Chiral Memory Units Based on Dynamic Redox Systems with a Dibenzoxepinone Skeleton: Drastic Change in Racemization Barrier and Electrochemical Bistability
摘要:
The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.
Geometrical Remote Steric Effects in 4,5-Disubstituted-9,10-dihydrophenanthrenes: Expansion of Prestrained C<sup>9</sup>–C<sup>10</sup> Bond in Di(spiroacridan) Derivatives
By attaching bulky substituents at the bay region of di(spiroacridan)-substituted dihydrophenanthrene 1a, the prestrained C9–C10 bond in the dihydrophenanthrene (DHP) skeleton of 1c–1e is expanded from 1.634(2) to 1.649(3)–1.652(6) Å, which demonstrates the bond expansion through remote steric effects. Twisting deformation of the DHP skeleton is the key to transfer the steric bulkiness from the C4/C5 positions to cause the additional strain in the C9–C10 bond.
Acridine-based novel fluorophores 1/2 with a helical dihydrodibenzoxepin/azepine skeleton exhibit halochromic response upon addition of Brønsted acid in CH2Cl2, thus giving UV–vis and fluorescence spectral changes. By using the optically resolved species [(M)-1/2], circular dichroism (CD) and fluorescence detected-CD (FDCD) signals were also changed drastically, thus demonstrating four-way-output response thanks to configurational stability of helicity and efficient exciton coupling.
Phenanthrene-4,5-diylbis(10-methylacridinium) with a Short C+ - - C+ Contact: Preparation, Molecular Structure, Redox Properties, and Electrochromic Interconversion with Dihydropyrene Derivative
The title dication (1(2+)) was generated by oxidative bond cleavage of a 4,5-dihydoropyrene derivative (2) with two spiro(10-methylacridan) units. Despite the skewed deformation of the arylene spacer, two cationic chromophores in 1(2+) are forced to face in a proximity with a very short interatomic separation of 2.98(1) angstrom between carbenium centers (X-ray), which makes the LUMO level of 1 much lower than that of biphenyl-2,2'-diyl-type dication (3(2+)).
Intramolecular Methylacridan-Methylacridinium Complexes with a Phenanthrene-4,5-diyl or Related Skeleton: Geometry-Property Relationships in Isolable CH Bridged Carbocations
Bridging the gap: Snapshots of 1,6‐H‐shift precursors indicate that a narrower CH⋅⋅⋅C+ separation (D in the ORTEP diagram) in the title complexes induces faster degenerate rearrangement of 1+. A contact distance of less than 2.7 Å is necessary to realize the organic three‐center two‐electron bond of [CHC]+, as indicated by extrapolation of the X‐ray data.
Chiral Memory Units Based on Dynamic Redox Systems with a Dibenzoxepinone Skeleton: Drastic Change in Racemization Barrier and Electrochemical Bistability
The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.