Preparation,spectroscopic characterization and X-ray crystal and molecular structures of nickel(II), copper(II) and zinc(II) complexes of the Schiff base formed from isatin and S-methyldithiocarbazate (Hisa-sme)

Complexes of general formula, [M(isa-sme)₂] · n(solvate) [M = Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺; isa-sme = monoanionic form of the Schiff base formed by condensation of isatin with S-methyldithiocarbazate; n = 1 or 1.5; solvate = MeCN, DMSO, MeOH or H₂O] have been synthesized and characterized by a variety of physicochemical techniques. An X-ray crystallographic structure determination of the [Ni(isa-sme)₂] · MeCN complex reveals a six-coordinate, distorted octahedral geometry. The two uninegatively charged, tridentate, Schiff base ligands are coordinated to the nickel(II) ion meridionally via the amide O-atoms, the azomethine N-atoms and the thiolate S-atoms. By contrast, the crystal structure of [Zn(isa-sme)₂] · MeOH shows a four-coordinate distorted tetrahedral geometry. The two dithiocarbazate ligands are coordinated as N, S bidentate chelates with the amide O-atom not coordinated. The structure of the copper(II) complex [Cu(isa-sme)₂] · DMSO is complicated and comprises two different complexes in the asymmetric unit, one four- and the other five-coordinate. The four-coordinate copper(II) has a distorted (flattened) tetrahedral geometry as seen in the Zn(II) analogue whereas the five-coordinate copper(II) has a distorted square-pyramidal geometry with one ligand coordinated to the copper(II) ion as a tridentate (N, S, O) ligand and the other coordinated as a bidentate N, S chelate. EPR spectroscopy indicates that in solution only one form is present, that being a distorted tetrahedral complex.     

Preparation and structural characterization of nickel(II), cobalt(II), zinc(II) and tin(IV) complexes of the isatin Schiff bases of S-methyl and S-benzyldithiocarbazates

The molecular structures of the isatin Schiff bases of S-methyldithiocarbazate (Hisasme) and S-benzyldithiocarbazate (Hisasbz) have been determined by X-ray diffraction and their complexes of general formula [ML₂]·n(solvate) [M = Co²⁺, Ni²⁺, Zn²⁺; L = anionic forms of Hisasme or Hisasbz; solvate = DMF, DMSO; n = 1, 2] and [Sn(L)Ph₂Cl]·nMeOH (n = 0, 1) have been synthesized and characterized by a variety of physicochemical techniques and X-ray diffraction. The bis-ligand complexes, [Ni(isasbz)₂]·2DMSO and [Co(isasme)₂]·DMF have a six-coordinate, distorted octahedral geometry with the two uninegatively charged tridentate ONS ligands coordinated to the metal ions meridionally via the amide O-atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. By contrast, the crystal structure of [Zn(isasbz)₂]·2DMF shows a four-coordinate distorted tetrahedral geometry with the two Schiff bases coordinated as NS bidentate ligands via the azomethine nitrogen atoms and the thiolate sulfur atoms. Steric constraints of the rigid tridentate ligands lead to unusual ‘pseudo-coordination’ of the O-donors which occupy sites close to the metal but too distant to be considered as true coordinate bonds.The crystal structures of the tin(IV) complexes [SnLPh₂Cl]·nMeOH (L = isasme and isasbz; n = 0, 1) also show that the Schiff bases act as monoanionic bidentate NS chelating agents coordinating the tin(IV) ion via the azomethine nitrogen atoms and the thiolate sulfur atoms, the tin atom in each complex is five-coordinate with a highly distorted geometry intermediate of square pyramidal and trigonal bipyramidal. Again Sn?O contacts are weak and do not qualify as coordinate bonds.     

