A PN(Pz)P ligand protected Au2Cu2 complex for photoluminescent ultra-low humidity detection with reversible single-crystal-to-single-crystal transformations

Reliable and sensitive detection of sub-ppm level, ultra-low humidity is critical for a number of important technologies. We herein report the reaction of a P/N hybrid ligand 3-dppmapz-1-ol with Au(I) and Cu(I) salts resulting in a heteronuclear Au2Cu2 cluster complex [Au2Cu2(3-dppmapz)(2)](PF6) (2)center dot 4MeOH (1 center dot 4MeOH) that undergoes reversible single-crystal-to-single-crystal (SCSC) transformations into analogues 1 and 1 center dot 2H(2)O. The photoluminescent emission of 1 center dot 2H(2)O at 625 nm shifted to 617 nm within 24 h and 622 nm after 65 h in P2O5 dried air, and returned to green in MeOH/H2O or MeOH/EtOH vapour. Crystals of 1 could rapidly detect ultralow humidity of 0.21 ppm (w/w).

Automated summary

Reliable and sensitive detection of sub-ppm level, ultra-low humidity is critical for a number of important technologies. We report a heteronuclear Au2Cu2 cluster complex that can undergo reversible transformations and has photoluminescent properties in different environments. The crystals of the complex can detect ultralow humidity of 0.21 ppm (w/w).