Synthesis, structural characterization, and reactivity of organolanthanides derived from a new chiral ligand (S)-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl

Condensation of (S)-2-amino-2′-hydroxy-1,1′-binaphthyl with 1 equiv. of pyrrole-2-carboxaldehyde in toluene in the presence of molecular sieves at 70 °C gives (S)-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl (1H₂) in 90% yield. Deprotonation of 1H₂ with NaH in THF, followed by reaction with LnCl₃ in THF gives, after recrystallization from a toluene or benzene solution, dinuclear complexes (1)₃Y₂(thf)₂ · 3C₇H₈ (3 · 3C₇H₈) and (1)₃Yb₂(thf)₂ · 3C₆H₆ (4 · 3C₆H₆), respectively, in good yields. Treatment of 1H₂ with Ln[N(SiMe₃)₂]₃ in toluene under reflux, followed by recrystallization from a benzene solution gives the dimeric amido complexes {1-LnN(SiMe₃)₂}₂ · 2C₆H₆ (Ln = Y (5 · 2C₆H₆), Yb (6 · 2C₆H₆)) in good yields. All compounds have been characterized by various spectroscopic techniques, elemental analyses and X-ray diffraction analyses. Complexes 5 and 6 are active catalysts for the polymerization of methyl methacrylate (MMA) in toluene, affording syn-rich poly-(MMA)s.     

A series of silver coordination polymers constructed from flexible bis(benzimidazole) ligands and different carboxylates

In this article, eight new silver coordination polymers constructed from two structurally related ligands, 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole) (bbmb) and 1,1′-(1,4-butanediyl)bis(2-ethylbenzimedazole) (bbeb), have been synthesized: [Ag(L1)(bbmb)]·C₂H₅OH·H₂O (1), [Ag(L2)(bbmb)]·C₂H₅OH (2), [Ag(L3)(bbmb)] (3), [Ag₂(L4)(bbmb)₂]·C₂H₅OH (4), [Ag(L2)(bbeb)]·C₂H₅OH (5), [Ag(L5)(bbeb)]·CH₃OH (6), [Ag₂(L6)₂(bbeb)]·H₂O (7), and [Ag₂(L7)(bbeb)₂]·4(H₂O) (8), where L1 = benzoate anion, L2 = p-methoxybenzoate anion, L3 = 2-amino-benzoate anion, L4 = oxalate anion, L5 = cinnamate ainon, L6 = 3-amino-benzoate anion, and L7 = fumaric anion. In 1-3, 5 and 6, the bidentate N-donor ligands (bbmb and bbeb) in trans conformations bridge neighboring silver centers to form 1D single chain structures. The carboxylate anions are attached on both sides of the chains. Moreover, 1 and 3 are extended into 2D layers, while 2 and 6 are extended into 3D frameworks through π-π interactions. In 4, the bbmb ligands bridge adjacent Ag(I) centers to form -Ag-bbmb-Ag- chains, which are further connected by L4 anions to form a 2D layer. The resulting layers are extended into 3D frameworks through strong π-π interactions. In 7, the N-donor ligands (bbeb) in trans conformations bridge two silver centers to generate a [Ag₂(bbeb)]²⁺ unit. The adjacent [Ag₂(bbeb)]²⁺ units are further connected via the L6 anions to form a 1D ladder chain. Moreover, the structure of compound 7 is extended into a 3D framework through hydrogen bonding and π-π interactions. In 8, two Ag(I) cations are bridged by two bbeb ligands in cis conformations to form a [Ag₂(bbeb)₂]²⁺ ring, which are further linked by L7 anions to generate a 1D string chain. Furthermore, the hydrogen bonding and π-π interactions link L7 anions to form a 2D supramolecular sheet. Additionally, the luminescent properties of these compounds were also studied.     

