy6(L6)4(L7)2(μ3-OH)4(CH3O)4Cl4]Cl2·2H3O (4, H2L6 = 2-hydroxy-3-ethoxybenzaldehyde, H2L7 = 2-(((5-amino-1,3,4-thiadiazol-2-yl)amino)(hydroxy)methyl)-6-ethoxyphenol). A series of acetal products (H4L2, H3L3, H2L5, and H2L7) were obtained through dehydration in situ tandem reactions. Magnetic studies show that complexes 1-4 exhibited different single-molecule magnet behavior under zero-field conditions. The best fitting results showed that under zero DC field, the effective energy barriers (Ueff) and magnetic relaxation times (τ0) of complexes 1-4 are Ueff = 117.0 (2.1) K and τ0 = 6.07 × 10-7 s; Ueff = 83.91 (1.5) K and τ0 = 4.28 × 10-7 s; Ueff = 1.28 (0.2) K and τ0 = 0.73 s, and Ueff = 104.43 (13.3) K and τ0 = 8.25 × 10-8 s, respectively.

Assembly of tetra-nuclear lanthanide compounds: Structures, magnetic refrigeration and slow relaxation of magnetization

Two novel tetranuclear lanthanide compounds with the formula [Ln4(L1)2(L2)2(μ2- OCH3)2(CH3OH)2]·CH3OH (Ln = Gd (1), Dy (2), H2L1 = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-8-hydroxyquinoline, H3L2 = 2-[(2-(N'-acetylhydrazino)propanehydrazide)methyl]-8-hydroxyquinoline) were successfully prepared, and structurally and magnetically characterized. Crystal structural analyses reveal that two compounds are isostructural and they all consist of a tetranuclear Ln4 cluster. All Ln(III) ions in them are eight-coordinated and located in a distorted triangular dodecahedron geometry. Magnetic studies indicate that 1 exhibits large magnetocaloric effect with the entropy change (-ΔSm) of 32.10 J Kg−1 K−1 (at T = 2.0 K and ΔH = 7 T), and 2 displays slow magnetic relaxation behaviors.

IN VITRO ANTICANCER, ANTIOXIDANT AND MOLECULAR DOCKING STUDIES OF 4-AMINOBENZAMIDE METAL COMPLEXES

Objective: Mixed ligand complexes of Cu(II) and Cd(II) with 4-aminobenzamide(4-ABZ) have been synthesized under microwave irradiation and they were characterized by elemental analysis, estimation of metal ion, molar conductivity, magnetic study, FT-IR, Far-IR, electronic spectra, NMR (1H and 13C) and EPR spectral studies. Methods: The data of microanalysis and metal estimation showed that the complexes have the composition of [M(L1)2(L2)2] for Cu(II) and [M(L1)(L2)2] for Cd(II) complex respectively. The conductivity data confirmed the neutral nature of the complexes. The tetrahedral geometry of the Cd(II) complex was confirmed using UV-Visible spectra. The tetragonally distorted octahedral stereochemistry of Cu(II) complex was further confirmed by UV and EPR spectral studies. The diamagnetic nature and probable geometry of Cd(II) complex were also confirmed using NMR spectral studies, which are also compared with free 4-aminobenzamide. The in vitro bio-potential activities of 4-ABA and Cd(II) complex were screened for E. coli and C. Albicans microorganisms by Agar disc diffusion methods. Results: The cancer study of Cu(II) complex and antioxidant activity of DPPH free radical scavenging method of Cd(II) complex were measured and compared with 4-aminobenzamide and standard drugs. The breast cancer studies were also identified using the targeted proteins viz., BRCA1, PR and EGFR by molecular docking study. Conclusion: In the present study, we synthesized new metal complexes of Cu(II) and Cd(II) with 4-ABA and nitrite ion by microwave irradiation method. The analytical data show that the metal-ligand stoichiometry they are non-electrolytes in acetonitrile solution. The spectral data show that the synthesized ligand binds with metal ions through the nitrogen atom of the 4-ABA and oxygen atoms of the nitrite ion.

