Structural and spectral studies of N-(2-pyridyl)-N'-tolylthioureas

Article abstract of DOI:10.1016/S0022-2860(98)00746-7

N-(2-pyridyl)-N'-o-tolylthiourea, monoclinic, P2₁/c, a = 5,127(1), b = 19.854(2), c = 12.077(2), A, β = 94.96(1)°, V = 1224,7(2) A³, Z = 4, μ = 2.177 mm^-1, N-(2-pyridyl)-N'-m-tolylthiourea, triclinic, P - 1, a = 9.811(2),

Full text of DOI:10.1016/S0022-2860(98)00746-7

Journal of Molecular Structure 478 (1999) 219–226
Structural and spectral studies of N-(2-pyridyl)-N0-tolylthioureas
a
a
b,
*
´
´
´
`
´
Jesus Valdes-Martınez , Simon Hernandez-Ortega , Douglas X. West ,
Lily J. Ackermanb, John K. Swearingenb, Anne K. Hermetetb
a
´
´
´
´
Instituto de Quımica, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Coyoacan 04510, Mexico
bDepartment of Chemistry, Illinois State University, Normal, IL 61790-4160, USA
Dedicated with best wishes to Professor Gottfried Heinisch on the occasion of his 60th birthday
Received 13 August 1998; accepted 19 October 1998
Abstract
N-(2-pyridyl)-N0-o-tolylthiourea, monoclinic, P21/c, a ˆ 5:127ꢀ1†, b ˆ 19:854ꢀ2†, c ˆ 12:077ꢀ2† A, b ˆ 94:96ꢀ1†Њ,
ꢀ
ꢀ 3
V ˆ 1224:7ꢀ2† A , Z ˆ 4, m ˆ 2:177 mmϪ1, N-(2-pyridyl)-N0-m-tolylthiourea, triclinic, P Ϫ 1, a ˆ 9:811ꢀ2†, b ˆ 9:887ꢀ4†,
Ϫ1
ꢀ
ꢀ
c ˆ 13:595ꢀ3† A, a ˆ 74:91ꢀ3†, b ˆ 83:58ꢀ2†, g ˆ 76:27ꢀ2†Њ, V ˆ 1235:ꢀ7† A, Z ˆ 4, m ˆ 2:469 mm and N-(2-pyridyl)-
0
ꢀ
N -p-tolylthiourea, triclinic,P Ϫ 1, a ˆ 9:935ꢀ2†, b ˆ 11:488ꢀ2†, c ˆ 12:569ꢀ2† A, a ˆ 63:91ꢀ2†, b ˆ 88:60ꢀ2†, g ˆ 75:04ꢀ2†Њ,
V ˆ 1238:1ꢀ2† A , Z ˆ 4, m ˆ 2:154 mm all have an intramolecular hydrogen bond between N0H and the pyridyl nitrogen,
ꢀ 3
Ϫ1
as well as intermolecular hydrogen bonding between NH and a thione sulfur of a second molecule to form centrosymmetric
dimers. Solution H NMR studies (CDCI3) show the N0H resonance considerably downfield for each thiourea and its position,
1
as well as that of NH, are affected by substituents on the phenyl ring. ᭧ 1999 Elsevier Science B.V. All rights reserved.
Keywords: Heterocyclic thioureas; Hydrogen bonding; Crystal structure
1. Introduction
structures of substituted thioureas lacking intramole-
cular hydrogen bonding, but studying the intermole-
cular hydrogen bonding between an N–H and a sulfur
in a neighboring molecule [9–13]. A more recent
study of substituted N-(2-pyridyl)-N0-phenylthioureas
involves methyl substituents on the pyridyl ring (i.e.,
picolyl and lutidyl derivatives) [14]. Here we report
the crystal structures and lattice arrangements for
thioureas having methyl groups situated on the
aromatic ring (i.e., tolyl derivatives), Fig. 1, which
possess both intramolecular and intermolecular
hydrogen bonding.
