Structural and spectral studies of N-2-(4,6-lutidyl),N'-tolylthioureas

Article abstract of DOI:10.1016/S0022-2860(99)00314-2

N-2-(4,6-lutidyl)-N'-o-tolylthiourea, 4,6LuTuoT, triclinic, P-1, a = 7.470(2), b = 9.799(5), c = 10.269(3) ?, α = 90.514(4), β = 98.89(3), γ = 90.14(3)°, V = 742.5(9) ?³, Z = 2, μ = 2.09 mm^-1; N-2-(4,6-lutidyl)-N'- m-tolylthiourea, 4,6LuTumT, monoclinic, P2₁/a, a = 7.2393(2), b = 16.636(3), c = 12.557(1) ?, β = 101.968(9)°, V = 1479.4(6) ?³, Z = 4, μ=2.10mm^-1 and N-2-(4,6-lutidyl)-N'-p-tolylthiourea, 4,6LuTupT, triclinic, P-1, a=7.883(2), b=7.9024(8), c = 23.273(4) ?, α = 86.49(1), β = 86.48(2), γ = 88.45(2)°, V = 1443.9(7) ?³, Z = 4, μ = 2.15 mm^-1. These molecules have an intramolecular hydrogen bond between N'H and the pyridyl nitrogen, as well as intermolecular hydrogen bonding between NH and a thione sulfur of a second molecule to form centrosymmetric dimers. Solution ¹H NMR studies (CDCl₃) show the N'H resonance considerably downfield for each thiourea and its position, as well as that of NH, are affected by substituents on the phenyl ring. (C) 2000 Elsevier Science B.V.

Full text of DOI:10.1016/S0022-2860(99)00314-2

MOLSTR 11121
Journal of Molecular Structure 522 (2000) 27–36
www.elsevier.nl/locate/molstruc
Structural and spectral studies of
N-2-(4,6-lutidyl)-N0-tolylthioureas
*
D.X. West , J.K. Swearingen, A.K. Hermetet, L.J. Ackerman, C. Presto
Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA
Received 6 May 1999; accepted 21 June 1999
Abstract
N-2-(4,6-lutidyl)-N0-o-tolylthiourea, 4,6LuTuoT, triclinic, P-1, a ˆ 7:470ꢀ2†, b ˆ 9:799ꢀ5†, c ˆ 10:269ꢀ3† A,
ꢀ
ꢀ3
a ˆ 90:514ꢀ4†, b ˆ 98:89ꢀ3†, g ˆ 90:14ꢀ3†Њ, V ˆ 742:5ꢀ9† A , Z ˆ 2, m ˆ 2:09 mmϪ1; N-2-(4,6-lutidyl)-N0-m-tolylthiourea,
ꢀ
ꢀ3
4,6LuTumT, monoclinic, P21/a, a ˆ 7:2393ꢀ2†, b ˆ 16:636ꢀ3†, c ˆ 12:557ꢀ1† A, b ˆ 101:968ꢀ9†Њ, V ˆ 1479:4ꢀ6† A , Z ˆ 4,
m ˆ 2:10 mmϪ1 and N-2-(4,6-lutidyl)-N0-p-tolylthiourea, 4,6LuTupT, triclinic, P-1, a ˆ 7:883ꢀ2†, b ˆ 7:9024ꢀ8†,
c ˆ 23:273ꢀ4† A, a ˆ 86:49ꢀ1†, b ˆ 86:48ꢀ2†, g ˆ 88:45ꢀ2†Њ, V ˆ 1443:9ꢀ7† A , Z ˆ 4, m ˆ 2:15 mmϪ1. These molecules
have an intramolecular hydrogen bond between N0H and the pyridyl nitrogen, as well as intermolecular hydrogen bonding
between NH and a thione sulfur of a second molecule to form centrosymmetric dimers. Solution 1H NMR studies (CDCl3) show
the N0H resonance considerably downfield for each thiourea and its position, as well as that of NH, are affected by substituents
on the phenyl ring. ᭧ 2000 Elsevier Science B.V. All rights reserved.
