FT-IR and NMR investigation of 2-(1-cyclohexenyl)ethylamine: A combined experimental and theoretical study

Spectrochimica Acta Part A 68 (2007) 55–62

FT-IR and NMR investigation of 2-(1-cyclohexenyl)ethylamine: A combined experimental and theoretical study ¨ Alver a,b , C. Parlak a,b,∗ , M.T. Aytekin a , M. S¸enyel a T. ˙Izgi a , O. a

b

Department of Physics, Science Faculty, Anadolu University, Eski¸sehir, Turkey Plant, Drug and Scientific Research Centre, Anadolu University, Eski¸sehir, Turkey Received 10 October 2006; accepted 27 October 2006

Abstract FT-IR and 1 H, 13 C, DEPT, HETCOR, COSY, and NOESY NMR spectra of 2-(1-cyclohexenyl)ethylamine (CyHEA) have been reported for the first time. The vibrational frequencies and 1 H, 13 C NMR chemical shifts of CyHEA (C8 H15 N) have been calculated by means of the Hartree–Fock (HF), Becke–Lee–Yang–Parr (BLYP) and Becke-3–Lee–Yang–Parr (B3LYP) density functional methods with 6-31G(d) and 6-31G(d,p) basis sets, respectively. The comparison between the experimental and the theoretical results indicates that density functional B3LYP method is superior to the scaled HF and BLYP approach for vibrational frequencies and predicting NMR properties. © 2006 Elsevier B.V. All rights reserved. Keywords: 2-(1-Cyclohexenyl)ethylamine; IR spectra; NMR spectra; HF; DFT

1. Introduction 2-(1-Cyclohexenyl)ethylamine molecule consists of cyclohexene (C6 H10 ) attached to one of the carbon of ethylamine (C2 H7 N). Many of the spectroscopic properties of 2-(1-cyclohexenyl)ethylamine (CyHEA) have not been reported yet. However, Sirimanne and May reported dopamine ␤-monooxygenase (DBM) catalysed stereoselective allylic hydroxylation of CyHEA [1] and they demonstrated prototypical non-conjugated olefinic substrate CyHEA was not only a highly active substrate but also a mechanism-based inhibitor for DBM [2]. CyHEA also was used as a substrate and oxidizing agent for Ru complex [3]. Starting from CyHEA, 2-(1-cyclohexenyl)ethylcyanamide was synthesized and some of its IR and NMR properties was reported by G¨o␤nitzer et al. [4]. Density functional theory (DFT) calculations have provide excellent agreement with experimental vibrational frequencies of organic compounds, if the calculated frequencies are scaled to compensate for the aproximate treatment of electron correlation, basis set deficiencies and anharmonicity [5–11].

Moreover, gauge including atomic orbitals/density functional theory (GIAO/DFT) approach is widely used for the calculations of chemical shifts for a variety of heterocyclic compounds [12–16]. It has also been proved that DFT method is more successful in the calculations of vibrational frequencies and chemical shifts than the HF method [17–20]. NMR is a sensitive and versatile probe of molecular-scale structure and dynamics in solids and liquids. It has been widely used in chemistry, materials and geochemistry [21–24] and it enables to get faster and easier structural information. The standart 1D and 2D hetero and homonuclear NMR experiments are sufficient to afford complete assignment of organic compounds, and effective to afford molecular structure information [25–27]. In this study, we report FT-IR and 1 H, 13 C, DEPT, HETCOR, COSY, and NOESY NMR spectra of CyHEA for the first time. The vibrational frequencies and 1 H, 13 C NMR chemical shifts of CyHEA have also been calculated by using HF, BLYP and B3LYP methods with 6-31G(d) and 6-31G(d,p) basis sets, respectively.

2. Experimental ∗ Corresponding author at: Plant, Drug and Scientific Research Centre, Anadolu University, Eskis¸ehir, Turkey. Tel.: +90 222 335 2952; fax: +90 222 335 0127. E-mail address: [email protected] (C. Parlak).

