Syntheses, structures and photophysical properties of a series of Zn-Ln coordination polymers (Ln = Nd, Pr, Sm, Eu, Tb, Dy)

Six novel heterometallic Zn-Ln coordination polymers {[ZnLnCl(pydc)₂(H₂O)₆]·3H₂O}_n (Ln = Nd 1, Pr 2, Sm 3, Eu 4, Tb 5, Dy 6; pydc = pyridine-2,5-dicarboxylate) were synthesized by the hydrothermal method, and their structures were measured by the single-crystal X-ray diffraction. The IR and UV-Vis-NIR absorption spectra, and the luminescence spectra in the visible and near-infrared (NIR) regions of the six complexes were determined at room temperature. They possess the same crystal structure, and the Zn(II) and Ln(III) ions in each complex are bridged into 1D infinite chain by pyridine-2,5-dicarboxylates. Meanwhile, there are numerous hydrogen bonds which result in the 3D hydrogen bonding network in the crystal. In the visible and NIR regions, the emission spectra of the complexes show the characteristic bands of the corresponding Ln(III) ions, which are mainly attributed to the sensitization from the d-L-moiety to f-L-moiety after forming the Zn-Ln complexes. In this paper, we first report the Zn-Sm complex which can exhibit the emission bands of Sm(III) in the NIR region, and discuss the sensitization from the d-L-moiety to f-L-moiety on the basis of the different characteristics of levels for different Ln(III) ions.     

New complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin

New solid complex compounds of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) ions with morin were synthesized. The molecular formula of the complexes is Ln(C₁₅H₉O₇)₃ · nH₂O, where Ln is the cation of lanthanide and n = 6 for La(III), Sm(III), Gd(III) or n = 8 for Ce(III), Pr(III), Nd(III) and Eu(III). Thermogravimetric studies and the values of dehydration enthalpy indicate that water occurring in the compounds is not present in the inner coordination sphere of the complex. The structure of the complexes was determined on the basis of UV-visible, IR, MS, ¹H NMR and ¹³C NMR analyses. It was found that in binding the lanthanide ions the following groups of morin take part: 3OH and 4CO in the case of complexes of La, Pr, Nd, Sm and Eu, or 5OH and 4CO in the case of complexes of Ce and Gd. The complexes are five- and six-membered chelate compounds.     

Structure and magnetic properties of Ln2[Cu(opba)]3(DMSO)6(H2O) · (H2O) compounds with LnLa-Lu exhibiting ladder-like molecular motifs

The reaction of Ln(III) ions with the precursor [Cu(opba)]²⁻ in DMSO has afforded a series of isostructural compounds of general chemical formula Ln₂[Cu(opba)]₃(DMSO)₆(H₂O) · (H₂O), where Ln(III) stands for a lanthanide ion and opba stands for ortho-phenylenebis(oxamato). The crystal structure has been solved for the Gd(III) containing compound. It crystallizes in the orthorhombic system, space group Pbn2₁ (No. 33) with a = 9.4183(2) Å, b = 21.2326(4) Å, c = 37.9387(8) Å and Z = 4. The structure consists of ladder-like molecular motifs parallel to each other. To the best of our knowledge, this is the first Ln(III)Cu(II) coordination polymer family exhibiting the same crystal structure over the whole lanthanide series. The magnetic properties of the compounds have been investigated and the magnetic behavior of the Gd(III) containing compound was studied in more detail.     

Complexes of the highly preorganized ligand PDALC (2,9-bis(hydroxymethyl)-1,10-phenanthroline) with trivalent lanthanides. A thermodynamic and crystallographic study

