Non-Linear Optical Properties of Biexciton in Ellipsoidal Quantum Dot.

We have presented a theoretical investigation of exciton and biexciton states for the ground and excited levels in a strongly oblate ellipsoidal quantum dot made from GaAs. The variational trial wave functions for the ground and excited states of the exciton and biexciton are constructed on the base of one-particle wave functions. The energies for the ground and excited levels, depending on the ellipsoidal quantum dot's geometrical parameters, are depicted in the framework of the variational method.

Synthesis and Investigation of Electro-Optical Properties of H-Shape Dibenzofulvene Derivatives.

We have synthetized two classes of dibenzofulvene-arylamino derivatives with an H-shape design, for a total of six different molecules. The molecular structures consist of two D-A-D units connected by a thiophene or bitiophene bridge, using diarylamino substituents as donor groups anchored to the 2,7- (Group A) and 3,6- (Group B) positions of the dibenzofulvene backbone. The donor units and the thiophene or bithiophene bridges were used as chemico-structural tools to modulate electro-optical and morphological-electrical properties.

Dinuclear gold(I) complexes with -phosphanyl, N-heterocyclic carbene ligands: synthetic strategies, luminescence properties and anticancer activity.

A small library of dinuclear gold(I) complexes with the title ligands has been prepared, encompassing neutral, mono- and dicationic complexes. The luminescence properties of the complexes in the solid state have been evaluated, and it turns out that neutral and monocationic complexes not presenting a rigid metallamacrocyclic structure can exhibit rather strong emissions that extend towards the red region of the visible spectrum. The anticancer activity of the complexes has been also preliminarly evaluated; cytotoxicity seems to correlate with complex lipophilicity, whereas selectivity towards cancer cells can be apparently enhanced upon a judicious choice of the ligands.

Exploiting Photo- and Electroluminescence Properties of FIrpic Organic Crystals.

In this work, we investigate the optical and structural properties of the well-known triplet emitter bis(4',6'-difluorophenylpyridinato)-iridium(III) picolinate (FIrpic), showing that its ability to pack in two different ordered crystal structures promotes attractive photophysical properties that are useful for solid-state lighting applications. This approach allows the detrimental effects of the nonradiative pathways on the luminescence performance in highly concentrated organic active materials to be weakened. The remarkable electro-optical behavior of sky-blue phosphorescent organic light-emitting diodes incorporating crystal domains of FIrpic, dispersed into an appropriate matrix as an active layer, has also been reported as well as the X-ray diffraction, nuclear magnetic resonance, electro-ionization mass spectrometry, and scanning electron microscopy analyses of the crystalline samples.

Metal complexes with di(N-heterocyclic carbene) ligands bearing a rigid ortho-, meta or para-phenylene bridge.

Three novel dinuclear bis-dicarbene silver(i) complexes of general formula [Ag2(MeIm-phenylene-MeIm)2](PF6)2 (Im = imidazol-2-ylidene) were synthesized. The corresponding copper(i) and gold(i) complexes were obtained by transmetalation of the di(N-heterocyclic carbene) ligand from the silver(i) species, and both coordination geometry and stoichiometry are maintained for all three group 11 metals as expected. The photophysical properties of the Ag(i) and Au(i) complexes were also investigated and discussed; in particular the most strongly emitting complex was also studied via DFT calculations.

Imaging, photophysical properties and DFT calculations of manganese blue (barium manganate(VI) sulphate)--a modern pigment.

Manganese blue is a synthetic barium manganate(VI) sulphate compound that was produced from 1935 to the 1990s and was used both as a blue pigment in works of art and by conservators in the restoration of paintings. The photophysical properties of the compound are described as well as the setup needed to record the spatial distribution of the pigment in works of art.

A colour tunable microcavity by weak-to-strong coupling regime transition through a light-switchable material.

An organic based microcavity showing fully reversible colour tunability has been achieved for the first time. The emission output changes according to the modulation from pure photonic to polaritonic resonant modes through UV irradiation of the light-switchable matrix.

Charged bis-cyclometalated iridium(III) complexes with carbene-based ancillary ligands.

Charged cyclometalated (C(^)N) iridium(III) complexes with carbene-based ancillary ligands are a promising family of deep-blue phosphorescent compounds. Their emission properties are controlled primarily by the main C(^)N ligands, in contrast to the classical design of charged complexes where N(^)N ancillary ligands with low-energy π* orbitals, such as 2,2'-bipyridine, are generally used for this purpose. Herein we report two series of charged iridium complexes with various carbene-based ancillary ligands.

