Complexes of lanthanoid salts with macrocyclic ligands. Part 32. Synthesis and characterization of the complexes between lanthanoid nitrates and a tetraoxadiaza macrocycle

Lanthanoid nitrates react with 1,7,10,16-tetraoxa- 4,13-diaza-N,N′-dimethylcyclooctadecane, Me₂(2,2), to give complexes with two different metal:ligand ratios, 1:1 (Ln = La, Ce, Tb) and 4:3 (Ln = Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho). The complexes were isolated from anhydrous solutions in acetonitrile and characterized by elemental analysis, X-ray diffraction, magnetic susceptibility measurements and vibrational analysis.The La and Ce 1:1 complexes are non-ionic and probably 12-coordinated, with the metal ion bound to the six donor atoms of the ligand and to three bidentate nitrate ions. The 4:3 complexes are ionic; they contain three bis(nitrato) complex cations [Ln(NO₃)₂·Me₂(2,2)]⁺ and one hexakis(nitrato) anion [Ln(NO₃)₆]³⁻. Spectroscopic data, including luminescence spectra, point to the 1:1 Tb-complex as being a 4:3 complex with an additional outer-sphere coordinated molecule of ligand.In solution, the 1:1 complexes remain essentially non-ionic, although some dissociation cannot be ruled out, whereas the 4:3 complexes behave as 2:1 (of even 3:1) electrolytes.     

Antimicrobial study on trivalent lighter rare-earth complexes of 2-pyrazinecarboxylate with hydrazinium cation

The hydrazinium lanthanide metal complexes of 2-pyrazinecarboxylic acid (HpyzCOO) of the formulae (N₂H₅)₂[Ln(pyzCOO)₅]·2H₂O, where Ln=La or Ce and (N₂H₅)₃[Ln(pyzCOO)₄(H₂O)]·2NO₃, where Ln=Pr, Nd, Sm or Dy have been synthesized by the addition of an aqueous solution of the corresponding metal nitrate hydrates to an aqueous mixture of the respective carboxylic acids and hydrazine hydrate. The in vitro antibacterial screening of the free acid and its metal complexes has been carried out against Escherichia coli, Salmonella typhi and Vibrio cholerae. Antifungal activities of all the synthesized compounds were screened for in vitro growth inhibitory activity against Aspergillus fumigatus and Aspergillus niger by using the disc diffusion method. The antimicrobial activities of the prepared metal complexes show more promising activity than the corresponding free acid, its hydrazinium salts, and the standard control antibiotics, Co-trimoxazole and Carbendazim.     

Structure and dynamic behaviour of lanthanide nitrate complexes with bis(diphenylphosphorylmethyl)mesitylene in solutions: The nature of unexpected P NMR spectra

The solution structures of the lanthanide complexes, [Ln(L)(NO₃)₃] and [Ln(L)₂(NO₃)₃], where L = bis(diphenylphosphorylmethyl)mesitylene and Ln = La, Ce, Nd, Er, were investigated by ³¹P NMR and IR spectroscopy, conductivity and sedimentation analysis. Variable-temperature ³¹P{¹H} NMR spectroscopy was used to identify species present in solution and to monitor their interconversions. The results indicate that equilibrium between molecular complexes [Ln(L)_n(NO₃)₃]⁰ and cationic species (as ion pairs [Ln(L)_n(NO₃)₂]⁺ · (NO₃)⁻ and as free ions [Ln(L)_n(NO₃)₂]⁺, throughout n = 1, 2) in solutions can be observed by ³¹P{¹H} NMR spectroscopy due to separate detection of the molecular complexes and cationic species. The chelate coordination of the ligand and nitrate ions is retained in all complex species at ambient temperature except for [Er(L)₂(NO₃)₃]. The crystal structure of [Nd(L)(NO₃)₃(MeCN)]MeCN was determined by X-ray diffraction.     