Magneto-structural study on a series of rhenium(IV) complexes containing biimH2, pyim and bipy ligands

Three rhenium(IV) mononuclear compounds of formulae [ReCl₄(biimH₂)] · 2DMF (1), [ReCl₄(pyim)] · DMF (2) and [ReCl₄(bipy)] (3) (biimH₂ = 2,2′-biimidazole, pyim = 2-(2′-pyridyl)imidazole, bipy = 2,2′-bipyridine and DMF = N,N-dimethylformamide) have been prepared and characterized. The crystal structure of 2 was determined by single crystal X-ray diffraction. Compound 2 crystallizes in the monoclinic system with P2₁/c as space group. The rhenium atom is six-coordinated by four Cl atoms and two nitrogen atoms from a bidentate pyim ligand [average values of Re–Cl and Re–N bonds lengths being 2.330(2) and 2.117(4) Å, respectively]. The magnetic properties were investigated from susceptibility measurements performed on polycrystalline samples of 1–3 in the temperature range 1.9–300 K. The magnetic behaviour found is typical of antiferromagnetically coupled systems, and they exhibit susceptibility maxima at 2.8 (1 and 2) and 5.6 K (3). Short Re^IV–Cl?Cl–Re^IV contacts through space account for the antiferromagnetic behaviour observed.     

Enantioselective alkynylation to aldimines catalyzed by chiral 2,2′-di(2-aminoaryloxy)-1,1′-binaphthyl-copper(I) complexes

The enantioselective alkynylation of aldimines with terminal acetylenes catalyzed by chiral Cu(I) complexes with (R)-2,2′-di(2-aminoaryloxy)-1,1′-binaphthyl ligands (7) was examined. Chiral C₂-symmetric N,N-ligands 7, which have primary aniline moieties, were readily prepared from inexpensive (R)-1,1′-binaphthol (BINOL) as a chiral source. In particular, the reaction of N-benzylidenebenzeneamine 1a with phenylacetylene 2a proceeded smoothly in the presence of 5 mol % of (CuOTf)₂·C₆H₅CH₃ and 10 mol % of (R)-7d at room temperature for 24 h, and the corresponding propargylamine 3a was obtained with up to 82% ee.     

Rational design and syntheses of 0-D, 1-D, and 2-D metal-organic frameworks (MOFs) from ferrocenedicarboxylate tetrametallic macrocyclic building units and subsidiary ligands

We have designed and synthesized three new metal-1,1′-ferrocenedicarboxylate complexes containing tetrametallic macrocyclic building units, namely, [Cd₂(η²-O₂CFcCO₂-η²)₂(phen)₂(H₂O)₂] · 4CH₃OH (1) (Fc = (η⁵-C₅H₄)Fe(C₅H₄-η⁵), phen = 1,10-phenanthroline), {[Cd(η²-O₂CFcCO₂)(pebbm)(H₂O)] · 2H₂O}_n (2) (pebbm = 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole) and {[Cd(η²-O₂CFcCO₂-η²)(prbbm)(H₂O)] · 3H₂O}_n (3) (prbbm = 1,1′-(1,3-propanediyl)bis-1H-benzimidazole). Compound 1 is a 0-D discrete tetrametallic macrocyclic framework. Compound 2 features an infinite 1-D ribbon of rings structure constructed by the subsidiary ligands pebbm connecting tetrametallic macrocyclic building units. For 3, its tetrametallic macrocyclic building units are linked by the subsidiary ligands prbbm to form a 2-D network structure. The structural features of these complexes indicate that the ferrocenedicarboxylate tetrametallic macrocycle can be used as a successful molecular building unit and the shapes and conformational flexibility of subsidiary ligands play a crucial role in the manipulation of the configuration of the resultant MOFs. Their fluorescence spectra in solid state at room temperature suggest that the fluorescence emissions of 1-3 are ruled by 1,1′-ferrocenedicarboxylate ligand.     

