Structural and spectral studies of N-2-(pyridyl)-, N-2-(4-, 5-, and 6-picolyl)- and N-2-(4,6-lutidyl)-N′-2-methoxyphenylthioureas

Article abstract of DOI:10.1016/S0022-2860(00)00824-3

N-2-(pyridyl)-N′-2-methoxyphenylthiourea, PyTu2OMe, monoclinic, C2/c, a = 15.727(3), b = 11.251(2), c = 15.026(4) ?, β = 104.78(2)°, V = 2570.9(2) ?³ and Z = 8; N-2-(4-picolyl)-N′-2-methoxyphenylthiourea, 4PicTu2OMe, orthorhombic, Pbca, a = 11.

Full text of DOI:10.1016/S0022-2860(00)00824-3

Journal of Molecular Structure 562 (2001) 95±105
www.elsevier.nl/locate/molstruc
Structural and spectral studies of N-2-(pyridyl)-, N-2-(4-, 5-, and
6-picolyl)- and N-2-(4,6-lutidyl)-N0-2-methoxyphenylthioureas
*
Douglas X. West , John K. Swearingen, Ann K. Hermetet, Lily J. Ackerman
Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA
Received 15 May 2000; accepted 17 October 2000
Abstract
0
ꢀ
N-2-(pyridyl)-N -2-methoxyphenylthiourea, PyTu2OMe, monoclinic, C2/c, a ˆ 15:727ꢀ3†; b ˆ 11:251ꢀ2†; c ˆ 15:026ꢀ4† A;
b ˆ 104:78ꢀ2†8; V ˆ 2570:9ꢀ2† A and Z ˆ 8; N-2-(4-picolyl)-N0-2-methoxyphenylthiourea, 4PicTu2OMe, orthorhombic,
ꢀ 3
Pbca, a ˆ 11:439ꢀ9†; b ˆ 15:897ꢀ6†; c ˆ 14:920ꢀ6† A; V ˆ 2713:0ꢀ4† A and Z ˆ 8; N-2-(5-picolyl)-N0-2-methoxyphe-
ꢀ
ꢀ 3
ꢀ
nylthiourea, 5PicTu2OMe, triclinic, P-1, a ˆ 7:586ꢀ2†; b ˆ 8:505ꢀ3†; c ˆ 11:308ꢀ5† A; a ˆ 73:29ꢀ3†; b ˆ 89:04ꢀ3†; g ˆ
0
ꢀ 3
83:38ꢀ3†8; V ˆ 694:0ꢀ6† A and Z ˆ 2; N-2-(6-picolyl)-N -2-methoxyphenylthiourea, 6PicTu2OMe, monoclinic, P21/c, a ˆ
0
ꢀ
ꢀ 3
11:372ꢀ4†; b ˆ 15:808ꢀ4†; c ˆ 16:141ꢀ7† A; b ˆ 102:96ꢀ3†8; V ˆ 2827:8ꢀ3† A and Z ˆ 8 and N-2-(4,6-lutidyl)-N -2-methox-
ꢀ
yphenylthiourea, 4,6LuTu2OMe, monoclinic, P21/n, a ˆ 7:546ꢀ4†; b ˆ 23:400ꢀ5†; c ˆ 8:927ꢀ5† A; b ˆ 109:42ꢀ5†8; V ˆ
1486:7ꢀ2† A and Z ˆ 4: Some of these molecules have a bifurcated intramolecular hydrogen bond between N0H and the
ꢀ 3
pyridyl nitrogen and the 2-methoxy oxygen, and all have intermolecular hydrogen bonding between NH and a thione sulfur of a
second molecule to form centrosymmetric dimers. Solution H NMR studies (CDCl3) show the N0H resonance considerably
1
down®eld for each thiourea and its position, as well as that of NH, is affected by substituents on the pyridyl ring. q 2001
Elsevier Science B.V. All rights reserved.
