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The transitioning of nanotechnology from laboratory to industrial-scale manufacturing poses various challenges in nanoparticle realization. From this perspective, beside the conventional synthetic procedure, based on the seed-mediated growth approach, a reshaping thermal strategy has been investigated to improve the control on gold nanorods aspect ratio, with the aim to point out a potential and encouraging way to better manage the scalability and reproducibility of nanoparticles. For this purpose, nanorods covered with CTAB and nanorods enclosed within a silica shell of tuned thickness have been synthesized and submitted to a post-thermal treatment at various temperatures, up to 300 °C for CTAB recovered gold nanorods (AuNR@CTAB), and up to 500 °C for silica-shell embedded gold nanorods (AuNR@SiO2). For AuNR@CTAB, through accurate temperature control, the longitudinal plasmonic band can be moved very close to the transversal one upon slight reduction of their length. Instead, for AuNR@SiO2, owing to the fully inorganic shell, a higher temperature of treatment can be reached leading to the possibility of reshaping the nanorods into spheres without the observation of any by-products.

Four new Pt(ii) ionic complexes assembled from N-donor ligands and curcumin display interesting antioxidant and antimicrobial properties.

The synthesis and the electrochemical, photophysical, structural, and photoconductive properties of three new heteroleptic Pd(II) complexes with various 3′,5′- disubstituted-2-(2′-pyridil) pyrroles H(N^N) as coordinated ligands are reported. The coordination of the metal center was completed by a functionalized Schiff base H(O^N) used as an ancillary ligand. The [(N^N)Pd(O^N)] complexes showed highly interesting photoconductive properties which have been correlated to their electronic and molecular structures. Theoretical density functional theory (DFT) and time-dependent DFT calculations were performed, and the results were confronted with the organization in crystalline phase, allowing to point out that the photoconductive properties are mainly a consequence of an efficient intramolecular ligand-to-metal charge transfer, combined to the proximity between the central metal and the donor moieties in the solid-state molecular stacks. The reported results confirm that these new Pd(II) complexes form a novel class of organometallic photoconductors with intrinsic characteristics suitable for molecular semiconductors applications., Supported by Ministero dell’Istruzione, dell’Universitàe della Ricerca by the ELIOTROPO.

Heteroleptic Cu(II) compounds containing 4,4′-bis(hydroxymethyl)-2,2′-bipyridine (bipy-OH), tropolonate (Trop) and saccharinate (Sac) have been synthesized and characterized. Different synthetic procedures have been followed for the preparation of a neutral Sac [(bipy-OH)Cu(Trop)Sac], 2, selectively isolated in its blue anhydrous 2a and green mono-hydrated 2b crystalline solid-state forms. The structural characterization of 2 has revealed that the Sac ion is bound to the Cu(II) centre through one of the oxygen atoms of the sulphonyl group, a rare coordination herein proposed to be the thermodynamically preferred one through computational analysis. Investigation to rationalize the hydrogen bonding motifs introduced by the Sac ion in 2 is conducted using hydrogen bond propensity calculations, which are successful in predicting both the formation of its mono-hydrate solid state form and its behaviour in a biological environment. Moreover, both of the solid state forms of 2 are found emissive in the NIR region, in the crystalline solid state at room temperature and in acetonitrile solution at 77 K, with no emission in solution. Finally, computational analysis is carried out showing that 2 when exposed to model molecules mimicking biological targets undergoes ligand exchange reactions with N- and S-donor ligands, with the detached Sac ion interacting via hydrogen bonds with the bipy-OH moiety of the copper derivatives.

Platinum compounds cytotoxicity is strictly related to their ability to be converted into active mono- and di-aquated species and consequently to the replacement of labile ligands by water molecules. This activation process makes the platinum center prone to nucleophilic substitution by DNA purines. In the present work, quantum mechanical density functional theory (DFT) computations and experimental investigations were carried out in order to shed light on the relationship between the internalization, aquation, and DNA binding of two isostructural anionic theranostic complexes previously reported by our group, NBu

