Nickel(II)-, cobalt(II)-, copper(II)-, and zinc(II)-phthalate and 1-methylimidazole coordination compounds: synthesis, crystal structures and magnetic properties

Three new coordination polymers [M(Pht)(1-MeIm)₂]_n (where M=Cu (1), Zn (2), Co (3); Pht²⁻=dianion of o-phthalic acid; 1-MeIm=1-methylimidazole) and two compounds [M(1-MeIm)₆](HPht)₂ · 2H₂O (M=Co (4), Ni (5)) have been synthesized and characterized by X-ray crystallography. The structures of 1-3 (2 is isostructural to 3) consist of [M(1-MeIm)₂] building units connected by 1,6-bridging phthalate ions to form infinite chains. In complex 1, each copper(II) center adopts a square coordination mode of N₂O₂ type by two O atoms from different phthalate ions and two N atoms of 1-MeIm, whereas in 3 two independent metal atoms are tetrahedrally (N₂O₂) coordinated to a pair of Pht ligands and a pair of 1-MeIm molecules. There are only van der Waals interactions between the chains in 1, while the three-dimensional network in 3 is assembled by C-H?O contacts. In contrast to polymers 1-3 the structures of 4 and 5 (complexes are also isostructural) are made up of the [M(1-MeIm)₆]²⁺ cation, two hydrogen phthalate anions (HPht⁻) and two H₂O solvate molecules. The coordination around each metal(II) atom is octahedral with six nitrogen atoms of 1-MeIm. Extended hydrogen bonding networks embracing the solvate water molecules and a phthalate residue as well as the weak C-H?O interactions stabilize the three-dimensional structures. Magnetic studies clearly show that the magnetic ions do not interact with each other. Furthermore, in compound 4 we have another example of a highly anisotropic Co²⁺ ion with a rhombic g-tensor and large zero-field-splitting. The complexes were also characterized by IR and ¹H NMR spectroscopy, thermogravimetric analysis, and all data are discussed in the terms of known structures.     

Synthesis, crystal structure, magnetism and electrochemical properties of two copper(II) furoyltrifluoroacetonate complexes with nitroxide radical

Two new magnetic copper compounds were obtained using the 4,4,4-trifluoro-1-furoylbutane-1,3-dione (Ftfac) ligand and two nitroxide radicals: 3-pyridyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NITmPy) and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxy (Tempol). The complexes with formula [Cu(Ftfac)₂(NITmPy)₂] (1) and [Cu(Ftfac)₂(Tempol)] (2) were structurally characterized by single-crystal X-ray diffraction. In compound 1, the copper ion has a distorted octahedral environment, bound to two NITmpPy ligands through the nitrogen atom of the pyridine ring. In compound 2, the copper ion has a distorted pyramidal environment in which the apical position is occupied by the oxygen atom of the Tempol hydroxyl group. The temperature dependence of the magnetic susceptibility of the two compounds was investigated. It was found that compound 1 presents ferromagnetic interaction (J = 9.1 cm⁻¹) among copper(II) ions and NITmPy radicals. As a result of the interconnection between molecular moieties through H-bonds, compound 2 presents an unusual magnetic behavior with alternating ferro- and antiferromagnetic interactions.     

Hydrazone Schiff base-manganese(II) complexes: Synthesis, crystal structure and catalytic reactivity

