Synthesis, characterization and luminescence properties of copper(I) complexes containing 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one and triphenylphosphine as ligands

Some copper(I) complexes of the formula [Cu(L)(PPh₃)₂]X (1-4) [where L = 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one; PPh₃ = triphenylphosphine; X = Cl⁻, NO₃⁻, ClO₄⁻ and BF₄⁻] have been prepared and 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 the complex the central copper(I) ion assumes the irregular distorted-tetrahedral geometry. Cyclic voltammetry of the complexes indicate a quasireversible redox behavior corresponding to Cu(II)/Cu(I) couple. All the complexes exhibit intraligand (π → π^∗) fluorescence with high quantum yield in dichloromethane solution.     

Deciphering the bonding mode of the trihalide ligands in a series of halogen carrier homo- and hetero-trihalide Cu(II) Schiff base complexes

Electronic structure calculation techniques (DFT) have been used to decipher the bonding of the trihalide ligands in a series of homo- and hetero-trihalide Cu(II) Schiff base complexes formulated as [Cu(RdienR)(X)(XY₂)] (RdienR = Schiff base; R = furan, thiophene or pyrrol; X = Cl or Br; Y = Cl, Br or I). The association of the incoming Y₂ halogen molecule with one of the halide X ligands of the precursor [Cu(RdienR)(X)₂] complexes alters their distorted trigonal bipyramidal stereochemistry which is transformed to a distorted square pyramidal geometry. The bonding mechanism between the halogen Y₂ molecule and the halide X ligand was thoroughly explored by means of various electronic parameters and charge decomposition analysis techniques. The bond dissociation energy of the Cu–XY₂ bond, BDECu–XY₂${\text{BDE}}_{\text{Cu}''–''{\text{XY}}_2}$, was estimated in the range of 61.9–68.4 kcal/mol, while the bond dissociation energy of the X–Y₂ bond, BDECu–XY₂${\text{BDE}}_{\text{Cu}''–''{\text{XY}}_2}$, was found in the range of 10.6–12.5 kcal/mol. It was found that the X?Y₂ interactions correspond to weak hyperconjugative donor–acceptor interactions between a non-bonding n(X) molecular orbital (donor orbital) localized on the coordinated halide X ligand and an antibonding σ^∗(Y–Y) molecular orbital (acceptor orbital) localized on the Y₂ halogen molecule. The n(X) → σ^∗(Y–Y) donor–acceptor interactions are associated with a second-order perturbation stabilization energy, ΔE(2) of 34.5–52.5 kcal/mol. The loose association of the halogen molecules with the coordinated halide ligand renders the [Cu(RdienR)(X)(XY₂)] complexes good halogen carrier molecules.     

Mixed-ligand ternary complexes of potentially pentadentate but functionally tridentate Schiff base chelates

The potentially pentadentate chelate 2,6-diacetylpyridine-bis(N-methyl-S-methyldithiocarbazate) (Nmedapsme) has been synthesized and structurally characterized by X-ray diffraction. Its reactions with nickel(II) salts did not lead to pentadentate coordinated ligand complexes but ternary complexes of general formula, [Ni(Nmedapsme)(nmesme)L]X·H₂O (L = Br⁻, I⁻; X = I⁻, BF₄⁻) where Nmedapsme binds as a tridentate and nmesme = N-methyl-S-methyldithiocarbazate. The related ternary nickel(II) complexes of formula, Ni(Nmedapsme)(nmetsc)Br₂ has also been prepared and characterized. X-ray crystal structures of [Ni(Nmedapsme)(nmesme)I]I·H₂O and [Ni(Nmedapsme)(nmesme)Br]BF₄·H₂O revealed that, in these complexes, the Nmedapsme ligand acts as a tridentate NNN donor while the distal S-donors are not coordinated. The bidentate (NS) ligand, nmesme coordinates to the nickel(II) ion via the amino nitrogen and the thione sulfur atoms, the sixth coordination site is occupied by an anion. In both complexes, the nickel(II) ion adopts a distorted octahedral configuration. The complex [Cu(nmesme)₂(ONO₂)]NO₃ was obtained from an unsuccessful attempt to complex copper(II) with Nmedapsme. Hydrolysis of the parent Schiff base Nmedapsme occurred during complexation. An X-ray crystallographic structure analysis shows that the complex, [Cu(nmesme)₂(ONO₂)]NO₃ has an approximately square-pyramidal geometry with the two nmesme ligands coordinated to the copper(II) ion as NS bidentate chelating agents via the amino nitrogen and thione sulfur atoms and the fifth coordination position of copper(II) is occupied by a monodentate nitrate ligand.     