The synthesis of a new Cu(II) derivative, [(biq-OH)CuCl2], (4,4-bis(hydroxymethyl)-2,2-biquinoline (biq-OH)), and its reaction with potassium tropolonate (KTrop) is herein reported and the surprising results are discussed. Due to the steric requirements of the biq moiety, the tetrahedral geometry adopted by [(biq-OH)CuCl2] derivative makes it an unstable species, causing an overall rearrangement after reaction with KTrop, with competition between ligands and reduction of the copper ion. Indeed, a heteroleptic Cu(II) complex, [(biq-OH)Cu(Trop)Cl], and a ternary cocrystal, {[Cu(Trop)2][Cu(biq-OH)2]Cl}(biq-OH), in which homoleptic Cu(II) and Cu(I) species coexist, could be isolated from the reaction mixture and characterized. Single crystal X-ray analysis of both the biq-OH ligand and the ternary cocrystal {[Cu(Trop)2][Cu(biq-OH)2]Cl}(biq-OH) are reported and a deep analysis of the intermolecular interactions of their supramolecular assemblies in the solid crystalline state, conducted by Hirshfeld surface and contact enrichment tools, are thus reported.

A series of electropolymerizable cyclometallated IrIII complexes were synthesized and their electrochemical and photophysical properties studied. The triphenylamine electropolymerizable fragment was introduced by using triphenylamine-2-phenylpyridine and, respectively, triphenylamine-benzothiazole as cyclometalated ligands. The coordination sphere was completed by two differently substituted β-ketoiminate ligands deriving from the condensation of acetylacetone or hexafluoroacetylacetone with para-bromoaniline. The influence of the -CH3 /-CF3 substitution to the electrochemical and photophysical properties was investigated. Both complexes with CH3 substituted β-ketoiminate were emissive in solution and in solid state. Highly stable films were electrodeposited onto ITO coated glass substrates. Their emission was quenched by electron trapping within the polymeric network as proven by electrochemical studies. The -CF3 substitution of the β-ketoiminate leads instead to the quenching of the emission and inhibits electropolymerization.

Over the years, the need for the synthesis of biodegradable materials has facilitated the drift of the asphalt industry towards eco-sustainable and cost-effective production of road pavements. The principal additives in the asphalt industry to improve the performance of road pavements and increase its lifespan are majorly rheological modifiers, adhesion promoters and anti-oxidant agents. Rheological modifiers increase physico-chemical properties such as transition temperature of asphalt binder (bitumen), adhesion promoters increase the affinity between binder and stone aggregates while anti-oxidant agents reduce the effects of oxidation caused by exposure to air, water and other natural elements during the production of asphalt pavements. In this study, we tested the effectiveness of a food grade bio-additive on these three aforementioned properties. We also sought to hypothesize the mechanisms by which the additive confers these desired features on bitumen. We present this study to evaluate the effects of turmeric, a food-based additive, on bitumen. The study was conducted through dynamic shear rheology (DSR), atomic force microscopy, scanning electron microscopy (SEM) and boiling test analysis.

Neutral cyclometalated Ir(III) complexes of general formula [Ir(ppy)2(O^O)squi], where ppy = 2-phenylpyridine and (O^O)squi = TBC (tetrabromocatechol) or TCC (tetrachlorocatechol) in their semiquinone (squi) monoanionic redox state, were synthesized by chemically oxidizing the anionic parent complexes NBu4[Ir(ppy)2(O^O)cat], in which (O^O)cat represents the corresponding ancillary dioxolene ligand in its dianionic catecholate (cat) redox state. This chemical oxidation leads to the modification of both the photophysical and the magnetic properties of the complexes. While the NBu4[Ir(ppy)2(O^O)cat] complexes are diamagnetic (D) and yellow-orange solids, the corresponding oxidized complexes [Ir(ppy)2(O^O)squi] display paramagnetic (P) properties and are characterized by a dark-green color. The conversion between the two forms (squi vs. cat) is electrochemically and chemically fully reversible. Indeed, the anionic NBu4[Ir(ppy)2(O^O)cat] complexes are quantitatively restored by chemical reduction of the neutral [Ir(ppy)2(O^O)squi] parents. These complexes therefore represent interesting redox based switches between multi-parameter states since they allow switching from a neutral paramagnetic to an anionic diamagnetic form together with a significant change in chromicity. Taking advantage of the significant color difference between the oxidized and the reduced form, an electrochromic cell was prepared with [Ir(ppy)2(TBC)squi] and its spectroelectrochemical properties are reported.

