New μ-oxo-bridged tetranuclear Cu(II) complex with Schiff-base ligand: Synthesis,crystal structure and magnetic properties

A new μ-oxo-bridged Cu(II) complex with cubane-like tetranuclear copper(II) complex, [Cu₄(L¹)₄] · 4H₂O (1) (H₂L¹ = 2-(3-methoxy-salicylidene-amino)-benzyl-alcohol), has been prepared, and structurally characterized by X-ray crystallography. Complex 1 crystallized in the monoclinic space group P₂₁/n and has a tetranuclear core of Cu₄O₄. The temperature dependence of magnetic susceptibility measurements shown that complex 1 exhibits a strong antiferromagnetic interaction with J = −103.4 cm⁻¹.     

A new μ1,5-dicyanamide bridged cyclic tetranuclear copper (II) complex with 1,5,9-triazacycledodecane ligands: structure,ESR spectroscopic and magnetic properties

The tetranuclear complex [Cu₂L₂(dca)₂(ClO₄)₂]₂ (1) (L = 1,5,9-triazacyclododecane, dca = dicyanamide [N(CN)₂]⁻) has been synthesized and its crystal structure, ESR spectra and magnetic properties determined. The complex contains a tetranuclear copper (II) moiety in which two dimeric units are bridged by two dca ligands. In each dimeric moiety the two copper (II) ions are bridged by one μ_1,5-dicyanamide ligand. Magnetic susceptibilities for the complex in the solid state are measured over the temperature range 4–300 K. The complex shows a weak antiferromagnetic coupling with a best fit J value −0.436 cm⁻¹. The μ_1,5-dicyanamide bridges are the principal pathway for the super-exchange interaction and the weak antiferromagnetic coupling of the complex is interpreted in term of the μ_1,5-dicyanamide ligand behavior as a poor magnetic mediator.     

Alkoxo- and carboxylato-bridged hexanuclear copper(II) complex: Synthesis,structure and magnetic properties

Reaction of copper(II) nitrate trihydrate with N,N-dimethylethanolamine (dmea) and pivalic acid in methanol led to the hexanuclear copper(II) complex Cu₆(η¹:μ₂-C₄H₁₀NO)₄(η¹:η¹:μ₂-C₅H₉O₂)₄(η¹:μ₁-C₅H₉O₂)₂(μ₃-OH)₂ (1). The crystal structure of 1 indicates that hexametallic centers are bridged by the μ₃-alkoxo, dmea oxygens, and the μ₂-dicarboxylato oxygen atoms of pivalate ions. Furthermore, in the asymmetric unit, three types of copper ions have been found labeled as Cu₁, Cu₂ and Cu₃. The Cu₂ takes a distorted octahedral shape, whereas Cu₁ and Cu₃ adopt square pyramidal geometries. The complex 1 shows strong antiferromagnetic interactions through the oxo groups within the dimeric units (J = − 82.6 to − 25.8 cm^− 1) and weak antiferromagnetic couplings between the dimers (J = − 10.9 and 0.8 cm^− 1).     

A tetranuclear pyrophosphate-bridged Cu(II) complex with 4,4′-bipyridine and 1,10-phenanthroline: Synthesis,structural, and magnetic properties

A new tetranuclear pyrophosphate-bridged Cu(II) complex with 4,4′-bipyridine and 1,10-phenanthroline [Cu₄(phen)₄(bpy)₂(P₂O₇)₂]·10H₂O (1) has been hydrothermal synthesized and characterized by single-crystal X-ray analysis, element analysis, IR spectroscopy, TG analysis, and UV–vis spectra. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic interactions between the neighbor Cu(II) centers in 1. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = − 13.16 cm^− 1).     

Synthesis,crystal structure and magnetic properties of a new cyanide-bridged mixed-valence copper(I)/copper(II) clathrate

A unique cyanide-bridge mixed-valence Cu^I/Cu^II clathrate of formula [Cu^I₂(CN)₃][{Cu^II(tren)}₂(μ-CN)](CF₃SO₃)₂ [tren = tris(2-aminoethyl)amine] containing cyanide-bridged [{Cu^II(tren)}₂(μ-CN)]^3 + binuclear cations stacked between anionic honeycomb layered copper(I) cyanide networks, was synthesized and structurally characterized by single crystal X-ray diffraction. Variable-temperature magnetic susceptibility studies showed that the cyanide bridge mediates a strong antiferromagnetic interaction between the copper(II) centers (J = − 160 cm^− 1, the spin Hamiltonian being defined as H = −J S_A⋅S_B).     

