Comparison of HPLC and NMR characterization of the stereogenic properties of cyclotriphosphazene derivatives containing two equivalent centres of chirality: Cis (meso) and trans (racemic) isomers

The di-spiro derivatives of the reaction of gem-disubstituted cyclotriphosphazenes, N₃P₃Cl₄X₂ (X = Ph, PhS, PhNH, PhO) with 3-amino-1-propanol are expected to exist as cis and trans geometric isomers and exist as meso and racemic, respectively. The geometric isomers were separated by column chromatography on silica gel and analyzed by elemental analysis, mass spectrometry, and ³¹P and ¹H NMR spectroscopies. The stereogenic properties of all the compounds (trans, 2a–5a) and (cis, 2b–5b) were investigated by ³¹P NMR spectroscopy on the addition of a chiral solvating agent (CSA), (S)-(+)-2,2,2-trifluoro-1-(9′-anthryl)ethanol; one example of a derivative with the trans configuration (compound 5a, X = PhO) has been found where the ³¹P NMR/CSA method does not lead to the expected separation of the signals of enantiomers, even up to a molar ratio of CSA:compound of 50:1. On the other hand, chiral HPLC methods have been developed in order to characterize the trans (2a–5a) and cis (2b–5b) forms of the cyclotriphosphazene derivatives and give good separation of enantiomers for the trans disubstituted compounds (2a–5a). It is found that chiral HPLC is more reliable than the ³¹P NMR/CSA method for characterising the stereogenic properties of the cis and trans isomers of di-spiro 3-amino-1-propanoxy cyclophosphazene derivatives.     

Supramolecular assembly of 1,3-diaminopropane and its unusual conversion by macrocyclic nickel(II) complex

The reaction of macrocyclic nickel(II) complex [NiL](ClO₄)₂ (1) with 1,3-diaminopropane affords a novel complex with the formula [NiL(a.a.)₂](ClO₄)₂ (2), where L = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, a.a. = H₃N⁺(CH₂)₄COO⁻(5-aminovaleric acid ion), which reveals that the organic ligand 1,3-diaminopropane is converted during the process of the reaction.     

Self-assembly and guest binding of nickel(II) macrocyclic complex with pentyl groups and cis,cis-1,3,5-cyclohexanetricarboxylic acid

Reaction of the nickel(II) macrocyclic complex 1 including pendant pentyl groups in MeCN/H₂O mixed solvent with deprotonated cis,cis-1,3,5-cyclohexanetricarboxylic acid (CTC^3 −) resulted in two-dimensional (2-D) coordination polymer [Ni(C₁₈H₄₂N₆)]₃[C₆H₉(COO)₃]₂·6H₂O·6CH₃CN (2). The crystal structure of 2 indicates that each nickel(II) macrocyclic unit binds two CTC^3 − ions in trans position and each CTC^3 − ion coordinates three nickel(II) macrocyclic complexes to form a 2-D layer with hexagonal motif. The dried solid of 2 differentiates MeOH, EtOH, and PhOH in toluene solvent with the K_f values of 1.38, 2.11, and 6.68 M^− 1, respectively.     

Syntheses,structures, and properties of two dinuclear palladium (II) complexes of a single macrocyclic hexaaza ligand with two hydroxyethyl pendants

Two dinuclear palladium (II) complexes, trans-[Pd₂LCl₂](ClO₄)₂ · 2H₂O and cis-[Pd₂LCl₂]Cl₂ · 2H₂O, of a single macrocyclic ligand with two hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2^11,14]triaconta-1,11,13,24,27,29-hexaene), have been synthesized as “inorganic proteases” and analyzed by X-ray diffraction method. The two complexes-mediated hydrolytic cleavage of amide bond in acetyl methionyl alanine has been monitored by ¹H NMR, showing a moderate hydrolytic rate at 50 °C and pH ca. 1.0. The pendent hydroxyl group is responsible for the hydrolytic reaction.     

Ru(II)–CO complexes of thioarylazoimidazoles: Syntheses,structures, spectroscopy and DFT calculation

The complexes, cis-(CO)-trans-(Cl)-[Ru(SRaaiNR)(CO)₂Cl₂] (2) and trans-(Cl)-[Ru(SRaaiNR)(CO)Cl₂] (3) (SRaaiNR = 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles; R = Me (1a) and Et (1b)) have been synthesized and characterized. The structural confirmation is achieved by single crystal X-ray structure determinations. The complexes show Ru(III)/Ru(II) couple and ligand reductions. Electronic structure and spectral properties of the complexes have been explained with the DFT and TDDFT calculation.     