ꢀ
ꢀ3
Keywords: Heterocyclic thioureas; Hydrogen bonding; Crystal structure
1. Introduction
intramolecular hydrogen bond between N0H and
oxygen (i.e. benzoyl, etc.) [5–10]. There is also a
weak intermolecular N2H hydrogen bond with a sulfur
of a neighboring molecule to form a two-dimensional
(2D) network in these latter thioureas. In addition,
crystal structures of substituted thioureas with intermo-
lecular hydrogen bonding, but without intramolecular
hydrogen bonding, have been reported [11–15].
More recent studies of substituted N-(2-pyridyl)-
N0-phenylthioureas including N-2-(4,6-lutidyl)-N0-
phenylthiourea, 4,6LuTuPh [16] and N-(2-pyridyl)-
N0-tolylthioureas have been reported [17]. Here we
report the crystal structures and lattice arrangements
for thioureas having methyl groups situated on both
the pyridyl ring (i.e. 4,6-lutidyl derivatives) and the
aromatic ring (i.e. tolyl derivatives), Fig. 1, which
possess both intramolecular and intermolecular
hydrogen bonding.
Although representative heterocyclic thioureas have
beenshowntobebiologicallypotentcompounds[1]and
several thiourea derivatives have been characterized as
prospective agents for antiviral chemotherapy [2], their
structures, and in particular, the various modes of
1
hydrogen bonding have received little attention. H
NMR correctly predicted intramolecular hydrogen
bonding between the pyridyl nitrogen and N0H in 2-
pyridyl thioureas [3], but only recently a structural
study has been reported for N-(2-pyridyl)-N0-
phenylthiourea [4]. Studies of a number of substituted
thioureas including N-benzoyl-N0-thioureas indicate an
* Corresponding author. Tel.: ϩ 1-309-438-7661; fax: ϩ 1-309-
438-5538.
E-mail address: dxwest@ilstu.edu (D.X. West).
0022-2860/00/$ - see front matter ᭧ 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(99)00314-2

28
D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
coordinates of the H atoms attached to N and N0 were
refined. Refinement of the structures was made by
full-matrix least-squares. Scattering factors are from
Wassmaire and Kirfel [18], calculations were done by
maXus, version 2.0 [19] and graphics are Platon for
Windows [20].
3. Results and discussion
3.1. Structural studies
The crystallographic data and methods of data
collection, solution and refinement for 4,6LuTuoT,
4,6LuTumT and 4,6LuTupT are shown in Table 1
and the atomic coordinates and equivalent isotropic
displacement coefficients are included in the depos-
ited material (CCDC), as are a complete list of bond
distances and angles. The CCDC(s are as follows:
4; 6LuTuoT ˆ 118 645, 4; 6LuTumT ˆ 118 646 and
4; 6LuTupT ˆ 118 655.
Fig. 1. A representation of a N-(4,6-lutidyl)-N0-tolylthiourea
showing expected intramolecular and intermolecular hydrogen
bonding.
2. Experimental
4,6-Dimethyl-2-aminopyridine was purchased from
Aldrich and used as received. It was mixed in a 1:1
molar ratio with o-tolyl-, m-tolyl- or p-tolylisothio-
cyanate (Aldrich) in 95% ethanol, and the resulting
mixture gently refluxed for a minimum of 1 h. On
cooling and slowly evaporating (35ЊC) the reactant
mixture, the thioureas crystallized from solution.
They were filtered, washed with cold isopropanol
followed by anhydrous ether, dried on a warm plate
and then stored until required for characterization.
