Luminescent d-f transition Yb(Ⅱ)-containing azacryptates with high photoluminescence quantum yields

Emission tunable d-f transition lanthanide complexes have wide applications in many fields such as lighting and photoredox catalysis.Compared with Ce(Ⅲ)and Eu(Ⅱ)complexes,which have achieved near-unity photoluminescence quantum yields(PLQYs),Yb(Ⅱ)complexes still suffer from low reported PLQYs not exceeding 10%.In this work,two luminescent Yb(Ⅱ)-containing azacryptates YbI_(2)-N8M6(N8M6=4,7,13,16,21,24-hexamethyl-1,4,7,10,13,16,21,24-octaazabicyclo[8.8.8]hexacosane)and YbI2-N8E6(N8E6=4,7,13,16,21,24-hexaethyl-1,4,7,10,13,16,21,24-octaazabicyclo[8.8.8]hexacosane)were synthesized and characterized.YbI2-N8M6 in solid powder exhibits blue emission with a maximum emission wavelength(λm)of 464 nm and a PLQY of 76%,while YbI_(2)-N8E6 in solid powder exhibits green emission with a λ_(m) of 537 nm and a PLQY up to93%.Moreover,YbI_(2)-N8M6 exhibits mechanochromic property,showing an emission color change from deep-blue to cyan under mechanical grinding.These results will inspire the studies about luminescent Yb(Ⅱ)complexes and their further applications.