Preparation, spectroscopic and structural study of copper(II) complexes derived from bulky pyridine ligands

Three different binuclear tetracarboxylato-bridged copper(II) complexes supported by bulky pyridines ligands [Cu(m-MeCO2)2(dPy)]2 (dPy = 3-phenylpyridine (1), 2-benzylpyridine (2) and 4-acetylpyridine (3)) have been synthesised. These compounds were obtained from reaction of [Cu(MeCO2)2(H2O)]2 with pyridine-derived ligands in methanol at room temperature. All compounds were fully characterized by analytical and spectroscopic methods. The molecular structures were determined by X-ray diffraction analysis. All compounds consist of binuclear units where both Cu(II) atoms are linked by four syn-syn carboxylates bridges, showing a paddle-wheel unit, and exhibit interesting intermolecular interactions in the outer coordination sphere

Cocrystals Based on 4,4'-bipyridine: Influence of Crystal Packing on Melting Point

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4'-bipyridine (4,4'-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4'-bipy molar ratios, (HPip)(4,4'-bipy) (1) and (HCinn)2(4,4'-bipy) (2). The melting point (m.p.) of these cocrystals have been measured and a remarkable difference (DT 78 C) between them was observed. Moreover, the two cocrystals have been characterized by powder X-ray diffraction (PXRD), elemental analysis (EA), FTIR-ATR, 1H NMR spectroscopies, and single-crystal X-ray diffraction. The study of their structural packings via Hirshfeld surface analysis and energy frameworks revealed the important contribution of the pi..pi and C-H...pi interactions to the formation of different structural packing motifs, this being the main reason for the difference of m.p. between them. Moreover, it has been observed that 1 and 2 presented the same packing motifs as the crystal structure of their corresponding carboxylic acids, but 1 and 2 showed lower m.p. than those of the carboxylic acids, which could be related to the lower strength of the acid-pyridine heterosynthons respect to the acid-acid homosynthons in the crystal structures

Solvent-controlled formation of monomeric and dimeric species containing Cu(II) acetate and 4-phenylpyridine

Three copper(II) acetate complexes with 4-phenylpyridine (4-Phpy), namely [Cu(MeCO2)2(4- Phpy)2(H2O)2] (1), [Cu(MeCO2)2(4-Phpy)2(H2O)1.5] (2) and [Cu(MeCO2)2(4-Phpy)]2 (3), were synthesized and characterized by analytical and spectroscopic methods. Experimental conditions as solvent or temperature determine the species obtained. Crystal and molecular structure of 2 was determined by Xray diffraction. Compound 2 presents a singular structure, containing two crystallographic independent mononuclear units [Cu(MeCO2)2(4-Phpy)2(H2O)2] (2A) and [Cu(MeCO2)2(4-Phpy)2(H2O)] (2B) in its unit cell and each of these forms an independent 1-D chain through H-bonding

Synthesis and characterization of Pd(II), Pt(II), Cu(I), Ag(I) and Cu(II) complexes with N,O-hybrid pyrazole ligand

The coordination behavior of N,O-hybrid pyrazole-based metal-organic frameworks are described. 2- (3,5-Pyridyl-1H-pyrazol-1-yl)ethanol (L) and its Pd(II), Pt(II), Cu(I), Ag(I) and Cu(II) complexes with different anions have been synthesized and characterized by elemental analysis, conductivity, mass spectrometry, IR, 1H, 13C{1H} and 195Pt{1H} NMR spectroscopies. Complex 1 was also characterized by single crystal X-ray diffraction. For complex 7 has also been possible to perform the UV-Vis and magnetic susceptibility measurements. All complexes are monomers, except the complexes obtained by reaction of the ligand (L) with M(MeCO2)2 (M = Pd(II), Pt(II)) or CuBr2, which are dimers

Mononuclear and binuclear copper(II) bis(1,3-benzodioxole-5-carboxylate) adducts with bulky pyridines