Keywords: Heterocyclic thioureas; Bifurcated hydrogen bonding; Crystal structures; 2-methoxyphenylthioureas
1. Introduction
to form a two-dimensional network in these latter
thioureas. In addition, crystal structures0of substituted
thioureas with intermolecular N±H´´´S bonding, but
without intramolecular hydrogen bonding, have been
reported [10±14]. More recent studies of substituted N-
(2-pyridyl0)-N0-phenylthioureas including N-2-(4,6-
lutidyl)-N -phenylthiourea, 4,6LuTuPh [15], N-(2-
pyridyl)-N0-tolylthioureas [16] and the three N-2-
(4,6-lutidyl)-N0-tolylthioureas [17] have been repor-
ted, as has N-(5-bromo-2-pyridyl)-N0-[2-(2,5-dime-
thoxyphenyl)ethyl]thiourea [18]. These compounds
feature both intramolecular and intermolecular
hydrogen bonding. Here we report the crystal struc-
tures and lattice arrangements for ®ve heterocyclic 2-
methoxyphenylthioureas, Fig. 1, which are capable of
1
For 2-pyridyl thioureas H NMR correctly predicts
intramolecular0hydrogen bonding between the pyridyl
nitrogen and N H [1], but only recently has a structural
study been reported for N-(2-pyridyl)-N0-phenylthio-
urea [2]. Studies of a number of substituted thioureas,
including N-benzoyl-N0-thioureas, indicate an intra-
molecular hydrogen bond between N0H and an oxygen
(e.g. benzoyl, etc.) [3±9]. There is also an intermole-
cular NH´´´S interaction with a neighboring molecule
* Corresponding author. Tel.: 11-309-438-7661; fax: 11-309-
438-5538.
E-mail address: dxwest@ilstu.edu (D.X. West).
0022-2860/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00824-3

96
D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
possessing both intermolecular and bifurcated intra-
molecular hydrogen bonding.
2. Experimental
2-Aminopyridine, the four 2-aminopicolines and 2-
amino-4,6-lutidine, as well as 2-methoxyphenyl
isothiocyanate, were purchased from Aldrich and
used as received. 2-Methoxyphenyl isothiocyanate
and a 2-aminopyridine were dissolved in a 1:1
molar ratio in 95% ethanol, and the resulting mixture
gently re¯uxed for a minimum of 1 h. On cooling and
slowly evaporating (358C) the reactant mixture, the
thioureas crystallized from solution. The solids were
®ltered, washed with cold isopropanol followed by
anhydrous ether, dried on a warm plate and then
Fig. 1. A representation of bifurcated N-2-(4-picolyl)-N0-2-methox-
yphenylthiourea, 4PicTu2OMe, with expected intermolecular
hydrogen bonding.
Table 1
Crystallographic data and methods of data collection, solution and re®nement for PyTu2OMe, 4PicTu2OMe and 5PicTu2OMe
Crystal data
PyTu2OMe
C13H13ON3S
Colorless, prism
0.30 £ 0.24 £ 0.20
Monoclinic
C2/c
4PicTu2OMe
C14H15ON3S
Colorless, prism
0.30 £ 0.25 £ 0.15
Orthorhombic
Pbca
5PicTu2OMe
C14H15ON3S
Colorless, prism
0.25 £ 0.20 £ 0.12
Triclinic
P-1
Empirical formula
Crystal color, habit
Crystal size (mm)
Crystal system
Space group
Ê
a (A)
15.727(3)
11.251(2)
15.026(4)
90(0)
11.439(9)
15.897(6)
14.920(6)
90(0)
7.586(2)
Ê
b (A)
Ê
c (A)
8.505(3)
11.308(5)
73.29(3)
a (8)
b (8)
g (8)
104.78(2)
90(0)
90(0)
89.04(3)
90(0)
83.38(3)
Ê 3
Volume (A )
Z
2570.9(2)
8
2713.0(4)
8
694.0(6)
2
Formula weight
Density (calcd.) (g/cm3)
259.3
273.4
273.4
1.340
1.339
1.308
Absorp. coeff. (mm21
F(000)
)
0.243
0.234
0.229
1088
1152
288
Index ranges
0 # h # 20
0 # k # 14
219 # l # 18
6630
0 # h # 14
0 # k # 20
219 # l # 19
7026
0 # h # 9
210 # k # 11
214 # l # 14
3554
Re¯ections collected
Independent re¯ections
Observed re¯ections
2957
3122
3176
1268 {I . 3.0 s (I)}
c-scan
1606 {I . 3.0 s (I)}
None
2198{I . 3.0 s (I)}
c-scan
Absorption correction
Max. and min. transmissions
1.000 and 0.937
1.980
1.000 and 0.993
0.443
Goodness-of-®t
Ê 23
2.780
Largest diff. peak (eA
Largest diff.hole (eA
R, wR
)
0.47
20.22
0.59
20.34
0.58
20.19
Ê 23
)
0.0432, 0.0435
0.1748, 0.1467
0.0567, 0.0885
0.1305, 0.1200
0.0372, 0.0374
0.0693, 0.0623
R, wR (all re¯ections)

D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
97
Table 2
Crystallographic data and methods of data collection, solution and re®nement for 6PicTu2OMe and 4,6LuTu2OMe
