Syntheses and thermal characterization of the magnesium phthalocyanine complexes with 2-methoxy- and with 2-ethoxyethanol. X-ray structure of (2-ethoxyethanol)magnesium phthalocyanine

The syntheses of the magnesium phthalocyanine complexes with dry 2-methoxy-ethanol and 2-ethoxyethanol have been performed by recrystallization method using both anhydrous MgPc and aquated magnesium phthalocyanine, MgPcH₂O, as a starting material. It has turned out that in the temperature range below ca. 140 °C, the bi-axially ligated complexes are formed, i.e., MgPc(2-methoxyethanol)₂ and MgPc(2-ethoxyethanol)₂ with 4 + 2 coordination of Mg, whereas at higher temperatures, up to about 200 °C, the mono-axially ligated complexes are stable, i.e., MgPc(2-methoxyethanol) and MgPc(2-ethoxyethanol) with 4 + 1 coordination of Mg.The single crystal structure of MgPc(2-ethoxyethanol) complex has been determined. The central Mg atom is displaced towards the hydroxyl group of the ligand by about 0.37 Å from the (N-isoindole)₄ plane of the Pc ring. Hydrogen bonds of the type O-H?N between the hydroxyl groups of 2-ethoxyethanol and one of the azamethine N-atoms of the Pc ring link the molecules related by a centre of symmetry. Such a packing arrangement in the crystal leads to a dimerization with the ligand-to-Pc connections. The syntheses, thermogravimetric results and structure characteristics are compared with the known MgPc complexes with O- and N-donating molecules.     

Preparation, structural, spectroscopic, thermal and DFT characterization of cadmium(II) complexes with quinaldic acid

Cadmium(II) complex with quinaldic acid (quinH), [Cd(quin)₂(H₂O)₂] (1), was prepared by the reaction of cadmium(II) acetate and quinaldic acid in water-ethanol mixture, while another cadmium(II) complex, [Cd(quin)₂(DMSO)₂] (2), was prepared by the recrystallization of 1 in DMSO. Both complexes were characterized by IR spectroscopy and TGA/DTA methods. The crystal structure of 2 was determined by X-ray structure diffraction analysis. Cadmium(II) ion is octahedrally coordinated by two N,O-bidentate quinaldate ligands in equatorial and by two DMSO molecules in axial positions. Only weak intermolecular C-H···O hydrogen bonds and π-π stacking interactions as packing forces are present in the crystal structure of 2. The theoretical investigations included geometry optimizations of both complexes at DFT level (B3LYP and mPW1PW91 functionals) and calculations of vibrational frequencies. Calculated and experimental IR spectra were compared and characteristic bands assigned. The electronic properties of the complexes were investigated by the NBO analysis. Thermogravimetric studies showed the initial loss of two coordinated water molecules in 1 and of DMSO in 2 and then complete decomposition of quinaldate ligands for both 1 and 2.     

An azomethin-zinc complex for organic electroluminescence: Crystal structure, thermal stability and optoelectronic properties

An azomethin-zinc complex, bis[salicylidene(4-dimethylamino)aniline]zinc(II) (Zn(sada)₂) was synthesized and structurally characterized by single-crystal X-ray crystallography. Crystal data for Zn(C₁₅H₁₅N₂O)₂ was determined as follows: space group, triclinic, ; a = 10.2791(9) Å, b = 16.5008(14) Å, c = 17.5984(15) Å, α = 114.830(2)°, β = 96.579(2)°, γ = 97.674(2)°, Z = 4. Through thermal analysis characterization and FT-IR spectra, this complex was proved to have good thermal stability. The vapor-deposited films exhibited uniform and environment-stable morphology. The light emission and charge transporting performance of Zn(sada)₂ in organic light emitting diodes (OLEDs) were investigated preliminarily, and the results indicated the superior electron transporting property of this complex. Compared with the typical bilayer device of N,N′-diphenyl-N,N′-bis(1-naphthyl)-benzidine (NPB)/tris-(8-hydroxyquinoline)aluminum (Alq₃), the device with Zn(sada)₂ as the electron transporting layer exhibited a much lower turn-on voltage of 2.5 V (it is usually 3.5 V for an NPB/Alq₃ device).     

