First linear alignment of five C-Se...O...Se-C atoms in anthraquinone and 9-(methoxy)anthracene bearing phenylselanyl groups at 1,8-positions

Article abstract of DOI:10.1039/b209261a

Five C_i-Se...O...Se-C_i atoms in anthraquinone and 9-(methoxy)anthracene bearing phenylselanyl groups at 1,8-positions align linearly, the origin of which is shown to be a non-bonded 5c-6e interaction of the five atoms.

Full text of DOI:10.1039/b209261a

First linear alignment of five C–Se…O…Se–C atoms in anthraquinone
and 9-(methoxy)anthracene bearing phenylselanyl groups at
1,8-positions†
Waroˆ Nakanishi,* Satoko Hayashi and Norio Itoh
Department of Material Science and Chemistry, Faculty of Systems Engineering, Wakayama University, 930
Sakaedani, Wakayama 640-8510, Japan. E-mail: nakanisi@sys.wakayama-u.ac.jp; Fax: +81 73 457 8253;
Tel: +81 73 457 8252
Received (in Cambridge, UK) 23rd September 2002, Accepted 7th November 2002
First published as an Advance Article on the web 25th November 2002
Five Ci–Se…O…Se–Ci atoms in anthraquinone and 9-(me-
thoxy)anthracene bearing phenylselanyl groups at 1,8-posi-
tions align linearly, the origin of which is shown to be a non-
bonded 5c–6e interaction of the five atoms.
phenyl planes in 1 are perpendicular to the anthraquinone plane.
Conformations around the Se atoms of 2 are also both type B8
(2 (BB)). The five atoms in 2 also align linearly with Se(1)–
O(1)–Se(2) 148°. Indeed, the structure of 2 is very similar to
that of 1, but is closer to Cs symmetry. However, the structure
of 3 is very different from those of 1 and 2. The conformations
around the Se atoms are both type A8 (3 (AA)). Two phenyl
groups are located at the same sides of the plane (3 (AA-cis)).
It is well demonstrated that the double type A structure in 3
changes dramatically to the double type B in 1 and 2 with each
O atom at the 9-position.
Non-bonded interactions1 are of great interest. This is especially
so if they lead to linear bonds longer than the three center–four
electron bond (3c–4e) through direct orbital overlaps containing
group 16 elements.2 Naphthalene 1,8-positions supply a good
system to study such non-bonded interactions, containing 2c–
4e, 3c–4e and 4c–6e interactions.2–5 However, the nature of the
5c–6e interaction is as yet not well understood. Anthracene
1,8,9-positions also serve as a good system for such inter-
actions.6
Five C–Se…O…Se–C atoms are shown to align linearly for
1,8-bis(phenylselanyl)anthraquinone (1)† and 9-(methoxy)-
1,8-bis(phenylselanyl)anthracene (2).†The linear alignment can
be analyzed by the 5c–6e model. The structure of 1,8-bis-
(phenylselanyl)anthracene (3)†is also investigated for conven-
ience of comparison, in which five C–Se…H…Se–C atoms are
not aligned linearly.
The p-type lone pair orbitals of the O atoms (np (O)) in 1 and
x
2 extend toward the Se atoms (the axes in 1 (and 2) are defined
in Fig. 4). Observed non-bonded Se…O distances of 2.67–2.74
Å are about 0.7 Å shorter than the sum of their van der Waals
radii (3.40 Å).9 Therefore, np (O) directly overlaps with the
s*(Se–C) orbitals at both sides xof np (O). If the two non-bonded
x
O…Se–C 3c–4e interactions are connected effectively through
the central np (O), the non-bonded s*(C–Se)…np (O)…s*(Se–
x
x
C) 5c–6e arrangement is formed. The 5c–6e interaction must
play an important role in the double type B structures of 1 and
2.