Metal ion complexing properties of the highly preorganized tetradentate ligand PDALC (2,9-bis(hydroxymethyl)-1,10-phenanthroline) are presented. The structure of [Gd(PDALC)(NO₃)₃]·H₂O (1) is reported: triclinic, , a = 7.545(12), b = 10.811(17), c = 11.909(18) Å, α = 97.71(2)°, β = 91.56(2)°, γ = 109.06(2)°, V = 907(2) Å³, Z = 2, R = 0.0354. The Gd is 10-coordinate, with the coordination sphere comprising the four donor atoms of the PDALC plus the six O-donors of three chelated nitrates. Comparison with structures in the literature suggests that the Gd-L (L = ligand) bond lengths, particularly those to the alcoholic O-donors of PDALC, are a little short. It was suggested that the short Gd-L bond lengths in 1 were due to the efficiency of packing of the nitrates around the Gd, with the short ‘bite’ distances of the nitrate ligand. Formation constants (log K₁) were measured spectroscopically in 0.1 M NaClO₄ at 25 °C by monitoring the variation of the π-π∗ transitions of 2 × 10⁻⁵ M PDALC in the range 200-350 nm as a function of pH, in the presence of 1:1 concentrations of the lanthanide(III) (Ln(III)) metal ion. The measured log K₁ values varied from 5.34 (La(III)) to 6.40 (Lu(III), which is an unusually small variation across the series of Ln(III) ions. Values of log K₁ with PDALC were also measured for Y(III) (5.85) and Sc(III) (6.02). The small amount of variation in log K₁ for PDALC across the series of Ln(III) ions was rationalised in terms of the effect of neutral oxygen donors on complex stability, which promotes selectivity for larger metal ions such as La(III). It was discussed how the small amount of variation in log K₁ across the Ln(III) series might lead to optimal selectivity for the Am(III) ion relative to the Ln(III) ions as a group.     

Complexes of dibenzylsulfoxide with lanthanide nitrate

A new series of dibenzylsulfoxide (DBSO) compounds of empirical formula [Ln(DBSO)_x(NO₃)₃] are reported, where x = 3 for Ln = Pr; x = 2.5 for Ln = Nd, Sm, Eu, Gd, Er and La; and x=2 for Ln = Dy. The compounds were synthesized from a non-aqueous solvent and isolated as dibenzylsulfoxide salts. Infrared spectral data established coordination by the anion groups and also that coordination of DBSO is through the oxygen. Additional information based on the nature of bonding and geometrical structure was obtained from the electronic absorption spectra, X-ray diffraction analysis, molecular conductivities and molecular weight measurements (as well as magnetic susceptibility measurements). All these physical measurements indicate octahedral coordination. The 20% decrease in the metal ion radius across the lanthanide series and the competition between DBSO and nitrate groups for the coordination site affect the number of DBSO molecules bonded to a tripositive lanthanide ion.     

Lanthanide(III) coordination polymers from the exo-coordination of Na: Syntheses, structures, luminescence, and decay dynamics

[Na₂[Ln₂(sal)₄(CF₃SO₃)₂(H₂O)₄](CF₃SO₃)₂]_n Ln = Nd (1) and Eu (2) were synthesized from the reaction of salicylaldehyde, lanthanide(III) triflates, and sodium hydroxide. The compounds are iso-structural and possess a 2-D supramolecular network built up from discrete dinuclear Ln(III) units [Ln₂(sal)₄(CF₃SO₃)₂(H₂O)₄] via exo-coordination of Na(CF₃SO₃). The sal ligands display μ₂-O coordination modes involving both the phenolic and carbonyl oxygen atoms while the triflates function as both μ₂ and μ₃ bridges. Each Ln(III) in the network is eight coordinate and in bicapped trigonal prism coordination geometry. Luminescence from [Na₂[Eu₂(sal)₄(CF₃SO₃)₂(H₂O)₄](CF₃SO₃)₂]_n showed temperature dependent sensitized emission with significant quadrupolar contribution and decay dynamical studies followed single exponential kinetics. Together these results indicate that in the presence of Na⁺ ions, sal, and triflate are useful ligands in the construction of Ln(III) coordination polymers with unusual luminescence and structures.     

Ultramicroporous channel lanthanide coordination polymers of 2,5-pyrazinedicarboxylate

Five lanthanide coordination polymers with composition {[Ln(pzdc)_1.5(H₂O)₃] · 0.5H₂O}_∞, (Ln = Pr, 1; Nd, 2; Sm, 3; Eu, 4; Gd, 5; pzdc = 2,5-pyrazinedicarboxylate), have been synthesized by reacting Ln(NO₃)₃ · 6H₂O with 2,5-pyrazinedicarboxylic acid under hydrothermal condition in the absence of additional base and characterized by elemental analysis, IR spectra and TG analysis, as well as single-crystal X-ray diffraction. They crystallize isostructurally in the triclinic space group P-1 and the cell parameters agree with the ionic radii of the Ln(III) ions. Each trivalent rare earth ion is nine coordinate in an N₂O₇ environment. The ligand 2,5-pyrazinedicarboxylate adopts three coordination modes, through which the lanthanide ions are linked together to form an infinite three dimensional structure. A 1D channel exists along the (1 0 0) direction which accommodates uncoordinated water by hydrogen bonds. Heating of 4 at 120 °C evacuated the uncoordinated water while retaining its single crystallinity with only minor change in cell parameters (crystal 6, [Eu(pzdc)_1.5(H₂O)₃]_∞). This hydrophilic ultramicroporous channel is selective to accommodate water only among common solvents, which has some potential interest for solvent separation.     

