Synthesis,structural, electrochemical,and spectroscopic studies of some (diimine)ruthenium nitrile complexes

The syntheses of cationic ruthenium(II) complexes [Ru(Me₂-bpy)(PPh₃)₂RR?][PF₆]_x {Me₂-bpy = 4,4?-dimethyl-2,2?-bipyridine, (3) R = Cl, R? = N≡CMe, x = 1, (4) R = Cl, R? = N≡CPh, x = 1, (5) R = R? = N≡CMe, x = 2} and [Ru(Me₂-bpy)(κ²-dppf)RR?][PF₆]_x {dppf = 1,1?-bis(diphenylphosphino)ferrocene, (6) R = Cl, R? = N≡CMe, x = 1, (7) R = Cl, R? = N≡CPh, x = 1, (8) R = R? = N≡CMe, x = 2} are reported, together with their structural confirmation by NMR (³¹P, ¹H) and IR spectroscopy and elemental analysis, and, in the case of trans-[Ru(Me₂-bpy)(PPh₃)₂(N≡CCH₃)Cl][PF₆] (3), by X-ray crystallography. Electronic absorption and emission spectra of the complexes reveal that all complexes except 4 and 6 are emissive in the range 370–400 nm with 8 exhibiting an emission in the blue. Cyclic voltammetry studies of 3–8 show reversible or quasi-reversible redox processes at ca. 1 V, assigned to the Ru(II/III) couple.     

A blue-green-emitting 3D supramolecular compound: synthesis,crystal structure and effect of solvents and temperature on the luminescent properties

A blue-green-emitting three-dimensional supramolecular compound (C₁₀O₂N₂H₈)(C₉O₇H₆) (1) was synthesised under hydrothermal conditions and structurally characterised by elemental analysis, IR spectrum, ¹H NMR and single-crystal X-ray diffraction. The crystal belongs to triclinic system with P 1¯ space group. The crystal structure is stabilised by O–H…O, O–H…N hydrogen bonds and π–π interactions (π–π stacking distance is 3.282 Å). Compound 1 exhibits intense green luminescence in solid state at 298 K (λ_em = 546 nm). In addition, absorption and fluorescence characteristics of compound 1 have been investigated in different solvents (DMSO, CH₃CN and CH₃OH). The results show that compound 1 exhibits a large red shift in both absorption and emission spectra as solvent polarity increases (polarity: DMSO>CH₃CN>CH₃OH), indicating a change in dipole moment of compound 1 upon excitation. Although the emission spectra of compound 1 in CH₃OH are close to it in dimethyl sulfoxide (DMSO), it is revealed that the luminescence behaviour of compound 1 depends not only on the polarity of environment but also on the hydrogen bonding properties of the solvent. Meanwhile, temperature strongly affects the emission spectra of compound 1. Emission peaks of compound 1 were blue shift at 77 K than those at 298 K in both solid state (ca. 142 nm) and solution (ca. 6–23 nm), which was due to the non-radiative transition decreases at low temperature. Moreover, the quantum yield and fluorescence lifetime of compound 1 were also measured, which increased with increasing polarity of solvent, lifetime in DMSO at 298 K (τ₁ = 0.92 μs, τ₂ = 8.71 μs) was the longest one in solvents (298 K: τ₁ = 0.87–0.92 μs, τ₂ = 7.50–8.71 μs; 77 K: τ₁ = 0.72–0.90 μs, τ₂ = 6.88–7.45 μs), which was also shorter than that in solid state (298 K: τ₁ = 1.13 μs, τ₂ = 7.50 μs; 77 K: τ₁ = 0.97 μs, τ₂ = 8.97 μs). This was probably because of the weak polarity environment of compound 1 in solid state.     

