Dithienylethenes bridged porphyrins

However, not all the six prepared compounds (Scheme 3b) underwent photochemical isomerization the photoisomerization reactivity of these dithienylethene-bridged diporphyrins strongly depended on the distance between the porphyrin and dithienylethene. The three compounds, in which porphyrin and dithienylethene were directly linked (1), linked through a 1,4-phenylene (2), and linked through meso-ethynylene (5), did not exhibit any photochromism. The authors attributed it to the efficient quenching of the excited dithienylethene by the attached porphyrin moiety through intramolecular energy transfer. 

In 2008, Kim H-J et al. reported a photochromic fluorescence switching of porphyrin-bridged dithienylethenes, in which two dithienylethene derivatives were axially coordinated to the two sides of porphyrinato tin complex [35]. As depicted in Scheme 7, this photochromic fluorophore (Sn(TTP)(DTE)2) was synthesized by the inter-molecular etherification of trans-dihydroxo (5,10,15,20-tetratolylporphyrinato) tin and two phenolic derivatives of 1,2-dithienylethene. 

Recently, a ternary complex for a signal transmission system has been constructed by Aida and his co-workers [36], It involved three movable components a biaryl derivative bearing four zinc porphyrins (2), a pyridine-appended dithienylethene derivative (1), and a chiral tetrasubstituted ferrocene (3 ), as illustrated by its structure (Scheme 8). The three components were interconnected with bidentate coordination bonds. Component 2 was the bridge between 1 and 3. The well-designed triad was built up by multi-step reactions through routine methods. 

---