1-(Pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole and its copper(II) complex as a new fluorescent sensor for dopamine (4-(2-aminoethyl)benzene-1,2-diol)

A new ligand 1-(pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole (L) and its Cu(II) complex (1) have been synthesized and characterized spectroscopically and structurally. The Cu(II) ion is coordinated by two nitrogen atoms of benzimidazole groups, two oxygen atoms of the nitrate anions and one oxygen atom of a water molecule forming distorted trigonal bipyramidal geometry. The ligand and its complex have been utilized as a fluorescent sensor for 4-(2-aminoethyl)benzene-1,2-diol. A plot of F₀/F − F₀ vs 1/Conc (4-(2-aminoethyl)benzene-1,2-diol) at a selected wavelength of 306 nm with (L) that shows a straight line behavior, supports the validity of the assumption of 1:1 complex formation and the association constant of (L) with 4-(2-aminoethyl)benzene-1,2-diol is calculated to be 9868 M^− 1. Sensor (L) is found to be selective for 4-(2-aminoethyl)benzene-1,2-diol over aromatic amines, phenols, amino catechol (L-3,4-dihydroxyphenylalanine) and 4,6-ditertiarybutyl benzene-1,2-diol.     

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).     

A new binuclear Cr(III) citrate anion: Synthesis,characterization and crystal structure of [Cr(CO(NH2)2)6]2[Cr2(CO(NH2)2)2(C6H4O7)2]3

The new anion [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − has been isolated in the complex [Cr(CO(NH₂)₂)₆]₂[Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]₃. The crystals of this complex were obtained by a one-pot synthetic method using 1:1 molar ratio of hexaureachromium(III) chloride and trisodium citrate in aqueous medium. It was characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction analysis. The compound crystallizes in space group R‾3 of the trigonal system with three formula units in a cell of dimensions a = b = 24.7461(4) Å, c = 13.7204(3) Å and γ = 120°. The crystal structure comprises the columns consisting of [Cr(CO(NH₂)₂)₆]^3 + cations surrounded by a cylinder of complex anions, [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − which are packed in a honeycomb-like manner. This supramolecular architecture is formed and stabilized by inter- and intramolecular NH⋯O hydrogen bonds.     

A 2D coordination polymer with brick-wall network topology based on the [Cu(NCS)2(pn)] monomer

The new complex [Cu(NCS)₂(pn)] (1) (pn = 1,3-propanediamine) has been synthesized and characterized by elemental analysis, infrared and electronic spectroscopy. Single crystal X-ray diffraction studies revealed that complex 1 is made up of neutral [Cu(NCS)₂(pn)] units which are connected by μ-1,3,3-thiocyanato groups to yield a 2D metal-organic framework with a brick-wall network topology. Intermolecular hydrogen bonds of the type NH⋯SCN and NH⋯NCS are also responsible for the stabilization of the crystal structure.     

Coexistence of two distinct axial ligands and their thermo-induced substitution in trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (L = 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole)

A novel iron(II) complex, trans-[FeL₂(NCS)₂][FeL₂(CH₃OH)₂](NCS)₂ (1) with 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) has been successfully synthesized and characterized. X-ray crystallography analysis shows that 1 is the first example in the mononuclear triazole-based complexes consisting of two distinct molecules: trans-[FeL₂(NCS)₂] and trans-[FeL₂(CH₃OH)₂](NCS)₂ with each octahedral iron(II) center coordinated axial by two NCS⁻ ions in Fe1 but two MeOH molecules in Fe2. Moreover, 1 can lose two MeOH molecules at 220 °C to form trans-[FeL₂(NCS)₂] (2) which can be transformed to 1 when recrystallizing 2 in methanol. Both 1 and 2 are high-spin species in the range of 1.8–300 K.     

Tris(μ-phenoxo) bridged Cd(II) polymer synthesised from a symmetrical tripodal ligand: A novel observation for heptadentate monocapped trigonal antiprismatic Schiff base complex

A novel one-dimensional cadmium(II) polymer [Cd₂(L){HCON(CH₃)₂}N(CN)₂]_n (H₃L = condensation product of tris(2-aminoethyl)amine and salicylaldehyde) has been achieved from a tripodal Schiff base tris[(2-salicylaldeneimino)ethyl]amine or ‘trensal’. The structure confirmed from single crystal X-ray diffraction analysis reveals that each of the tris(μ-phenoxo) bridged individual Cd(II) dimeric units is interlinked via μ-(1,5) end-to-end (EE) dicyanamide [N(CN)₂]⁻ ligand framing a wavy chain polymer, which is believed to be the first report of its kind in the literature.     

