Preparation and Properties of (C₄H₉NH₃)₂EuI₄: A Luminescent Organic−Inorganic Perovskite with a Divalent Rare-Earth Metal Halide Framework

(C 4 H 9 NH 3 ) 2 EuI 4 has been prepared through the low-temperature solid-state reaction between C 4 H 9 NH 2 ·HI and EuI 2, providing the first example of a layered organic−inorganic perovskite with a divalent rare-earth metal in the perovskite sheets. The orthorhombic lattice parameters for the new compound, a = 8.913(3) Å, b = 8.759(3) Å, and c = 27.793(6) Å, refined from powder X-ray diffraction data, are similar to those previously observed for the family (C 4 H 9 NH 3 ) 2 MI 4 (M = Ge, Sn, Pb). The measured europium paramagnetic moment, 7.8(1) μ b, is consistent with the expected 8 S 7/2 ground state for nominally isolated divalent europium ions. There is no evidence for magnetic ordering of these ions over the temperature range 1.8−300 K. Strong blue photoluminescence is observed at 460(1) nm, a wavelength that is red-shifted approximately 10 nm relative to that for the more three-dimensional perovskite structures CsEuI 3 and CH 3 NH 3 EuI 3 . Thermal analysis indicates that, in an inert atmosphere, (C 4 H 9 NH 3 ) 2 EuI 4 undergoes bulk decomposition at temperatures above 290 °C.