N,N′-Bis(3-methoxysalicylidene)propane-1,2-diamine mononuclear 4f and heterodinuclear Cu-4f complexes: Synthesis, crystal structure and electrochemical properties

Reactions of H₂L [H₂L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine] and Ln(NO₃)₃ · 6H₂O give rise to two different mononuclear 4f complexes, namely, {[(H₂L)La(NO₃)₃(MeOH)] · H₂O}_n (1) and [(H₂L)Nd(NO₃)₃] (2). Further additions of Cu(Ac)₂ · H₂O to the mononuclear 4f complexes yield expected heterodinuclear Cu-4f complexes [LCu(Me₂CO)Ln(NO₃)₃] (3, Ln = Nd; 4, Ln = Eu; 5, Ln = Dy). Complex 1 is a unique 1D polymeric chain structure, and 2 is one of the few structurally characterized discrete hexadentate salen-type mononuclear 4f complexes. Complexes 3-5 are similar to their analogues. However, they are prepared by a reversed synthetic route in contrast to their isomorphic complexes. Electrochemical behavior of heterodinuclear Cu-4f complexes 3-5 has been examined by cyclic voltammetry in acetonitrile. The redox potential of heterodinuclear Cu-4f complexes 3-5 shows significant anodic shift comparing to that of mononuclear copper complex (LCu). A tendency of anodic shift was observed in a sequence of 3 < 4 < 5. This results from the modulating effect of coordination geometry around Cu(II) ion on redox potential.     

Heterobinuclear Zn‐Ln (Ln = La,Nd, Eu,Gd, Tb,Er and Yb) complexes based on asymmetric Schiff‐base ligand: synthesis,characterization and photophysical properties

With a novel asymmetric Schiff‐base zinc complex ZnL (H₂L = N‐(3‐methoxysalicylidene)‐N′‐(5‐bromo‐3‐methoxysalicylidene)phenylene‐1,2‐diamine), obtained from phenylene‐1,2‐diamine, 3‐methoxysalicylaldehyde and 5‐bromo‐3‐methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn‐Ln complexes [ZnLnL(NO₃)₃(CH₃CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO₃)₃·6H₂O, and characterized by Fourier transform‐infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near‐infrared luminescence of Nd³⁺, Yb³⁺and Er³⁺ with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff‐base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Syntheses of iron(III) aroyl hydrazones containing pyridoxal and salicylaldehyde. The crystal and molecular structure of two iron(III)-pyridoxal isonicotinoyl hydrazone complexes

Iron(III) complexes of three aroyl hydrazones, pyridoxal isonicotinoyl hydrazone (H₂pih), pyridoxal benzoyl hydrazone (H₂pbh), and salicylaldehyde benzoyl hydrazone (H₂sbh), were synthesized and characterized. In aqueous medium at pH 7, [Fe(pih)(Hpih)]·3H₂O is formed. In acidic methanol, a 1:1 ligand-to-metal complex is formed, [FeCl₂(H₂pih)]Cl (1), whereas in aqueous medium at low pH cis-[FeCl₂(H₂pih)(H₂O)]Cl·H₂O (2) is formed. Compounds 1 and 2 are high-spin d⁵ with μ_eff = 5.88 μ_B and 5.93 μ_B (298 K). The crystal structures of 1 and 2 show that H₂pih acts as a tridentate neutral ligand in which the phenolic and hydrazidic protons have shifted to the pyridine nitrogen atoms. The co- ordination polyhedron of 1 is ‘square’ pyramidal, whereas that of 2 is pseudo-octahedral. Compound 1 is triclinic, space group P$\text{l}$, with a = 12.704(2) Å, b = 8.655(2) Å, c = 8.820(2) Å, α = 105.42(1)°, β = 89.87(1)°, γ = 107.60(1)°, V = 888 ų, and Z = 2; 2 is monoclinic, space group P2₁/c, with a = 15.358(4) Å, b = 7.304(3) Å, c = 17.442(4) Å, β = 101.00(2)°, V = 1921 ų, and Z = 4.     

Antibacterial,antifungal and in vitro antileukaemia activity of metal complexes with thiosemicarbazones

1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone 4‐ethyl‐thiosemicarbazone (HL) and its copper(II), vanadium(V) and nickel(II) complexes: [Cu(L)(Cl)]·C₂H₅OH·( 1 ), [Cu(L)₂]·H₂O ( 2 ), [Cu(L)(Br)]·H₂O·CH₃OH ( 3 ), [Cu(L)(NO₃)]·2C₂H₅OH ( 4 ), [VO₂(L)]·2H₂O ( 5 ), [Ni(L)₂]·H₂O ( 6 ), were synthesized and characterized. The ligand has been characterized by elemental analyses, IR, ¹H NMR and ¹³C NMR spectroscopy. The tridentate nature of the ligand is evident from the IR spectra. The copper(II), vanadium(V) and nickel(II) complexes have been characterized by different physico‐chemical techniques such as molar conductivity, magnetic susceptibility measurements and electronic, infrared and electron paramagnetic resonance spectral studies. The structures of the ligand and its copper(II) ( 2 , 4 ), and vanadium(V) ( 5 ) complexes have been determined by single‐crystal X‐ray diffraction. The composition of the coordination polyhedron of the central atom in 2 , 4 and 5 is different. The tetrahedral coordination geometry of Cu was found in complex 2 while in complex 4 , it is square planar, in complex 5 the coordination polyhedron of the central ion is distorted square pyramid. The in vitro antibacterial activity of the complexes against Escherichia coli, Salmonella abony, Staphylococcus aureus, Bacillus cereus and the antifungal activity against Candida albicans strains was higher for the metal complexes than for free ligand. The effect of the free ligand and its metal complexes on the proliferation of HL‐60 cells was tested.     

