Synthesis,characterization, cytotoxicity and computational studies of new phosphine‐ and carbodithioate‐based palladium(II) complexes

In quest of new metallo‐pharmaceuticals with enhanced anticancer activity, four new phosphine‐ and carbodithioate‐based Pd(II) complexes of the type [(R)CS₂Pd(PR₃)Cl] (where R = 4‐(2‐hydroxyethyl)piperazine ( 1 , 2 ), dibenzyl ( 3 , 4 ); PR₃ = diphenyl(p ‐tolyl)phosphine ( 1 , 3 ), tris(4‐tolyl)phosphine ( 2 , 4 )) were synthesized and characterized using elemental analysis, Fourier transform infrared and NMR (¹H, ¹³C and ³¹P) spectroscopies and single‐crystal X‐ray diffraction. The X‐ray diffraction data confirmed the pseudo square‐planar geometry ensuring bidentate coordination mode of carbodithioate ligands. Anticancer activity of the synthesized complexes and their ligands was assessed against human lung (A549), breast (MCF‐7) and prostate (PC3) carcinoma cells using MTT assay. All the tested compounds showed activity in micromolar range. In many cases, the cytotoxicity of the synthesized complexes was higher than or comparable to that of the standard drugs cisplatin and doxorubicin. Complex 3 emerged as the most promising compound with the lowest IC₅₀ values of 4.83, 3.72 and 5.11 μM for A549, MCF‐7 and PC3 carcinoma cell lines, respectively. DNA binding studies were also carried out using UV–visible spectroscopy. We extended our investigations to explore the mechanism of anticancer activity using in silico tools. Based on the mechanism of action of standard drugs used, extensive docking studies were carried out on the three different biomolecular targets.     

Comparison of crystal structures and magnetic properties of two Co(II) complexes containing different dicarboxylic acid ligands

Two novel cobalt(II) complexes, [Co(μ-succinato)(H₂O)₂(pyridine)₂]_n1 and {[Co₂(μ-H₂O)(μ-glutarato)₂(pyridine)₂]·pyridine}_n2 have been synthesized by a wet chemistry method. In complex 1, the Co(II) ions are linked through succinate ligands to created one-dimensional polymeric chain along the b-axis. Complex 2 consists of a polymeric chain of dinuclear Co(II) moieties in which two cobalt(II) ions are linked through a bridging water and two bridging carboxylate groups from two glutarate ligands. The glutarate ligands in complex 2 display two coordination modes, interbinuclear bridging and intrabinuclear bridging. All the bond angles of the alkyl chain in complex 2 are between 115.7° and 118.5°, supporting the gauche conformation. Free pyridine molecules were found in the cavities between the chains. Two strong intramolecular hydrogen bonds are observed between the coordinated water and the uncoordinated carboxylate oxygen atom in both complexes. Complex 2 is further stabilized by π–π stacking of pyridine molecules. Complex 1 is a paramagnet (C = 3.50(1) cm³ K mol and θ = −5.0(5) K) and complex 2 exhibits a broad maximum at 4 K due to weak coupling within the dimeric unit.     

Synthesis,characterization, and cytotoxicity of Pt(IV) complexes containing 1,10-phenanthroline and 2,2′-bipyridine and diaminocyclohexane ligands

Four platinum(IV) complexes containing intercalating ligands [1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy)] and ancillary ligands [(1S,2S)-diaminocyclohexane (SS-DACH) and (1R,2R)-diaminocyclohexane (RR-DACH)] were synthesized and characterized by ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, X-ray crystal structure analysis, elemental analysis, ultraviolet absorption spectroscopy, circular dichroism spectroscopy, and electrochemical analysis. The reactions between [Pt(phen)(SS-DACH)Cl₂]²⁺ and glutathione and Ac-CPFC-NH₂ were investigated by high-performance liquid chromatography. [Pt(phen)(SS-DACH)Cl₂]²⁺ was reduced to its corresponding Pt(II) complex [Pt(phen)(SS-DACH)]²⁺, while glutathione and Ac-CPFC-NH₂ were oxidized to glutathione-disulfide and a peptide containing an intramolecular disulfide bond, respectively. The cytotoxicities of the Pt(IV) complexes against a human non-small cell lung cancer cell line (A549) and the corresponding cisplatin-resistant cell line (A549cisR) were evaluated. These Pt(IV) complexes showed a higher activity toward A549 and A549cisR than did cisplatin. Also, the cytotoxicities of the Pt(IV) complexes were higher for A549cisR than for A549 cells. Moreover, the cytotoxicities of the (SS-DACH)-liganded platinum complexes were higher than those of the (RR-DACH)-liganded platinum complexes in either A549 or A549cisR cells. Phen-liganded platinum complexes were more cytotoxic than the bpy-liganded platinum complexes. The cytotoxicities of these Pt(IV) complexes had no correlation with reduction potentials.     