Crystal data
6PicTu2OMe
C14H15ON3S
Colorless, prism
0.32 £ 0.24 £ 0.14
Monoclinic
P21/c
4,6LuTu2Ome
C15H17ON3S
Colorless, prism
0.30 £ 0.20 £ 0.12
Monoclinic
P21/n
Empirical formula
Crystal color, habit
Crystal size (mm)
Crystal system
Space group
Ê
A (A)
Ê
B (A)
Ê
C (A)
11.372(4)
15.808(4)
16.141(7)
90(0)
7.546(4)
23.400(5)
8.927(5)
A (8)
B (8)
G (8)
90(0)
102.96(3)
90(0)
109.42(5)
90(0)
Ê 3
Volume (A )
Z
2827.8(3)
8
1486.7(2)
4
Formula weight
Density (calcd.) (g/cm3)
273.4
287.4
1.284
1.284
Absorp. coeff. (mm21
)
0.225
0.217
F(000)
1152
600
Index ranges
0 # h # 14
0 # k # 20
220 # l # 20
7305
0 # h # 9
0 # k # 30
211 # l # 10
3897
Re¯ections collected
Independent re¯ections
Observed re¯ections
6468
3306 {I . 3.0s (I)}
c-scan
3403
2153 {I . 3.0s (I)}
c-scan
Absorption correction
Max. and min. transmissions
1.000 and 0.970
1.259
1.000 and 0.982
0.844
Goodness-of-®t
Ê 23
Largest diff. peak (eA
)
0.46
0.53
Ê 23
Largest diff.hole (eA
)
20.29
20.28
R
wR
0.0469, 0.0487
0.1209, 0.0893
0.0505, 0.0494
0.0958, 0.0778
stored until required for characterization. The yields
are ca. 75% for each of the thioureas and the melting
points are as follows: PyTu2OMe, 207±2088C;
3PicTu2OMe, 120±1228C; 4PicTu2OMe, 196±
1988C; 5PicTu2OMe, 194±1958C; 6PicTu2OMe,
168±1698C and 4,6LuTu2OMe, 203±2048C. Their
1H NMR spectra were recorded in CDCl3 with a
Varian Gemini 2000 300 MHz spectrometer and UV
spectra (CHCl3) with a Cary 5E spectrophotometer in
1 cm cells.
Colorless, prismatic crystals of the thioureas were
grown by slow evaporation of acetone±ethanol solu-
tions (1:1 by volume) at room temperature. Crystals
were mounted on glass ®bers and used for data collec-
tion on a Nonius MACH3 automatic diffractometer,
obtained by least squares re®nements of the diffrac-
tion data from 25 re¯ections. The structures were
solved with direct methods and missing atoms were
found by difference-Fourier synthesis. All non-
hydrogen atoms were re®ned with anisotropic
temperature factors and hydrogens attached to
nitrogens were found on the difference Fourier
map. The H atoms of CH were ®xed at d ˆ
ꢀ
0:96 A and allowed to ride on the C atoms and
assigned ®xed isotropic temperature factor, U ˆ
ꢀ 2
0:05 A : The coordinates of the H atoms attached
to N and N0 were re®ned isotropically. Re®nement
of the structures was made by full-matrix least-
squares on F. Scattering factors are from
Wassmaire and Kirfel [19], calculations were
done by maXus, version 2.0 [20], and graphics
are Platon for Windows [21].
ꢀ
MoKa ꢀl ˆ 0:71073 A† at 293 K. Cell constants and
an orientation matrix for data collections were

98
D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
Fig. 2. ORTEP of the non-bifurcated PyTu2OMe with atom numbering scheme and displacement ellipsoids at 50% probability level.
3. Results and discussion
non-bifurcated PyTu2OMe, bifurcated 4PicTu2OMe
and views of the two showing their differences in
planarity are shown in Figs. 2±4, respectively. Fig.
5 shows two crystallographically unique molecules
of 6PicTu2OMe, and Fig. 6 shows the packing
diagram for 4,6LuTu2OMe with the intermolecular
and intramolecular hydrogen bonding indicated.
These ®ve thioureas are in a conformation resulting
from intramolecular hydrogen bonding of N3H3 (i.e.
N0H) to the pyridine nitrogen, N1, in a manner similar
to the 2-benzoylthioureas [3±8] and trans±cis like
N-cyclohexyl-N0-phenylthiourea [12]. In addition,
hydrogen bonding by N3H3 interacting with O of
the methoxy function results in H3 bifurcation,
which is present in some, but not all of these thioureas
3.1. Structural studies
The crystallographic data, as well as the solution and
re®nement information for these thioureas, are shown in
Tables 1 and 2, and the atomic coordinates and equiva-
lent isotropic displacement coef®cients are included in
the deposited material (CCDC), as are a complete list of
bond distances and angles. The CCDC nos. are as
follows: PyTu2OMe, 143737; 4PicTu2OMe, 143734;
5PicTu2OMe, 143735; 6PicTu2OMe, 143736 and
4,6LuTu2OMe, 117372.