Reversible water inclusion in a porous magnetic material synthesized from copper(II) incorporated metal-organic framework showing alternate ferro- and antiferromagnetic interactions

X-ray structural analysis shows that {[Cu₂(CTA) (H₂O)] · 5 H₂O}_n constitutes infinite one-dimensional parallel chains along the c-axis with water columns running down the crystallographic a-axis. The inclusion of water molecules is reversible and is confirmed by X-ray powder diffraction studies. The magnetic data (2–300 K) reveal that there are alternate ferro- (J = 0.29 cm⁻¹) and antiferromagnetic (J = −2.5 cm⁻¹) interactions.     

Synthesis,characterization and reactivity of a trinuclear copper(II) thiocyanurate complex: A spin-frustrated molecular propeller

1,3-bis{2-(4-methylpyridyl)imino}isoindoline (4-MeInH) reacts with copper(II) acetate and 2,4,6-trimercaptotriazine (H₃TMTA) to yield [Cu(4-MeIn)]₃(TMTA), a trinuclear propeller complex composed of three Cu(4-MeIn) “blades” coordinated to a 2,4,6-trimercaptotriazine (TMTA) “hub”. Each copper(II) center is coordinated via a exocyclic sulfur and a ring nitrogen from TMTA. Although the trimer is infinitely stable in the solid state, dark green solutions fade over time to produce a mixture of dinuclear products which are a result of both hydrolysis and desulfurization reactions. Variable temperature magnetic susceptibility measurements on [Cu(4-MeIn)]₃(TMTA) are consistent with a spin-frustrated doublet ground state and show the presence of moderate antiferromagnetic coupling (−2J = 38.14 cm⁻¹) between the copper(II) centers.     

A novel dimeric polyanion based on mono-manganese substituted Keggin-type phosphotungstate: (MnPW11O39)210 −

The novel dimeric polyoxometalate, (MnPW₁₁O₃₉)₂^10 − (1a), has been synthesized by reacting [B-α-PW₉O₃₄]^9 − with Mn^2 + ions in weak acid aqueous solution (pH = 5.3) under hydrothermal condition and isolated in the form of (C₁₄H₁₄N₄)₅H₁₀(MnPW₁₁O₃₉)₂·2H₂O (1), which was characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and magnetic measurements. The polyanion represents the first example of dimeric polyanion based on mono-transition metal (TM) substituted Keggin-type polyanions linked by two TM-μ₂-O-TM bridges. Magnetic measurements show that the Mn┄Mn exchange interactions are weakly antiferromagnetic (J = ⁻ 0.53 cm^− 1).     

Design,structure and magnetic properties of a novel one-dimensional Mn(II) coordination polymer constructed from 4-pyridyl-NH-1,2,3-triazole

A one-dimensional manganese(II) complex, [Mn(L₂)]_n (1, HL = 4-pyridyl-NH-1,2,3-triazole), has been hydrothermally synthesized at 120 °C. In the structure of 1, the Mn(II) ions are octahedral coordinated and further bridged by L⁻ ligands, forming a rigid 1D ribbon coordination chain. Varieties of supramolecular interactions, such as hydrogen bonds and CH ⋯ π interactions, play an important role on the stabilization of the structures. As revealed by magnetic measurement, complex 1 displays weak antiferromagnetic interaction with θ = –4.83 K, the best fit using Fisher's 1D Heisenberg model gives the intrachain magnetic coupling constant J = –0.21 cm^− 1 above 30 K due to the neighboring Mn(N–N)₂Mn rings twisted in the angle of almost 90°.     

