Assembly of tetra, di and mononuclear molecular cadmium phosphonates using 2,4,6-triisopropylphenylphosponic acid and ancillary ligands

The reaction of ArPO(3)H(2) (Ar = 2,4,6-iPr(3)-C(6)H(2)) with Cd(CH(3)COO)(2).2H(2)O using various co-ligands such as methanol, dimethylformamide (DMF) and 3,5-dimethylpyrazole (DMPZH) resulted in the formation of tetranuclear assemblies [Cd(4)(ArPO(3))(2)(ArPO(3)H)(4)(CH(3)OH)(4)].3(CH(3)OH) (1), [Cd(4)(ArPO(3))(2)(ArPO(3)H)(4)(DMF)(4)].3(DMF) (2) and [Cd(4)(ArPO(3))(2)(ArPO(3)H)(4)(DMF)(2)(DMPZH)(2)].2(DMF).2(H(2)O) (3). In all of these compounds the tetranuclear cadmium array, containing two five-coordinate and two six-coordinate cadmium atoms, is held together by two mu(4) capping [ArPO(3)](2-) and four anisobidentate mu(2) [ArPO(2)(OH)](-) ligands. Each cadmium atom is bound to an additional ancillary ligand. The reaction of ArPO(3)H(2) with Cd(CH(3)COO)(2).2H(2)O in the presence of the chelating ligand 2,2'-bipyridine (bipy) leads to the exclusive formation of the dinuclear assembly [Cd(2)(ArPO(3)H)(4)(bipy)(2)].(CH(3)OH)(H(2)O) (4). The latter contains an eight-membered Cd(2)P(2)O(4) inorganic ring formed as a result of the bridging coordination action of two anisobidentate mu(2) [ArPO(2)(OH)](-) ligands. Each cadmium atom is bound by one chelating bipy and one monodentate [ArPO(2)(OH)](-) ligands. Use of four equivalents of 3,5-dimethylpyrazole leads to the formation of the mononuclear derivative [Cd(ArPO(3)H)(2)(DMPZH)(4)] (5). The molecular structure of the latter comprises of a central cadmium atom surrounded by six monodentate ligands. Four of these are neutral pyrazole ligands that occupy the equatorial plane; the remaining two are anionic phosphinate ligands which are present trans to each other. The thermal analysis of 1 and 4 reveals that the char residue obtained at 600 degrees C consists predominantly of Cd(2)P(2)O(7).     

Cu(I) luminescence from the tetranuclear Cu4S4 cofactor of a synthetic 4-helix bundle

The addition of Cu(I) to the random-coil peptide, C16C19-GGY, produces a self-organized, metal-bridged 4-helix bundle which displays an intense room-temperature luminescence at 600 nm. Emission, UV, and CD titrations along with X-ray absorption studies indicate that the luminescent cofactor is likely a Cu4S4 cluster in which each Cu atom is bridged by the side chains of two cysteine residues and has terminal N/O ligation.     

Mononuclear,dinuclear and hydroxo-bridged tetranuclear complexes from reactions of Cu ions,mandelic acid and diimine ligands

The reaction of copper(II) hydroxocarbonate, mandelic acid (H₂MANO) and 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) in water affords [Cu(bpy)(μ₂-MANO)]₂ · 8H₂O (1), [Cu(bpy)(MANO)] · 4H₂O (2) and the opened tetranuclear hydroxo-bridged copper(II) complexes of formulae [Cu₄(μ₃-OH)₂(μ₂-MANO)₂(bpy)₄](phglyo)₂ · 8H₂O (3) (phglyo = phenylglyoxylate) or [Cu₄(μ₃-OH)₂(μ₂-OH)₂(OH₂)₂(phen)₄](Bza)₂(OH)₂ · 5H₂O (4) (Bza = benzoate), respectively. The compounds have been characterized by spectroscopic techniques and studied by single-crystal X-ray diffractometry. The formation of 3 and 4 takes place in basic media through dehydrogenation or oxidative dehydrogenation followed by in situ oxidative decarboxylation of mandelic acid to phenylglyoxylate or benzoate, respectively. These results indicate that cooperative catalysis of diimine ancillary ligands and copper(II) is essential.     

