Cyclometallated ruthenium(III) complexes: Synthesis,structure and properties

Reactions of Schiff bases (H₂apahR) derived from acetophenone and acid hydrazides, triethylamine and [Ru(PPh₃)₃Cl₂] (1:2:1 mole ratio) in methanol provide cyclometallated ruthenium(III) complexes of formula trans-[Ru(apahR)(PPh₃)₂Cl] in 74–81% yields. The complexes have been characterized by elemental analysis, magnetic susceptibility, spectroscopic (infrared, electronic and EPR) and electrochemical measurements. X-ray crystal structures of two representative complexes have been determined. In each complex, the metal centre is in distorted octahedral CNOClP₂ coordination sphere assembled by the C,N,O-donor meridionally spanning apahR^2?, the chloride and the two mutually trans-oriented PPh₃ molecules. All the complexes are one-electron paramagnetic (μ_eff. = 1.85–1.98 μ_B) and display rhombic EPR spectra in frozen (120 K) dichloromethane-toluene (1:1) solution. Electronic spectra of the complexes display several absorptions within 470–270 nm due to ligand-to-metal charge transfer and ligand centred transitions. The complexes are redox active and display a Ru(III) → Ru(II) reduction and a Ru(III) → Ru(IV) oxidation in the potential ranges ?0.66 to ?0.70 V and 0.75 to 0.80 V (vs. Ag/AgCl), respectively.     

Synthesis,spectroscopic studies,thermal analyses,biological activity of tridentate-coordinated transition-metal complexes [M(L)X2] and crystal structure of [ZnBr2(2,6-bis(tert-butylthiomethyl)pyridine)]

A new terdentate acyclic pincer ligand, 2,6-bis(tert-butylthiomethyl)pyridine (tbtmp), was synthesized and reacted with several complexes of iron, zinc, nickel, cobalt, and copper. The ligand and its coordination compounds were characterized using elemental analysis, infrared, ¹H- and ¹³C-NMR-spectroscopy, thermal analyses, plus—for the Zn complex—single-crystal X-ray diffractometry. The structure of [Zn(L)Br₂] was solved in the tetragonal crystal system, chiral space groups P4₁2₁2 and P4₃2₁2 (No. 92 and No. 96, a = 947.2(1) pm, c = 2265.2(5) pm), revealing five-fold coordination of the metal atoms. According to spectroscopy, all complexes share the same coordination environment around the metal atoms, consisting of two halide anions and a sulfur-methylene-pyridine-methylene-sulfur entity; tbtmp acts as a tridentate ligand with the pyridine N atom and both tert-butylthio S atoms coordinating to the metal ions (NS2). The analysis results indicate that the metal ions are coordinated as distorted pseudo-bipyramids, LMX₂, with the chelate ligand meridionally arranged. One of the complexes contains ethanol as an additional ligand, resulting in a pseudo-octahedral coordination sphere [Ni(L)Cl₂EtOH]. The latter was obtained in the form of green crystals, which turn into a red powder with loss of the ethanol molecule. Fe (III), Co(II), Ni(II) and Cu(II) metal complexes [M(L)Cl₂] were screened for their antibacterial activity against B. subtilis G(+) and Escherichia coli G(−) bacteria, and fungus (Candida albicans and Aspergillus flavus).     

Synthesis and in vitro biology of Co(II), Ni(II), Cu(II) and Zinc(II) complexes of functionalized beta-diketone bearing energy buried potential antibacterial and antiviral O,O pharmacophore sites

The clinically active functionalized β-diketones 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione (L₁)–(L₂) have been synthesized from Baker–Venkataraman transformation of 2,4-diaroyloxyacetophenones. Their transition metal complexes (1)–(8) have been prepared and characterized by physical, spectral and analytical data. The functionalized beta-diketone potentially acts as bidentate ligand and co-ordinate with the transition metal atom through beta-diketo system. The complexes have general formula [ML₂] where M = Co(II), Ni(II), Cu(II), Zinc(II) and L = ligand. The 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione and their transition metal complexes have been screened for in vitro antibacterial, antifungal and antioxidant bioassay. The biological activity data show that the transition metal complexes are more potent antibacterial, antifungal and antioxidant agents than the parent functionalized beta-diketone against different bacterial and fungal species. This constitutes a new group of compounds that can be used as potential metal derived drugs. Ultimately, here we can prompt about the use of metals for the drugs. The metal complexes were also studied for their thermogravimetric analyses.     