Synthesis,structure, and magnetic properties of a novel mixed-bridged heterometal tetranuclear complex [Mn2Ni2(MeOSalen)2(μ1,1-N3)2(N3)2]

The first heterometal tetranuclear complex with alternating azido and phenoxo bridges, [Mn₂Ni₂(MeOSalen)₂(μ_1,1-N₃)₂(N₃)₂] (MeOSalenH₂ = bis(3-methoxy)salicylideneimine), was synthesized and structurally characterized by X-ray crystallography and spectroscopic methods. Magnetic studies suggest there is a ferromagnetic interaction between the μ_1,1-azido-bridged Mn(II) ions with J = +2.11 cm⁻¹, while the Ni(II) ions are diamagnetic in the tetranuclear system.     

Structural characterization of ferromagnetic bridged-acetato and -dichlorido copper(II) complexes based on bicompartmental 4-t-butylphenol

The reaction of Cu(II) salts with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-t-butylphenol (L^t-Bu-OH) afforded two bridged-phenoxido/hydroxido complexes. The dinuclear bridged acetate species [Cu₂(μ-L^t-Bu-O)(μ-CH₃COO)](PF₆)₂ (1) and the 1D polymeric doubly-bridged-chlorido {[Cu₂(μ-L^t-Bu-OH)(μ-Cl)₂](ClO₄)₂·4H₂O}_n (2). The two complexes were structurally characterized. Both complexes revealed ferromagnetic interactions; moderate in complex 1 (J = + 30.8 cm^− 1) and very weak (J = + 2.25 cm⁻¹) in 2.     

ESR,solid-state 31P MAS NMR,and UV–vis–NIR studies on linear CuI CuII CuI trinuclear species: Crystal structure of bis-μ-salicylato (2−)-1:2 κ4O; 2:3 κ4O-tetrakis (triphenylphosphine-1κ2P, 3κ2P)-tricopper(I,II, I), [(PPh3)2Cu]2(μ-o-OC6H4COO)2Cu

A novel neutral mixed-valence Cu(I)Cu(II)Cu(I) linear trinuclear copper metallomacrocycle [(PPh₃)₂Cu]₂[μ-o-OC₆H₄COO]₂Cu (3) has been synthesized and characterized. Compound 3 consists of two Cu(I) ions and one Cu(II) ion which are bridged by two salicylate (2^?) ligands, and the external copper(I) atoms are coordinated by four terminal triphenylphosphines. The essentially localized mixed-valence [Cu(I)Cu(II)Cu(I)] formulation for 3 was determined on the basis of X-ray crystallography, solid-state ³¹P MAS NMR, and ESR spectroscopy. The solid-state ³¹P MAS NMR spectra of 3 is reported, affording δ[P(2)] = ?1.7 ppm with ¹J[Cu(I), P] = 1330 Hz and δ[P(1)] = ?3.4 ppm with ¹J[Cu(I), P] = 1600 Hz. UV–vis–NIR spectral measurement demonstrates the Robin–Day class II behavior of the mixed-valence compound 3 with a weak copper–copper interaction.     

Dicyanamido–metal(II) complexes. Part 3: Hydrolysis of the dicyanamide into amidocyanamide during its interaction with Cu(II) perchlorate and 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine

The reaction of Cu(ClO₄)₂, 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine (DPA-CO-py) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of three complexes: {[Cu(DPA)(μ_1,5-dca)]ClO₄}_n (1), [Cu₂(pic)₂(μ_1,3-H₂NCO–N–CN)₂(H₂O)₂] · 2H₂O (2) and Cu(pic)₂ · H₂O (3). The Cu²⁺ ion, during its complex formation with DPA-CO-py and dca not only assisted the hydrolysis of DPA-CO-py to the corresponding di(2-methylpyridyl)amine (DPA) and picolinic acid (Hpic) but also resulted in partial hydrolysis of one of the two nitrile groups of the dicyanamide, NC–N–CN^? (dca) to amidocynamide, H₂NCO–NH–CN. The complexes were structurally characterized and the single X-ray structures for 1 and 2 reveal their identity. Complex 1 forms a 1D polymeric chain with the dca acting as a μ_1,5-bridging ligand via the terminal nitrile nitrogen atoms. A distorted SP geometry around the Cu²⁺ centers was achieved by the three N-atoms of the DPA and by the two nitrile groups of the bridging dca ligands. Complex 2 consists of a dimeric unit with CuN₃O₂ chromophore in coordination polyhedron that has a distorted SP geometry. The amidocyanamide ion, H₂NCO–N–CN^? acts as bis(monodentate) μ_1,3-bridging ligand via the central amido and terminal nitrile nitrogen atoms whereas the picolinate anion forms a six-membered chelate ring through its pyridyl nitrogen and an oxygen atom of the carboxylate group, and the aqua water occupies the apical position of the structure. Complex 1 exhibits very weak antiferromagnetic coupling (J = ?0.31 cm^?1) whereas 2 shows a significant antiferromagnetic interaction between the two copper centers (J = ?13.6 cm^?1).     