Cu(I) and Ag(I) complexes of chalcogenide derivatives of the organometallic ligand dppf and the dppa analogue

New Cu(I) and Ag(I) complexes were prepared by reaction of [M(NCCH₃)₄][X] (M = Cu or Ag; X = BF₄ or PF₆) with the bidentate chalcogenide ligands Ph₂P(E)NHP(E)Ph₂ (E = S, S₂dppa; E = Se, Se₂dppa), and dpspf (1,1′-bis(diphenylselenophosphoryl)ferrocene). Copper and silver behaved differently. While three molecules of either S₂dppa and Se₂dppa bind to a distorted tetrahedral Cu₄ cluster, with deprotonation of the ligand, 1:2 complexes of the neutral ligands are formed with Ag(I), with a tetrahedral coordination of the metal. The [Cu₄{Ph₂P(Se)NP(Se)Ph₂}₃]⁺ clusters assemble as dimers, held together by weak Se?Se distances interactions. Another dimer was observed for the [Ag(dpspf)]⁺ cation, with two short Ag?Se distances. DFT and MP2 calculations indicated the presence of attracting interactions, reflected in positive Mayer indices (MI). The electrochemistry study of this species showed that both oxidation and reduction took place at silver.     

Synthesis, structures, electrochemistry and electrocatalysis of two novel copper(II) complexes constructed with aromatic polycarboxylates and dipyrido[3,2-d:2′,3′-f]quinoxaline

Two novel coordination polymers [Cu₃(1,3-BDC)₄(Dpq)₂] (1) and [Cu₂(BTC)(OH)(Dpq)₂] · H₂O (2), have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands 1,3-H₂BDC (1,3-H₂BDC = 1,3-benzenedicarboxylate) or H₃BTC (H₃BTC = 1,3,5-benzenetricarboxylate), chelating ligand Dpq (Dpq = dipyrido[3,2-d:2′,3′-f]quinoxaline), and copper chloride. X-ray diffraction analysis reveals that each trinuclear Cu^II cluster is bridged by two coordination modes of 1,3-BDC ligands to form one-dimensional (1-D) chain structure in complex 1. Complex 2 possesses a two-dimensional (2-D) layer network composed of dinuclear [Cu₂(OH)(Dpq)₂] unit and bridging ligand BTC. The adjacent chains for 1 or the adjacent layers for 2 are further linked by π-π stacking interactions to form the three-dimensional (3-D) supramolecular frameworks. Moreover, the electrochemical properties of the two copper(II) complexes bulk-modified carbon paste electrodes (Cu-CPEs: 1-CPE and 2-CPE) have been studied, and the results indicate that both Cu-CPEs give one-electron quasi-reversible redox waves in potential range of 600 to −400 mV due to the metal copper ion Cu(II)/Cu(I). The Cu-CPEs have good electrocatalytic activities toward the reduction of nitrite and bromate in 0.1 M pH 2 phosphates buffer solution, and have remarkable long term stability and especially good surface renewability by simple mechanical polishing in the event of surface fouling, which is important for practical application.     

