The conformation of the seven-membered ring in the title compound, C
18H
14N
5+·Cl
−, is close to a boat, and this fragment has an approximate mirror plane of symmetry. The protonation takes place at an N atom of the triazole ring. One strong N—H
Cl and two weak C—H
Cl hydrogen bonds determine the crystal packing.
Supporting information
CCDC reference: 159725
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.003 Å
- R factor = 0.048
- wR factor = 0.113
- Data-to-parameter ratio = 12.3
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
The title compound was provided by Ciba-Geigy. Colourless crystals were grown
from an ethanol solution by slow evaporation.
Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: ENPROC (Rettig, 1978); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation (Siemens, 1989).
1-(2-Pyridyl)-8
H-pyrrolo[2,1-
c]-s-triazolo[4,3-
a][1,4]benzodiazepinium chloride
top
Crystal data top
C18H14N5+·Cl− | F(000) = 696 |
Mr = 335.79 | Dx = 1.352 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54178 Å |
a = 8.7856 (5) Å | Cell parameters from 25 reflections |
b = 8.2058 (5) Å | θ = 5–35° |
c = 22.990 (2) Å | µ = 2.12 mm−1 |
β = 95.513 (6)° | T = 293 K |
V = 1649.8 (2) Å3 | Block, colourless |
Z = 4 | 0.2 × 0.2 × 0.15 mm |
Data collection top
CAD-4F four-circle diffractometer | Rint = 0.048 |
Radiation source: fine-focus sealed tube | θmax = 74.8°, θmin = 5.1° |
Ni-filter monochromator | h = 0→10 |
ω/2θ scans | k = −10→0 |
3604 measured reflections | l = −28→28 |
3380 independent reflections | 2 standard reflections every 33 min |
3315 reflections with I > 2σ(I) | intensity decay: 2% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.048 | All H-atom parameters refined |
wR(F2) = 0.113 | w = 1/[σ2(Fo2) + (0.01P)2 + 0.7P] where P = (Fo2 + 2Fc2)/3 |
S = 1.26 | (Δ/σ)max = 0.001 |
3380 reflections | Δρmax = 0.42 e Å−3 |
274 parameters | Δρmin = −0.55 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0098 (6) |
Crystal data top
C18H14N5+·Cl− | V = 1649.8 (2) Å3 |
Mr = 335.79 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 8.7856 (5) Å | µ = 2.12 mm−1 |
b = 8.2058 (5) Å | T = 293 K |
c = 22.990 (2) Å | 0.2 × 0.2 × 0.15 mm |
β = 95.513 (6)° | |
Data collection top
CAD-4F four-circle diffractometer | Rint = 0.048 |
3604 measured reflections | 2 standard reflections every 33 min |
3380 independent reflections | intensity decay: 2% |
3315 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.113 | All H-atom parameters refined |
