Synthesis,characterization and antibacterial activity of palladium(II) bromide complexes of thioamides; X-ray structure of [Pd(tetramethylthiourea)<Subscript>4</Subscript>]Br<Subscript>2</Subscript>

Palladium(II) bromide complexes of thioamides having the general formulae [PdL₂Br₂] and [PdL₄]Br₂ where L = Thiourea (Tu), Methylthiourea (Metu), Dimethylthiourea (Dmtu), Tetramethylthiourea (Tmtu), Imidazolidine-2-thione (Imt), Mercaptopyridine (Mpy), Mercaptopyrimidine (Mpm) and Thionicotinamide (Tna) were prepared by reacting K₂[PdCl₄] with KBr and the corresponding thioamides. The complexes were characterized by elemental analysis, IR and NMR spectroscopy, and one of them, [Pd(Tmtu)₄]Br₂ (1) by X-ray crystallography. The crystal structure of 1 shows a square-planar coordination environment around the Pd(II) atoms with the average cis and trans S–Pd–S bond angles of 90.0° and 180.0°, respectively. The synthesized complexes were screened for antibacterial effects, and the results showed that the complexes exhibit significant activities against both gram positive and gram negative bacteria.     

Syntheses,characterization and anti‐microbial activities of palladium(II) and palladium(IV) complexes of 3,10‐C‐meso‐Me8[14]diene (L1) and its reduced isomeric anes (LA,LB and LC). Crystal and molecular structure of [PdL1][Pd(SCN)4]

The reactions of 3,10‐C‐meso‐3,5,7,7,10,12,14,14‐octamethyl‐1,4,8,11‐tetraazacyclotetradecadiene, L¹, and two isomers (L_B and L_C, differing in the orientation of methyl groups on the chiral carbon atoms) of its reduced form with PdCl₂ and K₂[Pd(SCN)₄], produce square‐planar tetrachloro‐ and tetrathiocyano‐palladium(II) complexes of general formulae [PdL′][PdCl₄] and [PdL′][Pd(SCN)₄] (L′ = L¹, L_B and L_C), respectively. By contrast, the third ane isomer, L_A, upon reaction with the same reagents, PdCl₂ and K₂[Pd(SCN)₄], formed octahedral tetrachloro‐ and tetrathiocyanato‐palladium(IV) complexes [PdL_ACl₂]Cl₂ and [PdL_A(SCN)₂](SCN)₂, respectively. The [PdL′][PdCl₄] and [PdL_ACl₂]Cl₂ complexes undergo substitution reactions with KSCN to form square‐planar and octahedral tetrathiocyanato complexes [PdL′][Pd(SCN)₄] and [PdL_A(SCN)₂](SCN)₂, respectively. All complexes have been characterized on the basis of analytical, spectroscopic, conductometric and magnetochemical data. The anti‐fungal and anti‐bacterial activities of these complexes have been studied against some phytopathogenic fungi and bacteria. The crystal structure of [PdL¹][Pd(SCN)₄] has been confirmed by X‐ray crystallography and shows with square‐planar PdN₄ and PdS₄ geometries [monoclinic, space group C2/c, a = 17.884(3) Å, b = 14.734(2) Å, c = 11.4313(18) Å, β = 104.054(5)° ]. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermal, spectral, electrochemical and biologic characterization of new Pd(II) complexes with ligands bearing biguanide moieties

New complexes [Pd(HDMBG)₂]Cl₂·H₂O, [PdL¹]Cl₂·0.5H₂O and [PdL²]Cl₂·1.5H₂O (HDMBG: dimethylbiguanide, L¹ and L²: ligands resulted from HDMBG, ammonia/hydrazine and formaldehyde template condensation) were synthesized and characterized. The features of complexes have been assigned from microanalytical, IR, UV–Vis and cyclic voltammetry data. The thermal transformations are complex processes according to TG and DTA curves including water and hydrochloric acid elimination, thermolysis processes leading to paracyanide formation as well as PdO decomposition, final product being palladium. Complexes were screened for their antimicrobial properties against some pathogenic Gram-positive and Gram-negative bacterial as well as fungal Candida albicans strains. The complexes exhibit specific antibacterial and/or antifungal activity, depending on their structure and the tested microbial strains. All complexes inhibit the microbial biofilm development on the inert substratum. It was also observed that PdCl₂ complexation minimized their cytotoxic effect on the eukaryotic cells.     

Complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole

Novel oligonuclear complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole (L) of the composition [M₃L₁₀(H₂O)₂](NO₃)₆ (M = Co(II), Ni(II)), [Ni₃L₆(H₂O)₆]Hal₆ (Hal = Cl^?, Br^?), and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O were synthesized and studied by magnetic susceptibility, electronic and IR spectroscopy, and powder X-ray diffraction methods. All the above complexes are X-ray amorphous. Antifer-romagnetic exchange interactions between the M²⁺ ions were discovered in the [Co₃L₁₀(H₂O)₂](NO₃)₆ and [Ni₃L₁₀(H₂O)₂](NO₃)₆ complexes, whereas ferromagnetic exchange interactions were observed in the complexes [Ni₃L₆(H₂O)₆]Cl₆, [Ni₃L₆(H₂O)₆]Br₆, and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O.     

Synthesis and Photochemical Properties of Pd(II) Complexes of Secondary Heterocyclic Amines

Ionic [Pd(LH)₂(ClO₄)₂], neutral (PdL₂) complexes of Pd(II) with hetarylamines derived fromdipyridylamine and benz[c,d]indolylamine were synthesized. The ¹H NMR, IR, and UV spectra of the products were studied. Irradiation of neutral Pd(II) complexes with N-derivatives of benz[c,d]indolylamine results in ligand elimination. Photolysis of a neutral Pd(II) complex with 3,5-dichloro-2,2'-dipyridylamine in solution results in ligand cyclization to give 8-chlorodipyrido[1,2-a:2',3'-d]imidazole.     

Synthesis and spectroscopic investigations of Rh(III) and Pd(II) complex compounds with N-(pyridine-2-yl)morpholine-4-carbothioamide

The present paper describes the synthesis and spectral properties of Rh(III) and Pd(II) coordination compounds with N-(pyridine-2-yl)morpholine-4-carbothioamide (PMCTA). The compounds have the general composition [RhL₂Cl₂]Cl · C₂H₅OH (1), [PdL₂]Cl₂ (2), [PdL₂](ClO₄)₂ · 2C₃H₆O (2a), [PdLCl₂] · 2H₂O (3). All complexes were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, XPS and UV–Vis spectra. It has been shown that PMCTA behaves as a bidentate (N,S)-ligand, forming six membered metallocycles and coordinating to the metal ion through the carbothioamide sulfur atom and the pyridine nitrogen atom. The UV–Vis spectra suggest that the Pd(II) complexes are square planar, while the Rh(III) complex has an octahedral geometry. The molecular structure of the Pd(II) complex with PMCTA (M:L = 1:2) was determined by single-crystal X-ray diffraction.     

Salen-type nickel(II), palladium(II) and copper(II) complexes having chiral and racemic camphoric diamine components

Chiral and racemic Salen-type Schiff-base ligands (H₂L¹, H₂L² and H₂L³), condensed between D-(+)- and D,L-camphoric diamine (also known as (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diamine) and 2-hydroxybenzaldehyde or 3,5-dibromo-2-hydroxybenzaldehyde with a 1:2 molar ratio, have been synthesized and characterized. A series of new nickel(II), palladium(II) and copper(II) complexes of these chiral and racemic ligands exhibiting different coordination number (4, 5 and 6) have been characterized with the formulae [NiL¹]·CH₃OH (3), [NiL¹]·H₂O (4), [NiL²] (5), [PdL²] (6), [Cu₂(L²)₂(H₂O)] (7) and [NiL³(DMF)(H₂O)] (8). Different solvent molecules in 3 and 4 (methanol and water molecules) as well as different apical ligands in 7 and 8 (water and DMF molecules) are involved in different O–H···O hydrogen bonding interactions to further stabilize the structures. UV–Vis (UV–Vis), circular dichroism (CD) spectra and thermogravimetric (TG) analyses for the metal complexes have also been carried out.     