Steric hindrance effect of Schiff-base ligands on magnetic relaxation dynamics and emissive behavior of two dinuclear dysprosium complexes

The self-assembly reactions between mixed-ligand and tetrahydrate dysprosium acetate in the presence of mixed organic solvents lead to two structural similar dinuclear dysprosium complexes with composition formulas of Dy2(L1)2(L2)2(CH3OH)2·CH2Cl2·CH3OH (1) and Dy2(L1)2(L3)2(CH3OH)2·CH3CN (2), where L1, L2 and L3 represent the deprotonated form of 4-tert-butyl-2-(7-methoxybenzo[d]oxazol-2-yl)phenol, (E)-1-(((3,5-di-tert-butyl-2-hydroxyphenyl)imino)methyl)naphthalen-2-ol and (E)-2,4-di-tert-butyl-6-((2-hydroxybenzylidene)amino)phenol. The tiny difference of the core structure of 1 and 2 is derived from the steric hindrance of Schiff base ligands L2 and L3. Dynamic magnetic measurements reveal that 1 and 2 show frequency-dependent out-of-phase alternating-current susceptibility signal peaks at different temperatures under zero dc field, diagnostic of single-molecule magnet behavior. The experimental derived energy barrier to magnetization reversal for 1 and 2 is 108(1), 47(2) and 33(3) K. Ab initio CASSCF calculations performed on 1 and 2 suggest that the origin of the difference in magnetic properties originates from the variation in the single-ion anisotropy that arises due to minor structural variation. Further, the equation to calculate the effective energy barrier for Dy2 proposed earlier is found to yield an excellent agreement with the experimental results. Solid state fluorescence measurements performed on 1 and 2 demonstrate that both exhibit two ligands centered components of fluorescent emissive, in addition, with different emitting colors and chromaticity coordinates. The discrepancy of fluorescence and single molecule magnet behavior showed by 1 and 2 can be attributed to the steric hindrance effect of Schiff base ligands.

Silanol-functionalized tetranuclear copper complex and its nanoscale-heterogenization by immobilization on glass surface from solution

3-Formylsalicylic acid (3-FSA) was treated in a weak acid medium with 1,3-bis(2-aminoethylaminomethyl)tetramethyldisiloxane to form a salen-type ligand, followed by the addition of copper(II) chloride to build the corresponding coordination compound in a one-pot procedure. Along with the CH=N bond formation, Si-O-Si bond was also broken down to form the Si-OH ones tailing the remained monoamine. As single crystal X-ray diffraction revealed, when the copper salt is added, a tetranuclear complex, [Cu4(L1)2(L2)2Cl2(H2O)2], is formed consisting in two asymmetric dinuclear units, [Cu2L1L2Cl(H2O)], in which a molecule of 3-FSA (H2L1) and one of derived azomethine (H2L2), both doubly deprotonated and tridentate, participate in the coordination of oxo-bridged {Cu4} core. The coordination sphere is completed by chlorine atoms and water molecules. In the tetranuclear structure, the azomethine groups and implicitly the silanol arms are located in trans-position. The thermal behavior of the complex was studied by TGA and DSC. Besides the intrinsic properties induced by the presence of the metal ion (magnetic, biological, etc.), the free reactive silanol group may allow post-functionalization of the complex or, as found herein, its chemical binding to a suitable substrate. The attachment of the complex to the glass surface was proven by XPS but also highlighted by MFM due to its intrinsic magnetism.

Solvent mediated photoluminescence responses over mixed-linker cadmium (II) based metal–organic frameworks

Three dimensional mixed-linker cadmium based metal–organic framework (MOF), [Cd2(L1)2(L2)0.5(H2O)]n(1) and {[Cd3(L1a)2(L2)2]⋅H2O}n (2) (L1 = pyrazole-3,5 dicarboxylate, L1a = pyrazolate-3,5 dicarboxylate and L2 = 4,4′-azopyridine) have been synthesized by solvothermal methods. Notably, subtle change in reaction conditions afforded two strikingly different MOFs. Compounds have been characterized structurally by single-crystal X-ray analysis. Both the compounds feature a pillared-layer framework structure. Photoluminescence properties of the framework compounds have been investigated in the solid state as well as in solvent dispersed medium. Interestingly, solvent specific turn-on/turn-off photo-luminescence responses have been observed for both the compounds (1) and (2).

Mono-and Binuclear Cobalt(II) Mixed Ligand Complexes of 2,2’-Bipyridine and Ethylenediamine: Synthesis, Characterization and Biological Application

