Extended molecular networks based on Zn and Cd imparting N-substituted imidazole

Synthesis of complexes with the formulations [M(CPI)₂Cl₂] (M = Zn, 1; M = Cd, 4) and [M(CPI)₆](X)₂ (M = Zn, X = NO₃⁻, 2; X = ClO₄⁻, 3; M = Cd, X = NO₃⁻, 5; X = ClO₄⁻, 6) have been achieved from the reactions of MCl₂, M(NO₃)₂·xH₂O and M(ClO₄)₂·xH₂O (M = Zn, Cd) with 1-(4-cyanophenyl)-imidazole (CPI). Complexes 1-6 have been characterized by elemental analyses and spectral studies (IR, ¹H, ¹³C NMR, electronic absorption and emission). Molecular structures of 1, 2, 3 and 6 have been determined crystallographically. Weak interaction studies on the complexes revealed presence of various interesting motifs resulting from C-H···N, C-H···Cl and π-π stacking interactions. The complexes under study exhibit strong luminescence at ∼450 nm in DMSO at room temperature.     

Copper(I) complexes with Schiff base and 1,2-bis(diphenylphosphino)ethane as ligands: Synthesis, structure and catalytic properties for the amination of aryl halide

Some copper(I) complexes of the type [Cu(L)(dppe)]X (1-4) [where L = (3-trifluoromethylphenyl)pyridine-2-ylmethylene-amine; dppe = 1,2-bis(diphenylphosphino)ethane; X = Cl⁻, CN⁻, ClO₄⁻ and BF₄⁻] have been synthesized by the condensation of 3-aminobenzotrifluoride with 2-pyridinecarboxaldehyde followed by the reaction with CuCl, CuCN, [Cu(MeCN)₄]ClO₄ and [Cu(MeCN)₄]BF₄ in presence of dppe. The complexes 1-4 were then characterized on the basis of elemental analysis, IR, UV-Vis and ¹H NMR spectral studies. The representative complex of the series 4 has been characterized by single crystal X-ray diffraction which reveal that in complex the central copper(I) ion assumes the irregular pseudo-tetrahedral geometry. The catalytic activity of the complexes was tested and it was found that all the complexes worked as effective catalyst in the amination of aryl halide.     

Synthesis and reactivity of osmium (VI) nitrido complexes containing pyridine-carboxylato ligands

A series of osmium(VI) nitrido complexes containing pyridine-carboxylato ligands Os^VI(N)(L)₂X (L = pyridine-2carboxylate (1), 2-quinaldinate (2) and X = Cl (a), Br (1b and 2c) or CH₃O (2b)) and [Os^VI(N)(L)X₃]⁻ (L = pyridine-2,6-dicarboxylate (3) and X = Cl (a) or Br (b)) have been synthesised. Complexes 1 and 2 are electrophilic and react readily with various nucleophiles such as phosphine, sulfide and azide. Reaction of Os^VI(N)(L)₂X (1 and 2) with triphenylphosphine produces the osmium(IV) phosphiniminato complexes Os^VI(NPPh₃)(L)₂X (4 and 5). The kinetics of nitrogen atom transfer from the complexes Os^VI(N)(L)₂Br (2c) (L = 2-quinaldinate) with triphenylphosphine have been studied in CH₃CN at 25.0 °C by stopped-flow spectrophotometric method. The following rate law is obtained: −d[Os(VI)]/dt = k₂[Os(VI)][PPh₃]. Os^VI(N)(L)₂Cl (L = 2-quinaldinate) (2a) reacts also with [PPN](N₃) to give an osmium(III) dichloro complex, trans-[PPN][Os^III(L)₂Cl₂] (6). Reaction of Os^VI(N)(L)₂Cl (L = 2-quinaldinate) (2a) with lithium sulfide produces an osmium(II) thionitrosyl complex Os^II(NS)(L)₂Cl (7). These complexes have been structurally characterised by X-ray crystallography.     

