Synthesis, Crystal Structures, Magnetic Properties and Catecholase Activity of Double Phenoxido-Bridged Penta-Coordinated Dinuclear Nickel(II) Complexes Derived from Reduced Schiff-Base Ligands: Mechanistic Inference of Catecholase Activity

Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni(2)(L(1))(2)(NCS)(2)] (1), [Ni(2)(L(2))(2)(NCS)(2)] (2), and [Ni(2)(L(3))(2)(NCS)(2)] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL(1)), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL(2)), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL(3)), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter τ = 0.47) and 3 (τ = 0.29), while it is almost perfect for 2 (τ = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm(3) K mol(-1), in the convention H = -2JS(1)S(2)). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes.     

Synthesis and Crystal Structures of Dinuclear Palladium and Mononuclear Nickel Complexes of Macrocyclic N8S4 Ligands

The N₈S₄ donor ligand L¹ has been investigated regarding its capability to support the formation of coordinatively unsaturated Pd₂ complexes and its use as a starting material for functionalized N₈S₄ systems. L¹ represents a macrotricyclic ligand comprising four 4‐tert‐butyl‐2,6‐bis(aminomethyl)thiophenolate units, whose N and S atoms are linked by ethylene units. Treatment of L₁ with [Pd(NCMe)₂Cl₂] produced the dinuclear complex [Pd₂Cl₂(H₂L¹)]⁴⁺, which was isolated as its pale‐yellow perchlorate salt [Pd₂Cl₂(H₂L¹)](ClO₄)₄ (H₂ 1 ) and characterized by elemental analysis, IR, NMR and MS spectroscopy and X‐ray crystallography. The structure shows two planar PdN₂SCl units which are located in the central 24‐membered ring of L¹. Reaction of L¹ with CH₂O/HCO₂H under Eschweiler‐Clarke conditions followed by deprotection with sodium in liquid ammonia furnished the permethylated octaamine‐tetrathiophenol H₄L⁴. The identity of H₄L⁴ was ascertained by an X‐ray crystal structure determination of one of its metal complexes.     

Syntheses of Acyclic and Macrocyclic Compounds Derived from 9,9-Diethylfluorene (Part I)

A series of new 9,9-diethylfluorenes consisting of three side-arms each bearing a heterocyclic, bis(carboxymethyl)amino, bis(carbamoylmethyl)amino, bis(ethoxycarbonylmethyl)amino or an amino group were prepared on the basis of 2,4,7-tris(bromomethyl)-9,9-diethylfluorene. Imidazolyl, benzimidazolyl, pyrazolyl, pyrrolyl, 1,3-dioxoisoindolyl and pyridinium groups were taken into account as heterocyclic units, attached to the aromatic skeleton via −CH₂−, −CH₂NHCH₂− or −CH₂N=CH− linkers. In addition to the seventeen 2,4,7-trisubstituted 9,9-diethylfluorenes, two macrocyclic compounds were prepared on the basis of 2,7-bis(aminomethyl)-9,9-diethylfluorene. The excellent yield of the macrocyclization reaction is worth a special mention. Both the acyclic and the macrocyclic fluorene-based compounds have, among other things, the potential to act as artificial receptors for different substrates in analogy to the known receptors consisting of a benzene or biphenyl core.     

氮杂穴状大环钴(Ⅱ)配合物的合成、晶体结构及其催化性能

以一个氮杂穴状大环配体为自由配体,与硝酸钴经配合反应合成了一个新的穴状单核钴配合物[CoL(NO_3)]·(NO_3)·8H_2O(1),其晶体结构经X-射线单晶衍射表征。采用紫外-可见分光光度法对1催化p-硝基苯酚醋酸酯(NA)的水解动力学性质进行了研究。结果表明:催化水解速率对底物(NA)及配合物浓度均呈一级反应,催化水解速率受酸碱平衡影响。     

Synthesis and Metal-Binding Properties of Polybipyridine Ligands Derived from Acyclic and Macrocyclic Polyamines