Metal-organic chains constructed from pre-organized N2S2 donor ligands

Three new N₂S₂ donor ligands 1,1′-((2-(2-(phenylthio)phenylthio)phenyl)methylene)bis(3,5-R-1H-pyrazole), R = H (L^H), R = Me (L^Me), R = i-Pr (L^i-Pr) have been prepared and characterized. These bifunctional ligands incorporate two distinct chelate donor systems, by virtue of the presence of bispyrazole and bisthioether functions. The preferred conformation of these ligands is such that the N₂ and S₂ donor moieties may be oriented in opposite directions, thus favoring the formation of molecular chains when treated with AgBF₄. The X-ray structures of Ag(I) complexes show that, depending on the steric hindrance present on the pyrazole rings, these ligands behave as κ⁴-SSNN-μ bridging tetradentate (when R = H), or κ³-SNN-μ bridging tridentate (when R = Me, i-Pr). Interestingly, [Ag(L^H)]BF₄ crystallizes in the chiral space group P4₁, with the molecular chain that is folded around the 4₁ screw axis.     

Synthesis and characterization of tin(IV)/organotin(IV) complexes with 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone [HBPCT]: X-ray crystal structure of [SnCl3(BPCT)]

Four new tin(IV)/organotin(IV) complexes, [SnCl₃(BPCT)] (2), [MeSnCl₂(BPCT)] (3), [Me₂SnCl(BPCT)] (4), and [Ph₂SnCl(BPCT)] (5), have been synthesized by the direct reaction of 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone [HBPCT, (1)] and stannic chloride/organotin(IV) chloride(s) in absolute methanol under purified nitrogen. HBPCT and its tin(IV)/organotin(IV) complexes (2–5) were characterized by CHN analyses, molar conductivity, UV-Vis, FT-IR, and ¹H NMR spectral studies. In all the complexes, tin(IV) was coordinated via pyridine-N, azomethine-N, and thiolato-S from 1. The molecular structure of 2 has been determined by X-ray single-crystal diffraction analysis. Complex 2 is a monomer and the central tin(IV) is six-coordinate in a distorted octahedral geometry. The crystal system of 2 is monoclinic with space group P121/n1 and the unit cell dimensions are a?=?8.3564(3)?Å, b?=?23.1321(8)?Å, c?=?11.9984(4)?Å.     

Synthesis,characterization, and X-ray crystal structure analysis of Cd(ΙΙ) and Cu(II) complexes of an acyclic pentadentate Schiff base

Cd(ΙΙ) and Cu(II) complexes of an acyclic pentadentate Schiff base were prepared by template condensation of two equivalents of 2-acetylpyridine with one equivalent of bis(3-aminopropyl)amine in methanol. The resulting complexes [CdL(NO₃)]ClO₄ (1) and [CuL](ClO₄)₂ · CH₃CN (2) were characterized by X-ray crystallography, elemental analysis, IR and mass spectrometry in both cases and by NMR in the case of 1. The X-ray crystallographic structure determination of these complexes revealed six-coordinate distorted octahedral geometry for 1, with the sixth coordination by nitrate and five-coordinate for 2 with trigonal-bipyramidal Cu(II).     

Syntheses and characterization of nickel(II), zinc(II) and palladium(II) complexes derived from three pyrazole-based polydentate ligands

Two pyrazole-based polydentate ligands, 1,3-bis(5-methyl-3-phenylpyrazol-1-yl)-propan-2-ol (Hmppzpo) and 1,3-bis(5-methyl-3-p-isopropylphenylpyrazol-1-yl)-propan-2-ol (Hmcpzpo), have been synthesized. A third ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (Hdmpzpo), has been synthetically modified. Seven new M(II) coordination compounds of general formula M₂L₂X₂ (M?=?Zn, Ni; X?=?NO₃ or ClO₄; L?=?dmpzpo, mppzpo or mcpzpo) or MLX (M?=?Pd; L?=?dmpzpo; X?=?Cl) were synthesized and structurally characterized by elemental analysis and FT-IR analysis. The crystal structures of [Zn₂(μ-dmpzpo-O,N,N′)₂(NO₃)₂]?·?2H₂O (1?·?2H₂O), [Ni₂(μ-dmpzpo-O,N,N′)₂(CH₃CN)₂](ClO₄)₂ (2) and Pd(μ-dmpzpo-N,N′)Cl₂ (4) were determined by single-crystal X-ray crystallography. The crystal structures show that complexes 1?·?2H₂O and 2 are center-symmetric dinuclear compounds, with two metal ions bridged by two alkoxo groups and each metal ion with a distorted square-pyramidal environment. The palladium complex, 4, displayed square-planar coordination geometry around the Pd(II) ion with trans arrangement.     

