Synthetic, structural and solution speciation studies on binary Al(III)–(carboxy)phosphonate systems. Relevance to the neurotoxic potential of Al(III)

Efforts to delineate the interactions of neurotoxic Al(III) with low molecular mass substrates relevant to neurodegenerative processes, led to the investigation of the pH-specific synthetic chemistry of the binary Al(III)-[N-(phosphonomethyl) iminodiacetic acid] (Al-NTAP), Al(III)-[nitrilo-tris(methylene-phosphonic acid)] (Al-NTA3P), and Al(III)-[1-hydroxy ethylidene-1,1-diphosphonic acid] (Al-HEDP) systems, in correlation with solution speciation studies. Reaction of Al(NO₃)₃·9H₂O with NTAP at pH 7.0 and 4.0 afforded the new species (CH₆N₃)₄[Al₂(C₅H₆NPO₇)₂(OH)₂]·8H₂O (1) and (NH₄)₂[Al₂(C₅H₆NPO₇)₂(H₂O)₂]·4H₂O (2), while reaction of Al(NO₃)₃·9H₂O with NTA3P led to K₈[Al₂(C₃H₆NP₃O₉)₂(OH)₂]·20H₂O (3). Complexes 1–3 were characterized by elemental analysis, FT-IR, ¹³C, ³¹P, ¹H NMR (for 1–2 solid state and solution NMR where feasible), and X-ray crystallography. The structures of 1–3 reveal the presence of uniquely defined dinuclear complexes of octahedral Al(III) bound to fully deprotonated phosphonate ligands, water and hydroxo moieties. The aqueous solution speciation studies on the aforementioned binary systems project a clear picture of the binary Al(III)–(carboxy)phosphonate interactions and species under variable pH-conditions and specific Al(III):ligand stoichiometry. The concurrent solid state and solution work (a) exemplifies essential structural and chemical attributes of soluble aqueous species, reflecting well-defined interactions of Al(III) with phosphosubstrates and (b) strengthens the potential linkage of neurotoxic Al(III) chemical reactivity toward O,N-containing (carboxy)phosphate-rich cellular targets.     

The crystal structures of 4,4′-bipyridinium μ-(4,4′-bipyridine)bis[diaquatetranitratoneodymate(III)]-tris(4,4′-bipyridine) and a second monoclinic form of triaquatrinitratoholmium(III) – bis (4,4′-bipyridine)

The structures of (4-bipyH)₂[(μ-4-bipy)Nd₂(NO₃)₈(H₂O)₄]·3(4-bipy) (4-bipy = 4,4′-bipyridine; P2₁/c, a = 18.723(10), b = 10.720(6), c = 18.027(10) Å, β = 94.43(5)°, Z = 2; R = 0.066 for 4931 (diffractometer data) and of a second monoclinic form of [Ho(NO₃)₃(H₂O)₃]·2(4-bipy) (P2₁/c, a = 15.830(10), b = 21.44(3), c = 15.70(3) Å, β = 100.4(2)°, Z = 8; R = 0.091 for 2335 film data) are reported. In the first compound pairs of Nd atoms are bridged across a crystal inversion centre by a 4-bipy ligand, and 10-coordination is completed by one monodentate NO₃, three bidentate NO₃, and two H₂O ligands, with bond lengths Nd---N 2.70, Nd---OH₂(av.) 2.44, Nd---O(NO₃, av.) 2.56 Å. The second compound has a variant of the previously-reported monoclinic [Y(NO₃)₃(H₂O)₃]·2(4-bipy) structure, with doubling of the unit cell on a but with essentially no change in the geometry and orientation of the nine-coordinate complex. In both compounds the non-coordinated, non-protonated 4-bipy N atoms form hydrogen bonds with ligand H₂O.     

