Solution- and Solid-State Luminescent Borate Complexes Based on a Substituted π-Conjugated...

Job/Unit: O42806 /KAP1 Date: 26-09-14 12:55:45 Pages: 10

FULL PAPER

DOI: 10.1002/ejoc.201402806

Solution- and Solid-State Luminescent Borate Complexes Based on aSubstituted π-Conjugated 2-(6�-Hydroxy-5�-benzofuryl) Scaffold

Karima Benelhadj,[a] Julien Massue,*[a] Pascal Retailleau,[b] Siwar Chibani,[c]

Boris Le Guennic,[d] Denis Jacquemin,*[c,e] Raymond Ziessel,*[a] and Gilles Ulrich*[a]

Keywords: Fluorescence / Luminescence / Dyes/Pigments / Density funtional calculations / Borates

This paper describes the synthesis of π-conjugated fluoro-phores based either on an anil or a benzoxazole scaffold in-corporating a rigid 2-(6�-hydroxy-5�-benzofuryl) fragment.Their subsequent coordination to a BF2 motif led to highlyluminescent BIII complexes called boranils or HBBO boratecomplexes, respectively. All the new compounds were char-acterized by NMR spectroscopy, mass spectrometry, and ele-mental analysis. The study of their optical properties in solu-tion revealed two distinct photophysical behaviors de-pending on the substitution. Complexes bearing a strongelectron-donating p-nBu2NC6H4 group displayed a markedinternal charge transfer (ICT) leading to a pronounced

Introduction

There has been extensive research into the developmentof single compounds displaying both solution- and solid-state emission because these key materials lie at the cross-roads of a wide range of applications for optoelectronic andbiomedical devices.[1] Several recent advances, by masteringthe molecular design of these fluorescent dyes, have led tothe improvement of a wide range of technologies, such asorganic light-emitting diodes (OLEDs), organic field-effecttransistors (OFETs), organic solid-state lasers, as well asfluorescent sensors and probes, and various luminescentdisplays.[2] The main challenge in this field is that the large

[a] Institut de Chimie et Procédés pour l’Énergie, l’Environnementet la Santé (ICPEES), LCOSA, UMR CNRS 7515, ECPM,25 Rue Becquerel, 67087 Strasbourg Cedex 02, FranceE-mail: [email protected]

[email protected]@unistra.fr

[b] Laboratoire de Cristallochimie, ICSN – CNRS,Bât 27-1 avenue de la Terrasse, 91198 Gif-sur-Yvette, Cedex,France

[c] Laboratoire CEISAM, UMR CNRS 6230,2 rue de la Houssinière, 44322 Nantes Cedex 3, FranceE-mail: [email protected]

[d] Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS –Université de Rennes 1,263, Av. du Général Leclerc, 35042 Rennes Cedex, France

[e] Institut Universitaire de France (IUF),103 Boulevard Saint-Michel, 75005 Paris Cedex 05, Francehttp://www.sciences.univ-nantes.fr/CEISAM/ceisam.phpSupporting information for this article is available on theWWW under http://dx.doi.org/10.1002/ejoc.201402806.

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solvatochromism with λem ranging from 507 to 663 nm andquantum yields of up to 87%. Alternatively, borate com-plexes functionalized with p-tBuC6H4 or p-OMeC6H4 dis-played fluorescence in the visible range that is not influencedby the nature of the solvent. Although the emission of theboranils was quenched in the solid state, HBBO borate com-plexes displayed intense fluorescence from 489 to 567 nmand quantum yields of up to 23%. Finally, the excited statesof a selection of borate complexes were modeled by usingtime-dependent DFT, which allowed calculation of the dipolemoments of the dyes in their excited states.

majority of π-conjugated dyes are highly emissive in solu-tion but very weakly emissive in the solid-state because ofstrong intermolecular π–π interactions in the molecularpacking that lead to efficient luminescence quenchingthrough nonradiative processes. This is especially the casefor the well-known boron–dipyrromethene (BODIPY)dye,[3] which exhibits outstanding photophysical propertiesin the solution state (sharp absorption and emission profilesspanning from the visible to the near-IR, high molecularabsorption coefficient, and a quantum yield reaching up tounity) but emits weakly in the solid state. The luminescenceof BODIPY is strongly quenched in the solid state due tovery tight packing combined with a small Stokes’ shift thatleads to self-quenching through energy transfer. A strategyfor transferring its appealing optical properties to the solidstate, largely developed only recently, is to decorate the pe-riphery of the BODIPY core with bulky substituents suchas arylsilyl groups,[4] adamantyl,[5] diphenylaminocarb-azole,[6] or dimesitylboryl[7] among others.[8] Another popu-lar strategy is the introduction of aggregation-induced emis-sive motifs such as tetraphenylethene (TPE) or hexaphen-ylsilole, which induce a strong emission in the solid state atthe expense of fluorescence in solution in which molecularrotation leads to enhanced nonradiative rates.[9] To compen-sate the lack of solid-state luminescence of BODIPY, alter-native boron-containing dyes have been engineered to in-trinsically exhibit a sizeable emission in the aggregated statealong with an improved Stokes’ shift.[10] Different new fam-ilies of unsymmetrical π-conjugated dyes based on an


J. Massue, D. Jacquemin, R. Ziessel, G. Ulrich et al.FULL PAPERN∧N[11] or N∧O[12] chelating unit have been reported to1) form stable BIII complexes with BF2 or BAr2 fragmentsand 2) display intense solid-state emission. For example,Aprahamian and co-workers have reported BF2–hydrazoneadducts as efficient solid-state emitters.[13] Rigidification ofthe nonemissive hydrazone core with BIII fragments leadsto quantum yields of up to 0.52 in the aggregated state. Thegood planarity of the π-conjugated scaffold combined withdiminished π–π intermolecular interactions and enhancedStokes’ shifts (largely achieved by an unsymmetrical molec-ular structure) seem to be at the origin of a high solid-statequantum yield. These trends have been confirmed in severalother examples, including pyridomethene–BF2 com-plexes,[14] phenanthro[9,10-d]imidazole-quinoline–BF2

dyes,[15] naphthyridine–BF2[16] or β-iminoenamine–BF2

[17]

complexes just to cite but a few. In all cases, the emissionin the solid state is characterized by a modest-to-strong red-shift compared with that in solution. Our group has beeninterested in developing π-conjugated fluorophores con-structed around various N∧O chelates derived from 2-(6�-hydroxy-5�-benzofuryl)benzoxazole (HBO)[18] or aniline-amine (anil)[19] skeletons derived from Schiff bases[20].These dyes exhibit intrinsic fluorescence due to an efficientexcited-state intramolecular proton transfer (ESIPT)[21] butare also excellent chelates of BIII fragments leading tohighly luminescent tetrahedral HBO–borate complexes orboranils, respectively (Figure 1, a). These complexes displaysignificant emission spanning from the UV to the yellow/orange part of the visible region. Furthermore, in the caseof the HBO–borate complexes, extending the conjugationwith ethynyl substituents allows different photophysical be-haviors to be obtained, depending on the position on thephenolate core [weak-to-strong intramolecular chargetransfer (ICT) or purely singlet emitters].[22] Some of thesecomplexes have proven to be good solid-state emitters eitherin a KBr matrix or as luminescent crystals. In this context,we report herein the synthesis, structural and optical prop-erties, and ab initio calculations of a series of new N∧Ochelates based on a substituted 2-(6�-hydroxy-5�-benzo-furyl)benzoxazole scaffold (HBBO) and demonstrate that

