Synthesis, characterization, fluorescence and redox features of new vic-dioxime ligand bearing pyrene and its metal complexes (original) (raw)
Polyhedron, 2002
A new series of binuclear unsymmetrical compartmental oxime complexes (1 Á/5) [M 2 L] [M 0/Cu(II), Ni(II)] have been synthesized using mononuclear complex [ML] (L 0/1,4-bis[2-hydroxy-3-(formyl)-5-methylbenzyl]piperazine), hydroxylamine hydrochloride and triethylamine. In this system there are two different compartments, one has piperazinyl nitrogens and phenolic oxygens and the other compartment has two oxime nitrogens and phenolic oxygens as coordinating sites. The complexes were characterized by elemental and spectral analysis. Electrochemical studies of the complexes show two step single electron quasi-reversible redox processes at cathodic potential region. For copper complexes E 1 pc 0/(/0.18 to (/0.62 and E 2 pc 0/(/1.18 to (/1.25 V, for nickel complexes E 1 pc 0/(/0.40 to (/0.63 and E 2 pc 0/(/1.08 to (/1.10 V and reduction potentials are sensitive towards the chemical environment around the copper and nickel atoms. The nickel(II) complexes undergo two electrons oxidation. The first one electron oxidation is observed around '/0.75 V and the second around '/1.13 V. ESR Spectra of the binuclear copper(II) complexes [Cu 2 L](ClO 4 ), [Cu 2 L(Cl)], [Cu 2 L(NO 3 )] shows a broad signal at g 0/2.1 indicating the presence of coupling between the two copper centers. Copper(II) complexes show a magnetic moment value of m eff around 1.59 B.M at 298 K and variable temperature magnetic measurements show a (/2J value of 172 cm (1 indicating presence of antiferromagnetic exchange interaction between copper(II) centres.
Polyhedron, 2001
Acyclic dicompartmental ligands suitable for the complexation of transition-metal ions which can form mononuclear, homo-or heterodinuclear complexes have been synthesised. The mononuclear complexes ML 1 (M= Cu, Ni) where L 1 = N,N%-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiimine (alkyl = ethylene, L 1a ; propylene, L 1b ; butylene, L 1c ; triethylenetetraamine, L 1d ); ML 2 (M=Cu, Ni) where L 2 =N,N%-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiamine (alkyl =ethylene, L 2a ; propylene, L 2b ); and ML 3 (M=Cu, Ni) where L 3 = N,N%-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-bromobenzyl]alkyldiimine (alkyl =ethylene, L 3a ; propylene, L 3b ; butylene, L 3c ) have been synthesised and characterised by C, H, N analysis, IR, electronic and ESR spectra. The complexes CuH 2 L 1a (1), CuH 2 L 2a (4), NiH 2 L 1a (9) and NiH 2 L 1d (12) have been analysed by X-ray crystallography. Complexes 1 and 4 have square pyramidal geometry. The coordination geometry around the metal ion in complex 9 is square planar and in complex 12 it is octahedral. Electrochemical studies of the complexes show a single quasi-reversible electron transfer process at the negative potential region. For copper complexes (1-8) E pc = − 1.10 to −0.70 V, for nickel complexes (9-12) E pc = −1.0 to −0.85 V. Copper complexes show a magnetic moment value of v eff = 1.70-1.75 BM. The square planar nickel complexes are diamagnetic whereas the nickel complex (12) with octahedral structure has a magnetic moment value of 3.12 BM.
Crystal Growth & Design, 2019
A series of new polynuclear complexes of divalent Ni and Cu with 2-cyano-2-oximino-acetic acid (later AACO 2-) was obtained as the result of the ligand modification reaction in the process of complexation, using 2-cyano-2-oximino-acetates such as methyl-(later as MeCO), and ethyl-(as ECO later on). Synthesized compounds were characterized by spectroscopic methods, thermal analysis, magnetochemistry and X-ray crystallography. Crystal data revealed the formation of the dimeric [Ni(AACO)(H 2 O) 3 ] 2 •H 2 O (1), trimeric K 2 [Ni 3 (AACO) 4 (H 2 O) 4 ]•4H 2 O (2), and K 2 [Cu 3 (AACO) 4 (H 2 O) 4 ]•4H 2 O (3) complexes, with bridging NO-groups cyanoxime dianions. In the latter two compounds, the AACO 2anions adopt cis-arrangements around metal centers. One mononuclear complex of K 2 [Cu(AACO) 2 (H 2 O)]•2H 2 O (4) composition was isolated and characterized as well, where the cyanoxime forms the trans-complex 4. There is moderate-to-strong antiferromagnetic coupling between metal centers in polynuclear complexes. Data of thermal analysis studies revealed high-energy properties for dehydrated complexes 3 and 4, which violently decompose at ~200 o C. These compounds may be viewed as room temperature completely safe, but heat-triggered actuators, because of their pronounced mechanical action upon leaving the system (crucible). Final products of thermal decomposition are: Ni and NiO for 1, and the mixture of NiO and K 2 O for 2, with metallic copper for 3 and 4.