0The molecular structures of the ®ve N-heterocyclic
N -2-methoxyphenylthioureas are represented by the

D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
99
Fig. 3. ORTEP of the bifurcated 4PicTu2OMe with atom numbering scheme and displacement ellipsoids at 50% probability level.
(vide infra). Inspection of Table 3 shows that selected
bond distances for the ®ve thioureas are generally
within three orders of magnitude of their estimated
standard deviations. The largest differences are
found for the N2±C7 and N3±C8 bonds of
4,6LuTu2OMe, which may be attributed to a packing
effect due to the added bulkiness of two methyl
groups. The bond angles show greater variation; the
angles involving the aromatic ring bonding to N3 and
within the thiourea moiety show the greatest variation.
For example, C7±N3±C8 ranges from 123.1(4)8
(PyTu2OMe) to 130.9(6)8 (4PicTu2OMe) and N3±
C8±C9 from 114.1(7)8 (4PicTu2OMe) to 119.4(4)8
(PyTu2OMe). Therefore, both the presence and posi-
tion of methyl groups on the heterocyclic ring affects
the bonding of the thiourea moiety, and whether H3 is
bifurcated (vide infra).
The mean plane deviations show the pyridine rings,
thiourea moieties and aryl rings in the ®ve compounds
are quite planar, Table 4. The atoms farthest out of the
various planes are included in Table 4 and con®rm
that all atoms are quite close to their mean planes. The
angles between the mean planes provide information on
the nature of the intramolecular hydrogen bonding. The
greater the planarity of the entire molecule, which is
conveniently indicated by the angle between the planes
of the pyridyl ring and the aromatic ring, the more likely
that the N3H3 hydrogen is bifurcated.
Shown in Table 5 are the possible intramolecular
hydrogen bonding interactions of N3H with N1 and
O1. The listings in italics designate non-hydrogen
bonding. The ORTEP drawing for PyTu2OMe clearly
shows that N3H is not hydrogen bonding to O1 (i.e.
not bifurcated) and the angle between the pyridyl and
aryl mean planes is 80.8(3.5)8 and shown in Table 5
that such an interaction would have a D±H´´´A angle
of 62.1(3)8. Similarly, 5PicTu2OMe does not have
bifurcated hydrogen bonding based on a D±H´´´A
angle of 87.6(2)8; its angle between the pyridyl and
aryl mean planes is 48.9(3.5)8, the second largest
angle between the two planes in this series. The inter-
action between N3H and O1 in 4,6LuTu2OMe is
weak at best, but de®nitely present in the more planar
6PicTu2OMe (both forms, but one more than the
other) and the strongest in the most planar of the
series, 4PicTu2OMe. All ®ve of these thioureas
show the expected interaction by N3H with N1 of
the pyridine ring. Using the H´´´A distances as an
indicator of the strength of the interaction gives
the following order 4 PicTu2OMe . 4,6LuTu2OMe
.5PicTu2OMe ˆ 6PicTu2OMe ˆ PyTu2OMe,
suggesting that interaction with O1 does not affect the
strength of interaction with N1. Based on H´´´A
distances these interactions are all stronger than
found for pyridyl thioureas without the 2-methoxy
function. N-(2-pyridyl)-N0-phenylthiourea [2],

100
D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
Fig. 4. End on views of 4PicTu2OMe (a) and PyTu2OMe (b) showing the difference in the angles between the pyridyl and aryl mean planes.
N-(2-pyridyl)-N0-(2-tolyl)thiourea [16] and N-(4,6-
lutidyl)-N 0-(2-tolyl)thiourea [17] have H´ ´ ´A
Ê
distances of 1.96(3), 1.944(4) and 1.896(2) A, respec-
tively. These distances are longer than found for the
analogous compounds of the present series further
suggesting that bifurcation does not weaken the
N3H3´´´N1 interaction. Therefore, the angle between
mean planes of the pyridyl and aryl rings is a useful
indicator of H3 bifurcation and Fig. 7 shows a plot of
this angle versus the H´´´O and H´´´N distances for
these thioureas. There is a nearly linear arrangement
of the H´´´O distances with the angle between the
planes and a clear indication that the distance of the
N´´´H interaction is unaffected by this angle. Further,
the distance of the N´´´H interaction is also not
affected by whether the hydrogen is bifurcated or not.