Five dissymmetric tridentate Schiff base ligands, containing a mixed donor set of ONN and ONO were prepared by the reaction of benzhydrazide with the appropriate salicylaldehyde and pyridine-2-carbaldehyde and characterized by FT-IR, ¹H and ¹³C NMR. The complexes of these ligands were synthesized by treating an ethanolic solution of the appropriate ligand and one equivalent Et₃N with an equimolar amount of MnCl₂ · 4H₂O or alternatively by a more direct route in which an ethanolic solution of benzhydrazide was added to ethanolic solution of appropriate salicylaldehyde and MnCl₂ · 4H₂O solution to yield [MnCl(L¹)(H₂O)₂], [Mn(L²)₂(H₂O)₂], [MnCl(L³)], [MnCl(L⁴)] and [MnCl₂(H₂O)(L⁵)]. The hydrazone Schiff base ligands and their manganese complexes including HL^1-4 and L⁵ (HL¹ = benzoic acid (2-hydroxy-3-methoxy-benzylidene)-hydrazide, HL² = benzoic acid (2,3-dihydroxy-benzylidene)-hydrazide, HL³ = benzoic acid (2-hydroxy-benzylidene)-hydrazide, HL⁴ = benzoic acid (5-bromo-2-hydroxy-benzylidene)-hydrazide, L⁵ = benzoic acid pyridine-2-yl methylene-hydrazide) were characterized on the basis of their FT-IR, ¹H and ¹³C NMR, and molar conductivity. The crystal structures of HL¹ and [MnCl₂(H₂O)L⁵] have been determined. The results suggest that the Schiff bases HL¹, HL², HL³, and HL⁴ coordinate as univalent anions with their tridentate O,N,O donors derived from the carbonyl and phenolic oxygen and azomethine nitrogen. L⁵ is a neutral tridentate Schiff base with N,N,O donors. ESI-MS for the complexes Mn-L^2,3,5 provided evidence for the presence of multinuclear complexes in solution. Catalytic ability of Mn-L^1-5 complexes were examined and found that highly selective epoxidation (>95%) of cyclohexene was performed by iodosylbenzene in the presence of these complexes and imidazole in acetonitrile.     

Dinuclear terephthalato-bridged copper(II) complexes: Syntheses, spectral and structural characterization, and magnetic properties

Herein, we report the syntheses, spectral and structural characterization, and magnetic behavior of four new dinuclear terephthalato-bridged copper(II) complexes with formulae [Cu₂(trpn)₂(μ-tp)](ClO₄)₂ · 2H₂O (1), [Cu₂(aepn)₂(μ-tp)(ClO₄)₂] (2), [Cu₂(Medpt)₂(μ-tp)(H₂O)₂](ClO₄)₂ (3) and [Cu₂(Et₂dien)₂(μ-tp)(H₂O)](ClO₄)₂ (4) where tp = terephthalate dianion, trpn = tris(3-aminopropyl)-amin, aepn = N-(2-aminoethyl)-1,3-propanediamine, Medpt = 3,3′-diamino-N-methyldipropylmine and Et₂dien = N,N-diethyldiethylenetriamine. The structures of these complexes consist of two μ-tp bridging Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry of the Cu(II) ions in these compounds may be described as close to square-based pyramid (SP) with severe significant distortion towards trigonal bipyramid (TBP) stereochemistry in 1. The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, the solid infrared spectral data for the stretching frequencies of the tp-carboxalato groups, the ν(COO⁻) reveals the existence of bis(monodentate) coordination mode for the bridged terephthalate ligand. The susceptibility measurements at variable temperature over the range 2-300 K are reported. Despite the same bonding mode of the tp bridging ligand, there has been observed slight antiferromagnetic coupling for the compounds 1 and 4 with J values of −0.5 and −2.9 cm³ K mol⁻¹, respectively, and very weak ferromagnetic coupling for 2 and 3 with J values of 0.8 and 10.1 cm³ K mol⁻¹, respectively. The magnetic results are discussed in relation to other related μ-terephthalato dinuclear Cu(II) published compounds.     

Seven-coordinate Mn(II) and Co(II) complexes of the pentadentate ligand 2,6-diacetyl-4-carboxymethyl-pyridine bis(benzoylhydrazone): Synthesis, crystal structure and magnetic properties

