Journal of Molecular Structure 932 (2009) 43–54

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Journal of Molecular Structure

journal homepage: www.elsevier .com/ locate /molst ruc

Synthesis, spectroscopic, and molecular structure characterizations of some azoderivatives of 2-hydroxyacetophenone

Çigdem Albayrak a,*, _Ismail E. Gümrükçüoglu b, Mustafa Odabas�oglu c, Nazan Ocak _Iskeleli d, Erbil Agar b

a Faculty of Education, Sinop University, 57000 Sinop, Turkeyb Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit-Samsun, Turkeyc Chemistry Program., Pamukkale University, 20159 Kınıklı-Denizli, Turkeyd Department of Science Education, Ondokuz Mayıs University, 55200 Samsun, Turkey

a r t i c l e i n f o

Article history:Received 11 March 2009Received in revised form 21 May 2009Accepted 21 May 2009Available online 31 May 2009

Keywords:AzobenzeneAzo dyesX-ray analysisSpectral characterization2-Hydroxyacetophenone

0022-2860/$ - see front matter � 2009 Elsevier B.V. Adoi:10.1016/j.molstruc.2009.05.043

* Corresponding author. Fax: +90 368 271 55 30.E-mail address: cigdema@omu.edu.tr (Ç. Albayrak

a b s t r a c t

Some novel azo compounds were prepared by the reaction of 2-hydroxyacetophenone with aniline andits substituted derivatives. The structures of synthesized azo compounds were determined by IR, UV–Vis,1H NMR and 13C NMR spectroscopic techniques and the structures of some of these compounds were alsodetermined by X-ray diffraction studies. Structural analysis using IR in solid state shows that the azo formis favoured in the azo compounds whereas UV–Vis analysis of the azo compounds in solution has shownthat there is a azo and ionic form. The azo compounds in the basic solvents dimethylformamide (DMF)and dimethylsulfoxide (DMSO) are both azo and ionic form while these compounds in ethyl alcohol(EtOH) and chloroform (CHCl3) are only azo form.

� 2009 Elsevier B.V. All rights reserved.

1. Introduction

Azo compounds are the oldest and largest class of industriallysynthesized organic dyes due to their versatile application in vari-ous fields, such as dyeing textile fiber, biomedical studies, ad-vanced application in organic synthesis and high technologyareas as laser, liquid crystalline displays, electro-optical devicesand ink-jet printers [1–3]. There are about three thousand azo dyescurrently in use all over the world. The great majority of them aremonoazo compounds, which have the common structure unit ofthe azo chromophore, –N@N–, linking two aromatic systems. Thetextile industry is the largest consumer of dyestuffs. Althoughsome azo dyes have been reported to be toxic, dozens of additionalmonoazo dyes are permitted in drugs and cosmetics [4]. The phar-maceutical importance of the compounds including an arylazogroup has been extensively reported in the literature [5,6]. The oxi-dation–reduction behaviors of these compounds play an importantrole in its biological activity [7].

Our interest has been focused on preparation of some azo com-pounds and investigation of their spectroscopic properties, molec-ular structure.

ll rights reserved.

).

2. Experimental

2.1. Synthesis

Azo derivatives of (E)-2-acetyl-4-(phenyldiazenyl)phenol 4were synthesized by the azo-coupling reactions of substituted ben-zenediazonium salts 2 with 2-hydroxyacetophenone 3 shown inScheme 1 and Table 1. Substituted anilines 1 were diazotized usingsodium nitrite in the presence of hydrochloric acid followed bycoupling with 2-hydroxyacetophenone 3 to give (E)-2-acetyl-4-(phenyldiazenyl)phenol dyes 4 in good yield. The (E)-2-acetyl-4-(phenyldiazenyl)phenol 4 were purified by recrystallization fromsuitable solvents as mentioned below.

A mixture of aniline (4 g, 42.9 mmol), water (20 ml) and con-centrated hydrochloric acid (10.7 ml, 128 mmol) was stirred untila clear solution was obtained. This solution was cooled down to0–5 �C and a solution of sodium nitrite (2.96 g, 60.06 mmol) inwater was added dropwise while the temperature was maintainedbelow 5 �C. The resulting mixture was stirred for 30 min in an icebath. 2-hydroxyacetophenone (5.8 g, 42.9 mmol) solution (pH 9)was gradually added to a cooled solution of benzenediazoniumchloride, prepared as described above, and the resulting mixturewas stirred at 0–5 �C for 60 min in ice bath. The product wasrecrystallized from ethyl alcohol to obtain solid (E)-2-Acetyl-4-(phenyldiazenyl)phenol. Crystals of (E)-2-Acetyl-4-(phenyldiaze-nyl)phenol were obtained after one day by slow evaporation fromacetic acid (yield 78%, m.p. 114–115 �C).

Scheme 1. Some azo compounds synthesized from 2-hydroxyacetophenone.

44 Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54

2.2. Instrumentation

All melting points were taken with an electrothermal meltingpoint apparatus. FT-IR spectra were recorded on FTIR-8900

Table 1Properties of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4.