The yields are ca. 65% for each of the thioureas and
the melting points are as follows: 4,6LuTuoT, 180–
182ЊC; 4,6LuTumT, 184–186ЊC; and 4,6LuTupT,
The molecular structures of the three 4,6-lutidyl
thioureas are represented by 4,6LuTumT in Fig. 2,
the intermolecular and intramolecular hydrogen
bonding by 4,6LuTuoT in Fig. 3 and the packing
common to the three by 4,6LuTupT in Fig. 4. All
three are in a conformation resulting from intramole-
cular hydrogen bonding of N0H to the pyridine
nitrogen, N1, in a manner similar to the benzoyl
thioureas and trans–cis like N-cyclohexyl-N0-
phenylthiourea [14]. Inspection of Table 2 shows
that the bond distances for the three 2-lutidyl thioureas
are generally within three orders of magnitude of their
estimated standard deviations. The largest difference
is found in the N3–C8 bonds as might be expected
because of the change in position of the methyl group
on the aromatic ring. The bond angles do show some
variation; the angles involving the tolyl ring bonding
to N3 show the greatest variation. For example, C7–
N3–C8 is 125.6(2), 128.7(3) and averages 133.1(3)Њ
for 4,6LuTuoT, 4,6LuTumT and 4,6LuTupT, respec-
tively. Thus, the position (i.e. ortho, meta or para) of
the methyl group on the aryl ring has an effect on the
bonding of the thiourea moiety in these lutidyl
derivatives, but an effect of this magnitude was not
found for the N-(2-pyridyl)-N0-tolyl thioureas [17].
Table 3 shows bond distances and angles for
4,6LuTuoT, 4,6LuTumT and 4,6LuTupT along with
1
202–204ЊC. Their H NMR spectra were recorded
in CDCl3 with a Varian Gemini 2000 300 MHz spec-
trometer. IR spectra were recorded as nujol mulls
between NaCl plates with a Nicolet 5SCX FT Spec-
trometer and UV spectra with a Cary 5E spectro-
photometer 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. The struc-
tures were solved with direct methods and missing
atoms were found by difference-Fourier synthesis.
All non-hydrogen atoms were refined with anisotropic
temperature factors and all hydrogens were found on
the difference Fourier map. The H atoms of CH were
allowed to ride on the C atoms and assigned fixed
ꢀ2
isotropic temperature factor, U ˆ 0:05 A . Only the

D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
29
Table 1
Crystallographic data and methods of data collection, solution and refinement for 4,6LuTuoT, 4,6LuTumT and 4,6LuTupT
4,6LuTuoT
4,6LuTumT
4,6LuTupT
Crystal data
Empirical formula
Crystal color, habit
Crystal size (mm)
Crystal system
Space group
C15H17N3S
Colorless, prism
0:32 × 0:28 × 0:20
Triclinic
P-1
7.470(2)
9.799(5)
10.269(3)
90.514(4)
98.89(3)
90.14(3)
742.5(9)
2
C15H17N3S
Colorless, prism
0:30 × 0:26 × 0:18
Monoclinic
P21=a
7.2393(8)
16.636(3)
12.557(1)
90(0)
101.968(9)
90(0)
1479.4(6)
4
C15H17N3S
Colorless, prism
0:40 × 0:14 × 0:12
Triclinic
P-1
7.883(2)
7.9024(8)
23.273(4)
86.49(1)
86.48(2)
88.45(2)
1443.9(7)
4
˚
a (A)
˚
b (A)
˚
c (A)
a (Њ)
b (Њ)
g (Њ)
3
˚
V (A )
Z
