Secondary Amine Nitrogen Atoms Research Articles

Synthesis, characterization, DFT and biological studies of Fe(II), Cu(II), and Zn(II) complexes of keto-imine chelators

Three naphthoquinone-based chelators, 2-(pyrimidin-2-ylamino)-2,3-dihydronaphthalene-1,4-dione (HLa) 2-((4,6-dihydroxypyrimidin-2-yl)amino-2,3-dihydronaphthalene-1,4-dione (HLb), and 2-((4,6-dimethylpyrimidin-2-yl)amino-2,3-dihydronaphthalene-1,4-dione (HLc), have been synthesized by the reaction of 2-hydroxy-1,4-napthoquinone with 2-aminopyrimidine, 2-amino-4,6-dihydroxypyrimidine, and 2-amino-4,6-dimethypyrimidine respectively. Reaction of the chelators with Fe2+; Cu2+ and Zn2+ sulphate; and acetate salts; plus 2,2′-bipyridine(B) gave the resultant heteroleptic M2+ complexes, which were characterized by analytical, 1H-and 13C NMR, FT-IR, UV–vis, ESI-MS, and TG-DSC analyses. The FT-IR and NMR results showed that the chelators are bidentate and chelated with the M2+ ions via their ketonic oxygen (>CO) and secondary amine nitrogen (HN) atoms. The μeff data and UV–vis spectral evaluations of the complexes provided credence to the 6-coordinate octahedral geometries of the complexes. DFT calculations were performed to understand the mode of complex formation as well as their geometry around the metal centers. Compared to the chelators, the heteroleptic complexes have improved antimicrobial actions attributed to the extra 2-nitrogenous atoms in the 2,2′-bipyridine moiety and the presence of active metal ions. The CuLc complexes displayed the best antibacterial performance with inhibitory effects of 34.0 mm. However, the ZnLb complexes recorded the best antifungal activity (33.0 mm), due to the absorption of Zn2+ ions on the surface of the fungiform cell walls. The antioxidant assays with ferrous ions show that all the keto-imine chelators showed good chelating abilities. HLc showed values of 78.76 plus 74.5 % separately at concentrations of 200 and 100 mg/mL, which are higher than that of the standard ascorbic acid. The DPPH radical scavenging activities of the heteroleptic complexes indicate that they can be used for the synthesis of drugs for the treatment of pathological diseases arising from oxidative stress.

Engineering strong electronegative nitrogen-rich porous organic polymer for practical durable lithium-sulfur battery

The practical application of porous organic polymers (POPs) in Li–S batteries (LiSBs) is severely hampered by low sulfur loading and weak chemisorption. Here, a novel organosulfur copolymer host (POP@F/S) with polar nitrogen-rich heteroatoms is prepared by in situ anchoring of sulfur in 3D perfluorinated hierarchical porous polymers via nucleophilic aromatic substitution reaction (SNAr) reaction. The design of hierarchical pore structure with high porosity not only offers strong physical confinement to polysulfide species but also increase the sulfur loading and buffer the volume change during lithiation. Notably, calculations and experimental results indicate that the triazine and secondary amine nitrogen atoms containing lone electron pairs can act as Lewis base sites to strongly interact with the terminal lithium ions in lithium polysulfide, thereby suppressing the shuttle effect. Attributed to these merits, LiSBs with POP@F/S composite cathode exhibit excellent rate capability and ultra-low capacity decay of only 0.019% per cycle after 500 cycles at 1C. Even more excitingly, a desirable areal capacity of 8.65 mAh cm−2 is delivered when with 7.9 mg cm−2 sulfur loading, and a satisfactory lifetime of over 150 cycles is maintained even under lean electrolyte (E/S = 5 μL mg−1), demonstrating remarkable potential in developing high-performance LiSBs.

