Different crystal structures and luminescent properties of zinc and cadmium coordination polymers constructed from two flexible thioether ligands with different alkyl chains

Treatments of nitrogen-containing heterocyclic dithioether ligands, 1,2-bis(4-(pyridin-3-yl) pyrimidin-2-ylthio) ethane (L¹) and 1,3-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) propane (L²), with zinc or cadmium salts have resulted in the interesting frameworks with structural motifs from a mononuclear macrocycle or a dinuclear macrocycle to an one-dimensional structure. A small difference of the alkyl length between L¹ and L² led to conspicuous changes of the fluorescent properties of both ligands and their complexes. Mainly due to the size of metal atoms, structures of [ZnL²I₂] (1) and [CdL²I₂] (2) are varied from a mononuclear macrocycle to a 1D framework, while {[ZnL²(H₂O)₄](ClO₄)₂}₂ (3) and {[CdL²(H₂O)₄](ClO₄)₂}₂ (4) are dinuclear macrocycles in which perchlorate anions may play an important template role. As for complexes 5–8 ([ZnL¹I₂]_n (5), [CdL¹I₂]_n (6), {{[ZnL¹₂(H₂O)₄](ClO₄)₂}_0.5 · L¹_0.5 · CH₃OH} (7), {{[Cd_0.5L¹(H₂O)₂](ClO₄)}₂ · CH₃OH · L¹} (8)), the self-assemble processes were mainly directed by the organic ligand in the reactions of L¹ with metal salts. Complexes 1–4 exhibit blue fluorescence emissions, among which 1 and 2 may be suitable as candidates for blue fluorescent materials.     

Metal Complexes with a New Tetrapyridyl Pendant Armed Macrocyclic Ligand. X‐ray Crystal Structures of CuII and NiII Complexes

A new pendant‐armed macrocyclic ligand, L¹, bearing four pyridyl pendant groups has been synthesized by N‐alkylation of the tetraazamacrocyclic precursor L with 2‐picolyl chloride hydrochloride. Metal complexes of L¹ have been synthesized and characterized by microanalysis, MS‐FAB, conductivity measurements, IR, UV‐Vis, ¹H and ¹³C NMR spectroscopy and magnetic studies. Crystal structures of the ligand L¹ as well as of the complexes [Ni₂L¹](ClO₄)₄·5CH₃CN and [Cu₂L¹](ClO₄)₄·4.5CH₃CN have been determined by single crystal X‐ray crystallography. The X ray studies show the presence of two metal atoms within the macrocyclic ligand in both metal complexes showing five coordination arrangement for the metal ions.     

Comparative structural study of the complexation behaviour of silver(I), cadmium(II), mercury(II), and palladium(II) with a 17-membered N3O2-donor macrocycle

A comparative investigation of the coordination behaviour of the 17-membered, N₃O₂-donor macrocycle, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane, L, with the soft metal ions Ag(I), Cd(II), Hg(II), and Pd(II) is reported. The X-ray structures of 12 complexes have been determined and a range of structural types, including both mononuclear and dinuclear species, shown to occur. In particular cases the effect of anion variation on the resulting structures has been investigated; L reacts with AgX (X = NO₃, ClO₄, PF₆, OTf and CN) to yield related 2:2 (metal:ligand) complexes of types [Ag₂L₂(NO₃)₂] (1), [Ag₂L₂](ClO₄)₂ · 2DMF (2), [Ag₂L₂](PF₆)₂ · 2DMF (3), [Ag₂L₂](OTf)₂ (4) and [Ag₂L₂(μ-CN)][Ag(CN)₂] · H₂O (5). In all five complexes the ether oxygens of each ring are unbound. In 1–4 the macrocycles are present in sandwich-like arrangements that shield the dinuclear silver centres, with each silver bonded to two nitrogen donors from one L and one nitrogen from a second L. A Ag···Ag contact is present between each metal centre such that both centres can be described as showing distorted tetrahedral geometries. In the case of 5 a rare single μ₂-κC:κC symmetrically bridging two-electron-donating cyano bridge links silver ions [Ag···Ag distance, 2.7437(10) Å]; the macrocyclic ligands are orientated away from the dinuclear metal centres. In contrast to the behaviour of silver, reaction of cadmium(II) perchlorate with L resulted in a mononuclear sandwich-like complex of type [CdL₂](ClO₄)₂ · CH₃CN (6). Again, the ether oxygens do not coordinate, with each L binding to the cadmium centre only via its three nitrogen donors in a facial arrangement such that a distorted octahedral coordination geometry is attained. Reaction of L with HgX₂ (X = ClO₄, SCN and I) yielded the monomeric species [HgL(ClO₄)₂] (7), [HgL(SCN)₂]·CH₃CN (8) and [Hg₂L₂](HgI₄)₂ · 2L (9), in which all five donors of L are bound to the respective mercury centres. However, reaction of L with Hg(NO₃)₂ in dichloromethane/methanol gave a mononuclear sandwich-like complex [HgL₂](NO₃)₂ · 2CH₃OH (10) without anion coordination. Reaction of K₂PdCl₄ and Pd(NO₃)₂ with L yielded the 1:1 complexes [PdLCl]Cl · H₂O (11) and [PdL(NO₃)]NO₃ · CH₃OH (12), respectively, in which the metal is bound to three nitrogen donors from L along with the corresponding chloride or nitrate anion. Each palladium adopts a distorted square-planar coordination geometry; once again the ether oxygens are not coordinated.     