1386-1425/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2006.10.050

The pure CyHEA molecule in the liquid form was obtained from Aldrich Chemical Co., USA and was used without further purification. The IR spectra of the liquid CyHEA was recorded

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in the range of 4000–400 cm−1 via Perkin-Elmer FT-IR 2000 spectrometer at a resolution of 4 cm−1 . NMR experiments were performed in a Bruker AVANCE 500 spectrometer using 5 mm BBO probe at 300 K. CyHEA was dissolved in CDCl3 . Chemical shifts were reported in ppm relative to TMS for 1 H and 13 C NMR spectra. 1 H NMR, 13 C NMR, DEPT, HETCOR, COSY and NOESY NMR spectra were obtained at a base frequency of 125.76 MHz for 13 C and 500.13 MHz for 1 H nuclei. For 13 C NMR spectroscopy, the pulse sequence used a delay (D1) and acquisition time (AQ) of 2.0 s and 1.62 s, respectively, a spectral width of 20,161 Hz, 64K data points, 90◦ pulse (8.30 ␮s) and 16 scans. DEPT spectra were obtained at θ z = 45◦ where CH, CH2 and CH3 appear in the positive phase, θ z = 90◦ where only CH appears in the positive phase and θ z = 135◦ where CH, CH3 appear in the positive phase and CH2 appears in the negative phase. For 1 H NMR experiment D1 = 1 s, AQ = 7.39 s, spectral width 4432 Hz, 64K data points, 90◦ pulse (14.15 ␮s) and 16 scans were performed. Two-dimensional HETCOR, COSY and NOESY techniques were measured using standart pulse programs provided by Bruker.

calculated using the gauge including atomic orbital (GIAO) method [34] in chloroform (ε = 4.9) at HF/6-31G(d,p), BLYP/631G(d,p) and B3LYP/6-31G(d,p) level under the keyword nmr = spin–spin. Relative chemical shifts were then estimated by using the corresponding TMS shielding calculated in advance at the same theoretical level as the reference. Calculated 1 H and 13 C isotropic chemical shieldings for TMS at HF/6-31G(d,p), BLYP/6-31G(d,p) and B3LYP/6-31G(d,p) levels in chloroform (ε = 4.9) by using the IEFPCM method were 32.32 ppm, 31.47 ppm, 31.74 ppm and 203.38 ppm, 186.64 ppm, 192.04 ppm, respectively. The experimental values for 1 H and 13 C isotropic chemical shifts for TMS were 30.84 ppm and 188.1 ppm, respectively [35]. Although the absolute shielding calculations were performed for all nuclei, it was focused on 1 H and 13 C chemical shifts since the experimental values referred to these nuclei. All the calculations were performed by using GaussView molecular visualization program and Gaussian 03 program package on a personal computer [36,37].

3. Calculations

4.1. FT-IR studies of CyHEA

For the vibrational calculations, molecular structure of CyHEA was optimized by HF, BLYP and B3LYP with 6-31G(d) basis set. By using the same methods and the basis set the vibrational frequencies of CyHEA were calculated, and then scaled by 0.8929 [9–10,28–31], 0.9940 [28,31] and 0.9613 [28–30], respectively. In the calculations all frequencies were positive. Therefore, we were confident that a definite absolute minimum in the potential energy surface was found. For the NMR calculations, molecular structure of CyHEA was first fully optimized at 6-31G(d,p) level in chloroform (ε = 4.9) by using the IEFPCM method [32,33]. After optimization, 1 H and 13 C NMR chemical shifts (δH and δC ) were

The vibrational assignments and frequencies of CyHEA have not been reported in the literature yet. The CyHEA molecule consists of 24 atoms, so it has 66 normal vibrational modes and it belongs to the point group C1 with only identity (E) symmetry element or operation. It is difficult to determine the CyHEA molecule’s vibrational assignments in the observed spectrum due to its low symmetry. The vibrational assignments and frequencies for the free CyHEA have been catalogued according to vibrational assignments and frequencies of cyclohexene [38] and ethylamine [39] since CyHEA contains both structural moieties. The similar process was reported for the vibrational assignments of the 4-(3-cyclohexen-1-yl)pyridine in our previous study [40].

4. Results and discussions

Fig. 1. Infrared spectrum of the liquid CyHEA molecule.