2,2′-Oxydiacetato-bridged complexes containing Sm(III) and bivalent cations. Synthesis,structure, magnetic properties and chemical speciation

Heterometallic compounds containing Sm(III), bivalent cations M (M = Cu, Ni, Co, Mn, Ca, Mg), and 2′,2′-oxydiacetate (oda) as connecting ligand have been prepared and characterized. The complexes can be formulated as [Sm₂M₃(oda)₆] · xH₂O. The structure of [Sm₂Cu₃(oda)₆(H₂O)₆] shows the presence of the Sm(III) coordinated by six carboxy and three ether oxygen atoms, and the Cu(II) cation bonded to four carboxy oxygens and two molecules of water. An open 3D framework is observed, containing large hexagonal channels. At room temperature, the polynuclear complexes behave as built by magnetically isolated paramagnetic ions, but at low temperatures, very weak antiferromagnetic interactions M – M are predominant. The chemical systems were also investigated in solution (25.0 °C, I = 0.5 M Me₄NCl) by potentiometry. The same kind of polynuclear species have been found.     

Thermal investigation and infrared evolved gas analysis of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid

The characterisation of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid of the formula Ln₂pdc₃·nH₂O where Ln denotes lanthanides from La to Gd, pdc = C₇H₅NO₄²⁻; n = 6 for Ce(III), n = 7 for Pr(III) and Sm(III), n = 8 for La and n = 13 for Nd(III), Eu(III) and Gd(III) was performed by the thermal analysis TG-DTA and the simultaneous infrared evolved gas analysis TG-FTIR. Heating of the crystalline complexes resulted in the dehydration process at first. Next, dehydrated compounds decompose releasing of CO₂, CO, CH₄ and hydrocarbons. Free pyridine molecules were detected only in the gaseous products of lanthanum(III) complex decomposition.     

Synthesis and spectroscopic characterization of new tetradentate Schiff base and its coordination compounds of NOON donor atoms and their antibacterial and antifungal activity

New Schiff base (H₂L) ligand is prepared via condensation of o-phthaldehyde and 2-aminobenzoic acid in 1:2 ratio. Metal complexes are prepared and characterized using elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, ¹H NMR, ESR and thermal analysis (TGA). From the elemental analyses data, the complexes were proposed to have the general formulae [MCl(L)(H₂O)]·2H₂O (where M = Cr(III) and Fe(III)); [M(L)]·yH₂O (where M = Mn(II), Ni(II), Cu(II) and Zn(II), y = 1–2) and [M(L)(H₂O)_n]·yH₂O (where M = Co(II) (n = y = 2), Co(II) (n = y = 1), Ni(II) (n = 2, y = 1). The molar conductance data reveal that all the metal chelates were non-electrolytes. IR spectra show that H₂L is coordinated to the metal ions in a bi-negative tetradentate manner with NOON donor sites of the azomethine-N and carboxylate-O. The ¹H NMR spectral data indicate that the two carboxylate protons are also displaced during complexation. From the magnetic and solid reflectance spectra, it was found that the geometrical structure of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II)), square planar (Cu(II)), trigonal bipyramidal (Co(II)) and tetrahedral (Mn(II), Ni(II) and Zn(II)). The thermal behaviour of these chelates showed that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the ligand molecule in the subsequent steps. The biological activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species.     