Spectroscopic,biological activity studies,and DFT calculations,of Pd(II) and Pt(II) complexes of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione

Four palladium (II) and platinum(II) complexes with the formula [MCl₂(HPhqS)₂] and [M(PhqS)₂] (M^II = Pd and Pt), were synthesized by treating Na₂PdCl₄ or K₂PtCl₄ with 2 mol of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione (HPhqS) with or without the present base. The geometry around the Pd(II) and Pt(II) ions was a square planner and the HPhqS ligand was bonded as monodentate through the sulfur atom in complexes (1) and (2), while as bidentate chelating ligand through the nitrogen and sulfur atoms in complexes (3) and (4) as revealed by the data collection from spectroscopic studies. The prepared compounds were fully characterized by different physicochemical and spectroscopic methods. Furthermore, the free HPhqS ligand and its complexes were evaluated in vitro in regard to their antimicrobial activity against five bacteria species (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, staphylococcus epidermidis and staphylococcus aureus). Moreover, the cytotoxic activity of the compounds was examined against breast (MCF-7) and lung (A549) cancer cell lines, and the [PdCl₂(LH)₂] (1) and [PtCl₂(LH)₂] (2) appeared a highest inhibitory effect against MCF-7 cell lines with IC₅₀ = 4.291 ± 0.181 μM and 3.479 ± 0.162 μM, respectively, in comparison to the standard control and other complexes. The prepared ligand accompanied by the synthesized complexes were optimized using B3LYP method and 6–311++G(d,p) biases sets for the ligand and SDD basis set for the central metal. Different quantum parameters including electron affinity, ionization energy, dipole moment, hardness and vibrational frequencies were calculated for the ligand and its complexes. The total energy calculated for the two tautomeric structures of the ligand HPhqS showed a slightly higher value of the thione form over the thiol form. In addition, the trans-[PdCl₂(HPhqS)₂] complex possessed the highest dipole moment values while the cis-[PtCl₂(HPhqS)₂] showed non. In general, the obtained theoretical results showed a good match to the experimental findings.     

Cobalt(II) complexes with thiosemicarbazone as potential antitumor agents: synthesis,crystal structures,DNA interactions,and cytotoxicity

Two cobalt(II) complexes [Co(QCT)₂]·Cl·1.5H₂O (1) (QCT = quinoline-2-carboxaldehyde thiosemicarbazone) and [Co(QCMT)(CH₃OH)Cl₂] (2) (QCMT = quinoline-2-carboxaldehyde N⁴-methyl-thiosemicarbazone) have been synthesized and structurally characterized. Complex 1 crystallizes in a triclinic system with space group P–1 and complex 2 crystallizes in a monoclinic system with space group P2(1)/n. In both complexes the cobalt(II) center is six coordinated with distorted octahedral geometry. The interactions of two complexes with CT-DNA were investigated by electronic absorption spectra, circular dichroism (CD) spectra and fluorescence spectra. Results suggest that the complexes bind to DNA via groove binding mode, and complex 2 has stronger binding ability than complex 1. The in vitro cytotoxicity has been tested against the human lung adenocarcinoma cell line A-549, cisplatin-resistant cell line A-549/CDDP, and human breast adenocarcinoma cell line MCF-7. Complex 2 is more cytotoxic than complex 1, and both of them show higher cytotoxicity than the parent ligands alone. Compared with cisplatin, the two cobalt(II) complexes are more active against A-549/CDDP and MCF-7 cell lines at most experimental concentrations. Notably, although complex 2 is found to be less effective than cisplatin against the parent cell line A-549, it is much more effective than cisplatin against the resistant cell A-549/CDDP.     