Dinuclear gold(I) complexes with propylene bridged N-heterocyclic dicarbene ligands: synthesis, structures, and trends in reactivities and properties.

Four novel dinuclear N-heterocyclic dicarbene gold(I) complexes with a propylene linker between the carbene moieties have been synthesized and their luminescence and electrochemical properties, together with their reactivity towards bromine oxidative addition, have been screened. All the complexes emit in the solid state in the blue-green spectral range (400-500 nm) with appreciable intensities (Φ(em) up to ≈10%). In cyclic voltammetry, the Au(I)/Au(0) peak splits at low temperature into two separate peaks relative to the couples Au(I)-Au(I)/Au(I)-Au(0) and Au(I)-Au(0)/Au(0)-Au(0), thus indicating the presence of an Au···Au interaction in the dinuclear complex.

Polymorphism, fluorescence, and optoelectronic properties of a borazine derivative.

We have prepared a new borazine derivative that bears mesityl substituents at the boron centers and displays exceptional chemical stability. Detailed crystallographic and solid-state fluorescence characterizations revealed the existence of several polymorphs, each of which showed different emission profiles. In particular, a bathochromic shift is observed when going from the lower- to the higher-density crystal.

Tuning photoinduced processes of covalently bound isoalloxazine and anthraquinone bichromophores.

We present here the synthesis of several new isoalloxazine cyclophanes containing electroactive anthraquinones linked by aliphatic chains of different lengths. Such structural changes provide different interchromophoric orientations leading to the tuning of the rate of the photoinduced electron transfer process from the anthraquinone unit towards the isoalloxazine singlet excited state. Molecular modelling studies were undertaken in order to determine the minimal energy of the proposed structures using Monte Carlo calculations (Amber, Macromodel v.

Capturing the geometry of the emissive state of a Cu(I) red emitter through strong intramolecular stacking forces.

Condensation of ethylenediamine with fluorenone produces a diimine with two terminal fluorophores and a flexible central backbone, N,N'-bis-fluoren-9-ylidene-ethane-1,2-diamine (flen). The diimine reacts with [Cu(MeCN)(4)]BF(4) or CuI to produce a homoleptic compound of the stoichiometry [Cu(flen)(2)]BF(4) or [Cu(flen)(2)][CuI(2)] respectively. Both complexes emit in the red part of the spectrum, with a maximum around 720 nm and excited state lifetime of 0.

A stable and strongly luminescent dinuclear Cu(I) helical complex prepared from 2-diphenylphosphino-6-methylpyridine.

Treatment of 2-diphenylphosphino-6-methylpyridine (dpPyMe) with Cu(CH(3)CN)(4)BF(4) afforded the stable dinuclear Cu(I) complex [Cu(2)(μ-dpPyMe)(3)(CH(3)CN)](BF(4))(2). This compound is a weak emitter in solution, however a remarkably high emission quantum yield (46%) has been found in a rigid matrix at room temperature.

Synthesis and photoluminescence properties of rhenium(I) complexes based on 2,2':6',2''-terpyridine derivatives with hole-transporting units.

Based on 2,2′:6′,2′′-terpyridine ligands (L1), five terpyridine derivatives, namely 4′-carbazol-9-yl-2,2′:6′,2′′-terpyridine (L2), 4′-diphenylamino-2,2′:6′,2′′-terpyridine (L3), 4′-bis(4-tert-butylphenyl)amino-2,2′:6′,2′′-terpyridine (L4), 4′-[naphthalen-1-yl-(phenyl)amino]-2,2′:6′,2′′-terpyridine (L5), 4′-[naphthalen-2-yl(phenyl)amino]-2,2′:6′,2′′-terpyridine (L6) and their corresponding Re(I) complexes ReL(n)(CO)3Cl (n = 1–6) have been synthesized and characterized by elemental analysis and 1H NMR spectroscopy. The X-ray crystal structure of ReL3(CO)3Cl has also been obtained. The luminescence spectra of ReL2(CO)3Cl–ReL5(CO)3Cl, obtained in CH2Cl2 solution at room temperature, show strong dπ (Re) → π* (diimine) MLCT character (λ(max) 600 nm) and a small red shift relative to ReL1(CO)3Cl.

New tetrazole-based Cu(I) homo- and heteroleptic complexes with various P^P ligands: synthesis, characterization, redox and photophysical properties.

