Mechanochromic luminescence properties of fluoro-substituted pinene-containing cyclometalated platinum(II) complexes with multiple triplet excited states.

The structure-mechanochromism relationship is explored with respect to packing patterns and corresponding intermolecular interactions that are affected by the number and location of -F. The distinct and reversible mechanochormic luminescence (Δλem up to ca. 90 nm) of yellow solids (-)-1-Yg, (-)-2-Yg, and (-)-3-Yg was displayed with a simultaneous crystal-to-amorphous transformation. The change of multiple triplet excited states accounted for the mechanochormic luminescence, and a switch from the 3π,π* monomer to the excimer/3MMLCT occurred in the grinding process. The mechanical force led to perturbation in the molecular packing, and aggregates with effective PtPt and π-π interactions were formed in the amorphous phase, leading to the variation of excited states. The mechanochromic luminescence could be reverted by dropping in CH2Cl2 and could be cycled multiple times without perceivable performance degradation. This work gives a reference for designing mechanochromic luminescent materials toward multicolor and multicomponent responses.

Enhanced Circularly Polarized Luminescence Activity in Chiral Platinum(II) Complexes With Bis- or Triphenylphosphine Ligands.

Distinct circularly polarized luminescence (CPL) activity was observed in chiral (C∧N∧N)Pt(II) [(C∧N∧N) = 4,5-pinene-6'-phenyl-2,2'-bipyridine] complexes with bis- or triphenylphosphine ligands. Compared to the pseudo-square-planar geometry of chiral (C∧N∧N)Pt(II) complexes with chloride, phenylacetylene (PPV) and 2,6-dimethylphenyl isocyanide (Dmpi) ligands, the coordination configuration around the Pt(II) nucleus of chiral (C∧N∧N)Pt(II) complexes with bulk phosphine ligands is far more distorted. The geometry is straightforwardly confirmed by X-ray crystallography. The phosphines' participation enhanced the CPL signal of Pt(II) complexes profoundly, with the dissymmetry factor (g lum) up to 10-3. The distorted structures and enhanced chiroptical signals were further confirmed by time-dependent density functional theory (TD-DFT) calculations.

PtPt interaction triggered tuning of circularly polarized luminescence activity in chiral dinuclear platinum(ii) complexes.

Circularly polarized luminescence (CPL) activity switched by PtPt interaction is disclosed in two couples of dinuclear Pt(ii) complex enantiomers. Upon varying the length of the bridging ligand, intramolecular metal-metal interaction manipulation is achieved as evidenced from crystal structures. Complex (-)-1 exhibiting strong PtPt interaction displays red phosphorescence with a maximum peak at 638 nm, while complex (-)-2 exhibiting weak PtPt interaction displays green phosphorescence with a maximum peak at 530 nm. The observed CPL was opposite in sign for the two complexes. TD-DFT simulations further confirmed the influence of the PtPt distance on the difference in the electronic optical activities.