Anticonvulsant activity and toxicity evaluation of Cu(II) and Zn(II) metal complexes derived from triazole-quinoline ligands

A novel Cu(II) and Zn(II) complexes of triazolo-quinoline derivatives were synthesized by in situ method and were characterized by the spectro-analytical methods and their pharmacological properties were evaluated. The compound C3 has exhibited promising anticonvulsant activity towards the electroshock induced seizures in Wistar rats and possesses low toxicity, providing a high safety profile.     

New palladium(II) complexes with pyrazole ligands

This study describes the synthesis, IR, ¹H, and ¹³C{¹H} NMR spectroscopic as well the thermal characterization of the new palladium(II) pyrazolyl complexes [PdCl₂(HmPz)₂] 1, [PdBr₂(HmPz)₂] 2, [PdI₂(HmPz)₂] 3, [Pd(SCN)₂(HmPz)₂] 4 {HmPz = 4-methylpyrazole}. The residues of the thermal decomposition were identified as Pd⁰ by X-ray powder diffraction. From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 1 > 2 > 4 ≈ 3. The cytotoxic activities of the complexes and the ligand were investigated against two murine cancer cell lines: mammary adenocarcinoma (LM3) and lung adenocarcinoma (LP07) and compared to cisplatin under the same experimental conditions.     

Cu(2+) and Pt(2+) complexes of pyrazole and triazole based dinucleating ligands

A series of pyrazole and triazole based dinucleating ligands have been synthesized and their complexation potential for metal ions, which exhibit square planar coordination geometry has been studied. In the case of Cu(2+) the complexation equilibria in solution have been determined using pH titrations. Species with 1 : 1 stoichiometry [CuLH(n)], 2 : 1 stoichiometry [Cu(2)LH(m)], and of dimeric nature [Cu(2)L(2)H(p)], have been detected and their overall stability constants have been measured. The reactivity of the dinuclear species [Cu(2)LH(-1)] towards phosphate ester hydrolysis have shown that the OH-functionality incorporated in some of the ligands does not enhance the hydrolysis rate. Several ligands were reacted with Pt(2+) to give insoluble dinuclear species [Pt(2)LI(3)]. One of them was studied by X-ray diffraction and shows that the two Pt(2+) are bridged by the pyrazolide group and by one I(-). The remaining two positions are occupied by the amino group in alpha position of the heterocyclic ring and a terminal I(-). The nearly planar [Pt(2)LI(3)] units form sheets in the crystals, which are about 4 A apart and thus indicate pi stacking interactions.     

Effects of the substituents of pyrazole/thiazine ligands on nuclearity of Cu(II) nitrate complexes

[Cu(H₂O)(PzTz)₂](NO₃)₂ (1), [Cu(μ-NO₃)(NO₃)(DMPzTz)] _n (2), and [{Cu(NO₃)(DPhPzTz)}₂(μ-NO₃)₂] (3) [PzTz?=?2-(1-pyrazolyl)-1,3-thiazine, DMPzTz?=?2-(3,5-dimethyl-1-pyrazolyl)-1,3-thiazine, DPhPzTz?=?2-(3,5-diphenyl-1-pyrazolyl)-1,3-thiazine] have been prepared and characterized by elemental analysis, electronic spectroscopy, IR spectroscopy, electron paramagnetic resonance spectroscopy, magnetic susceptibility measurements, and single-crystal X-ray diffraction. Influence of ligand size on coordination to Cu(II) has been analyzed. The three complexes are five-coordinate and the coordination geometry can be described as a distorted trigonal bipyramid for 1 or a distorted square pyramid for 2 and 3. As a consequence of the strain induced by the ligands, 1 is a monomeric complex cation whereas 2 is a polymer and 3 is a dimer.     

