Fluorine-induced J-aggregation enhances emissive properties of a new NLO push–pull chromophore

A new fluorinated push–pull chromophore with good second-order NLO properties even in concentrated solution shows solid state intermolecular aryl–fluoroaryl interactions leading to J-aggregates with intense solid state luminescence

An acido-triggered reversible luminescent and nonlinear optical switch based on a substituted styrylpyridine : EFISH measurements as an unusual method to reveal a protonation-deprotonation NLO contrast

Diphenyl-(4-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-phenyl)-amine (DPVPA) constitutes a novel acido-triggered reversible luminescent and nonlinear optical switch. Remarkably, for the first time the Electric-Field Induced Second Harmonic generation (EFISH) technique is used to reveal a protonation-deprotonation NLO contrast

Fluorine-induced J-aggregation enhances emissive properties of a new NLO push-pull chromophore

A new fluorinated push-pull chromophore with good second-order NLO properties even in concentrated solution shows solid state intermolecular aryl-fluoroaryl interactions leading to J-aggregates with intense solid state luminescence. This journal is \ua9 the Partner Organisations 2014

(2-Pyrene-1-yl-vinyl)pyridine: a highly transparent chromophore with an unexpected large second-order nonlinear optical response

In the field of electrooptic materials, the rational design and synthesis of chromophores endowed with high transparency together with large second order nonlinear optical (NLO) response is a field of intense research activity. Many organic and metallorganic second order NLO chromophores have been designed according to the \u2018\u2018push-pull\u2019\u2019 strategy, where electron-donating (D) and electron-withdrawing (A) end groups interact through a delocalized \uf070-electron bridge to generate an intramolecular charge transfer transition [1]. On the other hand, far less attention has been devoted to low dipole moment chromophores, though in some instance they have been shown to possess large hyperpolarizability \uf062 [2]. Here we report on the second order NLO properties of (2-pyrene-1-yl-vinyl)pyridine, 1, a chromophore based on the pyrene moiety which is well studied for its outstanding fluorescence properties (long lifetime and high quantum yield) while its derivatives have never been investigated for their NLO response. Preliminary measurements of the second order NLO properties of 1 in solution by the EFISH technique revealed an unexpectedly high and strongly concentration dependent \ub5\u3b2 value, comparable to that of benchmark NLO chromophores. At high concentrations the decrease of the second order NLO response seems to point to the formation of centrosymmetric aggregates, a feature that is supported also by the emissive behaviour of 1. Interestingly 1 is quite transparent, a relevant property for potential technological applications. These experimental results have been supported by theoretical investigation performed at DFT and Time Dependent DFT level, which has allowed an analysis of the electronic origin of the NLO response. [1] T. Verbiest, et al. J. Mater. Chem. 7, 1997, 2175. [2] J. Gradinaru, A. Forni, et al. Inorg. Chem. 46, 2007, 884

Perylene diimide \u2013 POSS dyes as a way to inhibit aggregation caused quenching

In recent years there has been an extensive research on the development of efficient solid-state emissive organic materials for organic optoelectronic devices, such as light-emitting diodes, organic field-effect transistors, solid-state lasers and fluorescent sensors. However, most organic chromophores are non-luminescent in the solid state, even if they are highly emissive in solution, owing to the quenching caused by intermolecular interactions such as aggregation caused by \u3c0\u2013\u3c0 stacking [1]. This is the case of perylene tetracarboxylic acid diimides (PDI), an important class of industrial pigments, which have been recently investigated for their interesting properties such as near-unity fluorescence quantum yields in solution, high photochemical stability, and strong electron-accepting character, that allow PDIs to be used in many electronic and optical applications [2]. We report on the preparation of PDI derivatives anchored to inorganic scaffolds such as Polyhedral Oligomeric Silsesquioxanes (POSS) with the aim to suppress the quenching which occurs in the solid state due to \u3c0\u2013\u3c0 stacking of this kind of emitting chromophores. The new PDI-POSS compounds here presented show in solution the typical absorption and emission features of the monomeric perylene unit, with a quantum efficiency close to unity, while in the solid state (both as spin-coated films and powders) the fluorescence quantum yield is positively affected by the presence of the POSS cage, with a quantum efficiency about 6 times that of the corresponding perylene tetracarboxylic bisimide in the solid state. [1] M. Shimizu, T. Hiyama, Chem. Asian J. 5, 2010, 1516. [2] C. Huang, S. Barlow, S.R. Marder, J. Org. Chem. 76, 2011, 2386

Mononuclear copper(I) complexes of O-t-butyl-1,1-dithiooxalate and of O-t-butyl-1-perthio-1-thiooxalate

Described are the syntheses and structures of a phosphonium salt of the anionic ligand O-t-butyl-1,1-dithiooxalate, [PPh 3Bz][i-dto tBu] ([PPh 3Bz][1]), and of two Cu(I) complexes of this anion, Cu(PPh 3) 2(\u3b7 2-i-dto tBu) (2) and Cu(dmp)(PPh 3)(\u3b7 1-i-dto tBu) (3, dmp = 2,9-dimethyl-1,10-phenanthroline). In addition, it was found that the reaction of CuBr 2 with i-dto tBu - gives a O-t-butyl-1-perthio-1-thiooxalato complex of copper(I), [BzPh 3P][Cu(Br)(S-i-dto tBu)] ([BzPh 3P][4]), where [S-i-dto tBu] - is a disulfide-containing anionic ligand. The electronic structure and absorption spectrum of this species were investigated by time dependent DFT methods

New organic–inorganic hybrid materials based on perylene diimide–polyhedral oligomeric silsesquioxane dyes with reduced quenching of the emission in the solid state

Solid state luminescent materials are the subject of ever growing interest both from a scientific and a technological point of view because high-tech applications of light emitting materials very often require their use in the condensed phase. Aggregation caused quenching processes however represent an obstacle to the development of most luminogens in the condensed phase. This is why particularly fascinating are those materials showing high emission intensity in the solid state. Aggregation caused quenching is particularly detrimental for \u3c0-extended polycyclic aromatic hydrocarbons, for example perylene tetracarboxylic acid diimides which are characterized by a near-unity fluorescence quantum yield in solution but are far less emissive in the solid state. Here we report on the easy preparation and on the optical investigation of perylene tetracarboxylic acid diimide derivatives linked to the inorganic cage of polyhedral oligomeric silsesquioxanes. These new hybrid perylene diimide-polyhedral oligomeric silsesquioxane dyes show in solution the typical absorption and emission features of the perylene diimide fragment, with a quantum efficiency close to unity. Moreover, in the solid state (both as spin-coated films and powders) the electronic absorption spectra indicate a reduced fluorophore aggregation and significant quantum yield efficiencies induced by the positive effect of the polyhedral oligomeric silsesquioxane cage