Full Papers
doi.org/10.1002/ejic.202001148
number corresponds to carbon, see Figure S12. For 2D NMR spectra
(approximately one fifth) and further purification was achieved by
recrystallization in hot toluene.
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of fpo and pto see Figure S13-14). The X-ray powder diffraction
patterns were recorded on a MiniFlex600 (Rigaku) diffractometer by
using Cu Kα radiation (λ=1.5418 Å). The temperature-dependent
(T=1.9–300 K, B=0.2 T) and field-dependent (B=0–9 T, T=2, 5
and 10 K) magnetization measurements were performed on PPMS
Dynacool with VSM option. AC susceptibility data were measured
on MPMS XL-7 SQUID magnetometer. The magnetic data were
corrected for the diamagnetism of the constituent atoms (χdia/
II (72%). EA (calc.%) for C H N O (FW=137.14): C, 52.55, H, 5.14, N,
6
7
3
À 1
3
3
(
0.64, Found: C, 52.31, H, 5.08, N, 31.06. FT-IR (mid ATR, v/cm ):
288 (N-H), 3210 (NH), 3017 (CÀ H ), 1671 (C=O), 1622 (NH ), 1593
arom
2
C=C, C=N), 1568 (C=C, C=N), 1518 (C=C, C=N, NH ), 1433 (C=C,
2
C=N), 1123 (C-N), 999 (ring, pyridine), 819 (CÀ H ), 750 (CÀ Harom),
arom
1
620 (ring, pyridine), 410 (ring, pyridine). H NMR (400 MHz, DMSO-
1
3
À 12
3
À 1
[24]
d6) δ 9.9 (s, 1H, -NHÀ ), 8.62–8.59 (m, 1H, H ), 8.01–7.93 (m, 2H, H
10 m mol =-5×Mr) and for the diamagnetism of the sample
holder. The spectra of electron paramagnetic resonance (EPR) were
studied using Bruker ELEXSYS II E500 X-band spectrometer with an
operating frequency of 9.4 GHz equipped with ESR910 helium flow-
type cryostat. The measurements were performed in the temper-
ature range from 2 K to 50 K. A nascent powder was mixed with
Apiezon N grease and attached to the Suprasil sample holder.
4
2
13
and H ), 7.58–7.53 (m, 1H, H ), 4.55 (s, 2H, -NH ). C NMR (101 MHz,
DMSO-d6) δ 162.68 (C =O), 149.86 (C ), 148.52 (C ), 137.67 (C ),
2
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26.27 (C ), 121.76 (C ).
Picolinic acid 2-(2-furanylmethylene)hydrazide (IIIa) and
Picolinic acid 2-(2-thiophenylmethylene)hydrazide (IIIb).
Solution of furfural (1.5 g, 20.8 mmol) in 10 mL of methanol was
added to II (2 g, 14.6 mmol) in 20 mL of methanol or similarly
thiophene-2-carbaldehyde (2.1 g, 19.1 mmol) in 10 mL of methanol
into 40 mL of II (2.5 g, 18.2 mmol) methanolic solution. The
mixtures were refluxed for 3 hours and subsequently cooled in ice.
Crystals of IIIa and beige crystals of IIIb to appear from a yellow
solution. In both cases, IIIa and IIIb, the volume of the original
solution was reduced to acquire the additional amount of product.
Crystal data refinement
X-ray diffraction data of single crystal of compounds 1–3 suitable
for structure determination were collected either on a Nonius
KappaCCD diffractometer equipped with a Bruker APEX-II CCD
detector by monochromatized MoKα radiation (λ=0.71073 Å)
sample 3, or for 1 and 2 samples on a Bruker D8 VENTURE Kappa
Duo PHOTON 100 CMOS diffractometer with monochromatized
MoKα radiation (λ=0.71073 Å). The structures were solved by
direct methods (SHELXT2014/5) and refined by full-matrix least
IIIa, (94%). EA (calc.%) for C H N O (FW=215.21): C, 61.39; H, 4.22;
1
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2
N, 19.53; Found: C, 61.46; H, 4.20; N, 19.75. FT-IR (mid ATR, v/cmÀ 1):
3287 (NH), 3225 (NH), 3132 (CÀ H ), 3112 (CÀ H ), 3086 (CÀ H ),
2
[38]
squares based on F (SHELXT2018/3). The hydrogen atoms on
carbon atoms were found on difference Fourier map and recalcu-
lated into idealised positions (riding model) and refined with
arom
arom
arom
3060 (CÀ Harom), 3003 (CÀ Harom), 1675 (C=O), 1627 (C=N, imine), 1590
(
C=C, C=N), 1572 (C=C, C=N), 1520 (C=C, C=N), 1434 (C=C, C=N),
assigned temperature factors H (H)=1.2 U (pivot atom). The
iso
eq
996 (ring, pyridine), 613 (ring, pyridine), 594 (ring, furan), 406 (ring,
pyridine). H NMR (400 MHz, DMSO-d6) δ 12.23 (s, 1H, -NH-), 8.70 (d,
J=4.7 Hz, 1H, H ), 8.56 (s, 1H, H ), 8.12 (d, J=7.8 Hz, 1H, H ), 8.07-
crystal 2 was refined as non-merohedral twin with the volume
ration of two domains 0.58:0.42. The disorder of thiophen moiety
was treated by splitting of sulphur and opposite carbon atoms into
two positions. Their occupation factors were refined to 0.772:228.