Diverse coordination of polynuclear copper(II) complexes constructed from benzene tetracarboxylates

The reaction of aqueous solutions of the preformed 1:1 Cu(ClO₄)₂-polydentate amine with tetrasodium 1,2,4,5-benzene tetracarboxylate (Na₄bta) afforded three different types of polynuclear compounds. These include the tetranuclear complexes: [Cu₄(Medpt)₄(μ₄-bta)(ClO₄)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cu₄(pmdien)₄(μ₄-bta)(H₂O)₄](ClO₄)₄ (2), [Cu₄(Mepea)₄(μ₄-bta)(H₂O)₂](ClO₄)₄(3), [Cu₄(TPA)₄(μ₄-bta)](ClO₄)₄·10H₂O (4) and [Cu₄(tepa)₄(μ₄-bta)](ClO₄)₄·2H₂O (5), the di-nuclear: [Cu₂(DPA)₂(μ₂-bta)(H₂O)₂]·4H₂O (6), [Cu₂(dppa)₂(μ₂-bta)(H₂O)₂]·4H₂O (7) and [Cu₂(pmea)₂(μ₂-bta)]·14H₂O (8) and the trinuclear complex [Cu₃(dppa)₃(μ₃-bta)(H₂O)_2.25](ClO₄)₂·6.5H₂O (9) where Medpt = 3,3′-diamino-N-methyldipropylamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine, Mepea = [2-(2-pyridyl)ethyl]-(2-pyridylmethyl)methylamine, TPA = tris(2-pyridylmethyl)amine, tepa = tris[2-(2-pyridyl)ethyl)]amine, DPA = di(2-pyridymethyl)amine, dppa = N-propanamide-bis(2-pyridylmethyl)amine and pmea = bis(2-pyridylmethyl)-[2-(2-pyridylethyl)]amine. The complexes were structurally characterized by elemental analyses, spectroscopic techniques, and by X-ray crystallography for complexes 1, 2, 4, 6, 7 and 9. X-ray structure of the complexes reveal that bta⁴⁻ is acting as a bridging ligand via its four deprotonated caboxylate groups in 1, 2 and 4, three carboxylate groups in 9 and via two trans-carboxylates in 6 and 7. The complexes exhibit extended supramolecular networks with different dimensionality: 1-D in 2 and 4 due to hydrogen bonds of the type O-H···O, 2-D in 1 and 7, and 3-D network in 6 as a result of hydrogen bonds of the types N-H···O and O-H···O. Magnetic susceptibility measurements showed very weak antiferromagnetic coupling between the Cu^II ions in 1-5, 7-9 (|J| = 0.02-0.87 cm⁻¹) and weak ferromagnetic coupling for 6 (J = 0.08 cm⁻¹).     

Synthesis and characterisation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes [Ti(IV), Zr(IV), Hf(IV), La(III), Ce(III), Yb(III), Sn(II) and Fe(II)]

The preparation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes is described. These are of formula [M{η⁵-C₅H₄(BX)}Cl₃] [M = Ti and X = CAT (2a), CAT^t (2b) or CAT^tt (2c); X = CAT^tt and M = Zr (4a) or Hf (4b)], [M{η⁵-C₅H₄(BX)}₂Cl₂] [M = Zr, X = CAT (3a) or CAT^t (3c); or M = Hf, X = CAT (3b) or CAT^t (3d)], [M{(μ-η⁵-C₅H₃BCAT)₂ SiMe₂}Cl₂] [M = Zr (5a) or Hf (5b)], [M{η⁵-C₅H₃(BCAT)₂}Cl₃] [M = Zr (6a) or Hf (6b)], [M{η⁵-C₅H₄BCAT}₃(THF)] [M = La (7a), Ce (7b) or Yb (7c)], [Sn{η⁵-C₅ H₄(BCAT^t)}Cl](8) and [Fe{η⁵-C₅H₄(BCAT^t)}₂] (9). The abbreviations refer to BO₂C₆H₄-1,2 (BCAT) and the 4-Bu^t (BCAT^t) and the (BCAT^tt) analogues. The compounds 2a-9 have been characterised by microanalysis, multinuclear NMR and mass spectra. The single crystal X-ray structure of the lanthanum compound 7a is presented.     

Copper(II) complexes of bidentate ligands containing nitrogen and sulfur donors: Synthesis, structures, electrochemistry and catalytic properties

