Electron-Rich Dipyrrolonaphthyridinediones: Synthesis and Optical

Article pubs.acs.org/joc

Cite This: J. Org. Chem. 2018, 83, 11645−11653

Electron-Rich Dipyrrolonaphthyridinediones: Synthesis and Optical Properties Bartłomiej Sadowski,† Marcel Loebnitz,‡ Dennis R. Dombrowski,‡ Daniel H. Friese,*,‡ and Daniel T. Gryko*,† †

Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland Heinrich Heine-Universität Düsseldorf, Institut für Theoretische und Computerchemie, Universitätsstraße 1, 40204 Düsseldorf, Germany

Downloaded via UNIV OF SUNDERLAND on October 5, 2018 at 09:14:02 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

S Supporting Information *

ABSTRACT: This article describes the design rationale for highly electron-rich dipyrrolonaphthyridinedione (DPND) derivatives bearing substituted amino groups at the 3 and 9 positions, which exhibit absorption in the red and emission in the red/NIR region of the spectrum. These novel dyes are easily synthesized through a two-step protocol consisting of bromination of the DPND molecule followed by Buchwald−Hartwig amination. We demonstrated that the diamino-dipyrrolonaphthyridinediones have high ionization energies (∼4.7 eV) and that the spectroelectrochemical properties can be rationally tuned by altering the nature of the peripheral substituted amino groups. All amino-DPNDs exhibit solvatofluorochromism, which has not been previously reported for dyes possessing this core. Theoretical calculations reveal that in all cases, the strongest absorption is exhibited by the S1 states which clearly correlate with the HOMO−LUMO orbital transition. As all higher states have lower oscillator strengths, it is clear that fluorescence is completely dominated by the excitation/deexcitation sequence S0 → S1, S1 → S0 and that there are no contributions to the fluorescence from excitations to higher states.

■

based dyes) exhibit poor photostability and/or low fluorescence quantum yields. Within this context, some structural modifications are used to improve the optical characteristics of target molecules, namely: (1) appropriate extension of the πsurface;9c,13 (2) rigidification of rotatable moieties;9d,10a,14 (3) efficient planarization by reducing the dihedral angle between a heterocyclic core and peripheral aromatic units by replacement of phenyl with five-membered heterocyclic rings.15 Recently, we proved that the dipyrrolonaphthyridinedione (DPND) core (Figure 1) constitutes an excellent scaffold for the design of strongly fluorescent dyes16 or quadrupolar-type materials with large two-photon absorption (TPA) cross sections (up to 5180 GM).17 These properties result from an unusual arrangement of donor (pyrrole ring) and acceptor (carbonyl group) moieties within the DPND core.

INTRODUCTION Demand for dyes that both absorb and emit long wavelength light for photonic and cell imaging applications is increasing. Compounds of this type, especially near-infrared (NIR) dyes, have been found to be useful in photodynamic (PDT)1 and photothermal therapy (PTT)2 in which tumor cells are killed by either reactive oxygen species or heat, respectively. Due to the undeniable biological advantages of NIR light, such as deep tissue penetration and minimal interference from background autofluorescence, these dyes are widely used for high contrast bioimaging and detection in living systems.3 A recent expansion of interest in this class of molecules has resulted in many technological applications,4 such as photography,5 laser filters,6 and optical recording.7 A major trend in the development of new, long-wavelength absorbing and emitting dyes relies on the modification of known scaffolds such as cyanines,8 BODIPY and azaBODIPY,9 rhodamines and sila-rhodamines,10 diketopyrrolopyrroles,11 etc.;12 however, some of these (especially cyanine© 2018 American Chemical Society

Received: June 27, 2018 Published: September 4, 2018 11645

DOI: 10.1021/acs.joc.8b01615 J. Org. Chem. 2018, 83, 11645−11653

Article

The Journal of Organic Chemistry

of 4 toward other amines. We evaluated both dialkylamines and diarylamines with different electron-donating abilities to diversify the optoelectronic properties of the target compounds. Amination of 4 was successful with morpholine and four other diarylamines, leading to dyes 5−9 (Scheme 1). Inspired by the work of Lavis et al.,20 we also performed the coupling reaction between 4 and azetidine hydrochloride, but the expected product proved to be highly unstable during the purification process. Optoelectronic Properties. The optical properties of previously obtained dyes 1−3 and newly prepared dyes 5−9 were studied by means of steady-state UV−vis spectroscopy and compared (Table 1 and Figure 3). All amino-DPNDs exhibit strong absorption in the red and emission in the red/ NIR region of the spectrum. Taking into account their structural features, we choose derivative 5 as a reference molecule. The absorption spectrum of compound 5 shows one pronounced absorption band located in the range of 575−590 nm which is characterized by a high molar extinction coefficient. The maximum of the emission band for dye 5 is located in the range of 628−670 nm depending on the polarity of the solvent. The values of fluorescence quantum yields are moderate (∼0.3) in the majority of tested solvents (cyclohexane, toluene, THF, CH2Cl2), while in polar DMSO this value decreases slightly (Φfl = 0.18). Compared with the parent DPND dye in DCM,16 both the absorption and emission maxima of 5 are red-shifted by 74 and 125 nm, respectively. In the case of the 4-anilino substituted DPND dyes 1 and 2, the introduction of an aryl linkage between the peripheral amino group and the core causes bathochromic shift of both absorption and emission bands with respect to 5. The incorporation of a triple bond between the aryl rings and DPND core such as in 3, results in planarization in the structure of 3, which is reflected in a further bathochromic shift of λabsmax and λemmax. Compounds 1 and 3 exhibit similar behavior in terms of Φfl values, for which Φfl is the highest in nonpolar cyclohexane and decreases gradually with increasing solvent polarity. Sequential chromophore extension can be also connected with an increase in the value of ε in order 5 < 1 ≪ 3. The introduction of diphenylamine substituents directly attached to the DPND core as in 6, instead of dialkylamine substituents in 5 causes a bathochromic shift of both λabsmax and λemmax values. Interestingly, the fluorescence quantum yields measured for compound 6 reach 0.52 in cyclohexane and 0.33 in DMSO which are noticeably higher than those for dye 5. The phenomenon of higher quantum efficiencies for derivative 6 compared with those for 5 can be ascribed to “the amino conjugation effect” introduced earlier by Yang and others.21 Likewise, the values of Φfl for 2 are comparable or slightly higher than those for 1. It should be pointed out that in terms of λabsmax and λemmax, an opposite effect appears when comparing 1 to 2, that is in 5 and 6, the replacement of dialkylamino groups for diphenylamine results in a hypsochromic shift of both absorption and emission bands. Compound 2 can be considered as a π-expanded analogue of dye 6 in a similar manner to the relationship between 1 and 5. Again, the introduction of additional aryl π-spacers causes a shift in both absorption and emission maxima toward shorter wavelengths due to a substantial dihedral angle between the core and aryl rings.