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Table 1 The measured IR frequencies (cm−1 ) for the CyHEA molecule together with the data for cyclohexene and ethylamine molecules Ass.a

Cyclohexenea

Ass.b

Ethylamineb

CyHEA

– – ν23 ν1 – ν24 ν2 ν3 ν25 ν26 ν4 ν27 ν5 ν6 – – – ν28 ν29 ν8 – ν9 ν10 ν30 ν31 – ν32 ν11 ν12 ν34 – – ν15 ν35 ν36 ν16 ν37 ν17 – ν38 ν18 ν19 ν39 ν40 ν20 ν41 –

– – 3067 3026 – 2960 2940 2916 2898 2882 2865 2860 2839 1656 – – – 1450 1443 1436 – 1353 1343 1338 1321 – 1265 1241 1222 1139 – – 1068 1040 1009 996 917 905 – 878 822 789 721 643 495 455 –

N–H a-str N–H s-str – – C–H str (CH3 ) – C–H str (CH3 ) – C–H str (CH2 ) – – C–H str (CH3 ) C–H str (CH2 ) – NH2 sciss CH2 sciss C–H bend (CH3 ) C–H bend (CH3 ) – – CH2 wag C–H bend (CH3 ) – – – NH2 twist – CH2 twist – – CH3 rock (C–C, C–N) a-str – – CH3 rock – – – (C–C, C–N) s-str – CH2 rock NH2 wag – – – – (C–C–N) bend

3412 3345 – – 2985

3366 s 3288 s 3097 w 3043 m 2995 m – 2926 vs – 2894 vw 2877 vw – 2857 vs 2836 vs 1666 m 1600 mb 1505 vw 1473 vw 1448 vw – 1438 s 1384 w 1370 vw 1344 m 1334 w – 1307 w 1269 m 1242 w 1215 w 1136 m – 1086 w 1066 w 1049 w 1022 w 966 w 919 m 906 vw – 857 w 829 m 800 m 720 sh 647 w 497 vw 448 w –

2924 – 2906 – – 2860 2840 – 1622 1487 1465 1455 – – 1397 1378 – – – 1293 – 1238 – – 1117 1086 – – 1016 – – – 892 – 816 773 – – – – 403

Ass., assignments; v, very; s, strong; m, medium; w, weak, sh, shoulder; b, broad; s, symmetric; a, asymmetric; str, strectching; sciss, scissoring; bend, bending; twist, twisting; wag, wagging; rock, rocking. a Taken from Ref. [39]. b Taken from Ref. [40].

The measured infrared frequencies for the free CyHEA together with the data for cyclohexene and ethylamine molecules are given in Table 1. It is obvious that the asymmetric and symmetric N–H stretching bands at 3366 cm−1 and 3288 cm−1 are attributed to ethylamine. The medium ν1 and weak ν23 bands at between 3000 and 3100 cm−1 result from cyclohexene while the medium C–H stretching band at 2995 cm−1 arises from ethy-

Fig. 2. The optimized molecular structure of CyHEA molecule at used methods.

lamine. The very strong bands attributed to ethylamine attached to cyclohexene appear at between 2830 and 2920 cm−1 . Most of bands below the 1300 cm−1 arise from cyclohexene. Other bands observed in the experimental spectrum of CyHEA are shown in Table 1. The infrared spectrum of the liquid CyHEA is demonstrated in Fig. 1. We have calculated the theoretical vibrational frequencies of the title compound. Then, we have determined its approximate mode descriptions with the DFT calculations. For these calculations, the optimized molecular structure of CyHEA is shown in Fig. 2. The theoretical vibrational frequencies and the assignments of CyHEA with the experimental data have been compared and the results have been given in Table 2. According to the calculations for the eight normal vibrational modes of the title molecule are below the 400 cm−1 . As it can be seen from Table 2, if the vibrational assignments are investigated one-by-one, the obtained assignments with related molecules are consistent with the determined DFT calculations. There is also a good agreement between the experimental and the theoretical vibrational frequencies in the region of 4000–400 cm−1 except for some HF results. The asymmetric and symmetric N–H stretching frequencies observed at 3366 cm−1 and 3288 cm−1 are theoretically predicted at 3394 cm−1 (B3LYP), 3374 cm−1 (BLYP), 3513 cm−1 (HF) and 3276 cm−1 (B3LYP), 3273 cm−1 (BLYP), 3421 cm−1 (HF), respectively. The biggest difference between the experimental and the calculated frequencies is 28 cm−1 for B3LYP, 37 cm−1 for BLYP and 147 cm−1 for HF. Note that calculated frequencies have been scaled by 0.8929, 0.9940 and 0.9613 for HF, BLYP and B3LYP, respectively. In general, our intensities are very high when compared with those in the higher frequency region. Among the calculated fundamentals, the best agreement between the experimental and the calculated intensities are in low frequency region. We have noted that the experimental results belong to liquid phase and the theoretical calculations belong to gaseous phase. In order to compare the experimental frequencies, the correlation graphic based on the calculations has been presented in Fig. 3. The correlation values are found to be 0.99990, 0.99964 and 0.99935 for B3LYP, BLYP and HF with the 6-31G(d) basis set, respectively. It can be seen that B3LYP calculation is better than BLYP and HF calculations.