Two nitrogen and sulfur containing ligands, 1-methyl-4-((4-methylimidazol-5-yl)methylthio)benzene (NS-mim) (1) and 1-methyl-4-(2-pyridylmethylthio)benzene (NS-mpy) (2) were synthesized and a series of their Cu(II) complexes, 3-10, prepared. The imidazole-containing complexes (3-6) have the form [Cu(NS-mim)₂(solvent)₂](X)₂ where X = ClO₄, BF₄and [Cu(NS-mim)₂(Y)₂] where Y = Cl or Br and the pyridine-containing complexes (7-10) have the form [Cu(NS-mpy)₂]X₂ (where X = ClO₄, BF₄) and [Cu₂(NS-mpy)₂Y₄] (where Y = Cl or Br). These complexes were characterized by a combination of elemental analysis, FAB-MS and electrochemistry. The X-ray structure of the imidazole-containing [Cu(NS-mim)₂(DMF)₂](ClO₄)₂ (3) was determined and it showed the copper(II) coordinated only by the nitrogen donors while the sulfurs remain uncoordinated. In comparison, the X-ray structure of the pyridine-containing [Cu₂(NS-mpy)₂(Cl)₄] (9) shows a dinuclear copper(II) complex with the nitrogens and the sulfurs coordinated along with a terminal chloride and two μ-chloro atoms bridging the coppers. Cyclic voltammetry studies indicated that the complexes undergo quasi-reversible one-electron reductions in acetonitrile at potentials between 0.31 and 0.51 V versus SCE. The complexes were found to be active for the oxidation of di-tert-butyl catechol (DTBC) with the rate dependent on the ligand and the counterion present.     

Interaction of Pt(II) and Pd(II) complexes of terpyridine with 1-methylazoles: A combined experimental and density functional study

The synthesis and characterization of several complexes of the composition [{M(terpy)}_n(L)](ClO₄)_m (M = Pt, Pd; L = 1-methylimidazole, 1-methyltetrazole, 1-methyltetrazolate; terpy = 2,2′:6′,2″-terpyridine; n = 1, 2; m = 1, 2, 3) is reported and their applicability in terms of a metal-mediated base pair investigated. Reaction of [M(terpy)(H₂O)]²⁺ with 1-methylimidazole leads to [M(terpy)(1-methylimidazole)](ClO₄)₂ (1: M = Pt; 2: M = Pd). The analogous reaction of [Pt(terpy)(H₂O)]²⁺ with 1-methyltetrazole leads to the organometallic compound [Pt(terpy)(1-methyltetrazolate)]ClO₄ (3) in which the aromatic tetrazole proton has been substituted by the platinum moiety. For both platinum(II) and palladium(II), doubly metalated complexes [{M(terpy)}₂(1-methyltetrazolate)](ClO₄)₃ (4: M = Pt; 5: M = Pd) can also be obtained depending on the reaction conditions. In the latter two compounds, the [M(terpy)]²⁺ moieties are coordinated via C5 and N4. X-ray crystal structures of 1, 2, and 3 are reported. In addition, DFT calculations have been carried out to determine the energy difference between fully planar [Pd(mterpy)(L)]²⁺ complexes Ip-IVp (mterpy = 4′-methyl-2,2′:6′,2″-terpyridine; L = 1-methylimidazole-N3 (I), 1-methyl-1,2,4-triazole-N4 (II), 1-methyltetrazole-N3 (III), or 3-methylpyridine-N1 (IV)) and the respective geometry-optimized structures Io-IVo. Whereas this energy difference is larger than 70 kJ mol⁻¹ for compounds I, II, and IV, it amounts to only 0.8 kJ mol⁻¹ for the tetrazole-containing complex III, which is stabilized by two intramolecular C-H?N hydrogen bonds. Of all complexes under investigation, only the terpyridine-metal ion-tetrazole system with N3-coordinated tetrazole appears to be suited for an application in terms of a metal-mediated base pair in a metal-modified oligonucleotide.     

Three trinuclear Cu-M-Cu (M = Co, Ni and Zn) complexes including macrocyclic oxamido bridge: Synthesis, structures and magnetic properties

Based on the complex ligand (CuL H2L = 2,3-dioxo-5,6:15,16-dibenzo-1,4,8,13-tetraazacyclotetradeca-7,13-diene), which includes macrocyclic oxamido bridge, three trinuclear complexes were prepared. They are of the formula [(CuL)₂M(ClO₄)₂] (M = Co(1), Ni(2)) and [(CuL)₂Zn(CH₃OH)₂] · (ClO₄)₂ (3). The crystal structures of the three complexes have been determined and the M(II) of the three complexes all exist on the mirror plane. Complex 1 is the first Cu-Co complex bridged by oxamido. Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −28.12 cm⁻¹ for 1, J = −42.88 cm⁻¹ for 2, and J = −2.13 cm⁻¹ for 3.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Hydrolytic cleavage of double-strand DNA by the water-soluble dicobalt(III) complexes of 1,4,7-Triazacyclononane-N-acetate