Although 1H NMR has correctly predicted intramo-
lecular hydrogen bonding between the pyridyl
nitrogen and N0H [1], only recently has a structural
study been reported concerning N-(2-pyridyl)-N0-
phenylthiourea [2]. Studies of a number of N-
benzoyl-N0-thioureas have shown them to be in the
thioamidic form and to possess an intramolecular
hydrogen bond between N0H and the benzoyl oxygen
[3–8]. There is also a weak intermolecular N2H
hydrogen bond with a sulfur of a neighboring mole-
cule to form a two-dimensional network in these latter
thioureas. In addition, there are reports of crystal
2. Experimental
* Corresponding author. Tel.: 00 1 309 438 7661; Fax: 00 1 309
438 5538; e-mail: dxwest@ilstu.edu
2-aminopyridine was purchased from Aldrich and
0022-2860/99/$ - see front matter ᭧ 1999 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(98)00746-7

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J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
220
SHELXTL PCTM program package [15]. Scattering
factors for
N-(2-pyridyl)-N0-m-tolylthiourea,
PyTumT, are from Wassmaire and Kirfel [16], and
calculations were done by maXus, version 2.0 [17].
3. Results and discussion
3.1. Structural studies
The crystallographic data and methods of data
collection, solution and refinement for PyTuoT,
PyTumT and PyTupT are shown in Table 1 and the
atomic coordinates and equivalent isotropic displace-
ment coefficients are included in the deposited mate-
rial (CCDC), as are a complete list of bond distances
and angles. The CCDC#s are as follows:
Fig. 1. A representation of a N-(2-pyridyl)-N0-tolylthiourea
showing expected intra-and intermolecular bonding.
used as received. It was mixed in a 1 : 1 molar ratio
with o-tolyl-, m-tolyl-, or p-tolylisothiocyanate
(Aldrich) in anhydrous 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: PyTuoT, 183Њ–
185Њ; PyTumT, 167Њ–169Њ; and PyTupT, 183Њ–185Њ.
The NMR spectra were recorded in d6-DMSO with a
Varian Gemini 2000 300 MHz spectrometer. Infrared
and ultraviolet spectra were recorded with Perkin–
Elmer 783 and Hewlett Packard 8452 A Diode
Array spectrophotometers, respectively.
PyTuoT ˆ 102612,
PyTumT ˆ 102611
and
PyTupT ˆ 102613.
The molecular structures of the three thioureas are
shown in Figs. 2–4.,, All three are in a conformation
resulting from intramolecular hydrogen bonding of
the N0H to the pyridine nitrogen, N1, in a manner
similar to the benzoyl thioureas and ‘‘trans–cis’’
like N-cyclohexyl-N0-phenylthiourea [12]. Inspection
of Table 2 shows that the bond distances and bond
angles for the three 2-pyridyl thiureas are within three
orders of magnitude of the estimated standard devia-
tions. Thus, the position (i.e., ortho, meta or para) of
the methyl group on the aryl ring has no significant
effect on the bond distances and angles of the thiourea
moiety.
Colorless, prismatic crystals of the thioureas were
grown by slow evaporation of anhydrous ethanolic
solutions (filtrates) 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
Table 3 shows bond distances and angles for
PyTuoT, PyTumT and PyTupT along with other
thioureas having a functional group able to accommo-
date a similar intramolecular hydrogen bond, as well
as representative N,N0-substituted thioureas that do
not have intramolecular hydrogen bonding [9–13].
