Phosphorescent Square‐Planar Platinum(II) Complexes of 1,3‐Bis(2‐pyridylimino)isoindoline with a Monodentate Strong‐Field Ligand

Abstract

AbstractA series of platinum(II) complexes bearing 1,3‐bis(2‐pyridylimino)isoindoline (BPI) derivatives as ligand have been prepared by substitution of the coordinated Cl in precursors [Pt(L)Cl] [L = L1 (1), L2 (2), L3 (3)] by a monodentate strong‐field ligand such as CN–, CN‐cyclohexyl, PPh3, NCS–, PhS–, or N(CN)2–. Most of these compounds display orange‐to‐red luminescence in both the solid state and solution at ambient temperature. Compared with precursors 1–3, both low‐energy absorption and emission bands in ligand‐substituted platinum(II) complexes 4–13 exhibit distinct blueshifts. The emission of platinum(II) complexes with CN‐containing monodentate ligands shows progressive blueshifts with increasing ligand field strength: 609 (10, NCS–) → 603 [12, N(CN)2–] → 590 (4, CN–) → 581 nm (7, C≡N‐cyclohexyl). The emission of complexes 4–9 originates mainly from the 3[π → π*(BPI)] 3IL triplet excited state, mixed with some 3[dπ(Pt) → π*(BPI)] 3MLCT character. In contrast, the emission of 10–13 arises from a clearly increased 3[π(L) → π*(BPI)] 3LLCT state with reduced 3[π → π*(BPI)] 3IL and 3[5d(Pt) → π*(BPI)] 3MLCT character. Noticeably, dicyanamido‐linked dinuclear complex 13 displays a significant ligand–ligand electronic interaction between the two BPI across the Pt–N≡C–N–C≡N–Pt bridge with remarkable LLCT character from one BPI to the other.