S = 1.26 | Δρmax = 0.42 e Å−3 |
3380 reflections | Δρmin = −0.55 e Å−3 |
274 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Cl1 | 0.57862 (5) | 0.82294 (7) | 0.166179 (19) | 0.05235 (18) | |
C1 | −0.0478 (2) | 0.5787 (2) | 0.15720 (8) | 0.0428 (4) | |
H1 | −0.158 (3) | 0.587 (3) | 0.1477 (10) | 0.056 (6)* | |
C2 | 0.0678 (2) | 0.5067 (2) | 0.13014 (8) | 0.0471 (4) | |
H2 | 0.057 (3) | 0.455 (3) | 0.0961 (10) | 0.057 (6)* | |
C3 | 0.2052 (2) | 0.5325 (2) | 0.16482 (8) | 0.0428 (4) | |
H3 | 0.304 (2) | 0.494 (3) | 0.1596 (9) | 0.046 (6)* | |
C4 | 0.16905 (19) | 0.6198 (2) | 0.21296 (7) | 0.0359 (4) | |
C5 | 0.26225 (19) | 0.6754 (2) | 0.26350 (7) | 0.0354 (4) | |
N6 | 0.40341 (17) | 0.7306 (2) | 0.26449 (7) | 0.0424 (4) | |
H6 | 0.459 (3) | 0.759 (3) | 0.2313 (10) | 0.054 (6)* | |
N7 | 0.46255 (18) | 0.7704 (2) | 0.31949 (7) | 0.0459 (4) | |
C8 | 0.3530 (2) | 0.7391 (2) | 0.35263 (8) | 0.0393 (4) | |
N1' | 0.2539 (2) | 0.8371 (2) | 0.43927 (7) | 0.0546 (4) | |
C2' | 0.3703 (2) | 0.7668 (2) | 0.41603 (8) | 0.0419 (4) | |
C3' | 0.5043 (3) | 0.7222 (3) | 0.44829 (10) | 0.0607 (6) | |
H3' | 0.584 (3) | 0.672 (3) | 0.4275 (12) | 0.071 (8)* | |
C4' | 0.5173 (3) | 0.7502 (4) | 0.50771 (11) | 0.0715 (7) | |
H4' | 0.615 (4) | 0.730 (4) | 0.5307 (14) | 0.096 (10)* | |
C5' | 0.3987 (3) | 0.8224 (3) | 0.53224 (10) | 0.0648 (6) | |
H5' | 0.408 (3) | 0.843 (3) | 0.5744 (12) | 0.073 (8)* | |
C6' | 0.2716 (3) | 0.8627 (4) | 0.49654 (10) | 0.0654 (6) | |
H6' | 0.191 (3) | 0.908 (4) | 0.5103 (12) | 0.077 (8)* | |
N9 | 0.22472 (15) | 0.68080 (17) | 0.31946 (6) | 0.0340 (3) | |
C10 | 0.08906 (19) | 0.6093 (2) | 0.33966 (7) | 0.0350 (4) | |
C11 | 0.1031 (2) | 0.5132 (2) | 0.38937 (8) | 0.0440 (4) | |
H11 | 0.201 (3) | 0.497 (3) | 0.4101 (9) | 0.050 (6)* | |
C12 | −0.0272 (3) | 0.4441 (3) | 0.40865 (10) | 0.0543 (5) | |
H12 | −0.020 (3) | 0.383 (4) | 0.4469 (13) | 0.081 (8)* | |
C13 | −0.1677 (3) | 0.4676 (3) | 0.37776 (10) | 0.0560 (5) | |
H13 | −0.256 (3) | 0.417 (4) | 0.3920 (11) | 0.073 (8)* | |
C14 | −0.1796 (2) | 0.5601 (3) | 0.32752 (10) | 0.0487 (5) | |
H14 | −0.279 (3) | 0.573 (3) | 0.3040 (10) | 0.057 (6)* | |
C15 | −0.05162 (19) | 0.6339 (2) | 0.30754 (8) | 0.0378 (4) | |
C16 | −0.0641 (2) | 0.7316 (2) | 0.25220 (8) | 0.0405 (4) | |
H16B | −0.169 (3) | 0.744 (3) | 0.2376 (10) | 0.053 (6)* | |
H16A | −0.015 (2) | 0.840 (3) | 0.2590 (9) | 0.043 (5)* | |