The only significant differences between the pyridyl
thioureas and the previously studied intramoleculary
hydrogen bonded thioureas is that the pyridyl
thioureas have shorter N–C7 bonds and their C7–S1
bond is marginally longer. There is essentially no
difference in the N0 –C7 bonds as would be expected
as both groups of thioureas have aromatic rings
attached to N0. The pyridyl thioureas do not have
the electron withdrawing carbonyl group attached to
N, which apparently allows the N–C7 bond to have
ꢀ 2
isotroic temperature factor, U ˆ 0:06 A . Only the
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 for
N-(2-pyridyl)-N0-o-tolylthiourea, PyTuoT, and N-(2-
pyridyl)-N0-p-tolylthiourea, PyTupT, were taken from
International Tables for X-ray Crystallography (1974,
Vol. IV), and all calculations were done with the

´
´
J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
221
Table 1
Crystallographic data and methods of data collection, solution and refinement for PyTuoT and PyTupT
Crystal Data
PyTuoT
PyTumT
PyTupT
Empirical Formula
Crystal Color, Habit
Crystal Size (mm)
Crystal System
C13H13N3S
Colorless, prism
0:32 × 0:28 × 0:20
Monoclinic
P21/c
5.127(1)
19.854(2)
12.077(2)
90(0)
94.96(1)
90(0)
1224.7(2)
4
C13H13N3S
Colorless, prism
0:30 × 0:26 × 0:18
Triclinic
P Ϫ 1
9.811(2)
9.887(4)
13.595(3)
74.91(3)
83.58(2)
76.27(2)
1235.2(7)
4
C13H13N3S
Colorless, prism
0:40 × 0:14 × 0:12
Triclinic
P Ϫ 1
9.935(2)
11.488(2)
12.569(2)
63.91(2)
88.60(2)
75.04(2)
1238.1(2)
4
Space Group
˚
a, A
˚
b, A
˚
c, A
a, Њ
b,Њ
l,Њ
3
˚
Volume, A
Z
Formula weight
Density (calcd.), g/cm3
Absorp. coeff., mmϪ1
F(000)
243.3
1.320
2.177
512
243.3
1.30
2.469
512
243.3
1.305
2.154
512
Data Collection
Diffractometer
Radiation, (wavelength)
Temperature (K)
Monochrometer
2u range
Siemens P4/PC
CuKa, (1.54178 A)
293
Highly oriented graphite crystal
3.0Њ–110.0Њ
u/20
Nonius Mach 3
MoKa, (0.70930 A)
293
Highly oriented graphite crystal
2.0Њ–55.0Њ
v/u
Siemens P4/F
CuKa, (1.54178 A)
293
Highly oriented graphite crystal
3.0Њ–110.0Њ
u/2u
˚
˚
˚
Scan type
Scan range (v)
Index ranges
0.70Њ
0 Յ h Յ 5
0.80Њ
0.84Њ
0 Յ h Յ 5
0 Յ h Յ 21
Ϫ13 Յ l Յ 12
3349
3133 (2.56 %)
2672 {F Ͼ 3:0sꢀF†}
Face-indexed
Numerical
0 Յ h Յ 12
Ϫ12 Յ k Յ 12
Ϫ17 Յ l Յ 17
6280
5654 (2.56 %)
2672 {l Ͼ 3:0sꢀl†}
0 Յ k Յ 21
Ϫ12 Յ l Յ 12
1641
1440 (2.7 %)
1299 {F Ͼ 4:0sꢀF†}
Face-indexed
Numerical
Reflections collected
Ind. reflec. (Rint)
Observed reflections
Absorption correction
Max. and min. transmissions
Solution and refinement
Solution method
C-scan
0.999 and 0.929
0.8232 and 0.6625
0.7496 and 0.5428
Direct methods
1.34
Direct methods
2.741
Direct methods
1.30
Goodness-of-Fit
Data/parameter ratio
8.1 : 1
0.30
Ϫ0.36
12.6 : 1
0.38
Ϫ0.34
8.4 : 1
0.26
Ϫ0.33
Ϫ3
˚
Largest diff. Peak eA
Ϫ3
˚
Largest diff. Hole eA
Largest and Mean D/s
R
0.000, 0.000
0.0442
0.000, 0.000
0.0580
0.000, 0.000
0.0489
vR
0.0677
0.0650
0.0712
Programs used
SHELXTL PLUS
maXus
SHELXTL PLUS
slightly more double bond character. Also, there is no
significant difference in the thiourea moiety’s bond
angles between the present thioureas and those
previously studied with intramolecular hydrogen
bonding [3–7]. In general, the three thioureas
included in Table 3 having only intramolecular
hydrogen bonding [9,11,12] show the following
differences from thioureas with intermolecular
hydrogen bonding: the N–C7 bond is shorter, N–
C7–S1 angle larger and the N0 –C7–S1 angle smaller.