Synthesis and magnetic properties of bis(μ-hydroxo)bis[(2,2 ′-bipyridyl)copper(II)] squarate. Crystal structure of bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] squarate tetrahydrate

The compound [Cu₂(bipy)₂(OH)₂](C₄O₄)·5.5H₂O, where bipy and C₄O₄²⁻ correspond to 2,2′-bipyridyl and squarate (dianion of 3,4-dihydroxy-3-cyclo- butene-1,3-dione) respectively, has been synthesized. Its magnetic properties have been investigated in the 2–300 K temperature range. The ground state is a spin-triplet state, with a singlet-triplet separation of 145 cm⁻¹. The EPR powder spectrum confirms the nature of the ground state.Well-formed single crystals of the tetrahydrate, [Cu₂(bipy)₂(OH)₂](C₄O₄)·4H₂O, were grown from aqueous solutions and characterized by X-ray diffraction. The system is triclinic, space group P , with a = 9.022(2), b = 9.040(2), c = 8.409(2) Å, α = 103.51(2), β = 103.42(3), γ = 103.37(2)°, V = 642.9(3) ų, Z = 1, D_x = 1.699 g cm⁻³, μ(Mo Kα) = 17.208 cm⁻¹, F(000) = 336 and T= 295 K. A total of 2251 data were collected over the range 1θ25°; of these, 1993 (independent and with I3σ(I)) were used in the structural analysis. The final R and R_w residuals were 0.034 and 0.038 respectively. The structure contains squarato-O¹, O³-bridged bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] units forming zigzag one-dimensional chains. Each copper atom is in a square-pyramidal environment with the two nitrogen atoms of 2,2′-bipyridyl and the two oxygen atoms of the hydroxo groups building the basal plane and another oxygen atom of the squarate lying in the apical position.The magnetic properties are discussed in the light of spectral and structural data and compared with the reported ones for other bis(μ-hydroxo)bis[(2,2′-bipyridyl)copper(II)] complexes.     

Influence of the geometry around the manganese ion on the peroxidase and catalase activities of Mn(III)-Schiff base complexes

The peroxidase and catalase activities of eighteen manganese-Schiff base complexes have been studied. A correlation between the structure of the complexes and their catalytic activity is discussed on the basis of the variety of systems studied. Complexes 1-18 have the general formulae [MnLⁿ(D)₂](X)(H₂O/CH₃OH)_m, where Lⁿ = L¹-L¹³; D = H₂O, CH₃OH or Cl; m = 0-2.5 and X = NO₃⁻, Cl⁻, ClO₄⁻, CH₃COO⁻, C₂H₅COO⁻ or C₅H₁₁COO⁻. The dianionic tetradentate Schiff base ligands H₂Lⁿ are the result of the condensation of different substituted (OMe-, OEt-, Br-, Cl-) hydroxybenzaldehyde with diverse diamines (1,2-diaminoethane for H₂L¹-H₂L²; 1,2-diamino-2-methylethane for H₂L³-H₂L⁴; 1,2-diamino-2,2-dimethylethane for H₂L⁵; 1,2-diphenylenediamine for H₂L⁶-H₂L⁷; 1,3-diaminopropane for H₂L⁸-H₂L¹¹; 1,3-diamino-2,2-dimethylpropane for H₂L¹²-H₂L¹³). The new Mn(III) complexes [MnL¹(H₂O)Cl](H₂O)_2.5 (2), [MnL²(H₂O)₂](NO₃)(H₂O) (4), [MnL⁶(H₂O)₂][MnL⁶(CH₃OH)(H₂O)](NO₃)₂(CH₃OH) (8), [MnL⁶(H₂O)(OAc)](H₂O) (9) and [MnL⁷(H₂O)₂](NO₃)(CH₃OH)₂ (12) were isolated and characterised by elemental analysis, magnetic susceptibility and conductivity measurements, redox studies, ESI spectrometry and UV, IR, paramagnetic ¹H NMR, and EPR spectroscopies. X-ray crystallographic studies of these complexes and of the ligand H₂L⁶ are also reported. The crystal structures of the rest of the complexes have been previously published and herein we have only revised their study by those techniques still not reported (EPR and ¹H NMR for some of these compounds) and which help to establish their structures in solution. Complexes 1-12 behave as more efficient mimics of peroxidase or catalase in contrast with 13-18. The analysis between the catalytic activity and the structure of the compounds emphasises the significance of the existence of a vacant or a labile position in the coordination sphere of the catalyst.     