Syntheses,characterization and X-ray crystal structures of Ni(II) complexes of tridentate monocondensed and tetradentate dicondensed Schiff bases

Two octahedral complexes [Ni(HL¹)₂](ClO₄)₂ (1) and [Ni(HL²)₂](ClO₄)₂ (2) and a square planar complex [Ni(HL³)]ClO₄ (3) have been prepared, where [HL¹ = 3-(2-amino-ethylimino)-butan-2-one oxime, HL² = 3-(2-amino-propylimino)butan-2-one oxime] and H₂L³ = 3-[2-(3-hydroxy-1-methyl-but-2-enylideneamino)-1-methyl-ethylimino]-butan-2-one oxime. All the complexes have been characterized by elemental analyses, spectral studies and room temperature magnetic moment measurements. The molecular structures of all three compounds were elucidated on the basis of X-ray crystallography; complexes 1 and 2 are seen to be the mer isomers.     

Synthesis and characterization of three novel manganese(II) octaaza macrocyclic Schiff base complexes containing a phenanthroline and two pyridyl units as pendant arms. X-ray crystal structure determination of one manganese(II) complex

Three new branched hexadentate amines (N₆), 3,6-bis(2-pyridylmethyl)-3,6-diazaoctane-1,8-diamine (1), 3,7-bis(2-pyridylmethyl)-3,7-diazanonane-1,9-diamine (2) and 3,8-bis(2-pyridylmethyl)-3,8-diazadecane-1,10-diamine (3) have been synthesized. Subsequently, three novel Schiff base macrocyclic complexes containing a phenanthroline and two 2-pyridylmethylpendant arms have been prepared by template [1+1] cyclocondensation of 2,9-dicarboxaldehyde-1,10-phenanthroline and the branched hexadentate amines (1–3), in the presence of Mn(II) in methanol. These complexes have ligands with 18-, 19- and 20-membered hexaaza macrocycles and two 2-pyridylmethyl pendant arms (L¹, L² and L³, respectively). All the complexes have been characterized by elemental analysis and IR spectroscopy. The crystal structure of [MnL¹](ClO₄)₂ · 3CH₃CN was determined and indicates that in the solid state the complex adopts a slightly distorted hexagonal bipyramidal geometry with the Mn(II) ion located within a hexaaza macrocycle with the two 2-pyridylmethyl pendant arms coordinating in axial positions.     