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.     

Synthesis,spectroscopic characterization and thermal behavior of cadmium(II) complexes of S-methyldithiocarbazate (SMDTC) and S-benzyldithiocarbazate (SBDTC): X-ray crystal structure of [Cd(SMDTC)3] · 2NO3

Two new cadmium(II) complexes of the empirical formulae [Cd(SMDTC)₃] · 2NO₃ (1) and [Cd(SBDTC)₂] · 2NO₃ (2) have been synthesized and characterized by elemental analyses, UV–Vis, IR, ¹H NMR and TGA techniques. In complex 1, the six coordination sites around cadmium are occupied by three neutral SMDTC molecules with N and S donor atoms from each ligand molecule, whereas in complex 2 the cadmium center is four coordinated with two relatively larger SBDTC ligands chelating with N and S donor atoms in the neutral thione form. In the solid state, thermal gravimetric analysis shows that both complexes are relatively volatile in nature and undergo facile thermal decomposition above 120 °C to form the metal sulfide followed by stepwise loss of ligand molecules. The crystal and molecular structure of complex 1 has been established by the X-ray diffraction method. The central cadmium(II) atom has an octahedral geometry with three five-membered chelate rings formed by SMDTC ligands. The crystal structure consists of parallel layers of cations and anions. The SMDTC molecules in cations are arranged with their N donor groups directed towards the anion layer in an alternating fashion and form hydrogen bonds with the O atoms of the anion.     

Tin(IV) complexes of 2‐benzoylpyridine N(4)‐phenyl‐thiosemicarbazone: spectral characterization,structural studies and antifungal activity

Three tin(IV) complexes of 2‐benzoylpyridine N(4)‐phenylthiosemicarbazone (H2Bz4Ph) were prepared: [Sn(L)Cl₃] (1), [BuSn(L)Cl₂] (2) and [(Bu)₂Sn(L)Cl] (3), in which L stands for the anionic ligand formed upon complexation with deprotonation and release of HCl. The complexes were characterized by a number of spectroscopic techniques. The crystal structures of H2Bz4Ph and complex 3 were determined. The antifungal activity of the ligand and its tin(IV) complexes was tested against Candida albicans. The thiosemicarbazone proved to be more active than the tin(IV) complexes. Copyright © 2003 John Wiley & Sons, Ltd.     

Nickel(II), copper(II) and zinc(II) complexes withN-phenylglycine in water-methanol solution

The complex equilibria of the Ni(II), Cu(II), and Zn(II) complexes withN-phenylglycine have been studied by computer analysis of potentiometric data. The mode of coordination has been established by¹H NMR and IR studies.

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Nickel(II), Kupfer(II) und Zink(II)-Komplexe mitN-Phenylglycin in Wasser-Methanol-Lösung

Zusammenfassung Anhand der Computer-Analyse von potentiometrischen Daten wurden die Bildungsgleichgewichte von Nickel(II), Kupfer(II) und Zinc(II)-Komplexen mitN-Phenylglycin untersucht. Zur Bestätigung des Koordinationstyps wurden¹H-NMR- und IR-Messungen vorgenommen.

     

Synthesis, crystal structure, spectroscopic and photoluminescence studies of manganese(II), cobalt(II), cadmium(II), zinc(II) and copper(II) complexes with a pyrazole derived Schiff base ligand