Figure 1. General structures of (a) the 2-(6�-hydroxy-5�-benzo-furyl)benzoxazole (HBO)–borate complex and boranil and (b) the2-(6�-hydroxy-5�-benzofuryl)benzoxazole (HBBO)–borate complexand substituted boranils studied in this article. R and R� representelectron-withdrawing and -donating groups, respectively.

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these scaffolds are excellent chelates for BF2 fragments lead-ing to highly fluorescent solution- and solid-state materials(Figure 1, b).

Results and Discussion

The synthetic routes for the preparation of the boranilderivatives 5–8 and HBBO borate complexes 12–14 are out-lined in Scheme 1. The starting salicylaldehyde buildingblocks were synthesized in two steps according to a re-ported procedure.[23] The anil derivatives 1–4 were readilyprepared by using commercially available 4-substituted anil-ines in ethanol at reflux with catalytic amounts of pTsOH.The desired anils precipitated out of the medium and wereobtained pure after filtration in yields of 47–90 %. Subse-quent boron complexation was achieved by using an excessof BF3·Et2O in 1,2-dichloroethane in the presence of N,N-diisopropylethylamine (DIEA) as base. Boranils 5–8 werethen obtained as orange-red powders after filtrationthrough a basic alumina column in yields of 48–91%.

HBBO derivatives 9–11 were prepared by two syntheticroutes. HBBOs 9 and 10 were obtained by heating the start-ing salicylaldehyde at reflux with 1 equiv. of 4-tBu-2-amino-phenol in ethanol followed by an oxidative cyclization using2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). As aresult of its oxidation-sensitive nature, the synthesis ofHBBO 11 required the use of potassium cyanide in the pres-ence of phenylboronic acid and 1 equiv. of the relevant 2-aminophenol to promote oxidative cyclization in methanolat reflux.[23] It is noteworthy that all the HBBOs 9–11 ex-hibit strong solid-state fluorescence, detected by the nakedeye, when irradiated with a bench UV lamp as a result ofan intrinsic ESIPT process.[24] Dropwise addition of an ex-cess of BF3·Et2O to solutions of 9–11 in anhydrous 1,2-dichloroethane in the presence of DIEA as base led tostraightforward boron complexation at the N∧O chelatingsite. Pure HBBO borate complexes 12–14 were purified byfiltration through a basic Al2O3 column, eluting withCH2Cl2. The complexation reactions for all complexes canbe readily monitored by 1H NMR spectroscopy by as-sessing the loss of the hydrogen-bonded phenolic protonsignal (δ = 10–12 ppm). All new compounds, including anils1–4, boranils 5–8, and HBBO borate complexes 12–14 wereunambiguously characterized by 1H and 13C NMR spec-troscopy as well as mass spectrometry and elemental analy-ses. As representative examples, the 1H NMR spectra ofboranil 5 and HBBO borate 14 are presented in Figure 2.Apart from the typical aliphatic 1H signals of the N-n-butylfragments, distinctive aromatic protons can be seen in thesespectra. In addition, the imine proton in 5 resonates at8.4 ppm and the proton on the furan cycle can be found ataround 6.7 ppm for both complexes 5 and 14. The 13CNMR spectra are also in good agreement with expectedsignals for tertiary and quaternary carbons (see the Sup-porting Information).


Solution- and Solid-State Luminescent Borate Complexes

Scheme 1. Synthesis of HBBO borate complexes 5–8 and boranils 12–14.

X-ray Structures

Single crystals of the HBBO borate complex 13 suitablefor X-ray analysis were obtained by the slow diffusion of n-pentane into a concentrated dichloromethane solution. Itsmolecular structure is represented in Figure 3.

HBBO borate complex 13 features a structure that is20 Å in length with the aromatic rings appearing slightlycurved, in keeping with reported HBO borate complex-es.[18a,22a] The boron atom has a distorted tetrahedral geom-etry with angles ranging from 107.6(3) to 111.7(3)°. The B–O and B–N distances are similar to those formerly ob-served: 1.432(5) versus 1.44 Å and 1.584(5) versus1.59 Å.[22a]

Photophysical Properties

The photophysical data for boranils 5–8 and HBBO bor-ate complexes 12–14 in various solvents are presented inTable 1. The absorption and emission spectra of boranils 5–8 in cyclohexane and toluene are presented in Figure 4 andthose of the HBBO borate complexes 12 and 13 in dichloro-methane are shown in Figure 5. Finally, the optical spectraof the HBBO borate complex 14 in different solvents arepresented in Figure 6.

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The absorption spectra of all the BIII complexes showsimilar trends, that is, a broad, unstructured band the maxi-mum wavelength of which ranges from 382 to 486 nm withmolar absorption coefficients ranging from 12200 to45000 m–1 cm–1. Moreover, these absorption bands appearin the UV region and do not seem to shift significantly insolvents of different polarity. In addition, intense absorp-tion bands are observed in the higher-energy range indica-tive of individual π–π* transitions in the aromatic cycles.Irradiation at the wavelength of the lowest-energy bandleads to an intense emission band in the visible region forall dyes. For boranil dyes 5–8, the emission maximum wave-length spans from 585 to 633 nm (Φ = 6–31%) whereas forthe HBBO borate dyes 12–14, the emission peaks rangefrom 458 to 663 nm (Φ = 3–87%).

Interestingly, for boranil dyes 5–8, which are all function-alized by a strong electron-donating p-(dibutylamino)-phenyl as a terminal group at one end, the emission doesnot seem to be highly dependent on the functionalizationat the other end. This effect is less pronounced in apolarsolvents like cyclohexane in which substitution of the iodinein 5 by an electron-attracting cyano group in 7 leads to asubstantial bathochromic shift (λem = 605 nm for 5 vs. λem

= 632 nm for 7).


J. Massue, D. Jacquemin, R. Ziessel, G. Ulrich et al.FULL PAPER

Figure 2. 1H NMR spectra of (a) boranil 5 and (b) HBBO borate complex 14 in CDCl3 at room temperature along with expansions ofthe aromatic regions (right).