The metal complexation properties of a functionalized N₃O₂ donor ligand H₂L², where H₂L² stands for 2,6-diacetyl-4-carboxymethyl-pyridine bis(benzoylhydrazone), are investigated by structural and spectroscopic (IR, ESI-MS and EPR) characterization of its Mn(II) and Co(II) complexes. The ligand H₂L² is observed to react essentially in the same fashion as its unmodified parent H₂L¹ producing mixed-ligand [M(H₂L²)(Cl₂)] complexes (M = Mn^II (1), Co^II (3)) upon treatment with MCl₂. Complexes [M(HL²)(H₂O)(EtOH)]BPh₄ (M = Mn 2, M = Co 4), incorporating the supporting ligand in the partially deprotonated form (HL²)⁻, are formed by salt elimination of the [M(H₂L²)(Cl₂)] compounds with NaBPh₄. Compounds 2 and 4 are isostructural featuring distorted pentagonal-bipyramidal coordinated Mn^II and Co^II ions, with the H₂O and EtOH ligands bound in axial positions. Intermolecular hydrogen bonding interactions of the type M-OH₂?O-M involving the H₂O ligands and the carbonyl functions of the supporting ligand assembles the complexes into dimers. Temperature-dependent magnetic susceptibility measurements (2-300 K) show a substantially paramagnetic Curie behavior for the Mn²⁺ compound (2) influenced by zero-field splitting and significant orbital angular momentum contribution for 4 (high-spin Co^II). The exchange coupling across the Mn^II-OH₂?O-Mn^II bridges in 2 was found to be less than 0.1 cm⁻¹, suggesting that no significant intradimer exchange coupling occurs via this path.     

Synthesis, crystal structures, antimicrobial properties and enzyme inhibition studies of zinc(II) complexes of thiones

Zinc(II) complexes of thiones having the general formula [ZnL₂Cl₂] where L = N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu), tetramethylthiourea (Tmtu), N,N′-diethylthiourea (Detu), and diazinane-2-thione (Diaz), were prepared by reacting ZnCl₂ with the corresponding thiones. They were characterized by elemental analysis, IR and NMR spectroscopy and two of them {[(Tmtu)₂ZnCl₂] (1) and [(Diaz)₂ZnCl₂] (2)} using X-ray crystallography. The spectral data suggests that the coordination of thiones to zinc(II) occurs through the sulfur atom as indicated by an up field shift in the CS resonance of thiones in ¹³C NMR and downfield shift in N-H resonance in ¹H NMR. The crystal structures of the complexes show a tetrahedral coordination environment around the zinc atoms with the bond angles ranging from 99.33(5)° to 116.81(7)°. Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentration and the results showed that the complexes exhibited significant activities against gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and yeasts (Candida albicans, Saccharomyces cerevisiae). However, moderate activity was observed against molds (Aspergillus niger, Penicillium citrinum). The complexes were also tested for inhibition activity against an enzyme, Alkaline Phosphatase EC 3.1.3.1 and were found to be active inhibitors.     

Synthesis, structure and antimicrobial activity of manganese(II) and cobalt(II) complexes of the polyether ionophore antibiotic Sodium Monensin A

Mononuclear neutral manganese(II) and cobalt(II) complexes with the antibiotic Sodium Monensin A (Mon-Na, 1b) were synthesized and characterized. The crystal structures of M(Mon-Na)2Cl2.H2O (M=Mn, 2; M=Co, 3) were determined by X-ray crystallography. The complexes crystallize in monoclinic space group C2 with a tetrahedrally coordinated transition metal attached to oxygen atoms of deprotonated carboxyl groups of two Sodium Monensin molecules and two chloride ions. The sodium ion remains in the cavity of the ligand and cannot be replaced by Mn(II) or Co(II). The complexes were additionally characterized by different spectroscopic techniques (UV-Visible, EPR, FAB-MS). A preferable octahedral environment around the transition metal centers is observed in polar solvents while the complexes retain their tetrahedral structure in non-polar media. The antimicrobial activity of 1b, 2 and 3 was tested against Gram(+) and Gram(-) bacteria.     