An oxazoline derivatized Pybox ligand for Eu(III) and Tb(III) sensitization

A new Tb(III) dimer with an oxazoline-derivatized pyridine ligand, dimethyl-2,2′-(pyridine-2,6-diyl)bis(4,5-dihydrooxazole-4-carboxylate), has been isolated. This complex is highly luminescent and crystallizes in the triclinic P-1 space group with parameters a = 9.6167(2) Å, b = 11.6786(2) Å, c = 12.7548(3) Å, α = 70.026(1)°, β = 83.219(1)°, γ = 81.973(1)° and V = 1329.31(51)ų. Solution speciation studies showed the formation of monomeric species with 1:1 and 2:1 ligand-to-metal ion stoichiometries with log β₁₁ = 3.66 ± 0.41 and log β₂₁ = 6.16 ± 0.37 for Eu(III) and log β₁₁ = 3.56 ± 0.41 and log β₂₁ = 6.21 ± 0.38 for Tb(III). The quantum yields of emission Φ and luminescence lifetimes τ of solutions with 2:1 stoichiometry were 26.4 ± 0.5% and 1.47 ± 0.06 ms for Eu(III) and 41.0 ± 1.3% and 1.87 ± 0.06 ms for Tb(III).     

Synthesis,structural investigations and antimicrobial studies of hydrazone based ternary complexes with Cr(III), Fe(III) and La(III) ions

A novel series of three trivalent mononuclear ternary complexes of the type, [ML₁L₂] [M = Cr(III), Fe(III) and La(III), HL₁ = 2-((2-(2,4-dinitrophenyl)hydrazone)methyl)phenol, HL₂ = 2-aminophenol] was investigated by various physio-chemical studies. To obtain additional information inside the structure, density functional theory calculation was also carried out. The synthesized complexes showed remarkable antimicrobial activity when tested against A. niger, A. flavus, R. stolonifer, C. albicans, E. coli and Klebsiella sp. microbes. Furthermore, the molecular docking analysis was also carried out to analyze the interactions in protein–ligand complexes. Moreover, the quantitative structure–activity relationship was also investigated to study the biological activity of the ligand.     

Synthesis,characterization and antibacterial activity of some new triphenyltin(IV) sulfanylcarboxylates: Crystal structure of [(SnPh3)2(p-mpspa)], [(SnPh3)2(cpa)] and [(SnPh3)2(tspa)(DMSO)]

Five new triphenyltin(IV) sulfanylcarboxylates of the general formula [(SnPh₃)₂L] (L = pspa, tspa, fspa, p-mpspa or cpa, where p = 3-(2-phenyl)-, t = 3-(2-thienyl)-, f = 3-(2-furyl)-, p-mp = 3-(4-methoxyphenyl)-, spa = 2-sulfanylpropenoato and cpa = 2-cyclopentilyden-2-sulfanylacetate) have been synthesized by reacting triphenyltin(IV) hydroxide with the corresponding acid in ethanol/acetone. The complexes have been characterized by elemental analysis and mass spectrometry and by vibrational and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies. In the case of [(SnPh₃)₂(p-mpspa)] and [(SnPh₃)₂(cpa)], X-ray structural studies showed that in both compounds each Sn atom is coordinated to three phenyl C atoms and to one S or O atom of the bridge ligand L. All five complexes are active against strains of Staphylococcus aureus, but are inactive against Escherichia coli and Pseudomonas aeruginosa. From a solution of [(SnPh₃)₂(tspa)] in DMSO-d₆ the new complex [(SnPh₃)₂(tspa)(DMSO)] was isolated. The single-crystal X-ray diffractometric study of this complex is also reported, showing that both Sn atoms are bridged by the tspa ligand, whereas the molecule of DMSO is coordinated to one of the tin atoms via the oxygen atom.     