Rhodium aryloxide complexes containing terdentate nitrogen ligands, C-O bond formation, hydrogen bonding with phenol and oxidative addition reactions. Molecular structure of an Rh(III)-acetyl complex

The new rhodium(I) phenoxide complexes [Rh(OPh) (2,6-(CH=R²)₂C₅H₃N)] (R² = i-Pr(3), t-Bu(4)) containing strongly electrondonating N-N′-N ligands, have been prepared by a metathesis reaction of [RhCl(2,6-(CH=R²)₂C₅H₃N)] (R² = i-Pr (1), t-Bu (2)) with NaOPh. These rhodium(I) phenoxide complexes 3 and 4, which are very sensitive to O₂ but stable towards H₂O, give with phenol the adducts [Rh(OPh) (2,6-(CH=NR²)₂C₅H₃N)] · HOPh (R2 = i-Pr (5), t-Bu (6)), which contain strong O-HO hydrogen bonds. The hydrogen bonded phenol could not be extracted with diethyl ether, while no exchange of the hydrogen bonded phenol and the phenoxide ligand in 4 is observed on the NMR time scale. However, a small excess of phenol results in exchange of the hydrogen bonded phenol, the coordinated phenoxide ligand and free phenol on the NMR time scale. Reaction of 3 and 4 with p-nitrophenol afforded [Rh(OC₆H₄-(NO₂-4))(2,6-(CH=R²)₂C₅H₃N)] · HOPh (R² = i-Pr (7), t-Bu (8)) in which the formed phenol is hydrogen bonded to the Rh(I)-OC₆H₄-(NO₂-4) moiety. The O-HO bond is less strong than in 5 and 6, as the hydrogen bonded phenol could be removed by diethyl ether.Treatment of 3 with acetyl chloride and benzoyl chloride in benzene at room temperature gave phenylacetate and RhCl₂(C(O)C₆H₃) (2,6(C(H)=N-i-Pr)₂C₅H₃N)] (15), and phenylbenzoate and [RhCl₂(C(O)Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (19), respectively. Complex 15 and the analogous complex [RhCl₂(C(O)CH₃) (2,6-(C(H)=N-t-Bu)₂C₅H₃N)] (16) could also be prepared directly from acetyl chloride and 1 or 2, respectively. The single crystal X-ray determination of complex 16, monoclinic, space group P2₁/_c, a = 10.0477(5), b= 11.7268(6), c= 19.2336(9) Å, β = 92.041(4)°, Z = 4, R₁ = 0.0281, shows that the acetyl group occupies an axial position, while the N-N′-N ligand is positioned equatorially. In solution this geometry remains unchanged as was shown by variable temperature ¹H NMR measurements. When the oxidative addition of acetyl chloride to 3 was carried out at −78°C in toluene the intermediate complex [RhCl(OPh) (C(O)Me) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (11) could be isolated, which at room temperature reductively eliminates phenylacetate with formation of 1. Oxidative addition of acetyl chlori de to 4 at room temperature gives [RhCl(OPh) (C(O)Me) (2,6-(C(H)=Nt-Bu)₂C₅H₃N)] (12) which yields phenylacetate and 2 at 70°C in benzene by inductive elimination. Treatment of 3 with two equivalents of benzyl chloride afforded a mixture of [RhCl(OPh) (CH₂Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (13) and [RhCl₂(CH₂Ph) (2,6-(C(H)=N-i-Pr)₂C₅H₃N)] (17) and some non-characterizable organic products, while 4 only yielded [RhCl(OPh) (CH₂Ph) (2,6-(C(H)=N-tBu)₂C₅H₃N)] (14).     

3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ-THC and related compounds: synthesis of selective ligands for the CB2 receptor

The synthesis and pharmacology of 15 1-deoxy-Δ⁸-THC analogues, several of which have high affinity for the CB₂ receptor, are described. The deoxy cannabinoids include 1-deoxy-11-hydroxy-Δ⁸-THC (5), 1-deoxy-Δ⁸-THC (6), 1-deoxy-3-butyl-Δ⁸-THC (7), 1-deoxy-3-hexyl-Δ⁸-THC (8) and a series of 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=0–4, 6, 7, where n=the number of carbon atoms in the side chain−2). Three derivatives (17–19) of deoxynabilone (16) were also prepared. The affinities of each compound for the CB₁ and CB₂ receptors were determined employing previously described procedures. Five of the 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=1–5) have high affinity (K_i=<20 nM) for the CB₂ receptor. Four of them (2, n=1–4) also have little affinity for the CB₁ receptor (K_i=>295 nM). 3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ⁸-THC (2, n=2) has very high affinity for the CB₂ receptor (K_i=3.4±1.0 nM) and little affinity for the CB₁ receptor (K_i=677±132 nM).

