Xingtong Zhou, Xin-Ao Liu, Wendan Luo, Ke Liu^*, Taihong Liu^*, Liping Ding, Yu Fang. Chin. Chem. Lett., 2026, DOI: https://doi.org/10.1016/j.cclet.2026.112850

A primary objective of synthesizing novel organometallic complexes is to achieve tunable excited-state dynamics and superior nonlinear optical properties. This study systematically and comparatively investigated the mono- and bis-cyclometalated alkynylgold(III) complexes (Au-3T and Au-3T-Au). The quadrupolar Au-3T-Au exhibited a high two-photon absorption cross-section of 3980 GM at 560 nm, 6.8 times that of the dipolar analogue Au-3T, which was attributed to synergistic effect of ligand-to-ligand charge transfer and π-conjugation extension. Ultrafast excited-state dynamics revealed pronounced energetic and kinetic contrast in the underlying intramolecular charge transfer (ICT) and intersystem crossing (ISC) processes. Both complexes exhibited strong triplet-triplet absorption with microsecond-scale lifetimes. The synergistic ICT and efficient ISC effectively suppressed radiative energy loss, resulting in high photothermal conversion efficiencies. This work advances the understanding of intrinsic excited-state dynamics and high-performance photothermal applications in the cyclometalated alkynylgold(III) complexes.

Figure 1. (a) Combined 1PA and 2PA spectra of Au-3T-Au and related δ_2PA values in DCM (c = 1.0 × 10^-3 mol/L) excited at different fs-wavelengths within 530-850 nm. (b) Degenerate δ_2PA values of both complexes in DCM. (c) Normalized transmittance diagram of Au-3T-Au with different laser input values. (d) Compared state energies diagrams of the 1PA and 2PA processes for Au-3T-Au.

Figure 2. Related 2D contour plots and corresponding fs-TA spectra of (a) Au-3T and (b) Au-3T-Au excited at 410 nm in deaerated DCM. (c) ESA kinetics of Au-3T at 645 nm and Au-3T-Au at 770 nm. (d) Relative population profiles of the excited state species of Au-3T and Au-3T-Au reconstructed from global analysis.

First Author: Zhou Xingtong, Master’s student, Shaanxi Normal University

Correspondence Authors: Prof. Liu Taihong, Shaanxi Normal University; Prof. Liu Ke, Northwest A&F University

Full Text Link: https://doi.org/10.1016/j.cclet.2026.112850