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. 2006 Nov 28;2006:79327. doi: 10.1155/BCA/2006/79327

Proposal for Sets of 77Se NMR Chemical Shifts in Planar and Perpendicular Orientations of Aryl Group and the Applications

Satoko Hayashi 1, Waro Nakanishi 1,*
PMCID: PMC1800916  PMID: 17497018

Abstract

The orientational effect of p-YC6H4 (Ar) on δ(Se) is elucidated for ArSeR, based on experimental and theoretical investigations. Sets of δ(Se) are proposed for pl and pd employing 9-(arylselanyl)anthracenes (1) and 1-(arylselanyl)anthraquinones (2), respectively, where Se–C R in ArSeR is on the Ar plane in pl and perpendicular to the plane in pd. Absolute magnetic shielding tensors of Se (σ(Se)) are calculated for ArSeR (R = H, Me, and Ph), assuming pl and pd, with the DFT-GIAO method. Observed characters are well reproduced by the total shielding tensors (σ t(Se)). The paramagnetic terms (σ P(Se)) are governed by σ P(Se)xx + σ P(Se)yy, where the direction of nP(Se) is set to the z-axis. The mechanisms of the orientational effect are established both for pl and pd. Sets of δ(Se: 1) and δ(Se: 2) act as the standards for pl and pd, respectively, when δ(Se) of ArSeR are analyzed based on the orientational effect.

INTRODUCTION

77 Se NMR spectroscopy is one of powerful tools to study selenium compounds [1–20], containing bioactive materials [21–24]. 77 Se NMR chemical shifts (δ(Se)) are sharply sensitive to the structural changes in selenium compounds. Therefore, they are widely applied to determine the structures [6–20] and to follow up the reactions of selenium compounds [1–10]. The δ(Se) values have been analyzed variously. The substituent effect is employed when the effect of the electronic conditions around Se on δ(Se) is examined in p-YC6H4SeR perturbed by Y, for example [6–20]. Some empirical rules and/or classifications between structures and δ(Se) are proposed [6–20], however, it is not so easy to predict δ(Se) from the structures with substantial accuracy. Some important rules would be behind the observed values. Plain rules, founded on the theoretical background, are necessary to analyze the structures of selenium compounds based on δ(Se) and also to understand the origin of δ(Se) [25].

We have pointed out the importance of the orientational effect on δ(Se) of p-YC6H4SeR, for the better understanding of δ(Se) of ArSeR in a uniform manner [19, 20, 25]. To establish the orientational effect, we present two series of δ(Se) for p-YC6H4SeR whose structures (conformers) are fixed to planar (pl) and perpendicular (pd) conformers for all Y examined, under the conditions [26, 27]. (The nonplanar and nonperpendicular conformer (np) is also important in some cases, such as the CC conformer in 1,8-(MeZ)2C10H6 (Z = S and Se) [28–33].) (The importance of relative conformations in the substituent effects between substituents and probe sites is pointed out.) The Se−CR bond in ArSeR is on the Ar plane in pl and perpendicular to the plane in pd. 9-(Arylselanyl)anthracenes (p-YC6H4SeAtc: 1) and 1-(arylselanyl)anthraquinones (p-YC6H4SeAtq: 2) are the candidates for pl and pd, respectively: Y in 1 and 2 are H (a), NMe2 (b), OMe (c), Me (d), F (e), Cl (f), Br (g), COOEt (h), CN (i), and NO2 (j) (see Chart 1). Conformers of the 9-anthracenyl (9-Atc) and 1-anthraquinonyl (1-Atq) groups in 1 and 2 are represented by the type A (A), type B (B), and type C (C) notation, which is proposed for 1-(arylselanyl)naphthalenes (p-YC6H4SeNap: 3) [14–16, 19, 20, 26]. The structure of 1 is A for 9-Atc and pl for Ar, which is denoted by 1 (A: pl). That of 2 is B for the 1-Atq and pd for Ar (2 (B: pd)). The series of δ(Se) in 1 (δ(Se: 1)) and δ(Se: 2) must be typical for pl and pd, respectively.

Chart 1.

Chart 1

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Recently, the reliability of the calculated absolute magnetic shielding tensors (σ) is much improved [34–39] and the calculated tensors for Se nuclei (σ(Se)) are demonstrated to be useful in usual selenium compounds [28–33]. 1 As shown in (1), the total absolute magnetic shielding tensor (σt) is decomposed into diamagnetic (σd) and paramagnetic (σp) contributions [40, 41]. 2 σp contributes predominantly to σt in the structural change of selenium compounds. Magnetic shielding tensors consist of three components, as exemplified by σp in (2) as the following:

σt = σd + σp, (1)
σp = (σpxx + σpyy + σpzz)/3. (2)

Quantum chemical (QC) calculations are performed on ArSeH (4), ArSeMe (5), and ArSePh (6) to understand the orientational effect based on the theoretical background (see Chart 1). The conformations are fixed to pl and pd in the calculations. The gauge-independent atomic orbital (GIAO) method [42–46] is applied to evaluate σ(Se) at the DFT (B3LYP) level. Mechanisms of the orientational effect are explored for pl and pd based on the magnetic perturbation theory on the molecules.

After the establishment of the orientational effect of aryl group in p-YC6H4SeR, together with the mechanism, δ(Se) of some aryl selenides are plotted versus δ(Se: 1) and/or δ(Se: 2). The treatment shows how δ(Se) of aryl selenides are interpreted based on the orientational effect. And it is demonstrated that the sets of δ(Se: 1) and δ(Se: 2) give a reliable guideline to analyze the structures of p-YC6H4SeR based on δ(Se).

RESULTS

The structures of all members of 1 and 2 are predicted to be 1 (A: pl) and 2 (B: pd), respectively [25]. The results are supported by the X-ray crystallographic analysis carried out for 1 and 2, containing 1c and 2a and the QC calculations for 1a and 2a, together with the spectroscopic measurements, although not shown. Scheme 1 illustrates 1 (A: pl) and 2 (B: pd), together with some conformers of 3.

Scheme 1.

Scheme 1

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Structures of 1 and 2, together with those of 3.

Table 1 shows δ(Se: 1) and δ(Se: 2), measured in chloroform-d solutions (0.050 M) at 213 K, 297 K, and 333 K. 3 δ(Se: 1a) and δ(Se: 2a) are given from MeSeMe and δ(Se: 1) and δ(Se: 2) are from 1a and 2a, respectively, (δ(Se)SCS). To examine the temperature dependence in 1, δ(Se: 1)SCS at 297 K (δ(Se: 1)SCS, 297 K) and δ(Se: 1)SCS, 333 K are plotted versus δ(Se: 1)SCS, 213 K. Table 2 collects the correlations, where the correlation constants (a and b) and the correlation coefficients (r) are defined in the footnote of Table 2 (entries 1 and 2). δ(Se: 2)SCS, 297 K and δ(Se: 2)SCS, 333 K are similarly plotted versus δ(Se: 2)SCS, 213 K. Table 2 also contains the correlations (entries 3 and 4). The a values for 1 are smaller than those for 2. The results show that the temperature dependence in 1 is larger than that of 2, although both correlations are excellent (r > 0.999). The results show that 2 (B: pd) are thermally very stable and other conformers are substantially negligible in the solution for all Y examined. 1 (A: pl) must also be predominant in solutions, although 1 (A: pl) would not be thermally so stable, relative to the case of 2 (B: pd).