Synthesis and characterization of technetium(V) complexes with tridentate schiff base ligands. X-ray crystal structure of chloro[N-(2-hydroxyphenyl)salicylideneiminato]oxotechnetium(V)

Five-coordinate technetium(V) complexes of the form TcO(L)Cl where L is one of the two tridentate Schiff base ligands N-(2-oxidophenyl)salicylideneiminate or N-(2-mercaptophenyl)salicylideneiminate have been synthesized and characterized. These neutral complexes precipitate from methanol upon reaction of the Schiff base ligand with TcOCl₄^?. A single crystal X-ray structure determination shows that the chloro [[N-(2-oxidophenyl)salicylideneiminato](2?)-N,O,O′]oxotechnetium(V) complex, [TcO(C₁₃H₉NO₂)Cl], formula weight 362, has a distorted square pyramidal coordination geometry with the oxo ligand in the axial position. The steric requirements of the oxo group cause the Tc atom to be displayed 0.67 Å out of the mean equatorial plane of the other four donor atoms. This complex crystallizes in the monoclinic space group P2₁/a with a = 13.423(6) Å, b = 12.570(5) Å, c = 7.769(3) Å, β = 106.53(5)°, V = 1256.7(9) ų, and Z = 4. The structure has been refined to R = 0.047 for 1775 observed reflections.     

A new hydroxo-bridged thorium(IV) dimer: Preparation and structure of di-μ-hydroxo-bis[aquanitrato(2,6-diacetylpyridinedisemicarbazone)thorium(IV)] nitrate tetrahydrate

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Th(NO₃)₄ in ethanolwater mixture and a di-μ-hydroxo Th(IV) dimer is formed. The compound [Th₂(OH)₂(DAPSC)₂(NO₃)₂(H₂O)₂](NO₃)₄·4H₂O (I) is monoclinic, space group P2₁/n with a = 10.705(1), b = 19.008(2), c = 11.782(1) Å, β = 107.82(2)°, V = 2282(1) ų and Z = 2. Detailed X-ray structural analysis showed that each thorium atom in the complex is coordinated to one pentadentate DAPSC ligand, which is subjected to a considerable distortion, one bidentate nitrate group, one water ligand and two bridging hydroxo groups. The coordination number is ten and the best presentation of the polyhedron is that of a distorted bicapped square antiprism. The ThTh separation is 4.0181(6) Å and the average ThO(H) bridge is 2.366 Å. The structure was refined using 3185 reflections to an R value of 5.0%.     

Magnetic and luminescence characteristics of dinuclear complexes of lanthanides and a phenolic schiff base macrocyclic ligand

