Mononuclear Molecules Research Articles

Synthesis, Characterization, Crystal Structure, and Cytotoxicity of a 7-Coordinate Diorganotin(IV) Complex of 2-Acetylpyrazine N4-Methylthiosemicarbazone

The diorganotin(IV) complex [Ph2Sn(L)(CH3COO)] (1), where HL = 2-acetylpyrazine N4-methyl thiosemicarbazone, has been synthesized and characterized by elemental analysis, IR, UV/Vis and NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. Complex 1 contains mononuclear neutral molecules composed of one N2S tridentate anionic thiosemicarbazone ligand, one acetato group, and one Ph2Sn(IV) group with a seven-coordinated tin atom. In vitro biological studies have indicated that complex 1 shows effective cytotoxicity with IC50 = 5.4 μM against the K562 leukaemia cell line.

Single-molecule magnets based on rare earth complexes with chelating benzimidazole-substituted nitronyl nitroxide radicals

Three rare earth-nitronyl nitroxide radical complexes [Ln(tfa)(3)(NIT-BzImH)] (Ln(III) = Gd 1, Tb 2, Dy 3; tfa = trifluoroacetylacetonate; NIT-BzImH = 2-(2'-benzimidazolyl)-4,4,5,5-tetramethylimidazolyl-1-oxyl-3-oxide) have been successfully prepared and structurally characterized. X-Ray crystallographic analysis reveals that all three complexes are isomorphous. Their crystal structures consist of mononuclear molecule units in which lanthanide(III) is 8-coordinated to one NIT-BzImH and three trifluoroacetylacetonate ligands. The NIT-BzImH acts as a bidentate ligand via its nitrogen atom of the imidazole ring and the oxygen atom of the N-O group. The magnetic properties of complexes 1-3 were studied. All the three complexes exhibit ferromagnetic Ln(III)-radical coupling. AC magnetic susceptibility studies of 2 and 3 show slow magnetic relaxation suggesting that they behave as SMMs.

Synthesis, characterization, and X-ray crystal structures of zinc(II) complexes with schiff bases 2-[(2-isopropylaminoethylimino)methyl]-5-methoxyphenol and N,N-dimethyl-N′-(1-pyridin-2-ylethylidene)ethane-1,2-diamine

Two new zinc(II) complexes, [ZnBr2L1] (I) and [ZnBr2L2] (II), where L1 is 2-[(2-isopropylaminoethylimino)methyl]-5-methoxyphenol and L2 is N,N-dimethyl-N′-(1-pyridin-2-yl-ethylidene)ethane-1,2-diamine, were prepared and characterized using elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction. In complex I, the Zn(II) atom is coordinated by one phenolic O and one imino N atoms of L1 and two Br atoms, forming a tetrahedral coordination geometry. In complex II, the Zn(II) atom is in a trigonal bipyramidal coordination geometry with the equatorial plane formed by the imino N atom of L2 and two Br atoms and with the two axial positions occupied by one pyridine N and one amino N atoms of L2. In the crystal structure of I, the mononuclear zinc complex molecules are linked through intermolecular N-H…O and N-H…Br hydrogen bonds, forming chains running along the y axis. The chains are further linked via intermolecular C-H…Br hydrogen bonds. In the crystal structure of II, the mononuclear zinc complex molecules are linked through intermolecular C-H…Br hydrogen bonds, forming a 3D network.

“Wheel-and-axle” binuclear Cu(II) dioximates mediated by 1,2-bis(4-pyridyl)ethane: Synthesis, X-ray study and luminescent properties

The reaction of copper(II) acetate or fluoride with classic dioximes in the presence of 1,2-bis(4-pyridyl)ethane resulted in four novel compounds with the compositions [Cu 2(dmgH) 4bpe] ( 1), [Cu 2(NioxH) 4bpe] ( 2), [Cu 2(dpgH) 4bpe] ( 3), and [Cu 2(dpgH) 4bpe][Cu(dpgH) 2bpe] 2·2DMF ( 4) (where dmgH 2 = dimethylglyoxime, NioxH 2 = 1,2-cyclohexanedionedioxime, dpgH 2 = diphenylglyoxime, bpe = 1,2-bis(4-pyridyl)ethane, and DMF = N, N′-dimethylformamide), whose crystal structures were determined by single crystal X-ray diffraction. In the binuclear molecules 1– 3, as well as in both binuclear and mononuclear molecules in 4 each Cu(II) atom has an identical N 5-environment formulated by four oximic nitrogen atoms of two monodeprotonated ligands in a slightly distorted square planar mode, and the nitrogen atom of the bpe molecule being in the apical position. The new compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Luminescence investigations for 1, 2 and 4 were carried out to clarify whether the guest inclusion in the crystal lattice is accompanied by changes in the emission spectra.