The intramolecular hydrogen bonding common to
all three of the present thioureas shows somewhat

´
´
222
J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
Fig. 2. A perspective view of PyTuoT showing intramolecular hydrogen bonding.
different N0H…N non-bonding distances which
appear to be related to the weak electronic effect of
the methyl group in the ortho and para positions.
PyTumT has the longest N0H…N distance(s) of
2.697(2), 2.697(2) A followed by PyTuoT with
˚
˚
distance(s) of 2.687(4) A. The shortest distance,
2.646(4),2.665(4) A, for PyTupT indicates not only
an electronic effect, but also a steric effect.
˚
Fig. 3. A perspective view of PyTumT showing the two independent molecules of the unit cell.

´
´
J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
223
Fig. 4. A perspective view of PyTupT showing both intramolecuar and intermolecular hydrogen bonding.
0
As was found for N-benzoyl-N0-(4-methoxy-
phenyl) thiourea [8], NH is involved in intermolecular
hydrogen bonding with a sulfur from a neighboring
molecule. The previously studied N-substituted and
3.563(1) A for N-cyclohexyl-N -cyclohexylthiourea
[10]. The present compounds, PyTuoT, PyTumT
and PyTupT, have N…S non-bonding distances of
˚
˚
˚
˚
3.401(2) A, 3.387 and 3.410(2) A and 3.352 and
3.523(4) A, respectively, which is close to the range
found in previous studies [9–13]. The shorter
nonbonding N…S distance for PyTupT suggests a
0
˚
N,N -substituted thioureas average 3.46 A [9–13],
˚
the smallest N…S distance being 3.363(1) A for
N-diethyl-N0-o-tolythiourea [11] and the largest
Table 2
˚
Selected bond distances (A) and angles (Њ) for PyTuoT, PyTumT and PyTupT.
PyTumTa
PyTupTa
˚
Bond distances (A)
PyTuoT
S1–C7
N1–C2
N1–C6
N2–C2
N2–C7
N3–C7
N3–C8
1.678(3)
1.329(4)
1.327(5)
1.392(4)
1.370(4)
1.336(4)
1.440(4)
1.684(2)
1.332(3)
1.352(3)
1.407(3)
1.377(3)
1.331(3)
1.447(3)
1.684(2)
1.329(3)
1.354(3)
1.408(3)
1.373(3)
1.334(3)
1.443(3)
1.684(4)
1.326(6)
1.345(5)
1.397(5)
1.373(4)
1.324(6)
1.435(4)
1.672(4)
1.340(6)
1.341(6)
1.391(5)
1.378(6)
1.355(6)
1.433(6)
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
130.0(4)
124.4(4)
119.7(4)
117.9(4)
119.7(4)
123.4(4)
116.9(4)
120.5(4)
117.8(4)
130.2(2)
124.2(2)
119.4(2)
117.6(2)
118.8(2)
123.5(2)
117.7(2)
119.7(2)
118.1(2)
130.4(2)
123.4(2)
119.0(2)
118.0(2)
118.4(2)
123.7(2)
117.9(2)
120.0(2)
118.5(2)
129.6(4)
128.0(3)
119.3(3)
118.3(4)
118.6(3)
125.4(2)
116.0(2)
118.6(3)
121.3(3)
130.7(6)
125.4(7)
119.2(6)
118.7(7)
119.0(6)
124.5(6)
116.4(7)
118.5(7)
121.9(7)
a The second column represents the analogous bonds in the second molecule.

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J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
224
Table 3
˚
Selected bond distances (A) and bond angles (Њ) for substituted thioureas.