The magnetic and luminescence characteristics of trimorphic homodinuclear macrocyclic complexes of lanthanides and a 2:2 phenolate Schiff's base L, derived from 2,6-diformyl-p-cresol and triethylenetetramine were determined. The complexes of Pr³⁺ exhibit non-Curie-Weiss temperature dependent magnetic susceptibilities for which satisfactory fits to an axial relationship depends on crystal field splitting and a weak binuclear Pr³⁺Pr³⁺ antiferromagnetic interaction. The exchange interaction parameters are zJ′ = −2.2, −4.4 and −7.0 cm ⁻¹ for ‘off-white’ Pr₂L(NO₃)₄·2H₂O, ‘yellow’ Pr₂L(NO₃)₄, and ‘orange’ Pr₂L(NO₃)₂(OH)₂, respectively. In contrast, magnetic susceptibilities of the Ln₂L(NO₃)₃(OH) complexes (Ln = Dy, Ho) follow Curie-Weiss behavior over the entire temperature range (6 K to 300 K). The complexes of closed shell ions La³⁺, Lu³⁺, Y³⁺ and those of the half filled shell ion Gd³⁺ exhibit a strong ligand fluorescence in the 450 nm to 650 nm range with decay times at 77 K of 5–8 ns for Ln≠Gd or 2–4 ns for Ln = Gd. The complexes of Gd³⁺ also exhibit a phosphorescence at 600 nm (decay time ∼ 200 μs). The complexes containing Ce³⁺, Eu³⁺, Tb³⁺ and Er³⁺ show very weak ligand luminescence indicative of effective quenching processes. Sensitized emission from the lanthanide ion is observed only with the Eu³⁺ complexes (⁵D_o → ⁷F_j transitions). The emission lifetimes are on the order of 250 μs in the pure Eu³⁺ complexes. The emission decay curves from dilute samples of Eu³⁺ in ‘off-white’ La₂L(NO₃)_4nH₂O show a noticeable rise time as well as a biphasic decay (fast component ∼ 400 μs; slow component ∼ 2500 μs). The luminescing states of L and Eu³⁺ have a common excitation spectrum which is similar to the electronic absorption spectrum of L indicating that ligand-to-metal ion energy transfer processes are dominant. Overall the result if this study suggest that the spectral properties of the complexes are determined by the coordination mode of the lanthanide ions to the Schiff base portion of macrocyclic ligand.     

Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands

A series of four mononuclear manganese (II) complexes with the N-tridentate neutral ligands 2,2^′:6,2^′′-terpyridine (terpy) and N,N-bis(2-pyridylmethyl)ethylamine (bpea) have been synthesized and crystallographically characterized. The complexes have five- to seven-coordinate manganese(II) ions depending on the additional ligands used. The [Mn(bpea)(Br)₂] complex (1) has a five-coordinated manganese atom with a bipyramidal trigonal geometry, while [Mn(terpy)₂](I)₂ (2) is hexa-coordinated with a distorted octahedral geometry. Otherwise, the reactions of Mn(NO₃)₂ · 4H₂O with terpy or bpea afforded novel seven-coordinate complexes [Mn(terpy)(NO₃)₂(H₂O)] (3) and [Mn(bpea)(NO₃)₂] (4), respectively. 3 has a coordination polyhedron best described as a distorted pentagonal bipyramid geometry with one nitrate acting as a bidentate chelating ligand and the other nitrate as a monodentate one. 4 possesses a highly distorted polyhedron geometry with two bidentate chelating nitrate ligands. These complexes represent unusual examples of structurally characterized complexes with a coordination number seven for the Mn(II) ion and join a small family of nitrate complexes.     

Uranyl complexes of acetamidoxime and benzamidoxime. Preparation,characterization, and crystal structure

The uranyl complexes [UO₂(acetamidoxime)₄](NO₃)₂ (1) and [UO₂(benzamidoxime)₄](NO)₃)₂·χS (S = nitromethane or 1,2-dichloroethane, χ < 1) (2) were prepared by the reaction of uranyl nitrate with the corresponding amidoxime in ethanolic solution, and characterized by thermal analysis and infrared spectroscopy. The crystal structures of the acetamidoxime complex and the 1,2-dichloroethane-containing benzamidoxime complex (2a) were determined by single crystal X-ray diffraction measurements and refined R₁ = 0.018 and 0.070, respectively. 1 crystallizes in the monoclinic space group I2/c with a = 14.929(3), b = 8.946(2), c = 16.790(4) Å, β = 96.01(2)° and Z = 4, whereas crystals of 2a are triclinic, space group P $\text{1}$ with a = 9.890(4), b = 14.226(6), c = 15.227(6) Å, α = 75.76(3), β = 87.13(3), γ = 81.22(3)° and Z = 2. In both complexes the linear uranyl group is equatorially surrounded by four oxygen atoms of monodentate amidoxime ligands, the mean bond lengths in 1 and 2a being: UO_uranyl = 1.775 and 1.78 Å and UO_amidoxime = 2.308 and 2.26 Å, respectively. In accordance with infrared spectroscopic results the nitrate ions are not coordinated to uranium, but interact with the ligand molecules via hydrogen bonds.     

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.     