Copper(II) bis(1,3-benzodioxole-5-carboxylate) adducts with bulky pyridines have been prepared from the reaction of copper(II) acetate with 1,3-benzodioxole-5-carboxylic acid (piperonylic acid, HPip) and an excess of pyridine derivatives (3-phenylpyridine, 3-Phpy, 4-phenylpyridine, 4-Phpy, or 4-benzylpyridine, 4-Bzpy). Using 3-Phpy or 4-Bzpy binuclear paddle wheel compounds ([Cu(μ-Pip)2(3-Phpy)]2 (1) and [Cu(μ-Pip)2(4-Bzpy)]2 (3), and mononuclear complexes [Cu(μ-Pip)2(3-Phpy)2(H2O)] (2) and {[Cu(Pip)2(4-Bzpy)2]}{[Cu(Pip)2(4-Bzpy)2](HPip)}·{4A}{4B} have been isolated. Mononuclear 2 can also be produced from 1 in presence of an excess of 3-Phpy, while low thermal treatment of 2 at 70 °C, in absence of solvent, reverts to the formation of 1. On the other hand, 4 presents a singular structure that contains two independent mononuclear units {4A} and {4B}. Working with 4-Phpy yields crystalline binuclear [Cu(μ-Pip)(Pip)(4-Phpy)2]2·4CH3OH (5). In this complex only half of the carboxylate ligands bridge copper atoms, being one of the rare examples of this flat core. Its crystal structure contains a significant fraction of volume filled with methanol that is partly lost simply by exposing the solid to air. However, this process is related to an irreversible structure collapse, showing that the intermolecular interactions after methanol removal are not enough to support a porous structure

New N-pyrazole, P-phosphine hybrid ligands and their reactivity towards Pd(II): X-ray crystal structures of complexes with [PdCl2(N,P)] core

Two new N-pyrazole, P-phosphine hybrids ligands: 1-[2-(diphenylphosphanyl)methyl]-3,5-dimethylpyrazole (LP1) and 1-[2-(diphenylphosphanyl)propyl]-3,5-dimethylpyrazole (LP3) are presented. The reaction of these two ligands and two other ligands reported in the literature: 1-[2-(diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole (LP2) and 1-[2-(diphenylphosphanyl)ethyl]-3,5-diphenylpyrazole (LP4) with [PdCl2(CH3CN)2] yield [PdCl2(LP)] (LP = LP1 (1), LP2 (2), LP3 (3) and LP4 (4)) complexes. All complexes are fully characterised by analytical and spectroscopic methods and the resolution of the crystal structure of complexes 2 and 3 by single crystal X-ray diffraction is also presented. In these complexes the ligands are coordinated to Pd(II) via κ2(N,P) forming metallocycles of six (2) and seven (3) members and finish their coordination with two cis-chlorine atoms. Finally, complex 2 is studied in the palladium-catalysed C-C coupling reaction, being active even for aryl chlorides substrates

ZnII Complexes Based on Hybrid N-Pyrazole, N′-imine Ligands: Synthesis, X-Ray Crystal Structure, NMR Characterisation, and 3D Supramolecular Properties

The present report is on the synthesis of two new 3-imine-3,5-dimethylpyrazole ligands, N-[3-(3,5-dimethyl-1H-pyrazol- 1-yl)propylidene]ethylamine (L1) and N-[3-(3,5-dimethyl-1H-pyrazol-1-yl)propylidene]propylamine (L2). These ligands form molecular complexes with the formula [ZnCl2(L)] (L¼L1 (1) and L2 (2)) when the reacting with ZnCl2 in a metal (M)/ligand (L) ratio of 1 : 1. These new ZnII complexes have been characterised by elemental analyses, conductivity measurements, mass spectrometry, and infrared, 1H and 13C{1H} NMR spectroscopy techniques. The two crystalline structures of complexes 1 and 2 have been solved by X-ray diffraction methods. Finally, we have studied the self-assembly three-dimensional supramolecular structure through different intra- and intermolecular contacts. The application of these ZnII complexes in supramolecular crystal engineering is interesting due to (1) the easy preparation and the high efficiency of this system and (2) the different bonding properties of the heteroatoms (N-pyrazole vs N-imine) present in the structure of the ligands

Synthesis, crystal structure and magnetic properties of a Cu(II) paddle-wheel complex with mixed bridges

