Materials exhibiting reversible changes of their photoluminescence properties upon exposure to heat have an immense potential in various advanced photonic applications. Particularly, the control over an on‐demand response of thermochromic luminescent materials (TLMs) similar to a chameleon is of great importance. However, it is still difficult and challenging to achieve it. Therefore, this paper reports a simple and effective way to construct TLMs, which involves the incorporation of the metal–ligand complexes into polyethylene glycol (PEG). Ratiometric or off–on response modes of these TLMs can be tuned by incorporating metal complexes based on either Zn2+ or Co2+ into PEG and by taking advantage of reversible metal–ligand coordination, dissociation, or excited‐state conformation changes of the resulting materials. Moreover, by choosing PEG matrices with different molecular weights, the thermochromic transition temperatures of these TLMs can be tuned. It is also demonstrated that the controllable response behavior of these chameleon‐like TLMs can be used in applications related to real‐life anti‐counterfeiting and security printing. This work opens novel opportunities for the development of smart materials with controllable responses useful for advanced photonic applications.

Luminescent materials with tunable emission lifetimes have gained broad research interest, because they are ideal candidates for optical multiplexing applications, such as biolabeling, security printing, and data storage. To date, a few studies have reported that the efficient regulation of emission decay times can be achieved for lanthanide nanomaterials. However, it remains challenging to engineer the luminescence lifetimes of small molecules due to the lack of effective methods. Herein, a new strategy is put forward to control the emission lifetimes of ionic Cu(I) complexes by changing the electrostatic interactions between cationic complexes and counter anions. The Cu(I) complexes prepared with different counterions (ClO4−, PF6−, NO3−, and BF4−) exhibit distinct luminescence lifetimes from 12.9 to 22.3 µs in the solid state. Importantly, by simply doping different contents of CuBF4 into polymethyl methacrylate, the emission lifetimes could be varied in a linear manner in the range from 11.4 ± 0.3 to 20.7 ± 0.2 µs. Based on the tunable emission lifetimes, optical multiplexing is achieved by using time‐resolved luminescence imaging technique.

In this study, a soft salt complex based photosensitizer has been developed for photodynamic therapy (PDT) of cancer cells. The iridium(iii) complex [Ir(L)(L')]3+(PF6-)3 (C1) with L and L' being terpyridine ligands (L = 4'-phenyl-2,2':6',2''-terpyridine, L' = 3-([2,2':6',2''-terpyridin]-4'-yl)-9-hexyl-9H-carbazole) was chosen as the cationic component, and the iridium(iii) complex [Ir(dfppy)2CN2]-Bu4N+ (A1) was selected as the anionic component. Complexes C1 and A1 are directly connected through electrostatic interaction to form a soft salt based photosensitizer (S1), which exhibited an enhanced singlet oxygen generation rate because of efficient energy transfer between two ionic metal complexes. Furthermore, this novel photosensitizer was successfully applied in photodynamic therapy (PDT) of cancer cells for the first time.

In this study, a soft salt complex based probe has been exploited for measuring oxygen content changes in living cells. The zinc(II) complex [Zn(tpy) 2 ] 2+ (CH 3 COO -) 2 {tpy = 3-[(2,2′:6′,2′′-terpyridin)-4′-yl]-9-hexyl-9H-carbazole} was chosen as the cationic component, and the iridium(III) complex [Ir(tpq) 2 CN 2 ] -Bu 4 N + [tpq = 2-(thiophen-2-yl)quinoline] was selected as the anionic component. The soft salt complex based [a]