Figs. 1–3‡ show the structures of 1–3, respectively.7
Conformations around the two Se atoms are both type B8 (1
(BB)). Consequently, the five C–Se…O…Se–C atoms align
linearly with Se(1)–O(1)–Se(2) 153°. The slightly bent align-
ment is a reflection of the differences in the r(C,O) and r(C,Se)
values. The structure of 1 is close to C2 symmetry. The two
Fig. 2 Structure of 2. Selected bond lengths (Å), angles (°) and torsion
angles (°): Se(1)–C(1) 1.930(4), Se(1)–C(15) 1.921(5), Se(2)–C(11)
1.932(5), Se(2)–C(21) 1.938(5), C(13)–O 1.387(5), C(27)–O 1.436(6),
Se(1)–O 2.731(3), Se(2)–O 2.744(3); C(1)–Se(1)–C(15) 99.2(2), C(11)–
Se(2)–C(21) 99.9(2), C(13)–O–C(27) 111.7(4), Se(1)–O–Se(2) 147.9(1);
C(14)–C(1)–Se(1)–C(15) –163.1(4), C(12)–C(11)–Se(2)–C(21) 175.8(4),
C(1)–Se(1)–C(15)–C(16) –104.2(5), C(11)–Se(2)–C(21)–C(22) 88.3(5),
C(14)–C(13)–O–C(27) 89.1(5).
Fig. 1 Structure of 1. Selected bond lengths (Å), angles (°) and torsion
angles (°): Se(1)–C(1), 1.922(7), Se(1)–C(15) 1.924(6), Se(2)–C(11)
1.917(6), Se(2)–C(21) 1.927(6), C(13)–O(1) 1.225(7), Se(1)–O(1)
2.688(4), Se(2)–O(1) 2.673(4); C(1)–Se(1)–C(15) 98.5(3), C(11)–Se(2)–
C(21) 100.2(3), Se(1)–O(1)–Se(2) 152.5(2); C(14)–C(1)–Se(1)–C(15)
2172.8(6), C(12)–C(11)–Se(2)–C(21) 2171.3(5), C(1)–Se(1)–C(15)–
C(16) 90.5(6), C(11)–Se(2)–C(21)–C(22) 103.5(6).
Fig. 3 Structure of 3. Selected bond lengths (Å), angles (°) and torsion
angles (°): Se(1)–C(1) 1.923(3), Se(1)–C(15) 1.923(3), Se(2)–C(11)
1.943(3), Se(2)–C(21) 1.931(3); C(1)–Se(1)–C(15) 100.3(1), C(11)–Se(2)–
C(21) 98.3(1); C(14)–C(1)–Se(1)–C(15) 72.6(3), C(12)–C(11)–Se(2)–
C(21) –103.0(3), C(1)–Se(1)–C(15)–C(16) 6.7(3), C(11)–Se(2)–C(21)–
C(22) 85.8(3).
† Electronic supplementary information (ESI) available: experimental
procedures, analytical and spectroscopic data for 1–3. See http://
www.rsc.org/suppdata/cc/b2/b209261a/
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CHEM. COMMUN., 2003, 124–125
This journal is © The Royal Society of Chemistry 2003

Notes and references
‡ Crystal data: for 1: monoclinic, space group P21/n (#14), a = 7.412(2),
b = 16.002(2), c = 17.682(2) Å, b = 93.58(2)°, V = 2092.9(7) Å3, Z = 4.
¯
For 2: triclinic, space group P1 (#2), a = 10.930(3), b = 13.673(4), c =
8.052(2) Å, a = 96.64(2), b = 102.20(3), g = 106.48(2)°, V = 1107.9(6)
¯
Å3, Z = 2. For 3: triclinic, space group P1 (#2), a = 10.598(3), b =
11.575(3), c = 9.947(3) Å, a = 113.59(2), b = 95.42(2), g = 109.39(2)°,
V = 1017.6(6) Å3, Z = 2. Rigaku AFC5R four-circle diffractometer, Mo-
Ka radiation (l = 0.71069 Å). The structure analyses are based on 2756
observed reflections with I > 1.50s(I) for 1, on 2795 for 2 and on 3395 for
3 and 271 variable parameters for 1, 271 for 2 and 253 for 3. The structures
of 1–3 were solved by heavy-atom Patterson methods (PATTY) and
expanded using Fourier techniques (DIRDIF94) and refined by full-matrix
Fig. 4 HOMO 2 2 drawn on the optimized structure of 1 (BB).