Thermodynamic study of Eu(III) complexation by pyridine monocarboxylates

The thermodynamic parameters (log K, ΔG, ΔH and ΔS) of complexation of Eu(III), a chemical analogue of trivalent actinides, with pyridine monocarboxylates, namely, picolinic acid (pyridine-2-carboxylic acid), nicotinic acid (pyridine-3-carboxylic acid), isonicotinic acid (pyridine-4-carboxylic acid) have been studied at 1.0 M ionic strength adjusted by NaClO₄ and 298 K by potentiometry, fluorescence spectroscopy and calorimetry. The potentiometric results revealed formation of four complexes, ML_i (i = 1–4) in case of picolinate whereas only ML complexes in case of nicotinate and isonicotinate. The log K_ML for Eu(III) picolinate complex is higher than that for complexes of Eu(III) with the other two acids. The complexation reaction between Eu(III) and picolinate was found to be exothermic due to chelate formation via pyridyl nitrogen. In case of complexation of Eu(III) with nicotinate and isonicotinate, the enthalpy changes are similar as in the case of simple mono carboxylates and are positive. Life time measurements by time resolved fluorescence spectroscopy, for the decay of ⁵D₀ state of Eu(III) also indicated the formation of ML₄ with picolinate and formation of ML only with the other two acids. The experimental observations on the stability and binding mode of the complexes are corroborated by theoretical calculations using the TURBOMOLE software. The detail analysis of calculated charge values of the free ligands and the complexes indicates that charge polarization is more in the isonicotinate than in nicotinate upon complexation.     

Lanthanide complexes derived from hexadentate macrocyclic ligand: Synthesis,spectroscopic and thermal investigation

The lanthanide complexes derived from (3,5,13,15-tetramethyl 2,6,12,16,21-22-hexaazatricyclo[15.3.I^1-17I^7-11]cosa-1(21),2,5,7,9,11(22),12,15,17,19-decane) were synthesized. The complexes were found to have general composition [Ln(L)X₂·H₂O]X, where Ln = La³⁺, Ce³⁺, Nd³⁺, Sm³⁺ and Eu³⁺ and X = NO₃^? and Cl^?. The ligand was characterized by elemental analyses, IR, Mass, and ¹H NMR spectral studies. All the complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral techniques and thermal studies. The ligand acts as a hexadentate and coordinates through four nitrogen atoms of azomethine groups and two nitrogen of pyridine ring. The lanthanum complexes are diamagnetic while the other Ln(III) complexes are paramagnetic. The spectral parameters i.e. nephelauxetic ratio (β), covalency factor (b^1/2), Sinha parameter (δ%) and covalency angular overlap parameter (η) have been calculated from absorption spectra of Nd(III) and Sm(III) complexes. These parameters suggest the metal–ligand covalent bonding. In the present study, the complexes were found to have coordination number nine.     

Metal complexes of gliclazide: Preparation,spectroscopic and thermal characterization. Biological potential study of sulphonylurea gliclazide on the house fly,Musca domestica (Diptera – Muscidae)

Metal complexes of gliclazide (GLZ; HL) drug are prepared and characterized based on elemental analyses, IR, diffused reflectance, magnetic moment, molar conductance and thermal analyses (TG and DTG) technique. From the elemental analyses data, the complexes are proposed to have the general formulae [M(HL)Cl₃(H₂O)]·3H₂O (M = Cr(III) and Fe(III)), [M(HL)Cl₂(H₂O)₂]·yH₂O (M = Co(III), Ni(II) and Cu(II), y = 0–2) and [M(HL)Cl₂]·yH₂O (M = Mn(II) and Zn(II), y = 0–1). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that GLZ is coordinated to the metal ions in a neutral bidentate manner with ON donor sites of the amide-O and sulphonamide-OH. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II) and Cu(II)) and tetrahedral (Mn(II) and Zn(II)). The thermal behaviour of these chelates is studied using thermogravimetric analysis (TG and DTG) techniques. The results obtained show that the hydrated complexes lose water molecules of hydration followed immediately by decomposition of the anions and ligand molecules in the successive unseparate steps. The activation thermodynamic parameters are calculated using Coats–Redfern method. The GLZ drug, in comparison to its metal complexes also is screened for their biological activity against house fly, Musca domestica (Diptera – Muscidae). Dose of 5 μg/insect of gliclazide is typically applied against 3 days-old larval instar of M. domestica. Survival of pupal and adult stages has been affected by the complexes of gliclazide more than larval instars. Morphogenic abnormalities of larvae, pupae and adults are studied. On the other hand, pupation and adult emergence program is deteriorated by the effect of different chemicals.     