Copper(II), Cobalt(II), and Nickel(II) Complexes of two Novel Pyridine‐derived Macrocyclic Ligands bearing o‐ and pNitrobenzyl Pendant Groups

The pendant‐armed ligands L¹ and L² were synthesized by N‐alkylation of the four secondary amine groups of the macrocyclic precursor L using o‐nitrobenzylbromide (L¹) and p‐nitrobenzylbromide (L²). Nitrates and perchlorates of Cu^II, Ni^II and Co^II were used to synthesize the metal complexes of both ligands and the complexes were characterized by microanalysis, MS‐FAB, conductivity measurements, IR and UV‐Vis spectroscopy and magnetic studies. The crystal structures of L¹, [CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN, [CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH and [NiL²](ClO₄)₂·3CH₃CN·H₂O were determined by single crystal X‐ray crystallography. These structural analysis reveal the free ligand L¹, three mononuclear endomacrocyclic complexes {[CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN and [NiL²](ClO₄)₂·3CH₃CN·H₂O} and one binuclear complex {[CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH} in which one of the metals is in the macrocyclic framework and the other metal is outside the ligand cavity and coordinated to four nitrate ions.     

Copper(II) complexes of tetradentate N2S2 donor sets: Synthesis,crystal structure characterization and reactivity

Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [Cu^II(L¹)Cl]ClO₄ (1), [Cu^II(L²)Cl]ClO₄ (2) and [Cu^II₂(L³)₂Cl₂](ClO₄)₂ (3) were synthesized and isolated in pure form [where L¹ = 1,2-bis(2-pyridylmethylthio)ethane, L² = 1,3-bis(2-pyridylmethylthio)propane and L³ = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [Cu^I₂(L³)₂](ClO₄)₂,0.5H₂O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes 1 and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral.     

Ru(II) with chelating containing N4-type donor quadridentate Pd-oxime metal complexes: Syntheses, spectral characterization, thermal and catalytic properties

Five new metal complexes [Pd(LH)₂] (1), [Pd(L)₂Ru₂(bpy)₄](ClO₄)₂ (2), [Pd(L)₂Ru₂(phen)₄](ClO₄)₂ (3), [Pd(L)₂Ru₂(dafo)₄](ClO₄)₂ (4) and [Pd(L)₂Ru₂(dcbpy)₄](ClO₄)₂ (5), (where, L = ligand, bpy = 2,2′-bipyridine, phen = 1,10-phenantroline, dafo = 4,5-diazafluoren-9-one and dcbpy = 3,3′-dicarboxy-2,2′-bipyridine) have been isolated and characterized by UV-VIS, FT-IR, ¹H NMR, magnetic susceptibility measurements, elemental analysis, molar conductivity, X-ray powder techniques, thermal analyses and their morphology studied by SEM measurements. IR spectra show that the ligand acts in a tetradentate manner and coordinates N₄ donor groups of LH₂ to Pd^II ion. The disappereance of H-bonding (O−H···O) in the trinuclear Ru^II-Pd^II-Ru^II metal complexes, the Ru^II ion centered into the main oxime core by the coordination of the imino groups while the two Ru^II ions coordinate dianionic oxygen donors of the oxime groups and linked to the ligands of bpy, phen, dafo and dbpy. The X-powder results show that 1 metal complex is indicating crystalline nature, not amorphous nature. Whereas, the X-ray powder pattern of the ligand (LH₂) with 2, 3,4 and 5 exhibited only broad humps, indicating its amorphous nature. The catalytic activity of three different complexes were tested in the Suzuki coupling reaction. The 1, 4 and 5 metal complexes catalyse Suzuki coupling reaction between phenylboronic acid and arylbromides affording biphenyls. Also, the thermal results shown that the most stable complex is 1 compound while the less stable is 4 compound.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Copper complexes with 1,10-phenanthrolines tethered to a cyclotriphosphazene platform

