Table 3. Experimental details.

	(I)	(II)
Crystal data
Chemical formula	C18H11Br2N3O4	C18H11Cl2N3O4
M r	493.1	404.2
Crystal system, space group	Monoclinic, P21/c	Monoclinic, P21/c
Temperature (K)	100	100
a, b, c (Å)	13.4705 (7), 11.6686 (6), 11.7081 (7)	13.3117 (3), 11.5460 (3), 11.7558 (3)
β (°)	107.576 (2)	108.7971 (10)
V (Å3)	1754.39 (17)	1710.46 (7)
Z	4	4
Radiation type	Mo Kα	Mo Kα
μ (mm−1)	4.65	0.41
Crystal size (mm)	0.80 × 0.56 × 0.20	0.76 × 0.65 × 0.35
Data collection
Diffractometer	Bruker KAPPA APEXII CCD	Bruker KAPPA APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2013 ▸)	Multi-scan (SADABS; Bruker, 2013 ▸)
T min, T max	0.055, 0.390	0.74, 0.87
No. of measured, independent and observed [I > 3σ(I)] reflections	52187, 7731, 5557	29061, 4959, 4374
R int	0.045	0.031
(sin θ/λ)max (Å−1)	0.808	0.704
Refinement
R[F 2 > 3σ(F 2)], wR(F 2), S	0.034, 0.079, 1.36	0.034, 0.131, 1.39
No. of reflections	7731	4959
No. of parameters	244	244
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	1.00, −0.91	0.24, −0.23

Computer programs: APEX2 and SAINT-Plus (Bruker, 2013 ▸), SUPERFLIP (Palatinus & Chapuis, 2007 ▸), JANA2006 (Petříček et al., 2014 ▸), Mercury (Macrae et al., 2008 ▸) and publCIF (Westrip, 2010 ▸).