Pyridoxal thiosemicarbazonate monohydrate of dimethylthallium(III): X-ray structure and spectroscopic properties

The title compoud, [TlMe₂(HL)(H₂O)] (HL = monoanion of pyridoxal thiosemicarbazone), crystallizers in the triclinic space group , No. 2). The HL⁻anion coordinates to the thallium atom, in an unusual mode through the S atom (Tl-S = 2.832(1) Å), and also forms a weak bond with the metal atom of a neighbouring molecule to make an asymmetric bridge (Tl′…S = 3.190(1) Å). The acidic proton retained in the thiosemicarbazonato anion is located on the oxygen of the phenolic hydroxyl group. The water molecule is only 2.630(4) Å from the metal, suggesting a rather strong bond that contrasts with the long distance between the thallium and the phenolic oxygen (Tl…O(1)′ = 3.124(4) Å). If both strong and weak intermolecular interactions are taken in account, the metal has distorted octahedral coordination with the methyl groups in apical positions. The solid state IR spectrum and ¹H, ¹³C and ²⁰⁵Tl NMR spectra in DMSO solution are also discussed.     

Chlorido-bridged polymeric and dinuclear copper(II) complexes with tridentate Schiff base: Synthesis, crystal structure and magnetic properties

Two copper(II) complexes, [Cu(qsal)Cl](DMF) (1) and [Cu₂(qsalBr)₂Cl₂](DMF) (2), with tridentate Schiff base ligands, 8-(salicylideneamino)quinoline (Hqsal) and 8-(5-bromo-salicylideneamino)quinoline (HqsalBr), respectively, were synthesised and structurally characterized. Each copper(II) ion in the two complexes is in a distorted square pyramidal N₂OCl₂ environment. Complex 1 exists as a polymeric species via equatorial-apical chloride bridges, whereas 2 is a di-chlorido-bridged dinuclear complex, where each bridging chloride simultaneously occupies an in-plane coordination site on one copper(II) ion and an apical site on the other copper(II) ion. Variable-temperature magnetical susceptibility measurements on the two complexes in the temperature range 2-300 K indicate the occurrence of intrachain ferromagnetic (J = +6.58 cm⁻¹) and intramolecular antiferromagnetical (J = −6.91 cm⁻¹) interactions.     

Synthesis, crystal structure, characterization of zinc(II), cadmium(II) complexes with 3-thiophene aldehyde thiosemicarbazone (3TTSCH). Biological activities of 3TTSCH and its complexes

The reaction of zinc(II) chloride, cadmium(II) chloride and bromide with 3-thiophene aldehyde thiosemicarbazone leads to the formation of a series of new complexes. They have been characterized by spectroscopic studies: infrared, ¹H NMR, and electronic spectra. The crystal structures of the compound [ZnCl₂(3TTSCH)₂] and [CdBr₂(3TTSCH)₂] have been determined by X-ray diffraction methods. For the complexes [ZnCl₂(3TTSCH)₂] and [CdBr₂(3TTSCH)₂], the central ion is coordinated through the sulfur, and for the complexes [CdCl₂(3TTSCH)], [CdBr₂(3TTSCH)] the ion is coordinated through the sulfur as well as azomethine nitrogen atom of the thiosemicarbazone. In addition, fungistatic and bacteriostatic activities of both ligand and complexes have been evaluated. Cadmium(II) complexes have shown the most significant activities.     

NMR characterization, dynamics and crystal structure of [2,2′-dipyridyl(bis-pyridine) palladium(II)] and related cations

Eight Pd^II complexes are chemically and structurally characterized by NMR and X-ray diffraction. Their common structural feature is the planar 2,2′-bipyridyl ligand (bipy) faced by variously substituted, vertical pyridines (n-Rpy). Dissymmetric C_sn-Rpy lead, in solution, to syn and anti geometric isomers whose dynamic interconvertion can be either driven by pyridine rotation or reversible dissociation. Activation energy of the rotational motion is for Pd lower than Pt in accord with a weaker double bond character of Pd-N_py bond. The energetic barrier also owns a steric contribution which becomes dominant for 2-Mepy. Methyl bumping locks rotation and loosens Pd-N_py bond, triggering an alternative isomerization pathway.     

