Synthesis, Characterization and Hirshfeld Surface Analyses of Ni(mnt)-Alkyl Bisimidazolium Ion Pair Compounds: Supramolecular Interactions Mediated Self-Assembly

• A series of five new ion pair compounds have been synthesized from Ni(II) salts, Na 2 mnt and alkyl-bis(imidazolium) cations [C 8 H 12 (CH 2 ) n N 4 Br 2 ] (n = 1−5) by varying alkyl chain length. • The article highlights the role of planarity in Ni-dithiolene complexes under various supramolecular interactions • Hirshfeld surface analyses visualize the fidelity of alkyl chain length in cationic receptor towards the self-assembly of the compounds. A series of five new ion pair compounds with formulae [C 9 H 14 N 4 ][Ni(mnt) 2 ](CH 3 CN) ( 1a ), [C 10 H 16 N 4 ][Ni(mnt) 2 ] ( 1b ), [C 11 H 18 N 4 ][Ni(mnt) 2 ] ( 1c ), [C 12 H 20 N 4 ][Ni(mnt) 2 ] ( 1d ), [C 13 H 22 N 4 ][Ni(mnt) 2 ] ( 1e ) have been synthesized from Ni(II) salts, Na 2 mnt (disodium maleonitriledithiolate) and alkyl-bis(imidazolium) cations [C 8 H 12 (CH 2 ) n N 4 Br 2 ] (n = 1−5). All the compounds were characterized by IR, elemental analyses, UV, and electrochemical studies. The solid-state structures of these compounds were characterized by single crystal X-diffraction, facilitated by Hirshfeld surface analyses, to quantify the type and magnitude of various non-covalent interactions controlling the self-assembly. Various supramolecular interactions C-H cation •••N anion , C-H cation •••S anion and C-H•••π play a crucial role in modulating the conformations of cationic and anionic receptors as well as mediating the self-assembly. Hirshfeld surface analyses reveals that supramolecular packing is dominated by the directional interactions in lower chain cationic receptors whereas, non-directional interactions operate in longer chain cationic receptors. Absorption spectra reveals compound 1d exhibits absorption band (diffuse reflectance) at 910 nm whereas others at 860 nm. All the compounds show oxidative response in the region 0.48−0.56 V in the electrochemical studies. Additionally, the phase purity of the compounds were confirmed by the powder X-ray diffraction studies.