A turn-on fluorescence sensor based on Cu2+ modulated DNA-templated silver nanoclusters for glyphosate detection and mechanism investigation

The abuse application of glyphosate can result in a potential hazard for environment and human, however its ultrasensitive detection remains challenging. Herein, a Cu2+ modulated DNA-templated silver nanoclusters (DNA-AgNCs) sensor was constructed to sensitively determine glyphosate based on the turn-on fluorescence strategy. The fluorescence quenching of DNA-AgNCs occurred with the existence of Cu2+. Upon the presence of glyphosate, the functional groups on the surface of glyphosate could chelate with Cu2+, following the fluorescence recovery of DNA-AgNCs. Through the stoichiometric methods, we unveil that Cu2+-trigged fluorescence quenching mode is a combination of static and dynamic quenching with the static mode being predominant. In DNA-AgNCs/Cu2+ system, the carboxylate, amine, and phosphonate groups of glyphosate interact with Cu2+ through chelation, in which the carboxylate oxygen, the phosphonate oxygen atoms, and the monoprotonated secondary amine nitrogen atom and Cu2+ form chelate rings. This fluorescence sensor showed a desired linearity of glyphosate analysis under the optimum conditions, ranging from 15 to 100 μg/L with a low detection down to 5 μg/L. Moreover, the proposed sensor was successfully utilized to measure glyphosate in real samples, indicating a promising application in pesticide residues detection.

Removal of Cr(III) from aqueous solution by silica-gel/PAMAM dendrimer hybrid materials.

Water pollution caused by Cr(III) is a serious environmental problem which bring adverse effect to environmental protection and public safety. Efficient removal of Cr(III) from aqueous solution is important for the remediation of Cr(III) pollution. Herein, a series of silica-gel/polyamidoamine (PAMAM) dendrimer hybrid materials (SG-G0~SG-G4.0) were used for the removal of Cr(III) from aqueous solution. The factors that affect the adsorption were extensively studied and the adsorption mechanism was demonstrated based on the experimental results and density functional theory (DFT) calculation. Result demonstrates the adsorption capacity of ester-terminated silica-gel/PAMAM dendrimers follow the order of SG-G2.5 > SG-G3.5 > SG-G1.5 > SG-G0.5, while that of amino-terminated ones decrease in the order of SG-G2.0 > SG-G4.0 > SG-G3.0 > SG-G1.0 > SG-G0. The highest adsorption is achieved at pH 4.0 for both ester- and amino-terminated materials. Adsorption kinetic indicates the adsorption equilibrium can be reached at about 240 and 180 min for amino- and ester-terminated hybrids, respectively. Adsorption kinetic can be well fitted by pseudo-second-order kinetic model with film diffusion process as the rate-limiting step. Adsorption isotherm follows Langmuir model with monolayer adsorption behavior. Fourier transform infrared spectra (FTIR) indicate the adsorption of Cr(III) by PAMAM dendrimer mainly involve the participation of N-H and C=O groups. DFT calculation demonstrates the uptake of Cr(III) by ester-terminated adsorbents mainly involves carbonyl oxygen and secondary amine nitrogen atoms to form tetra-coordinated chelate, while that of amino-terminated one tends to form hexa-coordinated chelates by carbonyl oxygen, primary and secondary amine nitrogen atoms.

Removal of Co(II) from fuel ethanol by silica-gel supported PAMAM dendrimers: Combined experimental and theoretical study