Ag(I)-containing ethylcellulose (EC) films suitable as antbacterial packaging materials have been prepared and fully characterized. Different preparation methods, including the use of green casting solvents, are proposed. The Ag(I) acylpyrazolonato complexes, [Ag(Qpy,CF3 )(L)], L=benzylimidazole (Bzim) and L=ethylimidazole (EtimH), used as active additives, display different modes of interactions with EC, depending on their structural features. A thorough investigation of the EC liquid-crystalline lyotropic phase and its changes with the introduction of silver additives, has been conducted, revealing either the inclusion of complex molecules into the inner structure of the EC matrix or their dispersion on its surface. Moreover, the bactericidal activity of the prepared Ag(I) films seems to be related to the interaction between silver additives and the polymeric EC matrix. Indeed, the EC-2b films show a particularly good performance even with a low silver content, with a relative bacterial killing of about 100 %. Tests for Ag(I) migration have been performed by using three food stimulants under two assay conditions. Low values of silver release are recorded, particularly at low concentration of silver content, in the case of all new prepared Ag(I) films.

Five- and six-coordinated zinc(II) complexes, [Zn(QR)2(H2O)] (1-2) and [Zn(QR)2(L)] (3-8) (HQR = 4-R(C=O)-5-pyrazolones in general, in detail HQC17, R = -(CH2)16CH3, HQCy, R = -C6H11; L = bipy, tmeda or en;) have been synthesized and characterized by IR, 1H and 13C NMR, UV-visible spectroscopy, elemental analysis, TGA and ESI mass spectrometry. The square pyramidal complex [Zn(QC17)2(H2O)] (1) has been structurally characterized, together with a trans octahedral [Zn(QCy)2(EtOH)2] (2b) species obtained by recrystallization of [Zn(QCy)2(H2O)] (2) from ethanol. Additionally, in both complexes [Zn(QCy)2(bipy)] (4) and [Zn(QC17)2(tmeda)] (5) structurally characterized by single crystal X ray diffraction, the same amount of ? and ? enantiomers are present, with the only difference related to the mutual disposition of the different type of the QR coordinated oxygen atoms. The cytotoxicity of the complexes [Zn(QCy)2(H2O)] (2), [Zn(QCy)2(bipy)] (4) and [Zn(QCy)2(en)] (8) has been evaluated in vitro against MCF-7 human breast cancer cell line in a biohybrid membrane system. Results revealed that zinc complexes possess antiproliferative activity inducing apoptosis by activation of caspase-3 and p-JNK.

The influence of the counterions on the geometry of Cu(I) and Cu(II) unsubstituted phen-based (phen = 1,10-phenanthroline) complexes was investigated. The synthetic strategy used afforded the synthesis of both the tetracoordinated Cu(I) and pentacoordinated Cu(II) species with general formula [(phen)2Cu]+Y− (Y− = ClO4−, I−, SCN− and BF4−) and [(phen)2CuX]+Y− (X = Cl−, I−, NCS−, and Y− = ClO4−, I−, SCN− and BF4−), respectively. The firstly isolated Cu(I) complexes were characterized by IR, 1H NMR and UV-Vis spectroscopies, their proposed structures being confirmed by elemental analysis, atomic absorption spectroscopy (AAS) and thermogravimetric analysis (TGA). The molecular structure of Cu(II) complexes was determined by single crystal X-ray diffraction analysis. While for Cu(I) complexes, the coordinating nature of the counterions seems to have a strong influence (observed in the solid state and concentrated solution) on the flattening distortion (D2d → D2) of the geometry about the Cu(I) ion, in the Cu(II) derivatives, the size, shape, number and type of intermolecular interactions established by the counterions, drive not only the overall cations supramolecular organization, but also the molecular stereochemistry around the Cu(II) ion.

In the present study, the synthesis and properties of a novel water soluble Ir(III) complex of formula [(ppy)2Ir(dpq)]CH3CO2 is described, where ppy is the cyclometalated 2-phenylpyridine ligand and dpq the dipyrido[3,2-f:2′,3′-h]quinoxaline used as ancillary ligand. Own to its specific molecular structure, this complex forms highly ordered supramolecular gels in water on a wide range of concentration, from 3 to 14% w/w. The gel phase shows birefringence under cross polarisers that is completely loss when water is removed, evidence of the formation of a true lyotropic liquid-crystalline gel, without the need of an additional gelator. The gel is macroscopically formed of entangled microfibers that can be seen under optical microscope and that display luminescent properties as observed by confocal microscopy. X-Ray diffraction allowed to resolve the structure of the lyotropic mesophase that is formed by columns of complex cations organised in a tetrahedral manner which are in turn arranged in a larger oblique lattice, hence showing a high degree of order. The photophysical properties of the complex in its different state of matter (solid, gel phase and xerogel) are presented and discussed.