Table 1.

Observed δ(Se)SCS of 1 and 2 and calculated σt rel(Se)SCS for 4–6 in pl and pd (a,b).

Compd T NMe2 OMe Me H F Cl Br CO2R (c) CN NO2
[K] (b) (c) (d) (a) (e) (f) (g) (h) (i) (j)
1 213 −22.7 −12.7 −6.3 0.0 (245.3) −3.3 1.9 2.4 17.4 27.7 32.7
1 297 −21.0 −12.2 −6.6 0.0 (249.0) −3.6 1.5 1.6 16.2 26.2 30.4
1 333 −21.3 −12.7 −6.8 0.0 (250.6) −3.9 1.0 1.2 15.2 24.8 29.0
2 213 −20.6 −15.5 −9.2 0.0 (511.4) −10.5 −7.1 −6.4 0.1 8.5 2.7
2 297 −19.6 −15.0 −9.0 0.0 (512.3) −10.2 −7.1 −6.4 0.0 8.2 2.5
2 333 −19.5 −15.0 −9.1 0.0 (512.5) −10.3 −7.2 −6.7 −0.3 7.9 2.2
4 (pl) — −36.4 −18.0 −8.2 0.0 (87.0) −1.6 1.7 −1.8 14.3 29.8 33.7
4 (pd) — −35.9 −23.0 −15.6 0.0 (41.3) −11.8 −9.1 −8.7 1.0 16.8 10.0
5 (pl) — −23.9 −8.2 −8.0 0.0 (169.7) 2.1 4.7 7.2 24.6 29.7 43.8
5 (pd) — −34.9 −21.2 −16.7 0.0 (219.1) −14.1 −11.8 −12.6 3.0 13.4 6.6
6 (pl) — −20.5 −9.0 −3.7 0.0 (398.8) 1.1 1.9 2.3 13.1 20.2 28.6
6 (pd) — −34.2 −25.8 −14.6 0.0 (398.8) −15.2 −13.3 −12.6 −3.4 7.0 0.5
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(a) δ(Se)SCS are given for 1 and 2, together with δ(Se) for 1 a and 2 a in parenthesis, measured in chloroform-d.

(b) σt rel(Se)SCS are given for 4−6, together with σt rel(Se) for 4a−6a in parenthesis, calculated according to (3), where σt(Se) of 4−6 in pl and pd are given in Tables 3–5, respectively, and σt(Se: MeSeMe) = 1650.4 ppm.

(c) R = Et for 1 and 2 and R = Me for 4−6.

Table 2.

Correlations of δ(Se)SCS for 1 and 2 and σ(Se) for 4−6, together with δ(Se)SCS for 5−9 (a) .

Entry Correlation a b r n (b)
1 δ(Se: 1)SCS, 297 K vs δ(Se: 1)SCS, 213 K 0.940 −0.3 1.000 10
2 δ(Se: 1)SCS, 333 K vs δ(Se: 1)SCS, 213 K 0.916 −0.8 1.000 10
3 δ(Se: 2)SCS, 297 K vs δ(Se: 2)SCS, 213 K 0.957 −0.1 1.000 10
4 δ(Se: 2)SCS, 333 K vs δ(Se: 2)SCS, 213 K 0.946 −0.3 1.000 10
5 δ(Se: 1)SCS, 213 K vs σ rel(Se: 4 (pl))SCS 0.823 2.6 0.986 10
6 δ(Se: 1)SCS, 213 K vs σ rel(Se: 5 (pl))SCS 0.845 −2.1 0.990 10
7 δ(Se: 1)SCS, 213 K vs σ rel(Se: 6 (pl))SCS 1.218 −0.4 0.991 10
8 δ(Se: 2)SCS, 213 K vs σ rel(Se: 4 (pd))SCS 0.562 −1.5 0.990 10
9 δ(Se: 2)SCS, 213 K vs σ rel(Se: 5 (pd))SCS 0.599 −0.5 0.988 10
10 δ(Se: 2)SCS, 213 K vs σ rel(Se: 6 (pd))SCS 0.691 1.9 0.990 10
11 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 4 (pl) 0.339 −547.8 0.982 10
12 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 5 (pl) 0.367 −461.8 0.999 10
13 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 6 (pl) 0.350 −546.7 0.990 10
14 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 4 (pd) 0.309 −547.0 0.998 10
15 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 5 (pd) 0.345 −517.4 0.994 10
16 σp(Se) vs (σp(Se)xx + σp(Se)yy) in 6 (pd) 0.335 −598.5 0.998 10
17 δ(Se: 5)SCS (c) vs δ(Se: 1)SCS, 213 K 0.997 1.0 0.997 8
18 δ(Se: 5)SCS (d) vs δ(Se: 1)SCS, 213 K 0.952 0.1 0.999 7
19 δ(Se: 7)SCS vs δ(Se: 2)SCS, 213 K 0.909 1.3 0.995 10
20 δ(Se: 6)SCS vs δ(Se: 1)SCS, 213 K 0.804 −3.3 0.991 7
21 δ(Se: 8)SCS vs δ(Se: 1)SCS, 213 K 0.691 −1.7 0.981 9
22 δ(Se: 9)c SCS vs δ(Se: 1)SCS, 213 K 0.870 −1.3 0.999 7
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(a)The constants (a, b, r) are defined by y = ax + b (r: correlation coefficient).

(b)The number of data used in the correlation. (c)Reference [19] at neat. (d)Reference [11] in CDCl3.

Scheme 2 shows the axes and some orbitals of 4–6, together with SeH2. While the x-axis of SeH2 is in the bisected direction of ∠HSeH, the Se−H and Se−C bonds of MeSeH are almost on the x- and y-axes, respectively, although not shown. Axes of 4–6 are close to those in MeSeH in most cases. Since ∠CSeX (X = H or C) in 4–6 are about 95°, 98°, and 101°, respectively, the Se−C and Se−H bonds deviate inevitably from the axes to some extent. Axes are rather similar to those of SeH2 for 4 (pl) with Y = Br and COOMe and 5 (pl) with Y = Me and CN. 4

Scheme 2.

Scheme 2

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Axes and some orbitals of 4–6, together with those of SeH2.