Photochemical reductive elimination of [PtIV(NH3)4(NH2)Cl]2 +: Photogeneration of hydrazine

When [Pt^IV(NH₃)₅Cl]^3 + is deprotonated the complex [Pt^IV(NH₃)₄(NH₂)Cl]^2 + is formed. Upon NH₂⁻ → Pt^IV LMCT excitation (λ_irr > 250 nm) a reductive elimination takes place: [Pt^IV(NH₃)₄(NH₂)Cl]^2 + → [Pt^II(NH₃)₃Cl]⁺ + N₂H₄ + H⁺. Since Pt(II) ammine complexes can be reoxidized to Pt(IV) by H₂O₂ it is suggested that in a cyclic process the overall reaction could proceed according to the equation: 2 NH₃ + H₂O₂ → N₂H₄ + 2 H₂O.     

Imidazolate-bridged dinuclear copper(II) complex with new macrocyclic ligand bearing two 1H-imidazol-4-yl-pendants

A new imidazolate-bridged dicopper complex [Cu₂(L)(Im)](ClO₄)₃·H₂O has been synthesized by reaction of new macrocyclic ligand 6, 20-bis(1H-imidazol-4-ylmethyl)-3, 6, 9, 17, 20, 23-hexaazatricyclo[24.3.1.1^11,15]hentriaconta-1(29), 11, 13, 15(31), 26(30), 27-hexaene (L) with Cu(ClO₄)_2?6H₂O and imidazole, and structurally characterized as a model compound of Cu₂Zn₂-SOD. There is antiferromagnetic interaction with g = 2.08, ? 2 J = 66.5 cm^? 1 between the two imidazolate-bridged Cu(II) atoms. The complex displays moderate SOD activity with IC₅₀ of 1.42 μM.     

Role of spacers and substituents in the self-assembly process: Syntheses and characterization of two novel thiocyanatocuprates polymers

Two novel cation-induced complexes, {(Phen-dq) [Cu₂(SCN)₄]}_n (1) and {(Phen-dzp) [Cu₂(SCN)₄]}_n (2) [Phen-dq = (C₁₄H₁₂N₂)²⁺, 5,6-dihydropyrazino[1, 2, 3, 4-lmn]-1, 10-phenanthrolinium, Phen-dzp = (C₁₅H₁₄N₂)²⁺, 6,7-dihydro-5H-[1, 4]diazepino[1, 2, 3, 4-lmn][1,10]phenanthroline-4, 8-diium], have been synthesized via the self-assembly reaction in solution. The compound 1 possesses a two-dimensional supramolecular network linked by bridging thiocyanate groups. Complex 2 is also a two-dimensional polymeric architecture with the organic cation Phen-dzp trapped in it. Each Cu(I) atom is coordinated by two N atoms and two S atoms from four NCS groups to form a Cu₂(NCS)₂ rectangular dimer unit. In these two compounds, thanks to the difference from organic cations, the simple modification from Phen-dq to Phen-dzp leads to distinct structures between 1 and 2, and these “planar” cations are effective guests to manipulate the aggregate structure of thiocyanatocuprates.     

Binuclear cyano-bridged complex derived from [MnIII(salpn)] and [FeIII(CN)6]: Synthesis,structure and magnetic properties

The reaction of the neutral [Mn(salpn)C(CN)₃(H₂O)] (salpn^2 − = N,N^′-1,3-propylenebis(salicylideneiminato) dianion) with [Fe^III(CN)₆]^3 − in the presence of strong oxidizer (NH₄)₂S₂O₈ yields a binuclear anion complex [NH₃CH₂CH₂CH₂NH₃]^2 +{[Mn^III(salpn)(H₂O)][Fe^III(CN)₆]}^2 − (1). Its structure, DC and AC susceptibility have been studied. Frequency dependence of the AC susceptibility characteristic for single-molecule magnets has been found.     