˚
Bond distances, A
Bond angles, Њ
Compound
N2–C7
S1–C7
N3–C7
N2–C7–N3
N2–C7–S1
N3–C7–S1
Ref
BzOTuPra
1.393(5)
1.391(2)
1.393(3)
1.392(4)
1.349(4)
1.356(4)
1.358(2)
1.332(2)
1.374(4)
1.375(4)
1.366(4)
1.370(4)
1.377(3)
1.373(3)
1.373(4)
1.378(6)
1,678(4)
1.672(2)
1.658(2)
1.659(3)
1.681(5)
1.693(3)
1.702(2)
1.696(2)
1.682(3)
1.679(3)
1.689(3)
1.678(3)
1.684(2)
1.684(2)
1.684(4)
1.672(4)
1.332(7)
1.335(3)
1.344(3)
1.329(4)
1.349(4)
1.337(4)
1.344(2)
1.347(2)
1.335(4)
1.333(4)
1.341(4)
1.336(4)
1.331(3)
1.334(3)
1.324(6)
1.354(6)
117.4(3)
114.3(2)
115.0(2)
115.4(3)
113.9(4)
115.6(3)
115.63(14)
117.33(15)
116.8(5)
115.8(5)
115.5(2)
116.9(4)
116.7(2)
117.9(2)
116.0(3)
116.4(7)
118.5(3)
123.30(14)
118.3(2)
119.2(2)
123.0(2)
121.5(3)
121.30(12)
123.62(12)
118.6(4)
117.3(4)
117.6(2)
119.7(4)
118.8(2)
118.4(2)
118.6(3)
119.0(6)
124.1(3)
122.35(14)
126.6(2)
125.4(2)
123.0(2)
122.9(2)
123.07(12)
119.05(13)
124.6(4)
126.9(4)
126.9(2)
123.4(4)
123.5(2)
123.7(2)
125.4(2)
124.5(6)
[4]
[5]
[6]
[7]
(EtOH)2TuPhb
BzOTupNO2Phc
BzOTupMeOPhd
PhTuPhe
[9]
Me2TuoTf
[11]
[11]
[12]
[2]
Et2TuoTg
ChTuPhh
PyTuPhi
6MePyTuPhj
4,6MePyTuPhk
PyTuoT
[14]
[14]
l
l
l
l
PyTumT
PyTupT
a N-benzoyl-N0-propylthiourea
b N,N-di(hydroxyethyl)-N0-phenylthiourea
c N-benzoyl-N0-(4-nitrophenyl) thiourea
d N-benzoyl-N0-(4-methoxyphenyl)thiourea
e N, N0-diphenylthiourea
f N-dimethyl-N0-o-tolythiourea
g N-diethyl-N0-o-tolythiourea
h N-cyclohexyl-N0-phenylthiourea
i N-(2-pyridyl)-N0-phenylthiourea
j N-6-methy-2-pyridyl-N0-phenylthiourea
k N-4,6-dimethy-2-pyridyl-N0-phenylthiourea
l This work.
lower steric effect by the methyl group than for
PyTuoT and PyTumT. The intermolecular N–H…S
bond angles for PyTuoT, PyTumT and PyTupT are
159(2)Њ, 161 and 162(2)Њ and 167 and 171(4)Њ, which
fall in the range of 140(3)Њ (N-dimethyl-N0-o-
tolylthiourea) [11] and 170(1)Њ (N-ethyl-N0-
ethylthiourea) [9] found in previous structural studies
of substituted thioureas. In addition to the N–H…S
hydrogen bond, the sulfur is also interacting with a
pyridyl hydrogen, C3H, with a C–H…S nonbonding
rather planar with the N1–C2–N2–C7–N3 plane
deviating to the greatest extent in the three molecules;
the mean plane deviations for PyTuoT, PyTumT and
PyTupT are 0.0594 A, 0.0141 A and 0.0348 A,
respectively.
˚
˚
˚
The angles between planes also give information
about the molecules with the dihedral angle between
the pyridyl and aryl planes being 67.4(1)Њ; 80.2(1),
78.59(6)Њ and 58.8(1)Њ, 58.6(1)Њ for PyTuoT, PyTumT
and PyTupT, respectively, which are considerably
greater than the 11.24(7)Њ and 13.89(9)Њfound for
previously studied picolyl and lutidyl thioureas,
6MePyTuPh and 4, 6MePyTuPh [14], respectively,
but in the range of 63.2(1)Њ found for unsubstituted
N-(2-pyridyl)-N0-phenylthiourea, PyTuPh [2]. The
pyridyl ring has an angle with the thiourea moiety
plane, N2–N3–C7–S1, of 13.6(2)Њ, 4.6(1)Њ, 2.08(4)Њ
and 10.2(1)Њ, 2.1(1)Њ for PyTuoT, PyTumT and
˚
˚
distance of 3.619(3) A, 3.564 and 3.635(2) A and
˚
3.528 and 3.801(5) A and non-bonding angle of
138.5(3)Њ, 144 and 141.2(2)Њ and 145.6% and 146.7Њ
for PyTuoT, PyTumT and PyTupT, respectively.