Compound Yield (%) Mp (�C) % C

Found Calcula

4a 78 114–115 69.62 (69.99)4b 84 141–143 64.38 (65.11)4c 86 148–150 64.82 (65.11)4d 80 151–153 60.84 (61.21)4e 79 112–114 60.84 (61.21)4f 84 172–174 60.66 (61.21)4g 52 150–152 52.43 (52.69)4h 55 116–118 52.36 (52.69)4i 78 185–187 52.24 (52.69)4j 74 195–197 46.12 (45.92)4k 45 104–106 70.64 (70.85)4l 83 137–139 70.15 (70.85)4m 56 88–90 70.83 (71.62)4n 45 77–79 72.78 (72.32)4o 40 82–83 72.64 (72.95)4p 58 148–150 66.65 (66.66)4r 63 102–104 66.22 (66.66)4s 67 127–128 66.54 (66.66)4t 56 135–137 66.98 (67.59)4u 88 179–181 59.25 (58.95)

Table 2UV–Vis absorption bands of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4.

Compounds EtOH CHCl3

Azo Anion Azo Anion

4a 335(38600) – 337(27700) –4b 341(39200) – 343(31200) –4c 336(41000) – 338(30300) –4d 341(32600) – 343(29900) –4e 340(47200) – 340(28300) –4f 341(41200) – 345(30800) –4g 344(33600) – 344(35600) –4h 342(36100) – 344(34000) –4i 342(52000) – 347(32400) –4j 350(55200) – 350(44800) –4k 339(41700) – 338(33700) –4l 339(35000) – 341(34300) –4m 341(50100) – 344(37800) –4n 342(59800) – 342(38000) –4o 342(63900) – 342(38100) –4p 356(37500) – 354(30000) –4r 337(35800) – 340(24700) –4s 352(52900) – 354(63900) –4t 353(47100) – 357(30800) –4u 365(37900) – 366(37000) –

Schmadzu spectrometer. Absorbtion spectra were determined onUnicam UV–Vis spectrometer. The 1H NMR and 13C NMR spectrawere taken on Bruker AC 200 MHz spectrometer. Crystal structureresults were taken with STOE IPDS II diffractometer. Elementalanalysis was recorded by TUBITAK Ankara test and analysislaboratory.

3. Results and discussion

3.1. UV–Vis absorption spectra

The UV–Vis electronic spectra of (E)-2-acetyl-4-(phenyldiaze-nyl)phenols 4 in various organic solvents (DMSO, DMF, EtOH andCHCl3) were recorded in the wavelength range 200–600 nm. Typi-cal characteristic UV–Vis absorption bands of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4 in DMSO, DMF, EtOH and CHCl3 are gi-ven in Table 2. Representative spectra are shown in Figs. 1 and 2.Examination of the results indicates that the UV–Vis electronic

% H % N

ted Found Calculated Found Calculated

5.661 (5.03) 11.53 (11.66)4.004 (4.29) 10.74 (10.85)3.738 (4.29) 10.82 (10.85)3.929 (4.04) 10.12 (10.20)3.684 (4.04) 10.04 (10.20)3.480 (4.04) 10.12 (10.20)3.142 (3.47) 8.72 (8.78)3.230 (3.47) 8.70 (8.78)2.873 (3.47) 8.696 (8.78)2.952 (3.03) 7.12 (7.65)5.140 (5.55) 10.84 (11.02)4.680 (5.55) 10.86 (11.02)6.59 (6.01) 10.13 (10.44)6.44 (6.43) 9.56 (9.92)6.94 (6.80) 9.39 (9.45)5.140 (5.22) 10.12 (10.36)4.443 (5.22) 10.34 (10.36)5.381 (5.22) 10.31 (10.36)6.140 (5.67) 9.842 (9.85)4.16 (3.89) 14.47 (14.73)

DMSO DMF

Azo Anion Azo Anion

346(37000) 463(35400) 344(16600) 464(17200)353(37400) 473(19000) 400(20600) 476(54400)351(16800) 464(19900) 400(27400) 464(55400)364(36400) 477(22500) 368(18400) 480(32900)352(25400) 477(17100) 396(19400) 479(59000)352(36500) 473(12800) 369(19100) 476(37800)374(20100) 480(33200) 382(18100) 479(33200)353(40200) 474(16800) 392(16100) 480(43000)356(36100) 477(25000) 355(28300) 477(26100)358(42000) 467(9600) 361(25200) 478(26900)344(44200) 443(5200) 342(24000) 460(13300)374(30200) 462(39700) 348(28300) 461(24200)351(30600) 452(6000) 355(19300) 464(25100)350(38100) 445(6500) 360(19100) 463(30000)349(38400) 453(5400) 352(21800) 463(26200)368(26900) 453(7600) 391(22700) 466(30200)345(45400) 464(16300) 358(19300) 466(20000)360(50500) 444(6200) 359(37500) 448(11000)364(34100) 461(13400) 363(30300) 459(17300)373(28600) 553(19300) 380(14900) 557(70200)

Fig. 1. The electronic spectra of 4a in (- - -) DMSO, (� � �� � �) DMF, (– –) CHCl3, (—)EtOH.