Synthetic procedures have been developed for the preparation of ligands bearing two to six pendent, unsubstituted or substituted 2, 2′-bipyridine groups attached to acyclic (tripode, tetrapode) and macrocyclic (triazanonade-cane, cyclam, hexacyclen, bis(bipyrido)hexaazamacrocycle) polyamines. Ligands 1-5 have been obtained in high yield by condensation of 6-(bromomethyl)-2, 2′-bipyridine ( 9b ) with the corresponding amines in the presence of NaOH, H₂O, and MeOH. Ligands 6-8 have been prepared in good yield by condensation of 9b or the di- or tetrasubstituted mono (bromomethyl) bipyridine 10b or 11b , respectively, with the corresponding amines in the presence of Na₂CO₃ and MeCN. Ligand 1 forms hemi-cage complexes with Ru^II, Fe^I, Cr^II, and Cr^III cations and trinuclear complexes with [RuCl²(bpy)²] and [ReCl(CO)⁵]. Tetrapode 2 and hexapode 4 gave tetranuclear and dinuclear complexes, respectively, by reaction with Fe11 salts. These complexes possess a variety of interesting physical and chemical properties.     

Dinuclear vs. Mononuclear Copper(II) Coordination Species of Tylosin and Tilmicosin in Non-Aqueous Solutions

The veterinary 16-membered macrolide antibiotics tylosin (HTyl, 1a) and tilmicosin (HTilm, 1b) react with copper(II) ions in acetone at metal-to-ligand molar ratio of 1:2 to form blue (2) or green (3) metal(II) coordination species, containing nitrate or chloride anions, respectively. The complexation processes and the properties of 2–3 were studied by an assortment of physicochemical techniques (UV-Vis, EPR, NMR, FTIR, elemental analysis). The experimental data revealed that the main portion of copper(II) ions are bound as neutral EPR-silent dinuclear complexes of composition [Cu₂(µ-NO₃)₂L₂] (2a–b) and [Cu₂(µ-Cl)₂Cl₂(HL)₂] (3a–b), containing impurities of EPR-active mono-species [Cu(NO₃)L] (2a’–b’) and [CuCl₂(HL)] (3a’–b’). The possible structural variants of the dinuclear- and mono-complexes were modeled by the DFT method, and the computed spectroscopic parameters of the optimized constructs were compared to those measured experimentally. Using such a combined approach, the main coordination unit of the macrolides, involved in the complex formation, was defined to be their mycaminosyl substituent, which acts as a terminal ligand in a bidentate mode through the tertiary nitrogen atom and the oxygen from a deprotonated (2) or non-dissociated (3) hydroxyl group, respectively.     

2,2'-硫代-二(苯甲酸)和双吡啶配体构筑的三个双核锌配位聚合物

用水热法合成了3个配位聚合物并测定了其晶体结构,分子式分别为[Zn₂(tba)₂(bpy)]_n(1),[Zn₂(tba)₂(bpe)]_n(2)和[Zn(tba)(bpp)]n(3),(tba=2,2''-thiobis(benzoic acid),bpy=4,4''-bipyridine,bpe=1,2-bis(4-pyridyl)ethylene,bpp=1,3-bis(4-pyridyl)propane)。tba是由2-(2-cyanophenylthio)benzoicacid原位水解得到的。X射线单晶衍射分析表明配合物1含双核锌单元,由tba和bpy连成二维(4,4)网。配合物2是基于[Zn₂(tba)₂]_n子链,由bpe连接而成的钻石拓扑三维结构。有趣的是,配合物3是一个由(4,4)网交缠形成的二维到二维的聚索烃。Tba配体构型和各双吡啶辅助配体引起了3个化合物的结构各异性。此外,研究了3个配位聚合物的荧光性质。     

2, 2'-硫代-二(苯甲酸)和双吡啶配体构筑的三个双核锌配位聚合物

用水热法合成了3个配位聚合物并测定了其晶体结构, 分子式分别为[Zn₂(tba)₂(bpy)]_n (1), [Zn₂(tba)₂(bpe)]_n (2)和[Zn(tba)(bpp)]_n (3), (tba=2, 2''-thiobis(benzoic acid), bpy=4, 4''-bipyridine, bpe=1, 2-bis(4-pyridyl)ethylene, bpp=1, 3-bis(4-pyridyl)propane)。tba是由2-(2-cyanophenylthio)benzoic acid原位水解得到的。X射线单晶衍射分析表明配合物1含双核锌单元, 由tba和bpy连成二维(4, 4)网。配合物2是基于[Zn₂(tba)₂]_n子链, 由bpe连接而成的钻石拓扑三维结构。有趣的是, 配合物3是一个由(4, 4)网交缠形成的二维到二维的聚索烃。Tba配体构型和各双吡啶辅助配体引起了3个化合物的结构各异性。此外, 研究了3个配位聚合物的荧光性质。     

