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A new class of push-pull 1,1,4,4-tetracyanobutadienes (TCBDs) chromophores bearing a γ-pyranylidene as a pro-aromatic donor group have been developed, characterized and studied for their electrochemical, photophysical and second-order nonlinear optical (NLO) properties. [2 ​+ ​2] Cycloaddition-retroelectrocyclizations (CA-RE) with tetracyanoethylene (TCNE) allowed the formation of new TCBDs by taking advantage of the electron-donating ability of γ-pyranylidene functional groups. The limits of the reaction between TCNE and the corresponding alkynes have been investigated, both in terms of reactivity and solubility. Electrochemical studies of pyranylidene-TCBD 1a-1j revealed two reversible reduction waves typical of TCBDs, and two oxidation waves originating from the γ-pyranylidene moiety. More complex electrochemical signals have been recorded when studying chromophores bearing multiple TCBD and/or γ-pyranylidene units. All pyranylidene-TCBDs showed panchromatic absorption properties, extending to the NIR in some cases. Changes made around the electron-withdrawing TCBD units significantly affected the ICT performance of the push-pull chromophores. Computational studies have been performed on this series of compounds to rationalize the origin of their optical properties. TD-DFT calculations confirmed that the synthesized pyranylidene-TCBDs are potential NLOphores. The second-order NLO properties of all chromophores were determined by the Electric Field-Induced Second Harmonic generation (EFISH) technique, and all systems exhibited valuable NLO properties with large μβEFISH values for purely organic compounds, up to 5700 10−48 ​esu.

Abstract A series of surface‐functionalized gold nanocatalysts are synthesized. Through diazonium chemistry, calix[4]arene molecules are grafted at the gold surface. Sharing the same anchoring function and a common backbone, the calix[4]arene ligands possess distinct terminal chemical functions where the length, hydrophobic nature, and oxygen affinity are varied. Thanks to the versatility of the calix[4]arene platform, this paper only focuses on the molecular tuning of the solid/liquid interface through the change of the tail groups while electronic effects that are regulated by the anchoring function will be similar for all catalysts. Electrocatalytic tests demonstrate the influence of the tails group on the oxygen reduction reaction performances, including efficiency, selectivity, and durability. Beyond a pure geometric steric effect, it is shown that chemical properties of the ligands can effectively tune the interactions between the metallic catalyst and the electrolyte and reactants.

Pioneered by J. Pinson and coll. in 1990s, the reductive grafting of aryldiazonium salts has become a powerful method for surface functionalization. Highly robust interfaces result from this surface attachment, resistant to heat, chemical degradation and ultrasonication. Importantly, this approach can be applied to many materials, ranging from conducting, semi-conducting, oxides to insulating substrates. In addition, either massive, flat surfaces or nanomaterials can be functionalized. The method is easy to process and fast. The grafting process involves the formation of highly reactive aryl radicals able to attack the substrate. However, the generated radicals can also react with already-grafted aryl species, leading to the formation of loosely-packed polyaryl multilayer films, typically of 10–15 nm thick. It is thus highly challenging to control the vertical extension of the deposited layer and to form well-ordered monolayers from aryldiazonium salts. In this mini review, we briefly describe the different strategies that have been developed to prepare well-ordered monolayers. We especially focus on two strategies successfully used in our laboratories, namely the use of unconventional solvents, i.e., room temperature ionic liquids (RTILs), as grafting media and the use of calixarene macrocycles by taking benefit of their pre-organized structure. These strategies give large possibilities for the structuring of interfaces with the widest choice of materials and highlight the potential of aryldiazonium grafting as a competitive alternative to self-assembled monolayers (SAMs) of alkyl thiols.