Dicyanamido-metal(II) complexes. Part 5: First example for a unit cell containing dinuclear and 1-D polymeric Cu(II) complexes bridging by dicyanamide

The reaction of Cu(ClO₄)₂, N,N,N′,N″,N″-pentamethylethylenetriamine (pmedien) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of {[Cu(pmedien)(μ_1,5-dca)]₂(ClO₄)₂,[Cu(pmedien)(μ_1,5-dca)]_n(ClO₄)_n} (1). The complex was structurally and magnetically characterized. Single X-ray crystallography for 1 reveals the existence of two independent molecules in the unit cell: dinuclear doubly bridging complex and a 1-D polymeric chain with dca in both cases acting as a μ_1,5-bridging ligand via the terminal nitrile nitrogen atoms. Magnetic susceptibility measurements of the complex showed that the Cu(II) ions are weakly coupled with ferromagnetic interaction in the dinuclear unit (J_d = 0.9 cm^–1) and antiferromagnetic interaction in the polymeric chain (J_c = ? 0.6 cm^? 1).     

Improved photovoltaic performances of Ru (II) complex sensitized DSSCs by co-sensitization of carbazole based chromophores

Herein, we report photovoltaic performance studies of three carbazole based dyes (N_1–3) derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl)acrylonitrile scaffold as effective co-sensitizers in Ru (II) complex, i.e. NCSU-10 sensitized DSSCs. From the results it is evident that, the device fabricated using co-sensitizer N₃ with 0.2 mM of NCSU-10 exhibited improved photon conversion efficiency (PCE) of 8.73% with J_SC of 19.87 mA·cm^− 2, V_OC of 0.655 V and FF of 67.0%, while N₁ displayed PCE of 8.29% with J_SC of 19.75 mA·cm^− 2, V_OC of 0.671 V and FF of 62.6%, whereas NCSU-10 (0.2 mM) alone displayed PCE of 8.25% with J_SC of 20.41 mA·cm^− 2, V_OC of 0.667 V and FF of 60.6%. However, their EIS studies confirm that, N₁, showing higher V_OC is efficient in suppressing the undesired charge recombination in DSSCs through enhanced surface coverage on TiO₂ and thereby resulting in longer electron lifetime than that of NCSU-10 dye alone. Here, the higher PCE of N₃ can be attributed to its improved light harvesting efficiency, which is due to the presence of highly electron withdrawing barbituric acid in its structure. Conclusively, the results showcase the potential of simple carbazole based dyes as co-sensitizers in improving efficiency of DSSCs.     

An alternating chain consisting of dinuclear Cu(II) ions bridged by end-on bis(μ-dicyanamido-κN1,N5) ligands and hydrogen-bonded pairs of bis(pyrimidin-2-yl)amines,with unusually long Cu⋯Cu distances of 7.20 and 9.99 Å: Synthesis,structure and magnetic properties of [Cu(dipm)(μ-dca)(H2O)(ClO4)]2 · 2EtOH