Scheme 3. (a) (C₆H₅)₃PCH₃⁺ Br⁻, n-BuLi/THF, 65°C; (b) LiAlH₄/THF, 25°C; (c) KBH(sec-Bu)₃/THF, −78 to 25°C then H₂O₂/NaOH.     

Metal dependent coordination of biomolecular ligand: X-ray crystal structures of copper, cobalt and calcium complexes of (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate, an oxidized pyridoxal 5-phosphate

X-ray crystal analyses of divalent copper, cobalt and calcium complexes of monoanionic (3-hydroxy-5-(hydroxymethyl)-2-methylisonicotinic acid) 5-phosphate (L₁C₈H₉NO₇P⁻) revealed the chemical compositions of Cu ---L·3H₂O(1), Co ---L·5H₂O(2) and Ca·L₂·7H₂O (3) and the coordination structures which depend on the coordination abilities and chemical properties of the respective metal ions. Although 1 and 2 crystals showed similar features, i.e., presence of the metal ion at the crystallographic center of symmetry and octahedral six-coordination, the patterns of coordination with the ligand molecules differed. While direct coordination to the L carboxyl oxygen was observed in 1 crystals, all ligation positions in 2 crystals were occupied by water molecules. On the other hand, 3 crystals formed a pentagonal bipyramidal structure (seven-coordination), where oxygens of L phosphates and water molecules coordinated to the calcium ion. Each of the complex structures showed characteristic molecular packing depending on the pattern of coordination to the respective metal ion. L is monoanionic in all complex crystals, where the phosphate and carboxyl groups are deprotonated and pyridine nitrogen is protonated, and is neutralized by each metal ion. Crystal data: 1, monoclinic, space group P2₁/c, A = 5.4129(6), B = 10.515(2), C = 22.770(2) Å, β = 91.853(9)°, Z = 4, R = 0.0404 for 1834 observed reflections; 2, triclinic, space group

Full-size image

, c = 6.789(3) Å, α = 96.84(3), β = 109.10(3), γ = 100.50(2)°, Z = 2, R = 0.0684 for 1605 observed reflections; 3, triclinic, , a = 10.069(2), B = 14.501(3), c = 10.051(1) Å, α = 100.75(1), β = 97.28(2), γ = 76.18(2)°, Z = 2, R = 0.0540 for 3637 observed reflections.     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

Synthesis and characterization of new oligomeric and polymeric complexes based on the [Cu(bpca)] unit [Hbpca = bis(2-pyridylcarbonyl)amine]

Five novel bpca-based Cu(II) polynuclear coordination compounds [Hbpca = bis(2-pyridylcarbonyl)amine] were prepared using the [Cu(bpca)(H₂O)₂](NO₃)·2H₂O (1) building block and characterized by single crystal X-ray diffraction. We have also isolated and characterized two new crystal forms of the starting species, with lower water contents. Three of the new products are dinuclear complexes obtained by reacting 1 with different rigid or flexible spacer ligands: [Cu₂(bpca)₂(H₂O)₂(bipy)](NO₃)₂·6H₂O (2) (bipy = 4,4′-bipyridine) and [Cu₂(bpca)₂(H₂O)₂(bpete)](NO₃)₂·xH₂O (3) [bpete = (E)-1,2-di(pyridin-4-yl)ethane] are linear dumbbell-like species with Cu?Cu separations of 11.075 and 13.275 Å, respectively. The third dinuclear compound, [Cu₂(bpca)₂(H₂O)₂(bpx)](NO₃)₂·8H₂O (4) [bpx = 1,4-bis((1H-pyrazol-1-yl)methyl)benzene], with the flexible bpx ligand, assumes an unusual S-shaped conformation and shows a quite shorter Cu?Cu contact of 6.869 Å only. We have also obtained a chiral 1D neutral polymeric complex, [Cu₃(bpca)₂(bipy)₃(NO₃)₄]·6H₂O (5), that shows a central linear -Cu-bipy-Cu- chain, with all these Cu atoms connected to two lateral [Cu(bpca)(NO₃)₂]⁻ groups on two opposite sides by means of bipy spacers. An unprecedented type of Cu(II) neutral trinuclear complex, [Cu₃(bpca)₂(H₂O)₂(NO₃)₂] (6), was obtained which has a centrosymmetric structure with two external [Cu(bpca)(NO₃)₂]⁻ units chelating on a central copper atom via the two pairs of carbonyl groups of the bpca ligands. The central metal is octahedral with two axial water molecules, while the two lateral Cu atoms are in square pyramidal geometry; the Cu?Cu separation is 5.205 Å. The magnetic properties of 6 have been rationalized through a ferromagnetic coupling between the central metal ion and the peripheral ones which are coupled by a smaller antiferromagnetic interaction. DFT calculations have been also performed in order to give a better insight into magnetic interactions.     