Fig. 2. The electronic spectra of 4a in DMF. (—) 6 � 10�5 M, (- - -) 4 � 10�5 M, (– –)2 � 10�5 M, (– �� –) 1 � 10�5 M.

Scheme 2. Two different forms of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4 insolution.

Fig. 3. The electronic spectra of 4a in DMF (—) and DMF + N-methylpiperazine (– –)for 6 � 10�5 M.

Fig. 4. The electronic spectra of 4u in (- - -) DMSO, (� � �� � �) DMF, (– –) CHCl3, (—)EtOH.

Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54 45

spectra of (E)-2-acetyl-4-(phenyldiazenyl)phenol 4a are largelydependent on both the nature of the solvent employed and theconcentration of solute dye.

In the UV–Vis spectra of these compounds two absorbtionbands are noteworthy in DMF and DMSO whereas in ethanol andchloroform only one absorption band were observed (Fig. 1). Thefirst band is at 330–400 nm and the second band is between 400and 500 nm. The UV–Vis spectra of (E)-2-acetyl-4-(phenyldiaze-nyl)phenol 4a in the basic solvents DMF showed an increase theabsorbtion band at 400–500 nm with decreasing concentration of(E)-2-acetyl-4-(phenyldiazenyl)phenol 4a whereas a diminution

the absorbtion band at 300–400 nm with decreasing concentrationof (E)-2-acetyl-4-(phenyldiazenyl)phenol 4a (Fig. 2). The addi-tional absorbtion band appearing in DMF and DMSO could be as-signed to absorbtion by the ionized form of the compound(Scheme 2). This is substantiated by the fact that the band due toanion increases with decreasing concentration of 4a. The appear-ance of this band only in DMF and DMSO is due to the high basicityof these solvents [8,9].

Evidence for effect of the basicity of DMF is recorded the spec-trum by dropping N-methylpiperazine in DMF where the band at400–500 nm is observed while the absorbtion band at 300–400 nm almost disappears (Fig. 3). Accordingly, the longer wave-length absorbtion band at 400–500 nm appearing in DMF andDMSO solutions is due to absorbtion by ionic form of thesecompounds.

(E)-2-Acetyl-4-(4-nitrophenyldiazenyl)phenol4u includingelec-tron-withdrawing substituent –NO2 group stabilize ionic form bydelocalizing the negative charge, thus making the azo molecule more

Fig. 5. The electronic spectra of 4s in (- - -) DMSO, (� � �� � �) DMF, (– –) CHCl3, (—)EtOH.

Table 3Characteristic IR absorption bands of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4.

Compound R mO–H (stretching) cm�1 mO–H (bending) cm�1 mC@O

H (4a) 2000–3000 1326 16372-F (4b) 2000–3000 1324 16404-F (4c) 2000–3000 1330 16472-Cl (4d) 2000–3000 1330 16383-Cl (4e) 2000–3000 1326 16384-Cl (4f) 2000–3000 1329 16412-Br (4g) 2000–3000 1330 16393-Br (4h) 2000–3000 1326 16414-Br (4i) 2000–3000 1328 16394-I (4j) 2000–3000 1327 16423-Me (4k) 2000–3000 1322 16384-Me (4l) 2000–3000 1327 16374-Et (4m) 2000–3000 1327 16464-Prn (4n) 2000–3000 1317 16454-Bun (4o) 2000–3000 1317 16462-OCH3 (4p) 2000–3000 1327 16363-OCH3 (4r) 2000–3000 1330 16384-OCH3 (4s) 2000–3000 1322 16394-OEt (4t) 2000–3000 1326 16404-NO2 (4u) 2000–3000 1318 1647

Fig. 6. The IR spe

46 Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54

acidic. For this reason, (E)-2-acetyl-4-(4-nitrophenyldiazenyl)phenol 4u is more ionic form than the other azo compounds (Fig. 4).

(E)-2-Acetyl-4-(4-methoxyphenyldiazenyl)phenol 4s with elec-tron-donating substituent –OCH3 group are less acidic because thissubstituent destabilize the ionic form and (E)-2-acetyl-4-(4-meth-oxyphenyldiazenyl)phenol 4s is less ionic form than the other azocompounds (Fig. 5).

3.2. IR absorption spectra

The characteristic IR absorption bands of (E)-2-acetyl-4-(phen-yldiazenyl)phenols 4 were determined in KBr disk. In the IR spectra(Table 3) of these compounds two bands are noteworthy, one inthe region 1630–1650 cm�1 attributed to m(C@O) and the otherin the region 1409–1433 cm�1 attributed to the m(N@N) stretchingfrequencies. In the IR spectra of the parent acetophenone showedthe presence of m(C@O) at 1686 cm�1 which shifted to lower fre-quencies 1630–1650 cm�1 in the noval azo compounds due tothe formation of strong intramolecular hydrogen bonding O–H� � �O in the structure. The IR spectra of these compounds showed

(stretching) cm�1 mC–O (stretching) cm�1 mN@N (stretching) cm�1

1216 14181215 14141221 14221217 14171213 14091218 14181217 14171212 14241216 14171212 14201210 14231221 14231223 14291202 14241202 14251219 14301218 14331207 14291213 14201206 1424

ctrum of 4c.