Aqua substitution from mononuclear Pt(II) complexes with 2-(pyrazol-1-ylmethyl)quinoline non-leaving ligands

The rates of aqua substitution from [Pt{2-(pyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(H₂Qn)], [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCH₃Qn)], [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]quinoline}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Qn)], and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazol-1-ylmethyl]pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCF₃Py)], with three sulfur donor nucleophiles were studied. The reactions were followed under pseudo-first-order conditions as a function of nucleophile concentration and temperature using a stopped-flow analyzer and UV/visible spectrophotometry. The substitution reactions proceeded sequentially. The second-order rate constants for substituting the aqua ligands in the first substitution step increased in the order Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(H₂Qn) < Pt(dCF₃Py), while that of the second substitution step was Pt(dCH₃Qn) < Pt(dCF₃Qn) < Pt(dCF₃Py) < Pt(H₂Qn). The reactivity trends confirm that the quinoline substructure in the (pyrazolylmethyl)quinoline ligands acts as an apparent donor of electron density toward the metal center rather than being a π-acceptor. Measured pK_a values from spectrophotometric acid–base titrations were Pt(H₂Qn) (pK_a1 = 4.56; pK_a2 = 6.32), Pt(dCH₃Qn) (pK_a1 = 4.88; pK_a2 = 6.31), Pt(dCF₃Qn) (pK_a1 = 4.07; pK_a2 = 6.35), and Pt(dCF₃Py) (pK_a1 = 4.76; pK_a2 = 6.27). The activation parameters from the temperature dependence of the second-order rate constants support an associative mechanism of substitution.     

One-pot synthesis,characterization, DNA binding and enzymatic studies of 4-methyl trans-cinnamate zinc(II)-mixed ligand complexes

Four new zinc(II) complexes formulated as [Zn(L)₂] (1), [Zn(L)₂(phen)] (2), [Zn(L)₂(bipy)H₂O] (3), and [Zn(en)₂(H₂O)₂](L)₂(H₂O)₂ (4), where HL = 4-methyl trans-cinnamic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline, and en = ethylenediamine, have been synthesized and characterized by FT-IR and NMR spectroscopy. Single-crystal XRD revealed distorted square-pyramidal structure for 3 and octahedral for 4. The complexes were screened for DNA interaction via viscommetry and UV–visible spectroscopy. The apparent binding constants were calculated to be 1.18 × 10⁴, 1.26 × 10⁵, 4.64 × 10⁴_, and 1.89 × 10⁴ for 1–4, respectively. The binding propensity to salmon sperm DNA was in the order: K₂ > K₃ > K₄ > K₁. Furthermore, these complexes demonstrated efficient inhibition of alkaline phosphatase, which was attributed to the binding of zinc(II) to the enzyme’s active site.     

Syntheses,structures and luminescent properties of a series of ladder-shaped [Ln2Sr3] heterometal-organic frameworks

A series of Ln^III–Sr^II heterometallic coordination polymers formulated as [Ln₂Sr₃(pda)₆(H₂O)₁₈]·nH₂O (Ln = Pr-1, n = 14; Nd-2, n = 12; Sm-3, n = 11; Eu-4, n = 11; Gd-5, n = 16; Tb-6, n = 13; Dy-7, n = 13) were synthesized via assembly of Ln(NO₃)₃·6H₂O, SrCl₂·6H₂O, pyridine-2,6-dicarboxylic acid (H₂pda) and imidazole (im) in H₂O/C₂H₅OH solution. Single crystal X-ray diffraction revealed that they are isostructural. All of these complexes possess ladder-shaped 1-D chain structures. The luminescent properties of Sm-3, Eu-4, Gd-5, Tb-6 and Dy-7 have been investigated. The solid-state quantum yields and the lifetimes of Eu-4 and Tb-6 are also studied.     