Syntheses, structures and properties of copper(II) complexes containing N-(2-hydroxybenzyl)-amino amide ligands

Four copper(II) complexes containing the reduced Schiff base ligands, namely, N-(2-hydroxybenzyl)-glycinamide (Hsglym) and N-(2-hydroxybenzyl)-l-alaninamide (Hsalam) have been synthesized and characterized. The crystal structures of [Cu₂(sglym)₂Cl₂] (1), [Cu₂(salam)₂(NO₃)₂] · H₂O (3), [Cu₂(salam)₂(NO₃)(H₂O)](NO₃) · 1.5H₂O (4), [Cu₂(salam)₂](ClO₄)₂ · 2H₂O (5) show that the Cu(II) atoms are bridged by two phenolato oxygen atoms in the dimers. The sglym ligand bonded to Cu(II) in facial manner while salam ligand prefers to bind to Cu(II) in meridonal geometry. Variable temperature magnetic studies of 3 showed it is antiferromagnetic. These Cu(II) complexes and [Cu₂(sglym)₂(NO₃)₂] (2), exhibit very small catecholase activity as compared to the corresponding complexes containing acid functional groups.     

Synthesis and crystal structures of di- and tetra-nuclear dicarboxylate-bridged copper(II) complexes

Three new Cu(II) complexes, [Cu₂(C₃H₂O₄)(phen)₂(H₂O)₃](NO₃)₂(H₂O)₂ (1) (C₃H₂O₄ = malonate, phen = 1,10-phenanthroline), [Cu₂(C₄H₄O₄)(phen)₂(H₂O)₂](NO₃)₂ (2) (C₄H₄O₄ = succinate), and {[Cu₂(phen)₂(H₂O)(NO₃)]₂(C₅H₆O₄)₂}(NO₃)₂ (3) (C₅H₆O₄ = glutarate) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The X-ray analysis reveals that the structures of 1 and 2 are of dinuclear copper(II) complexes bridged by malonate and succinate dianions, respectively, and 3 is a tetranuclear species formed by two {[Cu₂(phen)₂(H₂O)(NO₃)](C₅H₆O₄)} fragments. The copper ions in 1 and 3 show square-pyramidal coordination geometry, while the copper ions in 2 exhibit a square planar geometry. In each complex, the dicarboxylate ligand is coordinated to copper ions as a chelate and monodentate (1), bis-monodentate (2), and bis-bridging ligand toward the copper ions with syn-syn coordination mode (3).     

Synthesis, crystal structures and magnetic characterization of heterodinuclear CuGd and CuTb Schiff base complexes

Preparation, crystal structures and magnetic properties of new heterodinuclear Cu^IIGd^III (1) and Cu^IITb^III (2) complexes [CuLn(L)(NO₃)₂(H₂O)₃MeOH]NO₃·MeOH (where Ln = Gd, Tb) with the hexadentate Schiff-base compartmental ligand N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine (H₂L = C₁₉H₂₀N₂O₄Br₂) (0) have been described. Crystal structure analysis of 1 and 2 revealed that they are isostructural and form discrete dinuclear units with dihedral angle between the O1Cu1O2 and O1Gd1/Tb1O2 planes equal to 2.5(1)° and 2.6(1)°, respectively. The variable-temperature and variable-field magnetic measurements indicate that the metal centers in 1 and 2 are ferromagnetically coupled (J = 7.89 cm⁻¹ for 1). Crystal and molecular structure of the Schiff base ligand (0) has been also reported. The complex formation changes the conformation of Schiff base ligand molecule.     

