Gian Paolo Suranna

Hydrogen‐Bonded Semiconducting Pigments for Air‐Stable Field‐Effect Transistors

Extensive intramolecular π-conjugation is considered to be requisite in the design of organic semiconductors. Here, two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored. These molecules afford intermolecular π-stacking reinforced by hydrogen-bonding bridges. Air-stable organic field effect transistors are reported that support mobilities up to 1.5 cm(2)/Vs with T80 lifetimes comparable with the most stable reported organic semiconducting materials.

“Darker-than-Black” PbS Quantum Dots: Enhancing Optical Absorption of Colloidal Semiconductor Nanocrystals via Short Conjugated Ligands

Colloidal quantum dots (QDs) stand among the most attractive light-harvesting materials to be exploited for solution-processed optoelectronic applications. To this aim, quantitative replacement of the bulky electrically insulating ligands at the QD surface coming from the synthetic procedure is mandatory. Here we present a conceptually novel approach to design light-harvesting nanomaterials demonstrating that QD surface modification with suitable short conjugated organic molecules permits us to drastically enhance light absorption of QDs, while preserving good long-term colloidal stability. Indeed, rational design of the pendant and anchoring moieties, which constitute the replacing ligand framework leads to a broadband increase of the optical absorbance larger than 300% for colloidal PbS QDs also at high energies (>3.1 eV), which could not be predicted by using formalisms derived from effective medium theory. We attribute such a drastic absorbance increase to ground-state ligand/QD orbital mixing, as inferred by density functional theory calculations; in addition, our findings suggest that the optical band gap reduction commonly observed for PbS QD solids treated with thiol-terminating ligands can be prevalently ascribed to 3p orbitals localized on anchoring sulfur atoms, which mix with the highest occupied states of the QDs. More broadly, we provide evidence that organic ligands and inorganic cores are inherently electronically coupled materials thus yielding peculiar chemical species (the colloidal QDs themselves), which display arising (opto)electronic properties that cannot be merely described as the sum of those of the ligand and core components.

Synthesis, characterisation and catalytic activity of Pd(II) and Ni(II) complexes with new cyclic α-diphenylphosphino-ketoimines. Crystal structure of 2,6-diisopropyl-N-(2-diphenylphosphino-cyclopentylidene)aniline and of 2,6-diisopropyl-N-(2-diphenylphosphino-cyclohexylidene)aniline

Abstract New cyclic α-diphenylphosphino-ketoimines have been synthesised by deprotonation of the corresponding imine and subsequent reaction with chlorodiphenylphosphine. The crystal structures of two of these compounds containing a cyclopentylidene and cyclohexylidene backbone are discussed. Reaction of these bidentate phosphorus–nitrogen (P∧N) ligands with (cod)Pd(CH3)Cl leads to neutral complexes of the general formula (P∧N)Pd(CH3)Cl which have been reacted with AgSbF6 to yield cationic complexes of formula [(P∧N)Pd(CH3)(NCCH3)]SbF6. Reaction of these ligands with (1,2-dimethoxyethane)NiBr2 yields neutral nickel(II) complexes that have been characterised by IR and elemental analysis. Cationic Pd(II) complexes as well as MAO-activated neutral nickel(II) complexes have been used as ethylene oligomerisation catalysts. The cationic palladium(II) complexes show a marked pressure dependence of TOF, with α-olefin fraction and Schulz-Flory α-values explainable in the light of the accepted mechanism for analogous complexes. By increasing the steric bulkiness of the substituent on the imine, or by using ligands with cyclohexylidene or cycloheptylidene backbone instead of cyclopentylidene, a drop in catalytic activity is observed. Nickel(II) complexes of the title ligands activated with MAO permit to confirm the latter conclusions. In comparison with palladium their use brings to comparable linearities but higher oligomerisation grades as well as α-olefin fraction. Cationic palladium(II) complexes are also active in the propene and 1-butene oligomerisation.

Hydrogenation reactions catalysed by a supported palladium complex

Abstract The catalytic activity of the cross-linked polymer obtained by reaction of Pd(AAEMA) 2 [HAAEMA=2-(acetoacetoxy)ethyl methacrylate] and suitable acrylates as comonomers and cross-linkers was investigated in the hydrogenation reactions of substrates such as olefins, aromatic and unsaturated aldehydes, unsaturated ketones and nitrocompounds. The polymer-supported palladium was found to be active and recyclable without loss of metal.

Aerobic oxidation of aldehydes, ketones, sulfides, alcohols and alkanes catalysed by polymerizable, β-ketoesterate complexes of iron(III), nickel(II) and cobalt(II)

Abstract The oxidation of aldehydes, ketones, sulfides, alcohols and alkanes is achieved by using a soluble β-ketoesterate complex of iron (III), nickel (II) or cobalt (II) in the presence of a branched aldehyde and molecular oxygen (or air) at room temperature and atmospheric pressure (Mukaiyamas conditions).