The preparation and characterization of a new metallogelator based on the Ir(III) discrete cyclometallated complex [(ppy)2Ir(bpy)](CH3CH2OCH2CO2) are reported, where H(ppy) is 2-phenylpiridine and bpy is 2,2'-bipyridine, used as ancillary ligand. The compound is able to self-assemble in water in a range of concentrations between 3% and 6 % w/w, creating a luminescent ordered supramolecular gel. The gel and xerogel architectures were investigated through POM, SEM and TEM microscopies coupled with Powder X-Ray Diffraction. The gel supramolecular organization is characterized by columnar tetragonal strands, already present at high dilution conditions, of cations surrounded by counteranions. These strands, in turn, are self-assembled in an oblique columnar cell upon gelification. The xerogel thin films obtained upon complete dehydration maintained the gel supramolecular order and can be used as precursor for the preparation of nanostructured IrO2 thin films.

A nanoplatform for simultaneous cellular imaging, and photodynamic and photothermal therapies has been designed and realized by embedding a purposely synthesized highly luminescent water soluble iridium(III) compound into gold core–silica shell nanoparticles. These multifunctionalities arise mainly from the photophysical properties of the cyclometalated complex: (i) the heavy atom promotes, through excited triplet state formation, energy transfer processes towards molecular oxygen, with the generation of 1O2 (photodynamic effect); (ii) the overlap of the iridium(III) complex emission band with the plasmonic resonance of gold nanostructures allows excitation energy transfer towards the metallic core (photothermal effect); (iii) the remarkable iridium(III) complex luminescence feature, which is preserved despite energy transfer processes, makes the whole system an efficient luminescent bio-probe (imaging). Photophysical and photothermal investigations have been carried out, whereas in vitro photo-cytotoxicity tests have been performed on human glioblastoma cells (U87MG), highlighting significant cancer cell death at a very low photosensitizer concentration (

The focus of this work is pointing out the different behavior of two structurally related Pt

The ability of Nile Red to self-assemble into supramolecular packings on Au(111) was studied using scanning tunneling microscopy and modeled through theoretical semiempirical calculations. At both submonolayer (sub-ML) and ML coverages, two distinct molecular packings, that is, four-leaf clover and dense chain, were observed, both weakly interacting with the underlying metal surface. Theoretical calculations suggested that the dipole moment plays a subtle role in both molecular assemblies, held together by hydrogen bonds between the Nile Red molecules. Furthermore, although both molecular assemblies were observed in as-deposited samples, a mild thermal annealing caused the transition from the four-leaf clover to the dense-chain packing, pointing out the greater stability of the dense-chain configuration. The study further emphasized how the established interactions between the Nile Red molecules are strongly influenced by the surrounding environment.

The modulation of the environment around the “PtI2” molecular fragment in the Pt(IV) cyclometalated complexes [PtI2(ppy) (facac)](1a) and [PtI2(ppy) (acac)] (1b) (Hfacac = hexafluoroacetylacetone; Hacac = acetylacetone) causes competition between halogens in the formation of leading intermolecular interactions. Particularly, the presence of the “organic fluorine” CF3 induces significant structural changes proving the key role that fluorine plays in crystal engineering in metallorganic systems.

The synthesis and photophysical characterization of a new family of luminescent water-soluble ionic iridium(III) complexes of the general formula [(ppy)2Ir(bpy)]X are reported. The Ir(III) complexes incorporate a cyclometalated 2-phenylpyridine (ppy), the ancillary ligand 2,2′-bipyridyl (bpy) and different counterions (X− = EtO−, OH−, EtOCH2CO2−, MeOCH2CO2−). These complexes were obtained starting from the cyclometalated Ir(III) chloro-bridged dimer [(ppy)2Ir(μ-Cl)]2, for the first time synthesized through a new microwave assisted synthetic procedure, and subsequently converted into the corresponding hydroxy-bridged dimer [(ppy)2Ir(μ-OH)]2. The latter was eventually used as a sole reagent for the synthesis of all the reported complexes by simply varying the nature of the reaction solvent from water to alcohols and glycol ethers. This study demonstrates the versatility of the [(ppy)2Ir(μ-OH)]2 complex as a precursor to water soluble ionic Ir(III) complexes. Indeed, [(ppy)2Ir(μ-OH)]2 has shown its peculiar chemical reactivity due to both a strong base character and an unexpected oxidative ability towards the alcoholic function of glycol ethers. All the synthesized complexes exhibit, in water solution, an orange emission centred at 606 nm. Moreover, all complexes display the ability to give rise to gel phases in water upon increasing their concentration, and the photophysical study evidenced the various interactions governing the gelification process. The water-solubility of these new luminescent Ir(III) complexes makes them potentially useful in bio-related systems.

Novel electropolymerizable Ir(III) cyclometallated complexes have been synthesized and characterized. In these complexes the cyclometallated ligands are either 2-phenylpyridineH(PhPy) or benzothiazole-triphenylamineH(BzTh-tpa), while the Ir(III) coordination sphere is completed by a Schiff base substituted with a triphenylamine fragment. A complete electrochemical study has been conducted on all complexes, in order to verify the feasibility of electropolymerization and to elucidate the role of the specific position of the triphenylamine moiety in the molecular structure. Homogeneous thin films of Ir(III) metallopolymers have been successfully obtained through electropolymerization process.

A study on the effect of silica nanoparticles (SNPs) dispersion in bitumen is herein reported. First, the size of the nanoparticles was finely tuned by controlling the experimental conditions during their synthesis, obtaining spherical SNPs with diameter ranging from 95 up to 900 nm. Subsequently, SNPs were embedded with peripheral amine groups by using APTES (3-aminopropyltriethoxysilane) as functionalized agent (NH2@SNP), and ultimately long alkyl chains were grafted by reacting the free amine with an alkylated aldehyde (C14N@SNP). All SNPs (ca. 1 wt%.) were dispersed in bitumen to probe their effect on the rheological properties of bitumen. No significant change in the thermorheological properties of bitumen was observed upon varying the size of the SNPs. Slight improvement was observed when using NH2@SNPs, while the best results were obtained by using C14N@SNPs, showing the crucial role that hydrophobic substituents play in bitumen binders which leads to significant improvements.

The focus of this work is pointing out the different behavior of two structurally related Pt(II) complexes, the anionic cyclometalated NBu4[(Bzq)Pt(Thio)], 1 and the neutral [(Phen)Pt(Thio)], 2, (Bzq = benzo[h]quinoline, Phen = 1,10-phenantroline, Thio = 1,2-benzenedithiolate), on the interaction with human serum albumin (HSA), a key drug-delivery protein in the bloodstream. Being very limited the number of anionic Pt(II) complexes reported to date, this is a pioneering example of report on a protein-ligand interaction involving a negatively charged platinum compound. The study was carried out by using fluorescence spectroscopy, differential scanning calorimetry and molecular docking simulations. The results revealed a strong binding affinity between the anionic compound and the protein, whereas a weak/moderate binding interaction was highlighted for the neutral one. Comparative studies with site specific ligands (warfarin and ibuprofen), allowed us to identify the protein binding sites of the two compounds. The work aims to shed light on the relevance of the charge in designing new drugs with a favorable binding affinity for HSA, which strongly contributes to influence their pharmacological and toxicological profile.

The synthesis, crystal structure and luminescence properties of three neutral heteroleptic cyclometallated Ir(III) complexes of general formula [(ppy) 2 Ir(PyPr-R)] , where Hppy = 2-phenylpyridine and HPyPr-R = 3,5-disubstituted-2-(2′-pyridyl)pyrrole with R = CH 3 ( 1 ), Ph ( 2 ) and CF 3 , ( 3 ), are described. The cyclic voltammetry studies carried out on 1 – 3 showed oxidation potentials consistent with the nature of the - R substituent groups, indicating that the energy of the HOMO level is significantly affected by the overall electronegativity of the PyPr-R ancillary ligand. Single-crystal X-ray-structural determination was carried out in the case of 2 and 3 . While 3 crystallizes in a unique form, two pseudo-polymorphs, a solvated ( 2a ) and non-solvated ( 2b ) specie, have been obtained for compound 2 . The supramolecular assembly of the neutral complexes in their crystalline state is mainly directed by π⋯π stacking ( 2a , 2b ) and C–H⋯π interactions ( 3 ). The photophysical properties of the HPyPr-R ligands and complexes 1 – 3 have been investigated in solution and, for 2a , 2b and 3 , in their solid crystalline state. All complexes show phosphorescence emission in solution, significantly quenched in presence of dioxygen. In the solid crystalline state, the emission maxima of 2a , 2b and 3 show a significant spectral shift with respect to the solution. For complex 3 it was calculated a bathochromic shift of 1178 cm −1 , while the spectral maxima of complexes 2a and 2b are red-shifted of ca . 3150 cm −1 . Moreover, the average emission lifetime of 2a and 2b crystalline samples is one order of magnitude higher with respect to that of 3 (1.64 and 1.55 μs, respectively, versus 0.265 μs). This behaviour accounts for the presence of excimers in the solid sample of 2a and 2b, most likely due to the π⋯π stacking interactions involving the pyridine rings of either the cyclometallated and/or the ancyllary ligands. This type of interaction is absent in 3 , the presence of the C–H⋯π interactions being insufficient to produce photophysically observable effects.

Historically, many useful drugs have been developed from natural sources and their mechanisms of action deeply investigated for therapeutic applications. Recently, the interaction between pharmacologically active biomolecules and transition metal ions has opened the way to the construction of new drugs, where the unique properties of metal complexes are combined with the specific mechanisms of action of the coordinated bioligands of natural extraction. In this context, this perspective summarizes some recent research studies devoted to the development of new metal-based drugs containing Zn(ii) or Cu(ii) metal ions. Both metals have a strong tendency to form highly stable complexes with N,N- and O,O-donor ligands bound through chelation, giving rise, particularly when the bound organic molecules are drug candidates of natural extraction, to drug delivery systems, new biologically active complexes and potential diagnostic agents due to their intrinsic spectroscopic properties.

Two series of novel NBu4+ salts of anionic cyclometallated Pt(ii) complexes were synthesized and fully characterized. These highly luminescent compounds (NBu4[(C^N)Pt(O^N)] and NBu4[(C^N)Pt(O^O)]) are incorporated as testing examples of cyclometallating ligands 2-phenylpyridine (PhPy), 2-(2,4-difluorophenyl)-pyridine (F2PhPy) and 2-thienylpyridine (ThPy), and a benzo[h]quinoline (Bzq) fragment. All complexes display a square-planar coordination sphere, wherein the "(C^N)Pt" fragment is completed either by an O^N orotate (Ort) or an O^O tetrabromocatecholate (Cat) ligand. The HOMO and LUMO levels of all complexes were estimated by cyclic voltammetry and a comprehensive electrochemical and photophysical study was performed. The new complexes are emissive in solution at 298 K and the NBu4[(ThPy)Pt(Ort)] complex displays good photosensitizing properties (Φ = 28% in deaerated solution vs. Φ = 1.4% in the presence of O2). Both series of NBu4[(C^N)Pt(Ort)] and NBu4[(C^N)Pt(Cat)] complexes are highly luminescent in the solid state (emission quantum yields from 10 to 85%). Remarkably, the square-planar Pt(ii) anionic complexes showed an important increase in luminescence quantum yields on changing from the dilute solution to the solid state (the most significant from 0.13% to 85% for the NBu4[(PhPy)Pt(Ort)] complex, an ideal candidate as an active species for LEECs).

The preparation and characterization of a new metallogelator based on the Ir

Four new complexes of general formula [(La)Pd(Qui)] (1), [(Lb)Pd(Acr)] (2), [(La)Pd(Acr)] (3) and [(Lb)Pd(Acr)] (4) containing methyl (1, 3) or phenyl (2, 4) 3,5-disubstituted chelated 2-(2′-pyridyl)pyrrole ligands (HLa,b) have been synthesized and characterized. For comparative purposes, the analogous 2-phenylpyridine (HLc) derivatives, [(Lc)Pd(Qui)] (5) and [(Lc)Pd(Acr)] (6), have also been prepared. Mild synthetic conditions and reduced reaction times can be employed with HLa,b ligands to obtain the products in good yields, proving the higher reactivity of HLa,b compared with HLc in cyclopalladation. Depending on the relative dispositions of the NN/NO (1–4) or CN/NO (5 and 6) chelating rings, all the complexes can in principle exist as two isomers. However, in each case, only one isomer was observed by 1H NMR spectroscopy. The crystal structures of 1, 4, and 5 reveal the presence of different isomers for different complexes, depending on both the cyclometallating and ancillary ligands. The structures of 1–6 allowed us to hypothesize that the ancillary ligand may play a predominant role in the formation of the trans/cis isomers in these systems and that the pyridylpyrrole definitely produces opposite outcomes compared with the 2-phenylpyridine ligand. Finally, the photophysical properties of 1–4 were studied in solution. Although 5 and 6 are emissive, no emission was detected for 1–4 under the same conditions, the emission quenching being most likely caused by the thermal deactivating path of the lowest excited state, which results from a combination of the pyridylpyrrole-localized state with that localized on the NO ligand.

Homogeneous thin films of controlled thickness obtained from cyclometalated complexes of general formula [(C(∧)N)M(O(∧)N)], where M = Pd(II) or Pt(II), H(C(∧)N) = 2-phenylpyridine and, respectively, 2-thienylpyridine and H(O(∧)N) = a triphenylamine functionalized Schiff base, have been deposited by oxidative electropolymerization. The films have been electrochemically and morphologically characterized. The metallopolymeric thin films present stable reversible redox behavior and typical cauliflower-like textures in agreement with a nucleation-growth electropolymerization mechanism. However, the film growth is greatly influenced by the nature of the metal center, with a higher tendency of the Pt complexes to promote the 3D growth. Furthermore, a complete spectroelectrochemical study has been performed on electrodeposited films showing near-IR absorption in the oxidized state, high contrast ratios (up to 65%) and low response times.

Luminescent complexes with general formula [(C^N)2Ir(N^N)]OCOCH3, where C^N = 2-phenylpyridine (ppy) and N^N = 2,2ʹ-bipyridine (bpy), self-assemble into ordered ‘soft’ viscous mesophases of chromonic type. By changing the ancillary ligand with 1,10-phenanthroline (phen), a new mesomorphic complex was obtained. The self-assembly into ordered liquid crystalline phases of chromonic type in water was investigated by comprehensive rheological and photophysical studies. By changing the ancillary ligand bpy with phen, assembly into smaller, more symetric aggregates is favoured, resulting in lower viscosity and more dynamic mesophase.

Three homologous series of luminescent octahedral ionic Ir(III) complexes (1–12) with a dual stereogenic center of general formula Δ,Λ (R,S)[(ppy)2Ir(R-campy)]X, where ppy=2-phenylpyridine, R-campy=2-methyl-5,6,7,8-tetrahydroquinolin-8-amine (Me-campy) or 8-amino-5,6,7,8-tetrahydroquinolines (H-campy) and as counterions X−=Cl− or CH3COO− have been synthesized and characterized. The NMR characterization of each complex highlighted the diastereoisomeric purity and the absolute configuration has been confirmed by Electronic Circular Dichroism spectroscopy. The absorption and the luminescence properties of the compounds in solution and in solid state have been investigated by UV–vis, steady-state emission and time-correlated single-photon counting spectroscopy. The obtained results from the 12 compounds highlight the difficult to correlate photophysical properties in solution to the stereochemistry, while excited states decay studies of the solid state samples indicate a correlation between photophysics and packing mode which is affected by the different stereochemistry.

We present the synthesis and characterization of a series of neutral and cationic Nile Red cyclopalladated complexes, first examples of covalent coordination of Nile Red to a Pd(II) metal centre. The Pd(II) coordination sphere is completed by a series of ancillary substituted ligands (acetylacetonates or bipyridine derivatives) selected in order to tune the photophysical properties and/or to enhance the supramolecular order. Both neutral and cationic columnar rectangular metallomesogens have been obtained. Emission has been observed only for neutral complexes (both in solution and mesophase) but quenched in cationic complexes.

New cationic Ir III materials of general formula [Ir(ppy) 2 (C n -bpy)]PF 6 (H(ppy) = 2-phenylpyridine; C n -bpy = 3,4,5-R-4,4'-benzoyloxymethyl-2,2'-bipyridine ; n = 8, R = OC 8 H 17 ; n = 0, R = H) were synthesised and fully characterised. Both complexes show high phosphorescence quantum yields in their condensed phases. Moreover, the introduction of long alkoxy chains on the bipyridne ligand in [Ir(ppy) 2 (C 8 -bpy)]PF 6 (1) has induced mesomorphism, and consequently a dynamic functional material with properties modulated by external stimuli has been obtained. Starting from the isotropic phase, on slow cooling a crystalline phase characterised by a bright green emission is obtained. However, on fast cooling a kinetically favoured columnar hexagonal mesophase is preferentially formed, which is stable down to room temperature. In this phase, the high luminescence is still maintained, even if a switch to yellow emission colour is observed. Moreover, through spin coating of solutions of 1, it has been possible to obtain its amorphous thin film to accomplish a further shift of the emission wavelength in the orange-red spectral range. A fully reversible colour tuning process by surface stress and heating from the orange-red film to the green crystalline phase, indicative of a mechanochromic behaviour, is also achieved.