Cyanato bridged binuclear nickel(II) and copper(II) complexes with pyridylpyrazole ligand: Synthesis, structure and magnetic properties

Binuclear cyanate bridged nickel(II) complex [Ni(L)(NCO)]₂(PF₆)₂ (1) and copper(II) complex [Cu(L)(NCO)]₂(PF₆)₂ (2), where L is N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine, a tetradentate N₄-coordinated ligand have been synthesized and characterized by physicochemical method. The structures of complexes 1 and 2 have been studied by single crystal X-ray diffraction analysis. The structure analysis reveals that both nickel(II) and copper(II) center are coordinated in distorted octahedral fashion and coordination mode of cyanate ligand is end-to-end (μ-1,3) for complex 1 but it is double end-on (μ-1,1) mode for complex 2. The variable temperature magnetic susceptibility data, measured from 2 to 300 K, show weak antiferromagnetic interaction with J value −6.2(1) cm⁻¹ for complex 1, whereas complex 2 has very weak ferromagnetic interaction with J value +0.5(1) cm⁻¹.     

Dinuclear triply bridged copper(II)-carboxylato compounds with different bischelating ligands: Synthesis, crystal structure, spectroscopic and magnetic properties

Three new triply bridged dinuclear copper(II) compounds containing carboxylato bridges, [Cu₂(μ-CH₃COO-κ-O¹,O²)₂(μ-CH₃COO-κ-O¹)(dpyam)₂](BF₄) (1), [Cu₂(μ-CH₂CH₃COO-κ-O¹,O²)(μ-OH)(μ-OH₂)(bpy)₂](ClO₄)₂ (2) and [Cu₂(μ-CH₃COO-κ-O¹,O²)(μ-OH)(μ-OH₂)(phen)₂](ClO₄)₂ (3) (in which dpyam = di-2-pyridylamine, bpy = 2,2-bipyridine, phen = phenanthroline), have been synthesized in order to investigate the magnetic super-exchange pathway between coupled copper(II) centres. All three compounds display a distorted square-pyramidal arrangement around each copper(II) ion with a CuN₂O₃ chromophore. Compound 1 has three acetato bridges, two of which connect each square pyramid at two equatorial sites in a triatomic bridging mode and the third acetato bridge acts at the apical site in the monoatomic bridging mode. The structures of compounds 2 and 3 are mutually similar. In each dinuclear unit, both copper(II) ions are linked at two equatorial positions through a hydroxo bridge and a triatomic carboxylato bridge and at the axial position through a water molecule.The magnetic susceptibility measurements, measured from 5 to 300 K, revealed an antiferromagnetic interaction between the Cu(II) ions in compound 1 and a ferromagnetic interaction for compounds 2 and 3 with singlet-triplet energy gaps (J) of −56, 149 and 120 cm⁻¹, for compounds 1, 2 and 3, respectively.     

Nickel(II) complexes of di- and tri-substituted thiourea mono- and di-anions

Reaction of nickel(II) acetate, 1,2-bis(diphenylphosphino)ethane (dppe), and a di- or tri-substituted thiourea R¹NHC(S)R²R³ (R³ = H or alkyl) with trimethylamine in hot methanol gave cationic nickel(II) complexes containing N,S-chelated thiourea monoanion ligands [Ni{SC(NR²R³)NR¹}(dppe)]⁺, which can be readily isolated as their BPh₄⁻ salts. The X-ray crystal structure of [Ni{SC(NMe₂)NPh}(dppe)]⁺BPh₄⁻ is reported.     

Synthesis, spectroscopy, structure and photophysical properties of dinaphthylmethylarsine complexes of palladium(II) and platinum(II)

Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX₂L₂] (M = Pd, Pt; L = di(1-naphthyl)methylarsine = Nap₂AsMe and X = Cl, Br, I), [M₂Cl₂(μ-Cl)₂L₂], [PdCl(S₂CNEt₂)L], [Pd₂Cl₂(μ-OAc)₂L₂] and [MCl₂(PR₃)L] (PR₃ = PEt₃, PPr₃, PBu₃, PMePh₂) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (¹H, ¹³C, ³¹P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl₂(PEt₃)(Nap₂AsMe)] and of [Pd(S₂CNEt₂)₂], a follow-up product, were determined. The UV-vis spectra of [MX₂L₂] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX₂L₂] and [PtX₂L₂] are strongly luminescent in fluid solution and in the solid at ambient temperature.     

