Sensitive luminescence mechanochromism and unique luminescence thermochromism tuned by bending the P-O-P skeleton in the diphosphonium/iodocuprate(I) hybrid

Two new copper(i) iodide-based hybrids, i.e. (Py3P-O-PPy3)(Cu2I4) (1) and (Py3P-O-PPy3)(Cu4I6) (2) (Py = pyrrolidine), have been prepared, in which the tripodal diphosphonium (Py3P-O-PPy3)(2+) is in situ generated in the one-pot synthesis. The disordered (Cu4I6)(2-) tetramers are rare with two sets of tetracuprate centers. Interestingly, 1 exhibits sensitive luminescence mechanochromism, which is ascribed to the disturbed cuprophilic Cu...Cu interactions and the crystalline packing adjustment by destroying C-H...I hydrogen bonds during mechanical force. In particular, the luminescence thermochromism is unique, whose fluorescence intensity is strengthened with the elevated temperature. This could be due to the S-2-S-1 internal conversion on the linear P-O-P backbone, which will be bent upon heating. Simultaneous luminescence thermo/mechanochromism can also be monitored in 1. However, no luminescence thermo/mechanochromic performances can be detected in 2, so the luminescence thermo/mechanochromism of 1 could be quenched with DMF. The conclusions in this work might provide a new large-scale synthesis strategy for intelligent responsive luminescent materials.

Automated summary

Two new copper(I) iodide-based hybrids have been synthesized, one of which exhibits sensitive luminescence mechanochromism and unique luminescence thermochromism.