Three water-soluble dicobalt(III) complexes, [Co₂L₂(µ-OH)₂](ClO₄)₂·5H₂O (1), [Co₂L₂(µ-OH)₂](ClO₄)₂·CH₃OH·H₂O(2); [Co₂L₂(µ-OH)₂](ClO₄)₂·4H₂O(3) (L = 1,4,7-triazacyclononane-N-acetate monoanion), were prepared to serve as nuclease mimics. The complexes were characterized by X-ray, IR and UV-vis spectroscopy as well as ESI-MS. Three complexes exhibit similar structures, just with different solvent molecules. The electrospray mass spectrum of 1 in solution indicates that dinuclear ion [Co₂L₂(µ-OH)₂-H⁺] ⁺ (4) is the active species. In the absence of any reducing agent, the complexes cleave plasmid pBR322 DNA was performed and its hydrolytic mechanism was demonstrated with radical scavengers, anaerobic reaction and T4 ligase. The kinetic aspects of DNA cleavage under pseudo- or true-Michaelis-Menten conditions are also detailed, kinetic parameters (k_cat, K_M) were calculated to be 3.57 h^− 1, 6.92 × 10^− 4 M; 0.28 h^− 1, 1.9 × 10^− 5 M for 4, respectively.     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

Organocyanide coordination chemistry: Syntheses, structural characterisations and magnetic properties of copper (II) complexes with a di-imine/pyridine ligand

The reactions between the copper (II) salts [CuXL]PF₆ (L: 2,6-[1-(2,6-diisopropylphenylimino)ethyl]pyridine) (X = Cl 1, X = Br 2) and LiTCNQ, in a DMF/water mixture, or Et₃NH(TCNQ)₂, in acetone, produced the new complexes [CuXL(TCNQ)] (X = Cl 3, X = Br 4). For both compounds, crystallographic studies have clearly evidenced the existence of dimeric complexes [{CuClL}(TCNQ)]₂ owing to π-π overlap between two adjacent TCNQ⁻ radical anions. Compound 1 reacted with Et₄N(C₁₀N₇) to afford the mononuclear derivative [CuClL(C₁₀N₇)] (5), while its reaction with K₂C₁₀N₆ produced the dinuclear complex [(CuClL)₂(C₁₀N₆)] (6). The crystal structures of complexes 5 and 6 have been determined by X-ray crystallography. Magnetic studies have revealed that compound 6 displays weak antiferromagnetic interactions between the two metal centres, conversely compounds 3 and 5 exhibit purely paramagnetic behaviours.     

From infinite tubular arrays to discrete molecules and back: An example of reversible ring-opening polymerization in silver(I)-diphosphazane chemistry

The reaction of AgX with the diphosphazane ligand, PrⁱN(PPh₂)₂ (L) gives the polymeric complexes, [Ag₂(μ-X)₂(μ-L)]_n (X = NO₃1a or OSO₂CF₃1b). Single crystal X-ray analysis of 1a reveals a novel structural motif formed by interlinking of giant 40-membered rings; the diphosphazane ligand L adopts a unique ‘C_s’ geometry. These polymeric complexes exhibit a completely reversible ring-opening polymerization-depolymerization relationship with the dinuclear and mononuclear complexes, [{Ag(μ-L)(X)}₂] (X = NO₃2a, X = OSO₂CF₃2b) and [Ag(κ²-L)₂]X (X = NO₃3a, X = OSO₂CF₃3b).     

Synthesis, structures, and magnetic properties of dicopper(II) and dinickel(II) complexes with a new bis(macrocycle), 7,7-(2-hydoxypropane-1,3-diyl)bis{3,7,11,17-tetraazabicyclo[11.3.1]- heptadeca-1(17),13,15-triene}

A new bis(macrocycle) ligand, 7,7^′-(2-hydoxypropane-1,3-diyl)-bis{3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene} (HL), and its dicopper(II) ([Cu₂(HL)Cl₂](NO₃)₂ · 4H₂O (4a), [Cu₂(HL)I₂]I₂ · H₂O (4b)) and dinickel(II) ([Ni₂(L)(OH₂)](ClO₄)₃ (5a), [Ni₂(L)(OH₂)]I₃ · 2H₂O (5b), [Ni₂(L)N₃](N₃)₂ · 7H₂O (5c)) complexes have been synthesized. The alkoxide bridged face-to-face structure of the dinickel(II) complex 5c has been revealed by X-ray crystallography, as well as the “half-opened clamshell” form of the bis(macrocyclic) dicopper(II) complex 4b. Variable temperature magnetic susceptibility studies have indicated that there exists intramolecular antiferromagnetic coupling (J=−33.8 cm⁻¹ (5a), −32.5 cm⁻¹ (5b), and −29.7 cm⁻¹ (5c)) between the two nickel(II) ions in the nickel(II) complexes.     