Polyhedron, 2006
A new end-off type acyclic ligand with two N-methyl piperazine arms, 2,6-bis[(4-methyl piperazin-1-yl)]-4-formyl phenol [L], has been synthesized by a simple Mannich reaction. The mono and binuclear complexes of Cu(II), Ni(II) and Zn(II) have been prepared. The complexes were characterized by elemental and spectral analysis. The EPR spectrum of the mononuclear copper complex shows four hyperfine splittings and the binuclear complex shows a broad signal due to an anti-ferromagnetic interaction. The room temperature magnetic moment of the mono and binuclear copper complexes are found to be 1.72 l B (l eff ) and 1.58 l B (l eff ), respectively. The mononuclear Ni(II) complex is square planar and diamagnetic, whereas the six-coordinated binuclear Ni(II) complex shows a magnetic moment value of 2.98 l B (l eff ). Cyclic voltammetric studies evidenced one irreversible reduction wave for all the mononuclear complexes and two irreversible one-electron reduction waves for the binuclear complexes are obtained in the cathodic region. In the anodic region, one irreversible oxidation wave for the mononuclear nickel(II) complex and two irreversible oxidation waves for the binuclear nickel(II) complexes are obtained. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the mono and binuclear copper(II) complexes as catalysts and on the hydrolysis of 4-nitrophenylphosphate using the mono and binuclear copper(II), nickel(II) and zinc(II) complexes as catalysts were carried out. The binuclear complexes have higher rate constant values than those of the corresponding mononuclear complexes. The rate constant values for the complexes for the hydrolysis are in the order nickel(II) > copper(II) > zinc(II).
Journal of Chemical Sciences, 2009
The novel vic-dioxime ligand containing the 4-amino-1-benzyl piperidine group, N,N′-(4amino-1-benzyl piperidine)-glyoxime, (LH 2 ) has been prepared from 4-amino-1-benzyl piperidine with anti-dichloroglyoxime at -15°C in absolute THF. Mononuclear Ni II metal complex has been obtained with 1 : 2 metal/ligand ratio. The Ni II complex of this ligand is proposed to be square planar geometry. IR spectra show that the ligand acts in a tetradentate manner and coordinates N 4 donor groups of LH 2 to Ni II ion. The detection of H-bonding (O-H⋅⋅⋅O) in the [Ni(LH) 2 ] (1) metal complex by IR spectra supported the square-planar MN 4 coordination of mononuclear complex. The disappereance of H-bonding (O-H⋅⋅⋅O) in the [Ni(L) 2 (BPh 2 ) 2 ] (2) complex shows that the BPh + 2 -capped groups (BPh + 2 cation formed BPh 4 anion) attaches to the main oxime core. MN 4 coordination of the [Ni(LH) 2 ] (1) and [Ni(L) 2 (BPh 2 ) 2 ] (2) metal complexes were also determined by 1 H-NMR spectroscopy. In the trinuclear Cu II -Ni II -Cu II metal complexes, the Ni II ion centered into the main oxime core by the coordination of the imino groups while the two Cu II ions coordinate dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10-phenanthroline, 2,2′-bipyridine, and 4,4′-bipyridine. The ligand and their mono and trinuclear metal complexes were characterized by elemental analyses, FT-IR, UV-Vis, 1 H and 13 C-NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra and X-ray powder techniques. The cyclic voltammetric results show that the cathodic peak potential of [Ni(L) 2 (BPh 2 ) 2 ] shifted toward more negative value compared to that of [Ni(LH) 2 ], probably due to a decreasing effect of back donation of metal-oxime moieties as a result of the BPh + 2 -bridged complex formation. Also, the formation of the trinuclear Cu II -Ni II -Cu II metal complexes caused considerable changes on the CV behaviour of mononuclear [Ni(LH) 2 ] (1) complex. The spectroelectrochemical study of [Ni(L) 2 (BPh 2 ) 2 ] (2) showed distinctive spectral changes that the intensity of the band (λ = at 364 nm, assigned to n → π* transitions) decreased and a new broad band in low intensity about 460 nm appeared as a result of the reduction of the nickel centered in the oxime core.