Antibiotic resistance of pathogens to the current commercially available drugs is a serious problem. To curve this problem, the discovery of active compounds with a new mode of action is insistent. In line with this, we report two new complexes; mononuclear [Co(L1)2(L2)(H2O)]Cl2 and binuclear [Co2(L1)4(L2)(H2O)2]Cl4 using precursor complex, [Co(L1)2(H2O)2]Cl2, synthesized before; where L1: 2,2’-bipyridine and L2: ethylenediamine. The precursor complex was prepared from CoCl2.6H2O and L1 in ethanol, treated with a different mole of L2 under optimized reaction conditions to give the corresponding mono-and binuclear cobalt(II) mixed ligand complexes. These complexes were characterized using the spectroscopic technique (ICP-OES, UV-Vis, FT-IR) and physicochemical methods (chloride determination, thermal analysis, and conductance measurement). Their antibacterial activities were also tested against two Gram-negative (Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae)) and two Gram-positive (Staphylococcus aureus (S. aureus), Streptococcus pyogenes (S. pyogenes)) bacteria using the disc diffusion method. The new complexes showed better activities against K. pneumoniae than the reference Gentamycin. Furthermore, [Co(L1)2(L2)(H2O)]Cl2 demonstrated better activity than Gentamycin against S. aureus and E. coli.

Cis-Locked Ru(II)-DMSO Precursors for the Microwave-Assisted Synthesis of Bis-Heteroleptic Polypyridyl Compounds.

We describe a synthetic strategy for the preparation of bis-heteroleptic polypyridyl Ru(II) complexes of the type [Ru(L1)2(L2)]2+ (L1 and L2 = diimine ligands) from well-defined Ru(II) precursors. For this purpose, a series of six neutral, anionic, and cationic cis-locked Ru(II)-DMSO complexes (2–7) of the general formula [Y] fac-[RuX(DMSO–S)3(O–O)]n (where O–O is a symmetrical chelating anion: oxalate (ox), malonate (mal), acetylacetonate (acac); X = DMSO–O or Cl–; n = −1/0/+1 depending on the nature and charge of X and O–O; when present, Y = K+ or PF6–) were efficiently prepared from the well-known cis-[RuCl2(DMSO)4] (1). When treated with diimine chelating ligands (L1 = bpy, phen, dpphen), the compounds 2–7 afforded the target [Ru(L1)2(O–O)]0/+ complex together with the undesired (and unexpected) [Ru(L1)3]2+ species. Nevertheless, we found that the formation of [Ru(L1)3]2+can be minimized by carefully adjusting the reaction conditions: in particular, high selectivity toward [Ru(L1)2(O–O)]0/+ and almost complete conversion of the precursor was obtained within minutes, also on a 100–200 mg scale, when the reactions were performed in absolute ethanol at 150 °C in a microwave reactor. Depending on the nature of L1 and concentration, with the oxalate and malonate precursors, the neutral product [Ru(L1)2(O–O)] can precipitate spontaneously from the final mixture, in pure form and acceptable-to-good yields. When spontaneous precipitation of the disubstituted product does not occur, purification from [Ru(L1)3]2+ can be rather easily accomplished by column chromatography or solvent extraction. By comparison, under the same conditions, compound 1 is much less selective, thus demonstrating that locking the geometry of the precursor through the introduction of O–O in the coordination sphere of Ru is a valid strategic approach. By virtue of its proton-sensitive nature, facile and quantitative replacement of O–O in [Ru(L1)2(O–O)]0/+ by L2, selectively affording [Ru(L1)2(L2)]2+, was accomplished in refluxing ethanol in the presence of a slight excess of trifluoroacetic acid or HPF6.

Bis (Diamines) Cu and Zn Complexes of Flurbiprofen as Potential Cholinesterase Inhibitors: In Vitro Studies and Docking Simulations

Alzheimer’s disease (AD) causes dementia and continuous damage to brain cells. Cholinesterase inhibitors can alleviate the condition by increasing communication between the nerve cells and reducing the risk of dementia. In an effort to treat Alzheimer’s disease, we synthesized flurbiprofen-based diamines (1,2 diaminoethane and 1,3 diaminopropane) Zn(II), Cu(II) metal complexes and characterized them by single-crystal X-ray analysis, NMR, (FT)-IR, UV-Vis, magnetic susceptibility, elemental analysis and conductivities measurements. Synthesized diamine metal complexes appeared in ionic forms and have distorted octahedral geometry based on conductivity studies, magnetic susceptibility and electronic studies. Single crystal X-ray diffraction analysis confirmed (2b) Cu(H2O)2(L1)2(L2)2 complex formation. Moreover, we tested all synthesized metal complexes against the cholinesterase enzyme that showed higher inhibition potential. In general, copper metal complexes showed higher inhibitory activities than simple metal complexes with flurbiprofen. These synthesized metal complexes may derive more effective and safe inhibitors for cholinesterases.