A structural study of the hydrated and the dimethylsulfoxide, N,N′-dimethylpropyleneurea, and N,N-dimethylthioformamide solvated iron(II) and iron(III) ions in solution and solid state

The structures of the solvated iron(II) and iron(III) ions have been studied in solution and solid state by extended X-ray absorption fine structure (EXAFS) in three oxygen donor solvents, water, dimethylsulfoxide (Me₂SO), N,N′-dimethylpropyleneurea (DMPU), and one sulfur donor solvent, N,N-dimethylthioformamide (DMTF); these solvents have different coordination and solvation properties. In addition, the structure of hexakis(dimethylsulfoxide)iron(III) perchlorate has been determined crystallographically to support the determination of the corresponding solvate in solution. The hydrated, the dimethylsulfoxide and N,N-dimethylthioformamide solvated iron(II) ions show regular octahedral coordination in both solution and solid state with mean Fe-O, Fe-O, and Fe-S bond distances of 2.10, 2.10, and 2.52 Å, respectively, whereas the N,N′-dimethylpropyleneurea iron(II) solvate is five-coordinated, d(Fe-O) = 2.06 Å. The compounds vary in color from light green (hydrate) to dark orange or red (DMPU). The hydrated iron(III) ion in aqueous solution and the dimethylsulfoxide solvated iron(III) ions in solution and solid state show the expected octahedral coordination, the Fe-O bond distances are 2.00 Å for both, whereas the N,N′-dimethylpropyleneurea iron(III) solvate is found to be five-coordinated with a mean Fe-O bond distance of 1.99 Å. The N,N-dimethylthioformamide solvated iron(III) ion in the solid perchlorate salt is tetrahedrally four-coordinated, the mean Fe-S bond distance is 2.20 Å. Iron(III) is reduced with time to iron(II) in N,N-dimethylthioformamide solution. The compounds vary in color from pale yellow (hydrate) to blackish red (DMPU).     

Synthesis,density functional theory calculations and luminescence of lanthanide complexes with 2,6‐bis[(3‐methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand

A pyridine‐diacylhydrazone Schiff base ligand, L = 2,6‐bis[(3‐methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X‐ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO₃)₂]NO₃.xH₂O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra‐red (FT‐IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO₃)₂]⁺ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT‐IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.     

Syntheses, structures, and spectroscopy of mono- and polynuclear lanthanide complexes containing 4-acyl-pyrazolones and diphosphineoxide

Lanthanide coordination compounds are important due to their unique luminescence and magnetic properties. Direct synthesis of oligo- and polymeric Ln complexes with a predicted structure is hampered due to high coordination numbers and unstable coordination polyhedra. A «building blocks» strategy for the synthesis of Ln(Q)₃L polymers (Ln = Eu, Tb or Gd; HQ = 1-phenyl-3-methyl-4-RC(O)pyrazol-5-one in general, in detail HQ_S, R = thienyl; HQ_CP: R = cyclopentyl; L = bis(diphenylphosphine)methane dioxide dppMO₂, bis(diphenylphosphine)ethane dioxide dppEO₂, and bis(diphenylphosphine)butane dioxide dppBO₂) has been used: {Ln(Q)₃} mononuclear fragments have been linked by dppXO₂ bridges when X = E or B, while monomeric molecular derivatives have been isolated with dppMO₂. Eighteen new complexes were prepared, 12 of them showing a polymeric nature and 6 being monomers. Three compounds have been structurally characterized, further confirming the hypothesized connectivity where metal centers have been found to exist in LnO₈ square antiprismatic environments. Luminescence properties have been also investigated.     

