Triarylborane‐Appended Anils and Boranils: Solid‐State Emission, Mechanofluorochromism, and Phosphorescence

Abstract

Herein, the design,s ynthesis, optical properties, and mechanofluorochromism characteristics of as eries of conjugates having covalently linked triarylborane (TAB) and anil/boranil units (TAB-anil: 1a-3a and TAB-boranil: 1-3)a re reported. The electronic interactions between TABa nd anil/ boranili n1a-3a and 1-3 were fine-tuned by changing the boryl moiety's positiono nt he phenyls pacer connecting the BMes 2 (Mes = mesityl)a nd anil/boranil units.Ab oryl moiety at the meta position(1a)o ft he phenyl spacers tabilizest he enolic form (E-OH), whereas ab oryl moiety at the para position (2a and 3a)s tabilizes the keto form (Z-NH) in the solid state.H owever,i ns olution 1a, 2a,a nd 3a exhibit keto-enol tautomerism in both ground and excited states.C ompounds 1a-3a and 1-3 show red-shifted absorption compared with 4a and 4,which are devoid of TABmoieties, which indicate effectivep articipation of an empty po rbital on the boronc enteri n1a-3a and 1-3.C ompounds 1 and 2 showed fluorescence variations in response to externals timuli such as mechanical grinding. Long phosphorescence lifetimes of 18-46 ms were observed for compounds 1-3.T he observed optical properties of 1a-3a and 1-3 are rationalized in the context of quantumm echanical calculations.

Circularly Polarized Fluorescent Helicene‐Boranils: Synthesis, Photophysical and Chiroptical Properties

“…Finally, intermolecular π-π stacking interactions (Figure 3b) are observed in the molecular packing of homochiral dimers. Note that the molecular geometry of H2 observed in its crystal structure may not necessarily be dominant in solution, as a careful analysis of the NOESY spectrum of this compound showed that the proton H 20 (of the CH=N imine) correlates with H 13 and H 14 (other extremity of the helicene) and with both H 1 and H 3 (see Figures S1.16a-b), thus suggesting the fast rotation around the C 2 À N (CÀ N 1 in Figure 3a) bound (in the NMR timescale). Similar conclusion holds also for H3, for which the analogous correlation of protons in the NOESY spectrum is seen (H 12 with H 1 , H 3 and H 4 , see Figures S1.37a-b).…”

“…The resulting novel helicenic boranils H1-H3 were then fully characterized by NMR and mass spectrometry (see Supporting Information). While the 1 H and 13 C NMR spectra display the typical, characteristic signals coming from both the helicene and boranil units, these compounds show very informative 11 B NMR and 19 F NMR (see Table 1 and Supporting Information). Indeed, H1 displays two chemically and magnetically equivalent fluorine atoms that resonate at À 136.5 ppm and demonstrate similar BÀ F coupling constants ( 1 J B-F = 17.3 Hz).…”

“…Boranils, another class of boron heterocycles derived from salicylaldanilinimines, possess an NÀ BÀ O connectivity and are particularly promising species due to their attractive optical features. [13] Following the pioneering work of Hohaus et al in 1973, [14] Ulrich, Ziessel et al reported in 2011 the facile twosteps preparation of boranils bearing donor/acceptor substituents, showing higher stability compared to their unsubstituted congeners and good luminescence properties in solution and solid states. [15] In addition, such compounds have the major advantage of being easily synthesized, even on a large-scale, from a variety of anilines or amines, including chiral ones.…”

Ultralong room temperature phosphorescence and ultraviolet fluorescence from simple triarylphosphine oxides

“…We have been involved in developing RTP materials for the last one decade. [33][34][35][72][73][74][75][76][77][78][79] As part of the ongoing program, we set to investigate the RTP characteristics of a series of simple triarylphosphines (1, 2, 3, and 4) and triarylphosphine oxides (5, 6, 7, and 8) to gain an understanding on how different are the lone pair electrons in R 3 P compared to arylphosphanediamines in the production of triplet excitons through np* transitions, and to understand the difference between R 3 P and R 3 P(O) based np* transitions in the production of triplet excitons. For this study, we synthesized a series of arylphosphines and arylphosphine oxides (Scheme 1).…”

Mechanofluorochromism of (D–π–)2A-type azine-based fluorescent dyes

“…In particular, the intermolecular MFC (inter-MFC) based on reversible changes in molecular orientation and arrangement of dye molecules is superior in durability to the intramolecular MFC (intra-MFC) based on reversible changes in the chemical structures of dye molecules by cleavage and reconstruction of chemical bonds during the grinding–heating process, and thus, the inter-MFC is expected to be applicable to rewritable photoimaging and electroluminescence devices. 8–70 Among various types of fluorescent dyes possessing the mechanofluorochromic properties, donor–π–acceptor (D–π–A)-type fluorescent dyes composed of an electron-donating moiety (D) and an electron-withdrawing moiety (A) connected by a π-conjugated bridge exhibit intense photoabsorption and fluorescence emission properties based on the intramolecular charge transfer (ICT) excitation from the D moiety to the A moiety. 11–33 Thus, the dipole moments as well as photoabsorption ( i.e.…”