heynderickx arnault CINaM

TOWARD AN ELECTROMODULATION OF PHOTOCHROMIC PROPERTIES

The photochromism proceeds by a pericyclic reaction of opening of the cycle pyran. By absorption UV, the colorless closed form sudden a rupture of the connection Csp3 - O undergoes to lead to called colored quasi-plane forms photomerocyanines. The opposite reaction is often a spontaneous thermal process but can be also induced by luminous irradiation in the visible one.

The design and synthesis of organic photochomic compounds displaying bistability is an intense research area motived by applications in optoelectronics, optical memory or switching devices.
In line with our investigation towards development of molecular switches a novel tetrathiafulvalene vinylogue containing two naphthopyran groups at the vinyl position is reported.
Electrochemical oxidation of the tetrathiafulvalene vinylogue moiety 1 leads to an extended conjugated species 2 in which the two chromophores are held in strong electronic communication.

The photoisomerization of dimer 2 was achieved, by irradiation of acetonitrile solution (3.10-5 M) in presence of air, at wavelength corresponding to the absorption band (360 nm) of the closed-ring isomer.
Its UV irradiation gave rise to photoinduced absorption in the visible region (511 nm). The photoinduced species are thermally unstable and also sensitive to visible light, leading to the initial closed 2.