Unveiling the binding interaction of zinc (II) complexes of homologous Schiff-base ligands on the surface of BSA protein: A combined experimental and theoretical approach

Four new zinc (II) complexes [Zn (HL¹H)Br₂] (1), [Zn (HL¹H)Cl₂] (2), [Zn₂(HL²)Br₃] (3), and [Zn (HL²)Cl] (4) have been synthesized by adopting template synthetic strategy and utilizing two homologous Schiff base ligands (H₂L¹ = 4-bromo-2-{[2-(2-hydroxyethylamino)-ethylimino]-methyl}-6-methoxyphenol, H₂L² = 4-bromo-2-{[3-(2-hydroxyethylamino)propylimino]methyl}-6-methoxyphenol), differing in one -CH₂- unit in the ligating backbone, by adopting template synthetic strategy. All the complexes have been characterized by single crystal X-ray diffraction analysis as well as by other routine physicochemical techniques. Ligand mediated structural variations have been observed and rationalized by density functional theoretical (DFT) calculations. Interaction of the complexes 1–4 with Bovine Serum Albumin protein (BSA) has been studied by different spectroscopic techniques. A complete thermodynamic profile (ΔH^o, ΔS^o and ΔG^o) was evaluated initially from the change in absorption and fluorescence spectra upon addition of BSA to the complexes. Appreciable binding constant values in the range ~ 0.94–4.51 × 10⁴ M⁻¹ indicate efficient binding tendency of the complexes to BSA with the sequence 1 ≅ 2 > 3 ≅ 4. Circular dichroism (CD), isothermal calorimetric titration experiments, molecular docking and molecular dynamics have been performed to gain deep insight into the binding regions of complex 1 to BSA. Experimental evidences suggest an interaction of zinc complexes at the surface of BSA protein and this particular binding has been exploited to determine unknown concentration of BSA protein. For this purpose complex 1 was explored as a BSA protein quantification tool.     

Cobalt(II), nickel(II), and copper(II) complexes of 14-membered hexaazamacrocycles: synthesis and characterization

Cobalt(II), nickel(II), and copper(II) complexes containing 5,12-di(4-bromophenyl)-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L¹) and 5,12-diphenyl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L²) have been synthesized. All complexes were characterized by elemental analysis, MALDI TOF-MS spectrometry, and electronic absorption spectroscopy. The crystal structures of two compounds, [Cu₂(H₂L¹)Cl₄]_n and [NiL²], were determined by X-ray powder diffraction. In the polymeric [Cu₂(H₂L¹)Cl₄]_n, the Cu₂Cl₄ units and H₂L¹ molecules are situated on inversion centers. Each Cu(II) has a distorted trigonal-bipyramidal coordination environment formed by N and O from H₂L¹ [Cu–N 2.340(14)?Å, Cu–O 1.952(11)?Å], two bridging chlorides [Cu–Cl 2.332(5), 2.279(5)?Å] and one terminal chloride [Cu–Cl 2.320(6)?Å]. In the [NiL²] complex, the Ni(II) situated on inversion center has a distorted square-planar coordination environment formed by four nitrogens from L² [Ni–N 1.860(11), 1.900(11)?Å].     

Synthesis,characterization, and anticancer activity of some azole‐heterocyclic complexes with gold(III), palladium(II), nickel(II), and copper(II) metal ions

Four new complexes of Au(III), Pd(II), Ni(II), and Cu(II) ions were synthesized, derived from a novel heterocyclic ligand (L) that has both triazole and tetrazole rings. The ligand synthesis was through successive steps to achieve both heterocyclic rings. The synthesized compounds were characterized using conventional techniques like infrared, ultra violet—visible and proton/carbon nuclear magnetic resonance spectroscopy, metal and thermal analyses, and molar conductivity. All complexes were suggested to have square planar geometry, gold, nickel, and palladium complexes were salts while copper neutral complexes have the chemical formulas; [AuL₂]Cl.2H₂O, [PdL₂]Cl₂.2H₂O, [NiL₂]Cl₂.2H₂O, and [CuL₂]. The cytotoxic effect was studied on breast cancer cell line (MCF‐7 cell line) at different concentrations by using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay method, for the ligand (L) and complexes. The results showed that gold(III) and nickel(II) complexes have the highest cytotoxicity among all compounds against cancer cell lines.     

