Abstract
The tetrapyridyl ligand bbpya (bbpya=N,N-bis(2,2'-bipyrid-6-yl)amine) and its mononuclear coordination compound [Fe(bbpya)(NCS)(2)] (1) were prepared. According to magnetic susceptibility, differential scanning calorimetry fitted to Sorai's domain model, and powder X-ray diffraction measurements, 1 is low-spin at room temperature, and it exhibits spin crossover (SCO) at an exceptionally high transition temperature of T-1/2=418 K. Although the SCO of compound 1 spans a temperature range of more than 150 K, it is characterized by a wide (21 K) and dissymmetric hysteresis cycle, which suggests cooperativity. The crystal structure of the LS phase of compound 1 shows strong N-H center dot center dot center dot S intermolecular H-bonding interactions that explain, at least in part, the cooperative SCO behavior observed for complex 1. DFT and CASPT2 calculations under vacuum demonstrate that the bbpya ligand generates a stronger ligand field around the iron(II) core than its analogue bapbpy (N,N'-di(pyrid-2yl)-2,2'-bipyridine-6,6'-diamine); this stabilizes the LS state and destabilizes the HS state in 1 compared with [Fe(bapbpy)( NCS)(2)] (2). Periodic DFT calculations suggest that crystal-packing effects are significant for compound 2, in which they destabilize the HS state by about 1500 cm(-1). The much lower transition temperature found for the SCO of 2 compared to 1 appears to be due to the combined effects of the different ligand field strengths and crystal packing.
Original language | English |
---|---|
Pages (from-to) | 331-339 |
Number of pages | 9 |
Journal | Chemistry |
Volume | 22 |
Issue number | 1 |
DOIs | |
Publication status | Published - 4-Jan-2016 |
Keywords
- cooperative effects
- hydrogen bonds
- iron
- ligand design
- spin crossover
- WIDE THERMAL HYSTERESIS
- ROOM-TEMPERATURE
- TRANSITION-TEMPERATURE
- PERFORMANCE
- VALIDATION
- CHEMISTRY
- INTERPLAY
- POLYMERS
- LIGANDS
- SYSTEMS
Datasets
-
CCDC 1019880: Experimental Crystal Structure Determination
Zheng, S. (Contributor), Reintjens, N. R. M. (Contributor), Siegler, M. A. (Contributor), Roubeau, O. (Contributor), Bouwman, E. (Contributor), Rudavskyi, A. (Contributor), Havenith, R. (Contributor) & Bonnet, S. (Contributor), University of Groningen, 18-Aug-2014
DOI: 10.5517/cc1378cz
Dataset