Figure 3. Top: ORTEP diagram of the HBBO borate complex 13showing the atom-labelling scheme. Thermal ellipsoids are drawnat the 50% level. Bond lengths [Å] and angles [°]: B1–N1 1.584(5),B1–O4 1.432(5), C1–N1 1.308(3), O4–C9 1.344(3), F1–B1–F2109.8(3), F1–B1–O4 111.1(3), F1–B1–N1 108.1(3), F2–B1–O4111.7(3), F2–B1–N1 107.6(3), O4–B1–N1 108.4(3). Bottom: Or-thogonal view of the above diagram highlighting the planarity ofthe molecule.

An increase in the dipole moment of the solvent is corre-lated with a bathochromic shift of the emission maximumwavelength along with a rapid decrease in the quantumyield, which is indicative of strong intramolecular chargetransfer (ICT). Although in toluene the quantum yield var-ies between 6 and 19% for dyes 5–8, the fluorescence emis-


sion is completely quenched in dichloromethane. To experi-mentally confirm the hypothesis of a strong ICT, we mea-sured the emission after bubbling HCl(g) into the solution(see also calculations below). A pronounced hypsochromicshift was observed for both the absorption and emissionbands along with an increase in the quantum yield (13–25 %). All these observations highlight the strong ICT char-acter of the emission of the boranil dyes 5–8, as also re-flected by the shape of their emission bands. In the absenceof a terminal p-(dibutylamino)phenyl group, HBBO boratecomplexes 12 and 13, bearing tBu and OMe end-groups,respectively, display similar photophysical behavior (Fig-ure 5). The emission spectra exhibit a single blue-greenemission band (λem = 458 and 471 nm in toluene for 12 and13, respectively), which is largely insensitive to the natureof the solvent, with improved quantum yields (Φ = 32–58%) as compared with those recorded for boranil dyes 5–8.

Moreover, 12 and 13 exhibit emission bands that arenearly mirror images of their absorption bands and featurereduced Stokes’ shifts (ΔSS; around 4000 cm–1 vs. an averageof 6000 cm–1 for the other borate complexes), consistentwith a weakly polarized excited state. Interestingly, HBBOborate complex 14 exhibits different photophysical behaviorto the analogous dyes 12 and 13. Indeed, the presence ofthe strongly electron-donating p-dibutylaminophenyl group



Table 1. Selected optical data measured in solution.

Dye λabs εmax λem ΔSS Φf[a] τ Solvent

[nm] [m–1 cm–1] [nm] [cm–1] [ns]

5 469 15100 605 4800 0.23 1.8 cyclohexane467 15900 632 5600 0.10 2.0 toluene471 14900 [b] – – – CH2Cl2413 16000 548 6000 0.25 3.7 CH2Cl2 +

HCl(g)


HCl(g)


HCl(g)


HCl(g)

12 386 45000 458 4100 0.32 2.6 toluene387 44300 465 4300 0.48 3.2 CH2Cl2

13 393 23800 471 4200 0.52 3.4 toluene392 25500 479 4600 0.58 4.5 CH2Cl2

14 419 29800 507 4100 0.87 4.6 toluene417 28300 579 6700 0.47 5.9 CH2Cl2382 32100 447 3800 0.43 1.6 CH2Cl2 +

HCl(g)

422 29300 584 6600 0.30 5.7 THF412 27100 663 9200 0.03 0.8 CH3CN

[a] Quantum yields determined in solution using quinine sulfate asreference, Φ = 0.55, in 1 n H2SO4, λex = 366 nm for dyes emittingbelow 480 nm, Rhodamine 6G, Φ = 0.88, in ethanol, λex = 488 nmfor dyes emitting between 480 and 580 nm, cresyl violet, Φ = 0.55,λex = 546 nm in ethanol for dyes emitting above 580 nm. [b] Non-fluorescent.

induces a strong polarization of the excited state, as evi-denced by the pronounced solvatochromism observed insolution (Figure 6). The broad emission band appears overa wide range of wavelengths, from 507 nm in toluene to663 nm in CH3CN with quantum yields ranging from 3 to87%. Note that dye 14 in THF luminesces in the range of480 to 780 nm, which is very unusual for this type of dye.The quantum yield measured in toluene (Φ = 87 %) is, tothe best of our knowledge, one of the highest reported forborate complexes derived from HBO. The emission spec-trum of 14 was also recorded in CH2Cl2 after bubblingHCl(g) through the solution. Because ICT no longer occursdue to protonation of the nitrogen atom lone pair of thenitrogen atom, a significant hypsochromic shift is observedin dichloromethane (λem = 579 nm in CH2Cl2 vs. 447 nmafter protonation).

The HBBO borate complexes 12–14 also display solid-state fluorescence, detected by the naked eye, under a benchUV lamp (λexc = 365 nm). We decided therefore to fullyinvestigate their photophysical properties in the solid state.The crystalline powders were dispersed in KBr pellets(≈10–6 m) and their emission and excitation spectra re-corded. The optical data are presented in Table 2 and the


Figure 4. Absorption (grey) and emission (black) spectra of boran-ils 5–8 in cyclohexane (top) and toluene (bottom) at room tempera-ture.

Figure 5. Absorption (grey) and emission (black) spectra of HBBOborate complexes 12 (solid line) and 13 (dashed line) in dichloro-methane at room temperature.

Figure 6. Emission spectra of HBBO borate complexes 14 in vari-ous solvents at room temperature.


J. Massue, D. Jacquemin, R. Ziessel, G. Ulrich et al.FULL PAPERemission spectra in Figure 7. The emission profiles followthe same trends as those observed in the solution state, thatis, they each exhibit a broad, unstructured emission bandin the visible region with a maximum wavelength at 489,542, and 567 nm for 12–14, respectively. The quantumyields calculated with a spectrometer fitted with an integra-tion sphere range from 19 to 23 % (Table 2), consistent withthose already reported for similar borate complexes.[18b,22a]

Table 2. Optical data measured in the solid-state in KBr pellets.

Dye λexc λem ΔSS Φf[a] x; y (CIE 1931)

[nm] [nm] [cm–1]

12 397 489 4700 0.23 0.225; 0.42413 388 542 7300 0.20 0.346; 0.54414 365 567 9800 0.19 0.507; 0.515

[a] Absolute quantum yields were determined by using an integra-tion sphere.

Figure 7. Solid-state emission spectra of HBBO borate complexes12–14 in KBr pellets.

Ab Initio Calculations

To complement the experimental analysis and to gain abetter understanding of the excited-state features, we mod-eled the excited-state properties of 12–14 by using time-de-pendent density functional theory (TD-DFT; see the Exp.Sect. for computational details). Our data are collected inTable 3 and the density difference plots obtained for thethree dyes are presented in Figure 8.

Table 3. Selected computational results for dyes 12–14.