Complexes of Cu(I) and Pd(II) with (+)-camphor and (–)-cavrone thiosemicarbazones: Synthesis,structure, and cytotoxicity of the Pd(II) complex

CuLCl, CuL¹Cl, PdLCl₂, and PdL¹Cl₂ complexes [L and L¹ being (+)-camphor and (–)-carvone thiosemicarbazones, respectively] have been synthesized. The structure of binuclear [Pd₂L²²Cl₄] complex has been determined by means of X-ray diffraction. The L² ligand (dehydrogenated (–)-carvone thiosemicarbazone) is coordinated via the bridging S atom to two Pd atoms. The complexes of Cu(I) and Pd(II) presumably have polynuclear and binuclear structure, respectively. These facts are in good agreement with IR and NMR spectroscopy as well as mass spectrometry data which indicate the coordination of L and L¹ ligands via the S atom. The influence of L¹ and PdL¹Cl₂ on viability of the Hep2 cell line has been studied. The PdL¹Cl₂ complex is more cytotoxic than L¹ ligand.     

Synthesis,characterization, and antimicrobial studies of some palladium complexes with an octamethyl tetraazacyclotetradecadiene ligand and isomers of its reduced form

Biologically important tetraaza-macrocyclic ligand 3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene dihydroperchlorate, Me₈[14]diene·2HClO₄ (L₁·2HClO₄) was synthesized by the condensation of 1,2-diaminopropane with acetone in presence of quantitative amount of HClO₄ and three isomeric ligands designated as L_A, L_B and L_C were separated by the reduction of L₁·2HClO₄ with NaBH₄ and fractional crystallization from xylene. The nitrato, nitro, bromido, and iodido complexes of palladium with diene ligand L₁ were prepared by the interaction of L₁·2HClO₄ with K₂[Pd(NO₃)₄], K₂[Pd(NO₂)₄], K₂[PdBr₄], and K₂[PdI₄] (prepared by the reactions with PdCl₂ with KNO₃, KNO₂, KBr, and KI, respectively), respectively. The bromide and iodido complexes of L_A were prepared by the axial substitution reactions with [PdL_ACl₂]Cl₂. By contrast, similar complexes of other isomeric ligands L_B and L_C were prepared by axial addition reactions of [PdL^?][PdCl₄] (L′?=?L_B or L_C) with KBr and KI, respectively. The complexes were characterized on the basis of elemental analysis: IR, ¹H-NMR, UV–Vis spectroscopic analysis, and magnetic and molar conductivity data. The antifungal and antibacterial activities of these compounds have been studied against some phyto-pathogenic fungi and bacteria.     

Synthesis,characterization, thermal,and antimicrobial studies of binuclear metal complexes of sulfa-guanidine Schiff bases

A series of metal complexes of Schiff bases derived from condensation of sulfa-guanidine with 1-benzoylacetone (H₂L¹), 2-hydroxybenzophenol (H₂L²), dibenzoylmethane (H₂L³), 5-methylisatine (H₂L⁴), and 1-methylisatine (H₂L⁵) have been synthesized. The complexes are characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, UV–Vis, ¹H NMR, and ESR spectra, as well as thermogravimetric analysis. The low molar conductance values indicate the complexes are nonelectrolytes. IR and ¹H NMR spectra show that H₂L¹–H₂L⁵ are coordinated to metal ions by two bidentate centers. Mn(II), Co(II), Ni(II), and Cu(II) complexes display paramagnetic behavior, whereas the Zn(II)-complex was diamagnetic. All studies confirm the formation of an octahedral geometry for [Cu₂L¹(AcO)₂(H₂O)₆] · 3H₂O (1), [Mn₂L⁴(AcO)₂(H₂O)₆] · 2H₂O (6), [Ni₂L⁴(AcO)₂(H₂O)₆] · 2H₂O (8), a tetrahedral geometry for [Cu₂L²(AcO)₂(H₂O)₂] (2), [Cu₂(L⁴)₂] (4), [Co₂(L⁴)₂] · 2H₂O (7) and [ZnHL⁴(AcO)(H₂O)] · 2H₂O (9) and a trigonal bipyramid geometry for [Cu₂L³(AcO)₂(H₂O)₄] (3) and [Cu₂HL⁵(AcO)₃(H₂O)₃] · H₂O (5). H₂L⁴ was most effective on Gram negative, Gram positive bacteria, and fungi (diameters inhibition zone ranged between 10.5–27.5 mm) after 24 and 48 h, respectively. Complex 8 showed moderate antimicrobial activity. Its minimum inhibitory concentration (MIC) against Escherichia coli, Bacillus subtilis, Candida albicans and Aspargllus flavas was 20 mg L^–1. The compound proved to be of moderate toxicity and its LD₅₀ was 20 mg L^–1.     