Formula weight
Density (calcd.) (g/cm3)
Absorption coefficient (mmϪ1
F(000)
271.4
1.214
2.09
288
271.4
1.219
2.10
576
271.4
1.248
2.15
576
)
Data collection
Diffractometer
Radiation (wavelength, A)
Temperature (K)
Monochromator
2u range (Њ)
Nonius Mach 3
MoKa (0.70930)
293
Highly oriented graphite crystal
2.0–55.0
Nonius Mach 3
MoKa (0.70930)
293
Highly oriented graphite crystal
2.0–55.0
Nonius Mach 3
MoKa (0.70930)
293
Highly oriented graphite crystal
2.0–55.0
˚
Scan type
v/u
v/u
v/u
Scan range (v,Њ)
Index ranges
0.80
0 Յ h Յ 9
0.80
0 Յ h Յ 9
0.80
0 Յ h Յ 10
Ϫ10 Յ k Յ 10
Ϫ30 Յ l Յ 30
7387
7089 (3.096)
4577 (I Ͼ 3:0sꢀI†)
c-Scan
Ϫ12 Յ k Յ 12
Ϫ13 Յ l Յ 13
3811
3673 (2.29)
2983 (I Ͼ 3:0sꢀI†)
c-Scan
0 Յ k Յ 21
Ϫ16 Յ l Յ 16
3934
3658 (1.77)
2644 (I Ͼ 3:0sꢀI†)
c-Scan
Reflections collected
Ind. Reflec.(Rint %)
Observed reflections
Absorption correction
Maximum and minimum
transmissions
1.000 and 0.984
1.000 and 0.956
1.000 and 0.966
Solution and refinement
Solution method
Goodness-of-fit
Direct methods
0.578
Direct methods
1.076
Direct methods
0.915
Data/parameter ratio
Largest diff. Peak (eA
Largest diff. Hole (eA
R
16.8:1
0.60
Ϫ 0.24
0.045
15.4:1
0.50
Ϫ 0.31
0.051
13.3:1
0.31
Ϫ 0.37
0.052
Ϫ3
˚
˚
)
)
Ϫ3
vR
0.094
maXus
0.1881
maXus
0.1038
maXus
Programs used
…
other 2-pyridylthioureas, and includes representative
N,N0-substituted thioureas that do not have intramole-
cular hydrogen bonding [11–15]. Previously [16], it
was found that the only significant differences
between the pyridyl thioureas and the previously
studied thioureas (i.e. benzoyl, etc.) that have
intramolecular hydrogen bonding, N3–H O is that
the pyridyl thioureas have shorter N2–C7 bonds and
the C7–S1 bond is marginally longer. Since the 2-
pyridyl thioureas do not have an electron withdrawing
carbonyl group attached to N, the N–C7 bond has
slightly more double bond character. Also, there is

30
D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
Fig. 2. A perspective view of 4,6LuTumT showing intramolecular hydrogen bonding.
Fig. 3. A perspective view of 4,6LuTuoT showing both intramolecular and intermolecular hydrogen bonding and the molecule’s lack of
planarity.

D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
31
Fig. 4. A unit cell of 4,6LuTupT showing the mode of packing of the dimers, both intramolecular and intermolecular hydrogen bonding and the
molecule’s nearly planar structure.
no significant difference in the thiourea moiety’s bond
angles between the present thioureas and those
previously studied [5–9]. In general, the two thioureas
Table 2
included in Table 3 that have only intermolecular
hydrogen bonding, PhTuPh [11] and Me2TuoT [13],
show the following differences from thioureas with
intramolecular hydrogen bonding: the N–C7 bond is
shorter, N–C7–S1 angle larger and the N0 –C7–S1
angle smaller. There are no significant differences in
the bond distances and angles among the nine 2-
pyridyl thioureas shown in Table 3.