The synthesis of two ligands, L¹ and L², each containing two 2-oxy-1,10-phenanthroline moieties attached to the same phosphorus atom of a substituted cyclotriphosphazene ring via an oxy-bridge, but differing in substitution on the biphenyl capping groups, is described. The single-crystal X-ray structure of L¹ · 2CH₂Cl₂ shows an ordered structure in the lattice with channels, containing dichloromethane molecules, running parallel to the a-axis. The reactions of L¹ and L² with [Cu(MeCN)₄](PF₆) afford the dimetallic copper(I) derivatives, [(CuL¹)₂] (PF₆)₂ · CH₂Cl₂ and [(CuL²)₂](PF₆)₂. The single-crystal X-ray structure of the former complex shows that the L¹ ligands of the cation [(CuL¹)₂]²⁺ act as a bridges coordinating to the two copper(I) centres in a helical fashion. The copper atoms have distorted tetrahedral geometries with the interligand dihedral angle being 85°. With copper(II) chloride and copper(II) perchlorate, the monomeric copper(II) complexes, [CuL¹Cl]Cl · 2CH₂Cl₂, [CuL²Cl]Cl · CH₂Cl₂, [CuL¹(OMe)]PF₆ · 2H₂O, [CuL²(OMe)]PF₆ · 2H₂O, [CuL¹(OH₂)](ClO₄)₂ and [CuL²(OH₂)](ClO₄)₂ · H₂O are obtained. The single-crystal X-ray structure of [CuL¹Cl]Cl · 2CH₂Cl₂ shows the copper to be in a square-base pyramidal distorted trigonal-bipyramidal (SBPDTB) environment (τ = 0.57) with L¹ acting as a κ⁴N donor, coordinating via the four nitrogen atoms of the two tethered 1,10-phenanthrolines. In CH₃CN, this complex undergoes hydrolysis via the presence of adventitious water losing one oxyphenanthroline arm to form the centrosymmetric dimetallic species, [(CuL³Cl)₂] · 4CH₃CN · 3H₂O (L³ = [N₃P₃(biph)₂(ophen)O]⁻ where biph = 2,2′-dioxybiphenyl and O replaces an oxyphenanthroline and is attached to the phosphorus of the phosphazene ring). The two monomeric units, which are linked by bridging chlorine atoms, have a distorted square-based pyramidal geometry about the copper with the basal plane made by the ‘ON₂Cl’ ligand set. Spectroscopic (mass spectral, electronic and ESR) and magnetic moment data for the complexes are discussed.     

Synthesis and characterization of Co(II), Ni(II), Zn(II) and Cu(II) complexes with a new tetraazamacrocyclic Schiff base ligand containing a piperazine moiety: X-ray crystal structure determination of the Co(II) complex

Two macrocyclic Schiff base ligands, L¹ [1+1] and L² [2+2], have been obtained in a one-pot cyclocondensation of 1,4-bis(2-formylphenyl)piperazine and 1,3-diaminopropane. Unfortunately, because of the low solubility of both ligands, their separation was unsuccessful. In the direct reaction of these mixed ligands (L¹ and L²) and the appropriate metal ions only [CoL¹(NO₃)]ClO₄, [NiL¹](ClO₄)₂, [CuL¹](ClO₄)₂ and [ZnL¹(NO₃)]ClO₄ complexes have been isolated. All the complexes were characterized by elemental analyses, IR, FAB-MS, conductivity measurements and in the case of the [ZnL¹(NO₃)]ClO₄ complex with NMR spectroscopy.     

Reactivity of triazolyl Schiff bases with Ru(II)-2,2′-bipyridyl: Synthesis,spectroscopic characterization of isomers and their photo-physical properties

The condensation of 3-amino-1H-1,2,4-triazole with benzaldehyde and terephthalaldehyde provides the bidentate and tetradentate Schiff bases 1,2,4-triazolo-3-imino-benzene L¹H and 1,4-bis(1,2,4-triazolo-3-imino)benzene L²H₂, respectively. The well characterized Schiff bases were allowed to react with cis-Ru(bpy)₂Cl₂ · 2H₂O. Isomers of the mononuclear complexes Ru(bpy)₂L¹]PF₆ · NH₄PF₆ (1a, N4) and [Ru(bpy)₂L¹]PF₆ · 0.5NH₄PF₆ (1b, N2), and the dinuclear Ru(II) complexes [Ru(bpy)₂L²Ru(bpy)₂](PF₆)₂ · NH₄PF₆ (2a, N4N4), [Ru(bpy)₂L²Ru(bpy)₂](PF₆)₂ · NH₄PF₆ · 2H₂O (2b, N2N2) and [Ru(bpy)₂L²Ru(bpy)₂](PF₆)₃ · NH₄PF₆ (2c, Ru(II)-Ru(III)) were separated by column chromatography and characterized by their elemental analysis, FAB mass and spectral (IR, NMR, UV–Vis) data. The data obtained suggest that the ligands are bound to the metal centre via the N4 and N2 atoms of the triazole moiety along with the N (imine) atom. The complexes display metal-to-ligand charge-transfer (MLCT) transitions in the visible region from the dπ(Ru^II) → π^∗L transition. Highly intense ligand-based π→π^∗ transitions are observed in the UV region. A dual emission occurs from the N2 and N2N2 isomers.     