N17 | 0.01414 (16) | 0.64735 (17) | 0.20759 (6) | 0.0369 (3) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cl1 | 0.0415 (3) | 0.0770 (4) | 0.0395 (3) | −0.0112 (2) | 0.00837 (18) | 0.0050 (2) |
C1 | 0.0470 (10) | 0.0405 (9) | 0.0396 (9) | −0.0050 (8) | −0.0028 (8) | 0.0024 (7) |
C2 | 0.0620 (12) | 0.0454 (10) | 0.0339 (9) | −0.0069 (9) | 0.0055 (8) | −0.0029 (8) |
C3 | 0.0495 (10) | 0.0435 (10) | 0.0368 (9) | −0.0010 (8) | 0.0115 (8) | 0.0014 (7) |
C4 | 0.0365 (8) | 0.0360 (8) | 0.0355 (8) | −0.0017 (7) | 0.0059 (6) | 0.0039 (7) |
C5 | 0.0348 (8) | 0.0365 (8) | 0.0355 (8) | −0.0007 (7) | 0.0064 (6) | 0.0032 (6) |
N6 | 0.0361 (8) | 0.0561 (9) | 0.0360 (7) | −0.0082 (7) | 0.0079 (6) | 0.0024 (7) |
N7 | 0.0374 (8) | 0.0602 (10) | 0.0403 (8) | −0.0085 (7) | 0.0040 (6) | 0.0008 (7) |
C8 | 0.0336 (8) | 0.0449 (9) | 0.0396 (9) | −0.0017 (7) | 0.0043 (7) | 0.0013 (7) |
N1' | 0.0538 (10) | 0.0672 (11) | 0.0430 (9) | 0.0073 (8) | 0.0064 (7) | −0.0032 (8) |
C2' | 0.0416 (9) | 0.0451 (10) | 0.0384 (9) | −0.0030 (8) | 0.0016 (7) | 0.0028 (7) |
C3' | 0.0545 (12) | 0.0741 (15) | 0.0512 (12) | 0.0128 (11) | −0.0062 (10) | −0.0018 (11) |
C4' | 0.0767 (17) | 0.0825 (18) | 0.0506 (13) | 0.0082 (14) | −0.0182 (12) | 0.0048 (12) |
C5' | 0.0911 (18) | 0.0666 (14) | 0.0360 (10) | −0.0074 (13) | 0.0022 (11) | 0.0004 (10) |
C6' | 0.0750 (16) | 0.0777 (16) | 0.0451 (11) | 0.0055 (13) | 0.0140 (11) | −0.0065 (11) |
N9 | 0.0316 (7) | 0.0371 (7) | 0.0338 (7) | −0.0012 (5) | 0.0053 (5) | 0.0018 (5) |
C10 | 0.0342 (8) | 0.0335 (8) | 0.0391 (8) | −0.0014 (6) | 0.0122 (6) | −0.0018 (7) |
C11 | 0.0473 (10) | 0.0432 (10) | 0.0431 (9) | 0.0008 (8) | 0.0129 (8) | 0.0041 (8) |
C12 | 0.0665 (13) | 0.0458 (11) | 0.0546 (12) | −0.0044 (10) | 0.0270 (10) | 0.0065 (9) |
C13 | 0.0501 (11) | 0.0516 (12) | 0.0713 (14) | −0.0105 (9) | 0.0310 (10) | −0.0044 (10) |
C14 | 0.0361 (9) | 0.0469 (10) | 0.0651 (12) | −0.0025 (8) | 0.0156 (9) | −0.0110 (9) |
C15 | 0.0354 (8) | 0.0334 (8) | 0.0458 (9) | 0.0008 (7) | 0.0105 (7) | −0.0071 (7) |
C16 | 0.0354 (9) | 0.0383 (9) | 0.0473 (10) | 0.0054 (7) | 0.0011 (7) | −0.0037 (8) |
N17 | 0.0373 (7) | 0.0347 (7) | 0.0383 (7) | −0.0006 (6) | 0.0018 (6) | −0.0001 (6) |
Geometric parameters (Å, º) top
C1—N17 | 1.354 (2) | C4'—C5' | 1.367 (4) |
C1—C2 | 1.374 (3) | C4'—H4' | 0.98 (3) |
C1—H1 | 0.97 (2) | C5'—C6' | 1.362 (4) |
C2—C3 | 1.398 (3) | C5'—H5' | 0.98 (3) |
C2—H2 | 0.89 (2) | C6'—H6' | 0.88 (3) |
C3—C4 | 1.381 (2) | N9—C10 | 1.445 (2) |
C3—H3 | 0.94 (2) | C10—C11 | 1.384 (2) |
C4—N17 | 1.373 (2) | C10—C15 | 1.392 (2) |