Silica-gel supported PAMAM dendrimers (SiO2-G0.5∼SiO2-G3.0) were used for the removal of Co(II) from fuel ethanol by batch method. The adsorption mechanism was revealed by combining the results of experiment and density functional theory (DFT) calculation. Results indicated the adsorption capacity was closely related with the generation number of PAMAM dendrimer, contact time, Co(II) concentration, and temperature. Amino-terminated PAMAM dendrimers exhibited better adsorption performance than the corresponding ester-terminated ones. Kinetic adsorption followed pseudo-second-order model and dominated by film diffusion. Isotherm adsorption can be well depicted by Langmuir isotherm model and proceeded by chemical mechanism. Thermodynamic parameters implied the adsorption was spontaneous, endothermic, and randomness incremental process. DFT calculation demonstrated that ester-terminated PAMAM tended to chelate with Co(II) by secondary amine nitrogen atoms and carbonyl oxygen atoms in a quadri-coordinated manner, while amino-terminated PAMAM preferred to act as tetradentate and pentadentate ligand to bind Co(II) with secondary amine nitrogen atom, carbonyl oxygen atom, and primary amine nitrogen atom. Charge transfer of the adsorption process mainly occurred from PAMAM dendrimer to Co(II).

Acid-Base Interactions of Polystyrene Sulfonic Acid in Amorphous Solid Dispersions Using a Combined UV/FTIR/XPS/ssNMR Study.

This study investigates the potential drug-excipient interactions of polystyrene sulfonic acid (PSSA) and two weakly basic anticancer drugs, lapatinib (LB) and gefitinib (GB), in amorphous solid dispersions. Based on the strong acidity of the sulfonic acid functional group, PSSA was hypothesized to exhibit specific intermolecular acid-base interactions with both model basic drugs. Ultraviolet (UV) spectroscopy identified red shifts, which correlated well with the color change observed in lapatinib-PSSA solutions. Fourier transform infrared (FTIR) spectra suggest the protonation of the quinazoline nitrogen atom in both model compounds, which agrees well with data from the crystalline ditosylate salt of lapatinib. X-ray photoelectron spectroscopy (XPS) detected increases in binding energy of the basic nitrogen atoms in both lapatinib and gefitinib, strongly indicating protonation of these nitrogen atoms. (15)N solid-state NMR spectroscopy provided direct spectroscopic evidence for protonation of the quinazoline nitrogen atoms in both LB and GB, as well as the secondary amine nitrogen atom in LB and the tertiary amine nitrogen atom in GB. The observed chemical shifts in the LB-PSSA (15)N spectrum also agree very well with the lapatinib ditosylate salt where proton transfer is known. Additionally, the dissolution and physical stability behaviors of both amorphous solid dispersions were examined. PSSA was found to significantly improve the dissolution of LB and GB and effectively inhibit the crystallization of LB and GB under accelerated storage conditions due to the beneficial strong intermolecular acid-base interaction between the sulfonic acid groups and basic nitrogen centers.

An asymmetrical dinuclear copper(II) β-amino-oxime/oximato-diamine compound with Cu–(OH)–Cu and Cu–(N–O)–Cu bridging; [Cu2(detenoxH)(detenox)(OH)](ClO4)2 (detenoxH = 4,4-dimethyl-7-(N,N-diethylamine)-5-azaheptan-2-one oxime)

The dark blue compound [Cu2(detenoxH)(detenox)(OH)](ClO4)2 (detenoxH=4,4-dimethyl-7-(N,N-diethylamine)-5-azaheptan-2-one oxime), [Cu2(C12H27N3O)(C12H26N3O)(OH)](ClO4)2, is formed by reaction of (N,N-diethyl-ethane-1,2-diamine)copper(II) perchlorate, 4-methylpent-3-ene-2-one oxime and base. The asymmetrical dinuclear cation has ion Cu1 in asymmetrical square pyramidal coordination by the oxime nitrogen atom (Cu1–Noxime=2.041(3)Å) and the secondary amine nitrogen atom (Cu1–Nsecondary=1.995(3) Å) of a detenoxH ligand, the bridging oximato oxygen atom of the detenox− ligand bonded to Cu2 (Cu1–Ooximato=1.928(2)Å) and the bridging OH− ion (Cu1–OOH=1.928(3)Å) with rms displacements from the N2O2 plane±0.246(1) with Cu1 in the plane). The tertiary amine nitrogen atom of the detenoxH ligand is weakly coordinated axially (Cu1–Ntertiary=2.328(3)Å). Ion Cu2 is in tetrahedrally twisted square-planar coordination by a detenox− ligand, with Cu2–Noxime=1.992(3), Cu2–Nsecondary=1.979(3), Cu2–Ntertiary=2.053(3), and by the bridging hydroxide ion (Cu2–O=1.878(3)Å), with rms displacements from the N3O best plane ±0.178(2)Å, with Cu2 in the plane). The dinuclear cation has Cu1–O=N–Cu2 bridging by the oximato group of detenox− and Cu1–(OH)–Cu2 bridging by a hydroxide ion, with Cu⋯Cu=3.3136(6)Å. The components of the dinuclear cation are further linked by a hydrogen bond between the oxime OH and oximato O− groups. The effective magnetic moment of 2.21 B.M. indicates that there is no significant spin coupling.

