Negative linear compression and expanding NH•••N bonds in an imidazoline compound

The 3-dimensional network of NH center dot center dot center dot N hydrogen bonds and Cl center dot center dot center dot Cl hydrogen contacts in the crystal structure of 2-(3'-chlorophenyl)imidazoline exhibits an anomalous hydrostatic compression. The lengthening of hydrogen bonds NH center dot center dot center dot N and some CH center dot center dot center dot N contacts as well as their supramolecular architecture lead to anomalous expansion of the crystal along [x] and [y] on increasing pressure to 0.1 GPa. The mechanism of this phenomenon is due to the 'stiffness' of the NH center dot center dot center dot N and Cl center dot center dot center dot Cl interactions and 'softness' of other van der Waals contacts. Above 0.1 GPa all crystal directions become compressed. However, up to 1.20 GPa, the crystal remains in the same orthorhombic phase of polar space group Fdd2.