Windmill-like ZnII-LnIII heterometallic compounds emited from visible to near infrared region

Considering the fascinating structural feature and special electronic property of heterometallic compounds, it is highly desirable but challenging to develop heterometallic species with excellent optical outputs. To this end, five ZnII-LnIII heterometallic compounds with the chemical composition of [Zn2Ln2(HL)2L2(NO3)4]∙xCH3OH∙yCH3CN∙zH2O (Zn2Ln2, LnIII = PrIII, NdIII, GdIII, TbIII and ErIII) based on ligand H2L, where 3-methoxysalicylamide and phenyl-substituted pyrazoloneimide are spaced by propylidene, have been developed. Single crystal analysis demonstrate that the new family of heterometallic compounds are all windmill-like ZnII-LnIII heterometallic species, where two fully deprotoned ligands L2− with μ3-η1:η1:η1:η2:η1 coordination mode in enol form and two partly deprotoned ligands HL− with μ2-η1:η1:η2 coordination mode in keto form are anchored by two ZnII and two LnIII ions. The luminescence studies indicate that the ZnII-L2−-HL− chromophore acts as a good antenna for sensitizing the visible emission of TbIII and near infraed emission of PrIII, NdIII and ErIII ions effectively as the result of its well matched triplet state. Experimental and computational studies on the energy level of the ZnII-incorporated antenna are performed for validating the energy transfer efficiency in these ZnII-LnIII heterometallic compounds. The results presented herein has important significance for the development of structural novel and luminescent ZnII-LnIII heterometallic compounds with wide emission ranges.