Crystalline O, O′-di- sec-butyl and O, O′-diethyl dithiophosphate platinum(II) complexes: Synthesis, 13C and 31P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Crystalline bis( O, O′-di- sec-butyldithiophosphato)platinum(II) was prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S 2P(O- sec-C 4H 9) 2} 2], in which the dithiophosphate groups display structural equivalence in both 31P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S, S′-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS 2P], in this molecule. The planar configuration of the [PtS 4] chromophore in structure 1 is governed by the dsp 2-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic 31P chemical shift tensors. The observed essential dispersion of the 31P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio- meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.

Re(V) complexes formed by metal-assisted solvolysis of di-(2-pyridyl)ketone: Synthesis, X-ray studies, redox behavior and DFT calculations

The complexes {ReOCl2[(py)2C(O)(OR)]}, (R=CH2CH3 (1), CH2CH2CH3 (2)) were obtained from the metal-assisted alcoholysis reaction of di-2-pyridylketone. Their crystal structures were determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of neutral mononuclear molecules containing the [ReO]3+ core. In both compounds the Re(V) central ion is also bonded to an oxygen and both nitrogens from the organic ligand and two chlorides in a distorted octahedral environment. Cyclic voltammograms in CH3CN solutions showed two main redox responses, both of them involving one electron transfer. Comparative theoretical studies on equilibrium geometries and electronic properties were conducted in the framework of the density functional theory (DFT).

The Zn(II)-organic coordination polymers based on 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylate ligands: Crystal structures and luminescent properties

Abstract Two novel compounds, [Zn(H2PIDC)2(H2O)2] (1) and [Zn4(PIDC)2(SO4)(H2O)5]·(2.5H2O) (2) (H3PIDC = 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid) have been synthesized under hydrothermal condition, and characterized by thermal analyses (TGA), powder X-ray diffractions (PXRD), and single-crystal X-ray diffractions, respectively. Compound 1 is constructed from mononuclear molecules which form the 2D square networks and further extend to 3D supermolecular framework through the π–π stacking and strong hydrogen bonding interactions. Compound 2 exhibits a 3D framework and generates the 1D open rhombic channels filled with the coordinated water molecules, sulfate anions and free water molecules. The structure of 2 can be rationalized as a (4,4,4)-connected net and shown as a unique (4.53.6.7)4(42.52.72)2(52.62.72) topology. The different luminescent nature for 1 and 2 may be due to their various delocalization environments.

Aqua[N′-(3-ethoxy-2-oxidobenzyl-κO)furan-1-carbohydrazidato-κ2N′,O]dioxidomolybdenum(VI)–4,4′-bipyridine (2/1)

The MoVI atom in the title co-crystal, [Mo(C14H12N2O4)O2(H2O)]·0.5C10H8N2, is O,N,O′-chelated by the deprotonated Schiff base and coordinated by the oxide and water O atoms in an octa­hedral geometry. The five-membered chelate ring is planar (r.m.s. deviation = 0.019 Å), but the six-membered chelate ring is puckered (r.m.s. deviation = 0.108 Å). Two mononuclear mol­ecules are linked across a center of inversion by an O—Hwater⋯O hydrogen bond; adjacent dinuclear units are linked by an water–4,4′-bipyridine O—H⋯N hydrogen bond, generating a linear chain structure. The 4,4′-bipyridine mol­ecule is disordered over two positions in a 1:1 ratio.