Synthesis and coordination chemistry of new tetradentate N2S2 donor Schiff-base ligand ca2-dapte: Mononuclear and dinuclear copper(I) complexes [Cu(ca2dapte)]ClO4 and [{Cu(PPh3)(X)}2(ca2dapte)] (X = I and Br)

A mononuclear copper(I) complex, [Cu(ca₂dapte)]ClO₄ (1), and two dinuclear copper(I) complexes, [{Cu(PPh₃)(X)}₂(ca₂dapte)] (X = I (2) and Br (3)), of a new tetradentate N₂S₂ donor Schiff-base ligand ca₂dapte have been prepared (ca₂dapte = N,N′-bis(trans-cinnamaldehyde)-1,2-di(o-iminophenylthio)ethane). These compounds have been characterized by elemental analyses (CHN), FT-IR, UV–Vis and ¹H NMR spectroscopy. The crystal structures of these copper(I) complexes have been determined by single-crystal X-ray diffraction. The coordination geometry around Cu(I) centers in these complexes is a distorted tetrahedron. The ca₂dapte is coordinated to Cu(I) as a tetradentate ligand in 1, while it acts as a bis-bidentate bridging ligand in 2 and 3.     

The supramolecular chemistry of metal complexes with heavily substituted imidazoles as ligands: Cobalt(II) and zinc(II) complexes of 1-methyl-4,5-diphenylimidazole

An investigation of the M^II/X⁻/L [M^II = Co, Ni, Cu, Zn; X⁻ = Cl⁻, Br⁻, I⁻, NCS⁻, NO₃⁻, N₃⁻, CH₃COO⁻; L = 1-methyl-4,5-diphenylimidazole] general reaction system towards the detailed study of the intermolecular interactions utilized for controlling the supramolecular organization and the structural consequences on the structures produced has been initiated. Three representative complexes with the formulae [Co(NO₃)₂(L)₂] (1), [Zn(NO₃)₂(L)₂] (2) and [Co(NCS)₂(L)₂]·EtOH (3·EtOH) have been synthesized and characterized by spectroscopic methods and single-crystal X-ray analysis. Compounds 1 and 2 are isomorphous (tetragonal, I4₁cd) with their metal ions in a severely distorted octahedral Co/ZnN₂O₄ environment, while 3·EtOH crystallizes in P2₁/c with a tetrahedral CoN₄ coordination. The structural analysis of 1, 2 and 3·EtOH reveals a common mode of packing among neighbouring ligands (expressed through intramolecular π–π interactions between the 4,5-diphenylimidazole moieties), enhancing thus the rigidity and stability of the complexes. The bent coordination of the two isothiocyanates in 3 [Co–NCS angles of 173.8(2) and 160.8(2)°] seems to be caused by intermolecular hydrogen bonding and crystal packing effects.     

Dinuclear and polynuclear silver(I) saccharinate complexes with 1,3-diaminopropane and N-methylethylenediamine constructed from Ag?C interactions

New dinuclear and polynuclear Ag(I) complexes with the formula of [Ag₂(sac)₂(pen)₂] (1) and [Ag₂(sac)₂(nmen)]_n (2), (sac = saccharinate, pen = 1,3-diaminopropane, nmen = N-methylethylenediamine) have been synthesized and characterized by IR spectroscopy and thermal (TG/DTG, DTA) analysis. In addition, their structures were determined by single crystal X-ray diffraction technique. In 1, Ag(I) ions are doubly bridged by two pen ligands, besides pen ligands exhibit an interesting coordination mode by binding bridging ligand. Sac ligands connect to silver atom through its imino N atom. Furthermore, each Ag(I) ion exhibits a T-shaped coordination geometry. In 2, Ag(I) coordination environment is again T-shaped, including weak Ag-Ag bonds. The sac exhibits bidentate bringing mode, involving its imino nitrogen and carbonyl oxygen atoms, besides, bridging of Ag(I) centres by sac ligands results in argentophilic contacts. The polymeric units are assembled into two-dimensional networks by hydrogen bonds, C-H?π stacking interactions, weak Ag?C_sac (η²) and Ag?O interactions.     

A new family of pyrazolyl-based anionic bidentate ligands and crystal structure of bis(N-phenyl-2-pyrazolyl-1-carboximidothioato)copper(II)

Three new N,S-donor bidentate pyrazolyl-based ligands abbreviated as [PhNCSPz]⁻, 1, [PhNCSPz^Me2]⁻, 2, and [PhNCSPz^Ph2]⁻, 3, have been synthesized in THF by direct mixing of phenylisothiocyanide with suspension of appropriate sodium-pyrazolate salts and characterized by the common spectroscopic and analytical methods. The Cu(II) complexes of these anionic chelate ligands have been characterized and the crystal structure of Cu(PhNCSPz)₂, 4, has been determined. The space group of complex is P2₁c, with a = 5.9313(3), b = 21.206(1) Å, c = 8.0667(4) Å, β = 103.822(1)°.     

