Directional Control of π-Conjugation Enabled by Distortion of the Donor Plane in Diarylaminoanthracenes: A Photophysical Study

Abstract

We designed and synthesized a series of diarylaminoanthracenes in which the planarity of the diarylamine moiety is controlled by methylene- or ethylene- bridges. The X-ray crystallographic structures confirm that the methylene- and ethylene bridges gradually decrease the disorder of the diarylamine planes. To quantitatively analyze the photophysical properties and underlying electronic structures of these compounds, we carried out UV-vis and fluorescence spectroscopy, fluorescence quantum yield, and fluorescence lifetime measurements. The results reveal that enhanced planarity of the diarylamine moiety optically forbids the charge-transfer transition between the diarylamine and anthracene moieties. Although it is generally accepted that a planar π-conjugated system favors electron delocalization, our results indicate that distortion of the donor plane induces interchromophoric conjugation rather than conjugation within the local structure. Density functional theory calculations further illustrate that the frontier orbitals of diarylamine and anthracene interpenetrate as the donor plane is distorted. Additionally, natural bonding orbital analyses reveal that distortion of the donor plane changes the directionality of the π-conjugation of the nitrogen n-orbital from intrachromophoric to interchromophoric.

Recent advances in twisted intramolecular charge transfer (TICT) fluorescence and related phenomena in materials chemistry

“…19 Similarly, we applied this concept by extending the p-conjugation of the widely used dopant for organic light emitting diodes (OLED), 9,10bis(N,N-diarylamino)anthracene (5); distortion of the donor (N,N-diarylamine) plane destabilises the 1 ET state and the resultant mixing with the LE state enhances the oscillator strength of S 0 ' 1 CT fluorescence. 20 As mentioned above, torsional restrictions in D-A systems enable precise control over the proportion of the LE and ET character of the D-A system. Therefore, the pretwisting strategy must be effective when designing solvatochromic probes 15,21 and photoinduced electron transfer (PET) sensors, 22 in spite of the limited number of reports.…”

“…70 Recently, Adachi et al achieved fast and efficient blue TADF based on engineering of LE and CT states. 4 Since 1 CT and 3 CT corresponding to blue emissions lie at relatively high energy levels, the lowest triplet state (T 1 ) tends to become a 3 LE state and hamper reverse intersystem crossing from 3 CT. To solve the problem of blue TADF, they arranged pretwisted D-A junctions at appropriate positions (20) in order to destabilise the 3 LE state (Fig. 9b).…”

5,12‐Diaminotetracenes: The Impact of Orbital Interactions between the Acene π System and Amino Groups on Their Electronic States

“…9,10-Bis(diphenylamino)anthracenee mitted bright photoluminescence in solution, originating from charge-transfer excited states from the diphenylamine moietyt ot he anthracene core. [9][10][11] In addition, 9,10-bis(dimethylamino)anthracene exhibited solid-statef luorescencebehavior,whereas it did not exhibit fluorescence in solution. [12] Thus,a lkylamino-substituted anthracenes demonstrated several unique and beneficial features, such as bright solid-statef luorescence,t unable fluorescence emission, and large Stokes shifts.…”

Palladium‐Catalyzed N‐Arylation of Iminodibenzyls and Iminostilbenes with Aryl‐ and Heteroaryl Halides

“…On the other hand, only a handful of methods for the functionalization of the preexisting ring system have been reported. A few examples of the palladium‐catalyzed N‐arylation of iminodibenzyl and iminostilbene have appeared sporadically in the literature, generally with unfunctionalized aryl halide substrates, and high catalyst loadings are frequently employed (2–5 mol % Pd) ,,. Alternatively, Ullmann‐type conditions for N‐arylation requiring a stoichiometric copper promoter and high temperatures have also been utilized …”

“…Polycyclic aryl bromides also gave high yields under standard conditions ( 1 e – g ). Compound 1 f , prepared in excellent yield (96 %) employing the current method, has been shown to exhibit interesting photoluminescent properties as a consequence of its distorted framework . In comparison, its previous synthesis from identical starting materials by using 1,3‐bis(2,6‐Diisopropylphenyl)imidazol‐2‐ylidene](3‐chloropyridyl)palladium(II) dichloride ( PEPPSI‐IPr) as the Pd precatalyst (5 mol %) gave the coupling product in only 47 % yield.…”