Dye λabs λem ΔSS dCT[a] μGS

[b] μES[c] Solvent

[nm] [nm] [cm–1] [Å] [D] [D]

12 346 409 4440 2.33 7.8 9.7 toluene343 414 5012 2.56 8.9 10.9 CH2Cl2

13 350 415 4490 2.61 6.5 10.2 toluene347 423 5191 2.86 7.4 11.4 CH2Cl2

14 362 432 4521 3.26 8.9 15.3 toluene361 450 5478 3.63 10.0 17.3 CH2Cl2

[a] dCT is the ICT distance. [b] μGS is the ground-state dipole. [c]μES is the excited-state dipole.

In comparison with the data presented in Table 1, it isclear that the theoretical wavelengths are too small, as ex-pected. (see Exp. Sect.). However, the major trends are wellreproduced by theory. Indeed, we note that 1) λabs is almostinsensitive to solvent, 2) the successive auxochromic effectson going from 12 to 13 and next to 14 are –0.04 and–0.12 eV, which compares well with the values of –0.06 and


Figure 8. PCM(Tol)-ωB97X-D/6-311+G(2d,p) density differenceplots obtained for 12–14 (from top to bottom). Blue (red) regionsindicate decrease (increase) in the electron density upon transition.A contour threshold of 0.004 a.u. was used.

–0.20 eV (absorption in toluene), 3) the fluorescence wave-lengths are more sensitive to the polarity of the solvent, and4) the Stokes’ shifts are in line with the experimental values,with a maximal value for 14 in dichloromethane (5478 vs.6700 cm–1 experimentally). From Figure 8, it is evident thatthe benzoxazole side acts as an electron acceptor (mostly inred), whereas the phenyl ring bonded to the benzofuran actsas a donor (mostly in blue). The dialkylamino group in 14increases the electron density of this side of the dye, andconsequently yields a stronger ICT. This qualitative trendis also confirmed by the charge distance (dCT) and dipolemoments listed in Table 3: For 12 and 13, the value of dCT

is 2.6� 0.3 Å, whereas it is significantly larger in 14. Wealso notice larger dipole moments for the latter compound,especially in the excited state (17 D in dichloromethane),which is consistent with the strong solvatochromism of theexperimental fluorescence wavelength in 14.

Conclusions

We have reported in this article the synthesis and struc-tural and optical properties of a range of borate complexesbased on either an anil or HBBO skeleton. The solution-state photophysical investigations have revealed differentbehavior, depending on the substitution on the core of thedyes. Whenever the mesomeric electron-donating p-nBu2NC6H4 is present, a strong ICT is evidenced leadingto pronounced solvatochromism of the emission. Thefluorescence maximum wavelength then spans from 505 to603 nm with quantum yields reaching up to 87 %, one ofthe highest reported in the literature for similar dyes. TheICT seems to be stronger in boranils than in the HBBOborate complexes, leading to fluorescence quenching in



dichloromethane. Fluorescence can be restored upon pro-tonation of the lone electron pair of the nitrogen, furtherproving the CT nature of the transition. Borate complexeswith less donating groups (tBu, OMe) display fluorescencecentered at around 460–480 nm, and the emission does notseem to be sensitive to the environment. The HBBO boratecomplexes 12–14 also display solid-state luminescence whenembedded in a KBr matrix with quantum yields reaching23%. Finally, TD-DFT modeling of the excited-state prop-erties of 12–14 confirmed the ICT nature of the emissionin the HBBO borate complex 14 through the calculation ofa significantly larger dipole moment in the excited statethan for 12 and 13.

Experimental SectionGeneral Methods and Equipment: All reactions were performed un-der dry argon using standard Schlenk techniques. All chemicalswere received from commercial sources (Aldrich, Alfa Aesar) andused without further purification. Dichloromethane was distilledfrom P2O5 under argon. TLC was performed on silica gel or alu-minium oxide (Al2O3) plates coated with fluorescent indicator.Chromatographic purifications were conducted by using 40–63 μmsilica gel or basic aluminium oxide. All solvent mixtures are givenas v/v ratios. The 300 (1H), 400 (1H), 75.46 (13C), 100.3 (13C), and128.38 (11B) MHz NMR spectra were recorded at room tempera-ture with perdeuteriated solvents; the residual protonated solventsignals were used as internal references. Mass spectra were recordedwith an ESI-MS mass spectrometer. Electronic absorption andemission spectra were recorded under ambient conditions by usingcommercial instruments. UV/Vis spectra were recorded with a dual-beam grating spectrophotometer with a 1 cm quartz cell. Fluores-cence spectra were recorded with a spectrofluorimeter. The solventsused for spectroscopy were spectroscopic grade and used as re-ceived. All fluorescence spectra were corrected from the local re-sponse of the photomultiplier. Luminescence lifetimes were mea-sured by means of a spectrofluorimeter using software with time-correlated single-photon mode coupled to a stroboscopic system.The excitation source was a laser diode (λ = 320 nm). The instru-ment response function was determined by using a light-scatteringsolution (LUDOX). The fluorescence quantum yields (Φexp) werecalculated from Equation (1) in which I denotes the integral of thecorrected emission spectrum, OD is the optical density at the exci-tation wavelength, and η is the refractive index of the medium. Thereference systems used were quinine, Φ = 55 % in 1 n H2SO4, λexc

= 366 nm for dyes emitting below 480 nm, Rhod-amine 6G, Φ = 88% in ethanol, λexc = 488 nm for dyes emittingbetween 480 and 570 nm, and cresyl violet, Φ = 55%, λexc = 546 nmin ethanol, for dyes emitting above 570 nm. Absorption spectrawere recorded with a Shimadzu UV-3600. Fluorescence spectro-scopic studies (emission/excitation spectra, quantum yield determi-nation) were performed with a Horiba Jobin Yvon Fluoromax 4spectrophotometer. Lifetimes were determined by using an Edin-burgh Instrument FL-900 with a TCSPC card.

(1)

Syntheses: All reagents were used directly as obtained commerciallyunless otherwise noted. Data for compounds 9–11 can be found inref.[23]


General Procedure for the Synthesis of Anils 1–4: 2-[4-(Dibut-ylamino)phenyl]-6-hydroxybenzofuran-5-carbaldehyde (1 equiv.)was added to a solution of 4-substituted aniline (1 equiv.) andpTsOH (few crystals) in dry ethanol. The resulting solution washeated at reflux overnight. After cooling, the desired anil com-pounds precipitated from solution and were then filtered, washedwith ethanol and pentane, and dried under vacuum.

