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).     

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.     

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.     

Synthesis,crystal structure,and magnetic property of a stepped tetranuclear copper(II) complex of 3,5-diisopropylpyrazole-1-methoxide

Reaction of copper(II) chloride dihydrate in methanol with deprotonated 3,5-diisopropylpyrazole-1-methanol (dippmOH) led to the tetranuclear copper(II) complex [(dippmO)CuCl]₄ (1). The crystal structure of 1 indicates that two copper(II) ions connect via the oxygen atoms of dippmO⁻ ligands each other in which two dimeric units are formed. Furthermore, one of the coordinated oxygen atoms in a dimer is bonded to an adjacent copper(II) ion positioned other dimer, which gives rise to a stepped tetranuclear structure. 1 shows strong antiferromagnetic interactions through the oxo groups within the dimeric units (J₁ = − 239 cm^− 1) and weak antiferromagnetic couplings between the dimers (J₂ = − 15 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).     

A dual shell-like heptadecanuclearity [Gd5Ni12] cluster with ferromagnetic interaction and large magnetocaloric effect

A new dual shell-like heptadecanuclearity [Gd₅Ni₁₂(Pro)₉(CMP)₆(μ₃-OH)₉(μ₂-OH)₃(H₂O)₃] · Cl₆ · 23H₂O (1) cluster with proline (HPro) and N-carboxymethyl-l-proline (H₂CMP) as coligands has been successfully synthesized and characterized. The compound consists of rare trigonal bipyramid {Gd₅} core and triangular orthobicupola {Ni₁₂} outer shell. The magnetic studies reveal that 1 shows ferromagnetic interactions and a large magnetocaloric effect (22.4 J kg^− 1 K^− 1, ΔH = 7 T).     

One-dimensional copper(II) complex containing alternate single and double end-on azide ligands: Crystal structure and magnetic characterization

A novel one-dimensional azido-bridged coordination polymer of formula [Cu₂(L)₂(H₂O)(N₃)₄]_n (1) has been synthesized and characterized crystallographically and magnetically, where L is 5-methylpyrimidin-2-amine. Complex 1 consists of 1D chain in which the Cu(II) ions with a square pyramidal geometry are alternately bridged by asymmetric single and symmetric double end-on (EO) azido ligands. Magnetic analysis reveals that the dominating ferromagnetic interaction is mediated by the symmetric double azido bridge with the exchange parameter J = 55.17 cm⁻¹.     

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).     

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).     

Synthesis and cytotoxicity of a ruthenium nitrosyl nitric oxide donor with isonicotinic acid and a cell penetrating peptide

The syntheses and properties of trans-[Ru(NH₃)₄(L)(NO)](BF₄)₃ (L = isonicotinic acid (inaH) (I) or ina-Tat48–60 (II)) are described. Tat48–60, a cell penetrating peptide fragment of the Tat regulatory protein of the HIV virus, was linked to the ruthenium nitrosyl through inaH. I and II release NO after reduction forming trans-[Ru(NH₃)₄(L)(H₂O)]^3 +. The IC₅₀ values against B16-F10 melanoma cells of I and II (21 μmol L^− 1 and 23 μmol L^− 1, respectively) are close to that of the commercially available cisplatin (33 μmol L^− 1) and smaller than similar complexes. The cytotoxicity is assigned to the NO released from I and II.     

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.     

Synthesis and characterization of an unprecedented 3D lanthanide coordination polymer assembled by cubane-like clusters and a flexible V-shaped dicarboxylate ligand

A lanthanide coordination polymer based on H₂sfdb ligand, namely [Tb₄(sdbc)₄(phen)₂(μ₃-OH)₄]_n ∙ 1.5nH₂O (1) (H₂sfdb = 4,4′-sulfonyldibenzoic acid, phen = 1,10-phenanthroline) has been hydrothermal synthesized and characterized. Compound 1 exhibits an unprecedented three-dimensional framework that comprised new cubane-like hydroxo clusters [Tb₄(μ₃-OH)₄]^8 + as the nodes and flexible (sfdb)^2 − ligands as the linkers. In 1, (sfdb)^2 − ligands display completely different four kinds of coordination modes. Interestingly, not only the carboxylate groups but also one oxygen atom of sulfonyl group of (sfdb)^2 − ligand are coordinated with Tb^III ions in 1, which is first found in the compounds based on H₂sfdb ligand. The luminescence experiments show that Tb^III compound exhibits the typical Tb^III-centered luminescence.     

