Luminescent [(2-PBO)CuILP] complexes: Synthesis, crystal structures, properties, and TD-DFT calculation

We report herein a series of new [(2-PBO)CuIL_P] type luminescent complexes 1–6 and their application in fluorescent VOCs detection. These CuI complexes (except 1 as CuBr) are constructed by a diimine ligand 2-PBO (2-(2′-pyridyl)-benzoxazole) and five P-containing ligands (L_P) PPh₃ (1–2), PPh₂Cy (3), o-Tol₃P (4), TXP24 (5), and TXP25 (6), where PPh₃ = triphenylphosphine, PPh₂Cy = 4-cyclohexyldiphenylphosphine, o-Tol₃P = 4-tri(o-tolyl)-phosphine, TXP24 = tris(2,4-xylyl)phosphine, and TXP25 = tris(2,5-xylyl)phosphine. All complexes exhibit isolated structures with tetrahedral CuIN₂P coordination. TD-DFT calculations assign their low-energy UV absorption band to a mixed (XL + ML)CT¹ transition from Cu-I fragment to 2-PBO, the similarly assigned (XL + ML)CT excited state is proposed as the source of photoluminescence (PL). The modification of phosphine ligands is found to have minimal impact on the PL properties of these materials. A thin-film sensor based on complex 2 was fabricated, achieving VOCs detection through remarkable PL enhancement and vapochromism behavior.