Synthesis,Characterization and Crystal Structures of New Difurylphosphido-bridged Dinuclear Ruthenium Carbonyl Complexes Derived from Ferrocenylacetylene Ligands

The difurylphosphido-bridged dinuclear complex [Ru₂(CO)₆(μ-PFu₂)(μ-η¹,η²-Fu)] (Fu = 2-furyl) 1 readily reacts with two equivalents of each of the terminal alkynes HC≡CR (R = Fc, p-C₆H₄Fc, p-C₆H₄NO₂, Fc = Fe(η⁵-C₅H₅)(η⁵-C₅H₄)) by an interesting head-to-tail ynyl coupling with a furan group to form a series of phosphido-bridged diruthenium compounds containing a novel furyl-substituted C₄ hydrocarbyl chain of stoichiometry [Ru₂(CO)₄(μ-PFu₂){μ-η¹,η¹,η²,η³-RCC(H)C(R)C(H)Fu}] (R = Fc 2, p-C₆H₄Fc 3, p-C₆H₄NO₂ 4) in moderate to good yields. Reaction of 1 with an equimolar amount of HC≡CFc and HC≡C(p-C₆H₄NO₂) afforded a pair of isomers of [Ru₂(CO)₄(μ-PFu₂){μ-η¹,η¹,η²,η³-R¹CC(H)C(R²)C(H)Fu}] (R¹ = Fc, R² = p-C₆H₄NO₂ 5a; R¹ = p-C₆H₄NO₂, R² = Fc 5b) together with a small mixture of 4. X-ray crystal structures of 2, 3, 5a and 5b are reported. All of these new alkyne-derived dinuclear complexes are electron precise with 34 cluster valence electrons in which the μ-η¹,η²-furyl ligand acts as a three-electron donor and the μ-phosphido Ru₂ framework is retained in the products upon alkyne coupling reactions. The resulting organic fragment of each complex is coordinated to the Ru atoms via a π, a π-allyl and two σ bonds, and donates seven electrons to the metal core. Dedicated to the memory of Professor F. Albert Cotton.     

Into the Next Dimension: Nanometer-Sized, Oligonuclear Coordination Compounds with C(3)-Symmetric Ligands

Nanometer-sized cavities are present in oligonuclear coordination compounds formed in molecular self-assembly processes from C(3)-symmetric ligands and appropriate metal complex fragments. The structures obtained can be described as basic polyhedra such as tetrahedron, hexahedron, or octahedron (see picture).     

Copper(II) 2,2-Bis(Hydroxymethyl)Propionate Coordination Compounds with Hexamethylenetetramine: From Mononuclear Complex to One-Dimensional Coordination Polymer

Three new copper coordination compounds derived from 2,2-bis(hydroxymethyl)propionic acid (dmpa) and hexamethylenetetramine (hmta) were obtained and their crystal structures were determined. The stoichiometry of the reagents applied in the syntheses reflects the metal to ligand molar ratio in the formed solid products. Due to the multiple coordination modes of the used ligands, wide structural diversity was achieved among synthesized compounds, i.e., mononuclear [Cu(dmp)₂(hmta)₂(H₂O)] (1), dinuclear [Cu₂(dmp)₄(hmta)₂] (2), and 1D coordination polymer [Cu₂(dmp)₄(hmta)]_n (3). Their supramolecular structures are governed by O—H•••O and O—H•••N hydrogen bonds. The compounds were characterized in terms of absorption (UV-Vis and IR) and thermal properties. The relationships between structural features and properties were discussed in detail. Owing to discrepancies in the coordination mode of a dmp ligand, bidentate chelating in 1, and bidentate bridging in 2 and 3, there is a noticeable change in the position of the bands corresponding to the stretching vibrations of the carboxylate group in the IR spectra. The differences in the structures of the compounds are also reflected in the nature and position of the UV-Vis absorption maxima, which are located at lower wavelengths for 1.     

