Cadmium(II) chloride complexes of imidazole-based ligands: Solvothermal syntheses,crystal structures and luminescent properties

Presented are the solvothermal syntheses, structures, characterizations, and luminescent properties of four novel organic-modified cadmium chloride complexes constructed from CdCl₂ and imidazole (or its derivatives), namely [CdCl₂(Im)₄] (1, Im = imidazole), [CdCl₄(HAPI)₂] (2, API = N-(3-Aminopropyl)-imidazole), [Cd(μ-Cl)₂(1-Mim)₂]_∞ (3, 1-Mim = 1-methyl imidazole) and [CdCl₃(HAPI)]_∞ (4). 1 and 2 feature a zero dimensional (0D) mononuclear structure with different mole ratios of Cd: Cl: ligand, while compound 3 and 4 bear infinite chains constructed from different subunits and connection modes. Worthy of note is that 4 represents a new structural type in the family of organic modified cadmium halides. The fluorescence spectra showed that compounds 1–4 exhibited emission peaks around 450 nm with the quantum yields of 23.01%, 5.84%, 27.31%, 5.71%, respectively.     

Synthesis,X-ray structures,and photoluminescence of heterometal trinuclear Hg(II)–Pt(I) and tetranuclear Hg(II)–Pd(I) complexes

A heterometallic trinuclear complex with monovalent platinum consisting of a [Pt₂Hg] cluster bridged by two μ₃-Cl atoms and another tetranuclear complex with monovalent palladium owning the structural core of open cubane-like [Hg₂Pd₂Cl₂I₂] framework were synthesized by self-assembly reactions.     

Metal-assisted syntheses and NMR characterization of square-planar Pd(II) and Pt(II) complexes with tridentate nitrogen-donor chelate ligands

The complexes [PtCl(NNN^H)](OTf) (1^H), [PdCl(NNN^H)](OTf) (2^H), [PdCl(NNN^Me)](OTf) (2^Me), [PdMe(NNN^H)](OTf) (3^H), [PdMe(NNN^Me)](OTf) (3^Me) and [PdMe(NNN^Ph)](OTf) (3^Ph) {NNN^H = (pyridin-2-ylmethylene)-quinolin-8-yl-amine; NNN^Me = (1-pyridin-2-yl-ethylidene)-quinolin-8-yl-amine; NNN^Ph = (phenyl-pyridin-2-yl-methylene)-quinolin-8-yl-amine} were prepared by reacting a stoichiometric methanolic mixture of 8-aminoquinoline and an ortho-substituted aldehydo- or keto-pyridine {2-pyridinecarboxaldehyde, 2-acetylpyridine or 2-benzoylpyridine} with the proper Pt(II) or Pd(II) precursor in methanol. In the case of the 2 ^Me derivative, the addition of a stoichiometric amount of a Ag(I) salt to the reaction mixture was necessary to obtain the desired product. Information about the formation of these complexes are reported. In particular, NMR experiments allowed to observe the different reactivity of 8-aminoquinoline towards aldehydo- and keto-pyridines and the formation of the emiaminal ligand pyridin-2-yl-(quinolin-8-ylamino)-methanol NNN(H₂O)^H 4. Finally, the methanesulphonato-complex [Pd(η¹-OSO₂CH₃)(NNN^Me)](OTf) (5^Me) was obtained by reacting the chloro-derivative 2^Me with a stoichiometric amount of AgSO₃CH₃ in nitromethane.     

Syntheses,crystal structures,spectroscopy, and catalytic properties of two nickel-based hexaazamacrocyclic complexes with carboxylate ligands

Two new hexaazamacrocyclic nickel(II) complexes with the formula [NiL¹(4-nba)₂] (1) and [NiL²(sal)₂] (2) (L¹ = 3,10-dioctyl-1,3,5,8,10,12-hexaazacyclotetradecane, L² = 3,10-diisobutyl-1,3,5,8,10,12-hexaazacyclotetradecane, 4-nba = p-nitrobenzoate, and sal = salicylate) were synthesized at room temperature. These complexes were characterized by physico-chemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis. The coordination geometry in complexes 1 and 2 exhibit a distorted octahedron around the nickel(II) ion with hexaazamacrocyclic unit in the equatorial positions and two p-nitrobenzoate (or salicylate) anions in the axial positions. The degradation of methyl orange by potassium persulfate (KPS) in the presence of complex 1 (or 2) oxidation system occurred to near completion in 60 min compared to only 55% with KPS alone under UV light irradiation. Thus, both complexes in cooperation with KPS could be an attractive choice for degradation of organic pollutants for environmental remediation.     