˚
Selected bond distances (A) and angles (Њ) for 4,6LuTuoT,
4,6LuTumT and 4,6LuTupT
4,6LuTuoT
4,6LuTumT 4,6LuTupTa
˚
Bond distances (A)
S1–C7
N1–C2
N1–C6
N2–C2
N2–C7
N3–C7
N3–C8
Bond angles (Њ)
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
1.687(3)
1.337(3)
1.349(3)
1.402(4)
1.370(4)
1.339(4)
1.436(4)
1.691(4)
1.337(4)
1.360(4)
1.411(4)
1.374(5)
1.339(5)
1.431(5)
1.686(4) 1.690(4)
1.334(5) 1.335(5)
1.353(5) 1.350(5)
1.408(5) 1.415(5)
1.382(5) 1.364(5)
1.332(5) 1.344(5)
1.421(5) 1.413(5)
Shown in Table 4 are the three hydrogen bonding
interactions found for the 2-pyridyl thioureas. The
…
intramolecular N3–H3 N1 hydrogen bonding
…
shows a wide range of non-bonding N3–H3 N1
129.2(3)
125.6(2)
129.8(3)
129.7(3) 130.1(3)
132.9(3) 133.4(3)
118.2(3) 118.0(3)
118.4(3) 118.6(3)
117.5(3) 118.0(3)
127.1(3) 126.3(3)
115.4(3) 115.8(3)
114.7(3) 115.0(3)
126.5(4) 126.2(4)
distances. For unsubstituted PyTuPh this distance is
128.7(3)
118.3(3)
117.9(3)
118.3(3)
125.6(3)
116.2(3)
121.8(4)
116.6(4)
˚
2.646(4) A, but substitution on the pyridyl ring
118.4(3)
118.3(3)
119.1(2)
124.1(2)
116.9(2)
118.6(3)
119.8(3)
strengthens this bonding, reducing the distance to an
average of 2.608(4) for the two forms of 4,6LuTupT
˚
and to 2.626(4) and 2.629(4) A for 4,6LuTumT and
4,6LuTuPh, respectively. However, ortho substitution
on the aryl ring weakens this interaction so that
…
N3–H3 N1 distance of
2.667(3) A and PyTuoT, a distance of 2.687(4) A.
An even longer distance (average of the two forms)
4,6LuTuoT has
a
a The second values represent the analogous bonds in the second
molecule.
˚
˚

32
D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
Table 3
˚
Selected bond distances (A) and bond angles (Њ) for substituted thioureas
˚
Compound
Bond distances (A)
Bond angles (Њ)
Reference
N2–C7
S1–C7
N3–C7
N2–C7–N3
N2–C7–S1
N3–C7–S1
BzOTupNO2Pha
BzOTupMeOPhb
PhTuPhc
1.393(3)
1.392(4)
1.349(4)
1.356(4)
1.374(4)
1.370(4)
1.377(3)
1.373(3)
1.373(4)
1.378(6)
1.375(4)
1.366(4)
1.370(4)
1.374(5)
1.382(5)
1.364(5)
1.658(2)
1.659(3)
1.681(5)
1.693(3)
1.682(3)
1.678(3)
1.684(2)
1.684(2)
1.684(4)
1.672(4)
1.679(3)
1.689(3)
1.687(3)
1.691(4)
1.686(4)
1.690(4)
1.344(3)
1.329(4)
1.349(4)
1.337(4)
1.335(4)
1.336(4)
1.331(3)
1.334(3)
1.324(6)
1.354(6)
1.333(4)
1.341(4)
1.339(4)
1.339(5)
1.332(5)
1.344(5)
115.0(2)
115.4(3)
113.9(4)
115.6(3)
116.8(5)
116.9(4)
116.7(2)
117.9(2)
116.0(3)
116.4(7)
115.8(5)
115.5(2)
116.9(2)
116.2(3)
115.4(3)
115.8(3)
118.3(2)
119.2(2)
123.0(2)
121.5(3)
118.6(4)
119.7(4)
118.8(2)
118.4(2)
118.6(3)
119.0(6)
117.3(4)
117.6(2)
119.1(2)
118.3(3)
117.5(3)
118.0(3)
126.6(2)
125.4(2)
123.0(2)
122.9(2)
124.6(4)
123.4(4)
123.5(2)
123.7(2)
125.4(2)
124.5(6)
126.9(4)
126.9(2)
124.1(2)
125.6(3)
127.1(3)
126.3(3)
[6]
[7]
[9]
[11]
[2]
Me2TuoTd
PyTuPhe
PyTuoTf
[15]
[15]
PyTumTg
PyTupTh
[15]
[14]
6PiTuPhi
4,6LuTuPhj
4,6LuTuoT
4,6LuTumT
4,6LuTupT
[14]
k
k
k
a N-benzoyl-N0-(4-nitrophenyl)thiourea.
b N-benzoyl-N0-(4-methoxyphenyl)-thiourea.
c N,N0-diphenylthiourea.
d N-dimethyl-N0-o-tolylthiourea.
e N-(2-pyridyl)-N0-phenylthiourea.
f N-2-pyridyl-N0-o-tolylthiourea.
g N-2-pyridyl-N0-m-tolylthiourea.
h N-2-pyridyl-N0-p-tolylthiourea.
i N-6-methyl-2-pyridyl-N0-phenylthiourea.
j N-4,6-dimethyl-2-pyridyl-N0-phenylthiourea.
k This work.