Structures of 4–6 in pl and pd are optimized employing the 6-311+G(3df) basis sets for Se and the 6-311+G(3d,2p) basis sets for other nuclei of the Gaussian 03 program [47]. 5 Calculations are performed at the density functional theory (DFT) level of the Becke three parameter hybrid functionals with the Lee-Yang-Parr correlation functional (B3LYP). Absolute magnetic shielding tensors of Se (σ(Se)) are calculated based on the DFT-GIAO method [42–46], applying on the optimized structures with the method. Tables 3–5 collect σt(Se), σd(Se), σp(Se), and the components of σp(Se), σp(Se)xx, σp(Se)yy, and σp(Se)zz for 4–6 bearing various substituents Y in pl and pd, respectively. 6

Table 3.

Calculated absolute shielding tensors (σ(Se)) of 4, containing various Y (a) .

Y σd(Se) σp(Se)xx σp(Se)yy σp(Se)zz σp(Se) σt(Se)
4 (pl)
H 2999.5 −1571.7 −1042.3 −1694.2 −1436.1 1563.4
NMe2 3006.4 −1676.1 −862.4 −1681.4 −1406.7 1599.8
OMe 3004.7 −1823.5 −757.0 −1689.5 −1423.3 1581.4
Me 3002.4 −1760.2 −848.1 −1684.2 −1430.8 1571.6
F 3001.4 −1800.4 −833.2 −1675.7 −1436.4 1565.0
Cl 3003.8 −1777.8 −868.7 −1680.0 −1442.2 1561.7
Br 3008.7 −1883.4 −745.3 −1701.6 −1443.4 1565.2
COOMe 3010.0 −1469.6 −1197.4 −1715.7 −1460.9 1549.1
CN 3002.1 −1829.1 −889.8 −1686.5 −1468.5 1533.6
NO 2 3004.9 −1836.6 −905.8 −1683.2 −1475.2 1529.7
4 (pd)
H 3001.9 −1870.9 −869.9 −1437.6 −1392.8 1609.1
NMe2 3004.1 −1782.2 −842.4 −1452.8 −1359.1 1645.0
OMe 3005.4 −1805.2 −871.3 −1443.6 −1373.4 1632.1
Me 3002.2 −1821.7 −871.0 −1439.8 −1377.5 1624.7
F 3000.8 −1829.8 −866.2 −1443.7 −1379.9 1620.9
Cl 3000.8 −1834.5 −870.2 −1442.8 −1382.5 1618.2
Br 3000.5 −1835.5 −870.5 −1442.1 −1382.7 1617.8
COOMe 3004.2 −1872.6 −879.2 −1436.5 −1396.1 1608.1
CN 2999.9 −1901.0 −881.6 −1440.1 −1407.6 1592.3
NO 2 3000.7 −1877.7 −884.4 −1442.8 −1401.6 1599.1
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(a) Structures are optimized with the 6-311+G(3df) basis sets for Se and 6-311+G(3d,2p) basis sets for other nuclei at the DFT (B3LYP) level, assuming pl and pd for each of Y [47]. σ(Se) are calculated based on the DFT-GIAO method with the same methods.

Table 5.

Calculated absolute shielding tensors (σ(Se)) of 6, containing various Y (a) .

Y σd(Se) σp(Se)xx σp(Se)yy σp(Se)zz σp(Se) σt(Se)
6 (pl)
H 2995.1 −1527.4 −1887.5 −1815.6 −1743.5 1251.6
NMe2 2997.7 −1462.8 −1902.3 −1811.6 −1725.5 1272.1
OMe 2995.5 −1504.1 −1887.4 −1813.2 −1734.9 1260.6
Me 2995.6 −1517.7 −1888.8 −1814.2 −1740.3 1255.3
F 2994.5 −1544.4 −1879.4 −1808.1 −1743.9 1250.5
Cl 2994.1 −1550.2 −1873.8 −1809.2 −1744.4 1249.7
Br 2996.5 −1553.1 −1871.1 −1817.4 −1747.2 1249.3
COOMe 2997.2 −1574.5 −1871.7 −1830.0 −1758.7 1238.5
CN 2994.8 −1605.6 −1869.2 −1815.6 −1763.5 1231.4
NO2 2994.4 −1630.8 −1867.8 −1815.7 −1771.4 1223.0
6 (pd)
H 2995.1 −1887.5 −1527.4 −1815.6 −1743.5 1251.6
NMe2 2998.3 −1787.3 −1531.6 −1818.6 −1712.5 1285.8
OMe 3002.2 −2044.1 −1313.9 −1816.4 −1724.8 1277.4
Me 2996.4 −1843.1 −1532.7 −1814.8 −1730.2 1266.2
F 2994.8 −1851.2 −1517.7 −1815.0 −1728.0 1266.8
Cl 2995.1 −1859.5 −1519.1 −1812.1 −1730.2 1264.9
Br 2997.2 −1871.4 −1514.8 −1812.8 −1733.0 1264.2
COOMe 3003.2 −2085.4 −1341.9 −1817.2 −1748.2 1255.1
CN 2998.5 −2132.1 −1310.6 −1818.8 −1753.8 1244.6
NO2 2995.5 −1914.6 −1502.6 −1816.1 −1744.4 1251.1
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(a)Structures are optimized with the 6-311+G(3df) basis sets for Se and 6-311+G(3d,2p) basis sets for other nuclei at the DFT (B3LYP) level, assuming pl and pd for each of Y [47]. σ(Se) are calculated based on the DFT-GIAO method with the same methods.

Relative shielding constants of A (σt rel(Se: A)) are calculated for 4–6 according to (3), using σt(Se: MeSeMe) (= 1650.4 ppm). σt rel(Se: A)SCS are calculated similarly. Table 1 also contains σt rel(Se: A) of 4a–6a and σt rel(Se: A)SCS for 4–6,

σtrel(Se : A) = −{σt(Se : A) − σt(Se : MeSeMe)} (A : n(pl), n(pd)). (3)

Table 6 shows σ(Se)SCS of p-YC6H4SeCOPh (7) [13], p-YC6H4SeCN (8) [8], and bis[8-(arylselanyl)naphthyl] 1,1′-diselenides (9) [15, 16], together with 5 [11, 19] and 6 [15, 16] (see Chart 2). The values are plotted versus δ(Se: 1)SCS and/or δ(Se: 2)SCS to explain the δ(Se) based on the orientational effect of the aryl groups.

Table 6.

Observed δ(Se)SCS reported for 5−9.

Compd NMe2 OMe Me H F Cl Br CO2R (a) CN NO2
(b) (c) (d) (a) (e) (f) (g) (h) (i) (j)
5 (b) −20.8 −10.4 −7.2 0.0 (207.8) — 2.5 2.8 20.1 — 33.4
5 (c) — −12.5 −5.9 0.0 (202.0) −2.0 1.6 — 16.1 — 31.4
6 (b) — −15.5 −8.6 0.0 (423.6) — −1.7 −1.3 9.7 — 22.7
7 (d) −18.6 −12.6 −7.1 0.0 (641.5) −7.1 −4.5 −4.1 0.8 8.9 4.2
8 (e) — −12.0 −7.8 0.0 (320.8) −2.5 0.2 0.9 8.6 21.0 18.0
9 (f) — −9.8 −6.6 0.0 (434.3) — −2.7 −1.9 8.1 — 19.6
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(a) R = Me for 5 and R = Et for 6−9. (b)Reference [19]. (c)Reference [11] at neat. (d)Reference [13]. (e)Reference [8]. (f)Reference [15, 16].

