As part of a series of investigations related to the construction of metal-free magnetic resonance imaging (MRI) contrast agents as alternatives to gadolinium agents, water-soluble biradicals, denoted as 1-AMP and 2-HEG, were prepared, in which two stable radicals were introduced to a ureabenzene framework. We found that 1-AMP possessed an amphiphilic side chain that consisted of an alkyl group and a hexaethylene glycol (HEG) chain, whereas 2-HEG possessed only an HEG chain. Accordingly, the biradicals showed self-assembly behavior due to multiple intermolecular interactions through which nanoparticles were formed in a water solution. Magnetic interaction took place in both biradicals, and the estimated interaction strength was J = 5.4 mT. Through MRI measurement, the water proton relaxivities, r 1, were estimated to be 0.12 and 0.41 mM–1 s–1 for 1-AMP and 2-HEG, respectively; in other words, the r 1 value for 2-HEG was approximately twice as high as that of monoradical-based contrast agents.

Small chiral organic molecules with CD properties are in high demanded due to their potential use in promising electronic and biological applications. Herein, we reveal a system in which the oxidation of a phosphino group to the corresponding phosphine oxide on the inner rim of a helicene derivative induces a CPL response. Laterally π-extended 7,8dihydro[5]helicenes bearing phosphine and phosphine oxide groups on their inner helical rims (i. e., the C1 position) were synthesized, and their helical structures were unambiguously determined by X-ray crystallography. The photophysical (UV/ visible and emission) and chiroptical properties of these compounds were investigated in various solvents. Despite their structural similarities, phosphine oxide showed a significantly better CPL response than phosphine, with a high dissymmetry factor for emission (j g lum j = (1.3-1.9) × 10 À 3 ) that can be attributed to structural changes in the interior of the helicene helix.

Invited for the cover of this issue are the groups of Kazuteru Usui and Satoru Karasawa at Showa Pharmaceutical University, and Yoshitane Imai at Kindai University. The image depicts how a phosphine‐oxide‐bearing helicene exhibits markedly enhanced CPL response in the excited state compared with that of one with a corresponding phosphine. Read the full text of the article at 10.1002/chem.202202922.

Helicenes with controllable chiroptical properties: Herein, we reveal a system in which the oxidation of a phosphino group on the inner rim of a helicene derivative induces a circularly polarized luminescence (CPL) response. A helicene bearing a phosphine oxide group exhibits a markedly enhanced CPL response in the excited state compared with that of such a helicene with a corresponding phosphine. More information can be found in the Research Article by K. Usui, Y. Imai, S. Karasawa, and co‐workers (DOI: 10.1002/chem.202202922).