C4—C5 | 1.430 (2) | C11—C12 | 1.388 (3) |
C5—N6 | 1.319 (2) | C11—H11 | 0.95 (2) |
C5—N9 | 1.359 (2) | C12—C13 | 1.377 (3) |
N6—N7 | 1.360 (2) | C12—H12 | 1.01 (3) |
N6—H6 | 0.97 (2) | C13—C14 | 1.378 (3) |
N7—C8 | 1.309 (2) | C13—H13 | 0.97 (3) |
C8—N9 | 1.384 (2) | C14—C15 | 1.394 (3) |
C8—C2' | 1.469 (2) | C14—H14 | 0.98 (2) |
N1'—C6' | 1.328 (3) | C15—C16 | 1.499 (3) |
N1'—C2' | 1.330 (3) | C16—N17 | 1.463 (2) |
C2'—C3' | 1.379 (3) | C16—H16B | 0.95 (2) |
C3'—C4' | 1.379 (3) | C16—H16A | 0.99 (2) |
C3'—H3' | 0.98 (3) | | |
| | | |
N17—C1—C2 | 108.2 (2) | C4'—C5'—H5' | 119 (2) |
N17—C1—H1 | 118 (1) | N1'—C6'—C5' | 124.8 (3) |
C2—C1—H1 | 134 (1) | N1'—C6'—H6' | 114 (2) |
C1—C2—C3 | 108.2 (2) | C5'—C6'—H6' | 122 (2) |
C1—C2—H2 | 126 (2) | C5—N9—C8 | 105.9 (1) |
C3—C2—H2 | 126 (2) | C5—N9—C10 | 125.0 (1) |
C4—C3—C2 | 106.4 (2) | C8—N9—C10 | 128.1 (1) |
C4—C3—H3 | 124 (1) | C11—C10—C15 | 121.7 (2) |
C2—C3—H3 | 129 (1) | C11—C10—N9 | 119.1 (2) |
N17—C4—C3 | 108.4 (2) | C15—C10—N9 | 119.2 (2) |
N17—C4—C5 | 120.4 (2) | C10—C11—C12 | 119.0 (2) |
C3—C4—C5 | 131.2 (2) | C10—C11—H11 | 120 (1) |
N6—C5—N9 | 106.6 (2) | C12—C11—H11 | 121 (1) |
N6—C5—C4 | 126.0 (2) | C13—C12—C11 | 120.3 (2) |
N9—C5—C4 | 127.4 (2) | C13—C12—H12 | 120 (2) |
C5—N6—N7 | 111.9 (1) | C11—C12—H12 | 120 (2) |
C5—N6—H6 | 128 (1) | C12—C13—C14 | 120.1 (2) |
N7—N6—H6 | 120 (1) | C12—C13—H13 | 119 (2) |
C8—N7—N6 | 104.9 (2) | C14—C13—H13 | 121 (2) |
N7—C8—N9 | 110.6 (2) | C13—C14—C15 | 121.1 (2) |
N7—C8—C2' | 122.4 (2) | C13—C14—H14 | 121 (1) |
N9—C8—C2' | 127.0 (2) | C15—C14—H14 | 118 (1) |
C6'—N1'—C2' | 116.5 (2) | C10—C15—C14 | 117.7 (2) |
N1'—C2'—C3' | 123.3 (2) | C10—C15—C16 | 121.1 (2) |
N1'—C2'—C8 | 117.1 (2) | C14—C15—C16 | 121.1 (2) |
C3'—C2'—C8 | 119.6 (2) | N17—C16—C15 | 110.0 (1) |
C4'—C3'—C2' | 118.3 (2) | N17—C16—H16B | 108 (1) |
C4'—C3'—H3' | 124 (2) | C15—C16—H16B | 110 (1) |
C2'—C3'—H3' | 118 (2) | N17—C16—H16A | 108 (1) |
C5'—C4'—C3' | 119.1 (2) | C15—C16—H16A | 111 (1) |
C5'—C4'—H4' | 121 (2) | H16B—C16—H16A | 110 (2) |
C3'—C4'—H4' | 120 (2) | C1—N17—C4 | 108.8 (2) |
C6'—C5'—C4' | 118.1 (2) | C1—N17—C16 | 128.3 (2) |
C6'—C5'—H5' | 123 (2) | C4—N17—C16 | 122.9 (2) |
| | | |
N17—C1—C2—C3 | −0.3 (2) | N7—C8—N9—C5 | 1.0 (2) |
C1—C2—C3—C4 | 0.4 (2) | C2'—C8—N9—C5 | −179.9 (2) |
C2—C3—C4—N17 | −0.4 (2) | N7—C8—N9—C10 | 169.7 (2) |
C2—C3—C4—C5 | 177.6 (2) | C2'—C8—N9—C10 | −11.1 (3) |
N17—C4—C5—N6 | −144.8 (2) | C5—N9—C10—C11 | 131.4 (2) |
