Ugo Caruso

Thermotropic Mesomorphism in Some Cu(II) and Pd(II) Metallorganic Complexes

Abstract The synthesis and liquid crystal properties of some bis(N-p-(n-alkoxy)phenyl, p-(n-alkoxy)salicylaldiminato)copper(II), of a homologous series of bis(N-p-(n-alkanoyloxy)phenyl, p-(n-alkanoyloxy)salicylaldiminato)copper(II), and of some corresponding palladium(II) complexes are reported. All of the compounds examined exhibit enantiotropic smectic mesomorphism, predominantly of the C type. Palladium(II) complexes are mesomorphic up to higher temperatures than the copper(II) homologues.

Nematic and smectic mesophases in a new series of Cu(II) organometallic complexes

Abstract The synthesis and the phase behaviour of a homologous series of copper, bis[N-[[4-[4-(alkoxy)benzoyloxy],2-hydroxyphenyl]methylene]-methanamino] complexes is reported. They all exhibit thermotropic mesomorphism. The thermal stability range of the mesophase decreases slightly with increasing length of the alkoxy terminals. With the onset of smectic mesomorphism, for alkoxy groups containing ten carbon atoms, the stability interval of the nematic phase decreases progressively so that the compound containing 14 carbon atoms in the alkoxy terminal chains exhibits only smectic mesomorphism. Optical texture analysis suggests the smectic C nature of the phase in all cases. The enthalpies for the liquid crystal-isotropic transition have been measured and they are comparatively low. Remarkably low values have also been measured for the melting enthalpies of the smectogenic members of the series. These are associated with solid phase polymorphism which is discussed briefly.

New NLO active cyclopalladated chromophores in main-chain polymers

Abstract Four new OH-functionalized orthopalladated complexes bearing an electron-donor and an acceptor group in a trans -like arrangement with respect to the metal have been prepared and characterized. The ligands are Schiff bases, bound as C,N- or N,O-chelating moieties. Four new polyesters were obtained by polycondensation from the monomeric complexes and pentyloxyterephthaloyl chloride. Two “model” complexes, each one related to one monomer, were also synthetized, in order to obtain further and more detailed characterization data, and in particular to perform measurements of μβ .

Nematic and smectic mesophases in a new series of Cu(II) metallorganic complexes. II

Abstract The synthesis and phase behaviour of a set of copper, bis-[N-[[4-[4-(tetrade-cyloxy)benzoyloxy],2-hydroxyphenyl]methylene]-alkanimino] complexes (referred to as 14-mNCu where m = 2–14 is the number of carbon atoms in the alkanamino group) is reported. With the single exception of the complex formed with the ethanamine, they show liquid crystal properties, either nematic only (m = 3–9) or smectic only (m = 15) or both of them (m = 10–14). Smectic mesomorphism is of the C type in all cases. The smectic interlayer spacing has been measured for compounds with m = 14 and 15 by X-ray diffraction. For both compounds it is significantly shorter than that found previously for m = 1. This should indicate that, in spite of the smectic phase homology, some substantial change in the molecular packing has occurred. Most compounds exhibit solid phase polymorphism, which is discussed briefly.

The liquid-crystalline properties of bis[N-[[4-[4-(alkoxy)benzoyloxy]2-hydroxyphenyl]methylene]alkanamino] complexes of Cu(II), Pd(II) and Ni(II). A general view

Abstract The thermotropic liquid-crystalline phase behaviour of a homologous set of bis[N-[[4-[4-(alkoxy)benzoyloxy]2-hydroxyphenyl]methylene]alkanamino] copper(II) complexes is examined. New data are reported and taken into account in addition to those previously reported in this Journal. The influence of alkoxy and alkanamine groups on the nature and stability of the mesophase is underlined. As a general trend, with some notable exception, smectic (C type) mesomorphism is favoured by longer alkoxy and alkanamine chains. Data concerning some Pd(II) and Ni(II) homologous complexes are also reported. The mesophase stability (nematic phase) is higher for palladium and nickel complexes than for the copper containing homologues.