Synthesis,spectroscopic, and antibacterial activity of tetraazamacrocyclic complexes of trivalent chromium,manganese, and iron

A new series of macrocyclic complexes of type [M(TML)X]X₂, where M = Cr(III), Mn(III), or Fe(III), TML is tetradentate macrocyclic ligand, and X = Cl^?, NO₃^?, CH₃COO^? for Cr(III), Fe(III) and X = CH₃COO^? for Mn (III), has been synthesized by condensation of benzil and succinyldihydrazide in the presence of metal salt. The complexes have been so formulated due to the 1:2 electrolytic nature of these complexes as shown by conductivity measurements. The complexes have been characterized with the help of various physicochemical techniques such as elemental analysis, molar conductance, electronic and infrared spectral studies, and magnetic susceptibility. On the basis of these studies, a five-coordinate distorted square pyramidal geometry, in which two nitrogens and two carbonyl oxygen atoms are suitably placed for coordination toward the metal ion, has been proposed for all the complexes. The complexes have been tested for their in vitro antibacterial activity. Some of the complexes show remarkable antibacterial activities against some selected bacterial strains. The minimum inhibitory concentrations shown by these complexes have been compared with those shown by some standard antibiotics such as linezolid and cefaclor.     

Synthesis,properties and structure of hexaaquo-tris(N,N-dimethylformamide)-lanthanide trifluoromethanesulfonates

The compounds of general formula [Ln(DMF)₃- (H₂O)₆](CF₃SO₃)₃ (Ln = LaEu, Tb, Dy) were synthesized and characterized by microanalysis, conductance measurements, IR absorption (Nd³⁺) and emission (Eu³⁺) spectra. The crystal structure of the neodymium compound was determined by X-ray diffraction techniques. The compound crystallizes in the triclinic system, space group P1, a = 8.589(4), b = 11.222(2), c = 12.271(2) Å, α = 56.83(2), β = 62.13(2), γ = 75.14(2)°, V = 875.2 ų, M = 918.4, Z = 1, D_c = 1.73 g cm⁻³, λ(Mo Kα) = 0.71073 Å, μ = 1.65 mm⁻¹, F(000) = 456, R = 0.056, R_w = 0.057, for 2979 independent reflections with I > 3σ(I). Nd³⁺ is coordinated to the oxygen atoms of six independent water molecules at a mean distance NdO = 2.52(1) Å, and to the oxygen atoms of three independent DMF groups at a mean distance NdO = 2.40(2) Å. The coordination polyhedron is a tricapped trigonal prism of point symmetry C_3v.     

Phosphodiesterolytic activity of lanthanide (III) complexes with α-amino acids

Kinetics of the hydrolysis of BNPP (bis(4-nitrophenyl)phosphate) mediated by lanthanide - samarium (III) and ytterbium (III) - alone and in the presence of various alfa amino acids has been systematically studied at 37.0 °C and I = 0.15 M in NaClO₄, in the pH interval of 7-9. The rate of BNPP cleavage is sensitive to metal ion concentration, pH, and ligand to metal molar ratio. Hydrolysis follows Michaelis-Menten-type saturation kinetics. For both metals, high pH values markedly increase the observed activity. Besides, potentiometric titrations of all these systems under identical conditions allowed us to identify the active coordination compounds towards hydrolysis. The results show that complexes with phosphodiesterolytic activity are monomeric cationic species such as [Ln(aa)₃(OH)]²⁺ or [Ln(aa)₂(OH)₂]⁺. Since phosphodiesterolytic activity is evident above pH 7 and it is increased with increasing pH, hydrolytic reactions of the metals are competitive processes that could lead to their precipitation as Ln(OH)₃(s). In this sense, ligand excess (for example, ligand to metal molar ratio equal to 30) was employed. Furthermore, due to its more extended hydrolysis, ytterbium shows, in general, less activity than samarium under the studied conditions. In general, a good phosphodiesterolytic activity is observed for these complexes under similar conditions to the physiological ones. Amino acids could be easily derivatized without changing their coordinating ability, leading to lanthanide complexes possibly capable of efficiently hydrolyzing the phosphodiester linkages of nucleic acids.     