Figure 1. Structure and numbering of key positions of the DPND core.

Our previous studies suggest that the DPND core as a whole has an electron-deficient character.18 Consequently, the goal of this project was to investigate the effect that introduction of electron-donating amino groups into positions 3 and 9 of the DPND core will have on the optoelectronic properties. The designed dyes contain amine moieties directly attached to the core, which is expected to induce a much stronger electrondonating effect compared with previously reported amino substituted DPND derivatives 1−3 (Figure 2). Moreover, we

Figure 2. General structures of previously obtained DPND derivatives and dyes obtained in this work.

foresee that the optoelectronic properties of the designed dyes can be effectively tuned by careful choice of the substituted amine moiety. Herein, we demonstrate that this strategy leads to centrosymmetric, solvatofluorochromic, long-wavelength emissive dyes.

■

RESULTS AND DISCUSSION Synthetic Approach. Our approach toward DPND derivatives that contain amine moieties attached directly to the core employs the well-known Buchwald−Hartwig amination reaction19 on dibrominated DPND 416 (Scheme 1). Careful optimization of the reaction conditions was performed using bis(4-methoxyphenyl)amine (Table S1, Supporting Information). We found that the best catalytic system comprises tris(dibenzylideneacetone)dipalladium(0) (Pd2dba3) as a catalyst, SPhos as a ligand, and Cs2CO3 as a base in toluene. Next, we carried out studies on the reactivity 11646


Article

The Journal of Organic Chemistry Scheme 1. Scope of Buchwald−Hartwig Amination Reaction

Compound 7 is an analogue of dye 6 enriched by four OMe groups. The incorporation of additional donor groups into para positions of the phenyl rings causes further bathochromic shifts in both the absorption maxima and the emission maxima compared to dye 6. Interestingly, the emission maxima for all solvents are located in the NIR region (702−739 nm). Fluorescence quantum yields of dye 7 are lower in contrast to those of dye 6 and gradually decrease during change from cyclohexane to DMSO, while the values of ε are slightly higher, highlighting stronger electron-donating effect of the amino substituents (7 versus 6). The replacement of four OMe groups with CN groups (7 versus 8) causes an increase in Φfl (up to 0.62 in CH2Cl2), and at the same time, minimal quenching effects in polar solvents are observed. However, we also note a hypsochromic shift of both absorption and emission maxima. Molecular extinction coefficients generally remain similar to the parent compound 6. Furthermore, the influence of the bis(3,4,5trimethoxyophenyl)amino substituent was investigated. The positions of absorption bands in 9 do not change significantly compared to those of 7 containing bis(4-methoxyophenyl)amino substituents, while the corresponding emission bands are blue-shifted. Gradual quenching of Φfl upon changing from cyclohexane to DMSO takes place for both compounds 7 and 9. The presence of an additional eight OMe groups in dye 9 compared with 7 increases the likelihood of nonradiative deactivation pathways, which results in even lower fluorescence quantum yields for this dye. It can be clearly noted that while the position of the absorption band for the dyes 1−9 shows a negligible change upon moving from cyclohexane to DMSO, the emission maxima show a considerable bathochromic shift with increasing polarity of the solvent. Taking this into account, we evaluated the solvent-dependent fluorescence features of 1−3 and 5−9 using the Lippert−Mataga function22 (eqs 1 and 2)

ΔSS = νabs − νfl = Δf =

2(μg − μe )2 hca3

ε−1 n2 − 1 − 2 2ε + 1 2n + 1

× Δf + const

(1)

(2)

(where νabs and νfl are absorption and fluorescence maxima; μg and μe are ground- and excited-state dipole moments; a is solvent cavity radius (Å); ε is solvent dielectric constant; and n is solvent refractive index) and Reichhardt parameter (ET(30)) plots,23 by plotting the obtained Stokes shift (cm−1) versus the solvent orientation polarizability (Δf) and ET(30) values, respectively (Table S2, Supporting Information). We found a positive linear correlation between the Stokes shift and the corresponding factors for all compounds, which suggests that μe (eq 1) is not 0 (because (μg − μe)2 > 0 and μg = 0). Due to the centrosymmetric shape of the chromophore, there should be neither a dipole moment in the ground nor in the excited state; however, the change in electron distribution upon excitation indicates a stronger local separation of charges which can then interact preferably with more polar solvents (see Computational Studies section). On the other hand, it is wellknown that fluorescence solvatochromism also can result from symmetry-breaking of centrosymmetric molecules in the excited-state occurring in polar solvents.24 The photostability of all dyes was tested by irradiation of their air-equilibrated toluene solutions with a UV lamp (7 W). The dye stability judged by half-life times (Table S5, Supporting Information) in order from the most stable to the least stable is 8 > 3 > 6 > 9 > 2 > 1 > 7 > 5. Among dyes with dialkylamine group at the peripheries, compounds 1 and 3 containing aryl or arylethynyl π-spacer occurred to be significantly more stable that compound 5. Furthermore, compound 5 is the least photostable among considered dyes. Both dyes bearing Ph2N moieties at the peripheries (2 and 6) exhibit similar stability. Finally, the highest half-life times were 11647