Mononuclear Cu and dinuclear Cu–Ln complexes of benzimidazole based ligands including N and O donors: Syntheses,characterization, X-ray molecular structures and magnetic properties

The synthesis of two mononuclear precursor copper complexes, [(HL²)₂Cu], 1, and [(HL³)₂Cu]·H₂O, 2, and three dinuclear Cu–Ln complexes, [(HL¹)₂Cu(CH₃CN)₂Gd(NO₃)₃], 3, [(HL³)₂CuGd(NO₃)₃]·2(H₂O), 4, and [(HL³)₂CuTb(NO₃)₃]·2(H₂O), 5, based on the ligands H₂L¹ (4-bromo-2-[1-(5-bromo-2-hydroxy-3-methoxybenzyl)-1H-benzimidazol-2-yl]-6-methoxyphenol), H₂L² (2-(1H-benzimidazol-2-yl)-4-bromo-6-methoxyphenol) and H₂L³ (2-(1H-benzimidazol-2-yl)-6-methoxyphenol) are described in this contribution. The X-ray crystal structures of H₂L², 1, 3, 4, and 5 have been solved. The novel ligand H₂L² crystallizes with two independent molecules in the asymmetric unit; several intermolecular hydrogen contacts connect alternate independent H₂L² molecules into chains developing along c. In complex 1, two (HL²)⁻ ligands chelate the copper ion through their imidazolyl nitrogen and phenoxo oxygen atoms, in a relative head to tail arrangement. The molecular structure of 3 is similar to those of the previously reported Cu–Ln complexes of H₂L¹. In the isostructural complexes 4 and 5, two HL³ ligands sandwich one Cu²⁺ ion through their N,O sites and one Ln³⁺ ion through their O₂ site, implying a relative head to head arrangement, at variance with the relative head to tail arrangement of HL² in the mononuclear copper precursor 1. The magnetic properties of 1, 3, 4, and 5 have been investigated. Extended intermolecular antiferromagnetic interactions operate in complex 1 ((J_Chain = −0.8(1) cm⁻¹). Ferromagnetic interactions between Gd (S = 7/2) and Cu (S = 1/2) centers operate in complexes 3 and 4, leading to an S = 4 ground state (J_CuGd = 7.2(2) cm⁻¹ for 3 and J_CuGd = 6.5(2) cm⁻¹ for 4). Depopulation of the Tb Stark levels, preclude obtaining reliable information on the presence and sign of the Cu–Tb interaction in 5. These new complexes are complementary to those previously reported: the Cu–O₂–Gd core is planar while deformations are borne by the ligands at variance with previous examples where the constraints were located at the Cu–O₂–Gd core. The presence of two independent ligands in the Cu,Gd coordination spheres confers a degree of freedom greater than that allowed by a unique tetradentate ligand. As a result, the strength of the magnetic interaction is not solely related to the dihedral angle between the CuOO and GdOO planes in the central core.     

Electrochemical,magnetic, catalytic and DNA cleavage studies of binuclear copper(II) complexes derived from pendant substituted tetraaza macrobicyclic compartmental ligands

