Mononuclear Cu(II) complexes of novel salicylidene Schiff bases: synthesis and mesogenic properties

Two new Schiff base ligands 1 and 2 (where 1 = 4-(2-hydroxybenzilidenamino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate, 2 = 4-(4-(decyloxy)-2-hydroxybenziliden amino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate) and their copper (Cu)(II) complexes have been synthesised and characterised. The derivatives were fully characterised structurally, and their mesomorphic behaviour was investigated by polarised optical microscopyand differential scanning calorimetry. The structure of Cu(II) complex having 1 as ligand (3) was determined by X-ray diffraction. The Schiff base ligands exhibit enantiotropic nematic phases, the Cu(II) complex 4 shows monotropic nematic phase behaviour, while compound 3 does not show mesomorphism

Enhanced electroanalytical performance for diclofenac detection through optimizing voltammetric operating conditions

In this study, the influence of the operating conditions of the voltammetric techniques, i.e., differential-pulsed voltammetry (DPV) and square-wave voltammetry (SWV) on the electroanalytical performance of fullerene-carbon nanofiber paste electrode (Full-CNF) for diclofenac (DCF) determination is studied. The optimization of the step potential (SP) and the modulation amplitude (MA) were achieved for DPV, which were further applied for SWV technique. The influence of frequency was tested and the SP of 25 mV, an MA of 200 mV, at the scan rate of 0.1 V·s-1 and frequency of 5 Hz were found as optimized voltammetric operating conditions related to the sensitivity for the determination of DCF in aqueous solution

"Smart" molecular engineering of metallomesogens based on Pt(II) terpyridine coordination complexes

A series of ionic tetracoordinated Pt(II) complexes based on terpyridine ligand were synthesized and characterized. Their chemical structures were engineered by using counterions of different coordination strengths and dimensions, namely non-coordinating BF4, weakly coordinating bulky gallate units, and small and strongly coordinating chlorine (Cl). The complexes containing lipophilic gallate units exhibit low temperature liquid crystalline properties. The mesomorphic properties were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction studies (SWAXS). Photophysical properties were determined in solution and condensed states

Behavior of bipyridine derivative Cu(I) complexes in donor solvents

Cu(I) complexes are known as highly emissive compounds having interesting fluorescence applications[1].Theluminescence is generated by more intense metal to ligand charge transfer (MLCT) electronic transitions for Cu(I), affording longer excited-statelifetimes compared to transient d-d excited state of Cu(II)[2].Herein we report the behavior of two bipyridine derivative Cu(I) complexes containing phenanthroline and biquinoline ligands, respectively, in donor solvents as dimethylsulfoxide and acetonitrile.The Cu(I) phenanthroline complex (1) is unstable in solution,due to oxidation of Cu(I) to Cu(II) in time, accompanied by change in coordination geometry from tetrahedral to trigonal bipyramidal. The Cu(I) biquinoline complex (2) is more stable in donor solvents,the stability increasing at low temperatures with the stabilization of tetragonal geometry of Cu(I).In case of biquinoline ligand, this kind of geometry is stabilized by the bulky aryl substituentsatαposition with respect to the pyridine nitrogen

Emissive Zn(II) metallomesogen based on tridentate terpyridine ligand

A low temperature liquid crystal based on luminescent terpyridine Zn(II) complex is presented. The induction of the mesomorphic properties was achieved using a lipophilic gallate unit as ancillary ligands. The mesomorphic properties were investigated by polarised optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TA) and X-ray scattering (SWAXS) of bulk materials, while the optical properties of the complex were investigated in solution and in condensed liquid crystalline states

Supramolecular "soft" assemblies based on copper (I) coordination complexes

Copper(I) coordination complexes with N^N chelating oligopyridines are valuable candidates for applications in solar energy conversion1 or lightning technologies2 because of their excellent photophysical and photochemical properties and for the low cost and ready availability of the metal. The most attractive systems are based on ligands able to stabilise their tetrahedral geometry (D2d symmetry) and to hinder the flattening distortions which facilitates oxidation to Cu(II) species.3 Herein we present the synthesis and characterisation of new stable Cu(I) complexes based on functionalised 2,2’-biquinoline ligands (Figure 1) that self-assemble into “soft” supramolecular architectures. The stoichiometry and purity of all compounds were determined using elemental analyses, Atomic Absorption, IR and 1H NMR spectroscopies. The functionalisation of the biquinoline ligand with long alkyl chains yielded thermotropic liquid crystalline systems (CuL1_X and CuL2_X), whereas insertion of hydrophilic groups promoted the assembly in water into supramolecular aggregates (CuL3_X). The thermal behaviour of complexes CuLn_X with n = 1 and 2 was investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). UV-Vis studies on CuL3_X evidenced the presence of supramolecular aggregates in water. Stabilization of Cu(I) systems can be also achieved by building supramolecular assemblies and thus blocking the fluxional process towards a distorted “Cu(II)-like” geometry in concentrated solution of complexes

Antioxidant activity and photochromic properties of 2,6-bis (2,4- dihydroxybenzylidene) cyclohexanone

Xanthylium derivatives have attracted considerable interest due to their potential health effects and replacement of synthetic pigments. Moreover, these type of compounds exhibit versatile photochromic properties by switching from a variety of colors when submitted to external stimuli (light, temperature, pH). Generally, all these compounds hold the same xanthylium core and follow the same pH-dependent network of reversible chemical reactions as structurally related families such as flavylium [1-4]. In the present study we focused the attention on the isolation and characterisation of of the species involved in the network of chemical reactions of 2,6-bis(2,4- dihydroxybenzylidene)cyclohexanone. The pH-dependent photochromic behavior of the xanthylium derivative has been investigated. In order to identify the species, the NMR spectra were recorded in acidic and basic media. The antioxidant activity was also determined using DPPH assay [5]. The IC50 values of radical scavenging activity for DPPH were found to be 133.68 μg/mL