Linear trinuclear manganese(II) complexes: crystal structures and magnetic properties

Two new trinuclear manganese(II) complexes, [Mn₃(O₂CCH(CH₃)₂)₆(N–N)₂] (N–N is 1,10′-phenanthroline (1) and 2,2′-bipyridine (2)) have been prepared and fully characterized. Single crystal X-ray diffraction analysis confirmed a linear arrangement of three Mn(II) centers bridged by six isobutyric carboxylate groups. The magnetic measurements showed that both complexes exhibit an S_T = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites: J/k_B = −2.31(2) and −2.67(2) K for 1 and 2, respectively.     

Synthesis,crystal structures and biological activities of 2-acetylpyridine N(4)-cyclohexylthiosemicarbazone and its manganese(II) and nickel(II) complexes

2-Acetylpyridine N(4)-cyclohexylthiosemicarbazone (HL) and its manganese(II) and nickel(II) complexes formulated as [Mn(L)₂] (1) and [Ni(L)₂] (2) have been synthesized and characterized by elemental analysis, infrared spectra, mass spectra, and single-crystal X-ray diffraction studies. In the two complexes, the coordination polyhedron approaches an octahedron, where the two ligands coordinate to the metal via the pyridine nitrogen atom and the nitrogen and sulfur donors of the thiosemicarbazide moiety. Biological studies, carried out in vitro against selected bacteria and K562 leukaemia cell line, respectively, have shown that the free ligand and its complexes exhibited distinct differences in the biological activities.     

Synthesis,crystal structures and urease inhibitory activity of copper(II) complexes with Schiff bases

Two thiocyanate-coordinated Schiff base copper(II) complexes, [CuL¹(NCS)] (1) and [Cu₂(L¹)₂(μ_1,3-NCS)₂]_n (2), where L¹ and L² are the deprotonated forms of 4-bromo-2-[(2-propylaminoethylimino)methyl]phenol (HL¹) and 2-ethoxy-6-[(2-propylaminoethylimino)methyl]phenol (HL²), respectively, have been prepared and structurally characterized. Single crystal X-ray diffraction indicates that 1 is a mononuclear copper(II) complex, while in 2, the adjacent two complex molecules are linked through two phenolate O atoms, forming a dimer. The dimers in 2 are further weakly linked through end-to-end thiocyanate bridges to form a two-dimensional sheet. The Cu atom in 1 is four-coordinate in a square planar geometry, and that in 2 is six-coordinate in an octahedral geometry. Complex 1 shows strong urease inhibitory activity, while complex 2 shows no activity.     

Palladium (II) and platinum (II) complexes containing organometallic thiosemicarbazone ligands: Synthesis,characterization, X-ray structures and antitubercular evaluation

A new series of palladium (II) and platinum (II) complexes containing ferrocenyl and cyrhetrenyl thiosemicarbazone ligands were synthesized and characterized. The two-step reaction of the organometallic thiosemicarbazones with i) K₂MCl₄ and ii) PPh₃ and their subsequent recrystallization from CH₂Cl₂/hexane yielded the binuclear complexes [Mˋ{ML_n(η⁵-C₅H₄)C(H)NNC(S)NHR}–(Cl)(PPh₃)] (M′Pd, Pt; ML_nRe(CO)₃, FeCp; RH, CH₃). The structures of the products were inferred from elemental analyses and IR, ¹H and ³¹P NMR spectroscopies. The molecular structures of 2b and 3d were confirmed by single crystal X-ray analysis. All complexes were screened in vitro against Mycobacterium tuberculosis and exhibited only moderate activity in the low micromolar range.     

Homochiral iron(II) complexes based on imidazole Schiff-base ligands: Syntheses,structures, and spin-crossover properties

A pair of mononuclear iron(II) enantiomeric complexes: fac-Λ-[Fe(R-L)₃](BF₄)₂·MeCN (1) and fac-Δ-[Fe(S-L)₃](BF₄)₂·MeCN (2) [L = 1-phenyl-N-(1-methyl-imidazol-2-ylmethylene)ethanamine] have been synthesized and characterized. X-ray crystallography reveals that iron(II) center is surrounded by three bidentate ligands defining a pseudooctahedral [FeN₆] coordination environment. R-L ligand induces the fac-Λ isomer, while S-L ligand induces the fac-Δ isomer. Magnetic measurements reveal that both of them display obviously spin-crossover behavior at 365 K. After desolvation, they exhibit a reversible spin transition with a small hysteresis loop of ca. 3 K appearing at about T_1/2↑ = 222 K and T_1/2↓ = 219 K.     