The lower half of Table 5 shows the intermolecular
N2H2´´´S interactions that result in centrosymmetric
dimer formation, Fig. 5. The distances and angles for
this interaction among these ®ve thioureas are similar,
but the strongest N3H3´´´O1 bonding molecule,
4PicTu2OMe, has the longest H2´´´S1#1 distance,

D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
101
Fig. 5. ORTEP of the two crystallographically unique molecules of bifurcated 6PicTu2OMe with atom numbering scheme and displacement
ellipsoids at 50% probability level.
but the non-bifurcated PyTu2OMe and 5PicTu2OMe
have the second longest and shortest H2´´´S1#1
distances, respectively. This suggests that the intra-
molecular and intermolecular hydrogen bonding
interactions are independent of each other in these
molecules. Also included in Table 5 is the intermol-
ecular N3H3-O1#1 interaction of PyTu2OMe, further
substantiating the lack of bifurcation in this molecule.
Previously [14], it was found that the most signi®-
cant difference between the pyridyl thioureas and the
previously studied thioureas (i.e. benzoyl etc.) that
have intramolecular hydrogen bonding, N3±H´´´O,
is the N2±C7 bond, which is shorter in the pyridyl
thioureas. In addition, the C7±S1 bond appears to
be marginally longer. Compared to N-benzoyl-N0-(4-
methoxyphenyl)thiourea, BzOTu4OMe [7],which has
its thiourea moiety bond angles listed in Table 6, the
same differences occur. For example, the average
N2±C7 and C7±S1 bond distances for the ®ve
Ê
thioureas of this study are 1.369(5) and 1.688(5) A
Ê
compared to 1.392(4) and 1.659(3) A for
BzOTu4OMe. Bond distances and angles for other
substituted thioureas are listed in Table 6 including
N-(2-pyridyl)-N0-phenylthiourea [2], and it appears
that the presence of the 2-methoxy group on the aryl
ring does not affect the bond distances and angles of
the thiourea moiety. Also, the thioureas in Table 6 that
do not possess intramolecular hydrogen bonding (i.e.
N,N0-diphenylthiourea, PhTuPh [9], and N-dimethyl-
N0-o-tolylthiourea, Me2Tu2T [11]) have even shorter
N2±C7 bond distances than the 2-pyridyl thioureas,
but there is no difference in the C7±S1 bond distances.
None of the bond angles listed in Table 6 seem to
follow a pattern except that the thioureas without
intramolecular hydrogen bonding have larger
N2±C7±S1 angles than the other thioureas.

102
D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
Fig. 6. Packing diagram for 4,6LuTu2OMe showing intermolecular and intramolecular hydrogen bonding.
Ê
Table 3
Selected bond distances (A) and angles (8) for PyTu2OMe, 4PicTu2OMe, 5PicTu2OMe, 6PicTu2OMe and 4,6LuTu2OMe
Compound
PyTu2Ome
4PicTu2OMe
5PicTu2OMe
6PicTu2OMea
4,6LuTu2OMe
Ê
Distances (A)
S1±C7
1.693(5)
1.320(6)
1.348(6)
1.409(7)
1.373(5)
1.330(5)
1.442(5)
1.363(5)
1.420(7)
1.674(7)
1.320(9)
1.33(1)
1.688(3)
1.328(3)
1.350(4)
1.409(3)
1.368(3)
1.337(3)
1.424(3)
1.361(3)
1.430(3)
1.687(4) 1.685(4)
1.331(5) 1.330(5)
1.352(5) 1.348(6)
1.404(5) 1.406(5)
1.377(5) 1.375(5)
1.330(5) 1.339(5)
1.425(5) 1.425(5)
1.364(5) 1.368(5)
1.410(6) 1.430(6)
1.697(3)
1.340(4)
1.360(4)
1.414(4)
1.354(4)
1.337(4)
1.400(4)
1.376(5)
1.428(6)
N1±C2
N1±C6
N2±C2
N2±C7
N3±C7
N3±C8
C9±O1
O1±C14
1.410(9)
1.375(9)
1.331(9)
1.435(9)
1.36(1)
1.42(2)
Angles (8)
C2±N2±C7
C7±N3±C8
N1±C2±N2
N2±C2±C3
S1±C7±N2
S1±C7±N3
N2±C7±N3
N3±C8±C9
N3±C8±C13
C8±C9±O1
C10±C9±O1
C9±O1±C14
129.1(4)
123.1(4)
119.3(4)
117.5(4)
117.4(3)
124.4(3)
118.2(4)
119.4(4)
120.8(4)
116.2(4)
124.3(4)
117.7(4)
130.1(7)
130.9(6)
118.7(7)
117.8(6)
117.0(5)
128.0(6)
114.9(7)
114.1(7)
125.9(7)
115.6(7)
124.9(7)
119.5(7)
130.1(2)
126.0(2)
119.2(2)
118.1(2)
118.2(2)
124.9(2)
116.8(2)
117.8(2)
122.2(2)
115.3(2)
124.9(2)
117.6(2)
130.1(3) 131.1(4)
128.4(3) 129.4(3)
118.8(4) 118.4(4)
117.8(4) 118.1(4)
118.3(3) 116.7(3)
125.7(3) 126.6(3)
116.0(4) 116.7(4)
115.7(3) 115.4(3)
123.6(4) 125.3(4)
115.1(4) 115.8(4)
125.1(4) 124.2(4)
118.8(4) 117.9(4)
130.7(3)
129.8(3)
117.4(3)
118.5(3)
117.3(3)
125.3(3)
117.4(3)
116.3(3)
125.0(3)
115.0(3)
124.8(4)
117.3(4)
a
The second column represents the analogous bonds in the S2 molecule.