Synthesis of two new tripodal ligands and their cyclocondensation with 2-[2-(2-formylphenoxy)ethoxy]benzaldehyde in the presence of manganese(II) and cadmium(II) metal ions

Two new asymmetric tripodal tetraamine ligands, 2-((bis(2-aminoethyl)amino)methyl)benzenamine (L²) and 2-(((2-aminoethyl)(3-aminopropyl)amino)methyl)benzenamine (L³) were synthesized and characterized. [1+1] Macrocyclic Schiff-base complexes containing 1,2-diphenoxyethane head units and a 2-aminobenzyl pendant arm, were synthesized as [MnL⁴(MeOH)](ClO₄)₂ (1), [MnL⁵(MeOH)](ClO₄)₂ (2), [CdL⁴(H₂O)](NO₃)₂ (3) and [CdL⁵(H₂O)](NO₃)₂ (4) from the metal ion templated cyclocondensation reactions of 2-[2-(2-formylphenoxy)ethoxy]benzaldehyde with the (L²) or (L³) tripodal tetraamine ligands. The crystal structure determination of (1) and (4) showed that the complex cations that had formed consisted of pentagonal bipyramidally coordinated Mn(II) and Cd(II) ions, centrally located in a N₃O₂ macrocycle, with one 2-aminobenzyl pendant arm. Supporting ab initio HF-MO calculations have been undertaken using the standard 3-21G^∗ and 6-31G^∗ basis sets.     

pH-dependent self-assembly of copper(II) complexes with a new imidazole-containing polyamine ligand: Synthesis,structure and magnetic property

Four copper(II) complexes were synthesized by reactions of new imidazole-containing polyamine ligand N¹-(2-aminoethyl)-N¹-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine (HL) with Cu(ClO₄)₂ · 6H₂O under different pH and their structures were characterized by X-ray crystallography. Interestingly, the complexes have diverse structures from protonated ligand [H₃(HL)][CuCl₄] · Cl (1), dinuclear [Cu₂(HL)₂Cl](ClO₄)₃ · H₂O (2), one-dimensional chain polynuclear {[Cu(L)](ClO₄)}_n (3) to cyclic-tetranuclear [Cu₄(L)₄](ClO₄)₄ · 3CH₃CN (4) coordination compounds by varying reaction pH from acidic to basic. The results indicate that the reaction pH has great impact on the formation and structure of the complexes. The magnetic measurements show that there are antiferromagnetic interactions between the Cu(II) centers with g = 2.09, J = −39.0 cm⁻¹ and g = 2.17, J = −36.8 cm⁻¹ for 3 and 4, respectively.     

Synthesis,crystal structures,DNA binding and oxidative cleavage studies of copper(II) complexes of N2S2 tetradentate ligands

Two new copper(II) complexes with aminothioether ligands, [Cu(L¹)(ClO₄)](ClO₄) · 0.5H₂O (1) and [Cu(L²)(H₂O)](ClO₄)₂ · H₂O (2) (L¹ = 2-benzyl-1,3-bis(aminoethylthio)propane and L² = 2-(4-butylbenzyl)-1,3-bis(aminoethylthio)propane), have been synthesized and characterized. The single crystal X-ray diffraction analysis reveals that both 1 and 2 adopt distorted square pyramidal geometries. The binding modes of both complexes with calf thymus DNA were investigated by UV–Vis and CD spectroscopies. The results show that both complexes mainly adopt an electrostatic attraction binding mode with DNA and the binding constants are (1.62 ± 0.02) × 10³ and (2.02 ± 0.02) × 10³ M⁻¹, respectively. Both complexes are able to cleave pBR322 plasmid DNA efficiently in the presence of ascorbic acid and the activity of 2 is higher than that of 1. The DNA cleavage by 1 and 2 were inhibited strongly in the presence of DMSO and tert-butyl alcohol, which suggests that hydroxyl radicals are the reactive oxygen species for the cleavage.     