Synthesis and structure of pseudotetrahedral Co(II) zwitterionic complexes: trichloro(1-methylpiperazin-1-ium-N4)cobalt(II) and trichloro(1,4-dimethylpiperazin-1-ium-N4)cobalt(II)

The pseudotetrahedral cobalt(II) zwitterionic complexes, [CoCl₃(H₂Meppz)] (1) [H₂Meppz⁺=1-methylpiperazin-1-ium cation] and [CoCl₃(HMe₂ppz)] (2), [HMe₂ppz⁺=1,4-dimethylpiperazin-1-ium cation] have been synthesized and characterized in the solid state by X-ray single crystal analysis, IR spectra, magnetic measurements and electronic spectra. In both the compounds the cobalt(II) center is coordinated in a distorted tetrahedral fashion by the three chloride ions and by one nitrogen of the piperazine ring that retains the more stable chair conformation. The distorted coordination polyhedron in complex 1 preserves the C_3v symmetry while in complex 2 it retains only the m symmetry. In complex 1, the (H₂Meppz)⁺ cation binds the Co(II) ion in the equatorial position of the piperazine ring using the unmethylated N1–H nitrogen atom that is less hindered than the methylated one. Complex 2, on the contrary, is a novelty being the first example of a Co(II) ion bound in the axial position of a piperazine ring, this produces a long Co(II)–N bond, 2.108(4) Å. Electronic spectra in the solid state are in perfect accordance with the X-ray crystallographic results indicating a C_3v symmetry for complex 1 and a C_s(m) symmetry for complex 2. These complexes present strong two-center and three-center hydrogen bonds of N⁺–H⋯Cl type.     

Palladium(II) and platinum(II) saccharinate complexes containing pyridine and 3-acetylpyridine: Synthesis, crystal structures, fluorescence and thermal properties

New palladium(II) and platinum(II) complexes of saccharinate (sac), trans-[Pd(py)₂(sac)₂] (1), cis-[Pt(py)₂(sac)₂] (2), trans-[Pd(3-acpy)₂(sac)₂] (3) and cis-[Pt(3-acpy)₂(sac)₂] (4) (py = pyridine and 3-acpy = 3-acetylpyridine) have been synthesized. Elemental analysis, UV-Vis, IR, NMR and TG/DTA characterizations have been carried out. The structures of 1-4 were determined by X-ray diffraction. The palladium(II) and platinum(II) ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of py or 3-acpy, forming a distorted square-planar geometry. The palladium(II) complexes (1 and 3) are trans isomers, while the platinum(II) complexes (2 and 4) are cis isomers. The mononuclear species in the solid state are connected by weak intermolecular C-H?O hydrogen bonds, C-H?π and π?π stacking interactions. The platinum(II) complexes show significant fluorescence at the room temperature.     

Synthesis,structures and properties of three copper complexes created via in situ ligand cross-coupling reactions

Three copper complexes {[Cu₂(L¹)₂]·I₃} _n (1), [Cu(L²)₂] (2), and [Cu₂I₂(L³)₂(MBI)₂] (3) (MBI = 2-mercaptobenzimidazole, L¹ = N-(benzothiazol-2-yl)acetamidine anion, L² = N-(thiazol-2-yl) acetamidine anion, L³ = 3-methyl-[1,2,4]thiadiazolo[4,5-a]benzimidazole) have been synthesized solvothermally by the reactions of CuI with 2-benzothiazolamine, 2-aminothiazole and 2-mercaptobenzimidazole (MBI), respectively, in acetonitrile. In situ C–N (or C–S) cross-coupling ligand reactions were observed in all three complexes, and hypothetical reaction mechanisms are proposed for the formation of the ligands and their complexes. The single-crystal X-ray structural analysis reveals that both the Cu(II) and Cu(I) atoms are located in pseudo-tetrahedral environments in complex 1, and L¹ acts as a double bidentate ligand which coordinates with the Cu(I) and Cu(II) atoms to form a 1D coordination polymer. Unlike complex 1, the Cu(II) atom in complex 2 is in a square planar geometry, coordinated by two L² ligands with relatively small steric hindrance. In complex 3, the Cu(I) atoms have a distorted tetrahedral geometry, being coordinated by one nitrogen atom from L³, two sulfur atoms of MBI ligands, and one iodide. The sulfur atoms from MBI ligands bridge two Cu(I) atoms to form a binuclear complex. All three complexes exhibit relatively high thermal stabilities. Complex 1 displays intense fluorescence emission at 382 nm and complex 3 displays two intense fluorescence emissions at 401 and 555 nm.     

Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

The redox reaction of bis(2-benzamidophenyl) disulfide (H₂L-LH₂) with [Pd(PPh₃)₄] in a 1:1 ratio gave mononuclear and dinuclear palladium(II) complexes with 2-benzamidobenzenethiolate (H₂L⁻), [Pd(H₂L-S)₂(PPh₃)₂] (1) and [Pd₂(H₂L-S)₂ (μ-H₂L-S)₂(PPh₃)₂] (2). A similar reaction with [Pt(PPh₃)₄] produced only the corresponding mononuclear platinum(II) complex, [Pt(H₂L-S)₂(PPh₃)₂] (3). Treatment of these complexes with KOH led to the formation of cyclometallated palladium(II) and platinum(II) complexes, [Pd(L-C,N,S)(PPh₃)]⁻ ([4]⁻) and [Pt(L-C,N,S) (PPh₃)]⁻ ([5]⁻). The molecular structures of 2, 3 and [4]⁻ were determined by X-ray crystallography.     

Synthesis,spectral, magnetic,electrochemical and kinetic studies of copper(II), nickel(II) and zinc(II) acetate complexes derived from phenol based ‘end-off’ ligands: Effect of p-substituents

A new class of symmetric, end-off, N-methyl piperazine armed binucleating ligands 2,6-bis(4-methyl piperazin-1-yl-methyl)-4-acetyl phenol (HL¹) and 2,6-bis[(4-methyl piperazin-1-yl-methyl)]-(4-methylcarboxy) phenol (HL²) were synthesized by the Mannich reaction. Their mononuclear and binuclear Cu(II), Ni(II) and Zn(II) complexes have been synthesized. These complexes were characterized by elemental analysis, infra-red and electronic spectral analysis. In the electronic spectra, the lower electron withdrawing nature of the C(O)CH₃p-substituent (HL¹) compared with the C(O)OCH₃p-substituent (HL²) of the phenolic ring causes a red shift in the LMCT-charge transfer band. The mononuclear Cu(II) complexes 1 and 7 have a magnetic moment value close to the spin only value with four hyperfine EPR signals. The binuclear Cu(II) complexes 4 and 10 illustrate an antiferromagnetic interaction (μ_eff 1.56 and 1.55 BM) at 298 K with a broad EPR signal. A variable temperature magnetic moment study of the binuclear copper(II) complexes shows that the extent of antiferromagnetic coupling increases in the order: CHO [K. Shanmuga Bharathi, A. Kalilur Rahiman, K. Rajesh, S. Sreedaran, P.G. Aravindan, D. Velmurugan, V. Narayanan, Polyhedron 25 (2006) 2859] < C(O)CH₃ < C(O)OCH₃ (−2J values 134 [Shanmuga Bharathi et al., mentioned above], 149 and 158 cm⁻¹, respectively). The mononuclear Ni(II) complexes 2 and 8 are square planar and diamagnetic. The six coordinated binuclear Ni(II) complexes 5 and 11 show a magnetic moment value of 2.96 and 2.95 BM, respectively. Electrochemical studies of the complexes reveal that all the mononuclear complexes show a single irreversible one-electron transfer reduction wave and the binuclear complexes show two irreversible one-electron transfer reduction waves in the cathodic region. There is an anodic shift in the reduction of the metal centres when the electron withdrawing nature of the p-substituent of the phenolic ring increases. The catecholase activity of the mono and binuclear copper(II) complexes, using pyrocatechol as a model substrate, and the hydrolysis of 4-nitrophenyl phosphate using the mono and binuclear copper(II), nickel(II) and zinc(II) complexes as catalysts showed that the binuclear complexes have higher rate constant values than those of the corresponding mononuclear complexes. A comparison of the spectral, electrochemical and magnetic behaviour of the complexes derived from the ligands is discussed on the basis of the substituent at the para position of the phenolic ring.     