The synthesis and characterization of a mixed carboxylate paddle-wheel copper complex, with formula [Cu(μ- Pip)(μ-MeCO2)(MeOH)]2 (Pip = piperonylate or 1,3-benzodioxole-5-carboxylate and MeCO2 = acetate), is here reported. The described compound is a binuclear complex, each pair of similar carboxylate ligands occupyingmutually trans bridging positions,while the methanol occupies the apical positions. The dimers are arranged into 2D layers in the bc plane through a network of O-H⋯O hydrogen bonds established between themethanol and the acetate ligand. Magnetic studies showed a strong antiferromagnetic Cu⋯Cu interaction (J = −308 cm−1), in agreement with the presence of four μ-κO-κO′ carboxylates bridging the metallic centers in the binuclear complex

Modulating p-hydroxycinnamate behavior as a ditopic linker or photoacid in copperth) complexes with an auxiliary pyridine ligand

The reaction of copper(II) acetate monohydrate with p-hydroxycinnamic acid (HpOHcinn) and different pyridine derivatives (4-tert-butylpyridine, 4-tBupy; 4-acetylpyridine, 4-Acpy; 3-phenylpyridine, 3-Phpy; 4-phenylpyridine, 4-Phpy) was essayed in methanol solvent at room temperature. The crystal structures of the resulting compounds were elucidated. Their analysis shows that the choice of pyridine ligands determines different coordination modes of the pOHcinn ligand and the Cu(II) coordination, nuclearity and geometry. The pOHcinn acts as a monodentate carboxylate ligand in combination with 4-tBupy or 4-Phpy, yielding monomers and dimers, associated by hydrogen bonds into supramolecular networks in which the phenol group plays a key role. Conversely, in combination with 4-Acpy or 3-Phpy, the phenol group coordinates directly to the Cu(II), acting as a ditopic ligand and yielding 2D coordination polymers. The compound containing 3-Phpy shows interesting MeOH-H2O reversible exchange behavior. Not only has the pyridine auxiliary ligand had a tremendous effect on the coordination mode of pOHcinn, but also its reactivity is influenced. Particularly, in the case of the compound containing 4-Phpy, it undergoes a photoinduced process, in which the phenol group deprotonates and coordinates to Cu(II) as a phenoxy ligand. This yields a coordination polymer in which two different dimers alternate, bridged by the resulting pOcinn ligand. The magneto-structural correlation of this compound is also discussed

Diverse Structures and Dimensionalities in Zn(II), Cd(II), and Hg(II) Metal Complexes with Piperonylic Acid

Reaction of M(MeCO2)2 (M = Zn(II), Cd(II), and Hg(II)) with 1,3-benzodioxole-5-carboxylic acid (HPip) in methanol (MeOH) yields four piperonylate compounds, one of Zn(II) ([Zn(Pip)2(H2O)2] (1c)), two of Cd(II) ([Cd(μ-Pip)2(H2O)]n (2) and [Cd3(μ-Pip)6(MeOH)2]n (3)), and one of Hg(II) ([Hg(μ-Pip)2]n (4)). The obtention of compounds 1c and 4 was independent of the M/L ratio. These four compounds were characterized by analytical and spectroscopic techniques. In addition, the thermal stability of 1c, 2, and 4 has been studied, and the structure of all the complexes has been determined by the single crystal X-ray diffraction method. The Zn(II) compound displayed a monomeric structure, while Cd(II) and Hg(II) complexes exhibited three polymeric arrays. The Zn(II) (1c) and Hg(II) (4) centers are four- and eight-coordinated in a tetrahedral or squareantiprism geometry, respectively. Furthermore, the Cd(II) ions are either six- (2) or six- and seven- (3) coordinated in a octahedral or both octahedral and pentagonal bipyramid geometries, respectively. In these compounds, the Pip ligand presents different coordination modes: μ1-η1 (1c); μ2-η1:η1 and μ2-η2:η1 (2); μ2-η1:η1, μ2-η2:η1 and μ3-η2:η1:η1 (3); μ1-η2 and μ2-η2:η1 (4). The extended structures were also analyzed. Their photoluminescence properties have been examined, and the quantum yields have been calculated