A series of metal-organic frameworks constructed with arenesulfonates and 4,4′-bipy ligands

Five transition metal compounds containing arenesulfonates and 4,4′-bipy ligands, namely [Zn₂(N,N′-4,4′-bipy)(N-4,4′-bipy)₂(H₂O)₈](bpds)₂ · 5H₂O (1), [Ag₂(N,N′-4,4′-bipy)₂(bpds)] (2), [Cd(N,N′-4,4′-bipy)(H₂O)₄]₂(4-abs)₄ · 5H₂O (3), [Cu(N,N′-4,4′-bipy) (O-bs)₂(H₂O)₂] · 4H₂O (4), and [Zn(N,N′-4,4′-bipy)₂(H₂O)₂](4,4′-bipy)(bs)₂ · 4H₂O (5) (4,4′-bipy = 4,4′-bipyridine, bpds = 4,4′-biphenyldisulfonate, 4-abs = 4-aminobenzenesulfonate, bs = benzenesulfonate), have been synthesized and characterized by X-ray single crystal diffraction, elemental analyses and TG analyses, in order to investigate the coordination chemistry of arenesulfonates and 4,4-bipy, as well as to construct novel coordination frameworks via mixed-ligand strategy. Compounds 2, 4 and 5 could be obtained via hydrothermal or aqueous reactions. Compound 1 forms a binuclear octahedral metal complex. Compounds 2–4 form polymeric chains. Compound 5 consists of 2D square grids with one intercalated 4,4′-bipy molecule. Weak Ag–Ag interactions are observed in compound 2. These complexes show great structural varieties and there are three different coordination modes observed for both the 4,4′-bipy and the sulfonate ligands.     

The cyclopalladation reaction of 2-phenylaniline revisited

2-Phenylaniline reacted with Pd(OAc)₂ in toluene at room temperature for 24 h in a one-to-one molar ratio and with the system PdCl₂, NaCl and NaOAc in a 1 (2-phenylaniline):1 (PdCl₂):2 (NaCl):1 (NaOAc) molar ratio in methanol at room temperature for one week to give the dinuclear cyclopalladated compounds (μ-X)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ [1a (X = OAc) and 1b (X = Cl)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)₂ in one-to-one molar ratio in acid acetic at 60 °C for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ (1c) in moderate yield. A parallel treatment, but using monodeuterated acetic acid (DOAc) as solvent in the cyclopalladation reaction, allowed isolation of a mixture of compounds 1c, 1c_d1 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄](μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃] and 1c_d2 (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃}]₂ in moderate yield and with a deuterium content of ca. 60%. 1a and 1b reacted with pyridine and PPh₃ affording the mononuclear cyclopalladated compounds [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(X)(L)] [2a (X = OAc, L = py), 2b (X = Cl, L = py), 3a (X = OAc, L = PPh₃) and 3b (X = Cl, L = PPh₃)] in a yield from moderate to high. Furthermore, 1a reacted with Na(acac) · H₂O to give the mononuclear cyclopalladated compound 4 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(acac)] in moderate yield. ¹H NMR studies in CDCl₃ solution of 2a, 2b, 3a, 3b and 4 showed that 2a and 3a presented an intramolecular hydrogen bond between the acetato ligand and the amino group, and were involved in a dynamic equilibrium with water present in the CDCl₃ solvent; and that the enantiomeric molecules of 2b and 4 were in a fast exchange at room temperature, while they were in a slow exchange for 2a, 3a and 3b. The X-ray crystal structures of 3b and 4 were determined. 3b crystallized in the triclinic space group with a = 9.9170(10), b = 10.4750(10), c = 12.0890(10) Å, α = 98.610(10)°, β = 94.034(10)° and γ = 99.000(10)° and 4 in the monoclinic space group P2₁/a with a = 11.5900(10), b = 11.2730(10), c = 12.2150(10) Å, α = 90°, β = 107.6560(10)° and γ = 90°.     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

R-phenyldicarboxyl (R = H, NO2 and COOH) modular effect on Ni(II) coordination polymers incorporated with a versatile connector 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole

Based on the versatile ligand 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (3,4′-Hbpt) (1), a series of coordination compounds [Ni(3,4′-Hbpt)(ip)] (2), [Ni(3,4′-Hbpt)₂(tp)(H₂O)₂] (3), [Ni₂(3,4′-Hbpt)(5-NO₂-ip)₂(H₂O)₄] (4) and [Ni(3,4′-Hbpt)(pm)_0.5(H₂O)₃]·2H₂O (5) have been hydrothermally constructed through R-phenyldicarboxyl (R = H, NO₂ and COOH) intervention effect (ip = isophthalic anion, tp = terephthalic anion, 5-NO₂-ip = 5-NO₂-isophthalic anion, pm = pyromellitic anion). Structural analysis reveals that 3,4′-Hbpt adopts μ-N_py, N_py coordination modes in two typical conformations in these target coordination compounds. In cooperation with the auxiliary ligands benzenedicarboxylate connectors, a variety of Ni(II) coordination networks such as 2-D layer with (4, 4) topology (2) 1-D chain (3), honeycomb (4) and 2-D helical chains (5) have been assembled. Theoretical calculation based on density functional theory (DFT) for ligand (1) is also employed to explicate the stability of the different conformations. Moreover, thermal stability of these crystalline materials is explored by TG-DTG.     

Dinuclear copper(II) perchlorate complexes with 6-(benzylamino)purine derivatives: Synthesis,X-ray structure,magnetism and antiradical activity

The reactions of Cu(ClO₄)₂·6H₂O with 6-(benzylamino)purine derivatives in a stoichiometric 1:2 metal-to-ligand ratio led to the formation of penta-coordinated dinuclear complexes of the formula [Cu₂(μ-L^1–8)₄(ClO₄)₂](ClO₄)₂·nsolv, where L¹ = 6-(2-fluorobenzylamino)purine (complex 1), L² = 6-(3-fluorobenzylamino)purine (2), L³ = 6-(4-fluorobenzylamino)purine (3), L⁴ = 6-(2-chlorobenzylamino)purine (4), L⁵ = 6-(3-chlorobenzylamino)purine (5), L⁶ = 6-(4-chlorobenzylamino)purine (6), L⁷ = 6-(3-methoxybenzylamino)purine (7) and L⁸ = 6-(4-methoxybenzylamino)purine (8); n = 0–4 and solv = H₂O, EtOH or MeOH. All the complexes have been fully characterized by elemental analysis, FTIR, UV–Vis and EPR spectroscopy, and by magnetic and conductivity measurements. Variable temperature (80–300 K) magnetic susceptibility data of 1–8 showed the presence of a strong antiferromagnetic exchange interaction between two Cu(II) (S = 1/2) atoms with J ranging from −150.0(1) to −160.3(2) cm⁻¹. The compound 6·4EtOH·H₂O was structurally characterized by single crystal X-ray analysis. The Cu?Cu separation has been found to be 2.9092(8) Å. The antiradical activity of the prepared compounds was tested by in vitro SOD-mimic assay with IC₅₀ in the range 8.67–41.45 μM. The results of an in vivo antidiabetic activity assay were inconclusive and the glycaemia in pre-treated animals did not differ significantly from the positive control.     

2,2′-Bipyrimidine transition metal complexes: Synthesis, reaction chemistry and solid state structures

