The synthesis of a new 3-ethynylthienyl-substituted QsalH ligand (QsalH is the short form for N-(8-
quinolyl)salicylaldimine) (ThEQsalH 3), and the preparation, electronic, and magnetic properties of three homoleptic
and cationic iron(3+) complexes containing this ligand with PF6
- 4, SCN- 5, and ClO4
- 6 counteranions are
reported. In all three complexes a spin-crossover is observed in the solid state by variable temperature magnetic
susceptibility measurements and Mo¨ssbauer spectroscopy, indicating that the synthetic modification of the QsalH
ligand has not significantly altered the electronics at the metal center. This includes the observation of a very rare
S ) 5/2 to 3/2 spin-crossover in a non-porphyrin iron(3+) complex 5. The molecular structure and magnetic
properties of an unusual iron(2+) complex 7 generated by reduction of complex 6 serendipitously during a
recrystallization attempt in aerobic acetone solution is also reported. Complexes 4-6 feature iron(3+) reduction
and oxidation of the thiophene ring at potentials of approximately -0.7 and +1.2 V (vs Fc), respectively.