Polarographic investigation of Cu(II) complexes with π donor ligands

The polarographic reduction of Cu(II) complex chlorides with biguanides and N′- amidinoisoureas have been studied in aqueous 0.5 M KCl solution containing 0.01% gelatin. The complexes [except Cu(enH₂dbg)²⁺] show two well defined waves whose heights are pH dependent. The first (lower - E_1/2) and the second waves have been attributed to mono and bis(ligand)Cu(II) species respectively. Lower rate constant, higher activation energy and more negative E_1/2 values relative to those of a σ bonded Cu(II) chelates have been explained on the basis of chelate ring current and high π-basicity of the ligands. The gradual change of these values with the size of the N-substituents is due to decreased π-basicity of the respective ligands. Ratio of mono and bis biguanide with pH change has been calculated and activation energies for the complexes, calculated polarographically, have been found to be closely related to D_q values obtained from absorption band maxima.     

Mesogenic Pd(II) complexes based on 3-substituted pyrazol ligands

A new family of linear Pd(II) complexes based on pyrazoles containing long-chain substituents at the third position has been prepared and their mesomorphic properties studied. The crystalline structure of one of these compounds is described as a representative example of a very elongated and straight molecule.     

Synthesis,crystal structure and DNA-binding studies of a Ru(II) complex containing two main ligands

A new Ru(II)-polypyridyl complex, [Ru(L)(dppz)₂](PF₆)₄ (L = 5,5′-di(1-(trimethylammonio)methyl)-2,2′-dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine]), has been synthesized and structurally characterized. The binding of this complex with calf thymus DNA (CT-DNA) has been investigated by spectroscopic and viscosity measurement. Results indicate that the complex binds to CT-DNA via an intercalative mode. Moreover, the complex reveals a highly efficient DNA cleavage activity upon irradiation at 365 nm, during which supercoiled pBR322 DNA was converted to nicked DNA.     

Template-assisted self-assembly: Synthesis,structures, and magnetic properties of lanthanide(III)-cobalt(II) coordination complexes constructed with deprotonated 3,5-pyridinedicarboxylic acid ligand

Two new 3d-4f complexes, [LnCo(3,5-pdc)₂(3,5-Hpdc) (H₂O)₇]·H₂O (Ln = Gd 2, La 3; 3,5-pdcH₂ = pyridine-3,5-dicarboxylic acid), have been synthesized by the self-assembly of Ln(III) oxides, 3,5-pdcH₂ and the template molecule [Co(3,5-pdc)(H₂O)₅]·H₂O (1) under hydrothermal conditions. Heterometallic complexes 2 and 3 are isostructural with supracyclic units containing four Ln(III) ions and two Co(II) ions, in which Co(II) and Ln(III) are linked by the deprotonated 3,5-pdcH₂ ligands in three kinds of bridging modes. The weak antiferromagnetic coupling of complex 2 and 3 imply that the large 3,5-pdc bridges with the greater separation ( > 7 Å) cannot lead to long range magnetic ordering, the strength of d_n-f_n exchange coupling increasing with decreases the size of the lanthanide ion.     

New high-spin bis-o-semiquinonato cobalt(II) complexes with neutral donor ligands

Two novel bis-o-semiquinonato cobalt complexes Co(3,6-SQ)₂L (1, L¹ = 2,6-dimethyl-N-(pyridin-2-ylmethylene)benzenamine; 2, L² = 2,6-dimethyl-N-(thiophen-2-ylmethylene)benzenamine; 3,6-SQ is 3,6-di-tert-butyl-o-benzosemiquinonato radical-anion) were synthesized. According to X-ray analysis, complex 2 adopts square pyramidal geometry with N-coordinated neutral ligand L² in the apical site. According to magnetic susceptibility measurements and spectroscopic studies, both complexes contain high-spin cobalt(II) (d⁷, S = 3/2) and two radical-anionic o-semiquinonato ligands. There is antiferromagnetic metal–ligand and ligand–ligand coupling in 1, while complex 2 demonstrates weak antiferromagnetic ligand–ligand coupling at low temperature and ferromagnetic metal–ligand exchange at 150–300 K.     