Synthesis, X-ray crystal structures, spectroscopic and electrochemical studies of Zn(II), Cd(II), Ni(II) and Mn(II) complexes of N1,N4-bis(pyridoxylidene)triethylenetetramine

Zn(II), Cd(II), Ni(II) and Mn(II) complexes of a new hexadentate ligand N1,N4-bis(pyridoxylidene)triethylenetetramine have been synthesized. X-ray crystal structures show that in all the complexes the metal: ligand stoichiometry is 1:1 and the ligand coordinates in a di-deprotonated hexadentate manner through two phenolate oxygens, two imine nitrogens and two secondary amine nitrogen atoms. Fluorescence spectroscopy shows that the ligand centered emission undergoes threefold enhancement of intensity on complexation with Zn(II) ion, whereas it is quenched or remains unaffected in presence of various biologically relevant divalent metal ions. The Zn(II) specific fluorescence enhancement indicates that the ligand may be used as a fluorogenic sensor for Zn(II) in biological systems, with a sensitivity of detection of 10−8M. The electronic structures of the ligand as well as the complexes and their UV–Vis absorption spectra are explained on the basis of DFT and TD-DFT calculations respectively. It is found that that covalence of the metal ligand bond follows the order Ni(II)⋙Mn(II)>Zn(II)≈Cd(II).

Macrobicyclic Cage Amine Ligands for Copper Radiopharmaceuticals: A Single Bivalent Cage Amine Containing Two Lys3-bombesin Targeting Peptides

The synthesis of new cage amine macrobicyclic ligands with pendent carboxylate functional groups designed for application in copper radiopharmaceuticals is described. Reaction of [Cu((NH(2))(2)sar)](2+) (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) with either succinic or glutaric anhydride results in selective acylation of the primary amine atoms of [Cu((NH(2))(2)sar)](2+) to give derivatives with either one or two aliphatic carboxylate functional groups separated from the cage amine framework by either a four- or five-atom linker. The Cu(II) serves to protect the secondary amine nitrogen atoms from acylation, and can be removed to give the free ligands. The newly appended carboxylate functional groups can be used as sites of attachment for cancer-targeting peptides such as Lys(3)-bombesin. The synthesis of the first dimeric sarcophagine-peptide conjugate, possessing two Lys(3)-bombesin peptides tethered to a single cage amine, is presented. This species has been radiolabeled with copper-64 at ambient temperature and there is minimal dissociation of Cu(II) from the conjugate even after two days of incubation in human serum.