From U(IV) double-decker phthalocyanine with stacked UPc2 sandwiches to unstacked ones

The uranium diphthalocyanine complex with the composition of [UPc₂]·2DBU·(CH₃)₂CO has been obtained by recrystallisation of [UPc₂](I₃)_2/3 in DBU (1,8-diazabicyclo[4.5.0]undec-7-ene) during slow dilution with acetone. The [UPc₂]·2DBU·(CH₃)₂CO complex crystallises in the Pna2₁ space group of the orthorhombic system with four molecules in the unit cell. In contrast to the stacked structure of [UPc₂](I₃)_2/3 the structure of [UPc₂]·2DBU·(CH₃)₂CO contains separated and unstacked UPc₂ sandwiches. The [UPc₂]·2DBU·(CH₃)₂CO complex dissolved in benzene, in 1-choronaphthalene and in DBU has been characterised by the UV-Vis spectroscopy. Some remarks on the stability of the complex in these solutions as well as its transformation to uranium monophthalocyanine have been made.     

Synthesis and structural analysis of copper(II) cysteine complexes

This report describes the synthesis and structural analysis of stable copper(II) cysteine complexes. Pale pink copper(II) cysteine complexes were synthesized in mole ratios of 1:2, 1:4, and 1:6 of copper(II):cysteine in ethanol. Infrared spectroscopy and X-ray absorption spectroscopy confirmed that copper(II) binding occurred via the thiol ligand of cysteine. XANES analysis showed that the oxidation state of copper remained as copper(II) and the local atomic geometry was similar in all of the cysteine complexes. The EXAFS data indicate that the copper(II) cysteine complexes are forming ring type structures with sulfur ligands from the cysteines acting as bridging ligands. X-ray diffraction revealed that the copper(II) cysteine complexes formed monoclinic cells with maximum crystallinity found in the 1:4 copper(II):cysteine complex.     

Synthesis and solid-state structure of magnesium and calcium imidazole complexes

Three octahedral complexes built from N-alkylsubstituted imidazoles and magnesium as well as calcium chloride are reported. The obtained solid-state structures differ significantly from each other, depending on the size of the metal ion and the substituent on the imidazole. A chloro-bridged structure is found in the case of tert-butylimidazole, while for the iso-propylimidazole the calcium ion is coordinated by six imidazoles. For the smaller magnesium cation, we also found a sixfold coordination, but here only three of the iso-propylimidazoles coordinate to the magnesium, the three other positions are taken by water molecules.     

Synthesis, spectroscopic and structural characterization of some novel adducts of copper(II) salts with unidentate nitrogen bases

Syntheses, spectroscopic characterization and single crystal X-ray studies are reported for a number of complexes of copper(II) salts with simple monodentate nitrogen bases. The 1:4 adduct of copper(II) sulfate with 3,5-dimethylpyridine (m₂py) CuSO₄·4m₂py, takes the form [(O₃SO)Cu(m₂py)₄], the Cu-O vector of the square-pyramidal coordination environment being disposed on the 4-axis in tetragonal space group P4/n. The complex CuCO₃·Cu(NCS)₂·4py is a linear polymer, taking the form ?O·Cu(py)₂·O·C{O·Cu(py)₂(NCS)₂}·O·Cu(py)₂? (etc.), all atoms lying in the mirror plane of space group Pnma, excepting the pair of ‘py’ (pyridine) ligands disposed to either side. In Cu(OH)I·3/4I₂·2py·1/2MeCN ≡ [{(py)₂Cu(OH)}₄](I₃)₃I·2MeCN a novel cubanoid tetranuclear cation is found (2-symmetry). The EPR spectra of the above compounds show a trend in the anisotropy of the g-values that correlates well with the crystal structures. Obtained only in small quantities but supported by single crystal X-ray studies are the adduct of Cu(OH)Cl with pyrrolidine (pyrr), Cu(OH)Cl:pyrr (1:3), which takes the centrosymmetric binuclear form [(pyrr)₃Cu(μ-OH)₂Cu(pyrr)₃]Cl₂, the copper atom being disposed in a distorted trigonal bipyramidal array, and the adduct 3CuCl₂·CuO·4quin, [Cu₄Cl₆O(quin)₄]Cl₂, which contains the familiar Cu₄Cl₆O core with monodentate quinuclidine (quin) attached to the copper atoms; this compound crystallizes in the cubic space group .     

