Excited state processes of dinuclear Pt(II) complexes bridged by 8-hydroxyquinoline

Area of Science:

• Inorganic Chemistry
• Photochemistry
• Materials Science

Background:

• Dinuclear d8 Pt(II) complexes with "A-frame" geometry exhibit unique photophysical properties.
• These properties are influenced by the distance between the two Pt(II) centers, leading to MLCT or MMLCT transitions.

Purpose of the Study:

• To synthesize and characterize novel dinuclear platinum(II) complexes using 8-hydroxyquinoline (8HQH) as a bridging ligand.
• To investigate the photophysical properties, specifically triplet ligand-centered (3LC) transitions, of these novel complexes.
• To correlate experimental findings with theoretical calculations.

Main Methods:

• Synthesis of dinuclear platinum(II) complexes [C^NPt(μ-8HQ)]2 (1, 2) and a mononuclear model [Pt(8HQ)2] (3).
• Spectroscopic analysis including UV-Vis absorption and photoluminescence measurements.
• Time-dependent density functional theory (TD-DFT) calculations for electronic structure and excited state analysis.

Main Results:

• Complexes 1 and 2, with Pt-Pt distances of ~3.25 Å, display lowest energy absorption around 480 nm with mixed LC/MLCT character.
• These complexes exhibit 3LC photoluminescence near 680 nm with low quantum yields (0.008).
• Photoexcitation leads to rapid relaxation to a long-lived 3LC excited state localized on the 8HQ bridge.

Conclusions:

• The synthesized dinuclear platinum(II) complexes exhibit 3LC photophysics similar to mononuclear analogues.
• The Pt-Pt distance significantly influences the photophysical properties, leading to mixed LC/MLCT absorption.
• Experimental results are consistent with DFT electronic structure calculations, validating the theoretical model.