Dicyanamido-metal(II) complexes. Part 4: Synthesis, structure and magnetic characterization of polynuclear Cu(II) and Ni(II) complexes bridged by μ-1,5-dicyanamide

The one pot aqueous reaction of M(ClO₄)₂ (M = Cu²⁺ or Ni²⁺) with N-methylbis[2-(2-pyridylethyl)]amine (MeDEPA) and N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine (bpmen) and 1,4,7,10-tetraazacyclododecane (cyclen) in presence of sodium dicyanamide (Nadca) yielded dicyanamido-bridged polynuclear complex {[Cu(MeDEPA)(μ-1,5-dca)]ClO₄}_n (1), and two dinuclear complexes [Cu₂(bpmen)₂(μ-1,5-dca)]₂(ClO₄)₅dca (2) and [Ni(cyclen)(μ-1,5-dca)]₂(ClO₄)₂ (3). These complexes were characterized by IR and UV-Vis spectroscopy. Room temperature single-crystal X-ray studies have confirmed that the Cu(II) centers in 1 and 2 adopt geometries that are more close to trigonal bipyramidal (TBP) in 1 and close to square pyramidal (SP) in 2, whereas in 3, the Ni(II) centers are located in octahedral environment with doubly bridged μ-1,5-dca bonding mode. The intermolecular M···M distances in these complexes are in the range of 7.3-8.6 Å. Variable temperature magnetic susceptibility studies have confirmed that the dca-bridges mediate very weak antiferromagnetic interaction between the M(II) centers with J values of −0.35, −0.18 and −0.43 cm⁻¹ for 1, 2 and 3, respectively. The results are compared and discussed in the light of other related bridged μ-1,5-dca Cu(II) and Ni(II) complexes.     

Binuclear manganese(III) complexes of an unsymmetric pyrazolate-based compartmental ligand with hard donor set

The synthesis, crystal structure and magnetic properties of manganese(III) binuclear complexes [Mn^III₂(L-3Н)₂(CH₃ОH)₄]·2CH₃ОH (1) and [Mn^III₂(L-3Н)₂(Py)₄]·2Py (2) (L = 3-[(1E)-N-hydroxyethanimidoyl]-4-methyl-1H-pyrazole-5-carboxylic acid) are reported. The ligand contains two distinct donor compartments formed by the pyrazolate-N and the oxime or the carboxylic groups. The complexes were characterized by X-ray single crystal diffraction, revealing that both 1 and 2 consist of dinuclear units in which the two metal ions are linked by double pyrazolate bridges with a planar {Mn₂N₄} core. Cryomagnetic measurements show antiferromagnetic interaction with g = 1.99, J = −3.6 cm⁻¹, Θ = −2.02 K for 1 and g = 2.00, J = −3.7 cm⁻¹, Θ = 1.43 K for 2.     

Synthesis, structure, and catalytic activity of chiral silver(I) and copper(II) complexes with biaryl-based nitrogen-containing ligands

A series of chiral Ag(I) and Cu(II) complexes have been prepared from the reaction between AgX (X = NO₃, PF₆, OTf) or CuX₂ (X = Cl, ClO₄) and chiral biaryl-based N-ligands. The rigidity of the ligand plays an important role in the Ag(I) complex formation. For example, treatment of chiral N₃-ligands 1-3 with half equiv of AgX (X = NO₃, PF₆, OTf) gives the chiral bis-ligated four-coordinated Ag(I) complexes, while ligand 4 affords the two-coordinated Ag(I) complexes. Reaction of AgX with 1 equiv of chiral N₄-ligands 5, 7, 8 and 10 gives the chiral, binuclear double helicate Ag(I) complexes, while chiral mono-nuclear single helicate Ag(I) complexes are obtained with N₄-ligands 6 and 9. Treatment of either N₃-ligand 1 or N₄-ligand 9 or 10 with 1 equiv of CuX₂ (X = Cl, ClO₄) gives the mono-ligated Cu(II) complexes. All the complexes have been characterized by various spectroscopic techniques, and elemental analyses. Seventeen of them have further been confirmed by X-ray diffraction analyses. The Cu(II) complexes do not show catalytic activity for allylation reaction, in contrast to Ag(I) complexes, but they do exhibit catalytic activity for Henry reaction (nitroaldol reaction) that Ag(I) complexes do not.     