Segmented liquid crystalline polyesters with allyl group as lateral substituent

The synthesis and a partial characterization of segmented liquid crystalline polymers with 3,3′-diallyl-4,4′-dihydroxybiphenyl unit in the rigid moiety is reported. The general formula of polymers is [-p-C6H4-COO-p-C6H3(R)-p-C6H3(R)-OOC-p-C6H4-O-(CH2)nO-]x, with n = 6, 8, 10, 12, and R = CH2CHCH2. All polymers have nematic liquid-crystalline behavior. At room temperature, annealed fiber samples of polymers show a complex polymorphism. Three phases have been isolated with very large unit cells accommodating 6 or 12 chains. The projection of the molecular packing in a plane perpendicular to the c axis is characterized by the organization of chains in a two-dimensional hexagonal or quasi-hexagonal array.

Synthesis and characterisation of main-chain oligomeric cyclopalladated azobenzene complexes

Abstract In this paper we report the synthesis of main-chain oligomeric cyclopalladated azobenzene complexes. The approach we followed was focused on the synthesis of difunctional azo-ligands substituted properly with terminal polymerisable OH groups, synthesis of cyclopalladated monomers and polycondensation reaction with acid chlorides as comonomers. In this way, using the interfacial method, two soluble cyclopalladated oligomers P1 and P2 were synthesised.

Synthesis and Antimicrobial Studies of New Antibacterial Azo-Compounds Active against Staphylococcus aureus and Listeria monocytogenes

Some novel (phenyl-diazenyl)phenols (4a–m) were designed and synthesized to be evaluated for their antibacterial activity. Starting from an active previously-synthesized azobenzene chosen as lead compound, we introduced some modifications and optimization of the structure, in order to improve solubility and drug conveyance. Structures of all newly-synthesized compounds were confirmed by 1H nuclear magnetic resonance (NMR), mass spectrometry, and UV-Vis spectroscopy. Antibacterial activity of the new compounds was tested with the dilution method against the bacteria strains Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa PAO1. All the compounds were selectively active against Gram-positive bacteria. In particular, compounds 4d, 4h, and 4i showed the highest activity against S. aureus and Listeria monocytogenes, reaching remarkable MIC100 values of 4 μg/mL and 8 μg/mL. The relationship between antimicrobial activity and compound structure has suggested that the presence of hydroxyl groups seems to be essential for antimicrobial activity of phenolic compounds.

Main chain liquid crystalline polymers with laterally linked organometallic mesogens

The synthesis and characterization of the phase behaviour of a homologous set of polymers of 1,m-diamino-n-alkanes with bis[4-(4-alkoxybenzoyloxy)-2-hydroxybenzaldheyde]copper(II) is reported. The structural peculiarity of these polymers, which is indicated in the title, stems from the presence of metal-complexed salicylideneaminato segments connected via the nitrogen atoms. Calorimetric analysis, polarizing optical microscopy, X-ray diffraction and dynamic viscosity measurements indicate the occurrence of nematic mesomorphism for all the polymers-including two structural analogues containing Ni(II) or Pd(II) in place of Cu(II).

A real-time tripodal colorimetric/fluorescence sensor for multiple target metal ions

Abstract In this work we report on the synthesis of a pyridyl/phenolic/benzothiazole functionalized colorimetric receptor (BPAP) that can selectively recognise Fe(III) and Fe(II) ions in aqueous medium with visible, naked eye colour changes. Moreover, BPAP behaves as a ‘turn-on’ fluorescent chemosensor, showing an excellent sensitivity towards Zn2+ and Cd2+ cations in water by exhibiting fluorometric change. BPAP exhibited a visible detection limit of 5.5 μM and 2.5 μM for Fe3+ and Fe2+, respectively, and a fluorometric selectivity towards Zn2+ and Cd2+ ions with lower detection limits of 205 nM and 642 nM. To understand the mode of binding to the sensor, both the nude sensor and the Zn-complex were isolated and characterized by X-ray crystallography. In Zn-BPAP, the ligand acts as neutral tridentate through Npyridine, Namine and Namide donor atoms. The N atom of benzothiazole group and the OH group of the phenole unit are not coordinated. Computational DFT study was performed on the free ligand BPAP and complex with Zn2+ to investigate the interaction site, to calculate the energies of the frontier molecular orbitals and to corroborate some of the experimental results.