Complexes Fe(HTrz)3B10H10 · H2O and Fe(NH2Trz)3B10H10 · H2O (HTrz = 1,2,4-triazole and NH2Trz = 4-amino-1,2,4-triazole). The spin transition 1 A 1 ⇆ 5 T 2 in Fe(HTrz)3B10H10 · H2O

Methods for the synthesis of iron(II) complexes with 1,2,4-triazole (HTrz) and 4-amino-1,2,4-triazole (NH₂Trz) containing the decahydro-closo-decaborate ion [B₁₀H₁₀]²-were developed. The empirical formulas of the complexes were Fe(HTrz)₃B₁₀H₁₀ · H₂O (I) and Fe(NH₂Trz)₃B₁₀H₁₀ · H₂O (II). The complexes were examined by static magnetic susceptibility measurements (2–300 K) and Moessbauer, IR, and electronic spectroscopy. Complex I exhibits the reversible spin transition ¹ A ₁ ? ⁵ T ₂ and pink ? white thermochromism. The temperatures of the forward and reverse transitions in complex I were 246 and 233 K, respectively. Complex II remained in the high-spin state over the whole temperature range. The sharp decrease in its effective magnetic moment at T < 78 K was attributed to antiferromagnetic exchange interactions between Fe²⁺ ions.     

Synthesis, crystal structures, electrochemical studies and anti-tumor activities of three polynuclear organotin(IV) carboxylates containing ferrocenyl moiety

A novel ferrocene-containing ligand 3-trifluoromethyl-5-ferrocenyl -pyrazol-1-yl-acetic acid (LCOOH) and three organotin(IV) carboxylate derivatives [Ph₄Sn₂O(OCH₃)(OOCL)]₂(1), [BuSnO(OOCL)]₆(2) and [Bu₄Sn₂O(OOCL₂)₂] (3) have been synthesized and structurally characterized by means of FT-IR, elemental analysis, ¹H NMR, ¹¹⁹Sn NMR, X-ray crystallography and cyclic voltammetry. Both complexes 1 and 3 are centrosymmetric with ladder framework. Complex 2 is a hexanuclear one with drum structure. Furthermore, their anti-tumor activities were also evaluated, using HepG2 human hepatocellular liver carcinoma cells, A549 human lung carcinoma cells and B16-F10 melanoma cells. Complex 1 displayed the best cytotoxicity and can be pointed out as a promising substrate to be subject of further investigations.     

Platinum(II) complexes of 8-quinolylmethylphosphonates: Synthesis,characterization and antitumour activity

A series of novel platinum(II) complexes of diethyl (8-dqmp) and monoethyl (8-Hmqmp) ester of 8-quinolylmethylphosphonic acid has been prepared and studied. It was shown that molecular or ionic complexes could be isolated by reaction of these organophosphorus ligands with [PtX₄]²⁻ (X = Cl, Br), depending on the acidity of the reaction solution. In the neutral medium diester formed dihalide adducts, trans-[Pt(8-dqmp)₂X₂] (1 and 2), with N-bonded ligand through the quinoline nitrogen. Under acidic conditions (pH < 3) both ligands gave the quinolinium salt complexes [LH]₂[PtX₄] (3 and 4, L = 8-dqmp; 7 and 8, L = 8-Hmqmp), with protonated quinoline ligand as cation and tetrahalidoplatinate complex as anion. By heating in methanol complexes 3 and 4 were converted into the corresponding dimeric hexahalidodiplatinum complexes, [8-Hdqmp]₂[Pt₂X₆] (5 and 6). The chelate complex [Pt(8-mqmp)₂] (9), with monoester ligand bonded through the quinoline nitrogen and the deprotonated phosphonic acid oxygen and forming two seven-membered {N, O} chelate rings, was obtained in neutral and basic media by reaction of platinum(II) halides either with sodium or hydrochloride salt of this monoester. The complexes were identified and characterized by elemental and thermogravimetric analyses, conductometric measurements, and by spectroscopic studies. In vitro antitumour activity of complexes was evaluated against the human epidermoid KB and murine leukaemia L1210 cell lines. These results were compared with those obtained for the palladium(II) complexes of the same phosphonate ligands and with those of platinum(II) and palladium(II) complexes of diethyl and monoethyl 2-quinolylmethylphosphonate, in order to correlate the structural and biological properties of quinoline-based aminophosphonate compounds.     