Synthesis and characterization of some new Co(II) and Cd(II) macroacyclic Schiff-base complexes containing piperazine moiety

Three Cd(II) or Co(II) macroacyclic Schiff-base complexes [CoL¹Br]ClO₄ (1), [CdL²Cl]ClO₄ (2) and [CdL³(NO₃)]ClO₄ (3) were prepared by template condensation of 2-pyridinecarboxaldehyde and three different amines containing piperazine moiety, N,N′-bis(2-aminoethyl)piperazine, N,N′(2-aminoethyl)(3-aminopropyl)piperazine and N,N′-bis(3-aminopropyl)piperazine, in the presence of Co(II) or Cd(II) metal ions, respectively. All complexes have been studied with IR, FAB mass and microanalysis and for complex (3) by ¹H and ¹³C NMR spectra. One of these complexes, [CdL³(NO₃)]ClO₄ (3) has been characterized through X-ray crystallography. In complex (3), the Cd(II) ion is coordinated by the six nitrogen donor atoms from the ligand and by one oxygen atom from a monodentate nitrate ion in a N₆O environment.     

Synthesis, crystal structure and spectroscopic properties of some cadmium(II) complexes with three polyamine and corresponding macroacyclic Schiff base ligands

Three Cd(II) macroacyclic Schiff base complexes [CdL⁴(NO₃)₂] (4), [CdL⁵(NO₃)₂] (5), [CdL⁶(NO₃)₂] (6) were prepared by template condensation of 2-pyridinecarboxaldehyde with N1-(2-nitrobenzyl)-N1-(2-aminoethyl)ethane-1,2-diamine (L¹), N1-(2-nitrobenzyl)-N1-(2-aminoethyl)propane-1,3-diamine (L²) or N1-(2-nitrobenzyl)-N1-(3-aminopropyl)propane-1,3-diamine (L³), in the presence of cadmium metal ion, respectively. Three Cd(II) complexes with L¹, L² and L³ were also synthesized. All complexes have been studied with IR, ¹H NMR, ¹³C NMR, DEPT, COSY, HMQC and microanalysis. Two of these complexes, [CdL⁴(NO₃)₂] (4) and [CdL¹(NO₃)₂] (1) have been characterized through X-ray crystallography. In complex 4, the Cd is in a six-coordinate environment comprised of the ligand N₄-donor set and two oxygen atoms of two nitrate groups. In the polyamine complexes (1, 2 and 3) Cd and ligand are in a ratio of 1:1. Supporting ab initio HF-MO calculations have been undertaken using the standard 3-21G^∗ and 6-31G^∗ basis sets.     

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.     

Luminescent europium(III) complexes of tripodal heptadentate N7 ligands containing three imidazole groups

Luminescent Eu^III complexes with tripodal heptadentate N₇ ligands containing three imidazole groups, [Eu^III(H₃L^2-H)(ac)](ClO₄)₂·H₂O (1), [Eu^III(H₃L^2-Me)(ac)](ClO₄)₂·2EtOH (2), and [Eu^III(H₃L^4-Me)(ac)](ClO₄)₂·H₂O (3), were synthesized and characterized, where H₃L^2-H, H₃L^2-Me, and H₃L^4-Me are the tripodal ligands derived from the 1:3 condensation of tris(2-aminoethyl)amine and either 4-formylimidazole, 2-methyl-4-formylimidazole, and 4-methyl-5-formylimidazole, respectively, and ac denotes an acetate ion. Single-crystal X-ray analyses revealed that each Eu^III ion is coordinated by a tripodal heptadentate N₇ ligand and two oxygen atoms of the acetate ion as a bidentate ligand. The complexes displayed sharp emission bands based on the f-f transitions by excitation at 261 nm in acetonitrile. The emission intensities increased in the order 1 < 2 < 3 in acetonitrile, while the emission spectra were quenched in aqueous solution due to the partial dissociation of the acetate ion and tripodal ligand.