A series of macrobicyclic unsymmetrical binuclear copper(II) complexes of compartmental ligands were synthesized from the Schiff base condensation of 1,8[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-1,4,8,11- tetraaza-5,5,7,12,12,14-hexa methylcyclotetradecane with diamines like 1,2-diamino ethane, 1,3-diamino propane, 1,4-diaminobutane, 1,2-diaminobenzene and 1,8-diaminonaphthalene. The complexes were characterized by elemental and spectral analysis. Electrochemical studies of the copper(II) complexes show two irreversible one-electron reduction processes around E¹_pc = −0.70 to −1.10 V and E²_pc = −0.98 to −1.36 V. ESR spectra of the binuclear copper(II) complexes show a broad signal at g = 2.10 and μ_eff values in the range 1.46–1.59 BM, which convey the presence of antiferromagnetic coupling. Cryomagnetic investigation of the binuclear complexes [Cu₂L³(ClO₄)](ClO₄) and [Cu₂L⁴(ClO₄)](ClO₄) show that the observed −2J values are 144 and 216 cm⁻¹, respectively. The observed initial rate (V_in) for the catalytic hydrolysis of p-nitrophenyl phosphate by the binuclear copper(II) complexes were in the range 1.8 × 10⁻⁵ to 2.1 × 10⁻⁵ Ms⁻¹. The initial rate (V_in) for the catalytic oxidation of catechol to o-quinone by the binuclear copper(II) complexes were in the range 2.7 × 10⁻⁵ to 3.5 × 10⁻⁵ Ms⁻¹. The copper(II) complexes have been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II.     

Synthesis,spectroscopic properties,structural characterization and electrochemistry of mixed ligand complexes of copper(I) halide with PPh3 and naphthylazoimidazole

The reaction of CuX (X = Cl, Br, I) with a mixture of PPh₃ and 1-alkyl-2-(naphthyl-α/β-azo)imidazole has synthesized mixed ligand complexes of the composition, [Cu(α/β-NaiR)(PPh₃)X]. The spectroscopic characterization (IR, UV–Vis, ¹H NMR) supports this formulation. The single crystal X-ray diffraction study of [Cu((α-NaiMe)(PPh₃)I] (7a) (α-NaiMe = 1-methyl-2-(naphthyl-α-azo)imidazole) shows a distorted tetrahedral geometry about Cu(I). Cyclic voltammograms of the complexes show a high potential Cu(II)/Cu(I) couple and azo reductions. The [Cu(α/β-NaiR)(PPh₃)I] complexes show an additional oxidative response at 0.4 V that is assigned to I/I⁻ A sharp anodic peak at ∼−0.2 V is assigned to the oxidation of metallic Cu, deposited on electrode surface upon scanning to the negative side of the SCE. DFT and TD-DFT computations of [Cu((α-NaiMe)(PPh₃)I] (7a), [Cu((α-NaiMe)(PPh₃)I]⁺ (7a⁺) and [Cu((α-NaiMe)(PPh₃)I]⁻ (7a⁻) were carried out to examine the electronic configuration and to explain the spectral and redox properties of the complexes.     

Kinetic investigation of a PC(sp)P pincer palladium (II) complex in the Heck reaction

An investigation of the kinetics of the Heck reaction between 4-iodoanisole and styrene catalysed by {cis-1,3-bis[(di-tert-butylphosphino)methyl]-cyclohexane} palladium (II) iodide (1) has been performed in DMF-d₇ solution. Based on mercury poisoning experiments a heterogeneous palladium catalyst formed from the pre-catalyst is proposed. Saturation behaviour with respect to the olefin concentration suggests a mechanism consisting of a pre-equilibrium association of the olefin followed by a rate determining reaction with aryl halide. The equilibrium constant for the olefin association, K₁, and the rate constant for the subsequent oxidative addition step, k₂, were determined to (5.7 ± 2.5) × 10⁻³ and 18.4 ± 2.7 M⁻¹ s⁻¹, respectively.     

Solution structures of fluorescent Zn(II) complexes with bis(naphthyl amide)-EDTA