Article


pyrrolopyrrole core (in the case of 3) and (2) the addition of electron-accepting groups (CN) which decreases electron density (in the case of 8). The electrochemical behavior of the synthesized compounds was investigated by CV, and the data derived from both the first reduction and oxidation waves are collected in Table 2. In general, the majority of the investigated compounds show one reversible reduction wave and one reversible oxidation wave (see Supporting Information for cyclic voltammograms), where the reduction wave probably refers to the electron transfer to the DPND core and the oxidation wave can be ascribed to the oxidation of the peripheral amino groups. Interestingly, four dyes (1−3 and 9) exhibit the second oxidation wave in the accessible potential range in dichloromethane (at potentials higher than +1.4 V), which can be associated with the formation of radical cations within the core.18 According to the measurements, compounds 5 and 7 are the most susceptible to oxidation, mostly due to their high electron-rich character, while compounds 3 and 8 undergo a reduction process much easier than the other dyes. The shift of the oxidation wave toward negative values (and hence lower ionization energies) follows the intuitive increase in electron density imparted by the introduction of highly electrondonating substituents in positions 3 and 9. Similarly to the previously obtained bis-aryl dipyrrolonaphthyridinediones,18 all electrochemically derived electron affinity levels lie below −3.0 eV. Computational Studies. In a series of quantum chemical calculations, the behavior of the first excited state of the exemplary molecules 6 and 8 have been considered involving solvent effects for cyclohexane, toluene, CH2Cl2, THF, and DMSO. Solvent effects on both the absorption and emission wavelengths and oscillator strengths were also studied. The calculated data are listed in Table S3 in the Supporting Information and refer to the S0 → S1 excitation or deexcitation, respectively. In both cases, this excitation is dominated by the transition between the highest occupied (HOMO) and the lowest unoccupied molecular orbital (LUMO). Among the calculated states, this is the one with the highest oscillator strength. Therefore, it is considered to be the main source of fluorescence as excitations to higher-lying states which could relax to the S1 state is not expected to be relevant due to the low oscillator strengths (not shown). In comparison with experimental observations, we note that while the calculated emission wavelengths are fairly accurate, the absorption wavelengths of our results are blue-shifted by 80−100 nm depending on the solvent (Table S3, Supporting Information). Comparing these values, we immediately noted that for both absorption and emission they separate into two different groups which correspond to nonpolar solvents, toluene and cyclohexane, and polar solvents, CH2Cl2, THF, and DMSO. In contrast to the experimental results, this separation is much stronger in the calculations, especially for the emission wavelengths. It should be pointed out that the solvation model used here takes into account only the solvent polarizability parameter and other interaction effects (e.g. πinteractions in the case of toluene) cannot be described in this approach. In all excited state optimization calculations, we observed two major effects for all solvents: (1) elongation of the average bond length and (2) a change in bond length alternation. Considering the bond lengths of the S0 and S1 geometries for molecule 8 in DMSO (Table S4, Supporting Information), the

Table 1. Spectroscopic Properties of Amino-DPNDs 5−9 and Previously Obtained π-Expanded DPND Derivatives dye

solvent

λabsmax/ nm

DPNDd 1

CH2Cl2 cyclohexane toluene THF CH2Cl2f MeCN DMSO cyclohexane toluene THF CH2Cl2f MeCN DMSO cyclohexane toluene THF CH2Cl2d MeCN DMSO cyclohexane toluene THF CH2Cl2 MeCN DMSO cyclohexane toluene THF CH2Cl2 MeCN DMSO cyclohexane toluene THF CH2Cl2 MeCN DMSO cyclohexane toluene THF CH2Cl2 MeCN DMSO cyclohexane toluene THF CH2Cl2 MeCN DMSO

504 603 613 615 615 607 631 575 585 580 583 573 589 639 645 644 645 634 652 575 582 580 578 576 590 608 614 608 608 601 613 645 654 648 648 642 656 565 571 560 558 554 564 646 654 640 634 627 638

2

3

5

6

7

8

9

ε·10−4/ M−1· cm−1 2.9 3.6 3.7 4.0 3.9 3.4 2.8 3.5 3.8 3.8 3.8 nde 2.3 4.2 5.2 5.6 5.7 3.6 3.7 3.7 3.8 3.5 3.4 2.9 2.8 3.3 2.9 3.1 2.9 2.8 2.4 3.8 3.5 3.7 3.5 3.4 3.8 nde 2.7 2.8 2.7 2.7 2.6 4.0 4.3 3.6 3.6 3.4 3.3

λemmax/ nm

ΔSS/ cm−1a

528 670 702 729 735 750 758 658 680 708 718 727 731 670 698 726 736

900 1700 2100 2500 2700 3100 2700 2200 2400 3100 3200 3700 3300 700 1200 1800 1900

628 645 650 653 659 670 665 678 680 693 698 706 702 718 720 727 732 739 639 655 658 659 666 677 698 711 711 710 711 720

1500 1700 1900 2000 2200 2000 1400 1500 1700 2000 2300 2100 1300 1400 1500 1700 1900 1700 2000 2200 2700 2700 3000 3000 1200 1200 1600 1800 1900 1700

Φfl 0.71 0.40c 0.25c 0.11c 0.10c 0.02c 0.02c 0.31b 0.30b 0.27b 0.20b 0.08b 0.04b 0.39c 0.24c 0.14c 0.17c 0 0 0.35b 0.32b 0.35b 0.27b 0.21b 0.18b 0.52c 0.39c 0.44c 0.41c 0.41c 0.33c 0.39c 0.26c 0.10c 0.07c 0.01c 0.01c 0.37b 0.49b 0.62b 0.61b 0.63b 0.47b 0.31c 0.11c 0.03c 0.02c 0.01c 0.01c

a

Stokes shift. bSulforhodamine 101 was used as a reference (Φfl = 0.95 in EtOH). cCresyl violet was used as a reference (Φfl = 0.54 in MeOH). dThe optical data were taken from ref 16. end: not determined due to low solubility. fThe optical data were taken from ref 18.

measured for DPNDs 3 and 8. Thus, the key structural elements for introducing high photostability were (1) the introduction of longer π-spacer between an amine group and a 11648


Article


Figure 3. Absorption (solid) and emission (dotted) spectra of all compound measured in cyclohexane (black), toluene (green), THF (red), CH2Cl2 (yellow), MeCN (blue), and DMSO (orange) .

pronounced for the polar solvents CH2Cl2, THF, and DMSO. Furthermore, we observe that in the ground state, the bond lengths show nearly no dependence on the solvent (variability between solvents around 10−4 Å), while in the S1 state, they show a solvent dependence which is about 2 orders of magnitude larger. The shapes of the HOMO and LUMO orbitals of 6 and 8 are shown in Figure 4. The HOMOs of each are localized on the DPND core and nitrogen atoms within the amine peripheral moiety. During the HOMO → LUMO transition, the electron density is shifted from the peripheral nitrogen atoms toward the DPND core, confirming substantial electronic communication between the core and these atoms. It has to be pointed out that according to calculations, aryl rings attached directly to nitrogens within the peripheral amino group are not involved in the excitation to the S1 state. However, as described in the previous section, we note a bathochromic shift of both absorption and emission for 7

most noticeable changes in bond length alternation are observed in the center of the molecule. This mainly affects the carbon−carbon bonds, while the influence of excitation on both the carbonyl group and the carbon−nitrogen bonds is negligible. This shows a transfer of electron density to the central part of the chromophore. The average bond elongation is caused by the stronger antibonding character of the LUMO. As mentioned in the previous section, due to the centrosymmetric shape of the chromophore, there should be neither a dipole moment in the ground nor in the excited state; however, the change in electron distribution upon excitation indicates a stronger local separation of charges which can then interact preferably with more polar solvents. The increase of local polarization is also illustrated by a small stretch which is observed for the carbonyl groups and which, in the valence bond picture, shows a higher weight of the zwitterionic border structure. Comparing the changes in bond length for the different solvents, we notice that this is much more 11649


Article


DMSO. Unfortunately, we found no evidence for a stabilization of twisted forms in the ground or the excited state in polar DMSO. We also have to point out that the computational model that has been used does not take into account vibronic couplings between the excited and the ground state, which offer additional relaxation channels.