Ladder-like azido-bridged copper(II) complexes: Synthesis, X-ray structure and magnetic study

Two mixed-ligand copper(II) complexes [{Cu(L¹)(μ_1,3-N₃)}{Cu(L)(μ_1,3-N₃)(μ_1,1-N₃)}]_n (1) [HL¹ = 1-(N-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane; L = 2-(dimethylamino)-ethylamine] and [{Cu(L²)(μ_1,3-N₃)}{Cu(L)(μ_1,3-N₃)(μ_1,1-N₃)}]_n (2) [HL² = 1-(N-5-methoxy-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane] have been formed upon addition of aqueous solution of sodium azide to a methanolic solution of copper nitrate trihydrate and corresponding Schiff-base ligands. The ligands, HL¹ and HL² undergo partial hydrolysis of their imine bond during the course of reaction. Both the complexes contain single end-to-end (μ_1,3) azido bridged 1D infinite chains (rail) which propagate parallel to the crystallographic b-axis; neighboring chains are interconnected by pairs through double asymmetric end-on (μ_1,1) azido bridges (rung) to yield a ladder-like structure. In both complexes, rungs (end-on azido bridges) do not connect copper centers of the chains like in a regular ladder; instead they connect only the alternating copper sites of the 1D chain. In a chain the coordination environment around copper(II) ions are not the same: while the {Cu(L¹)(μ_1,3-N₃)} and {Cu(L²)(μ_1,3-N₃)} moieties have a penta-coordinated copper(II) center, the copper(II) ion of the neighboring {Cu(L¹)(μ_1,3-N₃)(μ_1,1-N₃)} or {Cu(L²)(μ_1,3-N₃)(μ_1,1-N₃)} moiety has an octahedral coordination environment. The variable temperature (2-300 K) magnetic susceptibility measurements showed that the magnetic interaction between the metal centers in complexes 1 and 2 is dominantly antiferromagnetic. The results of magnetic model are in good agreement with the experimental data.     

Oxalate, squarate and croconate complexes with bis(2-pyrimidylcarbonyl)amidatecopper(II): synthesis, crystal structures and magnetic properties

The preparation and magnetic properties of three copper(II) compounds of formulae [Cu₂(bpcam)₂(H₂O)₂(C₂O₄)] (1), [Cu₂(bpcam)₂(H₂O)₄(C₄O₄)] · 10 H₂O (2) and Cu₂(bpcam)₂(C₅O₅)(H₂O)₃ (3) [bpcam = bis(2-pyrimidyl)amidate, and are reported. The structures of two of them (1 and 2) have been solved by single crystal X-ray diffraction and consists of centrosymmetric discrete copper(II) dinuclear units bridged by bis-bidentate oxalate (1) and bis-monodentate squarate (2), with the bpcam group acting as a terminal tridentate ligand. Each copper atom in 1 exhibits a distorted elongated octahedral coordination geometry. Three bpcam nitrogen atoms and one oxalate oxygen define the basal plane while the other oxalate oxygen and a water molecule take up the axial positions. Each copper atom in 2 is in an elongated octahedral surrounding with three bpcam nitrogen atoms and one squarate oxygen in the equatorial plane and two water molecules in the axial positions. The intramolecular copper-copper separations are 5.677(1) (1) and 7.819(53) Å (2). Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K show the occurrence of weak ferromagnetic interactions through oxalato (J = +0.75 cm⁻¹) and squarato (J = +1.26 cm⁻¹), the Hamiltonian being defined by . These values are analyzed and discussed in the light of the available magneto-structural data for analogous systems. The quasi-Curie law observed in 3 (θ = −1.15 K) contrasts with the significant antiferromagnetic interaction through bis-chelating croconate in other structurally characterized croconate-bridged copper(II) complexes and rules out the presence of bridging croconate in this compound.     