˚
has been found for PyTumT, 2.698(3) A. Similar
results in centrosymmetric dimer formation. The
…
…
N2–H2 SA non-bonding distance for PyTuPh is
variation occurs in the H3 N1 distances shown in
Table 4. The N3–H3 N1 bond angles range from
…
˚
3.412(3) A and shorter distances are found for
˚
˚
an average of 132(2)Њ for PyTumT to 150(3) for
4,6LuTuPh. Therefore, substitution in the 4-position
of the pyridyl ring strengthens this intramolecular
hydrogen bonding and substitution in the 6-position
of the pyridyl ring has little effect since 6-PiTuPh and
PyTuoT, 3.401(2) A and 4,6LuTuoT, 3.348(3) A, as
˚
well as 6PiTuPh, 3.383(3) A. Therefore, substitution
on the aryl ring strengthens this interaction, and
substitution on the pyridyl ring strengthens it to an
even greater extent. Weakening this intermolecular
interaction is substitution at the para-position of the
aryl ring since PyTupT and 4,6LuTupT have average
…
PyTuPh have similar N3–H3 N1 distances. Substi-
tution on the para-position of the aryl ring also
strengthens this bonding, but substituting the ortho-
and meta-positions weakens intramolecular hydrogen
bonding.
…
non-bonding N2–H2 SA distances of 3.437(4) and
˚
3.474(3) A, respectively. The bond angles range from
an average of 156(2)Њ for PyTumT to 169(4)Њ for
As was found for N-benzoyl-N0-(4-methoxyphe-
nyl)thiourea [10], N2H in the present thioureas and
the previously studied 2-pyridyl thioureas [4,16,17] is
involved in intermolecular hydrogen bonding with a
sulfur from a neighboring molecule, Table 4. This
PyTupT.
…
In addition to the N–H S hydrogen bond, the
thioureas’ sulfur is also interacting with a pyridyl
hydrogen, C3H. The non-bonding distances and
…
angles are also included in Table 3. The C3–H
S

D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
33
Table 4
Intramolecular and intermolecular hydrogen bond distances (A) and angles (Њ) for the various N(2-pyridyl)-N -arylthioureas
0
˚
…
˚
…
˚
…
Thiourea
H3 N1 (A)
N3-H3 N1 (A)
ЄN3–H3 N1 (Њ)
Intramolecular
PyTuPh
1.96(3)
2.646(4)
133(2)
PyTuoT
1.944(4)
2.687(4)
140(3)
PyTumT
PyTupT
6PiTuPh
2.262(2) 1.941(2)
1.93(4) 1.95(4)
1.82(3)
2.701(3) 2.696(3)
2.646(4) 2.665(4)
2.645(4)
129(2) 134(2)
140(5) 137(3)
144(2)
4,6LuTuPh
4,6LuTuoT
4,6LuTumT
4,6LuTupT
Intermolecular
1.76(4)
1.896(2)
1.840(3)
1.784(3) 1.801(3)
2.629(4)
2.667(3)
2.626(4)
2.605(4) 2.611(4)
150(3)
141(2)
143(2)
148(2) 146(2)
…