Stereochemical control of Zn(II)/Cu(II) selectivity in piperidine tripod ligands

Stereochemistry plays a major role in the selectivity toward zinc ion over copper(II) of some tripodal ligands with a central piperidine scaffold, one of which acts as a fluorescent zinc sensor with nanomolar sensitivity.     

Assembly of silver(I) coordination polymers incorporating pyromellitic acid and N-heterocyclic ligands

Five mixed ligands coordination polymers [Ag₄(apym)₂(pma)·(H₂O)₂]_n (1), {[Ag₄(dmapym)₄(pma)·(H₂O)₂]·(H₂O)₆}_n (2), [Ag₂(apyz)₂(H₂pma)·(H₂O)₄]_n (3), {[Ag₄(apyz)₂(pma)·(H₂O)₂]·(H₂O)₂}_n (4) and [Ag₄(NH₃)₈(pma)·(H₂O)₆]_n (5) (apym = 2-aminopyrimidine, dmapym = 4, 6-dimethyl-2-aminopyrimidine, apyz = 2-aminopyrazine, H₄pma = pyromellitic acid) were synthesized and characterized. For 1 and 2, as the substituents change from H to methyl, the dimensions of 1–2 decrease from three-dimension (3D) to one-dimension (1D) due to the steric effect of methyl groups. For 3 and 4, as the ratios of Ag₂O/apyz/pma vary from 1:1:1 to 2:1:1, the structure of 3 is a 1D ladder structure built from Ag-apyz double chains and pma anions, while the structure of 4 is a two-dimension (2D) grid. As excess ammonia is added to above four reaction systems, the structure of 5 contains unprecedented {[Ag(NH₃)₂]⁺}_n chains and pma anions. The substituent on the pyrimidyl ring, ratios of reactants, solvent systems and ligand isomers intensively influence the coordination environments of metal ion and the coordination modes of the carboxyl group, and thus determine the structures of the coordination polymers. The photoluminescent properties of 1–5 were also investigated.     

Coordination-position isomeric M(II)Cu(II) and Cu(II)M(II) (M = Co, Ni, Zn) complexes derived from macrocyclic compartmental ligands

The dinucleating macrocyclic ligands (L(2;2))(2-) and (L(2;3))(2-), comprised of two 2-[(N-methylamino)methyl]-6-(iminomethyl)-4-bromophenolate entities combined by the -(CH(2))(2)- chain between the two aminic nitrogen atoms and by the -(CH(2))(2)- or -(CH(2))(3)- chain between the two iminic nitrogen atoms, have afforded the following M(II)Cu(II) complexes: [CoCu(L(2;2))](ClO(4))(2).MeCN (1A), [NiCu(L(2;2))](ClO(4))(2) (2A), [ZnCu(L(2;2))](ClO(4))(2).0.5MeCN.EtOH (3A), [CoCu(L(2;3))(MeCN)(2-PrOH)](ClO(4))(2) (4A), [NiCu(L(2;3))](ClO(4))(2) (5A), and [ZnCu(L(2;3))](ClO(4))(2).1.5DMF (6A). [CoCu(L(2;2))(MeCN)(3)](ClO(4))(2) (1A') crystallizes in the monoclinic space group P2(1)/n, a = 11.691(2) A, b = 18.572(3) A, c = 17.058(3) A, beta= 91.18(2) degrees, V = 3703(1) A(3), and Z = 4. [NiCu(L(2;2))(DMF)(2)](ClO(4))(2) (2A') crystallizes in the triclinic space group P(-)1, a = 11.260(2) A, b = 16.359(6) A, c = 10.853(4) A, alpha= 96.98(3) degrees, beta= 91.18(2) degrees, gamma= 75.20(2) degrees, V = 1917(1) A(3), and Z = 2. 4A crystallizes in the monoclinic space group P2(1)/c, a = 15.064(8) A, b = 11.434(5) A, c = 21.352(5) A, beta= 95.83(2)degrees, V = 3659(2) A(3), and Z = 4. The X-ray crystallographic results demonstrate the M(II) to reside in the N(amine)(2)O(2) site and the Cu(II) in the N(imine)(2)O(2) site. The complexes 1-6 are regarded to be isomeric with [CuCo(L(2;2)))](ClO(4))(2).DMF (1B), [CuNi(L(2;2)))](ClO(4))(2).DMF.MeOH (2B), [CuZn(L(2;2)))](ClO(4))(2).H(2)O (3B)), [CuCo(L(2;3)))](ClO(4))(2).2H(2)O (4B), [CuNi(L(2;3)))](ClO(4))(2) (5B), and [CuZn(L(2;3)))](ClO(4))(2).H(2)O (6B) reported previously, when we ignore exogenous donating and solvating molecules. The isomeric M(II)Cu(II) and Cu(II)M(II) complexes are differentiated by X-ray structural, magnetic, visible spectroscopic, and electrochemical studies. The two isomeric forms are significantly stabilized by the "macrocyclic effect" of the ligands, but 1A is converted into 1B on an electrode, and 2A is converted into 2B at elevated temperature.     