Mononuclear manganese and tetranuclear copper compounds and their supramolecular networks constructed from hexafluoroglutaric acid and 2,2′-bipyridine

Mn(2,2′-bpy)2(HFGA) (1) and [Cu4(μ3-OH)2(μ2-OH)2(H2O)2(2,2′-bpy)4] · 2HFGA · 4H2O (2) (H2HFGA = hexafluoroglutaric acid and 2,2′-bpy = 2,2′-bipyridine) have been synthesized and characterized by X-ray structural analyses. 1 is a monomer with six-coordinate Mn2+ from two oxygens of HFGA and four nitrogens of two 2,2′-bpy. Complex 2 is tetranuclear with four Cu2+ ions bridged by triple-bridging μ3-OH and double-bridging μ2-OH. There are two crystallographically independent Cu2+ ions in different five-coordinate environments. Cu1 is coordinated by 2,2′-bpy and three OH ligands. Cu2 is coordinated by 2,2′-bpy, two μ3-OH ligands, and one water molecule. The mononuclear and tetranuclear molecules as building blocks are connected to construct different 3-D supramolecular architectures via noncovalent interactions. Particularly, the lone pair (lp)–π (F···π) interaction in 1 is observed. A hybrid water-anionic tape by linkage of {[(H2O)4(HFGA)]2 4−} n fragments consisting of water dimers and HFGA anions in 2 is observed.

Metal–organic supramolecular architectures derived from a new zwitterionic dicarboxylate ligand

A series of new coordination compounds with 1-carboxymethylpyridinium-4-benzoate (L) and transition metal ions have been synthesized. They are formulated as [M(L)2(H2O)4] · 4H2O M=Mn (1) and Co (2), {[M(L)2] · xH2O} n M=Mn, x = 1 (3); M=Co, x = 2 (4), and M=Cu, x = 3 (5). In 1 and 2, the zwitterionic dicarboxylate ligand is monodentate through only one carboxylate to generate mononuclear molecules. The molecules are assembled through O–H ··· O interactions to give 3-D pillared layer-like architectures, in which interesting 1-D tape-like hydrogen bonding motifs are connected into 2-D layers via carboxylate-mediated hydrogen bonds. In 3–5, the organic ligands serve as bridges with one carboxylate monodentate and the other chelating, and the metal ions are linked by double bridges to give 1-D polymeric chains, which are zigzag (3) or stair-like (4 and 5) due to the cis or trans coordination geometry around metal ions. The chains are further stabilized and associated into 3-D architectures through intra- and interchain hydrogen bonding and/or π–π stacking interactions.

Synthesis, crystal structures, and magnetic properties of cobalt(II) and nickel(II) complexes of 2,2′-bipyridine-6,6′-dicarboxylate: three three-dimensional networks formed via hydrogen bonding interactions

Three Co(II) and Ni(II) complexes, namely [Co(bpdc)(H2O)2] (1), [Ni(bpdc)(H2O)2] (2), and [Co2(bpdc)2(prz)0.5(H2O)3]·0.5H2O (3) (H2bpdc = 2,2′-bipyridine-6,6′-dicarboxylic acid and prz = piperazine), have been synthesized from H2bpdc and the corresponding metal salts under hydrothermal conditions. The complexes were characterized by physico-chemical and spectroscopic methods, as well as by X-ray crystallography. Compounds 1 and 2 both consist of neutral mononuclear molecules, of [Co(bpdc)(H2O)2] and [Ni(bpdc)(H2O)2], respectively. Compound 3 consists of a mononuclear molecule of [Co(bpdc)(H2O)2] and a binuclear molecule of [Co2(bpdc)2prz (H2O)2]. The discrete neutral complexes 1–3 further extend their structures into three-dimensional supramolecular architectures by intermolecular O–H⋯O and C–H⋯O hydrogen bonds as well as π–π stacking interactions. Magnetic susceptibility measurements show that complex 3 exhibits weak ferromagnetic interactions between the two Co(II) ions bridged by the prz ligand, with C = 5.41 cm3 mol−1 K and θ = +27.6 K, respectively.

Chiral complexes of PdCl2 with hydroxypyrazolylquinoline and pyrazolylquinoline based on the monoterpenoid (+)-3-carene: Synthesis and structures

The chiral complexes [PdL1Cl2] (I) and [PdL2Cl2] (II) (where L1 and L2 are hydroxypyrazolylquinoline and pyrazolylquinoline, respectively, based on the monoterpenoid (+)-3-carene) were obtained and examined using X-ray diffraction. The crystal structures of complexes I and II are built from mononuclear acentric molecules. The Pd2+ ions coordinate two N atoms of the chelating bidentate ligand L1 or L2 and two Cl atoms. The coordination polyhedron Cl2N2 is a square distorted in a tetrahedral manner. In structure I, adjacent molecules are linked by intermolecular contacts and hydrogen bonds Cl···H-O, which gives rise to chains aligned with the axis x. In structure II, contacts that are substantially shorter than the van der Waals interactions were not detected.