2
Quantum chemical calculations are performed on 1–3,
together with 1-(phenylselanyl)anthraquinone (4) and 9-(me-
thoxy)-1-(phenylselanyl)anthracene (5), at the DFT (B3LYP)
level.10 Conformers, AA, AB and BB, are optimized to be stable
for 1 and 2, which correspond to 3c–6e, 4c–6e and 5c–6e,
respectively. The results are collected in Table 1.11 Energies
evaluated for each process from 1 (AA) to 1 (BB) (32–29 kJ
mol21) are very close to that in 4.12 The average value from 2
(AA) to 2 (BB) (18 kJ mol21) is close to that in 5.12These results
least squares on ¡F¡ . R = 0.046, Rw = 0.029, GOF = 1.51 for 1, R =
0.040, Rw = 0.030, GOF = 1.59 for 2 and R = 0.034, Rw = 0.026, GOF
= 2.46 for 3. CCDC reference numbers 175767 (1), 175768 (2) and 175769
(3). See http://www.rsc.org/suppdata/cc/b2/b209261a/ for crystallographic
data in CIF or other electronic format.
1 ed. S. Scheiner, Molecular Interactions. From van der Waals to
Strongly Bound Complexes, Wiley, New York, 1997; K. D. Asmus, Acc.
Chem. Res., 1979, 12, 436–442; W. K. Musker, Acc. Chem. Res., 1980,
13, 200–206.
demonstrate that the non-bonded s*(C–Se)…np (O)…s*(Se–
2 W. Nakanishi, S. Hayashi and S. Toyota, J. Org. Chem., 1998, 63,
8790–8800; W. Nakanishi, S. Hayashi and T. Uehara, J. Phys. Chem. A,
1999, 103, 9906–9912; S. Hayashi and W. Nakanishi, J. Org. Chem.,
1999, 64, 6688–6696; W. Nakanishi, S. Hayashi, A. Sakaue, G. Ono and
Y. Kawada, J. Am. Chem. Soc., 1998, 120, 3635–3646; W. Nakanishi
and S. Hayashi, J. Org. Chem., 2002, 67, 38–48; W. Nakanishi, S.
Hayashi and A. Arai, Chem. Commun., 2002, 2416–2417.
3 R. S. Glass, S. W. Andruski, J. L. Broeker, H. Firouzabadi, L. K. Steffen
and G. S. Wilson, J. Am. Chem. Soc., 1989, 111, 4036–4045; R. S.
Glass, L. Adamowicz and J. L. Broeker, J. Am. Chem. Soc., 1991, 113,
1065–1072.
4 F. B. Mallory, C. W. Mallory and M.-C. Fedarko, J. Am. Chem. Soc.,
1974, 96, 3536–3542; F. B. Mallory, C. W. Mallory, K. B. Butler, M. B.
Lewis, A. Q. Xia, E. D. Luzic, L. E. Fredenburgh, M. M. Ramanjulu, Q.
N. Van, M. M. Francl, D. A. Freed, C. C. Wray, C. Hann, M. Nerz-
Stormer, P. J. Carroll and L. E. Chirlian, J. Am. Chem. Soc., 2000, 122,
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5 H. Fujihara, H. Ishitani, Y. Takaguchi and N. Furukawa, Chem. Lett.,
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Shimizu and N. Kamigata, Heteroat. Chem., 2001, 12, 227–237.
