title: A self-locking molecule operative with a photoresponsive key.
abstract: Rotary host 1, composed of a ferrocene unit as a rotary module, is conformationally locked internally in apolar solvents such as benzene by a double intramolecular Zn-N coordination between the zinc porphyrin and aniline units, attached to each cyclopentadienyl (Cp) ring. Upon addition of the cis form of 1,2-bispyridylethylene (cis-2) to (+)-1 ([cis-2]/[(+)-1] = 5.0), an enantiomer of 1, the intramolecular Zn-N coordination bonds in (+)-1 are readily cleaved to form an externally locked, cyclodimeric one-to-one complex (+)-1 subset cis-2, accompanying a rotation of the ferrocene module, as visualized by CD spectroscopy. In contrast, use of trans-2, in place of cis-2, under otherwise identical conditions to the above, did not result in releasing the internal double lock of (+)-1. Such a large difference between the isomers of 2 in the affinity toward host 1, along with their capabilities of photochemical interconversion, allowed for the demonstration of a reversible self-locking operation of 1. Namely, the externally locked state of 1, as in the form of 1 supersetcis-2, spontaneously retrieves the internally locked state, after the release of 2 from 1 upon cis-to-trans photochemical isomerization of ligating 2, while the backward photochemical isomerization of 2 in the presence of 1 results in switching of 1 to its externally locked state.
authors.affiliation: Department of Chemistry and Biotechnology, School of Engineering, and Center for NanoBio Integration, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Muraoka
authors.forename: Kazushi
authors.initials: K
authors.lastname: Kinbara
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D002942:Circular Dichroism; D003517:Cyclopentanes / Q000737:chemistry; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D000075163:Metallocenes; D008665:Metalloporphyrins / Q000737:chemistry; D008958:Models, Molecular; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000814:Aniline Compounds; D003517:Cyclopentanes; D005296:Ferrous Compounds; D000075163:Metallocenes; D008665:Metalloporphyrins; D011725:Pyridines; C017802:zinc hematoporphyrin; C023650:aniline; C004998:ferrocene