A couple of Co(II) enantiomers constructed from semirigid lactic acid derivatives

Enantiopure organic linkers (R)-H₂CBA and (S)-H₂CBA have been synthesized from nature lactic acid and rigid 4-hydroxybenzoate. With the help of auxiliary ligand 4,4′-BIP, (R)-H₂CBA and (S)-H₂CBA afford two enantiomeric coordination polymers, namely [Co₂((R)-CBA)₂(4,4′-BIP)₂]⋅ xH₂O (1-D) and [Co₂((S)-CBA)₂ (4,4′-BIP)₂]⋅ xH₂O (1-L). In complexes 1-D and 1-L, the CBA^2 − ligands and dinuclear Co units form 4-connected Co-CBA layers, which are further linked to a pillared-layer framework with 2-fold interpenetration pcu structure by 4,4′-BIP ligands. Moreover, complex 1-D displays antiferromagnetic interactions.     

Synthesis and characterization of unusual heterotrinuclear Co(III)Ni(II)Co(III) hydrotris(3,5-dimethylpyrazolyl)borate complex with mixed 1,1-azide and pyrazolate bridges

An unusual heterotrinuclear complex [LCo(μ-L₁, 1-N₃)₂(μ-L₁)Ni(μ-1, 1-N₃)₂(μ-L₁)CoL] (1) was obtained by the reaction of the precursor of half-sandwich nickel(II) complex [LNi(HL₁)₂(N₃)] (2) and CoCl₂ · 6H₂O (L = hydrotris(3,5-dimethylpyrazolyl)borate; L₁ = 3,5-dimethylpyrazolate), the complex 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV–vis spectra and magnetic properties.     

A 3D (3,8)-connected net based on the tetranuclear Cu4 units constructed from mixed organic ligands

Under hydrothermal conditions, a new polynuclear Cu(II) complex, [Cu₂(nip)(ina)(μ₃-OH)]₂·H₂O (1) (H₂nip = 5-nitroisophthalic acid, Hina = isonicotinic acid) has been synthesized with mixed organic ligands. Single crystal X-ray analysis reveals that complex 1 displays a three-dimensional (3D) structure based on the tetranuclear Cu₄ units. In the structure of 1, two pairs of symmetry-related Cu(II) ions are connected by six carboxyl and two μ₃-OH groups to generate the tetranuclear Cu₄ units, which are connected by the mixed ligands into a 3D framework. Topology analysis reveals a (3,8)-connected tfz-d net for 1. Magnetic studies display antiferromagnetic behavior for 1. And thermogravimetric analysis of 1 has also been investigated.     

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).     

Two Gd2 compounds constructed by 8-hydroxyquinoline Schiff base ligands: Synthesis,structure, and magnetic refrigeration

Two new Gd₂ compounds having formulae, [Gd₂(hfac)₄(L1)₂] (1) and [Gd₂(hfac)₄(L2)₂] (2) (hfac = hexafluoroacetylacetonate, HL1 = 2-[4-methylaniline-imino]methyl]-8-hydroxyquinoline and HL2 = 2-[(3,4-dimethylaniline)-imino]methyl]-8-hydroxyquinoline), have been successfully synthesized via applying two different 8-hydroxyquinoline Schiff base ligands, and further characterized by crystallography. Structural analysis shows that both of 1 and 2 are phenoxo-O bridged dinuclear complexes. The magnetic study reveal that 1 and 2 display cryogenic magnetic refrigeration properties with maximum − ΔS_m = 17.66 J kg^− 1 K^− 1 at 2 K and 7 T for 1 and − ΔS_m = 14.81 J kg^− 1 K^− 1 at 3 K and 7 T for 2.     

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).     

Copper(II) azide complexes of [Cu(acac)(N3)(dpyam)] and [Cu(μ-N3-κN1)(C2N3-κN1)(dpyam)]2: Synthesis,crystal structure and magnetism

Two new compounds, [Cu(acac)(N₃)(dpyam)] (1), (acac = acetylacetonate; dpyam = di-2-pyridylamine) and [Cu(μ-N₃-κ^N1)(C₂N₃- κ^N1) (dpyam)]₂ (2), have been synthesized and characterized by single-crystal X-ray diffraction and magnetic analyses. Compound 1 is a mononuclear compound in which each of two independent Cu(II) ions is penta-coordinated with a distorted square pyramidal geometry with distortion parameters τ = 0.21 and 0.16. In contrast, compound 2 is an azido-bridged dinuclear compound with monodentate dicyanamide anions and the Cu(II) ions display a distorted trigonal bipyramidal geometry with τ = 0.73 and end-on azido bridges providing an equatorial–axial position between the metal ions. The EPR spectra of powdered samples for 1 and 2 have also been investigated. Magnetic susceptibility measurements of compound 2 reveal a very weak ferromagnetic interaction between the Cu(II) ions with a J value of +5.8 cm⁻¹.