Construction of a nanoscale Yb(III) Schiff base complex with NIR luminescence response to anions and nitro explosives

A nanoscale Yb(III) complex [Yb6(L1)2(L2)4(OH)4(CF3SO3)2(DMF)2(EtOH)4]·2(CF3SO3)·2OH (1) with Schiff base ligand N,N′-bis(3-methoxysalicylidene)(binaphthyl)-1,4-diamine (H2L1) and salicylaldehyde ligand 3-methoxysalicylaldehyde (H2L2) was synthesized. Upon excitation of the ligand-centered absorption bands, 1 displays typical NIR luminescence of Yb(III). Interestingly, it shows lanthanide luminescence response to anions and nitro explosives, especially with high sensitivity to F− and PA. Meanwhile, the quenching effect of F− and PA to the lanthanide luminescence of 1 is not affected by the existence of other anions and explosives.

Facile synthesis of yellow luminescence from zinc coordination compound based on hydroxyquinoline under the blue-light excitation

In this paper, a novel Zn(L1)2(L2) phosphor with yellow light under blue-light excitation was synthesized using simple one pot method by introducing the second ligand 4-dimethylaminopyridine (L2) to the reaction that uses 5-chloro-8-hydroxyquinoline (L1) and zinc acetate to prepare the coordination compound Zn(L1)2. The structure of Zn(L1)2(L2) was determined with single crystal X-ray diffraction techniques. Besides, the compounds Zn(L1)2 and Zn(L1)2(L2) were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), fluorescence spectroscopy, and thermo-gravimetric analysis (TGA). Compared with the compound Zn(L1)2, the optimal excitation and emission wavelengths of the compound Zn(L1)2(L2) have red-shifted, with the excitation wavelength of 467 nm and the emission wavelength of 574 nm. The special luminescent properties and simple synthesis method of the Zn(L1)2(L2) make it become a promising candidate in the field of white-light-emitting diodes.

Mono and binuclear cobalt(II) mixed ligand complexes containing 1,10-phenanthroline and adenine using 1,3-diaminopropane as a spacer: synthesis, characterization, and antibacterial activity investigations

BackgroundCoordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities.ResultHerein, we report three novel mixed ligand complexes of cobalt(II) having the formulae [Co(L1)2(H2O)2]Cl2, [Co(L1)2(L2)(H2O)]Cl2 and [Co2(L1)4(L2)2(L3)]Cl4 (L1 = 1,10-phenanthroline, L2 = adenine, L3 = 1,3-diaminepropane) were synthesized and characterized by elemental analysis, conductivity measurement, infrared, and UV-Vis spectroscopic techniques. Octahedral geometries are proposed to all the complexes. In vitro antibacterial activities of the ligands, salt, and metal complexes were tested on four pathogenic bacteria (Staphylococcus aureus, Salmonella typhus, Escherichia coli, and Staphylococcus epidermis) using disc diffusion method.ConclusionsIt is interesting to note that the newly synthesized cobalt(II) complexes are active against gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) even though cobalt(II) complexes are well known for their activity against gram positive bacteria.

Multicomponent Self-Assembly of PdII /PtII Interlocked Molecular Cages: Cage-to-Cage Conversion and Self-Sorting in Aqueous Medium.

Coordination-driven self-assembly is an efficient approach for constructing complicated molecules with the aid of reversible bond formation. However, constructing topologically complicated interlocked systems and their formation studies remain challenging tasks. The formation of two water-soluble hexanuclear interlocked cages by multicomponent self-assembly of a flexible triimidazole donor (L1) and a rigid tripyridyl donor (L2) based on a triazine core in combination with 90° cis-blocked PdII and PtII acceptors is reported here. Formation of interlocked systems having a composition of M6 (L1)2 (L2)2 (M=Pd or Pt) becomes feasible through cavity-induced self-recognition of two similar units having a composition of M3 (L1)(L2). Self-sorting of two independently prepared cages of [M3 (L1)2 ] and [M6 (L2)4 ] in aqueous medium leads to the formation of interlocked systems, and their formation was monitored by time-dependent 1 H NMR spectroscopy. Self-recognition of L1 by [M6 (L2)4 ] or L2 by [M3 (L1)2 ] leads to the formation of interlocked systems, as confirmed from 1 H NMR spectroscopic titrations of L1 with cages {M6 (L2)4 } and L2 with {M3 (L1)2 }, respectively. Both the interlocked cages of Pd and Pt are highly stable, and formation of either system is equally probable as observed from the treatments of Pd3 (L1)2 with Pt6 (L2)4 or Pt3 (L1)2 with Pd6 (L2)4 , which lead to the formation of two different self-assembled homometallic interlocked cages [Pt6 (L1)2 (L2)2 +Pd6 (L1)2 (L2)2 ] instead of forming any other heterometallic assemblies. Formation of interlocked cages is dependent on the steric bulk of the diamine ligand bound to the metal acceptors. A N-alkyl-substituted blocking amine prefers the non-interlocked cage instead of the interlocked analogue.