Structural preferences and thermal stability of complexes with the exo-bidentate ligand 1,2-bis(2-methylimidazol-1-ylmethyl)benzene

We describe a series of new coordination polymers of Cd(II), Co(II) and Ag(I) with 1,2-bis(2-methylimidazol-1-ylmethyl)benzene. All complexes were characterized by single crystal X-ray diffraction which reveals polymeric bridging of metal centers by the ligand in all cases. The cadmium center in complex 1 has a slightly irregular octahedral geometry involving two Cl⁻ ions and four N atoms from individual ligands, resulting in the formation of undulated (4,4) layers. In complex 2 the cobalt(II) ion is coordinated by two Cl⁻ ions and two N atoms from separate ligands. This yields a slightly irregular tetrahedral coordination environment around the metal center and the formation of a 1D zigzag-chain structure. Each of the three Ag(I) complexes (3-5) forms an infinite 1D chain. These three complexes are similar both in conformation and packing mode despite modification of the counterions. The size of the counterion appears to affect the thermal stabilities of the resulting networks.     

Synthesis and spectral investigation of manganese(II), cadmium(II) and oxovanadium(IV) complexes with 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone): Crystal structure of manganese(II) and cadmium(II) complexes

The chelating behavior of 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone) (H₂dapa) towards manganese(II), cadmium(II) and oxovanadium(IV) ions has been studied by elemental analyses, conductance measurements, magnetic properties and spectral (IR, ¹H NMR, UV-Vis and EPR) studies. The IR spectral studies suggest the pentadentate nature of the ligand with pyridine nitrogen, two azomethine nitrogens and two carbonyl oxygen atoms as the ligating sites. Six coordinate structure for [VO(H₂dapa)]SO₄ · H₂O and seven coordinate structures for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)Cl₂] · H₂O complexes have been proposed. Pentagonal bipyramidal geometry for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)(Cl₂)] · H₂O complexes was confirmed by single crystal analysis. The X-band EPR spectra of the oxovanadium(IV) and manganese(II) complexes in the polycrystalline state at room (300 K) and also at liquid nitrogen temperature (77 K) were recorded and their salient features are reported.     

Synthesis, structural and corrosion inhibition studies on cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, electronic, IR, NMR and ESR spectral techniques. The molecular structures of ligand and its copper(II) complex have been determined by single crystal X-ray diffraction technique. The Cu(II) complex possesses a CuN₂O₂ chromophore with a considerable delocalization of charge. The structure of the complex is stabilized by intermolecular π–π stacking and C–H?π interactions. Hatbh acts as a monobasic bidentate ligand in all the complexes bonding through a deprotonated C–O⁻ and >CN groups. Electronic spectral studies indicate an octahedral geometry for the Ni(II) complex while square planar geometry for the Co(II) and Cu(II) complexes. ESR spectrum of the Cu(II) complex exhibits a square planar geometry in solid and in DMSO solution. The trend g_|| > g_⊥ > 2.0023 indicates the presence of an unpaired electron in the d_x²-y² orbital of Cu(II). The electro-chemical study of Cu(II) complex reveals a metal based reversible redox behavior. The Ni(II) complex shows exothermic multi-step decomposition pattern of the bonded ligand. The ligand and its most of the metal complexes show appreciable corrosion inhibition properties for mild steel in 1 M HCl medium. [Co(atbh)₂] complex exhibited the greatest impact on corrosion inhibition among the other compounds.     