Chart 2.

Chart 2

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DISCUSSION

Characters in δ(Se: 1) and δ(Se: 2)

The structures of all members of 1 and 2 are confirmed to be 1 (A: pl) and (B: pd), respectively, (see Scheme 1) [25]. The nature of δ(Se: 1) must be the results of 1 (A: pl), where np(Se) is parallel to the π(C6H4Y-p). Characteristic points in δ(Se: 1)SCS are summarized as follows.

  1. Large upfield shifts (−23 ppm to −6 ppm) are observed for Y = NMe2, OMe, and Me and large downfield shifts (17 ppm to 33 ppm) are for Y = COOEt, CN, and NO2, relative to Y = H.

  2. Moderate upfield shift (−3 ppm) is observed for Y = F.

  3. Small downfield shifts (2 ppm) are for Y = Cl and Br: the three points corresponding to Y = H, Cl, and Br are found very close with each other.

The characters of δ(Se: 2)SCS are very different from those of δ(Se: 1)SCS. The characteristics must be the reflection of 2 (B: pd), where np(Se) is perpendicular to π(C6H4Y-p). Characteristic points of δ(Se: 2)SCS are as follows.

  1. Large upfield shifts (−21 to −6 ppm) are observed for Y = NMe2, OMe, Me, F, Cl, and Br, relative to Y = H.

  2. Downfield shifts (3 ppm to 9 ppm) are brought by Y = CN and NO 2, where the magnitude by Y = CN is larger than that by NO 2.

  3. δ(Se: 2)SCS brought by Y = COOEt is negligible.

While δ(Se: 1)SCS is in a range of −23 < δ(Se)SCS < 33 ppm, δ(Se: 2)SCS is −21 < δ(Se)SCS < 9 ppm. Y of both donors and acceptors operate well on δ(Se: 1)SCS , whereas only Y of donors do well on δ(Se: 2)SCS.

δ(Se: 2)SCS are plotted versus those of δ(Se: 1)SCS. Figure 1 shows the results. Indeed, it emphasizes the difference in the characters between δ(Se: 1)SCS and δ(Se: 2)SCS, but most of δ(Se: 2)SCS seem to correlate well with δ(Se: 1)SCS, as shown by a dotted line (a = 0.58). Two points corresponding to Y = H and NO2 deviate upside and downside from the line, respectively. Namely, points for 2 with Y of non-H are more downside (upfield) than expected from δ(Se: 1a)SCS and δ(Se: 2a)SCS, especially for δ(Se: 2j)SCS.

Figure 1.

Figure 1

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Plot of δ(Se: 2)SCS, 213 k versus δ(Se: 1)SCS, 213 k.

Why are such peculiar behaviors observed in 1 and 2, caused by the orientational effect of the aryl group? The mechanism is elucidated based on the QC calculations performed on 4–6, assuming pl and pd for each.

Observed δ(Se) versus calculated σt(Se)

The δ(Se)SCS values of 1 and 2 are plotted versus σt rel(Se)SCS of 4 (pl)–6 (pl) and 4 (pd)–6 (pd), respectively, (Table 1). Good correlations are obtained as shown in Table 2 (entries 5–10). The r values become larger in an order of 4(pl) < 5(pl) ≦ 6(pl) for 1 and in an order of 5(pd) < 4(pd) ≈ 6(pd) for 2. Namely, observed δ(Se: 1)SCS and δ(Se: 2)SCS are reproduced by σt rel(Se: 6 (pl))SCS and σt rel(Se: 6 (pd))SCS, respectively, in most successfully. Figure 2 exhibits the plots for (a) 1 versus 6 (pl) and (b) 2 versus 6 (pd). The correlations are given in Table 2 (entries 7 and 10). The results demonstrate that the characters of δ(Se)SCS observed in 1 originate from the planar structure and those in 2 from the characteristic structure, where Se−CAtq in p-YC6H4SeAtq is perpendicular to the p-YC6H4 plane.

Figure 2.

Figure 2

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Plots of (a) δ(Se: 1)SCS, 213 K versus σt rel(Se: 6 (pl))SCS and (b) δ(Se: 2)SCS, 213 K versus σt rel(Se: 6 (pd))SCS.

How does such orientational effect arise from the structures? How does the electronic property of Y affect on δ(Se) of 1 and 2? σp(Se) of 4–6 are analyzed next.

Orientational effect in 4a–6a

σ(Se) of 4–6 shown in Tables 3–5 are examined. σp(Se) and σt(Se) of 4a (pd) are evaluated to be larger (more upfield) than those of 4a (pl) by 43 ppm and 46 ppm, respectively, which correspond to the orientational effect caused by Ph in 4a. 7 The inverse orientational effect is predicted for 5a. σp(Se) and σt(Se) of 5a (pd) are smaller than those of 5a (pl) by 41 ppm and 49 ppm, respectively. While σp(Se) and σt(Se) of 5a (pl) are smaller than those of 4a (pl) by 90 ppm and 83 ppm, respectively, the values of 5a (pd) are smaller than those of 4a (pd) by 174 ppm and 178 ppm, respectively. The differences are −84 ppm and −95 ppm, respectively, which also correspond to the differences in the orientational effect of the Ph group between 5a and 4a, respectively. The more effective contribution to downfield shifts by the Se−CMe bond in 5a (pd), relative to 5a (pl), must be responsible for the results. The orientational effect cannot be discussed for 6a of the Cs symmetry with Y = H.

What mechanism is operating in the Y dependence? σp(Se) of 4–6 in pl and pd are analyzed next.

Y dependence in 4–6

To get an image in the behavior of σp(Se)xx, σp(Se)yy, and σp(Se)zz of 4–6, the values are plotted versus σp(Se). Figure 3 shows the plots for 4 (pd) and 6 (pl). The correlations in 4 (pd) are linear and both σp(Se)xx and σp(Se)yy increase along with σp(Se). The plot for 5 (pd) is similar to that for 4 (pd), although not shown. In the case of 6 (pl), the correlations are linear but the slope for σp(Se)yy is inverse to that for σp(Se)xx. The plots of σp(Se)xx and σp(Se)yy do not give smooth lines for 4 (pl), 5 (pl), and 6 (pd). However, the slopes for σp(Se)zz are very smooth and the magnitudes are very close to 1.0 for all cases in 4–6.

Figure 3.

Figure 3

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Plots of σp(Se)xx (●), σp(Se)yy (■), and σp(Se)zz (Δ) versus σp(Se): (a) for 4 (pd) and (b) for 6 (pl).