Mo(II) complexes: A new family of cytotoxic agents?

Several molybdenum complexes, [Mo(η³-C₃H₅)X(CO)₂(N-N)] (N-N = 1,10-phenanthroline, phen: X = CF₃SO₃T1, X = Br B1, X = Cl C1; N-N = 2,2′-bipyridyl, X = CF₃SO₃T2, X = Br B2) and [W(η³-C₃H₅)Br(CO)₂(phen)] (W1) have been synthesized and characterized. Their antitumor properties have been tested in vitro against human cancer cell lines cervical carcinoma (HeLa) and breast carcinoma (MCF-7) using a metabolic activity test (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT), leading to IC₅₀ values ranging from 3 to 45 μM, approximately. Most complexes exhibited significant antitumoral activity. Complexes B1 and T2 were chosen for subsequent studies aiming to understand their mechanism of action. Cellular uptake of molybdenum and octanol/water partition assays revealed that both B1 and T2 exhibit a selective uptake by cells and intermediate partition coefficients. The binding constants of B1 and T2 with ct DNA, as determined by absorption titration, are 2.08 (± 0.98) × 10⁵ and 3.68 (± 2.01) × 10⁵ M^− 1, respectively. These results suggest that they interact with DNA changing its conformation and possibly inducing cell death, and may therefore provide a valuable tool in cancer chemotherapy.     

Transition metal complexes based on pyridine ligand containing both bis(2-pyridyl) and 1,3-dithiole-2-ylidene units: Syntheses, structures, and magnetic studies

Two new mononuclear spin-crossover iron(II) complexes, [FeL₂(NCS)₂] · H₂O (1) and [FeL₂(NCSe)₂] (2), have been synthesized from the reaction of the versatile ligand 4,5-bis(2-cyanoethylthio)-2-bis(2-pyridyl)methylene-1,3-dithiole (L), Fe(ClO₄)₂, and KNCX (X = S/Se). Reactions of L with Cu^II or Co^II salts afford one mononuclear complex [CuL(hfac)₂] · CH₃OH (hfac = hexafluoroacetylacetonate) (3), one dinuclear complex [(CuLCl)₂(μ-Cl)₂] · CH₃OH (4), and two 1D chain species, [CuL₂]_n(BF₄)_2n (5) and [CoL₂]_n(ClO₄)_2n · 2nCH₂Cl₂ (6). The crystal structures of complexes 1 and 3-6 have been determined by X-ray crystallography. Short intermolecular S?S contacts between neighboring 1D arrays are observed in 5 and 6, which lead to the formation of the 2D structure. The magnetic properties are studied, and antiferromagnetic couplings between the Cu^II centers across the chloride bridges have been found in 4 (J = 2.04 cm^-1). Spin-crossover behaviors between high and low spin states are observed at T_1/2 = 80 K for 1 and T_1/2 = 300 K for 2, respectively.     

Synthesis, crystal structures, DNA-binding properties, cytotoxic and antioxidation activities of several new ternary copper(II) complexes of N,N′-(p-xylylene)di-alanine acid and 1,10-phenanthroline

Three novel ternary copper(II) complexes, [Cu₂(phen)₂(l-PDIAla)(H₂O)₂](ClO₄)₂·2.5H₂O (1), [Cu₄(phen)₆(d,l-PDIAla)(H₂O)₂](ClO₄)₆·3H₂O (2) and [Cu₂(phen)₂(d,l-PDIAla)(H₂O)](ClO₄)₂·0.5H₂O (3) (phen = 1,10-phenanthroline, H₂PDIAla = N,N’-(p-xylylene)di-alanine acid) have been synthesized and structurally characterized by single-crystal X-ray crystallography and other structural analysis. Spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements indicate that the three compounds, especially the complex 3, strongly bind to calf-thymus DNA (CT-DNA). The intrinsic binding constants of the ternary copper(II) complexes with CT-DNA are 0.89 × 10⁵, 1.14 × 10⁵ and 1.72 × 10⁵ M⁻¹, for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the HeLa (Cervical cancer), HepG2 (hepatocarcinoma), HL-60 cells (myeloid leukemia), A-549 cells (pulmonary carcinoma) and L02 (liver cells). Investigations of antioxidation properties show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals.