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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.

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 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.

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...

Highly fluorescent materials have been prepared by incorporation of a zinc complex in mesoporous silica thin films with ordered pore structure. The zinc complex has been introduced into the mesoporous materials via impregnation in an ethanol solution. The incorporation into the films has been monitored by UV–Vis, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. After 18 h of immersion in the doping solution the films showed strong blue emission, increase in the refractive index. Leaching experiments performed by immersing the samples in ethanol or tetrahydrofuran have shown that the chromophore is retained in the porous matrix.

Three tetranuclear zinc(II) complexes of the general formula [ Zn 4 ( μ 3 -OH ) 2 ( LR N,N, O 1 – 3 ) 4 ( LR N,N 1 – 3 ) 2 ] (1–3) were formed from the reaction of ZnCl2 with 2 equiv. of the respective 2-pyridyl ketone oximes, HLR1−3 (R1–3 = H, Ph and Py). The synthesis and the characterization (elemental analysis, IR, 1H NMR and UV–Vis) are described. Complexes 2 and 3 were structurally characterized by single-crystal X-ray crystallography, revealing new examples of anti 12-metallocrown-4 complexes where anions such as hydroxyl groups are encapsulated into the cavity of the tetranuclear cluster.

2-Benzoylpyridine and 2-acetylpyridine N-methyl-N-phenylhydrazones (HL1 and HL2) in cyclopalladation reactions with Pd-3(OAc)(6) behave as N(py)N(im)C tridentate ligands and form the neutral mononuclear complexes [Pd(k(3)-N,N,C-L-1,L-2)(k(1)-OAc)] (1 and 2). The labile OAc ligand can be replaced by pyridine (py) and, in the presence of NH4PF6, a compound of the general formula [Pd(k(3)-N,N,C-L-1,L-2)(py)]PF6 (3 and 4) can be obtained. Reacting 1 or 2 with the poly(4-vinylpyridine) polymer (PVP, (M) over bar (w) = 160000) adducts of the general formula x[Pd(k(3)-N,N,C-L-1,L-2)(PF6)]center dot y[PVP] gives (5a-c and 6a-c, a-c: x/y = 80/20, 50150, 25/75 w/w) containing the laterally appended cyclopalladated 'Pd(k(3)-N,N,C-L-1,L-2)' fragments. These metallorganic polymers show high glass transition temperatures, high thermal stability and good solubility, and are optimal for obtaining transparent thin films by the spin coating method. (c) 2007 Elsevier B.V. All rights reserved.

A new red emitting ( λ em = 610 nm) discotic metal containing liquid crystal, NIRPAC, exhibiting a columnar phase over a broad temperature range (35–173 °C) has been successfully synthesised by an appropriate functionalisation of the cyclopalladated nile red molecular fragment.

The five-membered “(C,N)Pd” metallacycle is a structural feature common to a number of stable photoactive molecular materials. This review is centred on the connection among molecular geometries, types of ligand and photophysical, optical, thermal and electrooptical properties of several series of dinuclear and mononuclear cyclopalladated species, based on HC,N ligands (HC,N = azobenzenes or nitrogen containing heteroaromatic ligands). In the discussion, some representative examples of complexes featuring an useful set of physical properties, were selected and divided into different classes, depending on the nature of the ancillary ligands bonded to the “(C,N)Pd” fragment.

The Nile Red dye, H(NR), forms cyclometalated R2-disubstituted-acetylacetonato square planar Pd(II) complexes (1–3; R = CH3, CF3, C6H5 respectively) whose photophysical properties were tested in cyclohexane, dichloromethane or methanol solutions. In cyclohexane 1–3 emit in the range 580–650 nm with a quantum yield ranging from 0.12 (R = CH3) to 0.50 (R = CF3) and lifetimes between 0.88 and 4.46 ns. These complexes form a new family of notably efficient red emitting organometallic dyes which could be of interest for practical applications.

This communication reports the synthesis of polymetallic species formed by a zinc-tetraphenolporphyrinate core (ZnTPP(OH) 4 , 1 ) and peripheral gallium-quinaldinate ( Q 2 ′ Ga ) fragments. The photophysical analysis of 1 and of the model compound Q 2 ′ GaOPh , R , shows an appreciable overlap between the absorption spectra of 1 and the emission spectra of R , suggesting the presence of a donor–acceptor energy-transfer process. Contrarily, the obtained results indicated that energy transfer does not occur, hence these polymetallic complexes work as double emitting species, for which the colour of luminescence depends on the excitation energy.

The spectroscopic characterization of the metal complexes the 5-amidopyridine-8-hydroxyquinoline (HQ'NHCOC 5 H 4 N) form with M = Be, Zn, Cd, Al, Ga and In is reported. These compounds, M(Q'NHCOC 5 H 4 N) 2 (M = Be, Zn, Cd) and M(Q'NHCOC 5 H 4 N) 3 (M = Al, Ga, In), are highly soluble in DMSO and, in addition, the gallium and indium products dissolve in methyl or ethyl alcohol. These species are very stable in solution and emit in the range 520 (Be)-590 (Ga and In) nm with photoluminescent quantum yields ranging from 0.010 (Al) to 0.001 (In). Processability and color emission suggest that some of these new materials can be of interest for practical applications in optoelectronic devices.

New mononuclear palladium(II) complexes formed by with 2-hydroxy-4-(n-hexyloxybenzylidene)-4′-n-hexyaniline (HL) and 2-phenylpyridine (I), benzo[h]quinoline (II), azobenzene (III), 2-benzoylpyridine (IV) or phenyl-2-pyridylketone-2,4-dinitrophenylhydrazone (V) have been synthesized and characterized by analytical and spectroscopic methods and the single-crystal structures of [(IVa)Pd(L)] and [(Va)Pd(L)] have been established. The spectroscopic and diffractrometric data account for molecular structures wherein the palladium(II) center is part of two chelate rings involving HL and one of the I–V ligands which form a five-member N,C{[(Ia)PdL], [(IIa)Pd(L)] and [(IIIa)Pd(L)]}, a six-member N,C{[(IVa)Pd(L)]}, or a six-member N,N′{[(Va)Pd(L)]} metallacycle. The electronic spectra of [(IIIa)Pd(L)] and [(Va)Pd(L)] show an absorption maxima, at 495 (e∼3×103 M−1 cm−1) and 531 nm (e∼2×104 M−1 cm−1), respectively, which results are significantly affected by the polarity of the solvent. These chromophores should therefore be of interest for the preparation of nonlinear optical materials.

Two new dinuclear Pd(II) cyclometalated complexes of formula [L2Pd2(μ-1,2-sq)(C5H11N)2] (1) and [L2Pd2(μ-1,3-sq)(C5H11N)2]·2[(C5H12N)BF4] (1a) [HL=2,6-dimethylazobenzene], have been synthetized from a reaction of the mononuclear [LPd(acetone)2][BF4] with the piperidinium salt of squaric acid, [C5H12N]2[sq]. The single crystal X-ray analysis of complexes 1 and 1a shows that the sq ligand is found to bridge in both μ-1,2- and μ-1,3-coordination modes. These are the first examples of squarato Pd(II) complexes characterized structurally up to now.

A luminescent zinc complex was successfully incorporated to mesostructured porous titania films through a grafting process. The resulting films show an intense blue-emission increasing with functionalization time. The emission quantum yield of these newly synthesized films was quantitatively and accurately determined by measurements carried by an integrating sphere.

A series of new cationic ortho-metalated Pd(II) complexes of general formula [(C ∧ N)Pd(N ∧ N)]X (HC ∧ N = 2-phenylpyridine, H(PhPy) or benzo[ h ]quinoline, H(BhQ); N ∧ N = ethylenediamine, 2,2′-bipyridine, 1,10-phenanthroline, N , N , N ′, N ′-tetramethylethylenediamine, 4,4′-dimethyl-2,2′-bipyridine, 4,7-dimethyl-1,10-phenanthroline, or 4,4′-dinonyl-2,2′-bipyridine; X = CF 3 SO 3 ) are reported. Photophysical characterization of these species indicates that electronic transitions are prominently cyclometalating ligand-localized in character and nearly unaffected by the polarity of solvent in which the spectra are recorded.

The neutral luminescent tris-cyclometallated 2-phenylpyridine iridium(III) complex, (fac-Ir(ppy)3, [Ir]) following a self-assembling procedure, has been successfully located in the cavities of mesostructured silica materials through a surfactant-mediated process. Two different structure-directing agents, the cationic cetyltrimethyl ammonium bromide (CTAB) and the non-ionic poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) were tested. The structural features induced by the metal complex incorporation can be explained by comparing the newly synthesized hybrid mesostructured materials with the corresponding undoped samples which were similarly prepared. X-Ray powder diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and UV-Vis spectroscopy were used to characterize the investigated materials. Medium-sized spherical particles of 800 nm were obtained using CTAB as a structure-directing agent whereas larger monolithic aggregates with a minimum dimension of 5–8 μm were obtained using P123. The new hybrids showed the typical hexagonal symmetry of analogously prepared materials. Moreover high luminescence quantum yield values were obtained for both hybrids as a result of a very good dispersion of the chromophore in the mesostructured matrices, thereby avoiding dramatic self-quenching phenomena. The approach described in this paper provides a simple synthetic way to prepare new luminescent silica-based materials by the inclusion of neutral metal-containing luminophores into the pores of a mesoporous hosting skeleton.

The first cyclopalladation of 3,5-disubstituted-2-(2′-pyridyl)pyrroles leads to columnar metallomesogens of non-conventional molecular shape.

The synthesis of the first gallium(III)-based liquid crystal has been achieved grafting around the metal centre two chelating 2-methylquinolin-8-olate anions and one monodentate 3,4,5-tris(hexadecyloxy)benzoyloxy ligand, allowing the resulting complex to be a soft luminescent material with the typical high quantum yield of pentacordinated gallium species.

Three organometallic homopolymers and three copolymers have been obtained, by reacting, respectively, cyclopalladated dinuclear complexes with a polymeric backbone, and by radical copolymerization of cyclopalladated acrylic monomers and methyl methacrylate. Taking into account thermal behaviour and solubility, the copolymers, which display good second order nonlinear optical activity, seem to be the most promising for applications within the new metallated macromolecules. Macroscopic nonlinear optical coefficients d 33 have been determined on spin-coated corona-poled thin films by means of Second Harmonic Generation (SHG) measurements at the wavelength of 1064 nm.

Thin film morphology of tris-(8-hydroxyquinolate) aluminium (III) (Al q3 ) and bis-(8-hydroxyquinolate) oxovanadium (IV) (VO q2 ) are compared. Al q3 films deposited onto mica at 300K look almost featureless, but dendrimers or randomly distributed needleshaped crystallites appear as a consequence of crystallization in time. We show that a possible origin of this process is exposure to solvent vapors. On the other hand, VO q2 films retain their textured morphology as thickness increases because of stabilizing intermolecular interactions between vanadyl groups.

The synthesis and a comprehensive experimental study of molecular structure, electrochemical properties, photoconductivity, absorption and emission properties of two homologous series of square planar cyclometallated Pd(II) and Pt(II) complexes are described. In these complexes, a five member (C,N) metallacycle is formed by either azobenzene, 2-phenylpyridine or benzo[h]quinoline, while the ancillary (O,N) ligand required to complete the metal coordination sphere is the Schiff base resulting from the condensation of 4-n-hexylaniline with 2-hydroxy-4-n-hexyloxybenzaldehyde. The study is complemented by Density Functional Theory calculations of molecular structure in the ground state, frontier orbitals distribution and energies. Absorption energies, intensities for the transitions and composition of the excited states are characterized by Time Dependent Density Functional Theory computations. Results show that for these complexes the HOMO is located on the Schiff base and the LUMO on the cyclometalated ligand. As also indicated by spectroscopic and photoconductivity results, the photogeneration of charge carriers might be associated with the spatial separation of HOMO and LUMO, while an additional contribution could derive from a conformational variation in the excited state. The separation of the frontier orbitals on different ligands provides simple synthetic routes towards band-gap tuning and energy matching with other molecular species and electrodes, both important features for several applications of molecular semiconductors. The results of the present investigation suggest that these square planar cyclometalated Pd(II) and Pt(II) complexes actually form a new class of photoconductors.

The newly synthesized complexes formed by cyclopalladated 2-phenylpyridine co-ordinated to 5-substituted-8-hydroxyquinolines, are at room temperature and in fluid solution, luminescent with an absolute photoluminescent quantum yield which depends on the nature of the substituent in position 5.

A number of bis-[5-(4′-R-phenylazo)-8-hydroxy-quinolinato] vanadyl(IV) compounds (R=H, CH 3 , C 2 H 5 , n-C 3 H 7 , n-C 4 H 9 ) have been synthesized and characterized by elemental analyses and IR, EPR and UV–Vis spectroscopies. Data from the above show that they exist in two isomeric solid forms (which were separated for R=C 2 H 5 , n-C 3 H 7 and n-C 4 H 9 ) whose IR and EPR spectra account for isolated molecules (IR: ν (VO)≅961 cm −1 ; EPR: g ≅1.980) or for polymers (IR: ν (VO) about 890 cm −1 ; EPR: g x = g y =1.975(5), g z =1.960(2), A x = A y =40(5), A z =160(3)×10 −4 cm −1 ). The polymeric structure results from intermolecular VO⋯VO interactions.

The tetradentate Schiff base ligands N,N‘-bis[5-(4‘-n-alkyl)phenylazosalicylidene]alkyldiamine H2LN(n) (n = 6, 14), based on 1,2-diaminoethane (N = 1), 1,3-diaminopropane (N = 2), and 1,3-diamino-2,2-dimethylpropane (N = 3) were prepared and characterized. For all the ligands complexes M[LN(n)] (M = Cu, Ni, VO) were readily obtained, which contained two free azo functions. The three series of complexes M[LN(n)] (N = 1−3) were investigated for mesomorphism. This was observed only for N = 1 or 2, in the form of enantiotropic nematic (lower homologues) or smectic (higher homologues) mesophases. The thermal behavior of complexes is discussed on the basis of the structural characteristics of the N,N chelate rings.