Two EDTA-based bichromophoric isomers form Zn(II) complexes that exhibit distinct fluorescent behaviors; the ligands are abbreviated as (edta1nap)H₂ and (edta2nap)H₂, each of which consists of an EDTA chain linked to two 1-naphthyl or 2-naphthyl groups. The coordination chemistry of these complexes was studied by UV-Vis, fluorescence and ¹H NMR. The formation constants and the inherent emission intensities were determined by the pH dependence of the emission spectra; the species of the most intense emission is ML(OH) for L = (edta1nap)²⁻, and ML for (edta2nap)²⁻. The ¹H NMR of Zn-(edta1nap)²⁻ exhibits two sets of signals due to a slow exchange between two equivalent coordination geometries, whereas Zn-(edta2nap)²⁻ undergoes a fast exchange to show a single set of NMR signals. The spin-lattice relaxation time T₁ determined for the isostructural Mn(II) complexes shows that the naphthyl proton closest to the metal ion is H(8) in the (edta1nap)²⁻ complex, and H(3) in the (edta2nap)²⁻ complex. The two ligands differ only in the substitution position of the naphthyl group, but this apparently small difference leads to the notable difference in structural, dynamic, and consequent emission-spectral properties of their metal complexes as a result of the steric and size effects of the aromatic rings.     

Self-assembly of para-OH functionalized ECE-metalated pincer complexes

Various para-OH functionalized ECE-pincer metal complexes [MX(ECE-OH)L_n] (ECE-OH = [C₆H₂(CH₂E)₂-2,6-OH-4]⁻, E = NMe₂, PPh₂ and SPh) were synthesized. The X-ray crystal structures of neutral [PdCl(SCS-OH)], [PdCl(NCN-OH)], and cationic [Pd(PCP-OH)(MeCN)](BF₄) are reported. The neutral halide complexes exhibit self-assembly to form polymeric chains via H-bonding involving the para-OH group as donors and the halide ligand on the metal as acceptors. Moreover, the halide ligand can be replaced by a monomeric aryloxy-O ligand leading to the formation of a covalently bonded dimer. The crystal structure of such a dimer derived from [PdI(NCN-OH)] is reported. Furthermore, these pincer-metal complexes were tethered through a carbamate linker to a siloxane functionality with the aim to be immobilized on a silica support. The crystal structure of a siloxane-functionalized [PtI(NCN-Z)] complex exemplifies how other H-bonding interactions not involving the metal-halide groupings can lead to polymeric networks as well.     

Coordination behaviour of nicotinamide: an infrared spectroscopic study

A series of Hofmann-type complexes containing two nicotinamide(nia) molecules attached to transition metal (II) (M) tetracyanonickelate frame with the formula: M(nia)₂Ni(CN)₄ (where M=Mn, Co, Ni, Cu or Cd) have been synthesised for the first time. Metal (II) halide complexes of nicotinamide complexes of the type [M(nia)₂X₂ (M=Cd, Ni, Cu, Hg; X=Cl, Br) and Ni(nia)₄Br₂ nia=nicotinamide] have also synthesised. The FTIR spectra are reported in the 4000-400 cm⁻¹ region. Vibrational assignments are given for all the observed bands. The analysis of the vibrational spectra indicates that there are some structure-spectra correlations. A pronounced change was observed in the N-H stretching frequencies of the NH₂ group. It is proposed that the amide NH₂ group influence by the intramolecular hydrogen bond in the complexes. The coordination effect on the nicotinamide modes is analysed.     

Metal-assisted transformation of N-benzoyldithiocarbazate to 5-phenyl-1,3,4-oxadiazole-2-thiol in the presence of ethylenediamine,and its first row transition metal complexes

The reaction of metal complexes of the type [M(HL)Cl] or [M(HL)₂] [where M = Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) and H₂L = N-benzoyldithiocarbazate] with an excess of ethylenediamine (en) in CHCl₃–MeOH medium leads to ring closure by desulfurisation to yield unique mixed-ligand complexes 1–4, [Cu(en)₂](pot)₂(pot = 5-phenyl-1,3,4-oxadiazole-2-thiol), [M(en)₂(pot)₂] [M = Ni(II), Mn(II)] and [Zn(en)(pot)₂]. The metal complexes have been characterized by various physicochemical methods. The molecular structure of [Cu(en)₂](pot)₂ has been determined by a single crystal X-ray diffraction study. In the centrosymmetric unit of [Cu(en)₂](pot)_2, the metal ion has a square planar arrangement of four symmetry related N-atoms of two en groups and is ionically bonded to two pot anions. Weak interaction studies on the complex reveal the presence of a hydrogen-bonded network in the molecule involving non-coordinating donor atoms of the pot anion with en resulting in the formation of an extended three-dimensional network. The arrangement of the [Cu(en)₂]²⁺ units, at a dihedral angle of 49.43° to pot⁻, provides a network of intermingled chains leading to a π–π stacked 3-dimensional framework.     