Synthesis,X-ray structural and DFT studies of n-membered ring P,C-chelated complexes of Pd(II) and Pt(II) derived from unsymmetrical phosphorus ylides and application of Pd(II) complexes as catalyst in Suzuki reaction

The phosphonium salts [Ph₂P(CH₂)_nPPh₂CH₂C(O)C₆H₄-m-OMe]Br (n = 1 (S₁) and n = 2 (S₂)) were synthesized in the reaction of bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)ethane (dppe) with 2-bromo-3?-methoxy acetophenone, respectively. Further treatment with NEt₃ gave the phosphorus ylides Ph₂P(CH₂)_nPPh₂C(H)C(O)C₆H₄-m-OMe (n = 1 (Y₁) and n = 2 (Y₂)). These ligands were treated with [MCl₂(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) to give the P, C-chelated complexes, [MCl₂(Ph₂P(CH₂)_nPPh₂C(H)C(O)C₆H₄-m-OMe)] (n = 1, M = Pd (3), Pt (4), and n = 2, M = Pd (5), Pt (6)). These compounds were characterized by elemental analysis, spectroscopic methods, UV–visible, and fluorescence emission spectra. Further, the structures of complexes 3 and 6 were characterized crystallographically. The palladium complexes 3 and 5 proved to be excellent catalysts for the Suzuki reactions of various aryl chlorides. Also, a theoretical study on the structure of complexes 3–6 has been investigated at the BP86/def2-SVP level of theory. The strength and nature of donor?acceptor bonds between the phosphorus ylides (L) and MCl₂ fragment in the [LMCl₂] (M = Pd, Pt, L = Y₁, Y₂) were studied by NBO and energy decomposition analysis (EDA), as well as their natural orbitals for chemical valence variation (EDA-NOCV).     

Synthesis and cation binding properties of fluorescent calix[4]arene derivatives bearing tryptophan units at the lower rim

The fluorescent peptidocalixarenes, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(O-methyl-l-tryptophanylcarbonylmethoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,27-di(O-methyl)-26,28-bis(O-methyl-l-tryptophanylcarbonylmethoxy)calix[4]arene (2), were prepared by introducing tryptophan subunits at a lower calixarene rim. Coordination abilities of 1 and 2 towards Eu(III) and alkali metal cations were studied by spectrophotometric, spectrofluorimetric, conductometric and potentiometric titrations in acetonitrile at 25°C. Rather strong complexation was observed for smaller alkali metal cations Li⁺ and Na⁺ (log K _Li1 >6, log K _Li2 >6, log K _Na1  = 8.25, log K _Na2  = 6.94), and moderate for K⁺ (log K _K1  = 5.09, log K _K2  = 4.09). Larger Rb⁺ and Cs⁺ cations did not fit in the ion binding site of 1 so no complexation was detected, whereas the more flexible ligand 2 accommodated Rb⁺ cation (log K _Rb2  = 3.44). The fluorescence of 1 (λ_ex = 280 nm, λ_em = 340 nm) was remarkably quenched by Eu(III). Stability constant of 1:1 (Eu³⁺:1) complex determined spectrofluorimetrically amounted to log K _Eu1  = 6.16.     

Two tetranuclear Ni(II) complexes from substituted imidazole dicarboxylates: syntheses,structures, thermal and magnetic properties

Two tetranuclear nickel(II) complexes, [Ni₄ (p-BrPhHIDC)₄(py)₄(H₂O)₄]·CH₃OH (p-BrPhH₃IDC = 2-(p-bromophenyl)-1H-imidazole-4,5-dicarboxylic acid) (1) and [Ni₄(p-ClPhHIDC)₄ (CH₃CN)₄(H₂O)₄]·4H₂O (p-ClPhH₃IDC = 2-(p-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid, py = pyridine) (2), have been solvothermally synthesised and structurally characterised. Both compounds consist of similar tetranuclear Ni(II) cores, in which the imidazole dicarboxylate ligands adopt the similar coordination mode. The thermal properties of 1 and 2 have been investigated. Also, it is discovered that there exists antiferromagnetic coupling between the Ni(II) ions in 1 and 2; the best fittings to the experimental magnetic susceptibilities gave J = ? 9.89 cm^? 1 and g = 2.18 for 1, and J = ? 10.54 cm^? 1 and g = 2.14 for 2.     