Oligocyanometallic cords as building blocks in luminescent three-dimensional coordination polymers: [Ag4Cd2(tren)2(CN)6.5][Ag(CN)1.5] and [Au2Cd(tren)(CN)4]·H2O

The syntheses, structures and luminescent properties of two unusual mixed-metal coordination polymers, namely [Ag₄Cd₂(tren)₂(CN)_7.5][Ag(CN)_1.5] 1 and [Au₂Cd(tren)(CN)₄]·H₂O 2 (tren = tris(2-aminoethyl)amine), are presented. Both compounds contain abnormal metal cords of oligocyanometallic anions as building blocks wherein the d¹⁰–d¹⁰ interaction plays a crucial role in the metal–metal assembly.     

Two helical one-dimensional copper(II) coordination polymers based on N-(2-hydroxylbenzyl)glycine and N-(2-hydroxylbenzyl)-l-alanine: Syntheses,crystal structures and magnetic studies

Two new helical Cu(II) coordination polymers, [Cu(2,2′-bpy)(Hsgly)]Cl · 2H₂O(H₂sgly = N-(2-hydroxylbenzyl)glycine) (1) and [Cu(2,2′-bpy)(Hsala)](NO₃) · 2H₂O(H₂sala = N-(2-hydroxylbenzyl)-l-alanine) (2) were synthesized. Single crystal X-ray diffraction analysis indicated that both complexes showed helical chains arrangement of Cu(II) centers bridged by carboxyl groups. The magnetic measurements showed complex 1 exhibited ferromagnetic interaction while there was no interaction between the Cu(II) centers in complex 2.     

Microporous metal–organic frameworks constructed by Cu(I)/Zn(II), Tpt and 1,4-benzenedicarboxylate

Two novel metal–organic frameworks, [Cu(tpt)(bdc)_1/2]_n · nH₂O (1) and [Zn(tpt)(bdc)_1/2I]_n (2) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, H₂bdc = 1,4-benzenedicarboxylic acid), have been prepared by hydrothermal reactions. In complex 1, Cu(I) center is in a trigonal coordination environment with bidentate tpt coordinating Cu(I) atoms to form 1D zigzag chains, and bdc ligand links the zigzag chains to form a 2D layered structure. In complex 2, Zn(II) center is in a trigonal–pyramidal environment with bidentate tpt coordinating Zn(II) atoms to form zigzag chains, and bdc links the zigzag chains to form metal–organic framework which contains interesting hexagonal nano-channels.     

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl₂(L)₄], trans-[Ru(NO)Cl (L)₄](PF₆)₂ (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)₄]Cl₂ (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and ¹H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl₂(L)₄] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl₂(L)₄] and trans-[Ru(NO)Cl(L)₄]²⁺ increase in the order py < isn < 4-acpy. The stretching band frequency, ν_NO, of the nitrosyl complexes ranges from 1913 to 1852 cm^?1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H₂O)(py)₄]³⁺ than in trans-[Ru(NO)(H₂O)(NH₃)₄]³⁺.     

An unique trinuclear triply bridged Cu(II) compound containing double acetato and single azido bridges: Synthesis,X-ray structure and magnetism of [Cu3(dpyam)2(μ1,1-N3)2(μ-CH3COO- κ-O1)2(μ-CH3COO-κ-O1,O2)2] · 2(H2O) (dpyam = di-2-pyridylamine)

The synthesis, characterization, crystal structure and magnetic properties of the unique azido-acetato bridged trinuclear triply bridged Cu(II) compound, [Cu₃(dpyam)₂(μ_1,1-N₃)₂(μ-CH₃COO-κ-O¹)₂(μ-CH₃COO-κ-O¹,O²)₂] · 2(H₂O), is reported. In the centrosymmetric compound, the central Cu atom is linked to two terminal Cu atoms by a double acetato bridge and an azido bridge, thereby providing a linear trinuclear unit. The coordination geometry around each of the terminal Cu(II) ions is distorted square pyramidal, while the geometry of the central Cu(II) ion is elongated octahedral. The magnetic susceptibility measurements, measured from 5 to 300 K revealed a weak antiferromagnetic interaction between the Cu(II) ions with a J value of −10.2 cm⁻¹. In the EPR no signals for the low-lying doublet are resolved at 77 K.     