Table 2. Electrochemical Data for All Investigated DPND Derivativesa dye

E1/2red/V

E1/2ox/V

ionization energy/eVd

electron affinity/ eVd

EgCV/ eV

1b 2 3 5 6 7 8 9

−1.223 −1.110 −1.010 −1.413 −1.224 −1.273 −1.013 −1.214

+0.550 +0.754 +0.714c +0.369 +0.525 +0.335 +0.835 +0.465

4.82 5.03 4.91 4.64 4.77 4.60 5.13 4.74

−3.15 −3.35 −3.47 −3.02 −3.20 −3.14 −3.40 −3.19

1.66 1.69 1.44 1.63 1.56 1.45 1.73 1.55

■

CONCLUSIONS Due to the electron-deficient character of the DPND core, the introduction of two amino groups at peripheral positions has a very strong effect on both the absorption and emission spectra of resulting dipyrrolonaphthyridinediones. The synthesized dyes, bearing highly electron-donating amino groups at positions 3 and 9, generally exhibit absorption in the red and emission in the red/NIR region of the spectrum. This combined experimental/theoretical study provides fundamental guidelines for the design of electron-rich dyes based on an accepting DPND core. Despite the centrosymmetric nature of the investigated derivatives, we found that the emission maxima depends on the polarity of the solvent, and this phenomenon was rationalized using both Lippert−Mataga and Reichhardt functions. All S1 states are of charge transfer character, and the calculations showed that polar solvents are able to provide stronger stabilization of the excited state due to the stabilization of charge separation, which in turn results in the decrease of the emission energy. Upon excitation, only minor changes in the geometry have been found, which do not give any indication of the charge transfer state being stabilized by TICT.

a

Measurement conditions: compound (c = 0.1−0.2 mM); electrolyte (NBu4ClO4, c = 0.1 M); solvent: dry, degassed CH2Cl2; potential sweep rate: 100 mV/s; working electrode: GC; auxiliary electrode: Pt wire; reference electrode: Ag/AgCl/NaClsat; all measurements were carried out at room temperature and under Ar atmosphere. bThe data were taken from ref 18. cThe Epa value of irreversible oxidation wave is given. dCalculated according to the equations: ionization energy (eV) = [Eoxonset − E1/2(Fc/Fc+) + 4.8]; electron affinity (eV) = −[Eredonset − E1/2(Fc/Fc+) + 4.8].

compared with 6. To rationalize the role of OMe groups, we consider mesomeric structures of 7 (Figure 5). We hypothesize that the presence of additional electron-donating OMe groups stabilizes a positive charge located on nitrogen in the II form; thus, we observe the above-mentioned bathochromic shift of both λabsmax and λemmax. In the case of compound 8, the presence of electron-withdrawing CN groups prevents such stabilization, thus leading to hypsochromic shift of the absorption band and similar values of emission wavelengths compared with 5. According to Table 1, compound 3 exhibits the strongest quenching effect upon an increase in solvent polarity; that is, in polar MeCN and DMSO, it shows no fluorescence at all. One possible explanation of this fact is the twisted intramolecular charge transfer (TICT)25 phenomenon. For this purpose, for dyes 1 and 3, we investigated possible TICT mechanisms through twisting of either the amino group on the benzene rings or the whole benzene rings in both cyclohexane and

■

EXPERIMENTAL SECTION

General Remarks. All reagents and solvents were purchased from commercial sources and were used as received unless otherwise noted. Reagent grade solvents (CH2Cl2, hexanes) were distilled prior to use. Toluene was dried over sodium and then distilled and stored under argon. Transformations with moisture and oxygen sensitive compounds were performed under a stream of argon. The reaction progress was monitored by means of thin-layer chromatography (TLC), which was performed on aluminum foil plates, covered with silica gel 60 F254 or aluminum oxide 60 F254 (neutral). Product purifications were done by means of column chromatography with

Figure 4. HOMO (bottom) and LUMO (top) shapes for molecules 6 and 8. Atom colors: nitrogen, blue; oxygen, red; carbon, gray; hydrogen, white. 11650