Spectroscopic studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes with a N4-macrocylic ligands

Complexes of cobalt(II), nickel(II), copper(II) and zinc(II) with a new tetraaza macrocyclic ligand have been synthesized and characterized by microanalyses, molar conductance, magnetic susceptibility, mass, thermogravimetric (TGA), IR, 1H and 13C NMR, electronic and ESR spectral studies. All the complexes are found to have the formula [MLX2]x nH2O and are six-coordinated with distorted octahedral geometry.     

A comparison of the coordination preference of Cd, Zn, Cu(II) with flexible homophthalic acid and rigid bipyridine ligands

The mild hydrothermal reaction of Cd, Zn, or Cu(II) acetate salts with the deprotonated flexible linker homophthalic acid (H₂hmph) and the rigid molecule 4,4′-bipyridine (bpy) produced the following complexes, featured structurally by the assembly of various metal carboxylate subunits cohered further by the bpy ancillary ligand: {[Cd₂(hmph)₂(bpy)(H₂O)₂]·H₂O}_n (1) manifests cadmium carboxylate zigzag chain motifs, containing the alternation of a hmph-bridged Cd₂(hmph)₂ dimer and an edge-shared Cd₂N₄O₁₀ dimer, connected further by the bpy ligands to form a layered structure with a large 50-membered ring; [Zn(hmph)(bpy)]_n (2) processes hmph-bridged Cd₂(hmph)₂ dimer motifs inter-linked further by the bpy ligands to generate mutually embedded layered structures with square (4,4) grids; and {[Cu(hmph)(bpy)]·H₂O}_n (3) consists of copper carboxylate helix motifs, featuring hmph-bridged CuN₂O₄ octahedra cross-linked further by the bpy ligands into a twofold-interpenetrating 3D chiral framework with a homochiral topology of a quartz dual net. This well-defined synthetic system was proposed to highlight the fact that organic linkers display markedly different coordination preferences at specific metal ions. In addition, the fluorescence properties of complexes 1 and 2 were rationalized in terms of the local ligand environments in the crystal structures, and magnetic properties of complex 3 are also given.     

Synthesis,characterization, biological screening and molecular docking of Zn(II) and Cu(II) complexes of 3,5-dichlorosalicylaldehyde-N4-cyclohexylthiosemicarbazone

