Photochromic and photocontrolled luminescent rare-earth D-A hybrid crystals based on rigid viologen acceptors

As an emerging class of hybrid complexes, the donor-acceptor (D-A) hybrid crystals containing photoactive organic and inorganic components have gradually become an ideal platform for constructing photochromic materials in recent years. In order to investigate the effect of D-A interactions on photochromic properties, three novel hybrid crystals, [Eu-2(NO3)(2)(cbp-I)(4)(H2O)(8)][Co(CN)(6)](NO3)center dot 6H(2)O center dot CH3OH (1), [Eu(NO3)(2)(cbp-I)(2)(H2O)(3)](NO3)center dot 3H(2)O (2), and (cbp-II)(cbp-III)[Co(CN)(6)]center dot 7H(2)O (3), have been designed and synthesized. They all exhibit reversible eye-detectable color changes with different photoresponsive speeds: the photoresponse speeds are 1 > 3 > 2. This result can be attributed to the introduction of effective electron-transfer channels through combining [Co(CN)(6)](3-) as an electron donor with viologen acceptors in 1 and 3, in comparison to 2. Moreover, accompanied with the interesting photochromic process, these unique hybrid compounds simultaneously possess a photomodulated luminescent behaviour. The luminescent intensity of 2 is far greater than that of the other two compounds, and 2 shows high sensitivity towards 4-nitroaniline with a very small LOD of ca. 9.78 x 10(-7) M.

Automated summary

This study investigated the effect of D-A interactions on photochromic properties by designing and synthesizing three novel hybrid crystals. These hybrids exhibit reversible eye-detectable color changes with varying photoresponsive speeds, with compound 1 showing the fastest response and compound 2 the slowest. The introduction of effective electron-transfer channels in compoud 3, which combines [Co(CN)6]3- as an electron donor with viologen acceptors, results in a more significant electronic donor-acceptor structure compared to the other two compounds.