Synthesis, crystal structures, and magnetic properties of tetranuclear nickel(II) and copper(II) complexes with tridentate Schiff bases

Two cubane-type tetranuclear nickel(II) and copper(II) complexes, [Ni₄(L¹)₄(CH₃OH)₄] (1) and [Cu₄(L²)₄]·H₂O (2), where L¹ and L² are the dianionic forms of the tridentate Schiff bases 4-nitro-2-[(2-hydroxyethylimino)methyl]phenol (H₂L¹) and 5-methoxy-2-[(2-hydroxyethylimino)methyl]phenol (H₂L²), respectively, have been synthesized and characterized by physicochemical methods and single-crystal X-ray diffraction. The magnetic properties of the complexes show the presence of ferromagnetic interactions for complex 1 and antiferromagnetic interactions for complex 2, mediated by hydroxyl bridges.     

Binary and ternary oxorhenium(V) complexes: synthesis,characterization, and crystal structure

A series of anionic five-coordinate binary oxorhenium(V) complexes with dithiolato ligands, Bu₄N[ReO(L¹)₂] (1a), Bu₄N[ReO(L²)₂] (1b), and Bu₄N[ReO(L³)₂] (1c), and a series of neutral octahedral ternary oxorhenium(V) complexes of mixed dithiolato and bipyridine ligands, [ReO(L¹)(bpy)Cl] (2a), [ReO(L²)(bpy)Cl] (2b), and [ReO(L³)(bpy)Cl] (2c) (where L¹H₂ = ethane-1,2-dithiol, L²H₂ = propane-1,3-dithiol, L³H₂ = toluene-3,4-dithiol, and bpy = 2,2′-bipyridine), were isolated and characterized by physicochemical and spectroscopic methods. The solid state structure of 1c was established by X-ray crystallography. All the mononuclear oxorhenium(V) complexes are diamagnetic. The redox behavior of all the complexes has been studied voltammetrically.     

Copper and palladium complexes with substituted pyrimidine-2-thiones and 2-thiouracils: syntheses,spectral characterization,and X-ray crystallographic study

Copper(I) and palladium(II) complexes containing 5-acetyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione (L¹), ethyl 4,6-dimethyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (L²), cis-5-acetyl-6-ethyl-5,6-dihydro-2-thiouracil (L³), and 5,6-dihydro-2-thiouracil (L⁴) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H, and ¹³C NMR spectroscopy. To assign bands in the IR spectra of L¹ and L² and complexes with Cu(I) and Pd(II), deuterium substitution of movable protons at N-atoms was used. The crystal structures of two compounds, [Cu(L²)₂Cl] and [Pd(L⁴)₂Cl₂], were determined by X-ray single-crystal and powder diffraction, respectively. In [Cu(L²)₂Cl], copper has a rare coordination number of three and triangular surrounding of two neutral L² molecules, coordinated through sulfurs, and chloride. In [Pd(L⁴)₂Cl₂], palladium has a standard square-planar geometry, formed by two uracil molecules and two chlorides. A new method for the synthesis of 5,6-dihydro-2-thiouracil, starting from β-aminopropionic acid, was suggested.     

