Chemistry of Heterocyclic Compounds 2016, 52(2), 110–115
In conclusion, we have prepared a series of donor–
H-6); 8.46 (1H, d, J = 9.0, H-5); 8.28–8.35 (2H, m, H Ar);
7.79–7.84 (4H, m, H Ar); 7.68–7.70 (2H, m, H Ar); 7.37–
7.67 (6H, m, H Ar). 13C NMR spectrum, δ, ppm: 183.5
(C=O); 183.4 (C=O); 155.2; 154.3; 143.0; 138.3; 138.1;
135.1 (2C); 134.5; 133.5; 132.2; 130.4; 129.8 (2C); 129.7;
128.5 (2C); 127.3; 126.7; 126.6. Mass spectrum, m/z (Irel, %):
411 (100), 412 [M]+ (85). Found, %: C 81.50; H 3.93;
N 6.80; O 7.77. C28H16N2O2. Calculated, %: C 81.54;
H 3.91; N 6.79; O 7.76.
acceptor type 2,3-disubstitued naphtho[2,3-f]quinoxaline-
7,12-dione derivatives with excellent yield. The absorption
spectra of all studied compounds show the presence of
intramolecular charge transfer transition bands. The
electron affinities (LUMO energy levels) of the synthesized
compounds are comparable to those of electron-trans-
porting/injecting materials reported in literature. The
investigated compounds have high melting points and good
thermal stability. Therefore, these compounds are potential
candidates for electron-transporting/injecting applications
in organic electronics.
2,3-Bis(4-methylphenyl)naphtho[2,3-f]quinoxaline-
7,12-dione (2). Yield 95%, orange solid, mp 278°C (mp
263–265°C12). IR spectrum, ν, cm–1: 3082, 2926, 2852,
1666, 1587, 1265. 1H NMR spectrum, δ, ppm (J, Hz): 8.58
(1H, d, J = 9.0, H-6 ); 8.41 (1H, d, J = 9.0, H-5); 8.26–8.33
(2H, m, H Ar); 7.71–7.82 (4H, m, H Ar); 7.59 (2H, d,
J = 9.0, H Ar); 7.19 (4H, d, J = 9.0, H Ar); 2.40 (6H, s,
CH3). 13C NMR spectrum, δ, ppm: 183.5 (C=O); 183.4
(C=O); 155.1; 154.2; 142.9; 139.9; 138.4; 137.9; 135.6;
135.4; 135.2 (2C); 134.9; 134.4; 133.4; 132.2; 130.3;
129.7; 129.3; 129.2 (2C); 127.3; 126.6; 126.3; 21.4 (CH3).
Mass spectrum, m/z (Irel, %): 440 [M]+ (80), 425 [M−CH3]+
(100). Found, %: C 81.78; H 4.60; N 6.34; O 7.27.
C30H20N2O2. Calculated, %: C 81.80; H 4.58; N 6.36; O 7.26.
2,3-Bis(4-methoxyphenyl)naphtho[2,3-f]quinoxaline-
7,12-dione (3). Yield 96%, red solid, mp 235°C.
IR spectrum, ν, cm–1: 3065, 2926, 1659, 1602, 1513, 1286,
Experimental
UV-Vis spectra were recorded on a Shimadzu UV-2401
PC spectrophotometer at room temperature in 10–5
M
solution (quartz cuvette, path length 1 cm) or in thermally
deposited thin solid film. The fluorescence emission
spectra were recorded on a Perkin Elmer LS 55 spectro-
fluorimeter. Fourier-transform IR spectra were recorded on
1
a Perkin Elmer Frontier 91579 instrument in KBr. H and
13C NMR spectra were recorded on a Bruker 300
Ultrashield spectrometer (300 and 75 MHz, respectively) in
CDCl3 with TMS as internal standard. Mass spectra were
recorded on a Thermo Scientific Polaris Q GC-MS
instrument. Elemental analysis was carried out on a Euro
EA 3000 elemental analyzer. Melting points were
determined by DSC. TGA and DSC experiments were
performed on a Metler–Toledo instrument under nitrogen
atmosphere. Column chromatography was carried out using
SD−Fine silica gel (60−120 mesh), eluting with n-hexane
and chloroform. Cyclic voltammetry studies were carried
out on a computer-controlled PalmSens3 potentiostat/
galvanostat. Typically, a three-electrode cell, equipped
with a glassy carbon working electrode, Ag/AgCl (non-
aqueous) reference electrode, and Pt wire as counter
electrode, was employed. The measurements have been
carried at room temperature in anhydrous dichloromethane
(10–3 M) with Bu4NPF6 (0.1 M) as supporting electrolyte
and a scan rate 100 mV × s–1. The potential of Ag/AgCl
reference electrode was calibrated by using ferrocene/
ferrocenium redox couple which has the known oxidation
potential of +4.8 eV.9,22
1
1248. H NMR spectrum, δ, ppm (J, Hz): 8.56 (1H, d,
J = 9.0, H-6); 8.36 (1H, d, J = 9.0, H-5); 8.26–8.33 (2H, m,
H Ar); 7.66–7.83 (6H, m, H Ar); 6.90–6.94 (4H, m, H Ar);
3.85 (6H, s, OCH3). 13C NMR spectrum, δ, ppm: 183.6
(C=O); 183.4 (C=O); 161.0; 154.5; 153.6; 142.8; 138.4;
135.1; 134.9; 134.8; 134.4; 133.4; 132.2; 131.9; 131.3;
131.0; 130.6; 129.2; 127.2; 126.6; 126.1; 55.3 (OCH3).