Article


Figure 5. Mesomeric structures of compound 7. Kieselgel 60 or aluminum oxide. The identity and purity of prepared compounds were proved by 1H NMR and 13C NMR spectrometry as well as by mass spectrometry (HRMS (ESI-TOF) and HRMS (EI): double-focusing magnetic sector instruments with EBE geometry were utilized). NMR spectra were measured on 500 MHz instruments with TMS as internal standard. All chemical shifts are given in ppm. All melting points for crystalline products were measured with an automated melting point apparatus and are given without correction. 4,4′-Dicyanodiphenylamine,26 4,16 and RuPhos Pd G327 were synthesized as described earlier. Optical Measurements. For the measurements of absorption and emission spectra, a typical UV/vis spectrophotometer and a spectrofluorimeter were used. All solvents were of spectrophotometric grade and used without further purification. Quartz cells (10 mm) were used for the measurements of absorption and emission spectra. As a standard, sulforhodamine 101 (Φfl = 0.95 in EtOH) and cresyl violet (Φfl = 0.54 in MeOH) were used to determine fluorescence quantum yields. Computational Studies. Theoretical calculations have been performed using the GAUSSIAN program28 using the CAM-B3LYP density functional29 and the def2-SVP basis set.30 Solvation effects were taken into account using the polarizable continuum model (PCM).31 Longer alkyl chains were replaced with Me groups. Synthesis of Bis(3,4,5-trimethoxyphenyl)amine. In a 50 mL Schlenk flask containing a magnetic stirring bar were placed: 5bromo-1,2,3-trimethoxybenzene (9.10 mmol, 2.25 g), 3,4,5-trimethoxyaniline (10.0 mmol, 2.00 g), RuPhos Pd G3 (20.0 mg, 0.024 mmol), BrettPhos (16.0 mg, 0.030 mmol), and Cs2CO3 (4.45 g, 13.65 mmol). Then, anhydrous and degassed toluene (10 mL) was added. The vessel was tightly closed and again carefully evacuated and backfilled with argon (3 times). The contents of the flask were stirred at 120 °C overnight. After this time the flask was cooled to RT, and all solvents were removed in vacuo. The crude product was solidified with diethyl ether, recrystallized from i-PrOH, and air-dried to give 2.70 g (85%) of the product as creamy crystals. mp 142−143 °C. 1H NMR (500 MHz, CDCl3) δ 6.30 (s, 4H), 5.55 (s, 1H), 3.81 (s, 6H), 3.80 (s, 12H). 13C NMR (125 MHz, CDCl3) δ 153.9, 139.6, 132.6, 95.7, 61.0, 56.0. HRMS (ESI) calcd for C18H23NO6Na 372.1423 [M + Na+], found 372.1415. Anal. Calcd for C18H23NO6: C, 61.88; H, 6.64; N, 4.01. Found: C, 61.97; H, 6.65; N, 4.01. General Procedure for Buchwald−Hartwig Amination and Analytical Data for All New Compounds. In a 25 mL Schlenk flask containing a magnetic stirring bar were placed: 4 (0.05 mmol, 1.0 eq, 30.0 mg), Pd2dba3 (4.2 mg, 0.02 mmol, 10 mol %), SPhos (4.0 mg, 0.04 mmol, 20 mol %), Cs2CO3 (65.2 mg, 0.2 mmol, 4.0 equiv) and, if a solid, the amine (0.15 mmol, 3 equiv). The vessel was evacuated and backfilled with argon (3 times). If morpholine (0.2 mmol, 4 equiv) was used, it was added next using a syringe followed by anhydrous, degassed toluene (1 mL). The vessel was tightly closed and again carefully evacuated and backfilled with argon (3 times). The content of the flask was stirred at 110 °C for typically 72 h. After the indicated time, the flask was cooled to RT; 5 mL of dichloromethane was added, and the obtained mixture was filtered through Celite. Then, all solvents were evaporated off, and the residue was purified by column chromatography. All further manipulations are described below. 6,12-Diheptyl-3,9-dimorpholino-5H,11H-dipyrrolo[1,2-b:1′,2′-g][2,6]naphthyridine-5,11-dione (5). Prepared using morpholine (17.4 mg, 17.2 μL, 0.2 mmol). Product was purified using column

chromatography (SiO2, CH2Cl2:methanol, 98:2). Compound can be recrystallized from n-hexane if needed. Yield: 17.5 mg (55%). Rf = 0.34 (SiO2, CH2Cl2/methanol, 98:2). mp 172−174 °C (dec). 1H NMR (500 MHz, C6D6) δ 6.59 (d, 2H, J = 4.0 Hz), 5.57 (d, 2H, J = 4.0 Hz), 3.78 (t, 8H, J = 4.5 Hz), 3.32−3.29 (m, 4H), 2.91 (t, 8H, J = 4.5 Hz), 1.86−1.81 (m, 4H), 1.63−1.57 (m, 4H), 1.43−1.33 (m, 12H), 0.93 (t, 6H, J = 7.0 Hz). 13C NMR (125 MHz, C6D6) δ 159.5, 149.8, 141.2, 130.4, 114.7, 114.6, 100.5, 66.5, 52.7, 32.3, 31.1, 30.7, 30.5, 29.5, 23.1, 14.4. HRMS (EI) calcd for C36H50N4O4 602.3832 [M·+], found 602.3823. Anal. Calcd for C36H50N4O4: C, 71.73; H, 8.36; N, 9.29. Found: C, 71.53; H, 8.19; N, 9.04. 3,9-Bis(diphenylamino)-6,12-diheptyl-5H,11H-dipyrrolo[1,2b:1′,2′-g][2,6]naphthyridine-5,11-dione (6). Prepared using bis(phenyl)amine (25.4 mg, 0.15 mmol). Product was purified using column chromatography (SiO2, CH2Cl2:hexanes, 1:2). Compound can be recrystallized from n-pentane if needed. Yield: 14.6 mg (33%). Rf = 0.48 (SiO2, hexanes/CH2Cl2, 2:1). mp 162−164 °C (dec). 1H NMR (500 MHz, C6D6) δ 7.07 (t, 8H, J = 7.5 Hz), 6.87 (t, 4H, J = 7.0 Hz), 6.43 (d, 2H, J = 3.5 Hz), 6.00 (d, 2H, J = 4.0 Hz), 2.96−2.92 (m, 4H), 1.56−1.53 (m, 4H), 1.40−1.30 (m, 16H), 0.93 (t, 6H, J = 7.0 Hz). 13C NMR (125 MHz, C6D6) δ 157.8, 146.6, 141.1, 140.2, 130.8, 128.9, 122.7, 122.2, 115.3, 113.6, 111.7, 32.0, 30.4, 29.7, 29.0, 22.8, 14.0. HRMS (EI) calcd for C52H54N4O2 766.4247 [M·+], found 766.4243. Note: eight missing aromatic hydrogens in 1H NMR spectra overlap with residue signal of C6D6. 3,9-Bis(bis(4-methoxyphenyl)amino)-6,12-diheptyl-5H,11Hdipyrrolo[1,2-b:1′,2′-g][2,6]naphthyridine-5,11-dione (7). Prepared using bis(4-methoxyphenyl)amine (34.5 mg, 0.15 mmol). Product was purified using column chromatography (SiO2, CH2Cl2:hexanes, 2:1). The residue after column was boiled in the minimal amount of methanol for 1 min, then the crystals were filtered on hot, washed with cold methanol and dried. Yield: 22.2 mg (50%). Rf = 0.41 (SiO2, CH2Cl2/hexanes, 2:1). mp 119−120 °C. 1H NMR (500 MHz, C6D6) δ 7.11 (d, 8H, J = 9.0 Hz), 6.71 (d, 8H, J = 8.5 Hz), 6.54 (d, 2H, J = 4.0 Hz), 6.03 (d, 2H, J = 4.0 Hz), 3.31 (s, 12H), 3.04−3.01 (m, 4H), 1.65−1.62 (m, 4H), 1.45−1.43 (m, 4H), 1.38−1.33 (m, 12H), 0.94 (t, 6H, J = 7.0 Hz). 13C NMR (125 MHz, C6D6) δ 158.0, 155.9, 141.9, 140.6, 140.3, 130.3, 123.8, 114.9, 114.4, 113.8, 109.7, 54.6, 32.1, 30.5, 30.4, 29.7, 29.0, 22.8, 14.1. HRMS (ESI) calcd for C56H63N4O6 887.4748 [M+H+], found 887.4729. Anal. Calcd for C56H62N4O6: C, 75.82; H, 7.04; N, 6.32. Found: C, 75.67; H, 7.18; N, 6.14. 3,9-Bis(bis(4-cyanophenyl)amino)-6,12-diheptyl-5H,11Hdipyrrolo[1,2-b:1′,2′-g][2,6]naphthyridine-5,11-dione (8). Prepared using bis(4-cyanophenyl)amine (32.9 mg, 0.15 mmol). Product was purified using column chromatography with gradient elution (SiO2, CH2Cl2 → CH2Cl2:methanol, 98:2). The residue after column was boiled in methanol for 5 min, then the crystals were filtered on hot, washed with hot methanol and dried. Yield: 11.1 mg (25%). Rf = 0.67 (SiO2, CH2Cl2). mp 261−263 °C. 1H NMR (500 MHz, C6D6, 60 °C) δ 6.98−6.96 (m, 8H), 6.63−6.61 (m, 8H), 6.37 (d, 2H, J = 4.0 Hz), 5.78 (d, 2H, J = 4.0 Hz), 2.87−2.84 (m, 4H), 1.35−1.27 (m, 20H), 0.90 (t, 6H, J = 7.0 Hz). 13C NMR (125 MHz, C6D6, 60 °C) δ 157.6, 148.0, 142.9, 136.8, 132.9, 131.7, 121.4, 117.9, 115.5, 114.0, 113.5, 107.2, 31.8, 30.3, 30.1, 29.6, 28.9, 22.6, 13.8. HRMS (EI) calcd for C56H50N8O2 866.4057 [M·+], found 866.4035. 3,9-Bis(bis(3,4,5-trimethoxyphenyl)amino)-6,12-diheptyl5H,11H-dipyrrolo[1,2-b:1′,2′-g][2,6]naphthyridine-5,11-dione (9). Prepared using bis(3,4,5-trimethoxyphenyl)amine (52.5 mg, 0.15 11651