Syntheses,IR spectra,thermal properties and crystal structures of novel cyano-bridged polymeric complexes of zinc and cadmium with tetracyanoplatinate

Two novel one-dimensional polymeric cyano-bridged platinum(II) complexes of N-(2-hydroxyethyl)-ethylenediamine (hydeten), [M^II(hydeten)Pt(CN)₂(μ-CN)₂]_n (M^II = Zn^II (1) and Cd^II (2)), were synthesized and characterized by physico-chemical methods (elemental analysis, IR spectroscopy and thermoanalytical measurements) and X-ray diffraction. Thermal behaviours of 1 and 2 were followed using TG and DTA (DSC) techniques. The 1D chain structures of 1 and 2 were verified by X-ray diffraction studies. According to the positions of the bridging cyano groups, in complex 1 the polymeric chains are built up via the 2,2-CT type, while in complex 2 the polymeric chains are built up via the 2,2-TT type.     

In vitro anti‐proliferative and in silico docking studies of heteroleptic copper(II) complexes of pyridazine‐based ligands and ciprofloxacin

Three heteroleptic copper(II) complexes of the type [Cu(L^1–3)(cf)(ClO₄)] ( 1 – 3 ), where cf = ciprofloxacin, have been synthesized using pyridazine‐based ligands 3‐chloro‐6‐(salicylidenehydrazinyl)pyridazine (HL¹), 3‐chloro‐6‐(4‐diethylaminosalicylidenehydrazinyl)pyridazine (HL²) and 3‐chloro‐6‐(5‐bromosalicylidenehydrazinyl)pyridazine (HL³). Electronic spectral data and magnetic moment values suggest octahedral geometry for the synthesized copper(II) complexes. Electrochemical data of the copper(II) complexes present an irreversible one‐electron reduction wave in the cathodic potential region (E_pc) between ?0.631 and ?0.670 V. Frontier molecular orbital calculations were carried out, and the obtained low‐energy gap supports the bio‐efficacy of the complexes. All the complexes were screened for their in vitro cytotoxicity activity against three human cancerous (breast adenocarcinoma (MCF‐7), hepatoma (HepG‐2) and cervical (HeLa)) and one non‐cancerous (non‐tumorigenic human dermal fibroblast (NHDF)) cell lines using MTT assay, in which complex 2 exhibited higher activity. The apoptosis induction by the complexes was analysed using the Hoechst dye staining method with MCF‐7 cell line, which indicates higher apoptotic activity of complex 2 . A molecular docking study was carried out to ascertain the binding affinity of the synthesized heteroleptic copper(II) complexes with phosphoinositide 3‐kinase gamma (PI3Kγ) receptor.     

Solvent- and metal-directed lanthanide-organic frameworks based on pamoic acid: observation of slow magnetization relaxation,magnetocaloric effect and luminescent sensing

Two types of lanthanide coordination polymers, namely, [Ln(PA)(NO_3)(DMA)_3]_n(Ln=Gd(1), Dy(2), Eu(3), Tb(4))(type I), and {[Ln_2(PA)_3(DMF)_4]·2DMF}(Ln=Eu(5), Tb(6))(type II)(PA=Pamoic acid, DMA=dimethylacetamide,DMF=N,N-dimethylformamide), have been synthesized by the reaction of Ln(NO_3)_3·6H_2O with pamoic acid through layer diffusion method. These complexes were characterized by single crystal X-ray diffraction, infrared spectroscopy(IR),thermogravimetric analysis(TGA), fluorescence and magnetic measurements. Solvents and lanthanide atoms in the reaction play an important role in controlling different structures. Type I demonstrated 1-D linear chain structure connected by Ln atoms and PA ligands. Type II exhibited non-interpenetrating 3-D 6-connected 4_36~(12) nets based on binuclear [Ln_2(CO_2)_6(DMF)_4] cores.Magnetic properties of complexes 1–4 were investigated in details. Complex 1 shows significant magnetocaloric effect with–ΔS_m=20.37 J kg~(–1) K~(–1) at 3.0 K and 7 T. Complex 2 exhibits slow relaxation of the magnetization. Complexes 3–6 exhibit both ligand- and metal-centered fluorescent properties. Complex 6 demonstrates fluorescent sensing of DMF and Cu~(2+) ion.     