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Table 2 Comparison of the observed and the calculated vibrational frequencies (cm−1 ) of the CyHEA molecule Mode

ν1 ν2 ν3 ν4 ν5 ν6 ν7 ν8 ν9 ν10 ν11 ν12 ν13 ν14 ν15 ν16 ν17 ν18 ν19 ν20 ν21 ν22 ν23 ν24 ν25 ν26 ν27 ν28 ν29 ν30 ν31 ν32 ν33 ν34 ν35 ν36 ν37 ν38 ν39 ν40 ν41 ν42 ν43 ν44

Approximate mode descriptionsa

N(9)–H2 a-str N(9)–H2 s-str C(4)–H str C(1;2)–H2 a-str C(1;3)–H2 a-str + C(2)–H2 s-str C(1;2;6)–H2 a-str C(7;8)–H2 a-str C(1;2)–H2 a-str + C(3;6)–H(14;17) str C(1;2;6)–H2 s-str C(1;2)–H2 a-str C(7;8)–H2 s-str C(6)–H2 s-str C(3;7)–H2 s-str C(7)–H2 s-str + C(3)–H(14) str C(7)–H2 s-str C(8)–H(22) s-str N(9)–H2 s-str + C(4)–H a-str + C(7)–H2 wag + ip C(3;6)–H(15–18) bend N(9)–H2 sciss C(8)–H2 sciss ip C(1;2)–H(10–13) bend + C(8)–H2 sciss ip C(1)–H(10) bend + C(2;3)–H2 sciss C(2;3;6)–H2 sciss + ip C(7)–H(20) bend C(2;3)–H2 sciss C(7;8)–H2 twist N(9)–H2 twist + C(7;8)–H2 wag + ip C(4)–H bend N(9)–H2 twist + C(1;2;7;8)–H2 wag + ip C(4)–H bend ip ring str + ip C(7)–H(19) bend N(9)–H2 twist + C(1;2;6)–H2 wag + ip C(3;4;8)–H(14;16;21) bend C(1;2)–H2 twist + C(3;6)–H2 wag + ip C(4)–H bend N(9)–H2 twist + C(7;8)–H2 wag N(9)–H2 twist + C(2;8)–H2 twist + C(7;8)–H2 rock + ip C(1;3;4)–H(11;15;16) bend C(7;8)–H2 twist + ip C(1;4)–H(10–16) bend ip ring str + N(9)–H2 twist ip C(4)–H bend + C(1;2;7;8)–H2 twist + N(9)–H2 twist N(9)–H2 twist + C(8)–H2 rock + C(1;2;3;6)–H2 twist ip ring str + C(1)–H2 wag N(9)–H2 twist + C(7)–H2 rock + C(1;2;3;6)–H2 twist N(9)–H2 twist + C(3;7;8)–H2 twist + ip C(1;2;6)–H(10;13;17) bend N(9)–H2 twist + ip C(7)–H(19) bend + C(1;2)–H2 twist + C(3)–H2 rock C(1;2)–H2 rock + C(3)–H2 wag + C(7)–C(8)–N(9) a-str ip ring str + N(9)–H2 wag ip ring str + N(9)–H2 twist + ip C(7;8)–H(19;21) bend ip ring str + N(9)–H(24) bend + C(7;8)–H2 twist ip ring str + N(9)–H(24) bend + C(7;8)–H2 rock

Exp. Ass.b

Exp. IR Freq.c

Calculated/6-31G(d) basis set HFd Freq.

BLYPe Freq.

B3LYPf Freq.