Hydrothermal synthesis and characterization of a 3D luminescent lead(II) framework containing 3D Pb–X–Pb linkage (X = O and Cl) tuned by cis- and trans-ligand conformations

Under hydrothermal conditions using cis-butenedioic acid (H₂L) and corresponding lead(II) salts, a three-dimensional (3D) lead(II) complex {[Pb₂(L)(μ₂-Cl)(μ₃-Cl)]}_n (1) containing 3D Pb–X–Pb (X = O and Cl) linkage has been isolated. 1 also represents a truly 3D hybrid luminescent lead(II) framework with I³O⁰ type connectivity. Further analysis reveals that cis- and trans-conformations of butenedioic acid ligand greatly affect the lead(II) framework structure. Solid-state fluorescence spectrum of 1 exhibits the maximum emission peak at 379 nm.     

Tautomerism of a compartmental Schiff base ligand and characterization of a new heterometallic CuII–DyIII complex — Synthesis,structure and magnetic properties

A crystal structure of a compartmental ligand N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane (H₄L = C₁₇H₁₈N₂O₄) (1) containing N₂O₂-inner and O₄-outer coordination sites and a characterization of its novel diphenoxo-bridged discrete dinuclear complex [CuDy(H₂L)(MeOH)(NO₃)₃]·2MeOH (2) are reported. The Schiff base ligand 1 crystallizes in the orthorhombic P2₁2₁2₁ space group with a molecule in a bent conformation. The compound at 100 and 293 K displays the keto-enol tautomerism with the equilibrium in both temperatures shifted with a different degree towards the zwitterionic keto-amino form. The quantum chemical calculations showed preferences for enol-imino form in a gas phase and for keto-amine in solutions. The keto-amino tautomer is stabilized by intermolecular interactions. The complex 2 crystallizes in the triclinic P-1 space group as a dinuclear compound with Cu^IIDy^III core. The Dy(III) ion is nine-coordinated whereas the coordination number of Cu(II) is five. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicated that the interaction between Cu(II) and Dy(III) metal centers in 2 is ferromagnetic.     

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.     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.     

A novel 1-D coordination polymer constructed from disilver-1,3,4-oxadiazole nodes and perchlorato bridges

The reaction of silver perchlorate with 2-phenyl-5-(p-tolyl)-1,3,4-oxadiazole (L) affords a 1-D coordination polymer, [Ag₃L₄(ClO₄)₃] (1). Two silver ions are bridged by two L ligands, through the nitrogen atoms of the oxadiazole ring, resulting in binuclear units. The coordination polymer is constructed from binuclear nodes, {Ag₂L₂}, connected by perchlorato bridges. The investigation of the optical properties of compound 1 indicates a slight change in the emission profile compared to the organic ligand, showing blue luminescence upon excitation at λ = 300 nm.     

Complexation and electrochemical study of 1,5-diselena[5]ferrocenophane: X-ray crystal structures of 1,5-diselena[5]ferrocenophane,and silver,mercury complexes

The silver(I) and mercury(II) complexes of 1,5-diselena[5]ferrocenophane (L) have been synthesized. The X-ray crystal structures of L, [AgL₂]PF₆ and [HgI₂L] are reported. The small cavity of the macrocyclic ligand means that the ring must undergo a conformational change to allow coordination, and there is no significant through-space interaction M?Fe in any of the complexes. Electrochemical studies showed that no electronic communication between ferrocenylene groups was observed in the silver complex where the through-bond Fe···Fe distances are in the range 13.10 (3)–13.27(3) Å.     

A new helical coordination polymer constructed on flexible dicarboxylate ligand and CdII center: Structure and luminescence

A novel cadmium coordination polymer [Cd₂L₂(bpp)₂]_n (1) (H₂L = 1,3-adamantanediacetic acid and bpp = 1,3-di-4-pyridylpropane) was prepared under hydrothermal condition. The three-dimensional (3D) structure is built from the interlinking lamellars. The Cd^II ions are six- and seven-coordinated and linked by L^2? ligands, which results in the right- and left-handed helical chains. The layers are stacked with each other via bpp to generate a 3D architecture. At room temperature, the complex 1 shows the strong fluorescent emission bands in the solid state.     

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.     

