Structure and isomerization in N,N-dimethyl-l,3-propanediamine nickel(II) thiocyanate

Abstract

Abstract The complex [NiL2(NCS)2] (1), L = N,N-dimethyl-l,3-propanediamine, exhibits thennochromic solid state phase transition (temperature range 383 K–397.5 K) producing a high temperature isomer [NiL2(NCS)2] (2). The crystal structure of (2) has been solved by the X-ray powder as well as single crystal data sets and the precision of the structure determined with the X-ray single crystal diffraction data is higher than that obtained from the powder diffraction data. The triclinic unit cell of (2) having a volume approximately double to that of (1) consists of two symmetrically independent octahedral [NiL2(NCS)2] complexes with the metal atoms lying at (0 0 0) and (0 1/2 1/2), respectively. The equatorial planes around the two metal centers in isomer (2) are inclined to each other by 155.8(2)°. With the decrease of the specific volume per molecule of [NiL2(NCS)2] on isomerization (1 → 2) and significant changes in the molecular packing of the two isomers (1) and (2), the possible way of phase transition (1 → 2) is through a break up of the crystal body of isomer (1) and recrystallization into isomer (2).