To clarify the behavior of σp(Se) in 4–6, σp(Se) are plotted versus (σp(Se)xx + σp(Se)yy). 8 Excellent to good correlations are obtained in all cases as collected in Table 2 (entries 11–16). Figure 4 exhibits the plot of σp(Se) for 6 (pd), for example. The correlation constants (a) are 0.31–0.37, which are very close to one third. The results exhibit that (σp(Se)xx+σp(Se)yy) determines σp(Se) of 4–6 effectively (cf: (2)). The observations led us to establish the mechanism of Y dependence in 4–6.

Figure 4.

Figure 4

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Plot of σp(Se) versus σp(Se)xx + σp(Se)yy for 6 (pd).

Mechanism of Y dependence

The mechanism of Y dependence in 4–6 is elucidated by exemplifying 4. As shown in Scheme 2, the main interaction between Se and Y in 4 (pl) is the 4pz(Se)-π(C6H4)-pz(Y) type, which modifies the contributions of 4pz(Se) in π(SeC6H4Y) and π*(SeC6H4Y). Since (σp(Se)xx + σp(Se)yy) controls σp(Se) of 4 (pl) effectively, admixtures between 4pz(Se) in modified π(SeC6H4Y) and π*(SeC6H4Y) with 4py(Se) and 4px(Se) in σ(CArSeH) and σ*(CArSeH) must originate the Y dependence mainly when a magnetic field is applied. 9 Since σp zz,N contains the ^Lz,N operator, σp zz,N arises from admixtures between atomic px and py orbitals of N in various molecular orbitals. When a magnetic field is applied on a selenium compound, mixings of unoccupied molecular orbitals (MO's; ψ i) into occupied orbital MO's (ψ i) will occur. Such admixtures generate σp zz,N if ψ i and ψ j contain px and py of N, for example. σp xx,N and σp yy,N are also understood similarly. Consequently, Y of both donors and acceptors are effective for the Y dependence in 4 (pl). Scheme 3(a) shows the mechanism for pl.

Scheme 3.

Scheme 3

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Mechanisms of Y dependence. Outline allows exhibit the effect of p(Y) on 4p(Se) and double allows show the main admixtures to originate δ(Se): (a) in pl and (b) in pd.

In the case of 4 (pd), 4pz(Se) remains in np(Se) in the almost pure form. 10 The σ(CArSeH)-π(C6H4)-px(Y) interaction occurs instead, which modifies the contributions of 4px(Se) and 4py(Se) in σ(CArSeH) and σ*(CArSeH) (see Scheme 2). (σp(Se)xx + σp(Se)yy) determines effectively σp(Se) of 4 (pd). Therefore, Y dependence of 4 (pd) originates mainly from admixtures between 4pz(Se) in np(Se) and 4px(Se) and 4py(Se) in modified σ*(CArSeH) since np(Se) of 4pz(Se) is filled with electrons. Consequently, Y dependence in 4 (pd) must be more sensitive to Y of donors, which is a striking contrast to the case of 4 (pl). Scheme 3(b) summarizes the mechanism for pd.

The mechanisms proposed for 4 (pl) and 4 (pd) must be applicable to 5 and 6. The expectations are just observed in δ(Se: 1)SCS and δ(Se: 2)SCS.

Applications of δ(Se: 1) and δ(Se: 2) as the standards

Odom made a lot of effort to explain δ(Se) of 7 based on the electronic effect of Y [13]. However, the attempt was not successful: δ(Se: 7) were not correlated well with δ(Se: 5). How are δ(Se) of p-YC6H4SeR interpreted based on the orientational effect? Our explanation for the relationship between δ(Se) of p-YC6H4SeR and the structures is as follows.

Figure 5 shows the plot of δ(Se: 5)SCS measured in CDCl3 [19] versus δ(Se: 1)SCS, 213 K and the correlation is given in Table 2 (entry 17: r = 0.997). The correlation coefficient is excellent when δ(Se: 5)SCS measured in neat is plotted versus δ(Se: 1)SCS, 213 K (entry 18 in Table 2: r = 0.999). These observations must be the results of the Se−CMe bond in 5 being on the p-YC6H4 plane in solutions for all Y examined, under the conditions. On the other hand, δ(Se: 7)SCS do not correlate with δ(Se: 1)SCS, 213 K. Instead, they correlate well with δ(Se: 2)SCS, 213 K (entry 19 in Table 2: r = 0.995). Figure 6 shows the plot. The results are rationally explained by assuming that the Se−CO bond in 7 is perpendicular to the p-YC6H4 plane in solutions for all Y examined, under the conditions.

Figure 5.

Figure 5

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Plot of δ(Se: 5)SCS versus δ(Se: 1)SCS, 213 k.

Figure 6.

Figure 6

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Plot of δ(Se: 7)SCS versus δ(Se: 2)SCS, 213 k.

δ(Se)SCS of 6 [19] and 8 [8] are similarly plotted versus δ(Se: 1)SCS, 213 K. They give good correlations, although the r values become poorer relative to that for 5 (entries 20 and 21 in Table 2). The reason would be the equilibrium of pl with pd for some Y in 6 and 8, may be Y of donors.

δ(Se)SCS of 9 are also plotted versus δ(Se: 1)SCS, 213 K. The correlations are excellent (entry 22 in Table 2: r = 0.999). It is worthwhile to comment that the energy lowering effect by Se4 4c–6e in 9 fixes the conformation 9 (pl, pl) for both p-YC6H4Se groups in solutions for all Y examined, under the conditions [50].

It is demonstrated that sets of δ(Se: 1) and δ(Se: 2) proposed in this work can be the standards for pl and pd, respectively, when δ(Se) of aryl selenides are analyzed based on the orientational effect.

CONCLUSION

The orientational effect is empirically established by the Y dependence on δ(Se: 1) and δ(Se: 2). The Y dependence observed in 1 and 2 is demonstrated by σt(Se) calculated for 4–6 with the DFT-GIAO method. While σt(Se) of 4a (pl) is predicted to be more negative than that of 4a (pd) by 46 ppm, σt(Se) of 5a (pl) is evaluated to be larger than that of 5a (pd) by 49 ppm, which corresponds to the orientational effect by the Ph group in 4a and 5a, respectively. Excellent to good correlations are obtained in the plots of σp(Se) versus (σp(Se)xx+σp(Se)yy) for 4–6 in pl and pd. It is demonstrated that (σp(Se)xx + σp(Se)yy) effectively controls σp(Se) of 4–6 in pl and pd.

The mechanisms of the Y dependence are proposed based on the magnetic perturbation theory. The main interaction in pl is the np(Se)-π(C6H4)-pz(Y) conjugation. Y dependence in pl occurs through admixtures of 4pz(Se) in modified π(SeC6H4Y) and π*(SeC6H4Y) with 4px(Se) and 4py(Se) in σ(CSeX) and σ*(CSeX) (X = H or C). The main interaction in pd is the σ(CSeX)-π(C6H4)-px(Y) type, which modifies both σ(CArSeH) and σ*(CArSeH). The Y dependence in pd mainly originates from admixtures of 4pz(Se) in np(Se) with 4px(Se) and 4py(Se) in modified σ*(CSeX) since np(Se) of 4pz(Se) is filled with electrons. Therefore, Y of both donors and acceptors are effective in pl, whereas Y of donors are more effective in pd. The expectations are just observed in 1 and 2. Sets of δ(Se: 1) and δ(Se: 2) can be used as the standards for pl and pd, respectively, when δ(Se) of aryl selenides are analyzed.

