26 Serebryanskaya et al.
was stirred under reflux for 4–5 h. Then solvent was
removed under vacuum, solid residue was recrystal-
lized from diluted solution of NaOH, and then from
ethyl acetate (for 3a), acetonitrile (for 3b), or ethanol
(for 3c and 3d).
Crystal Structure Determination
Single crystal X-ray data for 3b and 3d were
collected at room temperature on a Nicolet R3m
diffractometer (graphite-monochromated Mo Kα ra-
diation, ω–2θ scans). The structures were solved by
direct methods using program SIR2004 [29]. Refine-
ment on F2 was carried out by full-matrix least-
squares technique as implemented in SHELXL-
97 [30]. Anisotropic displacement parameters were
used for all non-hydrogen atoms. The H atoms were
located from difference maps and refined using “rid-
ing” model. Crystal data and refinement details are
given in Table 1.
3a: Yield: 68%. DSC (10◦C min−1): mp 184◦C,
248◦C (decomp.) (Lit. 183–184 [25]). IR (ν, cm−1):
3044 (w), 3023 (m), 2962 (m), 2923 (w), 1513 (s),
1448 (s), 1406 (w), 1283 (s), 1248 (m), 1185 (s),
1043 (s), 918 (w), 828 (w), 757 (s), 687 (s), 547 (s),
435 (m). 1H NMR (DMSO-d6, δ, ppm): 4.38 (s, CH3).
13C NMR (DMSO-d6, δ, ppm): 159.44 (C5), 35.52
(CH3). 15N NMR (DMSO-d6, δ, ppm): −153.5 (N1),
−3.8 (N2). UV–vis (CH3CN, nm): λmax (ε, M−1 dm−1) =
300 (7.2 × 104), 455 (2.2 × 103). C4H6N10 (194.16): C,
24.74; H, 3.11; N, 72.14. Found: C, 24.66; H, 3.07; N,
72.30.
Molecular Orbital Calculations
3b: Yield: 45%. DSC (10◦C min−1): 240◦C (de-
comp.) (Lit. 225–227 [23]). IR (ν, cm−1): 3184 (w),
3102 (m), 3072 (m), 3044 (w), 1593 (s), 1498 (s),
1475 (s), 1442 (s), 1322 (m), 1283 (s), 1178 (s),
1142 (s), 1074 (s), 1023 (s), 996 (s), 925 (m), 844 (w),
763 (s), 732 (s), 687 (s), 596 (s), 507 (s), 460 (m).
1H NMR (DMSO-d6, δ, ppm): 7.81 (d, 2H, CHarom),
7.66 (m, 3H, CHarom). 13C NMR (DMSO-d6, δ, ppm):
158.47 (C5), 132.5, 130.48, 129.22, 124.73 (C6H5).
UV–vis (CH3CN, nm): λmax (ε, M−1 dm−1) = 300
(1.2 × 105), 455 (3.2 × 103). C14H10N10 (318.30): C,
52.83; H, 3.17; N, 44.01. Found: C, 52.96; H, 3.11; N,
44.16.
Molecular orbital calculations have been carried out
using the density functional theory B3LYP method
[31]. Geometries of all investigated structures were
optimized with 6-31G* basis set. Our previous inves-
tigations [32] showed that this computational level
provided good agreement of the calculated geome-
tries of tetrazole derivatives with the experimental
data. The validity of the DFT B3LYP method for
studying geometry and isomerism of diazene [13],
azobenzene [14,16–19], and similar molecular sys-
tems was also shown.
To obtain the stable conformations, arising as
a result of rotation of tetrazole cycle around exo-
cyclic C N bond, for the trans-isomers of the com-
pounds, the potential energy surface (PES) was gen-
erated by scanning one of N N C N dihedral angle
from 0.0◦ to 180.0◦. Obtained structures, correspond-
ing to minima on the PES, were then fully optimized
without any symmetry restrictions and zero-point vi-
brational energies (ZPVE) were calculated with un-
scaled frequencies for obtained structures. To find
total energies (E), single-point energy calculations
were performed with 6-31+G** basis set.
3c: Yield: 65%. DSC (10◦C min−1): mp 163◦C,
181◦C (decomp.) (Lit. 170–172 [25]). IR (ν, cm−1):
3049 (w), 2957 (w), 2920 (w), 1534 (w), 1486 (s),
1448 (s), 1422 (m), 1380 (s), 1348 (s), 1271 (w),
1197 (m), 1094 (m), 1036 (m), 895 (w), 861 (w),
778 (vs), 690 (w), 649 (m), 571 (m). 1H NMR (DMSO-
d6, δ, ppm): 4.55 (s, CH3). 13C NMR (DMSO-d6, δ,
ppm): 171.0 (C5), 40.4 (CH3). 15N NMR (DMSO-d6,
δ, ppm): −76.8 (N1), −96.6 (N2), 4.2 (N3), −54.1
(N4). UV–vis (CH3CN, nm): λmax (ε, M−1 dm−1) = 290
(1.1 × 105), 425 (3.8 × 103). C4H6N10 (194.16): C,
24.74; H, 3.11; N, 72.14. Found: C, 24.82; H, 3.03; N,
72.10.
The solvent effects on the geometrical parame-
ters and relative stabilities of isomers of investigated
bis(tetrazol-5-yl)diazenes were evaluated using the
polarized continuum model (PCM) [33] with the de-
3d: Yield: 59%. DSC (10◦C min−1): 187◦C (de-
comp.). IR (ν, cm−1): 2990 (s), 2941 (m), 2879 (w),
1458 (s), 1399 (m), 1375 (s), 1304 (s), 1273 (m),
1238 (m), 1217 (m), 1190 (s), 1147 (m), 1076 (w),
1029 (m), 934 (w), 870 (w), 822 (m), 775 (m), 749 (m),
600 (m), 566 (m), 503 (w), 466 (w). 1H NMR (DMSO-
d6, δ, ppm): 1.79 (s, CH3). 13C NMR (DMSO-d6, δ,
ppm): 170.9 (C5), 65.7 (CMe3), 28.7 (CH3). 15N NMR
(DMSO-d6, δ, ppm): −69.9 (N2). UV–vis (CH3CN,
nm): λmax (ε, M−1 dm−1) = 290 (1.9 × 105), 425 (4.4 ×
103). C10H18N10 (278.32): C, 43.15; H, 6.52; N, 50.33.
Found: C, 43.33; H, 6.65; N, 50.17.
fault parameters for water. The PCM energies (EPCM
)
were calculated at B3LYP/6-31+G** level using ge-
ometries optimized for isolated structures.
To compare the relative stability of above-
mentioned isomers in gas phase and in aqueous so-
lution, the ZPVE corrected energies (E0) and Gibbs
energies in solution (Gs) were calculated for each
species using the following equations:
E0 = E + ZPVE
Gs = E0 + solvG
Heteroatom Chemistry DOI 10.1002/hc