Inorganic Chemistry, 1992
mononuclear complexes that we have isolated as tetra-and pentahydrate sodium salts, respectively. The synthesis of M2L complexes was carried out in the light of the respective distribution diagrams based on fitted equilibrium constants (Figures 4 and 5). In order to obtain single crystals of such species, aqueous solutions of copper(I1) nitrate (nickel(I1) nitrate) and H4L in a 2: 1 molar ratio were prepared a t p H = 3. In the case of copper(II), the slow polymerization of Cu(H2L) leads to the insoluble polymeric complex 1. Nevertheless, Cu2-L.6H20 can be isolated as a powder in weakly acidic aqueous solutions. The nonpolymerization of the Ni(H2L) species allows in this case the formation of single crystals of the insoluble complex 2 in nearly neutral aqueous solutions. Conclusions. The versatility of N,N'-disubstituted oxamides has allowed the synthesis of mono-, di-, and polynuclear complexes. Strong antiferromagnetic coupling is observed in the poxamidato polynuclear compounds. This work shows how one must be careful when using the n21J1 values to estimate the magnitude of the exchange coupling in binuclear nickel(I1) complexes from the known values for the corresponding copper(I1) complexes through a given bridge. Although nickel(II)-oxamide complexes are usually diamagnetic, paramagnetic nickel(11) species can be obtained by tuning the strength of the ligand field using as tools appropriate N-substituted derivatives and angular strain. Finally, this report provides a new example of complementarity between solution and solid-state studies, showing how solution data can orientate the synthetic work in order to obtain the desired products. Acknowledgment. This work was partially suppprted by the Comisidn Interministerial de Ciencia y Tecnologia (Proyecto PB88-0490) and the Programa de Acciones Integradas Hispano-Francesas. R.R. acknowledges the Conselleria de Cultura, Educacid i C i h c i a de la Generalitat Valenciana for a grant.
Synthesis and characterization of (μ-oxalato) copper(II) and nickel(II) complexes
Polyhedron, 1998
Four new binuclear complexes of the type [(Cu(L)x)2ox](CIO4)2 (L = 1,3-diaminopropane (l,3-pn), x = 1.5 (1) ; L = 1,3-diaminopropane, x = 1 (2) ; L = N-(2-aminoethyl)-l,3-propanediamine (ept), x = 1 (3)) or [(Ni(L)2)2ox](C104)2 (L = 1,2-diaminopropane (1,2-pn) (4)) have been prepared and studied by elemental analysis, IR and electronic spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between five-coordinate (N302) Cu(II) (compounds 1 and 3), four coordinate (N202) Cu(II) (2) and sixcoordinate (N402) Ni(II) (4). Magnetochemical measurements (72-300 K) show and are antiferromagnetic (J = -254 and -33 cm T respectively (H = -JStS2)).