The effect of R in ArSeR is also important, which is in progress. The results will be discussed elsewhere, together with the applications of the method.

EXPERIMENTAL

NMR spectra were recorded at 25°C on a JEOL JNM-AL 300 spectrometer (1 H, 300 MHz; 13 C, 75.45 MHz; 77 Se, 57.25 MHz). The 1 H, 13 C, and 77 Se chemical shifts are given in parts per million relative to those of Me4Si, internal CDCl3 in the solvent, and external MeSeMe, respectively.

Preparation of compounds

1a–1j were prepared by the reactions of anthracenylgrignard reagents with arylselanylbromides and/or aromatic diazonium salts with anthracenylselenolates as the case of 3 [14]. 2a–2j were prepared by the reactions of 8-chloroanthraquione and arylselenolates with CuI as described earlier [51]. Elementary analyses for the compounds were satisfactory to those calculated within ±0.3% accuracy. 1 H, 13 C, and 77 Se NMR chemical shifts of the compounds rationalize the structures.

MO calculations

Quantum chemical (QC) calculations were performed using a Silent-SCC T2 (Itanium2) computer with the 6-311+G(3df) basis sets for Se and 6-311+G(3d,2p) for other nuclei of the Gaussian 03 program [47]. Calculations are performed on 4–6 in pl and pd at the density functional theory (DFT) level of the Becke three parameter hybrid functionals combined with the Lee-Yang-Parr correlation functional (B3LYP). Absolute magnetic shielding tensors of Se nuclei (σ(Se)) are calculated based on the gauge-independent atomic orbital (GIAO) method, applying on the optimized structures with the same method.

Structures of 1a–3a in various conformers are also optimized, containing frequency analysis, with the B3LYP/6-311+G(d,p) method.

Table 4.

Calculated absolute shielding tensors (σ(Se)) of 5, containing various Y (a) .

Y σd(Se) σp(Se)xx σp(Se)yy σp(Se)zz σp(Se) σt(Se)
5 (pl)
H 3006.5 −1893.4 −999.0 −1684.9 −1525.8 1480.7
NMe2 3007.7 −1645.4 −1194.5 −1669.5 −1503.1 1504.6
OMe 3007.4 −1741.5 −1136.8 −1677.1 −1518.4 1488.9
Me 3008.0 −1815.2 −1064.7 −1678.0 −1519.3 1488.7
F 3006.2 −1911.7 −990.8 −1680.6 −1527.7 1478.6
Cl 3006.7 −1639.8 −1269.8 −1682.4 −1530.7 1476.0
Br 3008.1 −1768.8 −1156.2 −1679.0 −1534.7 1473.5
COOMe 3009.6 −1840.5 −1132.8 −1687.1 −1553.5 1456.1
CN 3006.6 −1601.6 −1377.0 −1688.1 −1555.6 1451.0
NO2 3007.0 −1800.0 −1220.1 −1690.0 −1570.1 1436.9
5 (pd)
H 2998.0 −1956.8 −1086.4 −1656.9 −1566.7 1431.3
NMe2 3003.5 −1889.2 −1062.0 −1660.9 −1537.3 1466.2
OMe 3004.1 −1938.6 −1059.6 −1656.6 −1551.6 1452.5
Me 2999.8 −1908.0 −1090.1 −1657.2 −1551.8 1448.0
F 2998.1 −1916.6 −1077.7 −1663.9 −1552.8 1445.4
Cl 2999.3 −1925.8 −1078.6 −1664.3 −1556.2 1443.1
Br 3001.0 −1930.0 −1077.7 −1663.5 −1557.1 1443.9
COOMe 3006.4 −2017.8 −1057.8 −1658.7 −1578.1 1428.3
CN 2998.0 −1995.5 −1076.6 −1668.2 −1580.1 1417.9
NO2 2999.5 −1977.4 −1075.9 −1671.0 −1574.7 1424.7
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(a)Structures are optimized with the 6-311+G(3df) basis sets for Se and 6-311+G(3d,2p) basis sets for other nuclei at the DFT (B3LYP) level, assuming pl and pd for each of Y [47]. σ(Se) are calculated based on the DFT-GIAO method with the same methods.

ACKNOWLEDGMENT

This work was partially supported by a Grant-in-Aid for Scientific Research (no 16550038) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.

Footnotes

1 The contribution of relativistic terms has been pointed out for heavier atoms, but the perturbation would be small for the selenium nucleus.

2 This decomposition includes small arbitrariness due to the coordinate origin dependence, though it does not damage our chemical analyses and insights into the 77 Se NMR spectroscopy.

3 The 0.050 M CDCl3 solutions were used for NMR measurements. However, the concentrations would be lower for the compounds of low solubility, such as 1j and 2j, especially at 213 K.

4 When the axes from the Gaussian 03 program [47] are not the same as those shown in Scheme 3, axes are interchanged so as to be those in Scheme 3 for convenience of discussion, if possible.

5 Gaussian 03 (Revision B.05).

6 The torsional angle of φ = CoCiSeH in 4 (pd) is fixed at 90.0° if 4 (pd) is not the Cs symmetry (eg, Y = COOMe and OMe). Similarly, those of φ = CoCiSeCMe and φ = CiSeCMeH in 5 (pd) are fixed at 90.0° and 180°, respectively, and those of φ = CoCiSeCi' and φ = CiSeCi'Co' in 6 (pd) are fixed at 90.0° and 0°, respectively, when the conformers are not the Cs symmetry.

7 The DFT shieldings are deshielded in general, due to the underestimation of the orbital energy differences, which lead to the overestimation of the σp(Se) [48]. MP2 calculations are also performed on 4a (pl), 4a (pd), 5a (pl), and 5a (pd). The geometries are optimized with the MP2/6-311+G(3d,2p) method. σt(Se) are calculated with the MP2-GIAO method, employing the 6-311+G(2d,p) basis sets. The results are as follows (in ppm): (σt(Se: 4a (pl)), σt(Se: 4a (pd))) = (1827.3, 1865.5) and (σt(Se: 5a (pl)), σt(Se: 5a (pd))) = (1761.0, 1708.7). σt(Se: 4a (pl)) is evaluated to be more downfield than σt(Se: 4a (pd)) by 38 ppm, whereas σt(Se: 5a (pl)) is evaluated to be more upfield than σt(Se: 5a (pd)) by 52 ppm. The results support the orientational effects evaluated at the DFT level for 4a and 5a, although the basis sets are not the same.