N–H a-str N–H s-str ν23 ν1 C–H str (CH3 ) – – – – – ν2 + C–H str (CH3 ) – ν25 + C–H str (CH2 ) ν26 ν27 + C–H str (CH3 ) ν5 + C–H str (CH3 ) ν6

3366 s 3288 s 3097 w 3043 m 2995 m – – – – – 2926 vs – 2894 vw 2877 vw 2857 vs 2836 vs 1666 m

3513 (26.18) 3421 (12.73) 3231 (3.92) 3137 (28.29) 3091 (18.61) 3072 (0.98) 3045 (1.12) 3020 (1.49) 3005 (2.23) 2995 (1.96) 2972 (38.08) 2931 (0.78) 2919 (2.19) 2901 (2.46) 2895 (103.83) 2881 (7.75) 1663 (8.80)

3374 (17.99) 3273 (12.22) 3080 (2.26) 3008 (32.23) 2993 (17.06) 2988 (3.19) 2982 (2.35) 2981 (0.19) 2964 (2.73) 2949 (2.37) 2934 (55.56) 2913 (1.32) 2901 (3.77) 2899 (1.37) 2848 (138.87) 2838 (6.22) 1662 (5.46)

3394 (19.80) 3276 (14.11) 3090 (2.61) 3044 (19.76) 2996 (15.29) 2990 (1.89) 2981 (1.61) 2975 (1.21) 2958 (2.52) 2940 (0.79) 2928 (46.12) 2910 (2.03) 2898 (2.43) 2881 (2.57) 2858 (120.7) 2840 (4.59) 1660 (6.66)

NH2 sciss – CH2 sciss

1600 mb – 1505 vw

1600 (5.44) 1577 (0.96) 1510 (1.18)

1633 (7.45) 1515 (0.56) 1505 (0.45)

1610 (7.25) 1557 (0.74) 1514 (1.16)

– C–H bend (CH3 ) – ν28 + C–H bend (CH3 ) ν8

– 1473 vw – 1448 vw 1438 s

1499 (2.24) 1473 (2.29) 1462 (0.55) 1451 (1.76) 1417 (11.30)

1494 (0.43) 1492 (3.35) 1485 (0.76) 1475 (2.65) 1401 (12.19)

1501 (1.45) 1479 (3.87) 1465 (1.41) 1447 (2.24) 1428 (12.74)

CH2 wag

1384 w

1401 (1.19)

1373 (1.86)

1387 (1.25)

ν9 + C–H bend (CH3 ) ν10

1370 vw 1344 m

1388 (0.14) 1337 (3.95)

1363 (0.48) 1346 (2.15)

1372 (0.74) 1351 (2.92)

ν30

1334 w

1330 (2.55)

1329 (1.36)

1340 (2.43)

– NH2 twist

– 1307 w

1326 (1.08) 1308 (1.81)

1316 (1.58) 1313 (1.54)

1320 (1.14) 1309 (1.28)

–

1300 (1.58)

1300 (0.96)

1295 (1.77)

ν32 ν11 + CH2 twist

1269 m 1242 w

1278 (2.60) 1262 (2.26)

1269 (2.93) 1254 (6.56)

1271 (3.77) 1228 (3.71)

ν12

1215 w

1218 (2.51)

1239 (2.64)

1211 (2.13)

–

– –

– –

1185 (2.16) 1161 (1.81)

1191 (1.43) 1176 (0.99)

1184 (1.85) 1165 (1.02)

–

–

1150 (2.74)

1147 (4.37)

1141 (4.89)

ν34

1136 m

1144 (3.74)

1133 (1.58)

1124 (1.06)

(C–C, C–N) a-str

1086 w

1074 (1.02)

1084 (2.18)

1079 (1.06)

ν15 ν35

1066 w 1049 w

1065 (2.78) 1047 (1.24)

1068 (1.85) 1057 (1.09)

1067 (1.60) 1051 (0.98)

1030 (1.80)

1034 (1.56)

1036 (0.44)

1014 (1.90)

1024 (1.41)

1022 (2.28)

– ν36 + CH3 rock

– 1022 w

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Table 2 (Continued) Mode

ν45 ν46 ν47 ν48 ν49 ν50 ν51 ν52 ν53 ν54 ν55 ν56 ν57 ν58

Approximate mode descriptionsa

N(9)–H2 twist + ip C(8)–H(21) bend + C(7)–H2 wag + ip ring str N(9)–H2 twist + C(7;8)–H bend + opp ring torsion N(9)–H2 twist + C(1;2;3;6)–H2 twist opp[N(9)–H(23) bend + ring torsion + C(4)–H bend] N(9)–H2 twist + C(7;8)–H2 rock + ip ring str opp[N(9)–H(23) + C(1)–H(10)] bend + C(7;8)–H2 twist + C(3)–H2 rock N(9)–H2 wag + C(7;8)–H2 rock + opp ring bend opp[N(9)–H(23) + ring] bend + C(7;8)–H2 rock N(9)–H2 wag + C(1;2;3)–H2 rock + C(6)–H2 twist N(9)–H2 wag + C(1;8)–H2 rock N(9)–H2 wag + C(7)–H2 wag + ip ring str + opp C(4)–H bend N(9)–H2 twist + C(7)–H2 wag + ip ring bend ip ring bend + C(7)–H2 twist C(7)–H2 twist + ip ring bend