Anil 1: Red powder, yield 82%. 1H NMR (300 MHz, CDCl3): δ =13.23 (s, 1 H, OH), 8.64 (s, 1 H, CH imine), 7.73 (d, J = 8.6 Hz, 2H, CH Ar), 7.64 (d, J = 8.4 Hz, 2 H, CH Ar), 7.45 (s, 1 H, CHAr), 7.09–7.02 (m, 3 H, CH Ar), 6.69–6.66 (m, 3 H, CH Ar), 3.17(t, J = 7.3 Hz, 4 H, NCH2), 1.65–1.56 (m, 4 H, CH2), 1.44–1.32(m, 4 H, CH2), 0.97 (t, J = 7.3 Hz, 6 H, CH3) ppm. 13C NMR(75 MHz, CDCl3): δ = 163.4, 159.4, 158.2, 157.8, 148.5, 138.6,126.3, 123.9, 123.3, 117.0, 116.1, 111.6, 111.4, 99.0, 96.6, 91.0, 50.9,29.6, 20.5, 14.1 ppm. MS (EI): m/z = 566.1. C29H31IN2O2 (566.48):calcd. C 61.49, H 5.52, N 4.95; found C 61.32, H 5.37, N 4.78.

Anil 2: Orange powder, yield 90%. 1H NMR (300 MHz, CDCl3):δ = 13.18 (s, 1 H, OH), 8.45 (s, 1 H, CH imine), 7.47 (d, J = 8.9 Hz,2 H, CH Ar), 7.29 (s, 1 H, CH Ar), 7.10–7.06 (m, 2 H, CH Ar),6.96–6.90 (m, 3 H, CH Ar), 6.55–6.49 (m, 3 H, CH Ar), 3.17 (t, J= 7.7 Hz, 4 H, NCH2), 1.41–1.51 (m, 4 H, CH2), 1.29–1.17 (m, 4H, CH2), 0.83 (t, J = 7.2 Hz, 6 H, CH3) ppm. 13C NMR (75 MHz,CDCl3): δ = 163.2, 162.8, 151.0, 159.3, 158.0, 157.7, 148.5, 145.0,144.9, 126.2, 123.8, 123.1, 122.7, 122.6, 117.2, 116.4, 116.1, 111.7,111.7, 99.1, 97.0, 51.0, 29.6, 20.5, 14.1 ppm. MS (EI): m/z = 458.1.C29H31FN2O2 (458.57): calcd. C 75.96, H 6.81, N 6.11; found C75.74, H 6.64, N 5.88.

Anil 3: Red powder, yield 47%. 1H NMR (300 MHz, CDCl3): δ =12.87 (s, 1 H, OH), 8.66 (s, 1 H, CH imine), 7.71 (d, J = 8.6 Hz, 2H, CH Ar), 7.66 (d, J = 8.7 Hz, 2 H, CH Ar), 7.48 (s, 1 H, CHAr), 7.34 (d, J = 8.6 Hz, 2 H, CH Ar), 7.10 (s, 1 H, CH Ar), 6.73–6.65 (m, 3 H, CH Ar), 3.35–3.30 (m, 4 H, NCH2), 1.65–1.56 (m, 4H, CH2), 1.44–1.32 (m, 4 H, CH2), 0.97 (t, J = 7.3 Hz, 6 H,CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 165.2, 159.5, 158.7,158.1, 152.8, 133.7, 126.3, 124.4, 123.6, 122.2, 118.9, 115.9, 111.7,109.9, 99.3, 96.8, 51.0, 29.5, 20.5, 14.1 ppm. MS (EI): m/z = 465.2.C30H31N3O2 (465.59): calcd. C 77.39, H 6.71, N 9.03; found C77.14, H 6.52, N 8.77.

Anil 4: Red powder, yield 88%. 1H NMR (300 MHz, CDCl3): δ =13.44 (s, 1 H, OH), 8.64 (s, 1 H, CH imine), 7.64 (d, J = 8.9 Hz, 2H, CH Ar), 7.44 (s, 1 H, CH Ar), 6.68 (d, J = 8.9 Hz, 2 H, CHAr), 6.65 (s, 1 H, CH Ar), 6.53 (s, 2 H, CH Ar), 3.91 (s, 6 H,OCH3), 3.89 (s, 3 H, OCH3), 3.39–3.29 (m, 4 H, NCH2), 1.65–1.55(m, 4 H, CH2), 1.44–1.32 (m, 4 H, CH2), 0.98 (t, J = 7.3 Hz, 6 H,CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 162.2, 159.2, 157.9,157.6, 153.9, 148.5, 144.6, 137.1, 126.2, 123.7, 123.1, 117.1, 116.1,111.6, 99.0, 98.6, 96.9, 61.1, 56.3, 50.8, 29.6, 20.4, 14.1 ppm. MS(EI): m/z = 530.2. C32H38N2O5 (530.66): calcd. C 72.43, H 7.22, N5.28; found C 72.17, H 6.91, N 5.04.

General Procedure for the Synthesis of Boranils 5–8 and HBBOBorates 12–14: BF3·OEt2 (6 equiv.) was added to a solution of anilor HBBO (1 equiv.) in distilled 1,2-dichloroethane and stirred for20 min at room temperature. Then DIEA (6 equiv.) was added andthe solution was heated at reflux at 85 °C overnight. After cooling,the reaction mixture was washed with a saturated solution ofNaHCO3 and extracted with dichloromethane. The organic layerswere dried with MgSO4 and the solvent evaporated under vacuum.The product was filtered through a column of basic alumina elutingwith dichloromethane. Pure boranils or HBBO borate complexeswere obtained as yellow to red powders after evaporation of thesolvent in vacuo.


J. Massue, D. Jacquemin, R. Ziessel, G. Ulrich et al.FULL PAPERBoranil 5: Red powder, yield 82%. 1H NMR (300 MHz, CDCl3): δ= 8.41 (s, 1 H, CH imine), 7.82 (d, J = 8.7 Hz, 2 H, CH Ar), 6.65(d, J = 8.7 Hz, 2 H, CH Ar), 7.53 (s, 1 H, CH Ar), 7.31 (d, J =8.7 Hz, 2 H, CH Ar), 7.17 (s, 1 H, CH Ar), 6.69–6.65 (m, 3 H, CHAr), 3.35–3.30 (m, 4 H, NCH2), 1.65–1.58 (m, 4 H, CH2), 1.44–1.32 (m, 4 H, CH2), 0.98 (t, J = 7.3 Hz, 6 H, CH3) ppm. 13C NMR(75 MHz, CDCl3): δ = 161.0, 162.8, 159.7, 158.1, 149.0, 142.4,138.9, 126.7, 125.7, 125.4, 123.1, 116.0, 115.9, 113.1, 111.8, 111.6,101.1, 96.1, 94.6, 50.9, 29.6, 20.5, 14.1 ppm. MS (EI): m/z = 614.0.C29H30BF2IN2O2 (614.28): calcd. C 56.70, H 4.92, N 4.56; foundC 56.68, H 4.80, N 4.25.