Copper(II) and cadmium(II) complexes derived from Strandberg-type polyoxometalate clusters: Synthesis,crystal structures,spectroscopy and biological activities

Three Strandberg-type polyoxometalate compounds [Cu(L)₂(H₂O)₂]₂H₂[P₂Mo₅O₂₃]·2CH₃OH (1), [Cu(L)₂(H₂O)]H₂[Cu(L)₂(P₂Mo₅O₂₃)]·4H₂O (2), [Cd(L)₂(H₂O)₂]₂H₂[P₂Mo₅O₂₃]·2CH₃OH (3), (L = pyridine-2-carboxamide) have been synthesized and structurally characterized by elemental analysis, spectroscopic methods (IR and UV–vis) as well as single crystal X-ray diffraction. Single-crystal X-ray structural analyses indicate that 1 and 3 are isostructural and crystallized in monoclinic, space group I2/a. Biological studies have indicated that compounds 1–3 exhibit broad and effective activities against the tested cells. A synergistic effect involving L, metal and P₂Mo₅ could probably explain the improved growth-inhibiting properties. Both coordination mode and the type of metal ion play significant roles in these compounds cytotoxicity.     

Hydrothermal syntheses and crystal structures of four novel lanthanide(III) complexes based on two mixed N,O-donor ligands

Four novel polymeric lanthanide(III) complexes [Pr(NCP)(2,5-pydc)]_n·1.5nH₂O (1), [La(NCP)(2,5-pydc)]_n (2), [Nd(NCP)(2,5-pydc)]_n (3) and [Sm(NCP)(2,5-pydc)]_n (4) (HNCP = 2-(4-carboxyphenyl)imidazo(4,5-f)(1,10)phenanthroline, 2,5-H₂pydc = pyridine-2,5-dicarboxylic acid) have been hydrothermally synthesized and characterized via elemental analysis and single crystal X-ray diffraction. Structural analyses revealed that all of these four complexes possess similar two-dimensional sheet structures, which are further linked by the hydrogen bonds to furnish three-dimensional supramolecular structures. Meanwhile, the thermogravimetric analysis and photoluminescent property of complexes 1–4 have also been investigated.     

Synthesis and structural characterisation of new binuclear Pd(II) complexes with both bridging and terminal pyrazolate ligands

Dinuclear pyrazolato-bridged Pd(II) complexes Pd₂L₄⁰ and Pd₂L₄¹ have been prepared by reacting Pd(Ac)₂ and one equivalent of HL⁰ (3-phenyl-5-(2-pyridyl)pyrazole) or HL¹ (3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole. The new complexes have been characterised by elemental analyses, IR, ¹H NMR and in the case of PdL¹₄ by single crystal X-ray diffraction methods. This structure shows two palladium atoms bridged by two L¹ ligands. The square-planar geometry of each Pd atom is completed by a bidentate chelating L¹ ligand. The six-membered dipalladacycle formed by the two Pd atoms and the two bridging pyrazolato ligands adopts a distorted boat-like conformation.     

Synthesis,crystal structure and photophysical properties of a novel Pt(II) complex with multi-functionalized cyclometalating ligand

A novel Pt(II) complex [(L)PtCl] (HL = 4-{p-[N-(4-(9-carbazole))butyl-N-phenyl] aniline}-6-phenyl-2,2′-bipyridine) has been synthesized and verified by ¹H NMR, elemental analysis and X-ray crystallography. The crystal (C₄₄H₃₅N₄ClPt, M_r = 850.30) belongs to monoclinic system, space group P2(1)/c, with a = 21.864(6), b = 9.306(3), c = 17.240(5) Å, β = 96.483(6)°, Z = 4, V = 3485.3(16) ų, D_C = 1.620 g/cm³, μ(Mo-Kα) = 4.141 mm^? 1, F(000) = 1688, R₁ = 0.0591, wR₂ = 0.0976. The coordinate geometry of the Pt atom is a distorted square planar configuration. The complex molecules are stacked by a weak π–π interaction in a head-to-tail fashion along the b axis to form 1D chain and the alternating 1D chains are packed to form the 2D lamellar system. The complex shows an intense metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π*(L)) transitions (ε ～ 2 × 10⁴ dm³ mol^? 1 cm^? 1) at 448 nm in the UV–Vis absorption spectrum and a strong phosphorescence at 592 nm in CH₂Cl₂ solution at room temperature. An intramolecular energy transfer process from the carbazole unit to the arylamine-modified [(C^N^N)PtCl] emissive center exists in the complex.