˚
…
˚
…
H2 SA (A)
2.55(3)
N2–H2 SA (A)
3.412(3)
ЄN2–H2 SA (Њ)
163(2)
PyTuPh
PyTuoT
2.45(2)
3.401(2)
159(2)
PyTumT
PyTupT
6PiTuPh
2.51(1) 2.49(1)
2.47(5) 2.68(5)
2.45(3)
3.407(2) 3.380(3)
3.352(4) 3.523(4)
3.383(3)
157(2) 155(2)
167(4) 171(4)
168(2)
4,6LuTuPh
4,6LuTuoT
4,6LuTumT
4,6LuTupT
2.66(4)
2.482(1)
2.534(1)
3.461(2)
3.348(3)
3.428(3)
165(3)
158.0(2)
165.8(2)
166.4(2) 158.3(2)
ЄC3–H SA (Њ)
146
2.573(1) 2.612(1)
3.469(3) 3.480(3)
…
˚
…
˚
…
C3H SA (A)
2.81
C3–H SA (A)
3.643(4)
PyTuPh
PyTuoT
2.84
3.619(3)
138
PyTumT
PyTupT
6PiTuPh
2.78 2.84
2.70 2.96
2.85
3.566(3) 3.643(3)
3.528(5) 3.801(5)
3.656(3)
140 142
146 147
142
4,6LuTuPh
4,6LuTuoT
4,6LuTumT
4,6LuTupT
2.89
2.98
2.96
2.81 2.82
3.706(3)
3.660(3)
3.724(4)
3.643(4) 3.650(4)
143
129
138
145 146
Table 5
Angles between mean planes of the various N-(2-pyridyl)-N0-arylthioureasa
Compound
Єplane A/plane B
Єplane B/plane C
Єplane A/plane C
PyTuPh
5.4(1)
58.0(1)
63.2(1)
PyTuoT
13.6(2)
75.5(1)
67.4(1)
PyTumT
PyTupT
6PiTuPh
4.6(1) 2.08(4)
10.2(1) 2.1(1)
3.89(3)
76.1(1) 77.2(1)
55.5(1) 56.5(1)
11.17(6)
80.2(1) 78.6(1)
58.8(1) 58.6(1)
11.2(7)
4,6LuTuPh
4,6LuTuoT
4,6LuTumT
4,6LuTupT
4.66(3)
19.2(4)
4.9(4)
3.1(4) 3.3(4)
13.23(6)
68.0(4)
46.7(4)
16.7(4) 16.7(4)
13.9(9)
64.1(3)
45.2(3)
18.3(3) 18.3(3)
a Plane A: mean plane of pyridine ring, plane B: mean plane of the thiourea moiety, N–C(S)–N0 and plane C: mean plane of the aromatic ring.

34
D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
Table 6
1H, 13C NMR (d), ultraviolet and infrared spectral date for N-(2-pyridyl)-N0-arylthioureas
Compound
PyTuPha
N0 H
NH
CyS
p ! pء
n ! pء
n(CyS)
n(NH)
Reference
[14]
13.865
10.903
178.7
37040
32900
(4.429)
32890
(4.358)
32350
(4.382)
32890
(4.391)
32470
(4.468)
32680
(4.443)
32790
(4.488)
32670
(4.468)
32670
(4.497)
857 m
3195 m
(4.298)b
37040
PyTuoT
13.494
13.644
13.771
14.103
14.119
13.689
14.052
14.067
10.013
9.401
10.031
9.205
8.311
9.318
8.731
9.159
179.3
178.7
178.8
178.0
178.1
179.3
178.4
178.4
850 m
831 m
818 m
850 m
828 m
845 s
3200 m
3185 m
3200 m
3197 m
3205 m
3172 sh
3200 m
3214 m
[15]
[15]
[15]
[14]
(4.226)
33980 sh
PyTumT
PyTupT
37040
(4.278)
37040
(4.319)
37040
(4.264)
34590 sh
6MTuPhc
4,6MTuPhd
4,6MTuoT
4,6MTumT
4,6MTupT
[14]
e
e
e
34470 sh
34470 sh
831 m
818 m
a N-2-pyridyl-N0-phenylthiourea.
b log e.
c N-6-methyl-2-pyridyl-N0-phenylthiourea.
d N-4,6-dimethyl-2-pyridyl-N0-phenylthiourea.
e This work.