Boranil 6: Red powder, yield 48%. 1H NMR (300 MHz, CDCl3): δ= 8.41 (s, 1 H, CH imine), 7.65 (d, J = 8.9 Hz, 2 H, CH Ar), 7.57–7.53 (m, 3 H, CH Ar), 7.21–7.15 (m, 3 H, CH Ar), 6.69–6.65 (m,3 H, CH Ar), 3.35–3.30 (m, 4 H, CH2), 1.63–1.56 (m, 4 H, CH2),1.42–1.34 (m, 4 H, CH2) 0.98 (t, J = 7.3 Hz, 6 H, CH3) ppm. 13CNMR (75 MHz, CDCl3): δ = 164.5, 163.2, 162.6, 159.6, 157.9,149.0, 138.9, 126.6, 125.6, 125.6, 125.5, 123.0, 116.9, 116.6, 116.0,113.0, 111.6, 101.1, 96.1, 50.9, 29.6, 20.5, 14.1 ppm. MS (EI): m/z= 506.1. C29H30BF3N2O2 (506.37): calcd. C 68.79, H 5.97, N 5.53;found C 68.56, H 5.68, N 5.37.

Boranil 7: Red powder, yield 81%. 1H NMR (300 MHz, CDCl3): δ= 8.48 (s, 1 H, CH imine), 7.82 (d, J = 8.6 Hz, 2 H, CH Ar), 7.57(s, 1 H, CH Ar), 7.42 (d, J = 8.6 Hz, 1 H, CH Ar), 7.35 (d, J =8.4 Hz, 1 H, CH Ar), 7.20 (s, 1 H, CH Ar), 7.12 (s, 1 H, CH Ar),6.70–6.63 (m, 4 H, CH Ar), 3.36–3.32 (m, 4 H, NCH2), 1.62–1.59(m, 4 H, CH2), 1.41–1.35 (m, 4 H, CH2), 0.97 (t, J = 7.3 Hz, 6 H,CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 165.2, 163.6, 163.4,160.0, 158.6, 149.1, 146.0, 134.0, 133.8, 133.7, 126.7, 126.3, 126.2,124.6, 123.3, 122.2, 117.9, 115.7, 114.6, 113.1, 113.0, 111.6, 101.3,96.0, 60.5, 50.9, 29.6, 20.5, 14.1 ppm. MS (EI): m/z = 513.2.C30H30BF2N3O2 (513.39): calcd. C 70.19, H 5.89, N 8.18; found C69.84, H 5.64, N 7.92.

Boranil 8: Red powder, yield 91%. 1H NMR (300 MHz, CDCl3): δ= 8.44 (s, 1 H, CH imine), 7.63 (d, J = 9.0 Hz, 2 H, CH Ar), 7.52(s, 1 H, CH Ar), 7.12 (s, 1 H, CH Ar), 6.77 (s, 2 H, CH Ar), 6.67(d, J = 9.0 Hz, 2 H, CH Ar), 6.62 (s, 1 H, CH Ar), 3.89 (s, 6 H,OCH3), 3.87 (s, 3 H, OCH3), 3.34–3.29 (m, 4 H, N-CH2), 1.65–1.55 (m, 4 H, CH2), 1.44–1.32 (m, 4 H, CH2), 0.98 (t, J = 7.3 Hz,6 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.9, 166.7,159.0, 157.1, 152.7, 148.7, 145.8, 141.0, 126.4, 124.0, 121.2, 118.4,116.7, 115.2, 111.6, 111.3, 110.7, 105.9, 99.7, 96.7, 61.1, 56.3, 50.9,29.6, 20.5, 14.2 ppm. MS (EI): m/z = 578.2. C32H37BF2N2O5

(578.46): calcd. C 66.44, H 6.45, N 4.84; found C 66.17, H 6.18, N4.59.

HBBO Borate 12: Yellow powder, yield 80%. 1H NMR (300 MHz,CDCl3): δ = 8.00 (s, 1 H, CH Ar), 7.91 (m, 1 H, CH Ar), 7.72 (d,J = 8.4 Hz, 2 H, CH Ar), 7.55–7.57 (m, 2 H, CH Ar), 7.46 (d, J =8.4 Hz, 2 H, CH Ar), 7.27 (m, 1 H, CH Ar), 6.89 (s, 1 H, CH Ar),1.38 (s, 9 H, tBu), 1.35 (s, 9 H, tBu) ppm. 13C NMR (75 MHz,CDCl3): δ = 162.3, 161.1, 158.1, 157.5, 152.6, 151.6, 146.9, 130.9,126.7, 125.9, 125.1, 124.9, 124.1, 117.4, 113.3, 110.8, 103.2, 101.9,99.9, 35.5, 35.0, 31.7, 31.3 ppm. MS (EI): m/z = 487.1.C29H28BF2NO3 (487.35): calcd. C 71.47, H 5.79, N 2.87; found C71.37, H 5.67, N 2.66.

HBBO Borate 13: Yellow powder, yield 72%. 1H NMR (300 MHz,CDCl3): δ = 8.00 (s, 1 H), 7.92 (m, 1 H), 7.73 (d, J = 8.8 Hz, 2 H),7.58–7.60 (m, 2 H), 7.28 (s, 1 H), 6.94 (d, J = 8.8 Hz, 2 H), 6.79(s, 1 H), 3.83 (s, 3 H, OCH3), 1.41 (s, 9 H, tBu) ppm. 13C NMR(75 MHz, CDCl3): δ = 161.2, 160.6, 158.1, 157.5, 151.7, 146.9,131.0, 126.6, 125.1, 124.4, 122.3, 117.1, 114.5, 113.4, 110.8, 103.2,101.9, 98.8, 55.5, 35.6, 31.7 ppm. MS (EI): m/z = 461.1.


C26H22BF2NO4 (461.27): calcd. C 67.70, H 4.81, N 3.04; found C67.51, H 4.62, N 2.67.

HBBO Borate 14: Orange powder, yield 66 %. 1H NMR (300 MHz,CDCl3): δ = 7.97 (s, 1 H, CH Ar), 7.92 (m, 1 H, CH Ar), 7.57–7.66 (m, 4 H, CH Ar), 6.68 (m, 3 H, CHAr), 3.31 (t, J = 7.4 Hz, 4H, N-CH2), 1.55–1.66 (m, 4 H, CH2), 1.32–1.39 (m, 4 H, CH2),0.98 (t, J = 7.3 Hz, 6 H, CH3) ppm. 13C NMR (75 MHz, CDCl3):δ = 162.6, 161.3, 159.4, 158.4, 157.2, 151.6, 148.9, 146.9, 131.1,126.6, 125.0, 124.9, 116.2, 116.1, 113.4, 111.6, 110.8, 102.8, 101.7,96.4, 50.9, 35.6, 31.7, 29.6, 20.5, 14.2 ppm. MS (EI): m/z = 558.2.C33H37BF2N2O3 (558.47): calcd. C 70.97, H 6.68, N 5.02; found C70.62, H 6.54, N 4.69.