2,2′-Bipyrimidine metal complexes with Ti, Mo, Fe, Ru, Pt, Ag, and Cu transition metal atoms have been synthesized and structurally characterized. These molecules were prepared by following synthesis methodologies. The reaction of 2,2′-bipyrimidine (1; bipym) with {[Ti](μ-σ,π-CCSiMe₃)₂}AgOTf ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti, OTf = OSO₂CF₃) (2) in a 1:1 molar ratio gave [{[Ti](μ-σ,π-CCSiMe₃)₂}Ag(bipym)]OTf (3) which on further treatment with another equivalent of 2 produced [({[Ti](μ-σ,π-CCSiMe₃)₂}Ag)₂(μ-1,2,3,4-bipym)](OTf)₂ (4). As consequence thereof, the coordination number of Ag(I) was changed from 3 to 4. A platinum-bipym complex with two acetylide substituents was accessible by the gradual reaction of 1 with K₂[PtCl₄] (5) and two equivalents of HCCR (7a, R = SiMe₃; 7b, R = Fc; 7c, R = Rc; Fc = (η⁵-C₅H₄)(η⁵-C₅H₅)Fe; Rc = (η⁵-C₅H₄)(η⁵-C₅H₅)Ru) in di-iso-propylamine and in presence of [CuI]. Originating from cis-[(bipym)Pt(CCR)₂] (8a, R = SiMe₃; 8b, R = Fc; 8c, R = Rc) diverse multinuclear complexes with two, three or four different transition metals could be obtained. These are: [((CO)₄Mo)(μ-1,2,3,4-bipym)Pt(CCFc)₂] (10), [(AgClO₄)(μ-1,2,3,4-bipym){[Pt(μ-σ,π-CCFc)₂]AgOClO₃}] (12), [(McCC)₂Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe₃)₂}M)]X (15a, Mc = Fc, M = Cu, X = PF₆; 15b, Mc = Rc, M = Cu, X = PF₆; 15c, Mc = Fc, M = Ag, X = ClO₄), and [(McCC)₂Pt(μ-1,2,3,4-bipym)PtCl₂] (17). Like other organometallic Pt-Ag tweezer complexes, compound 12 decomposed to give FcCC-CCFc (13). During prolonged stirring of 15a and 15b, respectively, [(McCC)₂Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe₃)(μ-σ,π-CCH)}M)]X (15′a, M = Cu, X = PF₆; 15′b, M = Cu, X = PF₆) was formed.The structures of 8b, 8c, 15a′, and 15b′ in the solid state are reported. All complexes exhibit the anticipated planar dinuclear Pt-M structure (M = Pt, Cu, Ag) with the 2,2′-bipyrimidine unit in a μ-1,2,3,4-bridging mode.Electrochemical investigations were carried out with 8a, 8b, and 8c and show that no significant influence of R on the bipym redox potentials exists. The typical redox behavior for the bipym, ferrocene, ruthenocene units and platinum were observed.     

Synthetic,structural and spectroscopic studies of copper(II) complexes derived from the combination of the succinamate(−1) ligand with aromatic N,N′-chelates

The use of succinamic acid (H₂sucm)/N,N′-chelate (2,2′-bipyridine, bpy; 4,4′-dimethyl-2,2′-bipyridine, dmbpy; 1,10-phenanthroline, phen) ‘ligand blends’ in CuX₂·yH₂O (X = NO₃, y = 3; X = Cl, y = 0) chemistry has yielded the new complexes [Cu₂(Hsucm)₃(bpy)₂](NO₃)·0.5MeOH (1·0.5MeOH), [Cu₂(Hsucm)(OH)Cl(bpy)₂](OH)·3.6H₂O (5·3.6H₂O) and [Cu₂(Hsucm)₂Cl₂(phen)₂] (6). The succinamate(−1) ion behaves as a carboxylate ligand and exists in two different coordination modes in the structures of the above complexes, i.e., the common syn, syn μ₂-κO:κO′ in 1, 5 and 6, and the μ₂-κ²O:κO′ in 1. The primary amide group of Hsucm⁻ remains uncoordinated and participates in intermolecular hydrogen bonding interactions leading to 1D, 2D and 3D networks. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the Hsucm⁻ ligands.     

Synthesis and properties of novel 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates

Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac₂O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The ¹³C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG^‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol⁻¹ by the variable temperature ¹H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF₄⁻ and 12a-c·BF₄⁻) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF₄⁻) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF₄/Ac₂O afforded two kinds of novel products 11a-c·BF₄⁻ and 12a,c·BF₄⁻ in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF₄⁻ and 12a-c·BF₄⁻ observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF₄⁻ and 12a-c·BF₄⁻ were studied, and structural characterization of 11c·BF₄⁻ based on the X-ray crystal analysis and MO calculation was also performed.     