Aerobic oxidations of unsaturated substrates under mukaiyama's conditions: The role of the metal and of the sacrificial aldehyde

Abstract Aerobic epoxidation of unsaturated substrates has been achieved under Mukaiyamas conditions (atmospheric pressure of dioxygen, in the presence of an excess of sacrificial aldehyde) with or without metal catalyst. The influence of light in non-catalysed reactions and the possible role of the aldehyde and of the metal complex in catalysed reactions are discussed. Two mechanistic pathways are proposed for Co(II) and Fe(III) [Ni(II)] catalytic centres.

Synthesis and catalytic activity of allyl, methallyl and methyl complexes of nickel(II) and palladium(II) with biphosphine monoxide ligands: oligomerization of ethylene and copolymerization of ethylene and carbon monoxide

Abstract The syntheses of new cationic nickel complexes {[η 3 -methallyl]Ni[κ 2 P,O-Ph 2 P(X)P(O)Ph 2 ]}SbF 6 , ( 1 )–( 2 ) [X=( o -C 6 H 4 ) ( 1 ), (NH), ( 2 )] have been accomplished. The complexes oligomerize ethylene to linear α-olefins with selectivities as high as 89%. A dependence of oligomerization grade and activity on backbone geometry was shown. New cationic allyl and methyl complexes of palladium(II) [(CH 3 CN)(Me)Pd(κ 2 P,O–Ar 2 P(CH 2 ) n P(O)Ar 2 )]X [ n =1–3, X=BF 4 , Ar=C 6 H 5 ( 18 – 20 )] [ n =1, X=SbF 6 , Ar= p -tolyl ( 23 ); n =1 or 2, X=SbF 6 , Ar=C 6 H 5 ( 21 ) or ( 22 )]; [(η 3 -C 3 H 5 )Pd(κ 2 P,O-Ph 2 P(CH 2 ) n P(O)Ph 2 )]X, [ n =2, X=triflate ( 10 ), tosylate ( 13 ); n =3, X=triflate ( 11 ), tosylate ( 14 )], [(η 3 -C 3 H 5 )]Pd(κ 2 P,O-Ar 2 P(CH 2 ) n P(O)Ar 2 )]X, [ n =1, X=SbF 6 , Ar= p -tolyl ( 17 ); n =2, X=SbF 6 Ar=C 6 H 5 ( 16 )] have been synthesized in good yields. These complexes have been used in the catalytic oligomerization of ethylene, and in the catalytic alternating copolymerization of ethylene and carbon monoxide, to yield polyketones.

A Polymer-Supported β-Ketoesterate Complex of Palladium as an Efficient, Phosphane-Free, Air-Stable, Recyclable Catalyst for the Heck Reaction

The coupling between aryl iodides and bromides with olefins (Heck reaction) has been studied with a polymer-supported palladium catalyst in the presence of sodium or potassium acetate. The reactions can be performed in air without any activating phosphorus ligands and with non dried solvents. Under suitable conditions the catalyst, which exhibits high activity and selectivity, is recyclable several times with negligible leaching of metal. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Polymerization of phenylacetylene and of p-tolylacetylene catalyzed by β-dioxygenato rhodium(I) complexes in homogeneous and heterogeneous phase

AbstractThe catalytic polymerization of phenylacetylene and p-tolylacetylene under homogeneous and heterogeneous condi-tions is described. The catalysts used are either (cod)Rh(AAEMA) [cod: 1,5-cyclooctadiene (cod), AAEMA − : deproto-nated form of 2-(acetoacetoxy)ethylmethacrylate] or the supported metal complex obtained by thermal copolymerizationof (cod)Rh(AAEMA) with suitable comonomers and cross-linkers. Complexes of general formula (diene)Rh(acac) [diene:2,5-norbornadiene (nbd) or 1,5-cyclooctadiene (cod)] have also been used for comparison. High yields in poly(arylacetylene)are achieved in the homogeneous phase for both substrates using THF as solvent at room temperature even in the absenceof any co-catalyst. The use of the supported rhodium(I) catalyst facilitates the polymerization of arylacetylenes yielding, inthe case of poly(phenylacetylene) (PPA), a polymer having high stereoregularity and higher molecular weight respect to thatobtained in homogeneous phase. A new correlation between IR data and the cis-percentage of PPA is proposed and discussed.© 2002 Elsevier Science B.V. All rights reserved.

Homogeneous and heterogeneous catalytic oxidation of benzylic and secondary alcohols with a metal dioxygenato complex in the presence of 2-methylpropanal and dioxygen

Abstract The oxidation of benzylic and secondary alcohols under homogeneous conditions was achieved at 40°C using molecular oxygen as the oxidant in the presence of excess 2-methylpropanal and catalytic amount of Co(acac)2. The oxidation reactions were also carried out with a heterogeneous analogue of Co(acac)2 revealing that the supported cobalt polymer acts as an active and reusable catalyst.