Driving Unidirectional Molecular Rotary Motors with Visible Light by Intra- And Intermolecular Energy Transfer from Palladium Porphyrin

Abstract

Driving molecular rotary motors using visible light (530−550 nm) instead of UV light was achieved using palladium tetraphenylporphyrin as a triplet sensitizer. Visible light driven rotation was confirmed by UV/vis absorption, circular dichroism and

Visible‐Light‐Activated Molecular Switches

“…Interestingly,ring closure from the triplet state (l irr = 450 nm) and from the singlet state (l irr = 345 nm) occurred with very similar quantum yields.Incompound 11,aRe I -phenantroline complex was directly integrated into the DAEf ramework, thereby resulting in aM LCT band centered around 400 nm. [63] An overcrowded alkene was coupled to aPdporphyrin derivative serving as at riplet sensitizer (compound 12,F igure 7) to give asystem requiring no UV light to operate.S imilarly to the two cases described above (compounds 10 and 11), the isomerization occurred via the T 1 state of the overcrowded alkene upon irradiation at 530 nm, with similar efficiency to direct excitation of the motor with UV light (quantum yields F % 0.1), as well as with comparable photoconversion (67 %). Although the latter design is quite elegant since it involves arather compact structure compared to compound 10,t he closed isomer was found to be thermally rather unstable for aD AE derivative (t 1/2 of ca.…”

“…[63] An overcrowded alkene was coupled to aPdporphyrin derivative serving as at riplet sensitizer (compound 12,F igure 7) to give asystem requiring no UV light to operate.S imilarly to the two cases described above (compounds 10 and 11), the isomerization occurred via the T 1 state of the overcrowded alkene upon irradiation at 530 nm, with similar efficiency to direct excitation of the motor with UV light (quantum yields F % 0.1), as well as with comparable photoconversion (67 %). [63] The motor is driven by alternating green light (l = 530 nm) irradiation and thermal helix inversion. Thesystem was shown to operate in an intermolecular fashion as well, that is,with the two components simply mixed rather than linked together.Note that in arelated earlier example, [64] an azobenzene derivative connected to ap orphyrin moiety could surprisingly undergo E!Z isomerization upon irradiation at 500 nm as well.…”

Porphyrins functionalized by quaternary pyridinium units

“…Four examples selected from reports on copper [82,83], palladium(II) [84,85] and platinum(II) porphyrins [86,87] are mentioned below. Attention should be paid to interaction of aggregates of oppositely charge achiral porphyrins CuA and TPPS with phenylalanine aggregates serving as a chiral template; this process leads to chirality induction and self-amplification shown by porphyrin CuA and TPPS aggregates.…”

Toward Fast and Efficient Visible‐Light‐Driven Molecular Motors: A Minimal Design

“…From the point of view of applications, adding to these challenges is the fact that most overcrowded‐alkene motors are driven by energetic UV light, which is more damaging to the motors and their environment than visible light. Thus, a key goal in the development of light‐driven molecular motors is to make them responsive to visible light, so as to facilitate their usage in biological systems and other soft materials …”