A novel bis (end-to-end) bridged dicyanamide dinuclear copper(II) compound with the general formula [Cu(dipm)(μ-dca)(H₂O)(ClO₄)]₂ · 2EtOH (in which dipm = bis(pyrimidin-2-yl)amine) has been synthesised and characterised by X-ray crystallography and infrared spectroscopy. In addition, EPR and magnetic measurements have been performed.The geometry around the copper(II) ion is distorted octahedral with the basal plane formed by the two nitrogen atoms of the dipm ligand and two nitrogen atoms of two end-to-end bridging dca anions. The Cu–N distances vary from 1.979(4) to 2.004(3) Å. The apical positions are occupied by an oxygen atom of a water ligand with a Cu–O distance of 2.216(3) Å and an oxygen atom of a perchlorate anion with a semi-coordinating distance of 2.89(1) Å, 2.950(7) Å. A hydrogen-bond interaction of the Watson–Crick type is observed between the amine N atom of a dipm ligand to a pyrimidyl N atom of a neighbouring dipm ligand with a N⋯N distance of 2.970(4) Å. Furthermore, medium to strong hydrogen bond interactions are present between oxygen atoms of the water molecule, perchlorate lattice anions and ethanol molecules.The magnetic interaction between the Cu–Cu atoms is weak antiferromagnetic with a singlet–triplet separation (J) of −4.3  cm⁻¹.     

Structure and magnetic properties of A Cu(II) coordination polymer supported by a tetrapodal Schiff base ligand

A Cu(II) Schiff base coordination polymer, {[Cu₃L(μ₂-NO₃)₂·(H₂O)₂].3H₂O}_n, is readily prepared by complexation of the tetrapodal Schiff base, H₄L (H₄L = 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane), with cupric nitrate trihydrate. It has been demonstrated that the coordination polymer consists of linear trinuclear Cu(II) entities, and displays a cooperative coordination mode for nitrate anions, coordinated water molecules, and Schiff base ligands to Cu(II) ions. In addition, variable-temperature magnetic susceptibility measurements reveal a strong antiferromagnetic coupling interaction between adjacent copper(II) ions with large J value of − 289.66 cm^− 1.     

1D nickel(II) coordination polymer with pyrimidine and pivalate bridges: Synthesis,structure and magnetic properties

New 1D polymeric compound [Ni₂(μ-OH₂)(μ-Piv)₂(Piv)₂(μ-pym)(η¹-pym)₂]_n (3, Piv is an anion of pivalic acid) was synthesized upon the reaction of the nickel(II) pivalate complex Ni₉(OH)₆(Piv)₁₂(HPiv)₄ (3) and pyrimidine (pym) in MeCN. Complex 3 was characterized by the X-ray diffraction study and magnetic measurements. It is shown that neighboring Ni sites in the 1D metal chain in 3 are coupled by weak antiferromagnetic interactions with two exchange parameters of J₁ = –3.1 and J₂ = –1.2 cm^–1.     

Selective adenine/cytosine cations in one-dimensional coordination polymers of manganese (II) and copper (II) 2,3-pyridinedicarboxylates

One-dimensional coordination polymer {[1H,9H-ade]₂[MnL₂]?4H₂O}_n (1) and {[1H,3H-cyt]₂[CuL₂]?6H₂O}_n (2) (ade = adenine, cyt = cytosine, L = dianion of 2,3-pyridinedicarboxylic acid) are selectively synthesized and variable-temperature magnetic susceptibility measurements revealed weak antiferromagnetic interactions within the chains of 1 and 2 (J = ? 0.29 cm^? 1 for 1 and J = ?0.03 cm^? 1 for 2, according to the ? 2J_ijS_iS_j HDvV Hamiltonian formalism).     

Synthesis,structures and properties of cobalt(II) and copper(I) complexes of 2,6-diamino-3-[(2-carboxymethyl)phenylazo]-pyridine

The reaction of methyl anthranilate, sodium nitrite, and 2,6-diamino-pyridine affords a new compound, 2,6-diamino-3-[(2-carboxymethyl) phenylazo]-pyridine (L), which has been characterized with X-ray crystallography and NMR spectrum. The reaction of L and CoCl₂? 6H₂O or Cu(ClO₄)₂? 6H₂O gives a dinuclear cobalt(II) complex [Co₂L₂Cl₃]Cl (1), and a copper(I) complex [CuL₂]ClO₄ (2),respectively. They are characterized by X-ray crystallography, X-ray photoelectron spectroscopy, NMR spectra, magnetic measurement and emission spectra. Magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = ? 141.8 cm^? 1). Complex 2 exhibits photoluminescence at 557 nm.