Theoretical design of a fluorescence sensor with configuration-transformed metal ion recognition of aza-18-crown-6

A novel configuration-transformed metal-ion-recognizing fluorescent molecular sensor was designed. The ground state geometries of the free ligand L(L₁, L₂)and their metal ion complex L/Mⁿ⁺ have been investigated theoretically by density functional theory (DFT). The interaction of L and a series of alkaline earth metal ions have been carried out by the natural bond orbital (NBO) and mayer bond order. The calculated results reveal that the metal ion Sr²⁺ has strong interaction with the free ligand L. The excited states, absorption spectra and fluorescence emission spectra of the free ligands L₁, L₂ and their complexes L/Mⁿ⁺ were performed by the time-density functional theory (TD-DFT). The UV-vis results show that the absorption peak of L₂/Sr²⁺ has an obvious change compared with that of L₂, which indicates that the free ligand L₂ can specifically identify the metal ion Sr²⁺. Furthermore, L₂/Sr²⁺ is superior fluorescent molecular sensor compared with other molecules.     

Discotic derivatives of 6-oxoverdazyl radical

Substitution of each phenyl in 1,3,5-triphenyl-6-oxoverdazyl with three alkoxy groups induces an ordered columnar hexagonal phase (Col_h(o)) below 130°C in 1b[n], while in the alkylsulfanyl analogues 1a[n] additional periodicity along the columns was found rendering the phase a true three-dimensional columnar hexagonal phase (Col_h(3D)) below 60°C. Both series exhibit broad absorption bands in the visible region with maxima at 540 and 610 nm in series 1a[n] and at 486 and 614 nm in series 1b[n]. Unusual reversible thermochromism is observed in series 1b[n], in which the dark green isotropic phase turns red in the discotic phase. Analysis of 1a[8] revealed redox potentials E^0/+1_1/2 = +0.99 V and E^{0/ ?1}_1/2 = –0.45 V vs. saturated calomel electrode (SCE), while the potentials in the alkoxy analogue 1b[8] are shifted cathodically by 0.16 V. Photovoltaic studies of 1a[8] demonstrated hole mobility of μ_h = 1.52 × 10^?3 cm² V^?1 s^?1 in the mesophase with an activation energy E_a = 0.06 ± 0.01 eV. Magnetisation studies of 1a[8] revealed nearly ideal paramagnetic behaviour in either the solid or fluid phase above 200 K and weak antiferromagnetic interactions at low temperatures. In contrast, a noticeable drop of about 4% in μ_eff was observed during the I→Col phase transition in 1b[8], which coincide with the thermochromic effect.     

Structure activity relationship of bergenin,p-hydroxybenzoyl bergenin, 11-O-galloylbergenin as potent antioxidant and urease inhibitor isolated from Bergenia ligulata

Ethanol extract of the aerial parts of Bergenia ligulata was subjected to solvent–solvent separation followed by various chromatographic techniques that lead to isolation of bergenine (1), p-hydroxybenzoyl bergenin (2), 11-O-galloylbergenin (3) and methyl gallate (4) as major constituents. Ethyl acetate fraction showed a dose-dependent urease inhibitory pattern with IC₅₀ value of 54μg/mL. Structures of compounds 1 and 3 were established by XRD and 2, 4 by NMR. All these compounds were subjected to DPPH scavenging activity, reducing power assay and urease inhibitory activity. The EC₅₀ 7.45 ± 0.2 μg/mL and 5.39 ± 0.28 μg/mL values in terms of antioxidant and reducing power, respectively, were less for 3. Compounds 1–3 showed moderate to significant urease inhibitory potential with IC₅₀ 57.1 ± 0.7, IC₅₀ 48.4 ± 0.3 and 38.6 ± 1.5. Antioxidant activities and urease inhibitory potential were investigated and compound 3 was found to be the most active.     