The preparation and structure of [trans-dichloro-{trans-6,13-dimethyl-6,13-bis-(N,N-dimethylformamidinyl)-1,4,8,11-tetraazacyclotetradecane}nickel(II)] diperchlorate dihydrate

Abstract Reaction of (trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II) perchlorate with oxalyl chloride in dimethylformamide forms trans-dichloro-(trans-6,13-dimethyl-6,13-bis(N,N-dimethylformamidinyl)-1,4,8,11-tetraazacyclotetradecane)nickel(II) diperchlorate dihydrate. This has a centrosymmetrical cation with nickel(II) in octahedral coordination by the four secondary amine nitrogen atoms of the macrocycle, and with chloride ions coordinated axially. The 6,13-diamino substituents have been converted to N,N-dimethylformamidinyl ( C N+H=CH N(Me)2) substituents, which are equatorially oriented. The N C and C N distances of the formamidinyl group are approximately equal, with bond angles about the C and two N atoms all near 120°, with the group C(Me) NH CH N(Me)2 approximately coplanar, indicating approximately equal contributions from the canonical forms CH NH CH=N+(Me)2 and C N+H=CH N(Me)2.

Iron(III) complexes of N2O and N3O donor ligands as functional models for catechol dioxygenase enzymes: ether oxygen coordination tunes the regioselectivity and reactivity

A series of mononuclear iron(III) complexes of the type [Fe(L)Cl(3)], where L is a systematically modified N(2)O or N(3)O ligand with a methoxyethyl/tetrahydrofuryl ether oxygen donor atom, have been isolated and studied as models for catechol dioxygenases. The X-ray crystal structures of [Fe(L2)Cl(3)] 2, [Fe(L6)Cl(3)] 6, [Fe(L5)(TCC)Cl] 5a, where H(2)TCC = tetrachlorocatechol, [Fe(L6)(TCC)Br] 6a, and the μ-oxo dimer [{Fe(L6)Cl}(2)O](ClO(4))(2) 6b have been successfully determined. In [Fe(L2)Cl(3)] 2 the N(2)O ligand is facially coordinated to iron(III) through the pyridine and secondary amine nitrogen atoms and the tetrahydrofuryl oxygen atom. In [Fe(L6)Cl(3)] 6, [Fe(L5)(TCC)Cl] 5a and [Fe(L6)(TCC)Br] 6a the N(3)O donor ligands L5 and L6 act as a tridentate N3 donor ligand coordinated through two pyridine and one secondary amine nitrogen atoms, whereas the ether oxygen is not coordinated. The spectral and electrochemical properties of the adducts [Fe(L)(DBC)Cl] of 1-8, where H(2)DBC = 3,5-di-tert-butylcatechol, in DMF and their solvated adduct species [Fe(L)(DBC)(Sol)](+), where Sol = DMF/H(2)O, generated in situ in dichloromethane, respectively, have been investigated. The product analysis demonstrates that the adducts [Fe(L)(DBC)Cl] effect cleavage of catechol in the presence of O(2) in DMF to give mainly the intradiol (I) product with a small amount of the extradiol (E) product (E/I, 0.2:1-0.7:1). Interestingly, the solvated species [Fe(L)(DBC)(Sol)](+) derived from 1-4 cleave H(2)DBC to provide mainly the extradiol cleavage products with lower amounts of intradiol products (E/I, 2.3:1-4.3:1) in dichloromethane. In contrast, the solvated species [Fe(L)(DBC)(Sol)](+) derived from 5-8 cleave H(2)DBC to provide both extradiol and intradiol products (E/I, 0.6:1-2.3:1) due to the involvement of the ether oxygen donor of the methoxyethyl/tetrahydrofuryl arm in the coordination to iron(III) upon removal of a chloride ion.

A hexadentate bis(thiosemicarbazonato) ligand: rhenium(v), iron(iii) and cobalt(iii) complexes

