Karen Wright

Three complex ferrocene‐BODIPY‐fullerene‐peptide conjugates were synthesized by successive CuAAC reactions between firstly ferrocene‐BODIPY azides, then a lipoyl peptide azide, with a dual‐clickable fullerene platform. These conjugates displayed broad absorption in the visible region due to their extended π‐conjugation and the presence of an intramolecular charge transfer band from ferrocene to BODIPY, particularly in the case of BODIPY derivatives functionalized at the beta and alpha positions with ethynylFc and vinylFc groups, respectively. The terminal lipoyl peptide allowed grafting of the conjugates on gold surfaces, to form self‐assembled monolayers that were characterized by PM‐IRRAS and ultrafast electrochemical techniques. Estimation of the heterogeneous electron transfer rate constants for these monolayers revealed higher values for electron transfer from the BDP or C ₆₀ entities to the metal surface compared with conjugates without ferrocene units. This could be attributed to a reduced distance between the (Fc) ₂ ‐BODIPY‐C ₆₀ part and the metal surface, due to folding of the conjugates within the monolayer.

Two BODIPY‐C₆₀‐peptide assemblies were synthesized by CuAAC reactions of BODIPY‐C₆₀ dyads and a helical peptide functionalized with a terminal alkyne group and an azide group, respectively. The helical peptide within these assemblies was functionalized at its other end by a disulfide group, allowing formation of self‐assembled monolayers (SAMs) on gold surfaces. Characterizations of these SAMs, as well as those of reference molecules (BODIPY‐C₆₀‐alkyl, C₆₀‐peptide and BODIPY‐peptide), were carried out by PM‐IRRAS and cyclic voltammetry. BODIPY‐C₆₀‐peptide SAMs are more densely packed than BODIPY‐C₆₀‐alkyl and BODIPY‐peptide based SAMs. These findings were attributed to the rigid peptide helical conformation along with peptide‐peptide and C₆₀‐C₆₀ interactions within the monolayers. However, less dense monolayers were obtained with the target assemblies compared to the C₆₀‐peptide, as the BODIPY entity likely disrupts organization within the monolayers. Finally, electron transfer kinetics measurements by ultra‐fast electrochemistry experiments demonstrated that the helical peptide is a better electron mediator in comparison to alkyl chains. This property was exploited along with those of the BODIPY‐C₆₀ dyads in a photo‐current generation experiment by converting the resulting excited and/or charge separated states from photo‐illumination of the dyad into electrical energy.

Ferrocene‐BODIPY (Fc‐BDP) conjugates in which one or two ferrocene entities are linked to the β‐positions of the BODIPY core by an ethynyl bridge have been developed. These derivatives were easily and efficiently grafted onto a dual‐clickable fullerene platform using CuAAC reactions, leading to a clickable Fc‐BDP‐C₆₀ triad and a clickable [Fc]₂‐BDP‐C₆₀ tetrad which can be used for further derivatization with complex structures. Due to the extended π‐conjugation and the presence of an intramolecular charge transfer band from Fc to BDP, all these conjugates display a broad absorption in the visible region, which is bathochromically shifted when two Fc are appended to the BDP core. Ultrafast multistep electron transfers leading to charge stabilization were demonstrated in the Fc‐BDP‐C₆₀ triad and [Fc]₂‐BDP‐C₆₀ tetrad by femtosecond transient absorption studies.

A set of π-conjugated diindenothienothiophene derivatives (DITTs) which formally possess an extended as-indacene core with 16 π-electrons has been synthesised and their closed-shell configuration has been confirmed by X-ray structure analysis. Bond lengths analysis provides insight into the peculiar bond lengths observed for diindenoacene diradicaloids. The annellation mode at the outer rings has a great impact on the tropicity, optoelectrochemical properties and molecular packing. The featured molecules exhibit low energy band gap with values up to 1.30 eV and have high electron affinities with LUMO energies up to 3.86 eV. Their optical properties are similar to those of benzo-fused indeno[2,1-c]fluorene (BIFs) counterparts possessing formally the as-indacene core. Analysis of the molecule tropicity using NICS and ACID plot shows that the central rings of DITTs are weakly antiaromatic and should be regarded as quinoidal molecules bridged by two sulphur atoms. Three out of four molecules show ambipolar behavior in OFETs with moderate mobilities.

We report the synthesis and optoelectronic properties of TIPS‐peri‐pentacenopentacene (TIPS‐PPP), a vertical extension of TIPS‐pentacene (TIPS‐PEN) and a low‐band‐gap material with remarkable stability. We found the synthetic conditions to avoid the competition between 1,2‐ and 1,4‐addition of lithium acetylide on the large aromatic dione. The high stability of TIPS‐PPP is due to the peri‐fusion which increases the aromaticity by generating two localized aromatic sextets that are flanked with 2 diene fragments, similar to two fused‐anthracenes. Like TIPS‐PEN, TIPS‐PPP shows the archetypal 2D brickwall motif in crystals with a larger transfer integral and smaller reorganization energy. The high mobility of up to 1 cm² V⁻¹ s⁻¹ was obtained in an organic field‐effect transistor fabricated by a wet process. Also, TIPS‐PPP was used as a near‐infrared (NIR) emitter for NIR organic‐light‐emitting‐diode devices resulting in a high external quantum efficiency at 800 nm.

We report the synthesis and optoelectronic properties of TIPS‐peri‐pentacenopentacene (TIPS‐PPP), a vertical extension of TIPS‐pentacene (TIPS‐PEN) and a low‐band‐gap material with remarkable stability. We found the synthetic conditions to avoid the competition between 1,2‐ and 1,4‐addition of lithium acetylide on the large aromatic dione. The high stability of TIPS‐PPP is due to the peri‐fusion which increases the aromaticity by generating two localized aromatic sextets that are flanked with 2 diene fragments, similar to two fused‐anthracenes. Like TIPS‐PEN, TIPS‐PPP shows the archetypal 2D brickwall motif in crystals with a larger transfer integral and smaller reorganization energy. The high mobility of up to 1 cm² V⁻¹ s⁻¹ was obtained in an organic field‐effect transistor fabricated by a wet process. Also, TIPS‐PPP was used as a near‐infrared (NIR) emitter for NIR organic‐light‐emitting‐diode devices resulting in a high external quantum efficiency at 800 nm.