C3—C4—C5—N6 | 37.4 (3) | C8—N9—C10—C11 | −35.4 (3) |
N17—C4—C5—N9 | 35.8 (3) | C5—N9—C10—C15 | −46.3 (2) |
C3—C4—C5—N9 | −142.0 (2) | C8—N9—C10—C15 | 146.9 (2) |
N9—C5—N6—N7 | 1.0 (2) | C15—C10—C11—C12 | −2.1 (3) |
C4—C5—N6—N7 | −178.6 (2) | N9—C10—C11—C12 | −179.8 (2) |
C5—N6—N7—C8 | −0.4 (2) | C10—C11—C12—C13 | 1.7 (3) |
N6—N7—C8—N9 | −0.4 (2) | C11—C12—C13—C14 | 0.0 (3) |
N6—N7—C8—C2' | −179.6 (2) | C12—C13—C14—C15 | −1.2 (3) |
C6'—N1'—C2'—C3' | −0.5 (3) | C11—C10—C15—C14 | 0.8 (3) |
C6'—N1'—C2'—C8 | −179.4 (2) | N9—C10—C15—C14 | 178.5 (2) |
N7—C8—C2'—N1' | 136.0 (2) | C11—C10—C15—C16 | −177.0 (2) |
N9—C8—C2'—N1' | −43.1 (3) | N9—C10—C15—C16 | 0.7 (2) |
N7—C8—C2'—C3' | −43.0 (3) | C13—C14—C15—C10 | 0.8 (3) |
N9—C8—C2'—C3' | 137.9 (2) | C13—C14—C15—C16 | 178.7 (2) |
N1'—C2'—C3'—C4' | 0.9 (4) | C10—C15—C16—N17 | 66.1 (2) |
C8—C2'—C3'—C4' | 179.8 (2) | C14—C15—C16—N17 | −111.7 (2) |
C2'—C3'—C4'—C5' | −0.8 (4) | C2—C1—N17—C4 | 0.0 (2) |
C3'—C4'—C5'—C6' | 0.4 (4) | C2—C1—N17—C16 | −177.3 (2) |
C2'—N1'—C6'—C5' | 0.1 (4) | C3—C4—N17—C1 | 0.2 (2) |
C4'—C5'—C6'—N1' | 0.0 (4) | C5—C4—N17—C1 | −178.0 (2) |
N6—C5—N9—C8 | −1.1 (2) | C3—C4—N17—C16 | 177.7 (2) |
C4—C5—N9—C8 | 178.4 (2) | C5—C4—N17—C16 | −0.6 (2) |
N6—C5—N9—C10 | −170.4 (2) | C15—C16—N17—C1 | 112.5 (2) |
C4—C5—N9—C10 | 9.2 (3) | C15—C16—N17—C4 | −64.4 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N6—H6···Cl1 | 0.97 (2) | 1.98 (2) | 2.953 (2) | 177 (2) |
C16—H16B···Cl1i | 0.95 (2) | 2.71 (2) | 3.624 (2) | 161 (2) |
C5′—H5′···Cl1ii | 0.98 (3) | 2.82 (3) | 3.531 (2) | 130 (2) |
Symmetry codes: (i) x−1, y, z; (ii) x, −y+3/2, z+1/2. |
Experimental details
Crystal data |
Chemical formula | C18H14N5+·Cl− |
Mr | 335.79 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 8.7856 (5), 8.2058 (5), 22.990 (2) |
β (°) | 95.513 (6) |
V (Å3) | 1649.8 (2) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 2.12 |
Crystal size (mm) | 0.2 × 0.2 × 0.15 |
|
Data collection |
Diffractometer | CAD-4F four-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3604, 3380, 3315 |
Rint | 0.048 |
(sin θ/λ)max (Å−1) | 0.626 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.113, 1.26 |
No. of reflections | 3380 |
No. of parameters | 274 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.42, −0.55 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N6—H6···Cl1 | 0.97 (2) | 1.98 (2) | 2.953 (2) | 177 (2) |
C16—H16B···Cl1i | 0.95 (2) | 2.71 (2) | 3.624 (2) | 161 (2) |
C5'—H5'···Cl1ii | 0.98 (3) | 2.82 (3) | 3.531 (2) | 130 (2) |