Fig. 7. The 1H NMR spectrum of 4c.

Fig. 8. The 1H NMR spectrum of 4c.

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Table 41H NMR signals of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4.

N

N OH

O

R1

23

4

5 6 7

8 9

10

1112

13

14

R H2 H3 H4 H5 H6 H8 H11 H12 H13 H14 CH2 CH2 CH2 CH3

H (4a) 7.816(dd) 7.541(t) 7.507(tt) 7.541(t) 7.816(dd) 8.327 (d) 7.089 (d) 7.984(dd) 2.68 12.287 – – – –J23 = 8.754 J32 = 8.754 J43 = 8.754 J56 = 8.754 J65 = 8.754 J812 = 2.378 J1112 = 8.906 J1211 = 8.906J24 = 1.644 J34 = 8.754 J45 = 8.754 J54 = 8.754 J64 = 1.754 J128 = 2.378

J42 = 1.644J46 = 1.644

2-F (4b) – 7.715(td) 7.473(tdd) 7.334(td) 7.589(ddd) 8.409(d) 7.160 (d) 8.042(dd) 2.727 12.327 – – – –J34 = 7.966 J43 = 7.966 J56 = 7.966 J65 = 7.966 J812 = 2.452 J1112 = 8.938 J1211 = 8.938JHF = 7.966 J45= 7.966 J54 = 7.966 JHF = 3.06 J128 = 2.452J35 = 1.734 JHF = 1.734 JHF = 1.734 J64 = 7.966

J46= 1.502

4-F (4c) 7.924(dd) 7.406(t) – 7.406(t) 7.924(dd) 8.373 (d) 7.140(d) 8.027 (dd) 2.719 12.243 – – – –J23 = 8.84 J32 = 8.84 J56 = 8.84 J65 = 8.84 J812 = 2.372 J1112 = 8.910 J1211 = 8.910JHF = 5.358 JHF = 8.84 JHF = 8.84 JHF = 5.358 J128 = 2.372

2-Cl (4d) – 7.626(dd) 7.509(td) 7.437(td) 7.662(dd) 8.390(d) 7.138(d) 8.01(dd) 2.702 12.319 – – – –J34 = 7.334 J43 = 7.334 J56 = 7.334 J65 = 7.334 J812 = 2.148 J1112 = 8.924 J1211 = 8.924J35 = 1.96 J45 = 7.334 J54 = 7.334 J64 = 1.96 J128 = 2.148

J46 = 1.96 J53 = 1.96

3-Cl (4e) 7.821(t) – 7.792(dt) 7.583(t) 7.567(dt) 8.367(d) 7.110 (d) 7.997(dd) 2.694 12.319 – – – –J26 = 2.348 J45 = 7.890 J56 = 7.890 J65 = 7.890 J812 = 2.420 J1112 = 8.93 J1211 = 8.93J24 = 2.348 J42 = 2.348 J54 = 7.890 J64 = 2.348 J128 = 2.420

J46 = 2.348 J62 = 2.348

4-Cl (4f) 7.622 (d) 7.861(d) – 7.861(d) 7.622 (d) 8.377 (d) 7.138 (d) 8.032 (dd) 2.713 12.294 – – – –J23 = 8.696 J32 = 8.696 J56 = 8.696 J65 = 8.696 J812 = 2.402 J1112 = 8.926 J1211 = 8.926

J128 = 2.402

2-Br (4g) – 7.6065(d) 7.431(t) 7.494(t) 7.8335(d) 8.412 (d) 7.156 (d) 8.022 (dd) 2.71 12.32 – – – –J34 = 7.8 J43 = 7.8 J56 = 7.8 J6 5 = 7.8 J812 = 2.4 J1112 = 8.8 J1211 = 8.8

J45 = 7.8 J54 = 7.8 J128 = 2.4

3-Br (4h) 7.959(s) – 7.717(d) 7.546(t) 7.887(d) 8.422(s) 7.146(d) 8.044(d) 2.72 12.32 – – – –J45 = 8.0 J54 = 8.0 J65 = 8.0 J1112 = 8.8 J1211 = 8.8

J56 = 8.0

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4-Br (4i) 7.798(s) 7.798(s) – 7.798(s) 7.798(s) 8.410(d) 7.158(d) 8.062 (dd) 2.728 12.31 – – – –J812 = 2.39 J1112 = 8.98 J1211 = 8.98

J128 = 2.39

4-I (4j) 7.633(d) 7.936(d) – 7.936(d) 7.633(d) 8.391(d) 7.144(d) 8.044 (dd) 2.72 12.29 – – – -J23 = 8.4 J32 = 8.4 J56 = 8.4 J65 = 8.4 J812 = 2.4 J1112 = 8.8 J1211 = 8.8

