Synthesis, photophysical and electronic properties of tetra-donor- or acceptor-substitutedortho-perylenes displaying four reversible oxidations or reductions
“…A large number of air-stable conjugated three-coordinate organoboron compounds have been synthesized over the last few decades [1][2][3][4][5][6][7][8] for various applications, particularly in linear [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and nonlinear [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] optics, electro-optic devices, [40][41][42] anion sensors, [43,44] cell imaging, [45][46][47][48] etc. The boron center in these species possesses an empty p-orbital and can thus serve as a strong π-acceptor following photo-excitation, or as a readily reducible center.…”
The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4‐D−C6H4−B(Ar)2 (D=tBu or NPh2; Ar=mesityl (Mes) or 2,4,6‐tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state‐of‐the‐art DFT and TD‐DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4‐tBu−C6H4−B(Fmes)2 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert‐butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.
“…A large number of air-stable conjugated three-coordinate organoboron compounds have been synthesized over the last few decades [1][2][3][4][5][6][7][8] for various applications, particularly in linear [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and nonlinear [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] optics, electro-optic devices, [40][41][42] anion sensors, [43,44] cell imaging, [45][46][47][48] etc. The boron center in these species possesses an empty p-orbital and can thus serve as a strong π-acceptor following photo-excitation, or as a readily reducible center.…”
The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4‐D−C6H4−B(Ar)2 (D=tBu or NPh2; Ar=mesityl (Mes) or 2,4,6‐tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state‐of‐the‐art DFT and TD‐DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4‐tBu−C6H4−B(Fmes)2 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert‐butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.
“…The syntheseso ft he compounds (DPA)-Per, (DPA) 2 -Per and (DPA) 3 -Per are summarized in Scheme 1. We used the same startingp oint for the synthesis of the new derivatives as for our previouslyr eported [30] tetra-substituted ortho perylene (DPA) 4 -Per,w hich is the high yielding, regioselective Ir-catalyzed CÀHb orylation of perylene.I no rder to obtain the mono-, di-, and tri-borylated derivatives, the number of equiva-lents of B 2 pin 2 was reduced from 5t o1 .T hus, am ixture of Bpin-Per, (Bpin) 2 -Per, (Bpin) 3 -Per ands ome (Bpin) 4 -Per was obtained. The mono-a nd di-borylated products were successfully separated by column chromatography.T wo furtherr egioisomerso f(Bpin) 2 -Per are possible, namely 2,5-bis(Bpin)-perylenea nd 2,11-bis(Bin)-perylene.H owever,t hese two isomers could not be isolated, whereas 2,8-bis(Bpin)-perylene ((Bpin) 2 -Per)w as isolated successfully.F or the follow-up reactions, the tri-borylated perylene, in contrast, was used as amixture containing some residual di-borylatedp erylene.…”
Section: Synthesismentioning
confidence: 99%
“…Medium [30] the third and fourth oxidations of (DPA) 4 -Per are quite close to each other; therefore, we previously conducted af urther measurement using the weakly coordinating anion (WCA)-containing electrolyte [nBu 4 N][Al(OC(CF 3 ) 3 ) 4 ]t hat is known to separatec harged speciesbetter in electrochemical studies. Hence, four reversible oxidations at 0.04, 0.24, 0.41 and 0.51 Vw ith respect to Fc/Fc + were detected.…”
Section: Electrochemistrymentioning
confidence: 99%
“…Hence, four reversible oxidations at 0.04, 0.24, 0.41 and 0.51 Vw ith respect to Fc/Fc + were detected. [30] Thus, we now have as eries of perylene derivatives which allows one to tune the electrochemical properties dependingo nt he requirements of ap articular application.…”
We synthesized a series of new mono‐, di‐, tri‐ and tetra‐substituted perylene derivatives with strong bis(para‐methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11‐positions. The properties of our new donor‐substituted perylenes were studied in detail to establish a structure‐property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)‐Per possesses one reversible oxidation while (DPA)4‐Per has four. The mono‐ and di‐substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83.
“…The relevance of boron in these systems is due to the empty p z ‐orbital on boron that can act as an electron acceptor (A) in conjugated systems. Based on this, potential applications of three‐coordinate boron have been investigated, such as for linear and non‐linear optics, bioimaging, sensors, frustrated Lewis pairs (FLPs), and organic light‐emitting diodes (OLEDs) . The drawback of the employment of three‐coordinate boron in conjugated systems, however, is their inherent reactivity towards nucleophiles, such as water, due to the empty p z ‐orbital.…”
We observed a surprisingly high electronically driven regioselectivity for the iridium‐catalyzed C−H borylation of donor‐π‐acceptor (D‐π‐A) systems with diphenylamino (1) or carbazolyl (2) moieties as the donor, bis(2,6‐bis(trifluoromethyl)phenyl)boryl (B(FXyl)2) as the acceptor, and 1,4‐phenylene as the π‐bridge. Under our conditions, borylation was observed only at the sterically least encumbered para‐positions of the acceptor group. As boronate esters are versatile building blocks for organic synthesis (C−C coupling, functional group transformations) the C−H borylation represents a simple potential method for post‐functionalization by which electronic or other properties of D‐π‐A systems can be fine‐tuned for specific applications. The photophysical and electrochemical properties of the borylated (1‐(Bpin)2) and unborylated (1) diphenylamino‐substituted D‐π‐A systems were investigated. Interestingly, the borylated derivative exhibits coordination of THF to the boronate ester moieties, influencing the photophysical properties and exemplifying the non‐innocence of boronate esters.
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