Crystal structure and magnetic properties of [{Cu(cyclam)}3{Fe(CN)6}2] · 6H2O,a cyano-bridged assembly with a rope-ladder chain structure

The synthesis, crystal structure and magnetic properties of the cyano-bridged complex [{Cu(cyclam)}₃{Fe(CN)₆}₂] · 6H₂O are reported. Its structure is made up of centrosymmetric S-shaped pentanuclear [{Cu(cyclam}₃{Fe(CN)₆)}₂] units, in which three [Cu(cyclam)]²⁺ units are alternatively bridged by two trans-CN groups of [Fe(CN)₆]³⁻ anions and water molecules. The pentanuclear Fe₂Cu₃ units are held together by two complementary and very weak Fe–CN?Cu1 bonds, forming a rope-ladder chain along the c axis. The compound exhibits a ferromagnetic interaction between the Cu(II) and Fe(III) ions as a consequence of the orthogonality of their magnetic orbitals of σ and π nature, respectively. The magnetic data were fitted to the calculated magnetic susceptibility equation for a pentanuclear model, leading to the following magnetic parameters: J₁ = 9.0(3) cm⁻¹, J₂ = 3.8(4) cm⁻¹, g = 2.2, θ = −1.2 K. These results show that the interactions through the long Cu–N axial bonds are not so weak as is usually assumed.     

Complexes derived from the general copper(II)/maleamic acid/N,N′,N′′-chelate reaction systems: Synthetic,reactivity, structural and spectroscopic studies

The synthetic investigation of the Cu^II/maleamate(−1) ion (HL⁻)/N,N′,N′′-chelate general reaction system has allowed access to compounds [Cu₂(HL)₂(bppy)₂](ClO₄)₂·H₂O (1·H₂O), [Cu(HL)(bppy)(ClO₄)] (2) and [Cu(HL)(terpy)(H₂O)](ClO₄) (4) (bppy = 2,6-bis(pyrazol-1-yl)pyridine, terpy = 2,2′;6′,2′′-terpyridine). In the absence of externally added hydroxides, compound [Cu₂(L′)₂(bppy)₂](ClO₄)₂ (3) was obtained from MeOH solutions; L′⁻ is the monomethyl maleate(−1) ligand which is formed in situ via the Cu^II-assisted HL⁻ → L′⁻ transformation. In the case of tptz-containing (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) reaction systems, the Cu^II-assisted hydrolysis of tptz to pyridine-2-carboxamide (L1) afforded complex [Cu(L1)₂(NO₃)₂] (5). The crystal structures of 1–5 are stabilized by intermolecular hydrogen bonding and π–π stacking interactions. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Redox-active antifungal cobalt(II) and copper(II) complexes with sterically hindered o-aminophenol derivatives

Co(II) complexes with 4,6-di(tert-butyl)-2-aminophenol (HL^I) and 2-anilino-4,6-di(tert-butyl)phenol (HL^II) have been synthesized and characterized by means of physico-chemical methods. The compounds HL^I and HL^II coordinate in their singly deprotonated forms and behave as bidentate O,N-coordinated ligands; their low-spin Co(II) complexes are characterized by CoN₂O₂ coordination modes and square planar geometry. Both the free ligands and their Co(II) and Cu(II) complexes (we have produced and characterized the latter before) exhibit a pronounced antifungal activity against Aspergillus niger, Fusarium spp., Mucor spp., Penicillium lividum, Botrytis cinerea, Alternaria alternata, Sclerotinia sclerotiorum, Monilia spp., which in a number of cases is comparable with that of Nystatin and Terbinafine or even higher. The reducing properties of the ligands and their metal(II) complexes, as well as their antifungal activities, were found to decrease in the order: Cu(L^I)₂ > Cu(L^II)₂ ? Co(L^I)₂ > Co(L^II)₂ > HL^I > HL^II.