PPh3H2SbCl5: A Zero-Dimensional Hybrid Metal Halide with a Supramolecular Framework and Stable Dual-Band Emission

Zero-dimensional (0D) organic–inorganic metal halides (OIMHs) have attracted tremendous attention due to their fascinating optoelectronic properties. Herein, we report an antimony(III)-based 0D OIMH of PPh3H2SbCl5 comprising discrete SbCl52– pyramids and protonated triphenylphosphine (PPh3H) cations with a low charge density. Abundant supramolecular interactions including C–H···Cl and rare P–H···Cl hydrogen bonds and C–H···Π and anion···Π interactions lead to a three-dimensional (3D) supramolecular framework structure of PPh3H2SbCl5. Photophysical characterizations indicate that PPh3H2SbCl5 has singlet/triplet dual-band emission. The intersystem crossing between the single and triplet states is tunable upon changing the temperature. Analyses of the Huang–Rhys factor (S), exciton activation energy (Ea), and electron–phonon coupling energy (Γop) verify that the soft lattice and strong electron–phonon coupling result in the broad emission of PPh3H2SbCl5, while the excited-state reorganization of the SbCl52– pyramid leads to a large Stokes shift. DFT calculations help provide a deep understanding on the optical property of PPh3H2SbCl5. The title compound could remain stable for more than 1 year without the obvious decay of emission, which may be related to the rigid 3D supramolecular framework.