Theoretical Calculations: TD-DFT was used to probe the natureof the excited-states of the HBBO dyes 12–14; the only structuralsimplifications were the use of NMe2 rather than NBu2 donatinggroups and the use of methyl instead of tBu (see Scheme 1). Weused a computational protocol similar to the one applied in a re-cent paper devoted to other HBO structures[25] and we redirect theinterested reader to this contribution for further technical detailsand discussion. Extended guidelines dealing with TD-DFT applica-tions on dyes presenting a NBO pattern can also be found else-where.[26] The ground- and excited-state structures were optimizedby using analytic DFT and TD-DFT gradients, respectively. Theseforce minimizations were performed until the residual mean squareforce is less than 1 �10–5 a.u. The harmonic vibrational frequenciesof the different states were computed for the optimal geometriesby using analytical and numerical differentiation for the groundand excited states, respectively. This allowed the nature of the min-ima to be ascertained. In our calculations the electrostatic interac-tions between the dye and the environment were modelled by usingthe PCM method, which introduces a valid model for solvent ef-fects as long as there are no specific solute–solvent interactions.[27]

For this reason we modelled the systems in toluene and CH2Cl2.Both the absorption and fluorescence maxima were evaluated byusing the corrected linear-response (cLR) PCM model that allowsthe correct polarization of the excited-state cavity.[28] All our calcu-lations were performed with the Gaussian 09 program[29] by usingthe ωB97X-D range-separated hybrid functional,[30] which has beenshown to provide chemically sound excited-state properties forHBBO dyes although a systematic overestimation of the transitionenergies was noted.[25] The 6-31G(d) atomic basis set was used todetermine most parameters, whereas a much more extended basisset, 6-311+G(2d,p), was applied to correct the cLR PCM verticaltransition energies (both absorption and fluorescence). This combi-nation has been shown to yield results close to basis-set conver-gence for TD-DFT calculations performed on fluoroborate com-plexes, for example, BODIPY and similar derivatives,[31] and theinterested reader will find more details in that contribution. Thecharge-transfer parameters were computed by using Le Bahers’density-based model.[32]

Supporting Information (see footnote on the first page of this arti-cle): 1H and 13C NMR for all compounds, crystallographic andspectroscopic data.

Acknowledgments

The authors thank the Centre National de la Recherche Sci-entifique (CNRS) for providing research facilities and financialsupport, the Ministère de l’Enseignement Supérieur et de la Re-cherche for a MENRT Ph. D. fellowship for K. B. This project wassupported by Rhin-Solar, part of the European Fund for RegionalDevelopment (FEDER) within the framework of the Programme



INTERREG IV Upper Rhine (project number C25). S. C. and D. J.acknowledge the European Research Council (ERC) for financialsupport within the framework of a Starting Grant (Marches –278845). This research used resources of the GENCI-CINES/IDRIS (grant numbers c2013085117 and x2013080649), the Centrede Calcul Intensif des Pays de Loire (CCIPL), and of a local Troycluster.

[1] a) M. Shimizu, T. Hiyama, Chem. Asian J. 2010, 5, 1516–1531;b) S. Varughese, J. Mater. Chem. C 2014, 2, 3499–3516.

[2] a) P. Kiprof, J. C. Carlson, D. R. Anderson, V. N. Nemykin,Dalton Trans. 2013, 42, 15120–15122; b) Z. Zhao, J. W. Y. Lam,B. Z. Tang, J. Mater. Chem. 2012, 22, 23726–23740.

[3] a) A. Loudet, K. Burgess, Chem. Rev. 2007, 107, 4891–4932;b) G. Ulrich, R. Ziessel, A. Harriman, Angew. Chem. Int. Ed.2008, 47, 1184–1207; Angew. Chem. 2008, 120, 1202; c) N.Boens, V. Leen, W. Dehaen, Chem. Soc. Rev. 2012, 41, 1130–1172.

[4] a) H. Lu, Q. Wang, L. Gai, Z. Li, Y. Deng, X. Xiao, G. Lain,Z. Shen, Chem. Eur. J. 2012, 18, 7852–7861; b) C. A. Swamy P,S. Mukherjee, P. Thilagar, J. Mater. Chem. C 2013, 1, 4691–4698.

[5] T. T. Vu, M. Dvorko, E. Y. Schmidt, J.-F. Audibert, P. Re-tailleau, B. A. Trofimov, R. B. Pansu, G. Clavier, R. Méallet-Renault, J. Phys. Chem. C 2013, 117, 5373–5385.

[6] Y. Ooyama, Y. Hagiwara, Y. Oda, H. Fukuoka, J. Ohshita,RSC Adv. 2014, 4, 1163–1167.

[7] G.-L. Fu, H. Pan, Y.-H. Zhao, C.-H. Zhao, Org. Biomol. Chem.2011, 9, 8141–8146.

[8] a) T. Ozdemir, S. Atilgan, I. Kutuk, L. T. Yildirim, A. Tulek,M. Bayindir, E. U. Akkaya, Org. Lett. 2009, 11, 2105–2107; b)Z. Zhang, B. Xu, J. Su, L. Shen, Y. Xie, H. Tian, Angew. Chem.Int. Ed. 2011, 50, 11654–11657; Angew. Chem. 2011, 123,11858.

[9] a) D. Ding, K. Li, B. Liu, B. Z. Tang, Acc. Chem. Res. 2013,46, 2441–2453; b) Y. Hong, J. W. Y. Lam, B. Z. Tang, Chem.Soc. Rev. 2011, 40, 5361–5388.

[10] D. Frath, J. Massue, G. Ulrich, R. Ziessel, Angew. Chem. Int.Ed. 2014, 53, 2290–2310.

[11] a) J. F. Araneda, W. E. Piers, B. Heyne, M. Parvez, R. McDon-ald, Angew. Chem. Int. Ed. 2011, 50, 12214–12217; Angew.Chem. 2011, 123, 12422; b) D. Curiel, M. Más-Montoya, L.Usea, A. Espinosa, R. A. Orenes, P. Molina, Org. Lett. 2012,14, 3360–3363; c) D. Suresh, C. S. B. Gomes, P. T. Gomes,R. E. Di Paolo, A. L. Maçanita, M. J. Calhorda, A. Charas, J.Morgado, M. T. Duarte, Dalton Trans. 2012, 41, 8502–8505; d)W. Li, W. Lin, J. Wang, X. Guan, Org. Lett. 2013, 15, 1768–1771; e) D. Frath, A. Poirel, G. Ulrich, A. De Nicola, R. Zies-sel, Chem. Commun. 2013, 49, 4908–4910; f) D. Zhao, G. Li,D. Wu, X. Qin, P. Neuhaus, Y. Cheng, S. Yang, Z. Lu, X. Pu,C. Long, J. You, Angew. Chem. Int. Ed. 2013, 52, 13676–13680;Angew. Chem. 2013, 125, 13921; g) N. Gao, C. Cheng, C. Yu,E. Hao, S. Wang, J. Wang, Y. Wei, X. Mu, L. Jiao, DaltonTrans. 2014, 43, 7121–7127.