8 σp(Se)zz is almost constant in the change of Y for both pl and pd in 4–6. The small Y-dependence of σp(Se)zz is reasonably explained through the main interaction of the 4pz(Se)-π(C6H4)-pz(Y) type in pl, where 4px(Se) and 4py(Se) do not take part in the interaction directly. The main interaction in pd is the σ(CArSeX)-π(C6H4)-px(Y) (X = H or C) type, which modifies the contributions of 4px(Se) and 4py(Se) in the C ArSeX bonds. However, the results show that the interaction in pd affects on σp(Se)xx and σp(Se)yy but not on σp(Se)zz.

9 σp is exactly expressed by Ramsey's equation [49]. While σp is evaluated accurately by the CPHF method, it is approximated as σpzz,N = −(μoe2/2m2e) Σiocc Σjunocc (ɛj − ɛi)−1 × {< ψi|^Lz|ψj >< ψj|^Lz,N rN −3|ψ i > + < ψ i|^Lz,N rN −3|ψ j >< ψ j|^Lz|ψ i >}.

10 The interactions between np(Se) of 4pz(Se) and phenyl σ orbitals in 4a (pd) must be weak due to large energy differences between 4pz(Se) and the σ orbitals. Long distances between them are also disadvantageous.

References

  • 1.Klayman DL, Günther WHH, editors. Organic Selenium Compounds: Their Chemistry and Biology. New York, NY: John Wiley & Sons; 1973. [Google Scholar]
  • 2.Patai S, Rappoport Z, editors. The Chemistry of Organic Selenium and Tellurium Compounds. Vol 1 and 2. New York, NY: John Wiley & Sons; 1986. [Google Scholar]
  • 3.Liotta D, editor. Organic Selenium Chemistry. New York, NY: Wiley-Interscience; 1987. [Google Scholar]
  • 4.Back TG, editor. Organoselenium Chemistry, A practical Approach. Oxford, Uk: Oxford University Press; 1999. [Google Scholar]
  • 5.Wirth T, editor. Organoselenium Chemistry: Modern Developments in Organic Synthesis. vol 208. Berlin, Germany: Springer; 2000. (Top. Curr. Chem.). [Google Scholar]
  • 6.MacFarlane W, Wood RJ. Nuclear magnetic double-resonance studies of organo-selenium compounds. Journal of Chemical Society, Dalton Transactions. 1972;13:1397–1401. [Google Scholar]
  • 7.Iwamura H, Nakanishi W. Recent application of of 77Se NMR spectroscopy in organoselenium chemistry. Journal of Synthetic Organic Chemistry Japan. 1981;39:795–804. [Google Scholar]
  • 8.Patai S, Rappoport Z, editors. The Chemistry of Organic Selenium and Tellurium Compounds, Vol. 1. Chapter 6. New York, NY: John Wiley & Sons; 1986. [Google Scholar]
  • 9.Klapotke TM, Broschag M, editors. Compilation of Reported 77Se NMR Chemical Shifts. New York, NY: John Wiley & Sons; 1996. [Google Scholar]
  • 10.Duddeck H. Selenium-77 nuclear magnetic resonance spectroscopy. Progress in Nuclear Magnetic Resonance Spectroscopy. 1995;27(1–3):1–323. [Google Scholar]
  • 11.Kalabin GA, Kushnarev DF, Bzesovsky VM, Tschmutova GA. 1H, 13C and 77Se NMR spectra of substituted selenoanisoles. Journal of Organic Magnetic Resonance. 1979;12(10):598–604. [Google Scholar]
  • 12.Kalabin GA, Kushnarev DF, Mannafov TG. NMR spectroscopy of selenium and tellurium organic compounds. III. parameters of proton, carbon-13, and selenium-77 spectra and structure of gem-dichlorocytopropylaryl selenides. Zhurnal Organicheskoi Khimii. 1980;16:505–512. [Google Scholar]
  • 13.Mullen GP, Luthra NP, Dunlap RB, Odom JD. Synthesis and multinuclear magnetic resonance study of para-substituted phenyl selenobenzoates. The Journal of Organic Chemistry. 1985;50(6):811–816. [Google Scholar]
  • 14.Nakanishi W, Hayashi S, Uehara T. Structure of 1-(Arylselanyl)naphthalenes - Y dependence in 1 − (p − YC6H4Se)C10H7 . European Journal of Organic Chemistry. 2001;2001(20):3933–3943. [Google Scholar]
  • 15.Hayashi S, Nakanishi W. Novel substituent effect on 77Se NMR chemical shifts caused by 4c-6e versus 2c-4e and 3c-4e in naphthalene peri positions: spectroscopic and theoretical study. The Journal of Organic Chemistry. 1999;64(18):6688–6696. doi: 10.1021/jo9903860. [DOI] [PubMed] [Google Scholar]
  • 16.Nakanishi W, Hayashi S, Yamaguchi H. Inverse substituent effect on 77Se NMR chemical shifts in naphthalene systems with linear 4c-6e Se4 Bond: 1 − [8 − (p − YC6H4Se)C10H6]SeSe[C10H6(SeC6H4Y − p)-8′] − 1′ vs.1 − (MeSe) − 8 − (p − YC6H4Se)C10H6 . Chemistry Letters. 1996;25(11):947–948. [Google Scholar]
  • 17.Nakanishi W, Hayashi S, Sakaue A, Ono G, Kawada Y. Attractive interaction caused by the linear F ⋯ Se − C alignment in naphthalene peri positions. Journal of the American Chemical Society. 1998;120(15):3635–3640. [Google Scholar]
  • 18.Nakanishi W, Hayashi S. Structure of 1-(Arylselanyl)naphthalenes. 2. G dependence in 8 − G − 1 − (p − YC6H4Se)C10H6 . The Journal of Organic Chemistry. 2002;67(1):38–48. doi: 10.1021/jo010380m. [DOI] [PubMed] [Google Scholar]
  • 19.Nakanishi W, Hayashi S. On the factors to determine 77Se NMR chemical shifts of organic selenium compounds: application of GIAO magnetic schielding tensor to the 77Se NMR spectroscopy. Chemistry Letters. 1998;27(6):523–524. [Google Scholar]
  • 20.Nakanishi W, Hayashi S. Structural study of Aryl selenides in solution based on 77Se NMR chemical shifts: application of the GIAO magnetic shielding tensor of the 77Se nucleus. The Journal of Physical Chemistry A. 1999;103(31):6074–6081. [Google Scholar]
  • 21.Sitkoff D, Gase DA. Density functional calculations of proton chemical shifts in model peptides. Journal of the American Chemical Society. 1997;119(50):12262–12273. [Google Scholar]
  • 22.Xu XP, Gase DA. Probing multiple effects on 15N, 13Cα, 13 Cβ and 13 C′ chemical shifts in peptides using density functional theory. Biopolymers. 2002;65(6):408–423. doi: 10.1002/bip.10276. [DOI] [PubMed] [Google Scholar]
  • 23.Wishart DS, Gase DA. Use of chemical shifts in macromolecular structure determination. Methods Enzymol. 2001;338:3–34. doi: 10.1016/s0076-6879(02)38214-4. [DOI] [PubMed] [Google Scholar]
