On the importance of antiparallel π–π interactions in the solid state of isatin-based hydrazides Muhammad Naeem Ahmed, a Maryam Arif, a Farah Jabeen, a Haroon Ahmed Khan, a Khawaja Ansar Yasin a , Muhammad Nawaz Tahir b , Antonio Franconetti c and Antonio Frontera c* a Department of Chemistry, The University of Azad Jammu and Kashmir, Muzaffarabad, 13100, Pakistan b Department of Physics, University of Sargodha, Sargodha, Pakistan c Department de Quimica, Universitat de les Illes Balears, Crta. De Valldemossa km 7.5, 07122 Palma de Mallorca (Baleares), Spain (Z)-N'-(2-oxo-1-propylindolin-3-ylidene) benzohydrazide (7) Crystal data C 18 H 17 N 3 O 2 F(000) = 648 M r = 307.34 D x = 1.289 Mg m −3 Monoclinic, P2 1 /c Mo Kα radiation, λ = 0.71073 Å a = 7.167 (2) Å Cell parameters from 1636 reflections b = 24.911 (9) Å θ = 2.4–26.0° c = 8.898 (3) Å µ = 0.09 mm −1 β = 94.712 (14)° T = 296 K V = 1583.3 (9) Å 3 Needle, yellow Z = 4 0.40 × 0.25 × 0.22 mm Data collection Bruker Kappa APEXII CCD diffractometer 3095 independent reflections Radiation source: fine-focus sealed tube 1636 reflections with I > 2σ(I) Graphite monochromator R int = 0.060 Detector resolution: 0.78 pixels mm - 1 θ max = 26.0°, θ min = 2.4° ω scans h = −9→9 Absorption correction: multi-scan (SADABS; Bruker, 2005) k = −32→29 Electronic Supplementary Material (ESI) for New Journal of Chemistry. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019