J128 = 2.4

3-Me (4k) 7.617 (s) – 7.305 (d) 7.415(t) 7.625(d) 8.332(d) 7.096(d) 7.983 (dd) 2.69 12.27 – – – 2.37J43 = 8.0 J54 = 8.0 J65 = 8.0 J812 = 2.0 J1112 = 8.8 J1211 = 8.8

J56 = 8.0 J128 = 2.0

4-Me (4l) 7.769(d) 7.374(d) – 7.374(d) 7.769(d) 8.363 (d) 7.134 (d) 8.029(dd) 2.7241 12.241 – – – 2.383J23 = 7.774 J32 = 7.774 J56 = 7.774 J65 = 7.774 J812 = 2.42 J1112 = 8.90 J1211 = 8.90

J128 = 2.42

4-Et (4m) 7.765(d) 7.372(d) – 7.372(d) 7.765(d) 8.338 (d) 7.111 (d) 8.001(dd) 2.69 12.252 – – 2.66 (q) 1.195 (t)J23 = 8.4 J32 = 8.4 J56 = 8.4 J65 = 8.4 J812 = 2.4 J1112 = 8.8 J1211 = 8.8 J = 7.6 J = 7.6

J128 = 2.4

4-Prn (4n) 7.773(d) 7.366(d) – 7.366(d) 7.773(d) 8.353 (d) 7.127 (d) 8.016(dd) 2.717 12.242 – 2.616(t) 1.612 (h) 0.892 (t)J23 = 8.0 J32 = 8.0 J56 = 8.0 J65 = 8.0 J812 = 2.0 J1112 = 8.8 J1211 = 8.8 J = 7.2 J = 7.2 J = 7.2

J128 = 2.0

4-Bun (4o) 7.749(d) 7.337(d) – 7.337(d) 7.749(d) 8.332(d) 7.109 (d) 7.995(dd) 2.701 12.245 2.613 (t) 1.548 (p) 1.285 (h) 0.869 (t)J23 = 8.4 J32 = 8.8 J56 = 8.8 J65 = 8.4 J812 = 2.0 J1112 = 8.8 J1211 = 8.8 J = 7.8 J = 7.8 J = 7.8 J = 7.8

J128 = 2.0

2-OMe (4p) – 7.219(d) 7.463(t) 7.000(t) 7.497(d) 8.313 7.109(d) 7.956(d) 2.696 – – – – 3.925J34 = 7.2 J43 = 7.2 J54 = 7.2 J65 = 7.2 J1112 = 8.8 J1211 = 8.8

J45 = 7.2 J56 = 7.2

3-OMe (4r) 7.360(t) – 7.098 (dt) 7.47641 (t) 7.460dt) 8.368 (d) 7.117 (d) 8.015 (dd) 2.709 12.29 – – – 3.821J24 = 1.322 J45= 7.762 J56 = 7.762 J65 = 7.762 J812 = 2.414 J1112 = 8.952 J1211 = 8.952J26 = 1.322 J42 = 1.322 J54 = 7.762 J62 = 1.322 J128 = 2.414

J46 = 1.322 J64 = 1.322

4-OMe (4s) 7.852(d) 7.104(d) – 7.104(d) 7.852(d) 8.322(d) 7.115 (d) 7.998 (dd) 2.717 12.207 – – – 3.841J23 = 8.8 J32 = 8.8 J5 6 = 8.8 J65 = 8.8 J812 = 1.6 J1112 = 8.8 J1211 = 8.8

J128 = 1.6

4-OEt (4t) 7.083(d) 7.839(d) – 7.839(d) 7.083(d) 8.320 (d) 7.118 (d) 8.001(dd) 2.713 11.976 – – 4.107 1.343J23 = 8.826 J32 = 8.826 J56 = 8.826 J65 = 8.826 J812 = 2.34 J1112 = 8.88 J1211 = 8.88 J1516 = 6.88 J1615 = 6.88

J128 = 2.34

4-NO2 (4u) 8.011(d) 8.386(d) – 8.386(d) 8.011(d) 8.432 (d) 7.158(d) 8.069(dd) 2.719 12.378 – – – –J23 = 8.8 J32 = 8.8 J56 = 8.8 J65 = 8.8 J812 = 2.4 J1112 = 8.8 J1211 = 8.8

J128 = 2.4

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Table 513C NMR signals of (E)-2-acetyl-4-(phenyldiazenyl)phenols 4.