A series of tetradentate dimeric salicylaldimine ligands (H2LnRm) with terminal chains of variable length (Rm) and a central flexible (CH2)n spacer (Ln = 10 and 12) was synthesized. For all ligands, according to their rod-like molecular shape, mesomorphism characteristic of calamitic systems (nematic and smectic C phases) is observed. The reaction with ZnII acetate dihydrate afforded a series of ZnLnRm derivatives (1–6) that show mesomorphic behaviour only in the presence of the longest terminal tails (R12). Interestingly, the flexibility of the very long spacer in the central core and the presence of the tetrahedral ZnII centre introduce nonlinearity in the central part of the molecule, responsible for the appearance of an intercalated smectic C mesophase. Moreover, the coordination of the ZnII ion to the salen-like framework induces, in all the corresponding complexes, interesting blue-light-emitting properties at room temperature in dichloromethane solution (EQY in the 19–22 % range at about 450 nm), as well as in the solid (EQY: 9 % at about 450 nm) or, when present, in the mesophase (EQY 8 % at 440 nm).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

4-Hydroxyacridine (HAcr) is an O,N-chelating ligand whose coordination chemistry toward group 13 M(III) ions has received little attention. The molecular structure of HAcr consists of a 2,3-disubstituted-8-hydroxyquinoline; thus, in order to compare 8-hydroxyquinoline (HQ), 2-methyl-8-hydroxyquinoline (HMeQ′), and 2,3-disubstituted-8-hydroxyquinoline (HAcr) for steric and/or electronic influence, HAcr chelating ability toward the Al(III), Ga(III), and In(III) triad has been investigated. Irrespective of the nature of M(III), only complexes containing two equivalents of deprotonated HAcr are obtained. This article describes the synthesis and characterization of different series of bis-chelated pentacoordinated (Acr)2MY (M = Al, Ga, In; Y = Cl, Br, I, NCS, N3) or (Acr)2MZ (M = Ga or In; HZ = C6H5OH, C6H13OC6H4OH, C6H5COOH, or C6H13OC6H4COOH) six-coordinate neutral (Acr)2In(acac) (H(acac) =acetylacetone), or ionic [(Acr)2In(N,N)][CF3SO3] (N,N = 2,2′-bipyridine or 1,10-phenanthroline) complexes. These results...

New luminescent inorganic–organic hybrid materials incorporating the luminescent zinc(II) complex ZnL2 (λem = 457 nm and Φem = 4.4% reference values for ZnL2; HL = chelating ligand resulting from the reaction between salicylaldehyde and 3-aminopropyltriethoxysilane), covalently bonded to different types of mesoporous silica hosts (namely MCM-41, MCM-48 and SBA-15), were prepared via both the methods of grafting post-synthesis (GPS) and one-pot synthesis (OPS). The products obtained, which form the GPS [(GPS)(Zn/MCM-41), (GPS)(Zn/MCM-48), (GPS)(Zn/SBA-15)] and the OPS [(OPS)(Zn/MCM-41), (OPS)(Zn/MCM-48), (OPS)(Zn/SBA-15)] series, contain the ZnL2 guest covalently bonded to the silica framework through silicon–oxygen bonds formed when the silane group is placed at the periphery of the Zn(II) coordination sphere. GPS and OPS materials were characterized by powder X-ray diffraction, N2 adsorption/desorption, thermogravimetric analysis (TGA) and UV/vis spectroscopy. For the new mesoporous materials the emission quantum yield (EQY) was measured by means of an integrating sphere combined with a spectrofluorimeter. The ZnL2 loading (measured by the ZnL2/SiO2 ratio calculated from TGA data) for MCM-41 appears to be independent of the synthesis procedure, whereas, for both MCM-48 and SBA-15, the ZnL2/SiO2 ratio of the materials obtained via OPS is about four times higher than products obtained from GPS. The ZnL2 loaded GPS and OPS series show λem maxima at about 485 and 455 nm, respectively. Moreover, with reference to EQY (GPS)(Zn/SBA-15) and (OPS)(Zn/SBA-15), although featuring ZnL2/SiO2 ratios of 0.13 and 0.45, respectively, they showed similar EQY values: 2% and 5%. On the contrary, (GPS)(Zn/MCM-41) and (OPS)(Zn/MCM-41) which give similar ZnL2/SiO2 ratios (0.09 and 0.14) exhibit very different EQY, i.e. 2% and 22%, respectively.