Synthesis, X-ray spectral, and magnetochemical study of copper complexes based on tridentate azomethines of 3-allylsalicylaldehyde

Tridentate azomethine ligands (H₂L) based on 3-allylsalicylaldehyde and o-aminophenol, o-aminothiophenol, or 2-ethylamino-5-nitroaniline were synthesized and identified by IR and ¹H NMR spectroscopies. The structure of complexes (Ia-Ic) was studied by magnetochemistry and EXAFS spectroscopy. Complexes Ia and Ib (X = O, S) are binuclear and exhibit antiferromagnetic exchange interaction: 2J = ?36.5 and ?950 cm^?1, respectively. Complex Ic (X = NC₂H₅) is mononuclear (μ_eff = 1.75 μ_B at 275 K and does not change as temperature decreases).     

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)₂(H₂O)(HTST)]·2H₂O (1), [Co₃(phen)₆(H₂O)₂(TST)₂]·7H₂O (2), and [Co₂Cu(phen)₆(H₂O)₂(TST)₂]·10H₂O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H₃TST) with the M²⁺ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen)₂ building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen)₂ building blocks; complex 3 is formed by replacing the trans-Co(II)(phen)₂ in 2 with a trans-Cu(II)(phen)₂, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen)₂ and Cu(II)(phen)₂ as building blocks. The study shows the flexible multifunctional self-assembly capability of the H₃TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.     

Synthesis, structures, luminescent and magnetic properties of four coordination polymers with the flexible 1,3-phenylenediacetate ligands

Four coordination polymers, [Zn(pda)(bpy)(H₂O)]_n·nH₂O (1), [Cd(pda)(prz)(H₂O)]_n (2), [Co₃(μ₃-OH)₂(pda)₂(pyz)]_n·2nH₂O (3) and [Pr₂(pda)₃(H₂O)₂]_n (4) (H₂pda=1,3-phenylendiacetic acid, bpy=4,4′-bipyridine, prz=piperazine and pyz=pyrazine) have been hydrothermally synthesized and characterized. Complex 1 is a 1D wheel-like chain structure, which is further extended into a 3D metal-organic supramolecular framework by H-bonds and π-π stacking interactions. Complex 2 is a 1D ladder-like chain structure, which is also further extended into a 3D metal-organic supramolecular framework by H-bonds. Complex 3 possess a 2D sheet structure with infrequent two pairs of double-helix chains. Complex 4 features a 3D structure. Both 1 and 2 display strong blue fluorescent emission at room temperature. Magnetic susceptibility measurements of complexes 3 and 4 exhibit antiferromagnetic interactions between the nearest metal ions, with C=9.99 and 3.43 cm³ mol⁻¹ K, and θ=−23.9 and −46.3 K, respectively.     

Synthesis, molecular structure and catalytic activity of chiral benzamidinate nickel complexes

Two new nickel complexes containing the chiral benzamidinate ligation: [PhC(N-SiMe₃)(N′-myrtanyl)]₂Ni(py)₂(3) and {[PhC(NH)(N′-myrtanyl)]₂Ni}₂ (6) have been synthesized and characterized. The solid-state molecular structures of these complexes have been determined by low-temperature X-ray diffraction analysis. Complex 3 was obtained via two different procedures. In complex 3, the metal adopts a nearly ideal octahedral environment, whereas in complex 6 the two divalent nickel metals are coordinated in a square-planar geometry, forming a dimer. Complex 3 activated with MAO has been found to oligomerize propylene producing a mixture of dimers, trimers and tetramers with a turnover frequency of 5200 h⁻¹, whereas complex 6 being activated with MAO oligomerizes ethylene to a mixture of dimers and trimers with a high turnover frequency of 15,400 h⁻¹. In addition, when activated with MAO both complexes showed a good activity for the vinyl-type polymerization of norbornene.