[12] a) Y. Zhou, Y. Xiao, S. Chi, X. Qian, Org. Lett. 2008, 10, 633–636; b) Y. Zhou, J. W. Kim, M. J. Kim, W.-J. Son, S. J. Han,H. N. Kim, S. Han, Y. Kim, C. Lee, S.-J. Kim, D. H. Kim, J.-J. Kim, J. Yoon, Org. Lett. 2010, 12, 1272–1275; c) J. Feng, B.Liang, D. Wang, L. Xue, X. Li, Org. Lett. 2008, 10, 4437–4440;d) K. Benelhadj, J. Massue, P. Retailleau, G. Ulrich, R. Ziessel,Org. Lett. 2013, 15, 2918–2921.

[13] Y. Yang, X. Su, C. N. Carroll, I. Aprahamian, Chem. Sci. 2012,3, 610–613.

[14] Y. Kubota, T. Tsuzuki, K. Funabiki, M. Ebihara, M. Matsui,Org. Lett. 2010, 12, 4010–4013.

[15] W. Li, W. Lin, J. Wang, X. Guan, Org. Lett. 2013, 15, 1768–1771.


[16] L. Quan, Y. Chen, X.-J. Lv, W.-F. Fu, Chem. Eur. J. 2012, 18,14599–14604.

[17] K. Perumal, J. A. Garg, O. Blacque, R. Saiganesh, S. Kabilan,K. K. Balasubramanian, K. Venkatesan, Chem. Asian J. 2012,7, 2670–2677.

[18] a) J. Massue, D. Frath, P. Retailleau, G. Ulrich, R. Ziessel, Org.Lett. 2012, 14, 230–233; b) J. Massue, P. Retailleau, G. Ulrich,R. Ziessel, New J. Chem. 2013, 37, 1224–1230.

[19] a) C. C. Jiménez, N. Farfán, M. Romero-Avila, M. Rodrguez,L. Aparicio-Ixta, G. Ramos-Ortiz, J. L. Maldonado, R. Santil-lan, N. E. Magana-Vergara, M. E. Ochoa, J. Organomet. Chem.2014, 755, 33–40; b) K. Dhanunjayarao, V. Mukundam, M.Ramesh, K. Venkatasubbaiah, Eur. J. Inorg. Chem. 2014, 539–545.

[20] a) D. Frath, S. Azizi, P. Retailleau, G. Ulrich, R. Ziessel, Org.Lett. 2011, 13, 3414; D. Frath, S. Azizi, P. Retailleau, G. Ulrich,R. Ziessel, Org. Lett. 2011, 13, 3417; b) D. Frath, S. Azizi, G.Ulrich, R. Ziessel, Org. Lett. 2012, 14, 4774–4777.

[21] a) D. L. Williams, A. Heller, J. Phys. Chem. 1970, 74, 4473–4480; b) M. Ikegami, T. Arai, J. Chem. Soc. Perkin Trans. 22002, 1296–1301; c) T. Iijima, A. Momotake, Y. Shinohara, T.Sato, Y. Nishimura, T. Arai, J. Phys. Chem. A 2010, 114, 1603–1609; d) J. Zhao, S. Ji, Y. Chen, H. Guo, P. Yang, Phys. Chem.Chem. Phys. 2012, 14, 8803–8817; e) J. E. Kwon, S. Y. Park,Adv. Mater. 2011, 23, 3615–3642.

[22] a) J. Massue, D. Frath, P. Retailleau, G. Ulrich, R. Ziessel,Chem. Eur. J. 2013, 19, 5375–5386; b) J. Massue, G. Ulrich, R.Ziessel, Eur. J. Org. Chem. 2013, 25, 5701–5709.

[23] K. Benelhadj, W. Muzuzu, J. Massue, P. Retailleau, A. Charaf-Eddin, A. D. Laurent, D. Jacquemin, G. Ulrich, R. Ziessel,Chem. Eur. J. 2014, 20, 12842–12857.

[24] H. Lopez-Ruiz, H. Briseño-Ortega, S. Rojas-Lima, R. Santil-lan, N. Farfàn, Tetrahedron Lett. 2011, 52, 4308–4312.

[25] B. Le Guennic, S. Chibani, A. Charaf-Eddin, J. Massue, R.Ziessel, G. Ulrich, D. Jacquemin, Phys. Chem. Chem. Phys.2013, 15, 7534–7540.

[26] S. Chibani, A. Charaf-Eddin, B. Le Guennic, D. Jacquemin, J.Chem. Theory Comput. 2013, 9, 3127–3135.

[27] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 2005, 105,2999–3094.

[28] M. Caricato, B. Mennuci, J. Tomasi, F. Ingrosso, R. Cammi, J.Chem. Phys. 2006, 124, 124520.

[29] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M.Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Ad-amo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Mar-tin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B.Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09, re-vision C.01 and D.01, Gaussian Inc., Wallingford, CT, 2009.

[30] J. D. Chai, L. Head-Gordon, Phys. Chem. Chem. Phys. 2008,10, 6615–6620.

[31] S. Chibani, B. Le Guennic, A. Charaf-Eddin, O. Maury, C. An-draud, D. Jacquemin, J. Chem. Theory Comput. 2012, 8, 3303–3313.

[32] a) T. Le Bahers, C. Adamo, I. Ciofini, J. Chem. Theory Com-put. 2011, 7, 2498–2506; b) D. Jacquemin, T. Le Bahers, C. Ad-amo, I. Ciofini, Phys. Chem. Chem. Phys. 2012, 14, 5383–5388.

Received: June 23, 2014Published Online: �


J. Massue, D. Jacquemin, R. Ziessel, G. Ulrich et al.FULL PAPER

Luminescent Borate Complexes

A series of borate complexes based on an K. Benelhadj, J. Massue,* P. Retailleau,original 2-(6�-hydroxy-5�-benzofuryl) scaf- S. Chibani, B. Le Guennic, D. Jacquemin,*fold have been synthesized that are highly R. Ziessel,* G. Ulrich* ................... 1–10luminescent both in solution and in the so-lid state. Depending on their substitution, Solution- and Solid-State Luminescentthey exhibit either a strong internal charge Borate Complexes Based on a Substitutedtransfer leading to pronounced solvatoch- π-Conjugated 2-(6�-Hydroxy-5�-benzofu-romism or singlet emission. Their emission ryl) Scaffoldspans the whole visible range with quan-tum yields of up to 87%. Keywords: Fluorescence / Luminescence /

Dyes/Pigments / Density funtional calcu-lations / Borates


Solution- and Solid-State Luminescent Borate Complexes Based on a Substituted π-Conjugated...

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