Binuclear complexes of a new hexadentate macrocyclic ligand. The crystal and molecular structure of [LCu2(CH3CO2)2](ClO4)2·5H2O

The 30-membered hexaaza macrocylic ligand, L (L=3,7,11,18,22,26-hexaazatricyclo-[26.2.2.2^13,16]tetratriaconta-1(31),13(33),14,16(34),28(32),29-hexaene), is capable of forming binuclear complexes with the divalent transition metal ions Ni, Cu and Zn. The two metal ions are bound by the two dipropylenetriamine units of the macrocycle. Extra coordination sites on the metal ions can be occupied by exogenous ligands such as acetate, chloride and thiocyanate. The crystal structure of one of the di-copper complexes is described: [LCu₂(CH₃CO₂)₂](ClO₄)₂·5H₂O crystallizes in the monoclinic space group P2₁/c (No. 14), with a=9.369(2), b=17.644(3), c= 27.466(3) Å, β=92.90(1)°, U=4534.7 ų and Z=4. The Cu1···Cu2 separation is 8.40(3) Å. The access for potential exogenous bridging ligands, to the cavity between the copper ions, is somewhat restricted by the two phenyl units of the macrocycle which appear almost parallel in the structure. The redox potential of the couple L(Cu²⁺)₂/L(Cu⁺)₂, recorded by cyclic voltammetry for the chloride adduct, [LCu₂Cl₂]Cl₂·5H₂O, is −0.061 V versus SCE in DMF.     

Preparation, structures and properties of dinuclear and trinuclear copper(II) complexes bridged by one oximato and one hydroxo ligands

The dinuclear and trinuclear copper(II) complexes [Cu₂(L)(OH)(ClO₄)(phen)(H₂O)]ClO₄ · [Cu₂(L)(OH)(ClO₄)₂(phen)(CH₃OH)] (1) and [Cu₃(L)₂(OH)₂(H₂O)₂](NO₃)₂ (2) (HL=2-[2-(α-pyridyl)ethyl]imino-3-butanone oxime and phen=1,10-phenanthroline) were prepared and their crystal structures have been determined by X-ray crystallography. Complex 1 is composed of [Cu₂(L)(OH)(ClO₄)(phen)(H₂O)]ClO₄ (1a) and [Cu₂(L)(OH)(ClO₄)₂(phen)(CH₃OH)] (1b). In 1a and 1b, one oximato of L and one hydroxo group bridge two copper(II) ions. The linear trinuclear cation [Cu₃(L)₂(OH)₂(H₂O)₂]²⁺ in 2 is centrosymmetric, and one oximato and one hydroxo group bridge the central and terminal copper(II) ions. The strong antiferromagnetic interactions within the dinuclear and trinuclear complexes 1 and 2 have been observed (2J=∼−900 cm⁻¹ for 1 and 2, respectively, H=−2JS₁·S₂).     

Solution structure investigations of olefin Pd(II) and Pt(II) complex ion pairs bearing α-diimine ligands by F, H-HOESY NMR

Complexes [M(η¹,η²-C₈H₁₂OMe)((2,6-(R)₂---C₆H₃)N=C(R′)---C(R′)=N((2,6-(R)₂---C₆H₃))]PF₆ (where M=Pd, R=H and R′₂=Me₂ (1), M=Pd, R=Me and R′₂=Me₂ (2), M=Pd, R=Et and R′₂=Me₂ (3), M=Pd, R=iPr and R′₂=Me₂ (4), M=Pd, R=iPr and R′₂=An (5), M=Pt, R=iPr and R′₂=An (6)) were synthesized by the reaction of [M(η¹,η²-C₈H₁₂OMe)Cl]₂ with the appropriate α-diimine ligand in the presence of NH₄PF₆. Their ion pair structure in solution was investigated by detecting dipolar interactions between protons belonging to the cation and fluorine nuclei of the anion (interionic contacts) in the ¹⁹F, ¹H-HOESY NMR spectra. In complexes 1–4, the anion in solution is located close to the peripheral protons of the α-diimine ligand and it interacts with the R′ protons and with the R protons that point toward the R′ groups. The steric protection of apical position exerted by the R substituents is clearly illustrated by the absence of interionic contacts between any protons of the cycloctenylmethoxy-moiety and the anion for R≥Me in 1–4. In complexes 5 and 6 the interactions between the anion and the peripheral N,N protons also predominate but other anion–cation orientations are significantly present and, consequently, the interionic structure is less specific.     