A new 1,3-diaminopropane bridged bis(thiosemicarbazone) ligand (H(4)L) has been synthesised. The new hexadentate ligand is capable of forming six coordinate complexes with rhenium(V), iron(III) and cobalt(III). In the case of the iron(III) and cobalt(III) complexes the ligand doubly deprotonates to give the monocations [Fe(III)(H(2)L)](+) and [Co(III)(H(2)L)](+) in which the metal ion is in a distorted octahedral environment. In the rhenium(V) complex the ligand loses four protons by deprotonation of both secondary amine nitrogen atoms to give [Re(V)(L)](+) with the metal ion in a distorted trigonal prismatic coordination environment. [Re(V)(L)](+) represents a rare example of a rhenium(V) complex that does not contain one of the ReO(3+), ReN(2+) or Re(NPh)(2+) cores. The new ligand and metal complexes have been characterised by a combination of NMR spectroscopy, X-ray crystallography, mass spectrometry and microanalysis. The electrochemistry of [Fe(III)(H(2)L)](+), [Co(III)(H(2)L)](+) and [Re(V)(L)](+) has been investigated by cyclic voltammetry with each complex undergoing a single electron reduction event. It is possible to prepare the rhenium(V) complex from ReOCl(3)(PPh(3))(2) or directly from [ReO(4)](-) with the addition of a reductant, which suggests the new ligand may be of interest in the development of rhenium radiopharmaceuticals.

Synthesis and structures of (13-hydroxylamino-5,7,7,13-tetramethyl-1,4,8,11-tetraazacyclotetradec-4-ene-κ 4)nickel(II) tetrachlorozincate(II) and (13-azonium-5,5,7,13-tetramethyl-1,4,8,11-tetraazacyclotetradecane-κ 4)nickel(II) tetrachlorozincate(II) chloride 2.25 water

Zinc/acid reduction of the nitro function of (5,7,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II) yields (13-hydroxylamino-5,7,7,13-tetramethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II), isolated as the tetrachlorozincate salt, for which the structure is reported. This has singlet ground state nickel(II) in square-planar coordination by the three amine and the imine nitrogen atoms of the macrocycle. There is no interaction between the nickel(II) ion and the axially oriented hydroxylamino group. Zinc/acid reduction of the nitro function of (5,5,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradecane)nickel(II) yields (13-amino-5,5,7,13-tetramethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II), isolated from acid solution as (13-azonium-5,5,7,13-tetramethyl-1,4,8,11-tetraazacyclotetradecane-κ 4)nickel(II) tetrachlorozincate(II) chloride 2.25 water, for which the structure is reported. The two independent cations have singlet ground state nickel(II) in square-planar coordination by the four secondary amine nitrogen atoms of the macrocycle, with the protonated amine substituent axially oriented. The cations of both compounds show disorder in the location of the axial methyl component of the gem-dimethyl group, manifest as reversal of the trimethyl substituted 1,3-amine-imine or 1,3-diamine chelate rings, arising from co-crystallisation of enantiomers.

Syntheses and crystal structures of copper mixed-ligand complexes of multidentate enaminones and acetate anions

Reactions of ferrocenoylacetone with 2-(aminomethyl)pyridine and N-(2-hydroxyethyl)-1,2-diaminoethane afford the multidentate enaminones H L 1 and H 3 L 2, respectively. Reactions of copper acetate with the two enaminones generate the corresponding mixed-ligand complexes I and II, which are formulated as [Cu L 1(OAc)] and [Cu(H 2 L 2)(OAc)], respectively. The structures of H L 1, I and II have been determined by single-crystal X-ray crystallography. In complex I, H L 1 acts as a monoanionic tridentate donor via the carbonyl oxygen, deprotonated enamine nitrogen and pyridyl nitrogen atoms, the acetate anion is monodentate and the coordination geometry of the central metal is square planar. In complex II, H 3 L 2 is a monoanionic tetradentate ligand via the carbonyl oxygen, deprotonated enamine nitrogen, secondary amine nitrogen and hydroxy oxygen atoms, the acetate anion is monodentate and the coordination geometry of the central metal is a distorted trigonal bipyramid.