Varying coordination modes of the Schiff base ligand H₂L [5-methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] towards different metal centers are reported with the syntheses and characterization of four mononuclear Mn(II), Co(II), Cd(II) and Zn(II) complexes, [Mn(H₂L)(H₂O)₂](ClO₄)₂(MeOH) (1), [Co(H₂L)(NCS)₂] (2), [Cd(H₂L)(H₂O)₂](ClO₄)₂ (3) and [Zn(H₂L)(H₂O)₂](ClO₄)₂ (4), and a binuclear Cu(II) complex, [Cu₂(L)₂](ClO₄)₂ (5). In the complexes 1-4 the neutral ligand serves as a 3N,2O donor where the pyridine ring N, two azomethine N and two carbohydrazine oxygen atoms are coordinatively active, leaving the pyrazole-N atoms inactive. In the case of complex 5, each ligand molecule behaves as a 4N,O donor utilizing the pyridine N, one azomethine N, the nitrogen atom proximal to the azomethine of the remaining pendant arm and one pyrazole-N atom to one metal center and the carbohydrazide oxygen atom to the second metal center. The complexes 1-4 are pentagonal bipyramidal in geometry. In each case, the ligand molecule spans the equatorial plane while the apical positions are occupied by water molecules in 1, 3 and 4 and two N bonded thiocyanate ions in 2. In complex 5, the two Cu(II) centers have almost square pyramidal geometry (τ = 0.05 for Cu1 and 0.013 for Cu2). Four N atoms from a ligand molecule form the basal plane and the carbohydrazide oxygen atom of a second ligand molecule sits in the apex of the square pyramid. All the complexes have been X-ray crystallographically characterized. The Zn(II) and Cd(II) complexes show considerable fluorescence emission while the remaining complexes and the ligand molecule are fluorescent silent.     

Syntheses,crystal structures,and properties of Ni(II) and Co(III) complexes derived from tripod polypyridine ligands containing N7 or N6 donor set atoms

New complexes [Ni^II(pbpaen)](ClO₄)₂ (1) and [Co^III(pbpaen)](ClO₄)₃ (2) (pbpaen = N′-(pyridin-2-ylmethyl)-N,N-bis {2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine) have been synthesized and characterized by IR and UV–Vis spectroscopies. An X-ray structure of the nickel(II) complex shows that [Ni(pbpaen)](ClO₄)₂ (1) crystallizes in the monoclinic space group P2_1/c. The cation [Ni(pbpaen)]²⁺ is pseudo-octahedral with one of the three pyridyl nitrogen atom uncoordinated. The crystal lattice of this complex is stabilized by intra and intermolecular hydrogen bonding systems, giving one-dimensional sheets like arrays. All attempts to obtain nickel or cobalt complexes with protonated forms of the ligand resulted in isolation of only [Co^III(bpaen)](ClO₄)₃ (3) compound in which the tripod pbpaen ligand has lost one of the three pyridylmethyl groups, procuring then bpaen ligand {bpaen = N,N-bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine}. The X-ray crystal structure reveals that the compound 3 crystallizes in the orthorhombic space group Pna2 with the Co³⁺ ion having a distorted-octahedral environment. These two ligands with strong-field N donor stabilise the +3 oxidation state of the Co center.     

Palladium(II) complexes with S-benzyl dithiocarbazate and S-benzyl-N-isopropylidenedithiocarbazate: Synthesis,spectroscopic properties and X-ray crystal structures

Two new palladium(II) bis(NS) chelates, bis(S-benzyl dithiocarbazato)palladium(II) (1) and bis(S-benzyl-N-isopropylidenedithiocarbazato)palladium(II) (2), have been prepared and characterized using single-crystal X-ray diffraction and spectroscopic (electronic, IR and NMR) techniques. Complex 1 has a perfectly square planar trans configuration (point group C_i), while complex 2 has a distorted square planar cis configuration.     

Transition metal complexes with thiosemicarbazide-based ligands. Part LIV. Nickel(II) complexes with pyridoxal semi- (PLSC) and thiosemicarbazone (PLTSC). Crystal and molecular structure of [Ni(PLSC)(H2O)3](NO3)2 and [Ni(PLTSC-H)py]NO3