6 For example, Akiba et al. reported the 1,8-dimethoxy-9-dimethox-
ymethylanthracene monocation as a model of the transition state of the
SN2 reaction: K-y. Akiba, M. Yamashita, Y. Yamamoto and S. Nagase,
J. Am. Chem. Soc., 1999, 121, 10644–10645; see also: M. Yamashita, Y.
Yamamoto, K-y. Akiba and S. Nagase, Angew. Chem., Int. Ed., 2002,
39, 4055–4058.
x
C) 5c–6e interaction is effectively present in 1 and 2.13 The two
non-bonded 3c–4e interactions are well connected through the
central np (O) orbital. Some MOs in 1 and 2 extend over the five
x
C–Se…O…Se–C atoms as shown in Fig. 4, exemplified by
HOMO 2 2 in 1 (BB),14 which supports the above discus-
sion.
Table 1 Relative energies of the conformers in 1–3a
Conformation
1
2
3
AA-trans
AA-cis
AB
0.0b
0.0c
2.1
0.5
3.7
0.0d
224.4
236.5
231.5
260.6
BB
a kJ mol21
25919.2120 au.
. = = =
b E 25953.9764 au. c E 25804.6946 au. d E
It is worthwhile to comment on the through p-bond
interactions between np (Se) and np (O) via the p-framework of
z
z
anthracene in 1. Since the carbonyl group acts as a good electron
acceptor, electron densities at O and Se atoms in 1 become
larger and smaller, relative to those without such interactions,
respectively. This will create advantageous conditions for the
non-bonded 5c–6e interaction, since the character of CT is of
7 The structures of p,pA-dichloro derivatives of 1 and 3 are substantially
the same as those of 1 and 3, respectively.
the type s*(C–Se)/np (O)?s*(Se–C). The rigid structure in 1,
x
8 Structures of the naphthalene system, 8-G-1-(ArSe)C10H6, are well
classified using type A, type B and type C, where the Se–CAr bond is
placed almost perpendicular to the naphthyl plane in type A, the bond is
located on the plane in type B and type C is intermediate between type
A and type B. The notation is applied to the structures of 1–3. See ref.
2 and W. Nakanishi and S. Hayashi, Eur. J. Org. Chem., 2001, 20,
3933–3943.
9 L. Pauling, The Nature of the Chemical Bond, Cornell University Press,
Ithaca, New York, 3rd edn., 1960, ch. 7.
10 Gaussian 98, Revision A.9 is employed for the calculations (J. A. Pople
et al., Gaussian, Inc., Pittsburgh PA, 1998).11 The 6-311+G(d) basis sets
are employed for Se and O atoms and the 6-31G(d) basis sets for C and
H atoms.
except for the rotation around the Se–C bonds, must be
advantageous for the p-conjugation. Almost equal stabilization
energies calculated in each process from 1 (AA) to 1 (BB) must
arise from the rigid structure. Lack of the effective p-
conjugation between np (Se) and np(O) through the p-frame-
work in 2 must be reszponsible for the smaller stabilization
energies evaluated for the corresponding processes relative to
those in 1. The additional flexibility around C–O bonds in 2
would also play an important role in its characteristic energy
profile.
11 Details are shown in the ESI†.
12 4 (B) and 5 (B) are more stable than 4 (A) and 5 (A) by 30.5 and 14.7
kJ mol21, respectively.
13 Model calculations are also performed on model a (HaAHbABSe…(H2C-
N)O…ASeHaHb) and model b (HaAHbABSe…(H2)O…ASeHaHb) with the
B3LYP/6-311++G(3df,2pd) method. The non-bonded Se…O distances
in the models are fixed at 2.658 Å, observed in the phenyl p,pA-dichloro
derivative of 1. No noticeable saturation is predicted in the energy
lowering effect in each conformational change from type A to type B in
the models. The results also support the 5c–6e nature of the s*(H–
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Areas (A) (Nos. 11120232, 11166246, and
12042259) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan, by a Grant-in-Aid for
Encouragement of Young scientists (No. 13740354) from Japan
Society for Promotion of Science, and by the Hayashi Memorial
Foundation for Female Natural Scientists.
Se)…np (O)…s*(Se–H) interaction in the models.
x
14 The MacSpartan Plus program Ver. 1.0 is used (H. J. Hehre,
Wavefunction Inc., Irvine, CA 92612, USA).
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