The synthesis and structure of trans-di(cyano-κ 1)-( trans-6,13-dimethyl-6,13-bis(propionylamido)-1,4,8,11-tetraazacyclotetradecane-κ 4)cobalt(III) perchlorate dihydrate

trans-Di(cyano-κ 1)-( trans-6,13-dimethyl-6,13-bis(propionylamido)-1,4,8,11-tetraazacyclotetradecane-κ 4)cobalt(III) perchlorate dihydrate, trans-[Co(C 18H 38N 6O 2)(CN) 2)]ClO 4 · 2H 2O, is formed by reaction of trans-[Co(diam)(CN) 2]ClO 4 · 2H 2O (diam = trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane) with propionic anhydride in DMF. The centrosymmetrical cation has the azamacrocycle in planar coordination by the four secondary amine nitrogen atoms of the azamacrocycle, with Co–N = 1.979(2) and 1.968(2) Å and with trans cyano groups with Co–C = 1.920(2) Å. The propionylamido substituents are axially oriented, with the terminal methyl group disordered over two sites.

Synthesis, characterization and X-ray crystal structures of cyclam derivatives. Part VI. Proton binding studies of a pyridine-strapped 5,12-dioxocyclam based macrobicycle

The 14-membered cyclic diamide 1,4,8,11-tetraazacyclotetradecane-5,12-dione (5,12-dioxocyclam) can be considered as a trans-autodiprotected tetraazamacrocycle and provides a convenient starting material for the preparation of macrobicyclic receptors. As an example, the secondary amine nitrogen atoms located at the 1 and 8 positions were cross-bridged with a 1,3-pyridyl strap, affording the constrained ansa-dioxocyclam ligand 1,9,12,18,22-pentaazatricyclo[7.6.6.13,7]docosa-3,5,7(22)-triene-13,19-dione (L1). The proton binding properties of this cage-type compound, which possesses a hemispherical cavity, were fully investigated by spectroscopic (IR, NMR, UV, MALDI-TOF MS), quantum chemical, and potentiometric methods. While both bridgehead tertiary amines have their free lone pairs oriented inside the cavity, intramolecular hydrogen bonding was found to play a key role in determining the structural features of the free base and its protonated forms. L1 behaves as a diprotic base in water with log K011 = 8.94(1) and log K012 = 2.32(9), but most interestingly shows slow proton-transfer rates on the NMR timescale.

Blue dimetallic complexes of two heavy metal ions Cd(II) and Hg(II) with an extended nitrogen donor ligand. Preparation, spectral characterization, and crystallographic studies.

In methanol, the metal salts CdCl2.H2O and HgCl2 react instantaneously with the deprotonated ligand, L-, producing molecular dimetallic ink-blue complexes of general formula M2Cl2L2, M=Cd(II), (1) and Hg(II), (2) (HL=2-[2-(pyridylamino)phenylazo]pyridine). Crystal structures of these two complexes are reported. The coordination sphere around each Cd(II) ion in 1 is a distorted square pyramidal. The metal ion (Cd1) sits above the basal plane of three nitrogen atoms, N(1), N(3), and N(4). The second cadmium ion (Cd2) in this compound lies below the plane of three nitrogen atoms, N(6), N(8), and N(9). The apical positions are occupied by two Cl atoms. Secondary intramolecular interactions between the metal ions and the anionic secondary amine nitrogen atoms (N(4) and N(9)) are noted. The geometry of each Hg(II) ion in the mercury complex, Hg2Cl2L2.0.5H2O, is also distorted square based pyramid with the metal ions lying out of planes of the three nitrogen atoms of the chelating ligands. Secondary Hg(1)...N(1A) (deprotonated amine) interactions are noted. The separation between the two Hg(II) ions in this complex is within the sum of their van der Waals radii. Solution properties of these blue complexes are reported. The origin of the intense blue color in these complexes is the intraligand transitions that occur near 615 nm. 1H NMR of Hg2Cl2L2.0.5H2O indicates that it undergoes exchange in solution with the coordinated ligands.