A 3,5-dichlorosalicylaldehyde-N⁴-cyclohexylthiosemicarbazone (C₁₄H₁₆Cl₂N₃OS) and its complexes [Zn(dsct)(phen)]·DMF ( 1 ), [Zn(dsct)(bipy)]·DMF ( 2 ), [Cu(dsct)(bipy)]·DMF ( 3 ) (phen = 1,10-phenathroline, bipy = 2,2’bipyridine) were synthesized and characterized by CHN analysis, FT-IR, UV–vis and NMR spectra. The molecular structure of the thiosemicarbazone (H₂dsct) and its complexes have been resolved using single crystal XRD studies. In the complexes, thiosemicarbazone exist in the thioiminolate form and acts as dideprotonated tridentate ligand coordinating through phenolic oxygen, thioiminolate sulfur and azomethine nitrogen. The antibacterial activity of the prepared compounds were screened against Escherichia coli, Salmonella typhi, Enterobacter aerogenes, Shigella dysentriae, Bacillus cereus, Staphylococcus aureus. All the complexes showed activity against bacterial strains E.coli and Salmonella typhi. The thiosemicarbazone showed activity against three bacterial strains such as E. coli, Enterobacter aerogenes and Shigella dysentriae. Complex 2 showed very good antibacterial activity as compared to standard drug (Ampicillin) against the bacterial strain, Salmonella typhi. Finally, the thiosemicarbazone and its complexes have been used to accomplish molecular docking studies against an Epidermal Growth Factor Receptor (EGFR) and breast cancer mutant 3hb5-oxidoreductase to determine the most preferred mode of interaction. The results confirm that the complex [Cu (dsct)(bipy)]·DMF( 3 ) showed the highest docking score as compared to other complexes under study. The [Cu(dsct)(bipy)]·DMF( 3 ) complex was evaluated for their anticancer activities against breast cancer cell line (MCF-7) and normal L929 (Mouse Fibroblast) cell line. It was found that the compound showed an LC₅₀ of 6.25 μg/mL against breast cancer cell line (MCF-7).     

Reactivity of pyridine-2,4,6-tricarboxylic acid toward Zn(II) salts under different reaction conditions

Pyridine-2,4,6-tricarboxylic acid (ptcH(3)) readily reacts with a Zn(II) salt at room temperature to form different products depending upon the presence or absence of pyridine in the reaction mixture. In the presence of pyridine, the ligand breaks to form infinitely zigzag coordination polymers with the empirical formula [Zn(Ox)(py)(2)]n(Ox = oxalate, py = pyridine). The backbone is formed from Zn(II)-oxalate where two pyridine molecules are coordinated to each Zn(II) ion giving it hexacoordination. The orientation of the bound pyridines is slightly different when Zn(II)-nitrate is used compared to that when Zn(II)-sulfate (or acetate) salt is used. In absence of pyridine, the ligand remains intact and forms a mixture of a carboxylate-bridged coordination polymer and a discrete carboxylate-bridged 12-membered metallomacrocycle.     

Assembly of 1-D and decanuclear cage compounds from copper halide,cyclohexenephosphonic acid,and 3-(2-pyridyl)pyrazole

The reactions of cyclohexenephosphonic acid (C₆H₉PO₃H₂) and 3-(2-pyridyl)pyrazole (2-pyPzH) with copper(II) chloride and copper(II) bromide affords a 1-D compound [Cu(2-pyPz)Cl] (1) and a decanuclear [Cu₁₀(OH)₄(C₆H₉PO₃)₆(2-pyPz)₄] (2) cage complex. In 1, adjacent copper ions are bridged by two 2-pyPz ligands into dimers, which are further linked by Cl^? into a ladder-like chain. Compound 2 has a decanuclear cage structure, the overall cage can be viewed as composed of two Cu₄(OH)₂(2-pyPz)₂ wings that are bridged by a central Cu₂P₂O₆ rim. Variable-temperature magnetic susceptibility studies indicate that both compounds show antiferromagnetic interactions between copper centers.     

Novel tetranuclear cubane-like Co(II) complexes involving chelate phosphoramide ligands