  • 24.Xu XP, Gase DA. Automated prediction of 15N, 13Cα, 13Cβ and 13 C′ chemical shifts in proteins using a density functional database. Journal of Biomolecular NMR. 2001;21(4):321–333. doi: 10.1023/a:1013324104681. [DOI] [PubMed] [Google Scholar]
  • 25.Nakanishi W, Hayashi S, Shimizu D, Hada M. Orientational effect of Aryl groups on 77Se NMR chemical shifts: experimental and theoretical investigations. Chemistry—A European Journal. 2006;12(14):3829–3846. doi: 10.1002/chem.200500927. [DOI] [PubMed] [Google Scholar]
  • 26.Nakanishi W, Hayashi S, Uehara T. Successive change in conformation caused by p-Y groups in 1 – (MeSe) – 8 – (p – YC6H4Se)C10H6: role of linear Se ⋯ Se-C three-center-four-electron versus n(Se) ⋯ n(Se) two-center-four-electron nonbonded interactions. The Journal of Physical Chemistry A. 1999;103(48):9906–9912. [Google Scholar]
  • 27.Bordwen K, Grubbs EJ. Angular dependence of dipolar substituent effects. In: Taft RW, editor. Progress in Physical Organic Chemistry. Vol 19. New York, NY: John Wiley & Sons; 1993. pp. 183–224. [Google Scholar]
  • 28.Fukuda R, Hada M, Nakatsuji H. Quasirelativistic theory for the magnetic shielding constant. I. Formulation of Douglas-Kroll-Hess transformation for the magnetic field and its application to atomic systems. The Journal of Chemical Physics. 2003;118(3):1015–1026. [Google Scholar]
  • 29.Fukuda R, Hada M, Nakatsuji H. Quasirelativistic theory for magnetic shielding constants. II. Gauge-including atomic orbitals and applications to molecules. The Journal of Chemical Physics. 2003;118(3):1027–1035. [Google Scholar]
  • 30.Tanaka S, Sugimoto M, Takashima H, Hada M, Nakatsuji H. Theoretical study on metal NMR chemical shifts. Electronic mechanism of the Xe chemical shift. Bulletin of the Chemical Society of Japan. 1996;69(4):953–959. [Google Scholar]
  • 31.Ballard CC, Hada M, Kaneko H, Nakatsuji H. Relativistic study of nuclear magnetic shielding constants: hydrogen halides. Chemical Physics Letters. 1996;254(3-4):170–178. [Google Scholar]
  • 32.Nakatsuji H, Hada M, Kaneko H, Ballard CC. Relativistic study of nuclear magnetic shielding constants: mercury dihalides. Chemical Physics Letters. 1996;255(1–3):195–202. [Google Scholar]
  • 33.Hada M, Kaneko H, Nakatsuji H. Relativistic study of nuclear magnetic shielding constants: tungsten hexahalides and tetraoxide. Chemical Physics Letters. 1996;261(1-2):7–12. [Google Scholar]
  • 34.Grant DM, Harris RK, editors. Encyclopedia of Nuclear Magnetic Resonance. New York, NY: John Wiley & Sons; 1996. [Google Scholar]
  • 35.Tossell JA, editor. Nuclear Magnetic Shieldings and Molecular Structure. Dordrecht, The Netherlands: Kluwer Academic; 1993. [Google Scholar]
  • 36.Kaupp M, Bühl M, Malkin VG, editors. Calculation of NMR and EPR Parameters: Theory and Applications. Weinheim, Germany: Wiley-VCH; 2004. [Google Scholar]
  • 37.McWeeny R, editor. Spins in Chemistry. New York, NY: Academic Press; 1970. [Google Scholar]
  • 38.Markin VG, Malkina OL, Eriksson LA. A tool for chemistry. In: Seminario JM, Politzer P, editors. Modern Density Functional Theory. Amsterdam, The Netherlands: Elsevier; 1994. [Google Scholar]
  • 39.Springborg M, editor. Density-Functional Methods in Chemistry and Material Science. New York, NY: John Wiley & Sons; 1977. [Google Scholar]
  • 40.Kanda K, Nakatsuji H, Yonezawa T. Theoretical study of the metal chemical shift in nuclear magnetic resonance spectroscopy. Manganese complexes. Journal of the American Chemical Society. 1984;106(20):5888–5892. [Google Scholar]
  • 41.Atkins PW, Friedman RS, editors. Molecular Quantum Mechanics. 3rd ed. Oxford, NY: Oxford University Press; 1997. Chapter 13. [Google Scholar]
  • 42.Wolinski K, Hinton JF, Pulay P. Efficient implementation of the gauge-independent atomic orbital method for NMR chemical shift calculations. Journal of the American Chemical Society. 1990;112(23):8251–8260. [Google Scholar]
  • 43.Wolinski K, Sadlej A. Self-consistent perturbation theory. Open-shell states in perturbation-dependent non-orthogonal basis sets. Molecular Physics. 1980;41(6):1419–1430. [Google Scholar]
  • 44.Ditchfield R. Self-consistent perturbation theory of diamagnetism. I. A gauge-invariant LCAO method for NMR chemical shifts. Molecular Physics. 1974;27(4):789–807. [Google Scholar]
  • 45.McWeeny R. Perturbation theory for the fock-dirac density matrix. Physical Review. 1962;126(3):1028–1034. [Google Scholar]
  • 46.London F. Théorie quantique des courants interatomiques dans les combinaisons aromatiques. Journal de Physique et le Radium. 1937;8:397–409. [Google Scholar]
  • 47.Frisch MJ, Trucks GW, Schlegel HB, et al. Gaussian 03 (Revision B.05) Pittsburgh, Pa: Gaussian; 2003. [Google Scholar]
  • 48.Wilson PJ. Accurate non-relativistic density functional theory predictions for 77Se NMR shielding parameters. Molecular Physics. 2001;99(4):363–367. [Google Scholar]
  • 49.Ramsey NF. Magnetic shielding of nuclei in molecules. Physical Review. 1950;78(5):699–703. [Google Scholar]
  • 50.Nakanishi W. Hypervalent chalcogen compounds. In: Devillanova FA, editor. Handbook of Chalcogen Chemistry, New Perspectives in Sulfur, Selenium and Tellurium. Chapter 10.3. London, UK: Royal Society of Chemistry; 2006. [Google Scholar]
  • 51.Nakanishi W, Hayashi S, Itoh N. Extended hypervalent 5c-6e interactions: linear alignment of five C-Se—O—Se-C atoms in anthraquinone and 9-methoxyanthracene bearing Arylselanyl groups at the 1,8-positions. The Journal of Organic Chemistry. 2004;69(5):1676–1684. doi: 10.1021/jo035393+. [DOI] [PubMed] [Google Scholar]

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