手性1，4-二胺构建的双核铜[2+2]席夫碱大环化合物：制备和催化研究

Dinuclear copper(Ⅱ) complexes of [2+2] macrocyclic Schiff bases have been prepared from chiral 1,4-diamines using sodium ions as template. Catalytic investigation on the titled complexes has been carried out on model reactions (asymmetric sulfoxidation and asymmetric oxidative-coupling reactions).     

Allopurinol- and Hypoxanthine-Copper(II) Compounds. Spectral and Magnetic Studies of Novel Dinuclear Coordination Compounds with Bridging Hypoxanthine

The synthesis in aqueous solution and pH = 1.0 of several novel Cu(II) compounds with allopurinol and hypoxanthine as heterocyclic ligands and X = Cl(-), Br(-), NO(3)(-), SO(4)(2-), and ClO(4)(-) as anions, together with their spectral and magnetic characterization, is reported. The studies of the Cu(II) systems with these heterocycles and Cl(-) or Br(-) support their Cu(II)(L)(2)(X)(2) character and their interactions through halogen atoms as bridging ligands, leading to a very weak antiferromagnetic coupling. For the Cu(II) compounds with hypoxanthine and X = NO(3)(-), SO(4)(-), or ClO(4)(-), new examples of the cupric acetate type are obtained, showing in all cases similar strong antiferromagnetic coupling. These three cases are new examples of the scarce Cu(II) dinuclear compounds with bridging hypoxanthine which have been reported up to now.     

Ionic Ferrocenyl Coordination Compounds Derived from Imidazole and 1,2,4‐Triazole Ligands and Their Catalytic Effects During Combustion

Alkylferrocene‐based burning‐rate catalysts (BRCs) show conspicuous migration tendency and volatility during prolonged storage and fabrication process of a composite solid propellant. To enhance anti‐migration ability of the BRCs, forty novel ionic coordination compounds, [M(L)₄(H₂O)₂]_mX_n (M = Mn²⁺, Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Pb²⁺, Cr³⁺, Bi³⁺, or Cd²⁺; L = ferrocenylmethyl imidazole or ferrocenylmethyl‐1,2,4‐triazole; X = picrate or trinitroresorcinolate), were synthesized and characterized by FT‐IR, UV/Vis, and elementary analysis. Additionally, the crystal structures of six compounds were confirmed by single‐crystal X‐ray diffraction. The TG analyses revealed that the new compounds show high thermal stability. Cyclic voltammetry studies suggested that theyare irreversible redox systems. Their catalytic activities in the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclo‐hexane (RDX) and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were examined by DSC technique. The results indicated that all the new compounds exert great effects on the thermal decomposition of AP and RDX, among them some compounds are more active than catocene. Compound 26 has good catalytic ability in the thermal decomposition of HMX, representing a rare example of the reported ferrocene‐based BRCs which show catalytic activity during combustion of HMX.     

A Series of Mononuclear Complexes Constructed from Transition Metals and Amino Acid Derived Ligands: Syntheses, Structures and Photoluminescence

Eight neutral mononuclear complexes constructed from transition metals （M = Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ）, Zn（Ⅱ）, Cd（Ⅱ）） and ligands N-（2-pyridylmethyl）-L-phenylalanine （L-Hpmpa） and N-（2-pyridylmethyl）-L-tyrosine （L-Hpmtyr） have been synthesized by both hydrothermal and conventional room temperature reactions. Four of them have been structurally characterized by single-crystal X-ray diffractions. They are： [Co（L-pmpa）2·2H2O] 1, [Ni（L-pmpa）2·2H2O] 2, [Cu（L-pmpa）2·2H2O] 3 and [Cu（L-pmtyr）2·2H2O] 4. Single-crystal X-ray analysis, IR and elemental analysis revealed that complexes 1, 2 and 3 are isostructural. Powder X-ray diffraction, IR and elemental analysis revealed that complexes 4, 5 （Zn[L-pmtyr]2·2H2O）, 6 （Cd[L-pmtyr]2·2H2O）, 7 （Co[L-pmtyr]2·2H2O） and 8 （Ni[L-pmtyr]2·2H2O） are isostructural. The photoluminescence properties of L-Hpmtyr ligand, compounds 5 and 6 were also investigated.     