For PyTuoT, PyTumT and PyTupT the various
torsion angles involving the thiourea moiety (e.g.,
C7–N2–C2–C3, C8–N3–C7–S1 etc.) are not very
different from 0Њ or 180Њ. Thus, these molecules are

´
´
J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
225
Table 4
1H, 13C NMR (d), ultraviolet and infrared spectral date for PyTuoT, PyTumT and PyTupT.
Compound
PyTuPhb
N0H
NH
CyS
p ! p*
n ! p
n(CyS)
n(NH)
Ref.
[14]
13.865
10.903
178.7
37040
32900
(4.429)
32470
(4.468)
32680
(4.443)
32890
(4.358)
32350
(4.382)
32890
(4.391)
857 m
3195 m
(4.298)a
37040
6MtuPhc
4,6MTuPhd
PyTuoT
14.103
14.119
13.494
13.644
13.771
9.205
8.311
10.013
9.401
10.031
178.0
178.1
179.3
178.7
178.8
850 M
828 m
850 m
831 m
818m
3197 m
3205 m
3200 m
3185 m
3200m
[14]
(4.319)
37040
(4.264)
37040
(4.226)
33980sh
[14]
e
e
e
PyTumT
PyTupT
37040
(4.278)
a log e
b N-2-pyridyl-N0-phenylthiourea
c N-6-methy-2-pyridyl-N0-phenylthiourea
d N-4, 6-dimethy-2-pyridyl-N0-phenylthiourea
e This work.
PyTupT compared to 3.89(3)Њ, 4.66(3)Њ and 5.4(1)Њ for
6MeTuPh, 4,6MeTuPh, andPyTuPh, respectively.
The phenyl ring has angles with the thiourea moiety
of 75.5(1)Њ, 76.1(1)Њ, 77.2(1)Њ and 55.5(1)Њ, 56.5(1)Њ
for PyTuoT, PyTumT and PyTupT respectively,
compared to 11.17(8)Њ, 13.23(6)Њ and 58.0(1)Њ for
6MeTuPh, 4,6MeTuPh, and PyTuPh. Therefore,
based on these six thioureas, it appears that substitu-
tion on the pyridyl ring makes the molecule more
planar, but ortho substitution on the aryl ring makes
the thiourea less planar. The general order of the
decreasing planarity of these thioureas is
heterocyclic ring. Other bands involving the thiourea
function are evidently obscured by this latter band. In
the infrared spectra of PyTuoT, PyTumT and PyTupT
we have assigned n(NH) to medium intensity absorp-
tions in the 3200 cmϪ1 region and n(CS) to bands
between 800–860 cmϪ1 range in agreement with the
three previously studied thiosemicarbazones [14].
1
The H NMR spectra show some variation in the
shift of the resonance caused by the intramolecular
hydrogen bonding N0H in the six pyridyl thioureas
studied to date. Addition of methyl groups to the
pyridyl ring provides greater electron density to the
pyridine nitrogen causing a down field shift for
the resonance of N0H. In contrast, the o-methyl
group in PyTuoT, and to a lesser extent PuTumT
and PyTupT’s methyl groups, appear to weaken the
intramolecular hydrogen bond to the pyridyl nitrogen
based on the upfield position for N0H compared to the
other thoureas in Table 4. This is presumably as a
result of these molecules less planar arrangement
(i.e., in the solid state the angle between the pyridyl
and phenyl planes is 67Њ for PyTuoT, the largest of
these six thioureas). There is a significant upfield shift
for the resonance assigned to NH because of methyl
groups on the pyridyl ring; methyl groups on the
phenyl ring also cause an upfield shift, but of smaller
magnitude. Thus, the inductive effect of the methyl
groups enriches the electron density in the NH bond
6MePyTuPh
Ͼ 4; 6MePyTuPh Ͼ PyTupT Ͼ
PyTuPh Ͼ PyTuouT Ͼ PyTumT. Further, PyTumT
has the longest non-bonding N–H…N distance
˚
˚
{2.697 (2) A} and the others fall in the 2.64 A
range, except for 4,6MePyThPh which is
˚
2.629(4) A. In summary, there are only small differ-
ences in the structural parameters for the six N-(2-
pyridyl)-N0-arylthioureas reported to date.