Four Cu(I) complexes with general formulas [Cu(N^N)(2)][BF(4)] and [(P^P)Cu(N^N)][BF(4)] were prepared, where N^N stands for 2-(2-tert-butyl-2H-tetrazol-5-yl)pyridine and P^P is a chelating diphosphine, namely bis-(diphenylphosphino)methane (dppm), bis-(diphenylphosphino)ethane (dppe) or bis[2-(diphenylphosphino)phenyl]ether (POP). In an acetonitrile medium, the Electro-Spray Ionization Mass Spectrometry (ESI-MS) determination provided the preliminary evidence for the occurrence of the dppm-containing complex as a mixture of a cationic mononuclear [Cu(N^N)(dppm)](+) species and a bis-cationic dinuclear [Cu(2)(N^N)(2)(dppm)(2)](2+)-type compound. Definitive evidence of peculiar structural features came from X-ray crystallography, which showed both the dppm- and, unexpectedly, the dppe-based heteroleptic compounds to crystallize as diphosphine-bridged Cu(I) dimers, unlike [Cu(N^N)(2)](+) and [(POP)Cu(N^N)](+) which are mononuclear species.

Luminescent ionic transition-metal complexes for light-emitting electrochemical cells.

Higher efficiency in the end-use of energy requires substantial progress in lighting concepts. All the technologies under development are based on solid-state electroluminescent materials and belong to the general area of solid-state lighting (SSL). The two main technologies being developed in SSL are light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), but in recent years, light-emitting electrochemical cells (LECs) have emerged as an alternative option.

Bright blue phosphorescence from cationic bis-cyclometalated iridium(III) isocyanide complexes.

We report new bis-cyclometalated cationic iridium(III) complexes [(C(^)N)(2)Ir(CN-tert-Bu)(2)](CF(3)SO(3)) that have tert-butyl isocyanides as neutral auxiliary ligands and 2-phenylpyridine or 2-(4'-fluorophenyl)-R-pyridines (where R is 4-methoxy, 4-tert-butyl, or5-trifluoromethyl) as C(^)N ligands. The complexes are white or pale yellow solids that show irreversible reduction and oxidation processes and have a large electrochemical gap of 3.58-3.

Blue-emitting dinuclear N-heterocyclic dicarbene gold(I) complex featuring a nearly unit quantum yield.

Dinuclear N-heterocyclic dicarbene gold(I) complexes of general formula [Au(2)(RIm-Y-ImR)(2)](PF(6))(2) (R = Me, Cy; Y = (CH(2))(1-4), o-xylylene, m-xylylene) have been synthesized and screened for their luminescence properties. All the complexes are weakly emissive in solution whereas in the solid state some of them show significant luminescence intensities. In particular, crystals or powders of the complex with R = Me, Y = (CH(2))(3) exhibit an intense blue emission (λ(max) = 450 nm) with a high quantum yield (Φ(em) = 0.

Influence of halogen atoms on a homologous series of bis-cyclometalated iridium(III) complexes.

A series of homologous bis-cyclometalated iridium(III) complexes Ir(2,4-di-X-phenyl-pyridine)(2)(picolinate) (X = H, F, Cl, Br) HIrPic, FIrPic, ClIrPic, and BrIrPic has been synthesized and characterized by NMR, X-ray crystallography, UV-vis absorption and emission spectroscopy, and electrochemical methods. The addition of halogen substituents results in the emission being localized on the main cyclometalated ligand. In addition, halogen substitution induces a blue shift of the emission maxima, especially in the case of the fluoro-based analogue but less pronounced for chlorine and bromine substituents.

Synthesis and photophysical characterization of highly luminescent silica films doped with substituted 2-hydroxyphthalamide (IAM) terbium complexes.

Innovative Tb(3+) antenna complexes employing two different substituted 2-hydroxyphthalamide ligands (HxOH-IAM and bis-HxOH-IAM) acting simultaneously as coordinating sites and light collector units have been synthesized and successively anchored in silica layers by the sol-gel technique. The complexes show remarkable photoluminescence (PL) quantum yields in methanol solution, as high as 0.30 and 0.

Photophysical properties of charged cyclometalated Ir(III) complexes: a joint theoretical and experimental study.

The photophysical properties of a series of charged biscyclometalated [Ir(ppy)(2)(N^N)](1+) complexes, where ppyH is 2-phenylpyridine and N^N is 2,2'-bipyridine (bpy), 6-phenyl-2,2'-bipyridine (pbpy), and 6,6'-diphenyl-2,2'-bipyridine (dpbpy) for complexes 1, 2, and 3, respectively, have been investigated in detail. The photoluminescence performance in solution decreases from 1 to 3 upon attachment of phenyl groups to the ancillary ligand. The absorption spectra recorded over time suggest that complex 3 is less stable compared to complexes 1 and 2 likely due to a nucleophilic-assisted ancillary ligand-exchange reaction.