Copper(II) and Cadmium(II) Complexes Based on N,N‐Bis(3, 5‐dimethyl‐2‐hydroxybenzyl)‐N‐(2‐pyridylmethyl)amine Ligand: Syntheses,Structures, Magnetic,and Luminescent Properties

The reaction of the aryl‐oxide ligand H₂L [H₂L = N,N‐bis(3, 5‐dimethyl‐2‐hydroxybenzyl)‐N‐(2‐pyridylmethyl)amine] with CuSO₄ · 5H₂O, CuCl₂ · 2H₂O, CuBr₂, CdCl₂ · 2.5H₂O, and Cd(OAc)₂ · 2H₂O, respectively, under hydrothermal conditions gave the complexes [Cu(H₂L¹)₂] · SO₄ · 3CH₃OH ( 1 ), [Cu₂(H₂L²)₂Cl₄] ( 2 ), [Cu₂(H₂L²)₂Br₄] ( 3 ), [Cd₂(HL)₂Cl₂] ( 4 ), and [Cd₂(L)₂(CH₃COOH)₂] · H₂L ( 5 ), where H₂L¹ [H₂L¹ = 2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenol] and H₂L² [H₂L² = 2‐(2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenoxy)‐4, 6‐dimethylphenol] were derived from the solvothermal in situ metal/ligand reactions. These complexes were characterized by IR spectroscopy, elementary analysis, and X‐ray diffraction. A low‐temperature magnetic susceptibility measurement for the solid sample of 2 revealed antiferromagnetic interactions between two central copper(II) atoms. The emission property studies for complexes 4 and 5 indicated strong luminescence emission.     

Coordination compounds of some d metals with anthrapyridinedione derivatives: Crystal structure of 2-phenyl-4-(piperidyl-1)-anthra[1,2-b]pyridine-7,12-dionium hexabromodicuprate(II) (HL1)2[Cu2Br6]

Complexes of copper(II), nickel(II), and cobalt(II) chlorides and bromides with 2-phenyl-4-(piperidyl-1)-anthra[1,2-b]pyridine-7,12-dione (L¹) and 2-[phenyl-4-(octylamino)-anthra[1,2-b]pyridine-7,12-dione (L²) were synthesized from neutral and acidic media. The molecular and crystal structure of 2-phenyl-4-(piperidyl-1)-anthra[1,2-b]pyridine-7,12-dionium hexabromodicuprate(II) (HL¹)₂[Cu₂Br₆] was determined by X-ray diffraction analysis. The spectral characteristics of L¹ and L² and their complexes are presented. Formation of their complexes in solutions was studied.     

Synthesis of palladium(II) complexes with 3-amino-5-methyl-5-(4-pyridyl)-hydantoin: cytotoxic and antimicrobial investigations and comparison with their platinum analogues

Two new Pd(II) complexes with 3-amino-5-methyl-5-(4-pyridyl)-hydantoin (AMPH) were synthesized: cis-[Pd(AMPH)₂Cl₂]·2H₂O and cis-[Pd(AMPH)₂Br₂]·H₂O. The complexes were characterized by physico-chemical and spectroscopic methods. The determination of crystal water content in the complexes was defined by Karl Fisher titration. The cytotoxic effects of these complexes were examined on a panel of human tumor cell lines. Qualitative antimicrobial assays on three pathogenic microorganisms of the new complexes, their analogues with 5-methyl-5-(4-pyridyl)-hydantoin(MPH) and their platinum analogues were made. Cis-[Pd(mpyh)₂Br₂]·H₂O showed significant activity against C. albicans.     

Syntheses and structures of tetranuclear Zn（Ⅱ） complexes with in situ generated macrocyclic Schiff base ligands:Applications in Zn2+ sensing

Three novel Zn（II） complexes,[Zn₄L¹Cl₄]-3H₂O（1）,[Zn₄L²Cl₄]-2DMF（2） and[Zn₄L³Cl₄]H₂O（3）,have been synthesized and structurally characterized.In these complexes,interesting 32-membered dodecadentate macrocyclic ligands were generated in situ by ’2 + 2’ type condensation reactions between a tetraamine and various dialdehydes.All the complexes are isostructurally tetranuclear Zn（Ⅱ） complexes,containing endogenous alkoxo and phenoxo bridges.Applications of the macrocyclic ligands as Zn²⁺ sensors have been investigated.Take H₄L¹ for example,it exhibits a 4-fold fluorescence enhancement upon the addition of 2 equiv.of Zn²⁺ in MeOH.