S-Shaped Double Helicene Diimides: Synthesis, Self-Assembly, and Mechanofluorochromism

Abstract

Herein we present a synthesis of an S-shaped double helicene with fused imide moieties, achieving a contorted aromatic diimide (DHDI) with good fluorescence properties in both solution and the solid state. DHDI demonstrates distinct mechanofluorochromism from yellow to green emission under grinding of its crystalline powder.Letter pubs.acs.org/OrgLett

An S-shaped double helicene showing both multi-resonance thermally activated delayed fluorescence and circularly polarized luminescence

“…This FWHM value is considerably smaller than many of the helicene compounds reported in the literature (often 50 – 80 nm). 1,16,19,81,91–93,95 The PL spectrum at 77 K is nearly identical to that at room temperature. Furthermore, a very small degree of positive solvatochromism is observed (Fig.…”

“…This also leads to internal bond angles that are considerably different from that of an ideal planar benzene ring. This is not usually the case for S-shaped double helicenes, [90][91][92][93] and as such, in Hel-DiDiKTa, the central benzene e-ring (Scheme 1b) has internal bond angles between 118.73 (10) and 122.54 (10)1 and C-C bond distances between 1.3641(17) and 1.4207(15) Å (Scheme 1c). There is only one pÀp stacking interaction between adjacent molecules (packing diagram displayed in Scheme 1e), the c-ring interacting with the g-ring [centroidÁÁÁcentroid distance 3.6875( 6) Å], resulting in p-stacked chains running along the b-axis.…”

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

“…However, in contrast to DH - 1 , DH - 2 exhibits multiple S···H (2.88 Å), S···C (3.45 Å), and Se···H (2.94 Å) interactions between two molecules in the unit cell. These multiple interactions confer DH - 1 and DH - 2 with a regular arrangement featuring multi channels (Figures S4 and S8 in Supporting Information File 2 ), which is a suitable characteristic for helicene compounds used as supramolecular self-assembly units [ 34 – 41 ].…”

Mechanochromic luminogens with hypsochromically shifted emission switching property: recent advances and perspectives

“…Recently Zhang et al synthesized an S-shaped double helicene with fused imide moieties, 81 (Chart 8). 143 The original sample of 81 had yellow emission and showed two emission peaks at 538 and 580 nm in its emission spectra. The original sample on mechanical grinding changed its colour from yellow to green, and the emission peak in the longer wavelength region, at 580 nm, shrunk significantly (Fig.…”