Reaction of bis(bis(trimethylsilyl)amido)mercury(II) with 3,3′-disubstituted binaphthols: Cyclization via an intramolecular electrophilic aromatic substitution reaction

Reaction of the mercury(II) amide Hg[N(SiMe₃)₃]₂ with 3,3′-disubstituted binaphthols (HO)₂C₂₀H₁₀(R)₂-3,3′ (R = SiMe₃, SiMe₂Ph, SiMePh₂, SiPh₃) in a 2:1 stoichiometric ratio furnishes four hexacyclic 1,7-disilylsubstituted derivatives of peri-xanthenoxanthene (PXX). Reaction of these two reagents in a 1:1 ratio results in a mixture of the hexacyclic products as well as the related pentacyclic species which contain one hydroxyl group and only one C-O-C ring fusion. The structures of three of the hexacyclic products (R = SiMe₃, SiMe₂Ph, SiMePh₂) and one of the pentacyclic products (R = SiMe₃) have been obtained. The reaction of Hg[N(SiMe₃)₃]₂ with the 3,3′-disubstituted binaphthols proceeds via an intramolecular electrophilic aromatic substitution reaction and several intermediates in this process have been detected using NMR (¹H and ¹⁹⁹Hg) spectroscopy.     

An improved synthesis, crystal structures, and metallochromism of salts of [Ru(tolyl-terpy)(CN)3]

The previously reported complex [Ru(ttpy)(CN)₃]⁻ [ttpy = 4′(p-tolyl)-2,2′:6′,2″-terpyridine] is conveniently synthesised by reaction of ttpy with Ru(dmso)₄Cl₂ to give [Ru(ttpy)(dmso)Cl₂], which reacts in turn with KCN in aqueous ethanol to afford [Ru(ttpy)(CN)₃]⁻ which was isolated and crystallographically characterised as both its (PPN)⁺ and K⁺ salts. The K⁺ salt contains clusters containing three complex anions and three K⁺ cations connected by end-on and side-on cyanide ligation to the K⁺ ions. The solution speciation behaviour of [Ru(ttpy)(CN)₃]⁻ was investigated with both Zn²⁺ and K⁺ salts in MeCN, a solvent sufficiently non-competitive to allow the added metal cations to associate with the complex anion via the externally-directed cyanide lone pairs. UV-Vis spectroscopic titration of (PPN)[Ru(ttpy)(CN)₃] with Zn(ClO₄)₂ showed a blue shift of 2900 cm⁻¹ in the ¹MLCT absorption manifold due to the ‘metallochromism’ effect; a series of distinct binding events could be discerned corresponding to formation of 4:1, 1:1 and then 1:3 anion:cation adducts, all with high formation constants, as the titration proceeded. In contrast titration of (PPN)[Ru(ttpy)(CN)₃] with the more weakly Lewis-acidic KPF₆ resulted in a much smaller blue-shift of the ¹MLCT absorptions, and the titration data corresponded to formation of 1:1 and then 2:1 cation:anion adducts with weaker stepwise association constants of the order of 10⁴ and then 10³ M⁻¹. Although association of [Ru(ttpy)(CN)₃]⁻ resulted in a blue-shift of the ¹MLCT absorptions, the luminescence was steadily quenched, as raising the ³MLCT level makes radiationless decay via a low-lying ³MC state possible.     

Synthesis, structure and thermal behaviour of two magnesium complexes containing the 1,4-bis(5-tetrazolyl)benzene ligand

The reaction between the 1,4-bis(5-tetrazolyl)benzene ligand (H₂btb) and different magnesium salts allowed the recovery of two different molecular salts, namely [Mg(H₂O)₆](btb) (1) and [Mg(H₂O)₆](Hbtb)₂·2H₂O (2). These crystalline materials were fully characterized by spectroscopic, thermal and diffraction methods. In both cases the octahedrally coordinated hexaaquo Mg(II) ions are linked through several strong H-bond interactions of the OH?N type to the btb anions, completely or partially deprotonated in 1 and 2, respectively. The thermal analysis has established that, in both cases, all water molecules are lost below 200 °C. Interestingly, the process is completely reversible upon exposure to water-saturated atmosphere. Unfortunately, the anhydrous phases are amorphous, and no structural information could be derived form our PD traces, even if a number of partially crystalline intermediates, formed during the dehydration processes, were observed by thermodiffractometric methods.     