Solvent-controlled synthesis and reversible dynamic structural conversions of a series of iron(II) coordination complexes

In this work, a versatile multi-dentate 1,2-bis(pyridin-4-ylmethylene)hydrazine (L) ligand has been employed to construct three novel iron(II) coordination complexes, [Fe(L)₂(NCS)₂(H₂O)₂]·2H₂O (1), [Fe(L)(NCS)₂(H₂O)₂] (2) and {[Fe(L)₂(NCS)₂]·2CH₃OH}_n (3) (NH₄NCS = ammonium thiocyanate), which can be isolated under similar synthetic conditions, only different molar ratio of metal/ligand or different solvent systems are used. 1 is a mono-nuclear iron(II) coordination complex, and 2 is a one-dimensional (1D) iron(II) coordination complex, while 3 is a 2D micro-porous iron(II) framework with the channel dimensionality of 13.936(3) Å × 13.936(3) Å. PXRD patterns also confirm the purity of the bulky samples of 1–3. For 1–3, it represents the first example of solvent-induced drastic reversible dynamic conformation between different dimensional iron(II) coordination complexes 1 (0D), 2 (1D) and 3 (2D) (for 1: water; for 2: benzene; for 3: methanol/acetone/acetonitrile), which are unambiguously confirmed by PXRD characterizations. Variable-temperature magnetic susceptibility data of 2–3 have been recorded in the 2–300 K temperature range, indicating weak antiferromagnetic interactions.     

Spectroscopic studies on bis(1-amidino-O-alkylurea) copper(II) sulfate complexes where alkyl = methyl,ethyl, n-propyl or n-butyl: EPR evidence for binuclear complexes

Four new Cu(II) Complexes viz. [Cu(II)(1-amidino-O-methylurea)₂]SO₄·2H₂O (1), [Cu(II)(1-amidino-O-ethylurea)₂](SO₄)₂·2H₂O (2), [Cu(II)(1-amidino-O-n-propylurea)₂] SO₄·2H₂O (3), [Cu(II)(1-amidino-O-n-butylurea)₂]₂(SO₄)₂·2H₂O (4) have been synthesized and characterized. EPR spectrum of complex 4 at RT consisted of fine-structure transitions (ΔMs = ±1) with zero-field splitting (ZFS) of 0.0485 cm^?1 and a half-field signal (ΔMs = ±2) at ca. 1600 G, revealed formation of binuclear complex (S = 1). Whereas EPR spectrum of complex 2 in DMSO showed a mixture of mononuclear and binuclear complex in the ratio 0.75:1.0 with ZFS of 0.0385 cm^?1. From the temperature dependence of the EPR signal intensity, the isotropic exchange-interaction constant J was evaluated.     

Synthesis,characterization and photoluminescence properties of copper(II)–azido/thiocyanato complexes with thiazolylazo dye and1,2-bis(diphenylphosphino)ethane

A series of copper(II) complexes of the formula [Cu(L)(dppe)(N₃)₂] (1a–3a) and [Cu(L)(dppe)(NCS)₂] (1b–3b) (where L = 4-(2′-thiazolylazo)chlorobenzene (L₁); 4-(2′-thiazolylazo)bromobenzene (L₂) and 4-(2′-thiazolylazo)iodobenzene (L₃); dppe = cis-1,2-bis(diphenylphosphino)ethane) has been prepared and characterized on the basis of their elemental analysis, molar conductance, magnetic moment, IR, UV–vis and ¹H NMR spectral studies. The electrochemical behaviour of the complexes showed that the redox responses of copper(II) complexes shifted to more negative potential in order of decrease in electron withdrawing nature of the substituent on the azo ligands. All the complexes exhibit intraligand (π→π*) fluorescence in blue-green region with high quantum yield in DMF solution.     

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.     

Copper(II) complexes with chiral reduced Schiff bases: Helical self-assembly via intermolecular C–H⋯O interactions

Copper(II) complexes having the general formula [Cu(Lⁿ)₂] with the N,O-donor reduced Schiff bases N-(2-hydroxy-5-X-benzyl)-(R)-α-methylbenzylamine and N-(2-hydroxy-5-X-benzyl)-(S)-α-methylbenzylamine (X = Cl and Br) (HLⁿ) are described. These chiral complexes crystallize in the noncentrosymmetric P2₁2₁2₁ (X = Cl) and P2₁ (X = Br) space groups. In each case, self-assembly via intermolecular C–H⋯O interaction leads to a supramolecular helical superstructure.