D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
103
Table 4
Angles between mean planes of the various N-(2-pyridyl)-N0-(2-methoxyphenylthioureas) (plane A ˆ mean plane of pyridine ring, plane B ˆ
mean plane of the thiourea moiety, N±C(S)±N0 and plane C ˆ mean plane of the aromatic ring)
Compound
PyTu2OMe
Plane
Mean plane deviation
Atom with greatest deviation
Plane/plane
Angle (8)
N1±C2±C3±C4±C5±C6
N2±C7±S1±N3
0.0002(1)
0.0001(1)
0.0004(2)
C6, 0.0054(47)
C7, 0.0012(39)
C13, 0.0101(58)
A/B
B/C
C/A
3.2(3.8)
80.6(3.8)
80.8(3.5)
C8±C9±C10±C11±C12±C13
4PicTu2OMe
5PicTu2OMe
6PicTu2OMe
N1±C2±C3±C4±C5±C6
N2±C7±S1±N3
C8±C9±C10±C11±C12±C13
0.0001(1)
0.0013(6)
0.0001(1)
C3, 0.0102(68)
C7, 0.0090(67)
C13, 0.0098(75)
A/B
B/C
C/A
4.1(3.6)
14.5(3.7)
16.8(3.4)
N1±C2±C3±C4±C5±C6
N2±C7±S1±N3
0.0003(1)
0.0008(3)
0.0002(1)
C6, 0.0041(26)
C7, 0.0081(21)
C9, 0.0133(21)
A/B
B/C
C/A
4.9(3.9)
53.2(3.9)
48.9(3.5)
C8±C9±C10±C11±C12±C13
N1±C2±C3±C4±C5±C6
N2±C7±S1±N3
0.0003(1)
0.0011(5)
0.0002(1)
0.0004(2)
0.0014(6)
0.0001(1)
C2, 0.0071(39)
C7, 0.0085(39)
C11, 0.0126(53)
C26, 0.0062(52)
C27, 0.0128(42)
C28, 0.0194(38)
A/B
B/C
C/A
A/B
B/C
C/A
11.7(3.7)
39.5(3.7)
30.2(3.6)
6.7(3.6)
C8±C9±C10±C11±C12±C13
N21±C22±C23±C24±C25±C26
N22±C27±S21±N23
26.3(3.6)
19.9(3.5)
C28±C29±C30±C31±C32±C33
4,6LuTu2OMe
N1±C2±C3±C4±C5±C6
N2±C7±S1±N3
0.0002(1)
0.0012(5)
0.0001(1)
C3, 0.0025(32)
C7, 0.0097(30)
C8, 0.0115(30)
A/B
B/C
C/A
6.1(3.7)
33.3(3.7)
27.2(3.5)
C8±C9±-C10±C11±C12±C13
3.2. Spectral studies
The u.v. spectra (DMSO) of the six complexes have
a band at ca. 37000 cm21 due to p ! pp transitions
from the heterocyclic and aryl rings in agreement with
previous studies [15±17].
A second band in
the 33000 cm-1 region is assigned to n ! pp of the
heterocyclic ring and transitions associated with the
thiourea function. There are no signi®cant differences
in the spectra of the bifurcated and non-bifurcated
molecules.
1
The H NMR spectra show some variation in the
shift of the N3H resonance due to differences in the
intramolecular hydrogen bonding in these thioureas,
but there is no trend in the values as shown in Table 7.
