Screening polymorphism in a Ni(II) metal-organic framework: experimental observations, Hirshfeld surface analyses and DFT studies

A new polymorph of a 1D Ni(II) polymer with iminodiacetic acid (IDA), namely diaquaiminodiacetatonickel(II) [Ni(C4H5NO4)(H2O)(2)](n), is discovered one decade after the X-ray characterization of the other polymeric polymorph. The new polymorph (named form-II) is characterized by single-crystal X-ray diffraction, and its structural comparison with the previous polymorph (named form-I) is reported. The new form-II (space group Pbca) not only is a conformational polymorph, but it also exhibits packing polymorphism with the already known P2(1)ca crystal form of the polymer. The intermolecular interactions generate distinct packing features in the two forms. The present study reports a detailed analysis of Hirshfeld surfaces and fingerprint plots, facilitating a comparison of intermolecular interactions in the supramolecular architectures. Moreover, the differences in the H-bonding networks of the polymorphs have been analysed using a combination of density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) calculations.