Co-crystallization of the prominent Fe( ii ) spin-crossover (SCO) cation, Fe(3-bpp) 2 2+ (3-bpp = 2,6-bis(pyrazol-3-yl)pyridine), with a fractionally charged TCNQ δ − radical anion has afforded a hybrid complex Fe(3-bpp) 2 (TCNQ) 3 ·5MeCN ( 1 ·5MeCN, where δ = −0.67). The partially desolvated material shows semiconducting behavior, with the room temperature conductivity σ RT = 3.1 × 10 −3 S cm −1 , and weak modulation of conducting properties in the region of the spin transition. The complete desolvation, however, results in the loss of hysteretic behavior and a very gradual SCO that spans the temperature range of 200 K. A related complex with integer-charged TCNQ − anions, Fe(3-bpp) 2 (TCNQ) 2 ·3MeCN ( 2 ·3MeCN), readily loses the interstitial solvent to afford desolvated complex 2 that undergoes an abrupt and hysteretic spin transition centered at 106 K, with an 11 K thermal hysteresis. Complex 2 also exhibits a temperature-induced excited spin-state trapping (TIESST) effect, upon which a metastable high-spin state is trapped by flash-cooling from room temperature to 10 K. Heating above 85 K restores the ground-state low-spin configuration. An approach to improve the structural stability of such complexes is demonstrated by using a related ligand 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) to obtain Fe(bzimpy) 2 (TCNQ) 6 ·2Me 2 CO ( 4 ) and Fe(bzimpy) 2 (TCNQ) 5 ·5MeCN ( 5 ), both of which exist as LS complexes up to 400 K and exhibit semiconducting behavior, with σ RT = 9.1 × 10 −2 S cm −1 and 1.8 × 10 −3 S cm −1 , respectively. Co-crystallization of the cationic complex Fe(3-bpp)2 2+ with fractionally charged TCNQ δ − anions (0 < δ < 1) affords semiconducting spin-crossover (SCO) materials. The abruptness of SCO is strongly dependent on the interstitial solvent content.