Structural diversity for three Zn(II) coordination polymers from 4-nitrobenzene-1,2-dicarboxylate and bispyridyl ligand

Three Zn(II) complexes, [Zn₂(bpp)₂(FNA)₂]·H₂O (1), [Zn(bpp)(FNA)]·H₂O (2), and Zn₂(bpp)₂(FNA)₂ (3) (bpp = 1,3-bi(4-pyridyl)propane, H₂FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesized and characterized by single-crystal and powder X-ray diffraction methods, IR spectroscopy, TG analyses, elemental analyses, and fluorescent analysis. In 1, the Zn(II) ions are linked by FNA anions and bpp into 2-D layers. The Zn(II) ions in 2 are bridged by FNA anions into chiral chains, which are interlinked by bpp into 3-D metal–organic framework with (6⁵·8) CdS topology. Complex 3 features 1-D zigzag chains, which are interconnected by bpp ligands to give a 3-D framework with (6·7⁴·8)(6⁴·7·8) topology. Complexes 2 and 3 exhibit significant ferroelectric behavior (for 2 remnant polarization Pr = 0.050 μC cm^?2, coercive field Ec = 1.13 kV cm^?1, saturation of the spontaneous polarization Ps = 0.239 μC cm^?2; for 3 Pr = 0.192 μC cm^?2, Ec = 4.64 kV cm^?1, Ps = 0.298 μC cm^?2).     

Copper(II) halide salts and complexes of 4-amino-2-fluoropyridine: synthesis,structure and magnetic properties

Reaction of 4-amino-2-fluoropyridine (2-F-4-AP) with copper halides produced the neutral coordination complexes: (2-F-4-AP)₂CuX₂ (X = Cl(1), Br(2)). 1 crystallizes in the orthorhombic space group Pccn in a distorted square planar geometry. Magnetic susceptibility data were fit to the uniform chain Heisenberg model resulting in C = 0.439(6)emu-K/mole-Oe and J = ?28(1) K. 2 crystallizes in the monoclinic space group C2/m and is closer to distorted tetrahedral. Intermolecular Br?Cu contacts generate a square layer. Magnetic data show very weak ferromagnetic interactions [C = 0.42(1)emu-K/mol-Oe, J = 0.71(2) K]. Similarly, reaction of 2-F-4-AP with copper halides and aqueous HX in alcohol solvents produced the salts (2-F-4-APH)₂CuX₄ (X = Cl(3), Br(4)). 3 crystallizes in the triclinic space group P-1. Crystal packing reveals short Cl?Cl contacts which generate a structural ladder. However, analysis of the magnetic data suggests that only the rails of the ladder produce a viable magnetic superexchange pathway; the uniform Heisenberg chain model provides C = 0.449(1)emu-K/mol-Oe and J = -6.9(1) K. 4 is isostructural and is also best fit by a chain model [J = ?2.7(4) K]. The brominated complex (2-F-3-Br-4-APH)₂CuBr₄·2H₂O, 5, (2-F-3-Br-4-APH = 4-amino-3-bromo-2-fluoropyridinium) was serendipitously produced as a byproduct of the synthesis of 4 and was characterized by single-crystal X-ray diffraction.     

Synthesis,characterization, and magnetochemical properties of two Mn4 clusters derived from 2-pyridinecarboxaldehyde Schiff base ligands

Two tetranuclear manganese complexes, [Mn₄(L¹)₆](ClO₄)₂?2.75H₂O (1) [HL¹ = 4-methyl-2-((pyridin-2-ylmethylene)amino)phenol] and [Mn₄(L²)₄(NO₃)₃(OH)]?pz?3H₂O (2) [HL² = (1H-pyrazol-1-yl)(pyridin-2-yl)methanol, pz = pyrazole], have been synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and magnetic measurements. The structural analysis revealed that the central manganese ion is linked with three apical manganese ions through six phenoxo-bridges creating a Mn₄O₆ core for 1; 2 has a cubane-like topology with the Mn(II) ions and the deprotonated oxygens from L² alternatively occupying vertices. The magnetic studies indicated a weak ferromagnetic coupling interaction (J = 0.48 ± 0.087 cm^?1, g = 2.00, θ = ?0.78 K) for 1 and a weak antiferromagnetic spin-exchange interaction (J₁ = ?0.50 ± 0.075 cm^?1, J₂ = ?0.13 ± 0.082 cm^?1, g = 1.98) between Mn(II) ions for 2. The magnetostructural correlations of the two Mn₄ clusters have been discussed tentatively.     