N

N OH

O

R1

23

4

5 6 7

8 9

10

1112

13

14

R C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 13 C14 CH2 CH2 CH2 CH3

H (4a) 151.82 122.36 129.39 131.10 129.39 122.36 144.45 128.08 121.07 163.01 118.80 127.85 .30 174.94 – – – –4-F (4c) 148.61 124.67 116.43 163.63 116.287 124.540 144.38 127.92 121.28 162.98 118.87 127.92 .42 174.99

JC2F = 9.1 JC3F = 22.9 JC4F = 252 JC5F = 22.9 JC6F = 9.12-Cl (4d) 147.91 133.65 130.86 132.44 129.27 117.67 144.87 128.23 121.61 163.49 119.16 127.71 .63 175.27 – – – –3-Cl (4e) 152.85 122.60 134.24 131.28 130.66 120.70 144.28 128.88 121.23 163.54 119.00 127.94 .46 203.51 – – – –4-Cl (4f) 150.22 129.71 124.16 135.69 124.16 129.71 144.47 128.07 121.45 160.62 119.02 125.76 .39 175.75 – – – –2-Br (4g) 149.16 118.14 132.93 134.17 127.97 124.79 145.06 129.69 121.82 163.85 119.47 129.09 .87 203.64 – – – –3-Br (4h) 153.35 123.79 123.47 133.90 131.97 122.98 144.68 129.17 121.73 163.83 119.36 128.32 .85 203.85 – – – –4-Br (4i) 150.86 124.35 132.62 124.57 132.62 124.35 144.45 128.43 121.44 163.26 119.04 127.99 .60 174.56 – – – –4-I (4j) 151.60 124.66 138.83 98.80 138.83 124.66 144.82 128.73 121.75 163.61 119.35 128.38 .87 203.86 – – – –3-Me (4k) 152.30 122.83 139.27 132.15 129.57 115.09 144.88 128.51 121.33 163.43 119.20 128.19 .60 204.03 – – – 21.324-Me (4l) 149.94 122.45 130.01 141.41 130.01 122.45 144.51 127.88 121.15 162.83 118.85 127.88 .42 174.88 – – – 21.084-Et (4m) 150.51 122.91 129.14 144.91 129.14 122.91 147.85 128.30 121.43 163.25 119.20 128.22 .49 204.02 – – 28.70 15.724-Prn (4n) 150.57 122.82 129.75 144.96 129.75 122.82 146.31 128.25 121.54 163.22 119.22 128.25 .75 204.01 – 37.47 24.29 14.044-Bun (4o) 150.50 122.83 129.64 144.93 129.64 122.83 146.48 128.29 121.45 163.25 119.19 128.19 .70 203.98 35.11 33.32 22.21 14.192-OCH3 (4p) 141.70 156.89 113.77 133.00 116.71 120.93 145.42 128.65 121.47 163.23 119.20 128.05 .74 203.91 – – – 56.383-OCH3 (4r) 150.10 105.79 160.10 117.46 130.32 116.21 144.38 128.28 127.85 163.10 118.86 127.85 .37 174.98 – – – 55.374-OCH3 (4s) 146.47 124.76 115.02 162.90 115.02 124.76 144.98 128.22 121.45 162.16 119.17 127.82 .70 204.15 – – – 56.064-OEt (4t) 146.02 124.46 115.10 161.16 115.10 124.46 144.58 127.94 121.13 162.54 118.86 127.43 .34 174.76 – – 63.77 14.684-NO2 (4u) 155.57 125.50 123.70 148.57 123.70 125.50 144.97 129.60 122.03 164.31 119.50 128.52 .01 203.50 – – – –

50Ç.A

lbayraket

al./Journalof

Molecular

Structure932

(2009)43–

54

C

2828

2828282828282828282828282828282829

Fig. 9. 13C NMR spectrum of 4c.

Fig. 10. 13C NMR spectrum of 4c.

Table 6Crystal data of 4c.

Empirical formula C14H11FN2O2Formula mass 258.25Crystal system OrthorhombicSpace group Pna21a (A) 12.6706(9)b (A) 3.8698(2)c (A) 25.230(2)P (�) 90.00v (Å3) 1237.08(15)Z 4Pcalc. (g cm�1) 1.39l (mm�1) 0.105R1/wR2 (obsd data:2r(I)] 0.039/0.080R1/wR2 (all data) 0.062/0.087Goodness of fit 0.888

Table 7Fractional atomic coordinates and equivalent isotropic displacement parameters (Å2)Ueq ¼ ð1=3RiRjUijaiajaiajÞ.

