Title
Photocontrol over Molecular Shape: Synthesis and Photochemical Evaluation of Glycoazobenzene Macrocycles
Author
Guillaume Despras, Julia Hain, Sven Ole Jaeschke
Year
2017
Journal
Chemistry: A European Journal
Abstract
Reversible shape switching due to external stimuli is an attractive property for the control of molecular features. Hence, we aimed at macrocycles to investigate photoswitching of molecular shape. We prepared the first carbohydrate-based macrocycles comprising a photoresponsive azobenzene hinge. These macrocycles were readily obtained by cyclization of isothiocyanate-armed bis-azobenzene glycosides with piperazine. The unprotected macrocycles exhibit favorable photochromic properties in water and DMSO. Notably, the efficient trans[RIGHTWARDS ARROW]cis isomerization results in a remarkable shape transformation of the molecule. Additionally, the structure is characterized by restricted conformational freedom of the backbone, resulting in a single main conformer in each geometrical state (trans or cis). Measurement of optical rotation values and circular dichroism spectra revealed a tremendous change in chirality upon photoisomerization, with a strong helical induction in the cis state. These findings highlight the applicability of the new macrocycles as chiroptical molecular switches.
Instrument
J-720
Keywords
Circular dichroism, Stereochemistry, Cotton effects, Organic chemistry