Thermally controlling the singlet–triplet energy gap of a diradical in the solid state† †Electronic supplementary information (ESI) available: Crystallographic data in CIF formats, powder EPR spectra, crystal structures and theoretical calculation. CCDC 1430382 and 1430383. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc01825d Click here for additional data file. Click here for additional data file.

Table S1. Crystal data and structure refinement.......................................... ....................................S2 Figure S1. Powder EPR spectra of 1•2[Al(ORF)4] at various temperatures (120-170K)..............................S3 Figure S2. Powder EPR spectra of 1•2[Al(ORF)4] at various temperatures (190-290K)... ...........................S4 Figure S3. Powder EPR spectrum of 1•2[Al(ORF)4] at 123 K.............................................................S5 Figure S4. Powder EPR spectrum of 1•2[Al(ORF)4] at 200 K..... ........................................................S6 Figure S5. Powder EPR spectrum of 1•2[Al(ORF)4] at 290 K..... ........................................................S7 Figure S6. Packing diagram of 12+ at 200 K...................................................................................S8 Figure S7. Packing diagram of 12+ at 123 K...................................................................................S9