Interaction of cobalt(II) ions and sodium carbacylamidophosphates Na(L) (HL=PhC(O)NHP(O)(NR₂)₂; where NR₂ are morpholyl, HL¹; NMe₂, HL²; NEt₂, HL³) in methanol solution afforded polynuclear alkoxo complexes [Co₄{L¹}₃(OCH₃)₄(OH)(H₂O)₅·3H₂O] 1 and [Co₄{L}₄(OCH₃)₄(CH₃OH)₄] (L=L² 2, L³ 3). Data of spectral and TGA studies are presented. Coordination compounds 1 and 3 have been characterized by means of X-ray diffraction. Both the structures consist of tetranuclear cubane alkoxo clusters with methoxide ions bridging three metal centers (CoO 2.068(3)–2.093(4) Å) and phosphorylic ligands coordinated in a bidentatechelate fashion via the carbonyl oxygen atoms (CoO 1: 2.050(2); 3: 2.031(4) Å) and the phosphoryl groups (2.093(2) and 2.106(4) Å). Isolation of these cubane alkoxo complexes is an important proof for close resemblance in behavior of carbacylamidophosphate systems and β-diketonates towards transition metal ions.     

Synthetic, structural, electrochemical and solvent extraction studies of neutral trinuclear Co(II), Ni(II), Cu(II) and Zn(II) metallocycles and tetrahedral tetranuclear Fe(III) species incorporating 1,4-aryl-linked bis-beta-diketonato ligands

Uncharged complexes, formulated as trimeric metallocycles of type [M3(L(1))3(Py)6] (where M = cobalt(II), nickel(II) and zinc(II) and L(1) is the doubly deprotonated form of a 1,4-phenylene linked bis-beta-diketone ligand of type 1,4-bis(RC(O)CH2C(O))C6H4 (R = t-Bu)) have been synthesised, adding to related, previously reported complexes of these metals with L(1) (R = Ph) and copper(ii) with L(1) (R = Me, Et, Pr, t-Bu, Ph). New lipophilic ligand derivatives with R = hexyl, octyl or nonyl were also prepared for use in solvent extraction experiments. The X-ray structures of H2L(1) (R = t-Bu) and of its trinuclear (triangular) nickel(II) complex [Ni3(L(1))3(Py)6].3.5Py (R = t-Bu) are also presented. Electrochemical studies of H2L(1), [Co3(L(1))3(Py)6], [Ni3(L(1))3(Py)6], [Cu3(L(1))3], [Zn3(L(1))3(Py)6] and [Fe4(L(1))6] (all with R = t-Bu) show that oxidative processes for the complexes are predominantly irreversible, but several examples of quasireversible behaviour also occur and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as involving metal-centred oxidations. The reduction behaviour for the respective metal complexes is not simple, being irreversible in most cases. Solvent extraction studies (water/chloroform) involving the systematic variation of the metal, bis-beta-diketone and heterocyclic base concentrations have been performed for cobalt(II) and zinc(II) using a radiotracer technique in order to probe the stoichiometries of the respective extracted species. Significant extraction synergism was observed when 4-ethylpyridine was also present with the bis-beta-diketone ligand in the chloroform phase. Competitive extraction studies demonstrated a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).     

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: electrochemical, magnetic and antimicrobial studies

Phenoxide bridged later first row transition metal(II) complexes have been prepared by the interaction of later 3d transition metal(II) chlorides with tetranucleating compartmental Schiff base ligand system derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-hydrazinobenzothiazole. Ligand and complexes were characterized by analytical, spectral (IR, UV-visible, ESR, FAB-mass and fluorescence), magnetic and thermal studies. All complexes are found to have octahedral geometry. The mutual influence of metal centres in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff base and its complexes have been screened for their antibacterial (against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and antifungal activities (against Aspergillus niger, and Candida albicans).     

平面型四核铜簇合物Cu4(CH2XMen)4桥键性质的密度泛函研究

采用密度泛函B3LYP方法，用LanL2DZ和6—31G^＊基组分别优化了平面型四核铜簇合物Cu4（CH2SiMe3）4和Cu4（CH2XMe2）4（X=P，As）的几何构型，并对B3LYP／LanL2DZ方法优化的结构进行了红外振动频率计算和自然键轨道分析．结果表明，簇合物均呈笼状结构，Cu—C—Cu三中心桥键之间电子的离域增强了Cu簇合物的稳定性，配位C原子的C—H平伏键与C—Cu配位键之间存在σ-超共轭效应．