Synthesis and biological activity of 17α-alkynylamide derivatives of estradiol

Seven estradiol (E₂) derivatives with an alkynylamide side chain at the 17α position were synthesized starting from ethynylestradiol (EE₂). The main chemical step was the coupling reaction of the acetylide ion of EE₂ with carbon dioxide, glutaric anhydride or bromoalkyl ortho ester. The synthesis of these compounds is fast (3–6 steps according to the compound) and is easily achieved with good yield. Five compounds with different side chain lenghts were evaluated for uterotrophic and antiuterotrophic activity in the CD-1 mouse. None of the tested compounds shows estrogenic activity in this sensitive in vitro system. At low doses (1 and 3 μg), a 14–57% inhibition of E₂-induced uterine growth was observed while no additional inhibition was observed at the 10, 20 and 30 μg doses. In human breast carcinoma cells in culture, all compounds show estrogenic activity at high concentrations while only compound 39 (N-buty,N-methyl-8-[3′,17′β-dihydroxy estra-1′,3′,5′(10′)-trien-17′α-yl]-7-octynamide) possesses antiproliferative or antiestrogenic effects. No significant correlation could be demonstrated between alkynylamide side chain length and estrogenic or antiestrogenic activity. Among the compounds tested, the derivative of EE₂ possessing a five-methylene (CH₂) side chain (compound 39) possesses the best antiestrogenic activity (44 ± 7% in the CD-1 mouse uterus assay at the 3μg dose and 57 ± 4% at 0.1 nM in human ZR-75-1 cancer cells in culture).     

Diverse coordination of polynuclear copper(II) complexes constructed from benzene tetracarboxylates

The reaction of aqueous solutions of the preformed 1:1 Cu(ClO₄)₂-polydentate amine with tetrasodium 1,2,4,5-benzene tetracarboxylate (Na₄bta) afforded three different types of polynuclear compounds. These include the tetranuclear complexes: [Cu₄(Medpt)₄(μ₄-bta)(ClO₄)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cu₄(pmdien)₄(μ₄-bta)(H₂O)₄](ClO₄)₄ (2), [Cu₄(Mepea)₄(μ₄-bta)(H₂O)₂](ClO₄)₄(3), [Cu₄(TPA)₄(μ₄-bta)](ClO₄)₄·10H₂O (4) and [Cu₄(tepa)₄(μ₄-bta)](ClO₄)₄·2H₂O (5), the di-nuclear: [Cu₂(DPA)₂(μ₂-bta)(H₂O)₂]·4H₂O (6), [Cu₂(dppa)₂(μ₂-bta)(H₂O)₂]·4H₂O (7) and [Cu₂(pmea)₂(μ₂-bta)]·14H₂O (8) and the trinuclear complex [Cu₃(dppa)₃(μ₃-bta)(H₂O)_2.25](ClO₄)₂·6.5H₂O (9) where Medpt = 3,3′-diamino-N-methyldipropylamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine, Mepea = [2-(2-pyridyl)ethyl]-(2-pyridylmethyl)methylamine, TPA = tris(2-pyridylmethyl)amine, tepa = tris[2-(2-pyridyl)ethyl)]amine, DPA = di(2-pyridymethyl)amine, dppa = N-propanamide-bis(2-pyridylmethyl)amine and pmea = bis(2-pyridylmethyl)-[2-(2-pyridylethyl)]amine. The complexes were structurally characterized by elemental analyses, spectroscopic techniques, and by X-ray crystallography for complexes 1, 2, 4, 6, 7 and 9. X-ray structure of the complexes reveal that bta⁴⁻ is acting as a bridging ligand via its four deprotonated caboxylate groups in 1, 2 and 4, three carboxylate groups in 9 and via two trans-carboxylates in 6 and 7. The complexes exhibit extended supramolecular networks with different dimensionality: 1-D in 2 and 4 due to hydrogen bonds of the type O-H···O, 2-D in 1 and 7, and 3-D network in 6 as a result of hydrogen bonds of the types N-H···O and O-H···O. Magnetic susceptibility measurements showed very weak antiferromagnetic coupling between the Cu^II ions in 1-5, 7-9 (|J| = 0.02-0.87 cm⁻¹) and weak ferromagnetic coupling for 6 (J = 0.08 cm⁻¹).     