Electronic structures of collagen model polymers: (Gly-Pro)n, (Gly-Hyp)n, (Ala-Pro)n, (Ala-Hyp)n, (Gly-Pro-Gly)n, (Gly-Hyp-Gly)n, (Gly-Pro-Pro)n, and (Gly-Pro-Hyp)n

In order to investigate the relationship existing between the electronic structures of collagen and its biochemical functions in vivo, the semiempirical CNDO/2 SCF MO calculations were carried out on several model polymers of collagen, (Gly-Pro)_n, (Gly-Hyp)_n, (Ala-Pro)_n, (Ala-Hyp)_n, (Gly-Pro-Gly)_n, (Gly-Hyp-Gly)_n, (Gly-Pro-Pro)_n and (Gly-Pro-Hyp)_n. Geometries of the skeleton of these polymers were assumed to be the same as those of poly(l-proline) I (cis) and II (trans) and the calculations were performed only on infinite polymers in a single chain. The results show that the cis form is always more stable than the trans form for all the polymers treated. This energy difference between the cis and trans forms depends, for example, on the kind of amino acid residue, Gly or Ala, but this could not be seen in the Pro or Hyp residue. The flexibility or mobility of the collagen structure was explained using the energy difference between the cis and trans forms of the polymers, i.e. the cis-trans conversion of the collagen was discussed in connection with the energy difference. The reason why the collagen has the constitution of (Gly-Pro-Hyp)_n is briefly discussed.     

Formation and phosphodiesterolytic activity of lanthanide(III) N,N-bis(2-hydroxyethyl)glycine hydroxo complexes

Potentiometric titrations of N,N-bis(2-hydroxyethyl)glycine (bicine) in the presence of Ln(III) cations (Ln=La, Pr, Nd and Eu) in the pH range extended to ca. 9.5 reveal formation of two types of binuclear hydroxo complexes Ln₂(bic)₂(OH)₄ and Ln₂(bic)(OH)₄ ⁺ (bicH=bicine) in addition to previously reported mononuclear mono- and bis-complexes Ln(bic)²⁺ and Ln(bic)₂ ⁺, which predominate at pH below 8. ¹H NMR titrations of La(III)-bicine mixtures in D₂O show that the complex formation with bicine is slow in the NMR time scale and confirm formation of hydroxide rather than alkoxide complexes in basic solutions. Formation of a different type of hydroxide species under conditions of an excess of metal over ligand is confirmed by studying the absorption spectra of the Nd(III)-bicine system in the hypersensitive region. The binuclear hydroxide complexes are predominant species at pH above 9 and their stabilities increase in the order La < Pr ≈ Nd < Eu. They show fairly high catalytic activity in the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) at room temperature. Comparison of concentration and pH-dependences of the reaction rates with the species distribution diagrams shows that the catalytic hydrolysis of BNPP proceeds via a Michaelis-Menten type mechanism, which involves the Ln₂(bic)(OH)₄ ⁺ complex as the reactive species. The values of the catalytic rate constants and the Michaelis constants are in the range 0.002-0.004 s⁻¹ and 0.35-1.5 mM, respectively, for all lanthanides studied. The half-life for the hydrolysis of BNPP is reduced from 2000 years to ca. 10 min at 25 °C and pH 9.2 in the presence of 5 mM La(III) and 2.5 mM bicine.     

Lanthanide(III) solvation: N,N-dimethylformamide as a unidentate O-donor

Structure determinations for the lanthanide (Ln) complexes [(CH₃)₂NH₂][Gd(dmf)₈](ClO₄)₄, [Tb(dmf)₈](ClO₄)₃ and [Ho(dmf)₇(OH₂)](ClO₄)₃ (dmf=N,N-dimethylformamide) show all three to contain an LnO₈ coordination unit of essentially square-antiprismatic geometry. The geometry of the inner coordination sphere appears to be little perturbed by quite major differences in the lattice environment of the cations. Attractive interactions between coordinated dmf molecules may be one contributor to the stability of the primary coordination sphere.     