Synergistic effect of mixed ligands on the anisotropy axis of two dinuclear dysprosium complexes.

We present the syntheses, crystal structures, magnetic properties and theoretical calculations performed on two dinuclear dysprosium complexes with formulas Dy2(L1)2(L2)2(CH3CH2OH)(CH3OH) (1) and Dy2(L1)2(L3)2(CH3OH)2·1.5CH3OH (2). Single-crystal X-ray structural data analyses showed that both complexes contain two nonequivalent dysprosium ions bridged by two phenolate oxygen atoms. In both complexes, each dysprosium site adopts a N2O6 coordination constitution and triangular dodecahedron (D2d) configuration geometry with different distortion degree. Both complexes display single-molecule magnet behavior manifested by frequency-dependent out-of-phase alternating current susceptibility signal peaks under a zero-applied dc field. The effective energy barrier of the magnetization reversal and relaxation time values are 61 K, 7.1 × 10-6 s (1) and 51 K, 1.9 × 10-6 s (2), respectively. Theoretical calculations revealed a drastic discrepancy between the orientations of the anisotropy axis of the Dy2 ion observed in these two dinuclear complexes, resulting from the different spatial arrangements of the mixed ligands in the core structure.

Intramolecular Electron Transfers in a Series of [Co2Fe2] Tetranuclear Complexes.

Discrete cyanide-bridged Co-Fe multinuclear complexes can be considered as functional units of bulk Co-Fe Prussian blue analogues, and they have been recognized as a new class of switching molecules in the last decade. The switching property of the cyanide-bridged Co-Fe complexes is based on intramolecular electron transfers between Co and Fe ions, and we herein refer to this phenomenon as an electron transfer-coupled spin transition (ETCST). Although there have been numerous reports on the complexes exhibiting ETCST behavior, the systematic study of the substituent effects on the thermal ETCST equilibrium in solution has not been reported yet, and the rational control of the equilibrium temperature remains challenging. We report here the syntheses and thermal ETCST behavior both in the solid state and solution for a series of tetranuclear [Co2Fe2] complexes, [Co2Fe2(CN)6(L1)2(L2)4]X2 (L1 and L2: tri- and bidentate capping ligands for Fe and Co ions, X: counteranions). All complexes showed thermal ETCST equilibrium between high-spin ([(hs-CoII)2(ls-FeIII)2]) and low-spin ([(ls-CoIII)2(ls-FeII)2]) states in butyronitrile, and the equilibrium temperatures (T1/2) showed systematic shifts by chemical modifications and chemical stimuli. The T1/2 values were correlated with the redox potential differences (ΔE) of the Fe and Co ions in the constituent units, and the larger ΔE values led to the lower T1/2. The present result suggests that the thermal ETCST behavior in solution can be rationally designed by considering the redox potentials of the constituent molecules.

Redox-Active Organoruthenium(II)– and Organoosmium(II)–Copper(II) Complexes, with an Amidrazone–Morpholine Hybrid and [CuICl2]− as Counteranion and Their Antiproliferative Activity

A novel proligand HLH has been prepared from 2-pyridinamidrazone and 6-(morpholinomethyl)pyridine-2-carboxaldehyde. Subsequently, starting from HLH and CuCl2·2H2O in the presence of triethylamine, a series of homo- and heterometallic complexes with [CuICl2]− as counteranion, namely mononuclear complex [CuIICl(HLOMe)][CuICl2] (1), dinuclear Ru(II)–Cu(II) complex [CuIIRuII(η6-p-cymene)Cl2(LH)][CuICl2]·1.5H2O (2·1.5H2O), Os(II)–Cu(II) complex [CuIIOsII(η6-p-cymene)Cl2(LH)][CuICl2]·H2O (3·H2O), and tetranuclear complex [CuII4(L1)2(L2)2Cl2]·5MeOH (4·5MeOH), where HLOMe, L1, and L2 are Schiff base ligands derived from HLH, were synthesized. The structures of metal complexes were established by X-ray diffraction. Complexes 1–3 demonstrated quasireversible one-electron reduction of Cu(II) in complex cations and one-electron oxidation of [CuICl2]− counterion, confirmed by UV–vis and EPR spectroelectrochemical measurements. They exhibited moderate antiproliferative activity against ovarian carcinoma and cervical ad...