Article

The Journal of Organic Chemistry mmol). Product was purified using column chromatography (SiO2, CH2Cl2:methanol, 98:2). The residue after column was boiled in methanol for 5 min, then the crystals were filtered on hot, washed with hot methanol and dried. Yield: 28.7 mg (51%). Rf = 0.56 (SiO2, CH2Cl2/methanol, 98:2). mp 186−188 °C. 1H NMR (500 MHz, C6D6) δ 6.63 (s, 8H), 6.59 (d, 2H, J = 4.0 Hz), 6.21 (d, 2H, J = 4.0 Hz), 3.86 (s, 12H), 3.29 (s, 24H), 3.05−3.02 (m, 4H), 1.70−1.64 (m, 4H), 1.49−1.43 (m, 4H), 1.39−1.28 (m, 12H), 0.92 (t, 6H, J = 7.5 Hz). 13C NMR (125 MHz, C6D6) δ 158.5, 154.6, 142.9, 141.3, 141.1, 130.9, 115.5, 114.4, 111.1, 101.7, 60.7, 55.9, 32.4, 31.0, 30.8, 30.3, 29.4, 23.0, 14.4. HRMS (ESI) calcd for C64H78N4O14Na 1149.5412 [M + Na+], found 1149.5386. Anal. Calcd for C64H78N4O14: C, 68.19; H, 6.97; N, 4.97. Found: C, 67.97; H, 6.81; N, 4.78.

■

infrared analyte-responsive fluorescent probes based on organic fluorophore platforms for fluorescence imaging. Chem. Soc. Rev. 2013, 42, 622−661. (4) Daehne, S.; Resch’Grenger, U.; Wolfbeis, O. S. Near-Infrared Dyes for High Technology Applications; Kuwer Academic Publishers: Dordrecht, 1998. (5) Tani, T.; Kikuchi, S. Calculation of the electronic energy levels of various photographic sensitizing and desensitizing dyes in emulsions. Photogr. Sci. Eng. 1967, 11, 129−144. (6) Kololuoma, T.; Oksanen, J. A. I.; Raerinne, P.; Rantala, J. T. Dye-doped sol-gel coatings for near-infrared laser protection. J. Mater. Res. 2001, 16, 2186−2188. (7) Emmelius, M.; Pawlowski, G.; Vollmann, H. W. Materials for Optical Data Storage. Angew. Chem., Int. Ed. Engl. 1989, 28, 1445− 1471. (8) (a) Shi, C.; Wu, J. B.; Pan, D. Review on near-infrared heptamethine cyanine dyes as theranostic agents for tumor imaging, targeting, and photodynamic therapy. J. Biomed. Opt. 2016, 21, 050901. (b) Tang, R.; Lee, H.; Achilefu, S. Induction of pH Sensitivity on the Fluorescence Lifetime of Quantum Dots by NIR Fluorescent Dyes. J. Am. Chem. Soc. 2012, 134, 4545−4548. (c) Lin, Y.; Weissleder, R.; Tung, C.-H. Novel Near-Infrared Cyanine Fluorochromes: Synthesis, Properties, and Bioconjugation. Bioconjugate Chem. 2002, 13, 605−610. (9) (a) Zeng, L.; Jiao, C.; Huang, X.; Huang, K.-W.; Chin, W.-S.; Wu, J. Anthracene-Fused BODIPYs as Near-Infrared Dyes with High Photostability. Org. Lett. 2011, 13, 6026−6029. (b) Yamazawa, S.; Nakashima, M.; Suda, Y.; Nishiyabu, R.; Kubo, Y. 2,3-Naphtho-Fused BODIPYs as Near-Infrared Absorbing Dyes. J. Org. Chem. 2016, 81, 1310−1315. (c) Zhao, W.; Carreira, E. M. Conformationally Restricted Aza-Bodipy: A Highly Fluorescent, Stable, Near-InfraredAbsorbing Dye. Angew. Chem., Int. Ed. 2005, 44, 1677−1679. (d) Zhao, W.; Carreira, E. M. Conformationally Restricted AzaBODIPY: Highly Fluorescent, Stable Near-Infrared Absorbing Dyes. Chem. - Eur. J. 2006, 12, 7254−7263. (e) Sheng, W.; Wu, Y.; Yu, C.; Bobadova-Parvanova, P.; Hao, E.; Jiao, L. Synthesis, Crystal Structure, and the Deep Near-Infrared Absorption/Emission of Bright AzaBODIPY-Based Organic Fluorophores. Org. Lett. 2018, 20, 2620−2623. (10) (a) Niu, G.; Liu, W.; Wu, J.; Zhou, B.; Chen, J.; Zhang, H.; Ge, J.; Wang, Y.; Xu, H.; Wang, P. Aminobenzofuran-Fused Rhodamine Dyes with Deep-Red to Near-Infrared Emission for Biological Applications. J. Org. Chem. 2015, 80, 3170−3175. (b) Sun, Y.-Q.; Liu, J.; Lv, X.; Liu, Y.; Zhao, Y.; Guo, W. Rhodamine-Inspired FarRed to Near-Infrared Dyes and Their Application as Fluorescence Probes. Angew. Chem., Int. Ed. 2012, 51, 7634−7636. (c) McCann, T. E.; Kosaka, N.; Koide, Y.; Mitsunaga, M.; Choyke, P. L.; Nagano, T.; Urano, Y.; Kobayashi, H. Activatable Optical Imaging with a SilicaRhodamine Based Near Infrared (SiR700) Fluorophore: A comparison with cyanine based dyes. Bioconjugate Chem. 2011, 22, 2531− 2538. (11) (a) Fischer, G. M.; Ehlers, A. P.; Zumbusch, A.; Daltrozzo, E. Near-Infrared Dyes and Fluorophores Based on Diketopyrrolopyrroles. Angew. Chem., Int. Ed. 2007, 46, 3750−3753. (b) Purc, A.; Koszarna, G.; Iachina, I.; Friese, D. H.; Tasior, M.; Sobczyk, K.; Pędziński, T.; Brewer, J.; Gryko, D. T. The impact of interplay between electronic and steric effects on the synthesis and the linear and non-linear optical properties of diketopyrrolopyrrole bearing benzofuran moieties. Org. Chem. Front. 2017, 4, 724−736. (c) Grzybowski, M.; Hugues, V.; Blanchard-Desce, M.; Gryko, D. T. Two-Photon-Induced Fluorescence in New π-Expanded Diketopyrrolopyrroles. Chem. - Eur. J. 2014, 20, 12493−12501. (d) Shimizu, S.; Iino, T.; Saeki, A.; Seki, S.; Kobayashi, N. Rational Molecular Design towards Vis/NIR Absorption and Fluorescence by using Pyrrolopyrrole aza-BODIPY and its Highly Conjugated Structures for Organic Photovoltaics. Chem. - Eur. J. 2015, 21, 2893−2904. (12) (a) Zhang, X.-D.; Wang, H.; Antaris, A. L.; Li, L.; Diao, S.; Ma, R.; Nguyen, A.; Hong, G.; Ma, Z.; Wang, J.; Zhu, S.; Castellano, J. M.; Wyss-Coray, T.; Liang, Y.; Luo, J.; Dai, H. Traumatic Brain Injury

