Single-molecular electronics and organic material electronics are expanding research fields that ultimately aim for a vast variety of different applications, ranging from organic light-emitting diodes, to novel ways to improve the performance and decrease the size of electronics components. To achieve these goals, research has to be focused both on the development of functional molecules, but also on device fabrication. The work of this thesis is focused on the development of synthetic routes towards novel molecules for potential organic electronics applications, together with an investigation of their optical and electronic properties. The first part of the thesis describes the synthesis of butadiyne-substituted and diacetylenic phosphaalkenes. Theoretical, spectroscopic and electrochemical techniques have been used to understand key steps during their synthesis, and to gain further information on the conjugative properties of their π-systems. A mechanism is proposed for the formation of the butadiyne-substituted and diacetylenic phosphaalkenes and it is shown that the phosphorus heteroatom is an intrinsic part of the π-conjugated system. The incorporation of the phosphorus heteroatom leads to decreased HOMO-LUMO gaps compared to all-carbon based reference compounds. In the second part of the thesis, acetylenic phosphaalkenes are utilized for the preparation of phosphaalkene-substituted phospholes. A first step towards the exploration of the difference in reactivity of the σ2, λ3 phosphaalkene-P and the σ3, λ3 phosphole-P is presented as the oxidation of the compounds by sulfur proceeds selectively at the σ3, λ3–P. Spectroscopic and electrochemical investigations show that the phosphaalkene is an integral part of the compounds’ π-systems, and induces a HOMO-LUMO gap decrease compared to reference compounds that lack the P=C substituent. The third part of this thesis presents an exploratory study concerning the suitability of metathesis reactions for the assembly of alkene-bridged phosphaalkenes.

Les oligophénylènes constituent une classe de molécules centrale dans la conception de semi-conducteurs organiques pour des applications optoélectroniques. Ces travaux portent sur la synthèse et l’étude approfondie de dérivés linéaires et cycliques du fluorène (un biphényle rigidifié par un pont méthylène), fragment constitutif essentiel dans l’électronique organique. Nous nous intéressons en particulier aux relations structure-propriétés de ces systèmes π-conjugués. Dans une première partie, avec comme cadre le développement de matériaux hôtes pour diodes électroluminescentes (PhOLEDs), nous présentons une étude de la régioisomérie de phényl-fluorènes et de phényl-spirobifluorènes. Ses résultats ont permis la préparation de quatre matériaux hôtes purs hydrocarbures, dimères de spirobifluorène, intégrés dans des PhOLEDs bleues à hautes performances. Dans une seconde partie, nous nous intéressons au domaine récent des nano-anneaux moléculaires, objets cycliques présentant une conjugaison π de nature singulière. Après une revue bibliographique portant sur les cycloparaphénylènes et leurs propriétés, nous présentons nos études concernant plusieurs exemples de leurs analogues pontés : les cycloparafluorènes. / Oligophenylenes constitute a major class of molecules in the design of organic semiconductors for optoelectronics applications. This work involves the synthesis and in-depth study of linear and cyclic derivatives of fluorene (a biphenyl rigidified by a methylene bridge), an essential building block in organic electronics. We focus our attention on the structure-property relationships of these π-conjugated systems. In a first part, within the framework of host materials for phosphorescent organic light-emitting diodes (PhOLEDs), we present a regioisomerism study of phenyl-fluorenes and phenyl-spirobifluorenes. Its results enabled the preparation of four pure hydrocarbon host materials, spirobifluorene dimers, used in high-performance blue PhOLEDs. In a second part, we take interest in the emerging field of molecular nanorings, cyclic objects presenting a singular nature of π-conjugation. After a bibliographical review covering cycloparaphenylenes and their properties, we present our studies regarding several examples of their bridged analogues: cycloparafluorenes.

Two-dimensional conjugated covalent organic frameworks (2D c-COFs) are emerging semiconductor materials for optoelectronic and photothermal applications. In particular, the highly tailorable, semiconducting thiophene-based 2D c-COFs have attracted considerable interest due to their nontrivial physicochemical properties such as photo-activity, broad optical absorption, tunable electronic structures, and so forth. Herein, we demonstrate a novel, crystalline 2D c-COF based on thienyl-functionalized benzodithiophene (BDT) and biphenyl (BP) via the Schiff-base polycondensation reaction. The resultant BDT-BP-COF exhibits a broad optical absorption up to ca. 600 nm and decent π-conjugation along the 2D polymer skeleton, as revealed by the optical absorption and theoretical calculations. The favorable π-conjugation and the abundant electron-rich thiophene units confer excellent photo-activity to BDT-BP-COF towards the usage of solar energy. As a proof-of-concept application, we explore BDT-BP-COF in photothermal conversion, in which it shows a fast surface-temperature increase upon light irradiation for seconds.