Crystal structures and properties of four coordination polymers constructed from flexible pamoic acid

Four novel coordination polymers constructed from flexible pamoic acid, namely [Co(pam)(4,4′-bipy)]_n·nH₂O (1), [Ni(pam)(4,4′-bipy)(H₂O)₂]_n·2nCH₃CN (2), [Cd(pam)(py)₂]_n·npy (3) and [Mn₂(pam)₂(py)₆(H₂O)₂]_n·2npy (4), (H₂pam = pamoic acid, 4,4′-bipy = 4,4′-bipyridine, py = pyridine), have been synthesized and characterized by elemental analysis, infrared spectra and X-ray crystallography. Complex 1 is a 2-D coordination polymer constructed from chelating bis-bidentate pam and 4,4′-bipyridine bridging ligands. Complex 2 is a 2-D coordination polymer assembled by bis-monodentate pam and 4,4′-bipyridine, where acetonitrile is filled in the rectangle channels. Both 2-D coordination polymers display undulated (4,4) grid layers as sql topology. Complex 3 displays a 1-D polymeric chain using chelating bis-bidentate pam as bridging ligand. Complex 4 exhibits an interesting bis-monodentate pam-Mn(II) 1-D polymeric chain, in which exist two-type six-coordinated manganese centers. Mn(1) is bound to four pyridine ligands, whereas Mn(2) is combined to two pyridine and two H₂O molecules. Their thermal stabilities have been investigated. Cadmium complex 3 displays strong green luminescence with emission maximum at 543 nm.     

Application and details of photoinduced oxidative cyclization of 5-(4′,9′-methanocycloundeca-2′,4′,6′,8′,10′-pentaenylidene)pyrimidine-2,4,6(1,3,5H)-triones and related compounds

As novel methodology for synthesizing the furan ring, a photoinduced oxidative cyclization of 5-(4′,9′-methanocycloundeca-2′,4′,6′,8′,10′-pentaenylidene)pyrimidine-2,4,6(1,3,5H)-triones (7a-c) and related compounds 9a-c was accomplished to give 5,10-methanocycloundeca[4,5]furo[2,3-d]pyrimidine-2,4(1,3H)-dionylium tetrafluoroborates (8a-c⁺·BF₄⁻) and related compounds 2a-c⁺·BF₄⁻, respectively. In the photoinduced oxidative cyclization, the molecular oxygen in air is used as oxidant and the reaction proceeds under mild conditions to give desired products without byproducts, and thus, it is interesting from the viewpoint of the green chemistry. On the reactions of the mono-substituted derivatives 7d,e and 9e,f, the selectivity of the photoinduced cyclizations were reversed as compared with those of the DDQ-promoted oxidative cyclizations. By the NMR monitoring of the reactions of 7a and deuterated compound 7a-D₂ under degassed conditions, the details of the reaction pathway were clarified and rationalized on the basis of the MO calculation by the 6-31G^∗ basis set of the MP2 levels as well.     

A pyrazolyl-terminated 2,2′:6′,2″-terpyridine ligand: Iron(II), ruthenium(II) and palladium(II) complexes of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine

The preparation of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine (2) under acidic conditions results in the formation of the salts [H₂2][MeOSO₃]₂ and [H₂2][EtOSO₃]₂, treatment of which with base leads to neutral 2. The structure of [H₂2][EtOSO₃]₂ · H₂O has been established by single crystal X-ray diffraction. The complexes [Fe(2)₂][PF₆]₂ and [Ru(2)₂][PF₆]₂ have been prepared and characterized, and the single crystal structure determination of [Ru(2)₂][PF₆]₂ is reported; [Fe(2)₂][PF₆]₂ is isostructural with [Ru(2)₂][PF₆]₂. Treatment of [Fe(2)₂]²⁺ with PdCl₂ produces [Pd(2)Cl]⁺, isolated and structurally characterized as the hexafluoridophosphate salt, illustrating that metal exchange within the tpy-binding domain occurs in preference to palladium(II) coordination by the N-donor atom of the pendant 3,5-dimethylpyrazol-1-yl unit in 2. [Pd(2)Cl]²⁺ can also be prepared from PdCl₂ and [H₂2][MeOSO₃]₂ in refluxing methanol.     