Structural studies of lanthanide complexes with tetradentate nitrogen ligands

Complexes have been synthesised with bis(2-pyridine carboxaldehyde) ethylenediimine (1) and bis(2-pyridine carboxaldehyde)propylene-1,3-diimine (2) with all of the available lanthanide trinitrates. Crystal structures were obtained for all but one complex with 1 and for all but one complex with 2. Four distinct structural types were established for 1 but only two for 2, although in all cases the structures contained one ligand bound to the metal in a tetradentate fashion. With 1, the four different structures of the lanthanide(III) nitrate complexes included 11-coordinate [Ln(1)(NO₃)₃(H₂O)] for Ln = La; 10 coordinate [Ln(1)(NO₃)₃(H₂O)] with one monodentate and two bidentate nitrates for Ln = Ce, then 10-coordinate [Ln(1)(NO₃)₃] for Ln = Pr-Yb with three bidentate nitrates; and 9-coordinate [Ln(1)(NO₃)₃] with one monodentate and two bidentate nitrates for Ln = Lu. On the other hand for 2 only two distinct types of structure are obtained, the first type with Ln = La-Pr and the second type for Ln = Sm-Lu, although all are 10-coordinate with stoichiometry [Ln(2)(NO₃)₃]. The difference between the two types is in the disposition of the ligand relative to the nitrates. With the larger lanthanides La-Pr the ligand is found on one side of the coordination sphere with the three nitrate anions on the other. In these structures, the ligand is folded such that the angle between the two pyridine rings approaches 90°, while with the smaller lanthanides Sm-Lu, two nitrates are found on one side of the ligand and one nitrate on the other and the ligand is in an extended conformation such that the two pyridine rings are close to being coplanar. In both series of structures, the Ln-N and Ln-O bond lengths were consistent with the lanthanide contraction though there are significant variations between ostensibly equivalent bonds which are indicative of intramolecular hydrogen bonding and steric crowding in the complexes.     

Solution and solid-state structures of lanthanide nitrate complexes with [(MeO)2P(O)]2C(OH)R (R=Me,tBu)

The complexes Ln(NO₃)₃L^a ₂ (L^a=[(MeO)₂P(O)]₂C(OH)Me; Ln=La–Er) and Ln(NO₃)₃L^b ₂ (L^b=[(MeO)₂P(O)]₂C(OH)^tBu); Ln=La–Lu) have been synthesised. The solid-state structures examined by IR spectroscopy, single crystal X-ray diffraction and extended X-ray absorption fine structure show uniformity across the series up to Dy, the metal being ten coordinate. Solution structures have been examined by ³¹P NMR spectroscopy, conductivity, electrospray mass spectrometry and EXAFS, and results indicate that solution structures fall into two groups, one for the lighter (La–Sm) and one for the heavier (Eu–Lu) lanthanides. This structural change involves the diphosphonate ligands, which appear to be monodenate for the heavier metals, affording these a coordination number of eight.     

Copper(II) nitrato and chloro complexes with sterically hindered tridentate ligands: Influence of ligand framework and charge on their structure and physicochemical properties

Copper(II) coordination complexes of the neutral ligand, tris(3-tert-butyl-5-methyl-1-pyrazolyl)methane (L2′), i.e. the copper(II) nitrato complexes [Cu(L2′)(NO₃)][Cu(NO₃)₄]_1/2 (1) and [Cu(L2′)(NO₃)](ClO₄) (2) and the copper(II) chloro complex [Cu(L2′)(Cl)](ClO₄) (3), and its anionic borate analogue, hydrotris(3-tert-butyl-5-methyl-1-pyrazolyl)borate (L2⁻), i.e. the copper(II) nitrato complex [Cu(L2)(NO₃)] (4) and the copper(II) chloro complex [Cu(L2)(Cl)] (5), were synthesized in order to investigate the influence of ligand framework and charge on their structure and physicochemical properties. While X-ray crystallography did not show any definitive trends in terms of copper(II) atom geometry in four-coordinate copper(II) chloro complexes 3 and 5, different structural trends were observed in five-coordinate copper(II) nitrato complexes 1, 2, and 4. These complexes were also characterized by spectroscopic techniques, namely, UV-Vis, ESR, IR/far-IR, and X-ray absorption spectroscopy.     