Mass spectrum, m/z (Irel, %): 472 [M]+ (100), 441
[M−OCH3]+ (70). Found, %: C 76.30; H 4.20; N 5.95;
O 13.58. C30H20N2O4. Calculated, %: C 76.26; H 4.27;
N 5.93; O 13.54.
2,3-Bis(4-bromophenyl)naphtho[2,3-f]quinoxaline-
7,12-dione (4). Yield 93%, orange solid, mp 302°C.
IR spectrum, ν, cm–1: 3069, 2920, 1665, 1582, 1328.
1H NMR spectrum, δ, ppm (J, Hz): 8.66 (1H, d, J = 9.0,
H-6); 8.45 (1H, d, J = 9.0, H-5); 8.29–8.35 (2H, m, H Ar);
7.78–7.88 (2H, m, H Ar); 7.67–7.71 (2H, m, H Ar); 7.54–
7.58 (6H, m, H Ar). 13C NMR spectrum, δ, ppm: 183.3
(C=O); 183.2 (C=O); 153.7; 152.8; 142.9; 137.0; 136.6;
135.7; 135.0; 134.6; 133.6; 132.1; 132.0; 131.8; 131.3;
127.3; 127.0; 126.7; 124.8. Mass spectrum, m/z (Irel, %):
570 [M]+ (98), 491 [M−Br]+ (100). Found, %: C 58.80;
H 2.49; Br 28.05; N 4.92; O 5.58. C28H14Br2N2O2.
Calculated, %: C 58.98; H 2.47; Br 28.03; N 4.91; O 5.61.
2,3-Bis(4-fluorophenyl)naphtho[2,3-f]quinoxaline-
7,12-dione (5). Yield 94%, orange solid, mp 291°C.
IR spectrum, ν, cm–1: 3070, 2921, 1667, 1591, 1504, 1220.
1H NMR spectrum, δ, ppm (J, Hz): 8.65 (1H, d, J = 9.0,
H-6); 8.44 (1H, d, J = 9.0, H-5); 8.29–8.35 (2H, m, H Ar);
7.78–7.88 (4H, m, H Ar); 7.67–7.70 (2H, m, H Ar); 7.08–
7.15 (4H m, H Ar). 13C NMR spectrum, δ, ppm: 183.5
(C=O); 183.3 (C=O); 153.8; 152.9; 142.9; 138.5; 135.5;
135.0; 134.6; 133.3; 132.5; 132.3; 132.1; 131.9; 131.8;
The progress of reactions and the purity of the products
were checked by TLC on silica gel-coated glass plates. The
spots were visualized with UV light and in iodine chamber.
Preparation of 2,3-diarylnaphtho[2,3-f]quinoxaline-
7,12-diones 1–5 (General method). A mixture of benzil
derivative 7 (1.0 mmol) and 1,2-diaminoanthraquinone (6)
(0.238 g, 1 mmol) was dissolved in glacial acetic acid
(20 ml) and refluxed for 5 h. The reaction mixture was
allowed to cool and then poured onto crushed ice to obtain the
orange to red colored solid which was dried under vacuum and
purified using column chromatography (eluent n-hexane–
CHCl3, 3:2) to obtain a bright-orange to red solid.
2,3-Diphenylnaphtho[2,3-f]quinoxaline-7,12-dione (1).
Yield 93%, orange solid, mp 282°C (mp 272–275°C11).
IR spectrum, ν, cm–1: 3083, 2921, 2851, 1651, 1581, 1265.
1H NMR spectrum, δ, ppm (J, Hz): 8.64 (1H, d, J = 9.0,
114