Arnault Heynderickx

Bandrowski's base revisited: toward a unprecedented class of quinonediimines or new two-way chromophoric molecular switches.

Temperature-controlled reactivity places Bandrowskis base 3 at the crossroads of a new versatile strategy for the preparation of two different categories of chromophores. We describe the access to a new class of quinonediimines (8) with an extended pi-conjugation owing to the presence of imine functions. Under slightly different conditions, Bandrowskis base appears to be the precursor of choice in the preparation of a novel pH- and light-dependent binary molecular switch. This molecule (11) is constituted of a benzobis(imidazole) core that can be reversibly protonated and a diarylethene unit which can be reversibly converted into its closed form upon irradiation. Triggered by two independent variables, 11 provides four distinct optical states for molecular number processing.

Synthesis and photochromic behaviour of new dipyrrolylperfluorocyclopentenes

The synthesis of new photoswitchable dipyrrolylethenes having different π-conjugated chain lengths, employing Wittig–Horner reaction, Knoevenagel condensation, Suzuki palladium catalyzed cross-coupling or Sonogashira coupling, is reported. Their photochemical behaviour, and in particular, their thermal stability has been investigated upon continuous irradiation with light of appropriate wavelengths.

New and facile synthesis of 3-styrylflavones

Abstract A simple synthetic access to 3-styrylflavones is developed through the reaction of 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-diones with phenylacetic aldehydes. The structure of parent compound is confirmed by X-ray analysis.

Synthesis and Photochromic Properties of Functional Diarylethenes with a [1,3]dithiol-2-one (Thione) Bridging Unit

ABSTRACT In designing new photochromic compounds for optical data storage and photoswitching devices, the synthesis of a series of 4,5-diaryl-1,3-dithiol-2-one and 4,5-diaryl-1,3-dithiol-2-thione, which are suitable building blocks for incorporation with fluorophore, is herein reported. Our strategy needs the preliminary preparation of diarylalkynes, obtained by successive Sonogashira-Hagihara coupling-reactions in good yields (63–92%). A combination of these synthetic precursors with diisopropylxanthogen disulfide leads to the corresponding 4,5-diaryl-1,3-dithiol-2-ones under radical conditions with excellent yields (54–70%). The thionation of these compounds is obtained nearly quantitatively with phosphorous pentasulfide.

Photoinduced Processes in Dipyrrolyl‐Perfluoro‐Cyclopentenes

Abstract The photobehavior of five photochromic dipyrrolyl-perfluoro-cyclopentenes was studied by steady state and time-resolved absorption spectroscopy. The quantum yields of the UV-photoinduced ring-closing reaction (coloration) and the visible-stimulated cycloreversion reaction (bleaching) were measured. Kinetic and thermodynamic parameters of thermal bleaching were also determined. Nanosecond time-resolved experiments showed formation of a transient, which was not a precursor of the reaction photoproduct. This transient was tentatively assigned to a radical cation formed by direct photoionization through a short-lived triplet state. The nature of the transient species was supported by photoinduced electron transfer to electron acceptors.

Photophysics and Photochemistry of some Dipyrrolylperfluorocyclopentenes

ABSTRACT The relaxation properties of the lowest excited states of singlet and triplet multiplicity of some photochromes with dipyrrolylperfluorocyclopentene structure have been investigated by conventional and time-resolved spectrometric techniques. These compounds can be photocoloured with a fairly high quantum yield (ΦPC ≥ 0.5). The bleaching is thermal and photochemical. The fluorescence emission is scarceor undetectable. No triplet absorption was observed by laser flash photolysis, whereas transients unaffected by oxygen (lifetimes in the range 60 ns–10 μs) were detected beside the metastable closed form.

Revisiting Old Series and Rational Design of Novel Photochromics

ABSTRACT The reinvestigation of photochromic systems (appeared several decades ago) involving hydrogen transfer is described. For instance sulfonyl-substituted 2-benzylpyridine (or benzothiazole) and 2-benzyl-3-benzoylchromones or quinolones undergo thermoreversible photochromic reactions at room temperature. Taking benefit of the chemical or photochemical reactivity of the enol form of the last class of compounds, novel thermoreversible or photoreversible photochromic systems have been designed (1,2-dihydrothioxanthenones and 3-(2-benzylbenzoyl)quinolones respectively), opening promising opportunities for future applications.