Phosphorescent Zwitterionic Pt(II) N‐Heterocyclic Allenylidene Complexes: Metallophilicity and Ionic Self‐Assembly†

Abstract

Main observation and conclusionThree zwitterionic and one cationic N‐heterocyclic allenylidene (NHA) platinum(II) complexes were prepared and characterized via NMR, HR‐MS, and FT‐IR, etc. Single crystal structure analyses revealed the various intermolecular packing modes via multiple noncovalent interactions (short Pt···Pt contacts, π‐π interactions). The spectroscopic data demonstrated stability of the allenylidene metal complexes is largely ascribed to the resonance structures of zwitterionic acetylide. The zwitterionic and analogue cationic NHA Pt(II) monomers showed similar steady‐state photoluminescent properties in dilute fluid solution. Highly efficient solid‐state phosphorescent emissions (quantum yield up to 20%) of these NHA Pt(II) complexes are correlated with their dispersive metallophilic Pt···Pt interactions. HR‐MS spectrum indicated zwitterionic monomers can self‐assemble into oligomers, such as dimer, trimer and even hexamer in a mixed H2O/MeOH solvent. Meanwhile, molecular aggregates showed variable red‐shifted phosphorescence by manipulating the concentration, temperature, time and solvent in the self‐assembly of zwitterionic NHA platinum(II) complex.