A new kinetically preferable polymorph of 1-(4’- cyanobenzyl)pyridinium bis(maleonitriledithiolato)nickelate with spin-Peierls type transition

A new kinetically preferable polymorph of 1-(4’-cyanobenzyl)pyridinium bis(maleonitriledithiolato)nickelate (β-[CN-Py][Ni(mnt)2]) was achieved and characterized by element microanalysis for C, H and N elements, powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) techniques. β-[CN-Py][Ni(mnt)2] shows a magnetostructural phase transition together with a thermal anomaly at ~192 K. In high-temperature phase (HTP), the β-[CN-Py][Ni(mnt)2] crystal belongs to monoclinic space group P21/c, and its asymmetric unit is comprised of one pair of CN-Py+ and [Ni(mnt)2]− ions. Both CN-Py+ and [Ni(mnt)2]− ions form uniform columnar stacks, respectively. In low-temperature phase (LTP), the space group of the crystal is lowered to triclinic P-1, its asymmetric unit changes into two pairs of anions and cations, moreover, both stacks of CN-Py+ and [Ni(mnt)2]− ions are dimerized. β-[CN-Py][Ni(mnt)2] features an S = ½ Heisenberg regular antiferromagnetic (AFM) linear chain system with │J│= 86(9) K in HTP...