Bis(1,2,3-trimethylindenyl)iron(III) 2,3-Dicyanonaphtho-1,4-quinonide, a Non-Metallocene, Charge-Transfer Salt Metamagnet with Complementary Donor−Acceptor Geometries

Bis(1,2,3-trimethylindenyl)iron(III) can be paired with 2,3-dicyanonaphtho-1,4-quinone to give an air-stable π-stacked metamagnet with T_c = 4.1 K, the first example of a non-metallocene CT salt magnet in this class. A single crystal X-ray structure of the Fe(1,2,3-Me₃C₉H₄)₂[DCNQ] salt indicates that it consists of stacks of alternating donors and acceptors, in which the DCNQ ring systems are aligned with indenyl groups above and below, and the long axes of the DCNQ and the indenyl ligand are parallel to each other. This arrangement suggests that the magnetic properties arise from favorable interactions due to geometric similarities between the donor and acceptor, and not from a unique property of the donor itself.