Exp. Ass.b

Exp. IR Freq.c

Calculated/6-31G(d) basis set HFd Freq.

BLYPe Freq.

B3LYPf Freq.

ν16

966 w

964 (2.11)

964 (1.04)

973 (1.56)

ν37

919 m

917 (4.17)

953 (3.41)

937 (3.78)

ν17 –

906 vw –

902 (1.25) 875 (1.68)

942 (0.96) 882 (1.64)

925 (1.22) 895 (1.80)

ν38

857 w

866 (1.42)

836 (2.88)

862 (2.76)

ν18 + CH2 rock

829 m

833 (7.80)

830 (9.17)

822 (7.85)

ν19 + NH2 wag

800 m

803 (3.29)

781 (4.26)

808 (5.47)

–

–

749 (2.61)

766 (6.76)

769 (5.42)

–

–

741 (2.61)

759 (3.73)

742 (2.45)

720 sh 647 w

719 (1.77) 645 (2.92)

733 (1.72) 671 (7.08)

730 (0.57) 664 (8.23)

–

541 (1.07)

533 (3.86)

525 (2.33)

497 vw 448 w

487 (1.64) 440 (1.59)

499 (1.15) 436 (3.79)

515 (1.18) 450 (2.09)

ν39 ν40 – ν20 ν41

IR intensities (km/mol) are in parantheses. Ass., assignments; Exp., experimental; Freq., frequency; v, very; s, strong; m, medium; w, weak, sh, shoulder; b, broad; str, stretching; bend, bending; sciss, scissoring; twist, twisting; wag, wagging; s, symmetric; a, asymmetric; ip, in plane; opp, out of plane. a Our vibrational frequency assignment on the basis of the DFT calculations. b Our vibrational frequency assignment obtained with assignments of related molecules. c Our experimental IR frequencies. d Scaling factor = 0.8929 [6–7,29–32] for HF with 6-31G(d) basis set. e Scaling factor = 0.9940 [29,32] for BLYP with 6-31G(d) basis set. f Scaling factor = 0.9613 [29–31] for B3LYP with 6-31G(d) basis set.

4.2. NMR studies of CyHEA All the experimental values for 13 C NMR and 1 H measurements of CyHEA are given in Tables 3 and 4. As in Fig. 4,

CyHEA molecule shows eight different carbon atoms, which is consistent with the structure of the molecule. Owing to a lacking molecular symmetry, eight carbon peaks are observed in 13 C NMR spectrum of CyHEA. If the integration values of 1 H NMR spectrum are investigated in Fig. 5, it can be seen that total integration values are in compliance with the total number of protons in CyHEA. In DEPT spectra (Fig. 6) the peak which appears in 134.52 ppm in 13 C NMR spectrum cannot be observed. Therefore, it can be concluded that the peak belongs to the carbon C5 and does not contain any H bond. It is clear from 2D HETCOR NMR spectrum (Fig. 7) that there is no H atom bonded to C5 as expected. Thus, HETCOR spectrum is in agreement with the Table 3 Experimental and calculated molecule

Fig. 3. Plot of the calculated vs. the experimental frequencies of the CyHEA molecule.

13 C

NMR chemical shifts (ppm) of CyHEA

Carbon

Experimental

B3LYP

BLYP

HF

C2 C1 C3 C6 C7 C8 C4 C5

22.00 22.45 24.70 27.55 39.41 41.79 122.20 134.52

22.08 22.68 24.89 30.45 40.05 41.83 121.45 137.11

23.77 24.64 26.69 30.03 41.31 43.07 120.17 138.18

18.56 20.76 22.95 27.48 36.06 38.65 119.85 140.12

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Table 4 Experimental and calculated 1 H NMR chemical shifts (ppm) of CyHEA molecule Proton

Experimental

B3LYP

BLYP

HF

H23–24 H12–13 H10–11 H17–18 H14–15 H19–20 H21–22 H16

1.13 1.53 1.60 1.89 1.98 2.03 2.70 5.42

0.83 1.47 1.51 1.89 1.94 2.10 2.90 5.74

0.71 1.49 1.54 1.95 2.02 2.13 3.00 5.73

0.42 1.39 1.43 1.59 1.61 1.83 2.51 5.54

Fig. 6. DEPT spectra of CyHEA molecule.