Copper(I)-1,1,1-tris(diphenylphosphinomethyl)ethane complexes with different coordination modes tuned by auxiliary ligands and their spectroscopic properties

Three mono-, bi- and tetranuclear copper(I) complexes, [Cu(phen)(triphos-O)]BF₄ (1) (phen = 1,10-phenanthroline, triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane), [Cu₂(bipy)(triphos)₂](BF₄)₂ (2) (bipy = 4,4′-bipyridine), and [Cu₄(MeOC^N^N)₄(triphos)₂(bipy)](BF₄)₄ (3) (MeOC^N^N = 6-(4-methoxyphenyl)-2,2′-bipyridine), have been synthesized and characterized by NMR spectroscopy, electrospray ionization, and matrix-assisted laser desorption ionization time-of-flight mass spectrometries, elemental analysis, and X-ray crystal analysis. The crystal structure investigation revealed the copper ions of the complexes have pseudo-tetrahedral coordination geometry. The electronic absorption spectra of 1, 2, and 3 contain low-energy bands at 350–500 and 400–650 nm, which are assigned to d(Cu) → π*(phen or bipy) and a mixture of d(Cu) → π*(MeOC^N^N) and d(Cu) → π*(bipy) transitions, respectively. Complex 2 displays a strong, long-lived solid-state emission with a maximum at 555 nm and lifetime of 13.6 μs at room temperature. Photoinduced electron-transfer properties of 2 and 3 involving nanosecond time-resolved absorption spectroscopy and electron spin resonance techniques were studied.     

Antileishmanial diterpenoid alkaloids from Aconitum spicatum (Bruhl) Stapf

The crude extracts of tubers of Aconitum spicatum (Bruhl) Stapf were investigated for in vitro antileishmanial activity against Leishmania major. The dichloromethane extract at pH 2.5 showed antileishmanial activity with IC₅₀ value of 27.10 ± 0.0 μg/mL. Chromatographic purification of the dichloromethane extract led to isolation of three C-19 norditerpenoid alkaloids indaconitine (1), chasmaconitine (2) and ludaconitine (3). Compounds 3 and 2 showed antileishmanial activity with IC₅₀ = 36.10 ± 3.4 and 56.30 ± 2.1 μg/mL, respectively. Compound 1 was less effective (IC₅₀ > 100 μg/mL). The cytotoxicity of compounds 1, 2 and 3 studied against MCF7, HeLa and PC3 cancer cell lines and 3T3 normal fibroblast cell line did not show cytotoxicity at 30 μM.     

Hepatoprotective and neuroprotective tocopherol analogues isolated from the peels of Citrus unshiu Marcovich

Three tocopherol analogues methoxytocopherol (1), α-tocopherol (2) and γ-tocopherol (3) were isolated from the peels of Citrus unshiu Marcovich. The protective effects of the isolated compounds against tert-butyl hydroperoxide-induced hepatotoxicity in human liver-derived HepG2 cells and glutamate-induced oxidative stress in HT22-immortalised hippocampal cells were evaluated. Compounds 1–3 were significantly protective in HepG2 cells with EC₅₀ values of 21.22 ± 2.01, 25.21 ± 2.11 and 25.25 ± 1.21 μM, respectively, and in HT22 cells, compounds 1–3 had EC₅₀ values of 20.62 ± 1.36, 6.44 ± 1.65 and 9.52 ± 1.54 μM, respectively.     

A wine red copper(II) complex of a tetradentate nitrogen donor showing two-electron oxidation. Generation of a copper(II)-phosphine bond