This paper describes the synthesis of the first Ni(II) complexes with pyridoxal semicarbazone (PLSC), viz. Ni(PLSC)Cl₂ · 3.5H₂O (1), [Ni(PLSC)(H₂O)₃](NO₃)₂ (2), Ni(PLSC)(NCS)₂ · 4H₂O (3), [Ni(PLSC-2H)NH₃] · 1.5H₂O (4), as well as two new complexes with pyridoxal thiosemicarbazone (PLTSC), [Ni(PLTSC-H)py]NO₃ (5) and [Ni(PLTSC-H)NCS] (6). Complexes 1–3 are paramagnetic and have most probably an octahedral structure, for complex 2 this was proved by X-ray diffraction analysis. In contrast, complexes 4–6 are diamagnetic and have a square-planar structure, and in the case of complex 5 this was also confirmed by X-ray structural analysis. In all cases the Schiff bases are coordinated as tridentate ligands with an ONX (X = O, PLSC; X = S, PLTSC) set of donor atoms. With the complexes involving the neutral form of PLSC and the monoanionic form of PLTSC, the PL moiety is in the form of a zwitterion. In addition to the above-mentioned techniques, all the complexes were characterized by measuring their molar conductivities, UV–Vis and partial IR spectra.     

Synthesis and structural characterization of cobalt(II) and zinc(II) complexes with 2-(indazol-1-yl)-2-thiazoline (TnInA). X-ray characterization of [CoCl2(TnInA)2] · C2H6O and [(M)(TnInA)2(H2O)2](NO3)2 (M = Co, Zn)

Several complexes of 2-(indazol-1-yl)-2-thiazoline (TnInA) with the divalent ions Co and Zn have been synthesized by the direct combination of the ligand and the metal chloride or nitrate hydrated salts in ethanol. These complexes have been characterized by a variety of physical–chemical techniques. Moreover, the structures of [CoCl₂(TnInA)₂] · C₂H₆O (1) and [(M)(TnInA)₂(H₂O)₂](NO₃)₂ (M = Co, 3; Zn, 4) were determined by single-crystal X-ray diffraction. In all the complexes, the ligand TnInA bonds to the metal ion through the indazole and thiazoline nitrogen atoms. In complex 1 the environment around the cobalt ion may be described as a distorted octahedron with two TnInA ligands and two chlorine ligands. Compounds 3 and 4 are isostructural with a distorted octahedral geometry around the metal center, being linked to two water molecules and two TnInA ligands. However, in complex [ZnCl₂(TnInA)] (2) the zinc atom is four-coordinated with a probable tetrahedral environment with two chloro ligands and one TnInA ligand bonded to the metal ion.     

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,spectroscopic, and thermal analyses of trinuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with some sulfa derivatives

New bi- and trihomonuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with sulfa-guanidine Schiff bases have been synthesized for potential chemotherapeutic use. The complexes are characterized using elemental and thermal (TGA) analyses, mass spectra (MS), molar conductance, IR, ¹H-NMR, UV-Vis, and electron spin resonance (ESR) spectra as well as magnetic moment measurements. The low molar conductance values denote non-electrolytes. The thermal behavior of these chelates shows that the hydrated complexes lose water of hydration in the first step followed by loss of coordinated water followed immediately by decomposition of the anions and ligands in subsequent steps. IR and ¹H-NMR data reveal that ligands are coordinated to the metal ions by two or three bidentate centers via the enol form of the carbonyl C=O group, enolic sulfonamide S(O)OH, and the nitrogen of azomethine. The UV-Vis and ESR spectra as well as magnetic moment data reveal that formation of octahedral [Mn₂L¹(AcO)₂(H₂O)₆] (1), [Co₂(L¹)₂(H₂O)₈] (2), [Ni₂L¹(AcO)₂(H₂O)₆] (3), [Mn₃L²(AcO)₃(H₂O)₉] (5), [Co₃L²(AcO)₃(H₂O)₉] · 4H₂O (6), [Ni₃L²(AcO)₃(H₂O)₉] · 7H₂O (7), [Mn₃L³(AcO)₃(H₂O)₆] (9), [Co₂(HL³)₂(H₂O)₈] · 4H₂O (10), [Ni₃L³(AcO)₃(H₂O)₉] (11), [Mn₃L⁴(AcO)₃(H₂O)₉] · H₂O (13), [Co₂(HL⁴)₂(H₂O)₈] · 5H₂O (14), and [Ni₃L⁴(AcO)₃(H₂O)₉] (15) while [Zn₂L¹(AcO)₂(H₂O)₂] (4), [Zn₃L²(AcO)₃(H₂O)₃] · 2H₂O (8), [Zn₃L³(AcO)₃(H₂O)₃] · 3H₂O (12), and [Zn₃L⁴(AcO)₃(H₂O)₃] · 2H₂O (16) are tetrahedral. The electron spray ionization (ESI) MS of the complexes showed isotope ion peaks of [M]⁺ and fragments supporting the formulation.     