Binuclear monofunctional platinum(II) complexes formed by hexaazamacrocyclic bisdien ligands: Crystal structure, DNA binding and cytotoxicity studies

Two binuclear 3N-chelated monofunctional Pt^II complexes, [Pt₂L1Cl₂]Cl₂ (complex III) and [Pt₂L2Cl₂]Cl₂ (complex IV) [L1 = 3,6,9,16,19,22-hexaazatricyclo[22.2.2.2^11,14]-triaconta-11,13,24,26(1),27,29-hexaene, L2 = 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1^11,15]-triaconta-1(29),11(30),12,14,25,27-hexaene] have been synthesized and structurally characterized. Structural determination revealed that each Pt^II center was coordinated by one chloride anion and three N atoms from each diethylenediamine motif. The Pt-Cl bonds in complex III are shorter than those found in complex IV. The rigid para- and meta-xylylene groups make the two complexes adopt a rigid boat-like conformation and a flexible twisted chair-like conformation, respectively. Moreover, complex III has higher tendency to bind with each other than complex IV. DNA binding studies demonstrated that complex IV could bind effectively with calf thymus DNA, possibly via platination of N7 of guanine residue, while no obvious DNA binding was observed for complex III. However, complex III displays a comparable cytotoxicity to cisplatin against HeLa cell line, while compound IV does not show any effective cell inhibition at low concentration. Therefore, the rigid spacers in complexes III and IV play a determining role in their anti-cancer activity and DNA binding ability.     

Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Palladium [PdCl₂(L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L¹), 2-(1-ethyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L²), 2-(1-octyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L³), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol (L⁴) were synthesised. The crystal and molecular structures of [PdCl₂(L)] (L = L², L³, L⁴) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl₂(L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L (L², L⁴) with [Pd(CH₃CN)₄](BF₄)₂, in the ratio 1M:2L, gave complexes [Pd(L)]₂(BF₄)₂. Treatment of [PdCl₂(L)] (L = L², L⁴) with NaBF₄ and pyridine (py) and treatment of the same complexes with AgBF₄ and triphenylphosphine (PPh₃) yielded [Pd(L)(py)₂](BF₄)₂ and [Pd(L)(PPh₃)₂](BF₄)₂ complexes, respectively. Finally, reaction of [PdCl₂(L⁴)] with 1 equiv of AgBF₄ yields [PdCl(L⁴)](BF₄).     

Synthesis, crystal structures and properties of novel zinc(II) and cadmium(II) polymeric and cyclic bimetallic complexes with fluconazole and dicarboxylate co-ligands

Four new fluconazole-bridged zinc(II) and cadmium(II) complexes with dicarboxylate co-ligands, namely [Zn(HFlu)(TPA)]_n (1), {[Cd(HFlu)₂(TPA)]·2CH₃OH}_n (2), [Zn(HFlu)₂(Suc)(H₂O)₂]·H₂O (3), and [Cd(HFlu)₂(Suc)(H₂O)₂]·H₂O (4), have been synthesized and characterized by elemental analysis, IR, TG, and single-crystal X-ray diffraction (HFlu = 2-(2,4-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol, H₂TPA = terephthalic acid, and H₂Suc = succinic acid). Complex 1 displays a 2-D corrugated network with common (4,4) topology, in which two types of grids constructed by two bridging TPA dianions and two HFlu ligands are found. Complex 2 shows an unusual (3,6) coordination layer consisting of alternative PMPM Cd-HFlu helical chains in which the Cd(II) nodes are also fixed by terephthalate dianions in a cis fashion. The isostructural complexes 3 and 4 have 20-membered dimeric macrocyclic motifs with the Zn···Zn and Cd···Cd distances of 11.258(2) and 11.528(2) Å, respectively. The fluorescence and thermal stability of complexes 1-4 have also been investigated.