Synthesis of solvates of the copper(II) complex with chiral caryophyllane-type morpholino oxime (HL). Structure of Cu(HL)Cl2 · CHCl3

Paramagnetic Cu(HL)Cl2 · 0.25CHCl3 (I) and Cu(HL)C12 · 0.25CH2C12 (II), where HL is the optically active morpholino oxime obtained from the terpenoid caryophyllene, were synthesized. The crystals of Cu(HL)Cl2 · CHCl3 (III) were isolated. According to X-ray diffraction data, the crystals of III are composed of acentric mononuclear complex molecules Cu(HL)Cl2 and solvate molecules CHCl3. In the complex molecules, the Cu ion coordinates two N atoms of the bidentate chelating ligand HL and two C1 atoms at the vertices of a distorted tetrahedron. The translationally identical molecules of the complex combined by H-bonds form chains along the axis x.

Crystal structure and photoluminescence of the optically active complex [ZnL1Cl2], where L1 = pyrazolylquinoline—a derivative of monoterpenoid (+)-3-carene

The optically active complex [ZnL1Cl2] (I), where L1 = pyrazolylquinoline (a derivative of monoterpenoid (+)-3-carene) is obtained. Single crystals of compound I are grown and its crystal structure is determined from X-ray diffraction data (X8 APEX diffractometer, MoKα radiation, 3031 Fhkl). The crystals of I are monoclinic; unit cell dimensions are: a = 8.4189(10) A, b = 12.7194(11) A, c = 9.7652(12) A, β = 111.318(3)°, V = 974.14(19) A3, Z = 2, dx = 1.499 g/cm3, space group P21. Complex I is composed of discrete mononuclear molecules. In coordination of Cl atoms and two N atoms of the bidentate cycling ligand L1, a distorted tetrahedral Cl2N2 polyhedron forms at Zn. In the complex molecule, a fragment consisting of five-membered pyrazole and chelate rings, a five-membered carbocycle, and also two six-membered quinoline rings is almost planar. Solid complex I shows strong white photoluminescence at 300 K and λexc = 365 nm in the 400–700 nm range with λmax = 490 nm.

Synthesis, crystal structures and magnetic properties of a radical ligand and its corresponding copper(II) complex

A new chelating radical ligand, IMMeBzIm (IMMeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl) and its copper(II) complex [Cu(IMMeBzIm)2(ClO4)]·(ClO4) have been prepared and characterized by IR, magnetic and single-crystal X-ray analysis. In the crystal structures, both free IMMeBzIm and the complex crystallize in monoclinic space groups P2(1)/c and C2/c, respectively. The structure of IMMeBzIm consists of mononuclear molecules. In the complex, the coordination geometry around copper is a distorted square pyramid, and the apical position is occupied by one oxygen atom of ClO4 − anion. A 1-D polymer is formed through intermolecular H-bond interactions. The variable-temperature magnetic susceptibility of the free IMMeBzIm suggests weak antiferromagnetic coupling with J = −1.12 cm−1 where the spin Hamitonian is defined as Ĥ = −2 JŜ 1 Ŝ 2 between radical and radical.

Copper(II) complexes based on a new chelating 4-(3,5-diphenyl-1 H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine ligand: Synthesis and crystal structures. Lone pair–π, C–H···π, π–π and C–H···A (A = N, Cl) non-covalent interactions

A new bidentate chelating pyrazolylpyrimidine ligand bearing a strong electron-donating substituent, i.e. 4-(3,5-diphenyl-1 H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) ( Scheme 1), has been synthesized and used to obtain the copper(II) complexes by reaction with CuCl 2. The molar ratio Cu:L = 1:2 leads to isolation of a complex having CuL 2Cl 2 empirical formula, while the molar ratio Cu:L = 1:1 gives a complex with CuLCl 2 empirical formula. The crystal structure of L as well as the structures of both complexes were studied by single crystal X-ray diffraction. The crystal structure of CuL 2Cl 2 compound is formed by trans-[CuL 2Cl 2] mononuclear molecules. Surprisingly, in contrast to the previous compound having molecular structure, the crystal structure of CuLCl 2 consists of mononuclear [CuL 2Cl] + complex cations and dinuclear [Cu 2Cl 6] 2− anions. Thus, formula of CuLCl 2 complex can be represented as [CuL 2Cl] 2[Cu 2Cl 6]. In both complexes molecules of L adopt bidentate chelating coordination mode through N 2 atom of pyrazole and N 3 atom of pyrimidine rings forming five-membered CuN 3C metallocycles. Owing to C–H···N interactions and π–π-stacking L molecules form 2D network. In the structure of trans-[CuL 2Cl 2] there exist double lone pair(N(piperidine))–π(pyrimidine) interactions and C–H···Cl contacts resulting in the formation of 1D chains. Layered 2D structure of [CuL 2Cl] 2[Cu 2Cl 6] results from C–H···Cl, C–H···π and double lone pair(Cl([CuL 2Cl] + complex cation)–π(pyrimidine) interactions.