3.2. Spectral Studies
The UV spectra (DMSO) show one or two bands
for PyTuoT, PyTumT and PyTupT, as well as three
other pyridyl thioureas reported previously [14],
(Table 4) which we assign to a combination of p !
p* transitions from both rings and an n ! p* of the

´
´
226
J. Valdes-Martınez et al. / Journal of Molecular Structure 478 (1999) 219–226
´
[2] D.X. West, A.K Hermetet, L.J. Ackerman, J. Valdes-
and the more remote methyl groups on the phenyl ring
do so to a lesser extent. However, none of the six
thioureas show a significant difference in the 13C reso-
nance of the thione carbon with differing numbers of
methyl groups on either ring. Thus, like the structural
parameters, the spectral data are generally very
similar for the six N-(2-pyridyl)-N0-arylthioureas
studied, the greatest difference involves the chemical
shifts of the two NH0s.
Supplementary material: Crystallographic data
(excluding structure factors) for the structures
reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supple-
mentary publication no. CCDC-1003/m. Copies of
available material can be obtained, free of charge,
on application to the Director, CCDC, 12 Union
Road, teched@chemcrys.cam.ac.uk.
´
Martinez, S. Hernandez-Ortega, submitted to Acta Cryst.
[3] A. Dago, M.A. Simonov, E.A. Pobedimskaya, A. Macias, A.
Martin, Kristallografiya 32 (1987) 1024.
[4] A. Dago, M.A. Simonov, E.A. Pobedimskaya, A. Macias, A.
Martin, Kristallografiya 33 (1988) 1021.
´
[5] A. Dago, Y. Shepelev, F. Fajardo, F. Alvarez, R. Pomes, Acta
Cryst. C45 (1989) 1192.
[6] K.R. Koch, C. Sacht, S. Bourne, Inorg. Chim. Acta 232 (1995)
109.
[7] D.-C. Zhang, Y.-Q. Zhang, Y. Cao, B. Zhao, Acta Cryst. C52
(1996) 1716.
[8] Y. Cao, B. Zhao, Y.-Q. Zhang, Acta Cryst. C52 (1996) 1772.
[9] A. Ramnathan, K. Sivakumar, K. Subramanian, N.
Janarthanan, K. Ramadas, H.-K. Fun, Acta Cryst. C51
(1995) 2446.
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K. Ramadas, H.-K. Fun, Acta Cryst. C52 (1996) 139.
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K. Ramadas, H-K. Fun, Acta Cryst. C52 (1996) 411.
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K. Ramadas, H-K. Fun, Acta Cryst. C52 (1996) 656.
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Acknowledgements
Acknowledgement is made to the Donors of the
Petroleum Research Fund, administered by the Amer-
ican Chemical Society, the National Science Founda-
tion and the Consejo Nacional de Ciencia y
Technologia for the partial support of this research.
[14] D.X. West, C.A. Presto, A.K. Hermetet, K.D. Haslow, L.J.
´
´
Ackerman, J. Valdes-Martinez, S. Hernandez-Ortega, G. Espi-
´
nosa-Perez, submitted to J. Chem. Cryst.
[15] Siemens SHELXTL PCTM: Release 4.1 for Siemens Crystal-
lographic Research System, Siemens Analytical X-ray Instru-
ments, Inc., Madison, WI, USA, 1990.
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Steward, K. Shankland, A. Donald, University of Glasgow,
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