x y z Ueq

C1 0.11688 (18) 0.5419 (6) 0.35815 (9) 0.0480 (5)C2 0.1349 (2) 0.4495 (7) 0.41036 (9) 0.0611 (7)C3 0.0588 (2) 0.5055 (7) 0.44874 (10) 0.0712 (8)C4 �0.0340 (2) 0.6558 (7) 0.43300 (11) 0.0686 (7)C5 �0.0543 (2) 0.7515 (7) 0.38212 (10) 0.0621 (6)C6 0.02165 (17) 0.6957 (6) 0.34454 (10) 0.0527 (6)C7 0.26150 (17) 0.4605 (6) 0.23840 (9) 0.0457 (5)C8 0.24498 (17) 0.5539 (5) 0.18664 (9) 0.0468 (5)C9 0.32210 (16) 0.5057 (5) 0.14796 (9) 0.0484 (5)C10 0.41826 (16) 0.3545 (6) 0.16382 (9) 0.0534 (6)C11 0.43418 (17) 0.2545 (6) 0.21583 (9) 0.0548 (6)C12 0.35718 (16) 0.3048 (6) 0.25278 (9) 0.0522 (6)C13 0.30541 (19) 0.6062 (6) 0.09251 (9) 0.0573 (6)C14 0.2035 (2) 0.7571 (7) 0.07490 (11) 0.0686 (6)N1 0.19983 (15) 0.4693 (4) 0.32207 (8) 0.0511 (5)N2 0.17785 (14) 0.5296 (5) 0.27431 (8) 0.0501 (5)O1 0.49717 (13) 0.2972 (5) 0.12904 (9) 0.0787 (6)O2 0.37695 (16) 0.5621 (5) 0.05974 (7) 0.0889 (6)F1 �0.10834 (15) 0.7155 (5) 0.47095 (7) 0.1083 (6)

Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54 51

also the presence of m(C–O) stretching in the region 1206–1223 cm�1 and also gave a band located at about 2000–3000 cm�1 assigned to m(O–H) frequency. All this values are inaccordance with the literature [10,11]. Fig. 6 shows the IR spec-trum of compound 4c.

3.3. NMR investigations

The 1H NMR spectra of the azo compounds were recorded inDMSO-d6. The typical 1H NMR spectrum of the compound 4c is

Table 8Selected geometric parameters for 4c (Å, �).

4c

O1—C10 1.349 (3)O2—C13 1.239 (3)N1—N2 1.259 (2)N2—C7 1.420 (3)N1—C1 1.418 (3)O1—C10—C11 117.6 (2)O1—C10—C9 121.6 (2)C8—C7—N2 116.38 (17)C12—C7—N2 124.2 (2)O2—C13—C9 119.6 (2)C6—C1—N1 124.8 (2)C2—C1—N1 115.9 (2)C7—N2—N1—C1 179.29 (19)

Fig. 11. A view of 4c, with the atom numbering scheme. Displ

Fig. 12. A partial diagram for 4c, with O–H� � �O, C–H� � �O and C–H� � �N hydrogen bonds aninteractions have been omitted. [symmetry codes: (i) 1/2 � x, 1/2 � y, z + 1/2; (ii) x + 1/2

Table 9Some X-ray parameters of some (E)-2-acetyl-4-(phenyldiazenyl)phenols 4derivatives.

Compound Dihedral angle (�) Intramolecular hydrogen bond Ref.

Length (ÅA0

) Angle (�)

4a 3.48(15) 2.550(3) 146 [14]4c 1.26(8) 2.535(3) 151(3) This paper4d 3.73(9) 2.5327(19) 146 [15]4e 0.73(16) 2.547(2) 146 [16]4t 10.14(4) 2.555(4) 146 [17]

52 Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54

shown in Fig. 7. In the 1H NMR spectra, all azo compounds 4 showone peak at 2.67–2.73 ppm which belongs to methyl protons ofacetyl group. 1H NMR spectra of azo compounds show d peaks at8.30–8.44 ppm, d at 7.09–7.17 ppm and dd at 7.95–8.1 ppm, which

acement ellipsoids are drawn at the 50% probability level.

d shown as dashed lines. The atom numbering scheme. H atom not involved in these, y � 1/2, z + 1/2; (iii) 1 � x, 1 � y, z + 1/2; (iv) 1/2 � x, 3/2 � y, z].

Fig. 13. A partial packing diagram for 4c, with O–H� � �O, C–H� � �O and C–H� � �N hydrogen bonds shown as dashed lines. The atom numbering scheme. H atom not involved inthese interactions have been omitted. [symmetry codes: (i) 1/2 � x, 1/2 � y, z + 1/2; (ii) x + 1/2, 3/2 � y, z; (iii) x + 1/2, 1/2 � y, z].

Table 10Hydrogen-bonding geometry (ÅA

0

, �) for 4c.

D–H� � �A D–H H� � �A D� � �A D–H� � �A

4c O1–H1� � �O2 0.96(4) 1.65(4) 2.535(3) 151(3)C3–H3� � ��O2a 0.93 2.51 3.384(3) 157.1C5–H5� � ��N1b 0.93 2.73 3.628(3) 163.7C11–H11� � �N2c 0.93 2.69 3.594(3) 165.6

a 1/2 � x, y � 1/2, 1/2 + z.b x � 1/2, 3/2�y, z.c 1/2 + x, 1/2 � y, z.

Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54 53

are attributed to the phenyl group bearing acetyl group. Theresonance of hydroxyl proton is at 11–12 ppm which is typicalfor intramolecular hydrogen bonding (O–H� � �O) proton.