Synthesis of Pd(II) complexes containing the protonated form or molecule of 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline (L). The crystal structure of [Pd(HL)Cl3

The diamagnetic complexes [Pd(HL)Cl3](I) and PdLCl2(II), where L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline, were obtained. According to X-ray diffraction data, the crystal structure of complex I consists of mononuclear acentric molecules. The coordination polygon PdNCl3 is a distorted square (trapezium) made up of the pyrazole N atom of the monodentate ligand (cation HL+) and three Cl atoms. Complex II seems to contain the square polygon PdN2Cl2.

Synthesis, structure, and luminescence properties of complex ZnLClb2 (L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline)

A complex ZnLClb2 (L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline) was synthesized. According to X-ray diffraction data, the Znp2+ ions in mononuclear molecules of the obtained complex coordinate two N atoms of the bidentate chelating ligand L and two Cl atoms. The coordination polyhedron Cl2Nb2 represents a distorted tetrahedron. In solid state at 300 K, the ligand L exhibits weak photoluminescence in the visible spectral range. The complex ZnLClb2 exhibits bright blue photoluminescence.

DNA cleavage activities of tetraazamacrocyclic oxamido nickel(II) complexes

The DNA cleavage activities of nickel(II) ion and four closely related macrocyclic nickel(II) complexes NiL 1 ∼ NiL 4 in the absence of any added redox cofactors are compared and the structure of NiL 3 methanol solvate has been characterized by single crystal X-ray analysis, where L 1 ∼ L 4 are the dianions of tetraazamacrocyclic oxamido Schiff bases. In NiL 3·MeOH, the macrocyclic [N 4] ligand coordinates to the central Ni(II) ion forming a distorted square–planar geometry. The adjacent mononuclear molecules are linked by O–H⋯O hydrogen bonds and Ni⋯O and Ni⋯L van der Waals forces into 2D supramolecular structure. Agarose gel electrophoresis studies indicate that the ability of these nickel(II) complexes to cleave DNA is highly dependent upon the ligand employed. In the absence of any added oxidizing agents, only NiL 3 is a relatively good DNA cleavage agent, and the process of plasmid DNA cleavage is much sensitive to ionic strength and pH value. The NiL 3-mediated DNA cleavage reaction is a typical pseudo-first-order consecutive reaction, and the rate constants of 0.148 ± 0.007 h −1 ( k 1) and 0.0118 ± 0.0018 h −1 ( k 2) for the conversion of supercoiled to nicked DNA and nicked to linear DNA are obtained in presence of 0.5 mmol L −1 NiL 3. The results of DNA cleavage experiments, combining with those of circular dichroism (CD) and fluorescence spectroscopy indicate that the main binding modes between DNA and the complexes should be groove binding and electrostatic interaction.

Crystal structure of (acetylacetonato) (dicarbonyl)iridium(I)

The structure of Ir(CO)2(acac) is determined by XRD at room temperature. Crystallographic data for C7H7IrO4 are: a = 6.4798(5) A, b = 7.7288(5) A, c = 9.1629(10) A, α = 105.738(2)°, β = 90.467(3)°, γ = 100.658(2)°, space group 1, P $$ \bar 1 $$ , V= 433.24(6) A3, Z = 2, d calc = 2.662 g/cm3, R = 0.0167. The structure is built of isolated mononuclear molecules. The central iridium atom has a square coordination environment formed by two oxygen atoms that belong to the acetylacetonate ligand and two carbon atoms of carbonyl groups. The average Ir-O and Ir-C bond lengths are 2.045(3) A and 1.832(6) A respectively. Molecules are stacked in such a way that the planes of coordination squares turn out to be parallel to the Ir...Ir distances between the nearest neighbors in the stack of 3.242 A and 3.260 A.