For all structures: Z = 4. Experiments were carried out at 100 K with Mo Kα radiation using a Bruker D8 Venture diffractometer. Absorption was corrected for by multi-scan methods (SADABS; Bruker, 2016 ▸).

	(I)	(II)	(III)
Crystal data
Chemical formula	C15H9N3O2	C16H11N3O2	C15H8ClN3O2
M r	263.25	277.28	297.69
Crystal system, space group	Monoclinic, P21/n	Monoclinic, P21/n	Monoclinic, P21/c
a, b, c (Å)	11.6814 (5), 6.4310 (3), 16.0589 (8)	7.5676 (5), 20.2663 (14), 9.2503 (7)	11.0993 (8), 12.8996 (9), 9.2234 (6)
β (°)	100.687 (2)	112.957 (3)	106.675 (2)
V (Å3)	1185.47 (10)	1306.33 (16)	1265.04 (15)
μ (mm−1)	0.10	0.10	0.31
Crystal size (mm)	0.20 × 0.12 × 0.06	0.28 × 0.17 × 0.16	0.20 × 0.12 × 0.05
Data collection
T min, T max	0.936, 0.994	0.941, 0.985	0.895, 0.985
No. of measured, independent and observed [I > 2σ(I)] reflections	26237, 2747, 2400	36209, 3242, 2915	28194, 2905, 2495
R int	0.037	0.034	0.044
(sin θ/λ)max (Å−1)	0.652	0.668	0.650
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.036, 0.103, 1.04	0.036, 0.098, 1.05	0.032, 0.089, 1.08
No. of reflections	2747	3242	2905
No. of parameters	181	191	190
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.31, −0.21	0.31, −0.25	0.32, −0.36