Synthesis, crystal structure and EPR of a hydrogen bonded two-dimensional network of Cu(II) complex with N-(2-hydroxybenzyl)-2-amino-1-ethanol

Hsalea (N-(2-hydroxybenzyl)-2-amino-1-ethanol) and its Cu(II) complexes, Cu(salea)₂ (1) and CuH₋₁(salea)·1.5H₂O (2), were prepared and characterized. X-ray structural analyses of 1 show that two amino N and two deprotonated phenoxy O atoms of the two ligands coordinate equatorially to Cu(II). Two alcoholic O atoms coordinate weakly at axial positions. Each molecule utilizes two alcoholic H atoms and two phenoxy O atoms to form hydrogen bonds with four surrounding molecules, leading to a two-dimensional network structure. EPR and electronic spectra of 1 are consistent with the elongated octahedral coordination polyhedron.     

Synthesis, structural, spectroscopic and thermal characterization of cobalt complexes with 3- and 6-methylpicolinic acid. Voltammetric and spectrophotometric study in solution

Cobalt complexes of 3- and 6-methylpicolinic acid, namely [Co(3-Mepic)₃] (1) and [Co(6-Mepic)₂(H₂O)₂] · 2H₂O (2) were prepared and characterized by spectroscopic methods (IR, UV-Vis, NMR), their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA/DTA methods. Square-wave voltammetry showed that on mercury electrode the oxidation of 2 requires higher potential than the oxidation of complex anion [Co(3-Mepic)₃]⁻, the most probable product of the reduction of 1. The reduction of 1 and the oxidation of 2 depend on the kinetics of electron transfer and the electrode material. X-ray structural analysis revealed octahedral coordination polyhedron in both 1 and 2 and the same N,O-chelated coordination mode for both ligands. ¹³C, ¹H and ¹⁵N NMR spectroscopy confirmed that coordination mode of 3-methylpicolinic acid in 1 in DMSO solution. UV-Vis spectrophotometric measurements were used to study the complexation of cobalt with 3- and 6-methylpicolinic acid in aqueous solution and to determine the composition of the formed complexes by Job method of continuous variation. The stoichiometry of the complex with 3-methylpicolinic acid is 2:3, while it is 2:3 and 3:2 for the complex with 6-methylpicolinic acid, indicating the possibility of the formation of more than one complex species.     

Electrochemical synthesis and crystal structures of nickel(II), copper(II), zinc(II) and cadmium(II) complexes with N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine

The electrochemical oxidation of anodic metal (nickel, copper, zinc and cadmium) in acetonitrile solutions containing N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine H₂L and an additional nitrogen coligand, such as 1,10-phenanthroline, yielded mixed complexes of general formula [ML(phen)₂] (M=Ni, Cu, Zn and Cd). The compounds have been characterized by microanalysis, IR and UV-Vis (Ni, Cu complexes) spectroscopy, FAB mass spectrometry, ¹H NMR spectroscopic studies (Zn, Cd complexes) and EPR spectroscopy (Cu and Ni complexes). All compounds have also been characterized by single crystal X-ray diffraction. The molecular structures of these compounds consist of individual monomeric molecules in which the metal atom is in an [MN₆] distorted octahedral environment.     

Palladium(II) complexes of a bis-2-aminobiphenyl N-heterocyclic carbene: Synthesis, structural studies and catalytic activity

A new imidazolinium [(SIBiphen)H](BF₄) was synthesized in three steps from 2-aminobiphenyl. The reaction of the salt with Pd(OAc)₂, NaI and t-BuOK gave a dimeric Pd(II) complex [(SIBiphen)PdI₂]₂, which was analyzed by an X-ray diffraction study. The reaction of [Pd(allyl)Cl]₂, the imidazolinium salt and t-BuOK in THF at −78 °C gave the monomeric Pd complex, in which the N-heterocyclic carbene was bound to the metal centre, as confirmed by a single-crystal X-ray diffraction study. A preliminary catalytic study showed that these new systems were moderately active in the Suzuki-Miyaura coupling of aryl halides.     