Symmetry codes: (i) x−1, y, z; (ii) x, −y+3/2, z+1/2. |
In the course of studies on benzodiazepine derivatives, potential new neurodrugs, we solved the crystal structure of title compound, (I). Similar compounds with the s-triazole ring fused to the benzodiazepine skeleton are used clinically as anxiolytics and hypnotics (for example, alprazolam, marketed as Xanax, and triazolam, marketed as Halcion).
The protonation takes place at one of N atoms of triazole ring, and the resulting N—H group acts as a donor in a strong linear hydrogen bond with the chloride anion.
The overall shape of the cation (see Fig. 1) is mainly determined by the conformation of the seven-membered ring, which is close to the cycloheptatriene-like boat (also the bond-length pattern within this ring indicates a similarity to the cycloheptatriene ring). There is an approximate mirror plane that passes through the C16 atom and the midpoint of the C5—N9 bond; the appropriate asymmetry parameter (Duax & Norton, 1976) Δs = 6.10. The conformation of the diazepine ring can be also described by the dihedral angles between the central plane of the boat (C4/C10/C15/N17) and the planes of its `bow' (C15/C16/N17) and `stern' (C4/C5/N9/C10). The values of the bow and stern angles, of 52.3 (2) and 36.00 (7)°, respectively, compare well with the angles found in similar benzodiazepine derivatives [for example, 55.5 (8) and 36.2 (8)° in 1-methyl-6-phenyl-8-(trifluoromethyl)-4H-s-triazolo[4,3-a]- [1,4]benzodiazepine (Kemmish & Hamor, 1988), and 53.4 (7) and 34.3 (7)° in 8-chloro-6-(2-chlorophenyl)-1-(4-pyridyl)-1,2,4-triazolo[4,3-a][1,4]- benzodiazepine (Kemmish & Hamor, 1989)].
The three rings fused to the central seven-membered ring are planar within experimental error (maximum deviations from the least-squares planes are 0.006 (1) Å for the triazine, 0.012 (2) Å for the benzo and 0.002 (1) Å for the pyrrolo ring). The mutual disposition of these rings is obviously enforced by the conformation of diazepine ring. Relatively free rotation is possible only around the C8—C2' bond; the dihedral angle between the triazinium and pyridine planes is 43.31 (6)°. The crystal packing is determined mainly by van der Waals interactions and hydrogen bonds accepted by the chloride anion; one strong N—H···Cl and two weaker, but structurally important, C—H···Cl bonds. These bonds connect the cations and anions into layers approximately perpendicular to the [010] direction (Fig. 2).