Fig. 4.

13 C

NMR spectrum of CyHEA molecule.

DEPT spectra. The peak which appears at 1.13 ppm belongs to the (–NH2 ) amine group therefore, it does not have any interaction in the HETCOR spectrum. The correlations between C2 –H12,13 , C1 –H10,11 , C3 –H14,15 , C6 –H17,18 , C7 –H19,20 , C8 –H21,22 , C6 –H17,18 , C4 –H16 are also clearly observed in HETCOR spectrum. From the 2D COSY NMR spectrum (Fig. 8), it is clear that there is a correlation between H12,13 and H10,11 , H14,15 atoms those appear at 1.53 ppm, 1.60 ppm and 1.98 ppm, respectively. Moreover, correlations between H14,15 –H16 and H19,20 –H21,22 atoms are clearly observed in the COSY NMR

Fig. 5. 1 H NMR spectrum of CyHEA molecule.

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Fig. 7. 2D HETCOR NMR spectrum of CyHEA molecule. Fig. 9. 2D NOESY NMR spectrum of CyHEA molecule.

spectrum. From 2D NOESY NMR spectrum (Fig. 9), it can be said that there is an interaction between H16 –H19,20 , H16 –H21,22 , H16 –H23,24 and H17,18 –H19,20 through space. We have calculated the theoretical 13 C NMR and 1 H NMR chemical shifts of the title compound. Then, we have compared the theoretical and the experimental chemical shifts of CyHEA

Fig. 8. 2D COSY NMR spectrum of CyHEA molecule.

and the results are shown in Tables 3 and 4. According to these results, the calculated chemical shifts are in compliance with the experimental findings. The correlation graphic is also presented in Figs. 10 and 11 based on the calculations. The correlation values for proton and carbon chemical shifts are found to be 0.996, 0.989, 0.988 and 0.999, 0.998, 0.997 for B3LYP, BLYP and HF with the 6-31G(d,p) basis set, respectively. It can be seen that the B3LYP calculation is better than HF and BLYP calculations.

Fig. 10. Plot of the calculated vs. the experimental 13 C NMR chemical shifts of CyHEA molecule.

62

˙ et al. / Spectrochimica Acta Part A 68 (2007) 55–62 T. Izgi

Fig. 11. Plot of the calculated vs. the experimental 1 H NMR chemical shifts of CyHEA molecule.

5. Conclusion The experimental and the theoretical investigation of CyHEA molecule have been performed successfully by using FT-IR, NMR and quantum chemical calculations. For all calculations, it is shown that the results of DFT (B3LYP) method are excellent agreement with all the experimental findings. Acknowledgement This study was supported by Anadolu University Scientific Research Commission. References [1] S.R. Sirimanne, S.W. May, J. Am. Chem. Soc. 110 (1988) 7560. [2] S.R. Sirimanne, S.W. May, Biochem. J. 306 (1995) 77. [3] K. Mori, K. Yamaguchi, T. Mizugaki, K. Ebitani, K. Kaneda, Chem. Commun. (2001) 461. [4] E. G¨o␤nitzer, R. Malli, S. Schuster, B. Favre, N.S. Ryder, Arch. Pharm. Pharm. Med. Chem. 11 (2002) 535. [5] N.C. Handy, P.E. Maslen, R.D. Amos, J.S. Andrews, C.W. Murray, G.J. Laming, Chem. Phys. Lett. 197 (1992) 506. [6] N.C. Handy, C.W. Murray, R.D. Amos, J. Phys. Chem. 97 (1993) 4392. [7] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frisch, J. Phys. Chem. 98 (1994) 11623. [8] F.J. Devlin, J.W. Finley, P.J. Stephens, M.J. Frisch, J. Phys. Chem. 99 (1995) 16883. [9] S.Y. Lee, B.H. Boo, Bull. Korean Chem. Soc. 17 (1996) 754.

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