Mixed lanthanide coordination polymers for temperature sensing and enhanced NdIII NIR luminescence

Abstract

Three LnIII coordination polymers, [Ln2L3(NO3)3]n·2CH3COOCH2CH3 (Ln = Nd (Nd2L3), Eu (Eu2L3), Tb (Tb2L3)), following coordination-assembly reactions involving a new bi-monodentate salicylamide ligand, L = 1,4-bis[(2΄-thenylaminoformyl)phenoxyl]methyl}-benzene, have been successfully synthesized. Among them, Nd2L3 and Tb2L3 were structurally authenticated by single-crystal X-ray diffraction and the results indicate both Nd2L3 and Tb2L3 are one-dimensional corrugated blockchains with LnIII containing 64-membered block loops filled by ethyl acetate molecules alternating in nearly orthogonal directions. For they are isomorphous, two binary co-doped lanthanide coordination polymers, Tb0.965Eu1.035L3 and Tb0.717Nd1.283L3 are obtained. Luminescent studies indicate that Tb0.965Eu1.035L3 exhibits a temperature recognition property with the significantly high sensitivity of 2.61% per K in the 296–386 K temperature range upon excitation at 345 nm as well as white emission when excited in the range of 370–390 nm. Tb0.717Nd1.283L3 shows enhanced NdIII-centred NIR luminescence and diminished TbIII-centred luminescence as compared to those of Nd2L3 and Tb2L3. The results presented herein show that the energy transfer from TbIII to both EuIII and NdIII has been successfully achieved in Tb0.965Eu1.035L3 and Tb0.717Nd1.283L3. Generally speaking, this work explores the potential applications of lanthanide-based coordination polymers based on multi-monodentate salicylamide ligand in the area of thermal sensing.