The first substituted macrocyclic ligand Py2N4S2 containing four naphthylmethylene pendant-armed groups: Synthesis and photophysical properties

The synthesis of a pendant donor emissive macrocyclic ligand Py₂N₄S₂ with up to four naphthylmethylene arms (L) has been achieved. Their derivative solid metal complexes (Co^2 +, Ni^2 +, Cu^2 +, Zn^2 +, Cd^2 +, Hg^2 + and Ag⁺) have been isolated and characterized. The photophysical properties of the free ligand L and their complexation behaviour have been investigated in solution. In dichloromethane, the free ligand presents two emission bands which are related to the monomer naphthalene emission and a red-shifted band attributable to ground state dimers (interaction between two naphthalene chromophores), which was further validated from time-resolved data, with bi-exponential decay with absence of dynamic components. UV–Vis spectroscopy has revealed a 2:1 binding stoichiometry for Co^2 +, Cu^2 +, Zn^2 +, Hg^2 + and Ag⁺.     

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).     

Solvothermal in situ synthesis of (Schiff-base)-containing dinuclear cobalt compound

A new dinuclear cobalt compound, namely Co₂(L)(H₂O)Cl₂ (1, H₂L = N,N′-o-phenylenebis(salicylide-neimine) was obtained by one-pot solvothermal self-assembly of CoCl₂, 1,2-phenylenediamine, and salicylaldehyde in C₂H₅OH. The magnetic studies suggest weak antiferromagnetic behavior and the magnetic data were interpreted by means of a dinuclear cobalt model with the parameters of g = 2.12, J = ?1.25 cm^?1, θ = ?3.12 K.     

A new stable Cd(II)-framework for sensitive and selective detection of Cu2 + ions

A new water-stable 3D metal–organic framework (MOF), [Cd₂L₂]·NMP·MeOH (1, H₂L = 2-(3,5-dimethyl-1H-pyrazol-4-yl)-1,3-dioxoisoindoline-5,6-dicarboxylic acid, NMP = 1-methyl-2-pyrrolidinone) has been solvothermally synthesized and structurally characterized. 1 exhibits a 3D open-framework with a 2D metallic plane pillared by L^2 − fragments. Meanwhile, luminescent studies indicate that the luminescence intensity of 1 was strongly dependent on different metal ions. Most interestingly, 1 exhibited significantly quenching effect toward Cu^2 +, which implies that it may be used as a luminescent probe for the detection of Cu^2 +.     

Synthesis and characterization of dinuclear copper(II) complexes, [Cu2([20]-DCHDC)(La)2] (La = N3−, NCS− or S2O32−) with tetraazadiphenol macrocyclic ligand having cyclohexane rings

The chiral dinuclear tetraazadiphenol macrocyclic copper(II) complexes [Cu₂([20]-DCHDC)(L_a)₂] {H₂[20]-DCHDC = 14,29-dimethyl-3,10,18,25-tetraazapentacyclo-[25,3,1,0^4,9,1^12,16,0^19,24]ditriacontane-2,10,12,14,16(32),17,27(31),28,30-decane-31,32-diol; L_a = N₃^? (II), NCS^? (IV) or S₂O₃^2? (V)} has been synthesized and structurally characterized by elemental analysis, conductance, electronic and IR spectra as well as FAB-MS method. Crystal structure of [Cu₂([20]-DCHDC)(N₃)₂]·2CH₃OH (III) determined by X-ray crystallography reveal the two square pyramidal copper centers bridged by the two phenoxide oxygen atoms, with large Cu–O–Cu angles {100.88(10)°}.     

Two nickel coordination polymers with flexible ligand 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene

The reaction of 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (ttmb) with Ni(II) salts yields two coordination polymers [Ni₃(ttmb)₂(H₂O)₆Cl₆](H₂O)₃ (1) and [Ni(ttmb)₂(H₂O)₂](NO₃)₂(H₂O)₄ (2). The flexible ligand ttmb shows the cis,cis,cis-conformation and a tri-monodentate coordination mode in 1. Each ttmb links three Ni(II) atoms to form an undulated (3, 4)-connected two-dimensional network. Each undulated two-dimensional network polycatenates other two identical networks, thus giving a rare (2D → 3D) parallel polycatenation network in 1. The ttmb ligand exhibits the cis,trans,trans-conformation and a two-monodentate coordination mode in 2. Each ttmb connects two Ni(II) atoms to construct a two-dimensional (4, 4) network in 2. The thermal stability of compounds 1 and 2 was studied.