The molecular and supramolecular aspects in mononuclear manganese(iii) Schiff-base spin crossover complexes

Shi Wang; Ya-Juan Li; Fei-Fei Ju; Wu-Tan Xu; Koichi Kagesawa; Yong-Hua Li; Masahiro Yamashita; Wei Huang

doi:10.1039/c7dt01718a

The molecular and supramolecular aspects in mononuclear manganese(iii) Schiff-base spin crossover complexes

Dalton Trans. 2017 Aug 22;46(33):11063-11077. doi: 10.1039/c7dt01718a.

Authors

Shi Wang¹, Ya-Juan Li, Fei-Fei Ju, Wu-Tan Xu, Koichi Kagesawa, Yong-Hua Li, Masahiro Yamashita, Wei Huang

Affiliation

¹ Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Jiangsu National Synergistic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, Nanjing 210023, China. iamswang@njupt.edu.cn.

PMID: 28792029
DOI: 10.1039/c7dt01718a

Abstract

Manganese(iii) hexadentate Schiff base complexes ([Mn(sal-N-1,5,8,12)]Y·S, Y = AsF₆ (1); Y = SbF₆ (2); Y = NO₃, S = C₂H₅OH (3) and Y = Cl (4)) have been investigated to determine the impact of anion effects, intramolecular ligand distortions, and intermolecular supramolecular structures on the spin crossover (SCO) behavior. The crystal structure of [Mn(sal-N-1,5,8,12)]PF₆, a complex known to exhibit an abrupt SCO behavior with an 8 K hysteresis window, reveals that this complex has a temperature-dependent anion order-disorder transition that disrupts the hydrogen-bonding chain upon SCO, indicating that hydrogen bonds between cations and anions greatly influence the magnetic properties. The SCO in 1 is mediated by intermolecular hydrogen-bonding interactions. The subtle balance of these hydrogen bonds induces a cooperative SCO process with a hysteresis width of 18 K, which is the largest one reported in the d⁴ SCO chemistry. For 2, crystal structural analysis indicates that changing the anion from AsF₆^- to SbF₆^- led to close stackings between phenyl groups from ligands. These stackings preclude the spin transition of the [Mn(sal-N-1,5,8,12)]⁺ cations. With NO₃^- and Cl^- as counterions, the [Mn(sal-N-1,5,8,12)]⁺ cations are arranged more loosely and exhibit gradual SCO in the temperature range of 300-100 K. Careful evaluation of the supramolecular structures of these complexes and similar complexes reported previously revealed strong correlation between the supramolecular packing forces and their magnetic properties.