For example, N0H is found at 13.871 ppm for the
bifurcated 4PicTu2OMe but at 13.803 ppm for
PyTu2OMe, which is not bifurcated. For N2H there
is also no difference in its chemical shift based on
whether bifurcation is present. Compared to
previously N-(2)-pyridyl-N0-arylthioureas, there is
not a signi®cant difference in the chemical shift of
N3H due to bifurcation or an electronic effect of the
2-methoxy group, for example: 4,6LuTu2OMe,
Fig. 7. Plot of the angle (8) between the mean planes of the pyridyl
Ê
and aryl rings versus the H´´´O and H´´´N distances (A) for the N-
pyridyl-N-(2-methoxy)-phenylthioureas. 1 ˆ 4PicTu2OMe; 2 ˆ
6PicTu2OMe; 3 ˆ 4;6 LuTu2OMe, 4 ˆ 5PicTu2OMe and 5 ˆ
PyTu2OMe: PyTu2OMe and 5PicTu2OMe do not show bifurcation,
4,6LuTu2OMe is weakly bifurcated and 6PicTu2OMe and
4PicTu2OMe are bifurcated.

104
D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
Table 5
Intramolecular and intermolecular hydrogen bond distances (A) and angles (8) for the various N(2-pyridyl)-N -arylthioureas (italics are used to
indicate that hydrogen bonding does not occur)
0
Ê
Ê
Bond distances (A)
Thiourea
D
A
D±H
Bond angle
H´´´A
D±H´´´A
/(D±H´´´A) (8)
Intramolecular
PyTu2Ome
N3
N3
N3
N3
O1
O1
O1
O1
0.964(4)
0.993(6)
0.983(2)
0.942(3)
0.955(3)
0.962(3)
0.964(4)
0.993(6)
0.983(2)
0.942(3)
0.955(3)
0.962(3)
3.000(4)
2.131(6)
2.494(2)
2.225(3)
2.148(3)
2.275(3)
1.853(4)
1.788(7)
1.856(2)
1.916(4)
1.905(4)
1.821(3)
2.687(5)
2.566(8)
2.641(3)
2.598(4)
2.605(4)
2.612(4)
2.668(5)
2.634(9)
2.662(3)
2.652(5)
2.681(5)
2.648(4)
62.1(3)
104.5(4)
87.6(2)
4PicTu2OMe
5PicTu2OMe
6PicTu2OMe
102.5(2)
107.9(2)
99.5(2)
4,6LuTu2OMe
PyTu2Ome
N3
N3
N3
N3
N3
O1
N1
N1
N1
N1
140.4(3)
141.0(4)
137.2(2)
133.2(2)
136.7(2)
142.1(2)
4PicTu2OMe
5PicTu2OMe
6PicTu2OMe
4,6LuTu2OMe
N3
N1
Intermolecular
PyTuPh
N2
N2
N2
N2
N2
N2
N2
S1
S1
S1
S1
S1
S1
S1
2.55(3)
3.412(3)
3.401(2)
3.348(3)
3.409(3)
3.470(6)
3.404(2)
3.421(3)
3.418(3)
3.436(3)
3.170(5)
163(2)
PyTu2T
2.45(2)
159(2)
4,6LuTu2T
PyTu2Ome
4PicTu2OMe
5PicTu2OMe
6PicTu2OMe
2.482(1)
2.546(1)
2.561(2)
2.4837(6)
2.499(1)
2.5154(10)
2.5156(9)
2.476(3)
158(2)
0.962(2)
0.961(6)
0.938(2)
0.930(3)
0.962(3)
0.937(3)
0.962(3)
149.5(2)
157.9(4)
167.0(2)
160.5(2)
163.7(2)
167.7(2)
128.7(2)
4,6LuTu2OMe
PyTu2Ome
N2
N3
S1
O1#1
14.030 ppm and 4,6LuTuPh, N-2 (4,6-lutidyl)-N0-
phenylthiourea, 14.119 ppm [16]. However, there is
variation in the chemical shift of N2H between the
present thioureas and the previously studied 2-pyridyl
thioureas [16]. The following examples represent the
di0fferences in the chemical shift of N2H: N-2-pyridyl-
N -phenylthiourea, 10.903 ppm [16]; N-2-pyridyl-N0-
2-tolylthiourea [16], 10.013 ppm, PyTu2OMe,
8.533 ppm. These differences suggest that substitution
on the aryl ring has a signi®cant effect on the chemical
shift on N2H. Earlier we indicated that the inductive
effect a methyl group in N-2-pyridyl-N0-tolylthioureas
enriches the electron density in the N2H bond, and
the more remote methyl groups on the phenyl ring
do so to a lesser extent [16]. The above data show
that a 2-methoxy group attached to the aryl ring
affects the chemical shift of N2H to a greater
extent, as would be expected due to its larger elec-
tronic effect.