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.8b01615. 1 H NMR and 13C NMR spectra, cyclic voltammograms, and detailed information on theoretical calculations (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (D.T.G.). *E-mail: [email protected] (D.H.F.). ORCID

Bartłomiej Sadowski: 0000-0002-1323-2826 Daniel T. Gryko: 0000-0002-2146-1282 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The work was financially supported by the Polish National Science Centre (PRELUDIUM 2016/23/N/ST5/ 00054), Foundation for Polish Science (TEAM/2016-3/22) and COST Action CA15106: C-H Activation in Organic Synthesis (CHAOS). This project received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska Curie Grant 751781 (D.H.F.). B.S. and D.T.G. thank Dr. Yevgen M. Poronik (Institute of Organic Chemistry PAS) for a sample of bis(3,4,5-trimethoxyphenyl)amine.

■

REFERENCES

(1) Kamkaew, A.; Lim, S. H.; Lee, H. B.; Kiew, L. V.; Chung, L. Y.; Burgess, K. BODIPY dyes in photodynamic therapy. Chem. Soc. Rev. 2013, 42, 77−88. (2) Yuan, A.; Wu, J.; Tang, X.; Zhao, L.; Xu, F.; Hu, Y. Application of near-infrared dyes for tumor imaging, photothermal, and photodynamic therapies. J. Pharm. Sci. 2013, 102, 6−28. (3) (a) Kiyose, K.; Kojima, H.; Nagano, T. Functional Near-Infrared Fluorescent Probes. Chem. - Asian J. 2008, 3, 506−515. (b) Barbieri, A.; Bandini, E.; Monti, F.; Praveen, V. K.; Armaroli, N. The Rise of Near-Infrared Emitters: Organic Dyes, Porphyrinoids, and Transition Metal Complexes. In Photoluminescent Materials and Electroluminescent Devices: Topics in Current Chemistry Collections; Armaroli, N., Bolink, H., Eds.; Springer: Cham, 2017. (c) Becker, A.; Hessenius, C.; Licha, K.; Ebert, B.; Sukowski, U.; Semmler, W.; Wiedenmann, B.; Grötzinger, C. Receptor-targeted optical imaging of tumors with near-infrared fluorescent ligands. Nat. Biotechnol. 2001, 19, 327−331. (d) Escobedo, J. O.; Rusin, O.; Lim, S.; Strongin, R. M. NIR dyes for bioimaging applications. Curr. Opin. Chem. Biol. 2010, 14, 64−70. (e) Yuan, L.; Lin, W.; Zheng, K.; He, L.; Huang, W. Far-red to near 11652


