Tuning the ease of formation of on-surface metal-adatom coordination polymers featuring diketones.

We use pyrene-4,5,9,10-tetraketone molecules with substituents of varying bulkiness in the 2,7 positions to probe the generality and versatility of the previously reported on-surface coordination of two diketones with a single metal atom, leading to one-dimensional coordination polymers. Three different low index surfaces of group 11 metals (Cu, Ag and Au) are used to provide both the support and the metal atoms for metal-organic coordination. By real space visualisation with single molecule resolution employing scanning tunnelling microscopy we investigate the molecular self-assembly and show how this can be substantiated with the formation of metal-organic linear and cyclic oligomers, depending on the employed substrate.

Twisted Aromatic Frameworks: Readily Exfoliable and Solution-Processable Two-Dimensional Conjugated Microporous Polymers.

Twisted two-dimensional aromatic frameworks have been prepared by overcrowding the nodes with bulky and rigid substituents. The highly distorted aromatic framework with alternating out-of-plane substituents results in diminished interlayer interactions that favor the exfoliation and dispersion of individual layers in organic media.

Promoting Spontaneous Second Harmonic Generation through Organogelation.

An organogelator based on the Disperse Red nonlinear optical chromophore was synthesized according to a simple and efficient three-step procedure. The supramolecular gel organization leads to xerogels which display a spontaneous second harmonic generation (SHG) response without any need for preprocessing, and this SHG activity appears to be stable over several months. These findings, based on an intrinsic structural approach, are supported by favorable intermolecular supramolecular interactions, which promote a locally non-centrosymmetric NLO-active organization. This is in sharp contrast with most materials designed for SHG purposes, which generally require the use of expensive or heavy-to-handle external techniques for managing the dipoles' alignment.

Bis(triisopropylsilylethynyl)-substituted pyrene-fused tetraazaheptacene: synthesis and properties.

The synthesis and characterisation of a pyrene-fused tetraazaheptacene that is constituted of two terminal pyrene units and a central tetraazaanthracene core are reported. The optoelectronic properties (experimental and calculated) of this heptacene derivative are discussed together with its charge transport properties in thin films.

An electron-conducting pyrene-fused phenazinothiadiazole.

A pyrene-fused phenazinothiadiazole that shows electron mobilities (µe = 0.016 cm(2) V(-1) s(-1)) two orders of magnitude higher than those reported for pyrene-fused pyrazaacenes is described.

Dithienopyrrole as a rigid alternative to the bithiophene π relay in chromophores with second-order nonlinear optical properties.

4H-Pyranylidene-containing push-pull chromophores built around a bithiophene (BT) π relay or a rigidified thiophene-based unit, namely cyclopenta[1,2-b:3,4-b']dithiophene (CPDT) or dithieno[3,2-b:2',3'-d]pyrrole (DTP), have been synthesized and characterized. The effect of these different relays on the polarization and the second-order nonlinear optical (NLO) properties has been studied. For the sake of comparison, the corresponding reported dithieno[3,2-b:2',3'-d]thiophene (DTT) derivatives have also been included in the discussion. Replacement of the BT core by a rigidified unit (CPDT, DTP) leads to more polarized systems. Calculated NBO charges and electrochemical measurements show that dithienopyrrole has a remarkable donor character that allows an important charge transfer between the donor and the acceptor. The influence of the rigidification of the BT relay on the NLO responses depends on the acceptor strength. For the weakest acceptor used (thiobarbituric acid), passing from the BT relay to the rigidified units always involves an increase in the µß0 figure of merit. Nevertheless, for the strongest acceptor (2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF)), a slight increase in µß0 with respect to the BT chromophore is only observed for the DTP derivative. Thus, rigidification of the BT core is not enough to improve the second-order nonlinearity and the incorporation of a DTP moiety has proven to be the most efficient approach for this purpose.

Push-pull systems bearing a quinoid/aromatic thieno[3,2-b]thiophene moiety: synthesis, ground state polarization and second-order nonlinear properties.

Chromophores bearing a 2-dicyanomethylenethieno[3,2-b]thiophene moiety in their quinoidal form have been synthesized, exploring for the first time the reactivity of this system towards aldehydes. Their ground state polarization and linear and second-order nonlinear optical (NLO) properties have been determined by a combined experimental and theoretical study, and compared to those of analogous compounds featuring an aromatic thienothiophene unit. Due to the gaining of aromaticity, quinoid systems have been found to display more polarized electronic ground states and higher NLO responses with respect to their aromatic counterparts.