In contrast to the other p-substituted azo compounds, in 1HNMR spectra of 4c, since the F nucleus couples to H2, H6 and H3,H5 protons, they, respectively, give a quartet and a triplet(Fig. 8). Coupling constants for proton-fluorine are differentbecause the fluorine atom couples differently to the ortho-, meta-and para-protons. The triplet can be shown as a result of consecu-tive splitting of the H3, H5 absorbtion by the H2, H6 and F nucleus.The peaks overlap since the coupling constants are identical(JHF = J3,2 = 8.84 Hz). The H2, H6 protons are coupled to both theH3, H5 protons and F nucleus and show doublet of doublets(J2,3 = 8.84 Hz, JHF = 5.36 Hz). This result is in accordance with theliterature [10,11]. The chemical shift values are shown in Table 4.

In the 13C NMR spectra of azo compounds were recorded inDMSO carbonyl carbons (C14) in the azo compounds observed inthe range 174–204 ppm, and phenolic carbons (C10) appear at162–164 ppm. The chemical shifts of carbons for azo compounds

are shown in Table 5. The 13C NMR spectra of azo compounds showpeaks at 127.7–128.9 ppm (C8), at 118.7–119.2 ppm (C11) and at125.7–128 ppm (C12), which are attributed to phenyl group bear-ing acetyl functionality. The 13C NMR spectrum of 4c is shown inFig. 9. As in the 1H NMR spectra of 4c, the F nucleus couples to car-bons of fluorine-containing aromatic ring and C4 and C2,C6 andC3,C5 carbons give a doublet in the 13C NMR spectra (Fig. 10). Cou-pling constants for carbon–fluorine are different as the fluorineatom couples differently to the ipso-, ortho-, meta- and para-car-bons. Coupling constants for carbon–fluorine are given in Table 5.This result is in accordance with the literature [10,11]. The chem-ical shift values of 4 compounds are summarized in Table 5.

3.4. Description of the crystal structures

A summary of crystallographic data, experimental details, andrefinement results for 4c are given in Table 6. The atomic coordi-nates with their isotropic displacement parameters of non-hydro-gen atoms are listed in Table 7. Table 8 shows the selected bonddistances and bond angles for 4c. SHELXS-97 [12] and SHELXL-97[13] were used for the structure solution and refinement.

The molecular structure of compound 4c is shown in Fig. 11with the atom numbering scheme. The compound consists oftwo aromatic rings (C1–C6 and C7–C12), and an azo frame (C1–N1–N2–C7). In 4c, the aromatic rings, which adopt a trans config-uration about the N@N double bond, are nearly coplanar, with adihedral angle of 1.26(8)� between them. In our previous X-rayinvestigation, it has also been shown that, the other (E)-2-acetyl-4-(phenyldiazenyl)phenols are nearly coplanar and the dihedralangles of these compounds are as in Table 9 [14–17].

54 Ç. Albayrak et al. / Journal of Molecular Structure 932 (2009) 43–54

The (E)-2-acetyl-4-(4-fluorophenyldiazenyl)phenol moleculesare linked into [S(6)R4

4(34)] motifs [18] (Fig. 12). A significant intra-molecular interaction is noted, involving phenolic atom H and car-bonyl atom O1, such that a six-membered ring is formed S(6) andthe weak intermolecular C–H� � �O and C–H� � �N hydrogen bonds re-sult in the formation R4

4(34) ring motif (Fig. 12 and 13, Table 10).The C13–O1 double bond distance in 4c is also consistent withthe value of the C@O double bond in carbonyl compounds [19].The C10–O1, –N1@N2–, C1–N1 and C7–N2 bond lengths are con-sistent with values observed in related compounds [14–17,20–24].

4. Conclusion

In the present work, we report the synthesis and characteriza-tion of some substituted azo compounds using microanalyses(C,H,N), IR, UV–Vis, 1H and 13C NMR spectroscopic techniques.The structures of some of these compounds were determined byX-ray diffraction studies. In the IR spectra of substituted azo com-pounds, the m(C@O) and m(N@N) bands are observed at 1630–1650 cm�1 and 1409–1433 cm�1, respectively.

In the 13C NMR spectra of these azo compounds the carbonylcarbon (C14) resonates at 174–204 ppm. Furter data are presentedin Table 5. In the 1H NMR spectra, the resonance of hydroxyl protonat 11–12 ppm is due to the presence of intramolecular hydrogenbonding m(O–H� � �O) frequencies in the structure.

X-ray investigations show that the (E)-2-acetyl-4-(phenyldiaze-nyl)phenols the aromatic rings, which adopt a trans configurationabout the N@N double bond are nearly coplanar. The (E)-2-acet-yl-4-(4-fluorophenyldiazenyl)phenol molecules are linked into[S(6)R4

4(34)] motifs. A significant intramolecular interaction isnoted, involving phenolic atom H and carbonyl atom O, such thata six-membered ring is formed.

Appendix Supplementary. material

Crystallographic data (excluding structure factors) for the struc-tures in this paper have been deposited with the CambridgeCrystallographic Data Centre as the supplementary publication

no. CCDC 712626. Copies of the data can be obtained, free ofcharge, on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: +44-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk). Supplementary data associated with this article canbe found, in the online version, at doi:10.1016/j.molstruc.2009.05.043.

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