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

(C4H9NH3)2EuI4 has been prepared through the low-temperature solid-state reaction between C4H9NH2·HI and EuI2, 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 (C4H9NH3)2MI4 (M = Ge, Sn, Pb). The measured europium paramagnetic moment, 7.8(1) μb, is consistent with the expected 8S7/2 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 CsEuI3 and CH3NH3EuI3. Thermal analysis indicates that, in an inert atmosphere, (C4H9NH3)2EuI4 undergoes bulk decomposition at temperatures above 290°C.