Synthesis,characterization and biological properties of Co(II), Ni(II), Cu(II) and Zn(II) complexes with an SNO functionalized ligand

Some new metal(II) complexes, ML₂[M = Co, Ni, Cu and Zn], of 2-acetylthiophene benzoylhydrazone ligand (HL) containing a trifunctional SNO-donor system have been synthesized and characterized on the basis of physicochemical data by elemental analysis, magnetic moment, molar conductance, thermogravimetric and spectroscopic (electronic, IR, ¹H NMR and ¹³C NMR) data. The ligand functions as monobasic SNO tridentates where the deprotonated enolic form is preferred in the coordination producing distorted octahedral complexes.     

Synthesis,spectral characterization,theoretical, antimicrobial,DNA interaction and in vitro anticancer studies of Cu(II) and Zn(II) complexes with pyrimidine-morpholine based Schiff base ligand

Novel Cu(II) (1) and Zn(II) (2) complexes with 4-(1-(4-morpholinophenyl)ethylideneamino)pyrimidine-5-carbonitrile) (L) have been synthesized and characterized by various spectroscopic and analytical techniques. DFT (density functional theory) studies result confirms that, LMCT mechanism have been done between L and M(II) ions. The antimicrobial studies indicate that the ligand L and complexes 1 & 2 exhibit higher activity against the E. coli bacteria and C. albicans fungi. The groove binding mode of ligand L and complexes 1 & 2 with CT-DNA have been confirmed by electronic absorption, competitive binding, viscometric and cyclic voltammetric studies. The electronic absorption titration of ligand L and complexes 1 & 2 with DNA have been carried out in different buffer solutions (pH 4.0, 7.0 & 10.0). The K_b values of ligand L and complexes 1 & 2 are higher in acidic buffer at pH 4.0 (K_b = 2.42 × 10⁵, L; 2.8 × 10⁵, 1; 2.65 × 10⁵, 2) and the results revealed that, the interaction of synthesized compounds with DNA were higher in the acidic medium than basic and neutral medium. Furthermore, CT-DNA cleavage studies of ligand L and complexes 1 & 2 have been studied. The in vitro anticancer activities results show that complexes 1 & 2 have moderate cytotoxicity against cancer cell lines and low toxicity on normal cell line than ligand L.     

Synthesis,structure and solid state NMR analysis of a new templated titanium(III/IV) fluorophosphate

The title compound MIL-131 (MIL stands for Material from Institut Lavoisier) was prepared hydrothermally (4 days, 473 K, autogenous pressure) in the presence of an organic base (N((CH₂)₂NH₂)₃). The structure of MIL-131 or Ti^IIITi^IV(OH)F₄(HPO₄)·(PO₄)·(N((CH₂)₂NH₃)₃) has been determined ab initio from X-Ray synchrotron powder diffraction data using simulated annealing methods and was refined in the triclinic space group P-1 (no. 2). MIL-131 exhibits a one-dimensional structure built up from inorganic chains of corner sharing TiO₅(OH) titanium(III) octahedra and PO₄ and HPO₄ phosphate tetrahedra, related to TiO₂F₄ titanium octahedra. Protonated triamine cations are located between the inorganic motifs, and interact strongly with the mineral network through hydrogen bondings both with terminal fluorine atoms and hydroxo or oxo groups. Multinuclear solid state NMR has allowed a clear attribution of the protons, fluoride, and phosphate groups environment within the framework of MIL-131. The large values of chemical shift anisotropy together with the absence of any ¹³C NMR response confirmed the presence of paramagnetic titanium(III) species deduced from the crystal structure. Finally, 2D MAS ¹H-³¹P CP-HETCOR NMR correlation experiment gives some insight on the nature of the intra-framework hydrogen bonding.Crystal data for MIL-131: a = 14.109(1) Å, b = 8.462(3) Å, c = 7.179(1) Å, α = 93.772(1)°, β = 96.566(2)°, γ = 98.004(1)°, V = 840.36(2) ų, z = 2.     

Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT = 298.15 K andp = 0.1 MPa

The apparent molar heat capacities C_{p, φ} ^∘ and apparent molar volumes V_φ ^∘ of Y₂(SO₄)₃(aq), La₂(SO₄)₃(aq), Pr₂(SO₄)₃(aq), Nd₂(SO₄)₃(aq), Eu₂(SO₄)₃(aq), Dy₂(SO₄)₃(aq), Ho₂(SO₄)₃(aq), and Lu₂(SO₄)₃(aq) were measured at T =  298.15 K and p =  0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibrating-tube densimeter, respectively. These measurements extend from lower molalities of m =  (0.005 to 0.018) mol ·kg ^− 1to m =  (0.025 to 0.434) mol ·kg ^− 1, where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that V_φ ^∘ {RSO₄ ⁺ , aq, 298.15K}  =  − (6  ±  4)cm³· mol ^− 1and V_φ ^∘ {R(SO₄)₂ ⁻ , aq, 298.15K}  =  (35  ±  3)cm³· mol ^− 1, with no significant variation with rare-earth. In contrast, values of C_{p, φ} ^∘ { RSO₄ ⁺ , aq, 298.15K } generally increase with the atomic number of the rare-earth, whereas C_{p, φ} ^∘ { R(SO₄)₂ ⁻ , aq, 298.15K } shows a less regular trend, although its values are always positive and tend to be larger for the heavier than for the light rare earths.     

Novel Fe (III) heterochelates: Synthesis,structural features and fluorescence studies

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H₂SB_n) and their Fe (III) heterochelates of the type [Fe(SB_n)(L)(H₂O)]·mH₂O [H₂SB_n = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH₃, m = 4 (H₂SB₁); –C₆H₅, m = 2 (H₂SB₂); –CH₂–CH₃, m = 3 (H₂SB₃); –CH₂–CH₂–CH₃, m = 1.5 (H₂SB₄); –CH₂–C₆H₅, m = 1.5 (H₂SB₅) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.     

Thermodynamic study of the sublimation of crystalline tris(1,1,1-trifluoro-2,4-pentanedionate)ruthenium(III) and tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)ruthenium(III)

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of two crystalline ruthenium complexes: tris(1,1,1-trifluoro-2,4-pentanedionate)ruthenium(III) {Ru(tfacac)₃}, between T =  350.20 K and T =  369.17 K and tris(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)ruthenium(III) {Ru(hfacac)₃} between T =  299.15 K and T =  313.14 K. From the temperature dependence of the vapour pressure of the crystalline compounds, the standard molar enthalpies of sublimation were derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. By using an estimated value for the heat capacity differences between the gas and the crystal phases the standard, p^o =  10⁵Pa, molar enthalpies, entropies, and Gibbs energies of sublimation at T =  298.15 K, were derived:     

Synthesis,structure and antibacterial activity of manganese(III) complexes of a Schiff base derived from furfurylamine

Two new mononuclear complexes of manganese(III) viz. [MnL₂(LH)₂]ClO₄ (1) and [MnL₂(N₃)]·0.5CH₃OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria.     

Synthesis and magnetic properties of heptadecametallic Fe(III) clusters

Heptadecametallic, all-ferric pieces of molecular magnetite of general formula HL_x[Fe₁₇O₁₆(OH)₁₂(L)₁₂Br₄]Br_3+x (L = β-picoline, isoquinoline, 3,5-lutidine; x = 0, 1) are made by the simple dissolution of FeBr₃ in L. The β-picoline (or equivalent) molecules act simultaneously as solvent, base and capping ligand. The resultant structure consists of a metal–oxygen core containing both octahedral and tetrahedral Fe(III) ions that is the exact analogue of the metal–oxygen positions seen in the magnetite lattice. Antiferromagnetic exchange between the tetrahedral and octahedral Fe(III) ions lead to the stabilization of an S = 35/2 spin ground state.