Article

The Journal of Organic Chemistry Imaging in the Second Near-Infrared Window with a Molecular Fluorophore. Adv. Mater. 2016, 28, 6872−6879. (b) Nakamura, M.; Kitatsuka, M.; Takahashi, K.; Nagata, T.; Mori, S.; Kuzuhara, D.; Okujima, T.; Yamada, H.; Nakae, T.; Uno, H. Yellow NIR dye: πfused bisbenzoBODIPYs with electron-withdrawing groups. Org. Biomol. Chem. 2014, 12, 1309−1317. (13) Langhals, H.; Zgela, D.; Lüling, R. Sexterrylenetetracarboxylic Bisimides: NIR Dyes. J. Org. Chem. 2015, 80, 12146−12150. (14) (a) Kim, E.; Park, S. B. In Advanced Fluorescence Reporters in Chemistry and Biology I; Demchenko, A. P., Ed.; Springer: Berlin, 2010, pp 150−186. (b) Grzybowski, M.; Głodkowska-Mrówka, E.; Stokłosa, T.; Gryko, D. T. Bright, Color-Tunable Fluorescent Dyes Based on π-Expanded Diketopyrrolopyrroles. Org. Lett. 2012, 14, 2670−2673. (c) Jiao, C.; Huang, K.-W.; Wu, J. Perylene-Fused BODIPY Dye with Near-IR Absorption/Emission and High Photostability. Org. Lett. 2011, 13, 632−635. (15) (a) Purc, A.; Sobczyk, K.; Sakagami, Y.; Ando, A.; Kamada, K.; Gryko, D. T. Strategy towards large two-photon absorption crosssections for diketopyrrolopyrroles. J. Mater. Chem. C 2015, 3, 742− 749. (b) Grzybowski, M.; Głodkowska-Mrówka, E.; Hugues, V.; Brutkowski, W.; Blanchard-Desce, M.; Gryko, D. T. Polar Diketopyrrolopyrrole-Imidazolium Salts As Selective Probes For Staining Mitochondria In Two-Photon Fluorescence Microscopy. Chem. - Eur. J. 2015, 21, 9101−9110. (c) Zhang, X.; Yu, H.; Xiao, Y. Replacing Phenyl Ring with Thiophene: An Approach to Longer Wavelength Aza-dipyrromethene Boron Difluoride (Aza-BODIPY) Dyes. J. Org. Chem. 2012, 77, 669−673. (16) Grzybowski, M.; Deperasiń s ka, I.; Chotkowski, M.; Banasiewicz, M.; Makarewicz, A.; Kozankiewicz, B.; Gryko, D. T. Dipyrrolonaphthyridinediones − structurally unique cross-conjugated dyes. Chem. Commun. 2016, 52, 5108−5111. (17) Sadowski, B.; Kita, H.; Grzybowski, M.; Kamada, K.; Gryko, D. T. π-Expanded Dipyrrolonaphthyridinediones with Large TwoPhoton Absorption Cross-Section Values. J. Org. Chem. 2017, 82, 7254−7264. (18) Sadowski, B.; Rode, M. F.; Gryko, D. T. Direct Arylation of Dipyrrolonaphthyridinediones Leads to Red-Emitting Dyes with Conformational Freedom. Chem. - Eur. J. 2018, 24, 855−864. (19) (a) Hartwig, J. F. Carbon−Heteroatom Bond-Forming Reductive Eliminations of Amines, Ethers, and Sulfides. Acc. Chem. Res. 1998, 31, 852−860. (b) Hartwig, J. F. Transition Metal Catalyzed Synthesis of Arylamines and Aryl Ethers from Aryl Halides and Triflates: Scope and Mechanism. Angew. Chem., Int. Ed. 1998, 37, 2046−2067. (c) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Rational Development of Practical Catalysts for Aromatic Carbon− Nitrogen Bond Formation. Acc. Chem. Res. 1998, 31, 805−818. (d) Yang, B. H.; Buchwald, S. L. Palladium-catalyzed amination of aryl halides and sulfonates. J. Organomet. Chem. 1999, 576, 125−146. (20) (a) Grimm, J. B.; English, B. P.; Chen, J.; Slaughter, J. P.; Zhang, Z.; Revyakin, A.; Patel, R.; Macklin, J. J.; Normanno, D.; Singer, R. H.; Lionnet, T.; Lavis, L. D. A general method to improve fluorophores for live-cell and single-molecule microscopy. Nat. Methods 2015, 12, 244−250. (b) Grimm, J. B.; Muthusamy, A. K.; Liang, Y.; Brown, T. A.; Lemon, W. C.; Patel, R.; Lu, R.; Macklin, J. J.; Keller, P. J.; Ji, N.; Lavis, L. D. A general method to fine-tune fluorophores for live-cell and in vivo imaging. Nat. Methods 2017, 14, 987−994. (21) Yang, J.-S.; Chiou, S.-Y.; Liau, K.-L. Fluorescence Enhancement of trans-4-Aminostilbene by N-Phenyl Substitutions: The “Amino Conjugation Effect. J. Am. Chem. Soc. 2002, 124, 2518−2527. (22) (a) Lippert, E. Z. Dipolmoment und Elektronenstruktur von angeregten Molekülen. Z. Naturforsch., A: Phys. Sci. 1955, 10, 541− 545. (b) Mataga, N.; Kaifu, Y.; Koizumi, M. The Solvent Effect on Fluorescence Spectrum, Change of Solute-Solvent Interaction during the Lifetime of Excited Solute Molecule. Bull. Chem. Soc. Jpn. 1955, 28, 690−691. (23) Reichardt, C. Solvatochromic Dyes as Solvent Polarity Indicators. Chem. Rev. 1994, 94, 2319−2358.

(24) (a) Dereka, B.; Rosspeintner, A.; Krzeszewski, M.; Gryko, D. T.; Vauthey, E. Symmetry-Breaking Charge Transfer and Hydrogen Bonding: Toward Asymmetrical Photochemistry. Angew. Chem., Int. Ed. 2016, 55, 15624−15628. (b) Terenziani, F.; Painelli, A.; Katan, C.; Charlot, M.; Blanchard-Desce, M. Charge Instability in Quadrupolar Chromophores: Symmetry Breaking and Solvatochromism. J. Am. Chem. Soc. 2006, 128, 15742−15755. (c) Dereka, B.; Vauthey, E. Solute−Solvent Interactions and Excited-State Symmetry Breaking: Beyond the Dipole−Dipole and the Hydrogen-Bond Interactions. J. Phys. Chem. Lett. 2017, 8, 3927−3932. (25) (a) Grabowski, Z. R.; Rotkiewicz, K.; Rettig, W. Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures. Chem. Rev. 2003, 103, 3899−4032. (b) Sasaki, S.; Drummen, G. P.; Konishi, G.-i. Recent advances in twisted intramolecular charge transfer (TICT) fluorescence and related phenomena in materials chemistry. J. Mater. Chem. C 2016, 4, 2731−2743. (26) Hu, L.; Kully, M. L.; Boykin, D. W.; Abood, N. Optimization of the central linker of dicationic bis-benzimidazole anti-MRSA and antiVRE agents. Bioorg. Med. Chem. Lett. 2009, 19, 3374−3377. (27) Bruno, N. C.; Tudge, M. T.; Buchwald, S. L. Design and preparation of new palladium precatalysts for C−C and C−N crosscoupling reactions. Chem. Sci. 2013, 4, 916−920. (28) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.; Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.; Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian 16, Revision B.01; Gaussian, Inc.: Wallingford CT, 2016. (29) Yanai, T.; Tew, D. P.; Handy, N. C. A new hybrid exchange− correlation functional using the Coulomb-attenuating method (CAMB3LYP). Chem. Phys. Lett. 2004, 393, 51−57. (30) Weigend, F.; Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297−3305. (31) Tomasi, J.; Mennucci, B.; Cammi, R. Quantum Mechanical Continuum Solvation Models. Chem. Rev. 2005, 105, 2999−3094.

11653


Electron-Rich Dipyrrolonaphthyridinediones: Synthesis and Optical

Recommend Documents