The restriction of positions and displacement parameters of
disordered atoms were applied to ensure their physical meaning.
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.02 (m, 1H, H ), 7.87–7.85 (m, 1H, H ), 7.66 (d, J=7.5 Hz, 1H, H ),
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0
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6.92-6.90 (m, 1H, H ), 6.64 (dd, J=3.4, 1.8 Hz, 1H, H ). C NMR
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(
1
(
101 MHz, DMSO-d6) δ 160.40 (C =O), 149.57 (C ), 149.51 (C ),
1
11
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3
2
48.48 (C ), 145.30 (C ), 138.78 (C ), 138.06 (C ), 127.04 (C ), 122.73
4 9 10
C ), 113.59 (C ), 112.30 (C ).
Methyl picolinate (I).
IIIb, (93%). EA (calc. %) for C11
H
N
9
OS (FW=231.28): C, 57.13; H,
3
A flask containing 100 mL of methanol with solid picolinic acid
(10 g, 81.2 mmol) was vigorously stirred. After careful addition of
12 mL of 96% sulfuric acid white solid of picolinic acid dissolved
and the mixture was refluxed for one day. Reduction of solvent
volume by rotary evaporation under reduced pressure yielded
yellowish oil which was poured into 400 mL water/ice mixture and
neutralized with potassium bicarbonate. Subsequent extraction of
water solution five times with 50 mL of chloroform, drying with
MgSO4 and evaporation of chloroform produces yellowish oil.
Further drying under vacuum yields I.
3
.92; N, 18.17; Found: C, 57.13; H, 3.72; N,18.00. FT-IR (mid ATR, v/
À 1
cm ): 3231 (NH), 3074 (CÀ H ), 3048 (CÀ H ), 3032 (CÀ Harom),
arom
arom
2
1
999 (CÀ H ), 1668 (C=O), 1586 (C=C, C=N), 1535 (C=C, C=N),
arom
508 (C=C, C=N), 995 (ring, pyridine), 714 (=CH, thiophene), 694
(
=CH, thiophene), 634 (CS, thiophene), 616 (ring, pyridine), 398
1
(ring, pyridine). H NMR (400 MHz, DMSO-d6) δ 12.18 (s, 1H, -NH-),
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3
8
.84 (s, 1H, H ), 8.71 (d, J=4.7 Hz, 1H, H ), 8.12-8.03 (m, 2H, H and
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1
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H ), 7.70–7.65 (m, 2H, H and H ), 7.43 (d, J=3.5 Hz, 1H, H ), 7.15 (t,
10
13
6
J=4.3 Hz, 1H, H ). C NMR (101 MHz, DMSO-d6) δ 160.26 (C =O),
1
(C ), 129.16 (C ), 127.95 (C ), 127.02 (C ), 122.70 (C ).
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3
49.54 (C ), 148.51 (C ), 144.08 (C ), 139.18 (C ), 138.06 C ), 131.03
À 1
9 11 10 2 4
I (93%). FT-IR (mid ATR, v/cm ): 3058 (CÀ H ), 2952 (CH ), 2844
arom
3
(CH ), 1742 (CO), 1719 (CO), 1582 (C=C, C=N), 1572 (C=C, C=N),
3
1469 (C=C, C=N), 1442 (CH ), 1431 (C=C, C=N), 1281 (COC), 1244
3
(
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OCH ), 1125 (COC), 995 (ring, pyridine), 745 (CÀ H ), 705 (CÀ Harom),
2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (fpo),
2-(pyridin-2-yl)-5-(thiophen-2-yl)-1,3,4-oxadiazole (pto)
3
arom
1
19 (ring, pyridine), 405 (ring, pyridine). H NMR (400 MHz, CDCl ) δ
3
1 4
.71-8.69 (m, 1H, H ), 8.09 (d, J=7.8 Hz, 1H, H ), 7.82-7.78 (m, 1H,
3
2
13
Compounds IIIa (1000 mg, 4.65 mmol) or IIIb (1400 mg, 6.05 mmol)
were stirred at room temperature in 20 mL of dimethylsulfoxide
and potassium carbonate (2 equiv) with iodine (2 equiv) were
slowly added to the mixture. The solution turned dark and the
temperature was adjusted to 110°C and left stirring overnight.
Subsequently, dimethylsulfoxide was evaporated and the resultant
solid was suspended in water with sodium metabisulfite and
extracted five times with 20 mL of ethylacetate. Evaporating of
combined parts of ethylacetate and redissolving the solid in the
minimum amount of cyclohexane:ethylacetate (2:1) yielded white
H ), 7.45–7.42 (m, 1H, H ), 3.96 (s, 3H, -OCH ). C NMR (101 MHz,
CDCl ) δ 165.73 (C =O), 149.85 (C ), 147.92 (C ), 137.12 (C ), 127.03
(C ), 125.19 (C ), 52.97 (À CH ).
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3
Picolinic acid hydrazide (II).
Compound I (9.18 g, 67 mmol) in 10 mL of methanol was trans-
ferred into 70 mL of methanol solution containing 50–60%
hydrazine hydrate (17.2 g) and the mixture was refluxed overnight.
Colorless crystalline solid of II forms after volume reduction
Eur. J. Inorg. Chem. 2021, 1190–1199
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