Related Experiment Video
Updated: Dec 16, 2025

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
Published on: December 27, 2018
Near Infrared Phosphorescent Dinuclear Ir(III) Complex Exhibiting Unusually Slow Intersystem Crossing and Dual
Marsel Z Shafikov1,2, Andrey V Zaytsev3, Alfiya F Suleymanova4
1Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstrasse 31, Regensburg D-93053, Germany.
Abstract:
A dinuclear iridium(III) complex IrIr shows dual emission consisting of near infrared (NIR) phosphorescence (λmax = 714 nm, CH2Cl2, T = 300 K) and green fluorescence (λmax = 537 nm). The NIR emission stems from a triplet state (T1) localized on the ditopic bridging ligand (3LC). Because of the dinuclear molecular structure, the phosphorescence efficiency (ΦPL = 3.5%) is high compared to those of other known red/NIR-emitting iridium complexes. The weak fluorescence stems from the lowest excited singlet state (S1) of 1LC character. The occurrence of fluorescence is ascribed to relatively slow intersystem crossing (ISC) from state S1 (1LC) to the triplet manifold. The measured ISC rate corresponds to a time constant τISC of 2.1 ps, which is an order of magnitude longer than those usually found for iridium complexes. This slow ISC rate can be explained in terms of the LC character and large energy separation (0.57 eV) of the respective singlet and triplet excited states. IrIr is internalized by live HeLa cells as evidenced by confocal luminescence microscopy.
More Related Videos
Related Concept Videos
Photoluminescence: Applications
Photoluminescence: Fluorescence and Phosphorescence
A pair of electrons in a...
Variables Affecting Phosphorescence and Fluorescence
Fluorescence and Phosphorescence: Instrumentation
Total Internal Reflection Fluorescence Microscopy
IR Absorption Frequency: Hybridization
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that...