Using the 1 : 2 condensate of benzil and 2-hydrazinopyridine as the ligand LH₂ (H: dissociable NH proton), the red complex Cu(LH₂)(ClO₄)₂ (1) was synthesized. The ligand also afforded the orange [Zn(LH₂)(OH₂)₂](ClO₄)₂ (2). The X-ray crystal structures of the ligand, 1 and 2 have been determined. The metals in 1 and 2 have octahedral N₄O₂ environments. 1 is paramagnetic with μ_eff of one unpaired electron (1.63 μ_B and displays an axial EPR spectrum in the solid state with <g> = 2.07, characteristic of a (d_x2_?y2)¹ ground state (g_|| > g_⊥; A_|| = 16 mT). In cyclic voltammetry, 1 displays a two-electron oxidation around 0.9 V versus NHE. The two-electron oxidized (coulometrically) solution of 1 (golden yellow) gives an EPR spectrum with <g> = 2.17 and g_|| < g_⊥. The reaction of PPh₃ with 1 yields the orange complex [Cu(LH₂)(PPh₃)](ClO₄)₂ (4). With the assumed chemical formula, the effective magnetization of 4 corresponds to one electron. Its EPR spectrum in the solid state is isotropic with g = 2.07. This g value yields a theoretical μ_eff of 1.80 μ_B at 298 K from Curie’s law, which matches very well with the experimental value of 1.89 μ_B at room temperature. Since single crystals of 4 could not be obtained, DFT calculations at the UBP86/6–311G(2d,p) level have been carried out and indicate that the cation in 4 is square pyramidal with the phosphine at the apex. The ease of the oxidation of the metal in 1 leads to the stabilization of the rare Cu(II)-P bond in 4.     

Effect of the lanthanoid-size on the structure of a series of lanthanoid-anilato 2-D lattices*

Abstract

We report the synthesis and characterization of a series of Ln-based bromoanilato 2-D lattices with dimethyl sulfoxide (DMSO): [Ln₂(C₆O₄Br₂)₃(DMSO)_n]·2DMSO·mH₂O with n = 6 and m = 0 for Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6) and Gd (7); n = 4 and m = 2 for Ln = Tb (8), Dy (9), Ho (10), Er (11), Tm (12) and Yb (13) (C₆O₄Br₂^2? = 3,6-dibromo-2,5-dihydroxy-1,4-benzoquinone = bromoanilato). The X-ray analysis shows that the largest Ln(III) ions (La-Gd, 1-7) crystallize in the monoclinic P21/n space group (phase I), whereas the smaller Ln(III) ions (Tb–Yb, 8–13) crystallize in the triclinic P-1 space group (phase II). Both phases present a (6,3)-2-D topology but show important differences derived from the different coordination number of the Ln(III) in both phases. In phase I, the Ln(III) ions are nine-coordinate with a tri-capped trigonal prism geometry and rectangular cavities with no solvent molecules. In phase II, the Ln(III) ions are eight-coordinate with a triangular dodecahedral geometry and distorted hexagonal cavities having two water molecules. These differences are due to the lanthanoid contraction. The magnetic properties show that the Ln(III) ions are isolated and do not present any noticeable magnetic interactions as expected for bromoanilato bridges and Ln(III) ions.     

New cytotoxic isoprenoid derivatives from the Red Sea soft coral Sarcophyton glaucum

Chemical investigation of the soft coral Sarcophyton glaucum collected from the Red Sea led to isolation of 11 isoprenoidal metabolites (1–11). A new sesquiterpenoid, 6-oxo-germacra-4(15),8,11-triene (1), a new natural cembranoid, sarcophinediol, along with two known sesquiterpenoids (2 and 3) and seven known cembranoids (5–11) was obtained. The structures of the compounds were established based on their NMR, MS, IR and UV spectral data. All compounds were evaluated for their cytotoxicity employing three cancer cell lines (HepG2, MCF-7 and HCT116). Compounds 4 and 6 showed significant cytotoxicity towards HepG2 with IC₅₀ values of 18.8 ± 0.07 and 19.9 ± 0.02 μM; respectively. Compounds 5–7 exhibited potent cytotoxicity against MCF-7 cells with IC₅₀ values of 9.9 ± 0.03, 2.4 ± 0.04 and 3.2 ± 0.02 μM, respectively. Compounds 1, 4 and 5 showed significant activities towards HCT116 cells with IC₅₀ values of 29.4 ± 0.03, 19.4 ± 0.02 and 25.8 ± 0.03 μM, respectively.