˚
…
distance for PhTuPy is 3.643(4) A and substitution on
the pyridyl ring weakens this interaction (e.g.
has the shortest N2–H2 SA non-bonding distance
and the largest pyridyl ring/thiourea moiety dihedral
angle, 19.2(4)Њ this angle averages 3.2(4)Њ for
4,6LuTupT, which has one of the longer N2–
˚
˚
6PiTuPh, 3.656(3) A and 4,6LuTuPh, 3.706(3) A),
but substitution on the aryl ring appears to strengthen
this bonding (e.g. PyTuoT, 3.619(3) A). The non-
bonding C3–H S angles range from 129 to 146Њ.
Each of the 4,6-lutidyl thioureas has a very planar
thiourea moiety with no atom deviating from the
˚
…
H2 SA distances. When all three angles are consid-
ered, 6PiTuPh has the most planar structure and
…
features about average N3–H3 N1, somewhat
shorter N2–H2 SA and longer C3–H SA non-
bonding distances.
…
…
…
˚
plane by more than 0.0040 A. Table 5 lists the dihe-
dral angles between the pyridyl ring and the thiourea
moiety planes, the thiourea moiety and the aryl ring
planes and the pyridyl and aryl ring planes. The angles
between the planes should be useful in interpreting the
differences in the hydrogen bonding interactions
discussed earlier. For the intramolecular hydrogen
Although the bond distances and angles among the
nine 2-pyridyl thioureas studied to date do not show
significant variation, the distances and angles
involved in the three hydrogen bonding interactions
do have considerable variation. The dihedral angles
between the mean plane of the thiourea moiety and the
pyridyl and aryl mean planes result from differences
in solid state packing due to the various positions of
the methyl groups on the two rings.
…
bond, N3–H3 N1, the dihedral angle between the
pyridyl and aryl ring planes reflects the strongest
and weakest bonding. That is, 4,6LuTupT, which
…
has the shortest N3–H3 N1 distance, has an
pyridyl/aryl ring angle of 18.3(3)Њ for its two forms
and PyTumT, which has the longest N3–H3 N1
3.2. Spectral studies
…
distance, has an angle of 79.4(1)Њ. The pyridyl ring/
thiourea bond angles show a similar trend. 4,6LuTuoT
The UV spectra (DMSO) show a single band with a
high energy shoulder for 4,6LuTuoT, 4,6LuTumT and

D.X. West et al. / Journal of Molecular Structure 522 (2000) 27–36
35
4,6LuTupT, and one or two bands for the six other 2-
pyridyl thioureas reported previously [16,17], (Table
6) which we assign to a combination of p ! pء tran-
sitions from both rings and an n ! pء of the hetero-
cyclic ring. Other bands involving the thiourea
function are evidently obscured by this latter band.
In the infrared spectra of 4,6LuTuoT, 4,6LuTumT
and 4,6LuTupT, n(N2H) is assigned to a medium
intensity absorption band at ca. 3200 cmϪ1 and
n(CS) to bands between 800 and 860 cmϪ1 range in
agreement with the six previously studied thiosemi-
carbazones [16,17].
m. Copies of available material can be obtained, free
of charge, on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK, fax: ϩ 44-1223-336033 or
e-mail: deposit@ccdc.cam.ac.uk
Acknowledgements
Acknowledgement is made to the Donors of the
Petroleum Research Fund, administered by the
American Chemical Society, the National Science
Foundation and the Consejo Nacional de Ciencia y
Tecnologia for the partial support of this research.
1
The H NMR spectra show some variation in the
shift of the N3H resonance due to differences in the
intramolecular hydrogen bonding in the nine pyridyl
thioureas studied to date. Addition of methyl groups
to the pyridyl ring provides greater electron density to
the pyridine nitrogen causing a downfield shift for the
resonance of N3H. In contrast, the o-methyl group in
PyTuoT and 4,6LuTuoT weakens the intramolecular
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