Homo-and heterotrinuclear complexes [LNi{M(L n)} 2 ](ClO 4) 2 ÁH 2 O involving Ni II M II 2 nonlinear cores (M = Ni, Cu, and Pd) (1–6) have been synthesized by a single-pot reaction when the oximato metal complexes [ML n (H 2 O)]ClO 4 (HL n are tridentate oxime ligands), prepared in situ in methanol are allowed to react with the precursor nickel(II) complex [LNi(H 2 O) 2 ] (H 2 L = N,N 0-dimethyl-N,N 0-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine). Single crystal X-ray diffraction analysis, and ESI-MS spectroscopy have been used to establish their identities which involve an octahedral Ni(II) site flunked by two metal-oximate moieties, each in a square planar environment. The electronic and molecular structures of these compounds are interesting due to a synergistic bonding mechanism operative through the deprotonated oxime and the phenolate oxygen atoms via the metal centers. Thus the weak spin-forbidden 3 A 2 ? 1 E transition (e, 4–8 mol À1 cm 2), characteristic of the octahedral Ni(II) center in Ni(II)–Ni(II) 2 (1, 2) and Ni(II)–Pd(II) 2 complexes (5, 6), gains intensity by ca. 25-fold in the spin-coupled Ni(II)–Cu(II) 2 complexes (3, 4) in which the metal centers are connected antiferromagnetically through a moderately strong coupling (J Cu-Ni /k B = À119.6(6) K). In the presence of excess pyridine (5 Â 10 À2 M), the trinickel compound (1) in acetonitrile displays a pair of quasi-reversible oxidations at E 1/2 = 0.48 and 0.69 V (vs. Ag/AgCl reference at a high scan speed, 1000–3000 mVs À1) due to Ni(II/III) oxidations at the square planar nickel sites. Coordinated oxime helps in stabilizing these Ni centers in +3 oxidation state in the timescale of cyclic voltammetry possibly through the formation of octahedral geometry with the added pyridine as axial ligands. In the cathodic range, all the three Ni centers undergo Ni(II/I) reductions at E 1/2 = À1.17, À1.35 and À1.62 V, the most cathodic one being due to the octahedral site.
Copper(II) and Nickel(II) Complexes of Dianionic and Tetraanionic Dinucleating Macrocycles
Inorganic Chemistry, 1998
With nickel(II) or copper(II) acetate, 2,6-bis(acetoximato)-4-methylphenol (H 2 Damox) and 2,6-bis(acetoximato)-4-tert-butylphenol (H 2 Dabox) afford molecular dinuclear complexes [Cu 2 (Damox) 2 ] (1), [Ni 2 (Damox) 2 (MeOH) 2 ]‚ MeOH (2), [Cu 2 (Dabox) 2 ] (5) and [Ni 2 (Dabox) 2 (H 2 O) 2 ] (6). Salts of the macrocyclic tetraimine copper chelates from diacetylcresol with 1,3-diaminopropane and 1,4-diaminobutane, [Cu 2 (Dampn)] 2+ and [Cu 2 (Dambn)] 2+ , were also examined. Pyridine solutions of 2 yielded pink crystals of [Ni 2 (Damox) 2 (Py) 4 ]‚(Py) 2 (3a), which effloresce pyridine to form [Ni 2 (Damox) 2 (Py) 2 ]‚Py (3). The pseudomacrocyclic complexes 1, 5, and 6 react with BF 3 ‚Et 2 O to form BF 2-bridged macrocyclic complexes [Cu 2 (Damfb)] (4), [Cu 2 (Dabfb)]‚H 2 O (7), and [Ni 2 (Dabfb)] (8). Crystals of [Ni 2 (Damox) 2 (Py) 4 ]‚(Py) 2 (3a) are monoclinic (space group P2 1 /n), with a) 13.297(5) Å, b) 11.240-(5) Å, c) 17.396(6) Å,) 109.03°, V) 2458(3) Å 3 , Z) 2, R) 0.050, and R w) 0.052. The [Ni 2 (Dabfb] (8) crystals are orthorhombic (space group Pnma), with a) 11.558(6) Å, b) 17.200(5) Å, c) 16.058(2) Å, V) 3192(3) Å 3 , Z) 4, R) 0.057, and R w) 0.057. The saddle-shaped molecules of 8 contain low-spin Ni(II). The copper(II) centers in 1, 5, 6, etc., are strongly antiferromagnetically coupled with-2J values in the range 550-800 cm-1. The nickel(II) centers in 2 and 3 are weakly (-2J) 3.2 cm-1) or moderately (-2J) 19.5 cm-1) antiferromagnetically coupled, whereas 6 shows a moderate ferromagnetic interaction with-2J)-5.1 cm-1. All the complexes are electrochemically reducible in two 1-electron steps. In CH 3 CN, the mixed-valence complexes [Cu 2 (Dampn)] + and [Cu 2 (Dambn)] + are valence-localized. The nature of the carbon monoxide interactions with the M(I) centers is clearest for [Cu 2 (Dambn)] +/0 , which in dimethylformamide solution binds two molecules of CO in a cooperative fashion.