Magnetic properties and circular dichroism of 1D chains built from chiral mononuclear and non-chiral trinuclear Cu(II) complexes with α-aminocarboxylates

Coordination polymers Cu(l-Pro)(ClO₄)(H₂O)₂ (1) and Cu₃(Gly)₄(H₂O)₂(NO₃)₂ (2) were synthesized and characterized structurally. Compound 1 possesses the structure of 1D chain, where Cu(II) ions are linked by carboxyl-group in syn-anti conformation in equatorial-equatorial mode. Compound 2 is polymeric chain, consisting from trinuclear blocks Cu₃(Gly)₄(H₂O)₂²⁺. In each of these units Cu(II) ions are linked by carboxyl-group in the same way as in 1, while trinuclear units Cu₃(Gly)₄(H₂O)₂²⁺ are linked by NO₃⁻ ions, acting as the bridges between Cu(II) ions of neighboring trinuclear units. Circular dichroism properties of 1 were studied in solid state and solution. Magnetic measurements revealed that there were ferromagnetic exchange interactions between Cu(II) ions in 1 (J = +1.22(1) cm^-1 for Hamiltonian ) and 2 (J = +1.17(2) cm^-1 for Hamiltonian ).     

Chiral and achiral layered divalent metal aromatic ortho-dicarboxylate coordination polymers with bis(4-pyridylmethyl)piperazine ligands: Luminescent behavior and magnetic properties

Four divalent metal coordination polymers containing bis(4-pyridylmethyl)piperazine (4-bpmp) and the ortho-dicarboxylate ligands phthalate (pht) or 4-methylphthalate (mpht) have been prepared by solvent diffusion or hydrothermal methods. {[Cu₂(pht)₂(H4-bpmp)₂(H₂O)₂](NO₃)₂·H₂O}_n (1) and {[Cu₂(pht)₂(H4-bpmp)₂(H₂O)₂](SO₄)·2H₂O}_n (2) possess chiral cationic layer motifs formed by the junction of [Cu(H₂O)(pht)]_n chains by tethering curled-conformation H4-bpmp⁺ ligands. {[Co(pht)(H₂O)(4-bpmp)]·5.5H₂O}_n (3) displays a (4,4) grid constructed from anti-syn carboxylate-bridged {Co₂(H₂O)₂(pht)₂} dimeric clusters linked by open-conformation 4-bpmp ligands. {[Cd₂(mpht)₂(H₂O)₂(4-bpmp)(H4-bpmp)]ClO₄·4H₂O}_n (4) manifests cationic layered motifs based on neutral [Cd₂(H₂O)₂(mpht)₂] dinuclear units with {CdOC₄O}₂ 12-membered circuits, linked by open-conformation 4-bpmp and H4-bpmp⁺ ligands. Variable-temperature magnetic data indicate likely concomitant zero-field splitting and ferromagnetic coupling in 3. Violet light emission is observed when 4 is subjected to ultraviolet irradiation.     

Construction of a series of 0D, 2D and 3D inorganic-organic hybrid coordination polymers based on octamolybdate and 2-(2-pyridyl)imidazole and its derivative

Four octamolybdate-based compounds, that is, Cu^II₂(L¹)₄(Mo₈O₂₆) (1), Cu^II₂(HL²)₄(Mo₈O₂₆)₂ (2), [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (3) and [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (4) (L¹ = 2-(2-pyridyl)imidazole, L² = 2-(1-(pyridine-3-ylmethyl)-1H-imidazol-2-yl)pyridine), have been hydrothermally synthesized via changing the reaction conditions and structurally characterized by single-crystal X-ray diffraction. With L¹ ligand, we obtained compound 1, which is a 0D molecule and extends to a 3D supramolecular structure via hydrogen-bonding interactions. By using L² instead of L¹ ligand, compound 2 comes into being which is as well a discrete molecule and further extended to a 3D supramolecular structure by hydrogen bonds. Intriguingly, compounds 3 and 4 are supramolecular isomers: the former is a 2D 4-connected network and the latter is a 3D (3,4)-connected framework. The measurements of diffuse reflectance for compounds 1-4 indicate that they are potential wide gap semiconductors.