Synthesis and structural investigation of vanadocene(IV) complexes of non-linear pseudohalides

Two series of vanadocene complexes of the type (Cp′ = η⁵-C₅H₅, η⁵-C₅H₄Me; X = dicyanamide, tricyanomethanide, dicyanonitrosomethanide) were prepared by the reaction of appropriate vanadocene dichloride complex with alkali salt of non-linear pseudohalide. The bonding mode of pseudohalide ligands was determined by spectroscopic measurements and X-ray diffraction analyses.     

Synthesis, structures and spectroscopic properties of palladium(II) complexes with tridentate piperidyl-containing pincer ligands

A new series of square planar palladium(II) complexes with pincer ligands, pip₂NCN⁻ (pip₂NCNH = 1,3-bis(piperidylmethyl)benzene) and pip₂NNN (2,6-bis(piperidylmethyl)pyridine), has been prepared: Pd(pip₂NCN)X (X = Cl, Br, I), [Pd(pip₂NCN)(L)](BF₄) (L = pyridine, 4-phenylpyridine), and [Pd(pip₂NNN)Cl]Cl. The X-ray crystal structures of Pd(pip₂NCN)Br, [Pd(pip₂NCN)(L)]BF₄, and [Pd(pip₂NNN)Cl]Cl confirm the tridentate coordination geometries of the pincer ligands. For the pip₂NCN⁻ complexes, each piperidyl ring adopts a chair conformation with the metal center at an equatorial position on the N(piperidyl) atom. However, one of the piperidyl groups of Pd(pip₂NNN)Cl⁺ adopts a previously unobserved coordination geometry, effectively placing the metal center at an axial position on the N(piperidyl) atom. ¹H NMR and UV-Vis absorption measurements provide additional insight into the electronic structures of these complexes. The ¹H NMR spectra of Pd(pip₂NCN)X (X = Cl, Br, I) are consistent with deshielding of the pip₂NCN⁻ ligand resonances along the Cl < Br < I series, in opposition to the relative halogen electronegativities. It is suggested that this trend is consistent with decreasing filled/filled repulsions between the dπ orbitals of the metal center and the lone pair orbitals of the halide ligands along this series. Electronic absorption spectra support the notion that ligand-to-metal charge-transfer states are stabilized in these palladium(II) complexes relative to their platinum(II) analogues.     

Syntheses and structures of some adducts of silver(I) oxyanion salts with some 2-N,O-donor-substituted pyridine bases

Syntheses and room-temperature single crystal X-ray structural characterizations are recorded for a variety of silver(I) oxyanion (perchlorate, nitrate and trifluoroacetate (‘tfa’) (increasing basicity)) adducts, AgX, with a number of pyridine (‘py’) bases, L, functionalized in the 2-position with N- or O-donor groups, namely 2-amino-, 2-amino-6-methyl-, 2-aminomethyl-, 2-hydroxy-, 2-methoxy- and 2-acetyl- pyridines, ‘2np’, ‘nmp’, ‘amp’, ‘ohp’, ‘mop’, and ‘acp’. A variety of stoichiometries and associated structural types are defined: [Ag(chelate)₂]X, L/X = amp,acp/ClO₄, [XAg(chelate)₂], L/X = acp/tfa, of 1:2 AgX:L stoichiometry; for 1:1 stoichiometry, although a discrete mononuclear complex [(chelate)Ag(O₂NO)] is defined for AgNO₃: acp (1:1), all others are polymers, successive silver atoms being linked by N,N′-bridging ligands singly (L/X = 2np/ClO₄ (?HAgHTAgTHAgH?), amp/ClO₄, NO₃ (?HTAgHTAg?) (‘H’ ≡ head, ‘T’ = tail)) or pairwise, ?L₂AgX₂AgL₂Ag? (L/X = 2np/tfa, nmp/NO₃). More complex polymeric arrays are found with L/X = ohp/NO₃, tfa, where interaction with the metal takes place via the O-donor only, the py functionality being protonated, and in adducts of more complex stoichiometry AgNO₃:mop (2:3) and AgNO₃:2np (3:4).