Unique anisotropic optical properties of a highly stable metal–organic framework based on trinuclear iron(III) secondary building units linked by tetracarboxylic linkers with an anthracene core

A highly stable metal–organic framework, [{Fe3(ACTBA)2}X·6DEF]n (1; X = monoanion), based on trinuclear iron(III) secondary building units connected by tetracarboxylates with an anthracene core, 2,6,9,10-tetrakis(p-carboxylatophenyl)anthracene (ACTBA), is reported. Depending on the direction of light polarisation, crystals of 1 exhibit anisotropic optical properties with birefringence Δn = 0.3 (λ = 590 nm)