Iron(III) nitrate complexes with linear pentacoordinate ligands and their base hydrolysis products

The complexes, Fe(saldpt)NO₃, [Fe(salmedpt)]₂(NO₃)(OH), Fe(saldien)NO₃, and Fe(salmedien)NO₃·CH₂Cl₂, have been prepared. Solid state properties (IR spectra, Mössbauer spectra and magnetic moments) and solution properties (electronic spectra, PMR spectra, conductivities and cyclic voltammograms) have been measured. The saldpt and saldien compounds when reacted with aqueous KOH formed Fe(saldpt)sal and Fe(saldien)OC₂H₅·H₂O. Single crystals of Fe(saldpt)sal were prepared and examined. Crystal data: Fe(saldpt)sal: monoclinic, space group P2₁/c(#14), a=12.486(5), b=18.502(8), c=10.870(5) Å, β=104.23(3)°, V=2434(2) ų, Z=4, D_c=1.40 g cm⁻³, R=0.0473 (R_w=0.0681) for 317 parameters and 2107 data with F_o² > 3σ(F_o²).     

Metal—phenoxyalkanoic acid interactions. Part 14. The crystal and molecular structures of diaquabis(4-fluorophenoxyacetato)copper(II) bis(4-fluorophenoxyacetic acid)dihydrate and tetra-μ-(4-fluorophenoxyacetato-0,0′)-bis[(2-aminopyrimidine)copper(II)]

The crystal structures of two copper(II) complexes of 4-fluorophenoxyacetic acid (4-FPAH) have been determined by X-ray diffraction. [Cu(4-FPA)₂(H₂O)₂]·2(4-FPAH)·2H₂O (1) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 14.808(2), b = 9.832(2), c = 6.847(2) Å, α = 87.77(2), β = 98.41(2), γ = 112.33(2)° and was refined to a residual of 0.038 for 1697 ‘observed’ reflections. The coordination sphere in this complex is tetragonally distorted octahedral comprising two waters [CuO, 1.940(3) Å], two unidentate carboxylate oxygens [CuO, 1.942(2) Å] and two ether oxygens [CuO, 2.471(2) Å]. Two adducted [4-FPAH] acid molecules are linked to the un-coordinated oxygens of the acid ligands by hydrogen bonds [2.547(4) Å]. [Cu₂(4-FPA)₄(2-aminopyrimidine)₂] (2) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 12.688(2), b = 11.422(2), c = 7.951(1) Å, α = 78.74(1), β = 107.51(1), γ = 75.78(1)°, and was refined to a residual of 0.042 for 2683 ‘observed’ reflections. (2) is a centrosymmetric tetracarboxylate bridged dimer with four similar CuO (equatorial) distances [1.967–1.987 Å; 1.977(3) Å mean] and the axial position occupied by the hetero nitrogen of the 2-aminopyrimidine ligand [CuN, 2.176(3) Å]. The Cu---Cu separation is 2.710(1) Å. Crystal data are also presented which confirm the isostructurality of complex (2) with [Cu₂(phenoxyacetate)₄(2-aminopyrimidine)₂], the Co^II, Mg^II and Mn^II4-fluorophenoxyacetate complexes with their phenoxyacetic and 4-chlorophenoxyacetic acid analogues, and of Cd^II4-fluorophenoxyacetate with Cd^II and Zn^II phenoxyacetates.     

Three coordination modes of the pentadentate ligand 2,6-diacetylpyridinedisemicarbazone

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Cr(NO₃)₃·9H₂O and forms two kinds of complexes. At pH=3, the ligand is singly-deprotonated and crystals of [Cr- (DAPSCH)(H₂O)₂](NO₃)₂·H₂O (Ia) are obtained. Evaporation of a solution at pH=0, yields crystals of [Cr(DAPSC)(H₂O)₂](NO₃)₃·2H₂O (II) in which the ligand is fully protonated. The reaction of DAPSC with UO₂(O₂CCH₃)₂ in methanol, followed by crystallization of the product from DMSO yields crystals of [UO₂(DAPSC2H)(H₂O)]·2DMSO (III) in which the ligand is fully deprotonated. Compound Ia is monoclinic, space group P2₁/n with a=11.746(1), b=14.752(2), c=11.866(1) Å,β=105.53(2)°, V= 1981(1) ų and Z=4. Compound II is monoclinic, space group, P2₁/n with a=38.000(3), b= 14.939(2), c=8.233(1) Å, β=96.12(2)°, V= 4647(1) Å and Z=8. Compound III is monoclinic, space group P2₁/n with a=18.048(2), b=15.207(2), c=8.842(1) Å,β=97.72(2)°, V=2405(1) ų and Z=4. The structures were refined using 2084, 4169 and 2516 reflections to R values of 4.4%, 7.8% and 4.8% respectively.