4. Supplementary material
Crystallographic data (excluding structure
factors) for the structures reported in this paper
have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publica-
tion no. CCDC-1003/m. Copies of available
material can be obtained, free of charge, on appli-
cation to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK, (fax: 144-1223-336033 or e-mail:
deposit@ccdc.cam.ac.uk
Acknowledgements
Acknowledgement is made to the Donors of the
Petroleum Research Fund, administered by the Amer-
iScan Chemical Society for the partial support of this
research.

D.X. West et al. / Journal of Molecular Structure 562 (2001) 95±105
105
Table 6
Selected bond distances (A) and bond angles (8) for substituted thioureas
Ê
Ê
Bond distances (A)
Compound
Bond angles, (8)
Ref
N2±C7
S1±C7
N3±C7
N2±C7±N3
N2±C7±S1
N3±C7±S1
PyTu2OMe
1.373(5)
1.375(9)
1.368(3)
1.377(5)
1.375(5)
1.354(4)
1.392(4)
1.349(4)
1.356(4)
1.374(4)
1.370(4)
1.370(4)
1.693(5)
1.674(7)
1.688(3)
1.687(4)
1.685(4)
1.697(3)
1.659(3)
1.681(5)
1.693(3)
1.682(3)
1.678(3)
1.687(3)
1.330(5)
1.331(9)
1.337(3)
1.330(5)
1.339(5)
1.337(4)
1.329(4)
1.349(4)
1.337(4)
1.335(4)
1.336(4)
1.339(4)
118.2(4)
114.9(7)
116.8(2)
116.0(4)
116.7(4)
117.4(3)
115.4(3)
113.9(4)
115.6(3)
116.8(5)
116.9(4)
116.9(2)
117.4(3)
117.0(5)
118.2(2)
118.3(3)
116.7(3)
117.3(3)
119.2(2)
123.0(2)
121.5(3)
118.6(4)
119.7(4)
119.1(2)
124.4(3)
128.0(6)
124.9(2)
125.7(3)
126.6(3)
125.3(3)
125.4(2)
123.0(2)
122.9(2)
124.6(4)
123.4(4)
124.1(2)
This work
This work
This work
This work
4PicTu2OMe
5PiCTu2OMe
6PicTu2OMe
4,6LuTu2OMe
BzOTu4OMea
PhTuPhb
This work
[7]
[9]
Me2TuoTc
PyTuPhd
[11]
[2]
PyTuoTe
[15]
[17]
4,6LuTuoTf
N-benzoyl-N0-(4-methoxyphenyl)-thiourea.
N,N0-diphenylthiourea.
N-dimethyl-N0-o-tolylthiourea.
N-2-pyridyl-N0-phenyllthiourea.
N-2-pyridyl-N0-o-tolylthiourea.
N-2-(4,6-lutidyl)-N0-o-tolylthiourea.
a
b
c
d
e
f
Table 7
1H NMR spectral data (CDCl3) for the N-(2-pyridyl)-N0-2-methox-
[9] S.S.S. Raj, L. Puviarasan, D. Velmurugan, G. Jayanthi, H-K.
Fun, Acta Crystallogr. C55 (1999) 1318.
yphenylthioureas
[10] A. Ramnathan, K. Sivakumar, K. Subramanian, N. Janarthanan,
K. Ramadas, H.K. Fun, Acta Crystallogr. C51 (1995) 2446.
[11] A. Ramnathan, K. Sivakumar, K. Subramanian, D. Meerarani,
K. Ramadas, H-K. Fun, Acta Crystallogr. C52 (1996) 139.
[12] A. Ramnathan, K. Sivakumar, N. Janarthanan, D. Meerarani,
K. Ramadas, H-K. Fun, Acta Crystallogr. C52 (1996) 411.
[13] A. Ramnathan, K. Sivakumar, K. Subramanian, N. Srinivasan,
K. Ramadas, H-K. Fun, Acta Crystallogr. C52 (1996) 656.
[14] A. Ramnathan, K. Sivakumar, K. Subramanian, N.
Janarthanan, K. Ramadas, H-K. Fun, Acta Crystallogr. C51
(1995) 1627.
Compound
N3H
N2H
C6H
C4H
OCH3
3.928
PyTu2Ome
13.803 8.533
14.128 8.003
13.871 8.364
13.780 8.904
14.011 9.002
8.597
8.557
8.610
8.055
±
7.681(t)
3PicTu2OMe
4PicTu2OMe
5PicTu2OMe
6PicTu2OMe
7.520(d) 3.921
3.915
7.477(d) 3.910
±
7.541(t)
±
3.921
3.910
4,6LuTu2OMe 14.030 8.338
±
[15] D.X. West, C.A. Presto, A.K. Hermetet, K.D. Haslow, L.J.
Â
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