Enhanced emission of Nd3+ in liquid systems:: Formation of symmetrical rigid shells of tightly solvated DMSO molecules and weakly coordinated low-vibrational β-diketonato ligands

Coordination structures of neodymium(III) complexes with some beta-diketones were investigated in terms of their correlations with emission efficiency in deuterated dimethylsulfoxide (DMSO-d(6)). The analysis of UV-vis spectra, C-13 NMR, electrospray mass spectrometry (ES-MS) spectra, XANES and EXAFS analysis of tris(hexafluoroacetylacetonato)neodymium(III) complex, [Nd(hfa-H)(3)(H2O)(2)], and tris[bis(perfluorooctanoyl)methanato]neodymium(III), [Nd(pom-H)(3)], in DMSO indicated that the deuterated tris(hexafluoroacetylacetonato)neodymium(III), Nd(hfa-D)(3), and deuterated tris[bis(perfluorooctanoyl)methanato]neodymium(III) Nd(pom-D)(3), in DMSO-d(6) should have a symmetrical, rigid and bulky shell composed of six inner-coordinating DMSO molecules and three weakly coordinating hfa-D and pom-D molecules. The improvement in the emission efficiency of the neodymium complexes with the low vibrational and weakly coordinating beta-diketonates in DMSO-d(6) was ascribed to their symmetrical rigid coordination structures, which should suppress radiationless transition via vibrational excitation and energy migration in the fluid system.