Transition-Metal Derivatives of the Cyclopentadienylphosphine Ligands. 11. Reactivity of the Dinuclear Bridged Rhodium(II) Complexes toward Nitrogen-Containing Ligands

We report observations on the reactivity of the dinuclear bridged metal-metal-bonded carbonyl [Rh(II)(CO)(&mgr;-CpPPh(2))](2)(2+) (2(2+)) and of the bis(solvate) cations [Rh(II)(solv)(&mgr;-CpPPh(2))(2)](2)(2+) (3(2+)) with nitriles, amines and pyridine and in general with nitrosyl cation and nitrite anion. By reaction of nitriles and pyridine with 2(2+) we obtained monosubstituted [Rh(2)(CO)L(&mgr;-CpPPh(2))(2)](2+) (4(2+)) and disubstituted [Rh(L)(&mgr;-CpPPh(2))](2)(2+) (5(2+)) (L = MeCN, PhCN, pyridine). These complexes (5(2+)) were also obtained directly from 3(2+). In the reactions with 2(2+) the difference in reactivity of the two rhodium(II) sites suggests a specific role of the metal-metal bond. With secondary and primary amines, reductions of 2(2+) to [Rh(I)(CO)(&mgr;-CpPPh(2))](2) (1) were also observed, and the selectivity with respect to substitution or reduction was strongly solvent dependent. Lithium diisopropylamide induces quantitatively the reduction of 2(2+) to 1 and apparently the substitution of the solvent in 3a(2+). Finally, the new compounds [Rh(II)(THF)(&mgr;-CpPh(2))](2)(2+) (3a(2+)), [Rh(II)(&mgr;-H(2)NC(5)H(4)N)(&mgr;-CpPh(2))(2)](2+) (6(2+)) and [Rh(II)(NO(2))(&mgr;-CpPh(2))](2) (7(2+)) were obtained from 2(2+) and PhIO, from 3(2+) and aminopyridine, and from 2(2+) and nitrite anion, respectively. The compounds were characterized by elemental analysis and the usual spectroscopic methods including COSY NMR experiments. Reaction of NOBF(4) with 1 led efficiently to the compound 2(2+) again through a redox process, instead of a substitution.     

Synthesis and Spectroscopic Characterization of Dinuclear Calcium Complexes with Oxa‐Aza Macrocyclic Ligands

The syntheses of dinuclear calcium perchlorate and/or nitrate complexes by template and direct methods, employing macrocyclic ligands with 18, 20, 22, and 26 membered rings are reported. The presence of pendant arms provide with coordinative NxOy donor atoms in the smaller macrocycles, the high number of donor atoms between 7 and 10, and the dinuclear composition obtained in all the systems examined, point out that in the formed solid complexes both Ca²⁺ ions could be located inside of the macrocycle cavities. Transmetallation reaction of a lanthanide(III) complex, [L⁵Sm](ClO₄)₃·9H₂O, with Ca(ClO₄)₂·xH₂O leads the formation of the new dinuclear orange [L⁵Ca₂](ClO₄)₄·3H₂O complex, manifesting the versatility of this macrocyclic cavity. All complexes have been characterized by microanalysis, IR, UV‐vis, ¹H NMR spectroscopy, FAB mass spectrometry, FAAS spectroscopy, and conductivity measurements.     

Expanded Ligands Based upon Iron(II) Coordination Compounds of Asymmetrical Bis(terpyridine) Domains

The synthesis and characterization of two tritopic ligands containing a 2,2′:6′,2″-terpyridine (tpy) metal binding domain and either a 3,2′:6′,3″- or a 4,2′:6′,4″-tpy domain are detailed. The synthetic routes to these ligands involved the [Pd(dppf)Cl₂]-catalyzed coupling of a boronic ester-functionalized 2,2′:6′,2″-tpy with bromo-derivatives of 3,2′:6′,3″-tpy or 4,2′:6′,4″-tpy. The 2,2′:6′,2″-tpy domains of the tritopic ligands preferentially bind Fe²⁺ in reactions with iron(II) salts leading to the formation of two homoleptic iron(II) complexes containing two peripheral 3,2′:6′,3″-tpy or 4,2′:6′,4″-tpy metal-binding sites, respectively. These iron(II) complexes are potentially tetratopic ligands and represent expanded versions of tetra(pyridin-4-yl)pyrazine.