Titanium dioxide nanomaterial doped with trivalent lanthanide ions of Tb, Eu and Sm: Preparation, characterization and potential applications

Mesoporous Ln(III)-TiO₂ (Ln = Tb, Eu, Sm) nanomaterials composites have been successfully synthesized by using sol-gel technique.XRD pattern, FT-IR, Raman spectra, and SEM were used to characterize the Ln(III)-TiO₂ nanomaterials. The prepared lanthanide doped TiO₂ nanomaterials have anatase phase and exhibit Ti-O-Ln bond. The absorption spectra of all prepared samples reflect the increasing photoresponse of doped samples to visible light over pure TiO₂. Surface area is remarkably increased due to lanthanide ion-doping.Two newly prepared Ln(III)-TiO₂ (Ln = Eu, Sm) luminescent nanomaterials exhibit enhanced pure red or orange light emission due to energy transfer from host TiO₂ to guest Eu(III) or Sm(III), respectively.In addition, the commercially available textile dye Remazol Red RB-133 degradation was used as a probe reaction to determine the efficiency of the Ln(III)-TiO₂ photocatalysts. The Ln(III) doping brought about remarkable improvement in the photoactivity over pure TiO₂.     

Electrochemical and Thermodynamic Properties of Ln(III) (Ln?=?Eu,Sm, Dy,Nd) in 1-Butyl-3-Methylimidazolium Bromide Ionic Liquid

The electrochemical behavior and thermodynamic properties of Ln(III) (Ln = Eu, Sm, Dy, Nd) were studied in 1-butyl-3-methylimidazolium bromide ionic liquid (BmimBr) at a glassy carbon (GC) electrode in the range of 293–338 K. The electrode reaction of Eu(III) was found to be quasi-reversible by the cyclic voltammetry, the reactions of the other three lanthanide ions were regarded as irreversible systems. An increase of the current intensity was obtained with the temperature increase. At 293 K, the cathodic peak potentials of −0.893 V (Eu(III)), −0.596 V (Sm(III)), −0.637 V (Dy(III)) and −0.641 V (Nd(III)) were found, respectively, to be assigned to the reduction of Ln(III) to Ln(II). The diffusion coefficients (D _o), the transfer coefficients (α) of Ln(III) (Ln = Eu, Sm, Dy, Nd) and the charge transfer rate constants (k _s) of Eu(III) were estimated. The apparent standard potential (E ⁰*) and the thermodynamic properties of the reduction of Eu(III) to Eu(II) were also investigated.     

Hydrothermal synthesis and crystal structures of two lanthanide coordination polymers with novel tetradentate-coordinated perchlorates

Two new 3D lanthanide coordination polymers {[Ln(C₂O₄)(ClO₄)(H₂O)] · Cl}_n [Ln = Pr (1) and Nd (2)] have been synthesized by hydrothermal reactions and characterized by elemental analysis, X-ray single-crystal analyses, IR and Raman spectroscopy. X-ray crystal structure analyses reveal that compounds 1 and 2 are isostructural and crystallized in the space group P2₁/c. A 1D zigzag chains formed by oxalate ligands in μ₂-mode to bridge Ln(III) atoms present in the two complexes and the adjacent zigzag chains were further connected by μ₃-η¹:η¹:η¹:η¹ fashion of into a 3D framework with ordered 1D channels, in which uncoordinated Cl⁻ anions are located as counterions. In addition, the IR and Raman spectrum further confirm the presence of tetradentate-coordinated perchlorates.     

Structures, redox behavior, antibacterial activity and correlation with electronic structure of the complexes of nickel triad with 3-(2-(alkylthio)phenylazo)-2,4-pentanedione

3-(2-(Alkylthio)phenylazo)-2,4-pentanedione (HL), an O, N, S donor ligand, is used for the synthesis of Ni(II), Pd(II) and Pt(II) complexes. The spectroscopic (IR, UV-Vis, and NMR) data determine the structure. The single crystal X-ray diffraction measurement of [Ni(L)₂] and [Pt(L)Cl] has confirmed the structures. Coulometric oxidation of [Ni(L)₂] and EPR spectra thereof show formation of Ni(III) state. DFT computation has calculated the electronic configuration and has explained the spectral and redox properties of the complexes. The compounds are screened for their in vitro anti-bacterial activity using Gram-positive and Gram-negative bacteria (Bacillus subtilis UC564, Escherichia coli TG1, Staphylococcus aureus Bang25, Pseudomonas aeruginosa C/1/7, Salmonella typhi NCTC62, Salmonella paratyphi NCTC A2, Shigella dysenteriae 8NCTC599/52, Streptococcus faecalis S2, Vibrio cholerae DN7 and Mricococcus luteusAGD1). The minimum inhibitory concentration is determined for the compounds. The effect of the structure of the investigated compounds on the antibacterial activity is discussed.