Synthesis,characterization, electrochemical behaviour and X-ray crystal structures of nickel(II) complexes with a N2O4 donor set macrocyclic Schiff base ligand

Two nickel(II) complexes of [1 + 1] macrocyclic Schiff base ligand (L) have been prepared by cyclocondensation reactions between 1,3-diamino-2-propanol and 2-[3-(2-formylphenoxy)-2-hydroxypropoxy] benzaldehyde, using NiX₂ (X = Br, and I) salts as template agents, and characterized by elemental analyses, IR, molar conductivity and electronic spectra in both solid and solution states. The single-crystal X-ray diffractions of the complexes are also reported that contain nickel(II) ion in a distorted octahedral geometry coordination of N₂O₃X (X = Br, I and NO₃). In all complexes the ligand behaves as a pentadentate ligand. Cyclic voltammetric studies of nickel(II) complexes indicate a quasi-reversible redox wave in the negative potential range.     

Syntheses,crystal structures,and some spectroscopic properties of zinc(II) complexes with N2O2 ligands derived from m-phenylenediamine and m-aminobenzylamine

The reaction of bis(salicylidene)-m-phenylenediamine with zinc(II) ion affords a 2?:?2 dinuclear zinc(II) complex formulated as [Zn₂(L¹)₂]. A similar 2?:?2 dinuclear zinc(II) complex, [Zn₂(L²)₂], can be obtained by reaction of bis(salicylidene)-m-aminobenzylamine with zinc(II) ion. These two dinuclear complexes slightly differ in their crystal structures, especially coordination environments around the zinc(II) centers, depending on the dissimilar flexibilities of the two ligands. The differences between the two complexes are reflected in their diffuse reflectance and photoluminescence behaviors.     

Zn(II) complexes with pyridine derived N6 and N8 donor azamacrocyclic ligands

A novel N6 macrocyclic ligand, L¹ (2,8,14,20-tetramethyl-3,7,15,19,25,26-hexaaza-tricyclo[19.3.1.1^9,13]hexacosa-1(24),9,11,13(26),21(25),22-hexaene), was obtained by reduction of the 2 + 2 condensation product of 2,6-diacetylpyridine and propane-1,3-diamine. Zinc(II) complexes of L¹, of a related N8 macrocycle, L³ (3,6,9,17,20,23,29,30-octaaza-tricyclo[23.3.1.1[11,15]]triaconta-1(28),1,13,15(30),25(29),26-hexaene), similarly prepared by 2 + 2 condensation of 2,6-diformylpyridine and diethylenetriamine and of a tetra N-2-cyanoethyl derivative of a homologue of L¹ prepared from diformyl pyridine and ethane-1,2-diamine, L² (3-[6,14,17-tris-(2-cyano-ethyl)-3,6,14,17,23,24-hexaaza-tricyclo[17.3.1.1^8,12] tetracosa-1(23),8(24),9,11,19,21-hexaen-3-yl]-propionitrile), were prepared. Structures were determined for [ZnL¹](ClO₄)₂ · H₂O, [ZnL²](NO₃)₂ and [Zn₂L³(NO₃)₂](NO₃)₂ · H₂O. The [ZnL¹](ClO₄)₂ · H₂O and [ZnL²](NO₃)₂ complexes present a mononuclear endomacrocyclic structure with the metal in an octahedral distorted environment coordinated by the six donor nitrogen atoms from the macrocyclic backbone while the complex [Zn₂L³(NO₃)₂](NO₃)₂ · H₂O is dinuclear with both metal atoms into the macrocyclic cavity coordinated by four donor nitrogen atoms from the macrocyclic framework and one oxygen atom from one monodentate nitrate anion, in a distorted square pyramidal arrangement.