N,N-polymethylene-bisadenine complexes with d metal ions

The reaction of N⁹,N^9′-(tri or tetramethylene)-bisadenines (Ade₂C_x; x = 3 or 4) in HCl 2 M at 50 °C with MCl₂ · 2H₂O [M = Zn(II), Cd(II)] yields outer sphere compounds like the previously described [(H-Ade)₂C₃][ZnCl₄] · H₂O (3) and [(H-Ade)₂C₃]₂[Cd₂Cl₈(H₂O)₂] · 4H₂O (4) for Ade₂C₃ and the new {[(H-Ade)₂C₄][Cd₂Cl₆(H₂O)₂] · 2H₂O}_n (5) for Ade₂C₄. On the other hand, only in case of Zn(II) complexes by changing [HCl] to 0.1 M, the inner sphere compounds [H-(Ade)₂C₃(ZnCl₃)] (6) and [H-(Ade)₂C₄(ZnCl₃)] · 1.5H₂O (7) are obtained. X-ray diffraction study of compound 6, which represents the first inner sphere complex with a N⁹,N^9′-bisadenine, shows a zwitterionic form with one adenine ring protonated at N(1) while the other ring is coordinated via N(7) to a ZnCl₃ moiety as in other alkyl-adenine derivatives. In addition, with Ade₂C₄, is also possible to obtain another inner sphere complex: [(H-Ade)₂C₄(ZnCl₃)₂] · 3H₂O (8).     

Preparation,crystal structures and spectroscopic characterization of oxalate copper(II) complexes containing the nitrogen ligands 4,4′-dimethyl-2,2′-bipyridine and di(2-pyridyl)sulfide

The preparation, crystal structures and spectroscopic characterization of four oxalate copper(II) complexes containing the 4,4′-dimethyl-2,2′-bipyridine (Mebpy) or di(2-pyridyl)sulfide (DPS) nitrogen ligands namely [μ-(ox){Cu(Mebpy)(NO₃)(H₂O)}₂] (1), [μ-(ox){Cu(Mebpy)(ClO₄)(H₂O)}₂] (2), [μ-(ox){Cu(DPS)(H₂O)}₂](ClO₄)₂ (3) and [Cu(DPS)(ox)(H₂O)] · 2H₂O (4) are described. X-ray diffraction measurements have shown that complexes 1–3 are binuclear, in which the oxalate anion bridges two Cu(II) centers, while the complex (4) is mononuclear and the oxalate anion adopts the terminal bidentate chelating coordination mode. In 1 and 2 the Cu(II) sites display a distorted octahedral geometry (4+2 environment) and in compounds 3 and 4 the Cu(II) centers exhibit a slightly distorted square pyramidal geometry. In addition, complexes 1 and 2 present a 2D supramolecular arrangement through hydrogen bonds between coordination water molecules and nitrate or perchlorate anions and π-stacking interaction between the pyridyl rings of Mebpy nitrogen ligands.     

Synthesis and characterization of coordination polymers of a carboxylato cyclophane with metal [Zn(II) and Cd(II)]-2,2′-bipyridines

N,N′,N′′,N′′′-Tetrakis(3-carboxy-propionyl)-1,6,20,25-tetraaza-[6.1.6.1] paracyclophane, H₄cp has been complexed with metal (Zn(II) and Cd(II)) 2,2′-bipyridyls. The resulting complexes of the composition [{Zn(2,2′-bpy)}₂(cp)]_n·4H₂O 1 and [{Cd(2,2′-bpy)}₂(cp)]_n·5H₂O 2 (2,2′-bpy = 2,2′-bipyridine) have been characterized using spectroscopic (IR, solid state UV–Vis), elemental analysis and single-crystal X-ray diffraction measurements. In these complexes the cyclophane coordinates in different modes, and in complex 2, Cd(II) is hepta-coordinated. However, under harsh reaction conditions (using excess nitric acid and a longer reaction time) debranching of the cyclophane is observed in the reaction of Zn(2,2′-bpy)(NO₃)₂ with H₄cp, and a complex of the composition [Zn(2,2′-bpy)(Suc)]_n3 (suc = succinate) is isolated. Using non-covalent interactions, complexes 1 and 2 provide 3D supramolecular structures, whereas an infinite 1D chain structure is observed for complex 3. The thermal and photoluminescence properties of the complexes have also been studied.