Synthesis, characterization, and molecular structure of a gallium(III) complex of an amine-phenol ligand with activity against chloroquine-sensitive Plasmodium falciparum strains

Emergence of chloroquine-resistant Plasmodium falciparum strains necessitates discovery of novel antimalarial drugs, especially if the agents can be synthesized from commercially available, inexpensive precursors via short synthetic routes. While exploring structure–activity relationships, we found a gallium(III) complex, [{1,12-bis(2-hydroxy-5-methoxybenzyl)-1,5,8,12-tetraazadodecane}-gallium(III)] + [Ga-5-Madd] +, 1, that possessed antimalarial efficacy. Like previously reported complexes, the crystal structure of 1 revealed gallium(III) in a symmetrical octahedral environment surrounded by four secondary amine nitrogen atoms in equatorial plane and two axial oxygen atoms. In contrast to a previously reported complex, [Ga-3-Madd] +, this novel metallo-antimalarial 1 possessed modest efficacy against chloroquine-sensitive HB3 Plasmodium lines. Thus, slight variation in the positions of methoxy functionalities on the aromatic rings of the organic scaffold dramatically altered specificity thereby suggesting a targeted (e.g., transporter- or receptor-mediated) rather than non-specific (e.g., pH or other gradient-mediated) mechanism of action for these agents.

Complexation of copper ions by DETA-terminated magnetic carriers

It has been shown that diethylenetriamine (DETA)-functionalized magnetic carriers are able to complex copper ions from dilute streams. Complexometric titration using a copper selective electrode indicates the complexation of 0.52 μmol of Cu 2+ per 50 mg of magnetic carriers. This loading capacity is equivalent to the removal of 100 ppm of copper ions from a 1-liter solution by 3 g of magnetic carriers. X-ray photoelectron spectroscopy (XPS) results confirm the presence of Cu 2p bands, indicating the loading of copper ions. A shift of the nitrogen N 1s bands to higher binding energies confirms the involvement of secondary amine and amide nitrogen atoms from DETA-functionalized carriers in copper complexation.

Di-μ-olato dinuclear copper(II) compounds. The structure of bis-μ-O-[(4,6,6-trimethyl-9-(pyridin-2-yl)-3,7-diazanon-3-en-1-olato)copper(II)] perchlorate

Preparations are reported for blue-green[{Cu(pyen)(eto)}2](ClO4)2[pyen is 2-(2-aminoethyl)pyridine, eto– isdeprotonated 2-aminoethanol] and of green[{Cu(pyaceto)}2](ClO4)2,formed by reaction of this compound with acetone[pyaceto– is deprotonated4,6,6-trimethyl-9-(pyridin-2-yl)-3,7-diazanon-3-en-1-ol]. The structureof[{Cu(pyaceto)}2](ClO4)2shows a unit cell containing two independent, but closely similar,centrosymmetrical dinuclear diolato-bridged cations. The copper(II) ions arein square pyramidal coordination, with the two bridging oxygen atoms, and theimine and secondary amine nitrogen atoms in the basal plane, with the pyridinenitrogen atom more weakly coordinated axially. Mean dimensions for the twocations are Cu–Cu# 2.99, Cu–Nbasal 2.01,Cu–O 1.96, Cu–Naxial 2.24 Å,O–Cu–O# 99, Cu–O–Cu# 81, C–O–Cu110, C–O–Cu# 130˚[C30H46Cl2Cu2N6O10,monoclinic, space group P21/n, a 13.487(1),b 13.356(1), c 20.921(2) Å,β 103.235(3)˚, R1 = 0.0516 for 4694reflections]. Magnetic susceptibilities (100–300 K) showantiferromagnetic spin coupling for[{Cu(pyaceto)}2](ClO4)2and[{Cu(pyen)(eto)}2](ClO4)2with singlet–triplet level separation J of–110(10) and –65(10) cm–1,respectively, indicating that[{Cu(pyen)(eto)}2](ClO4)2also has a dinuclear structure.