Bispo-Jr Airton G, Mazali Italo O, Sigoli Fernando A
Department of Inorganic Chemistry, Institute of Chemistry, University of Campinas, Unicamp, Josué de Castro Street, Cidade Universitária, Campinas, 13083-970, Brazil.
Phys Chem Chem Phys. 2022 Jun 8;24(22):13565-13570. doi: 10.1039/d2cp01851a.
Ln complexes may display luminescence within the ultraviolet-visible-near-infrared spectral window and although they render bright emissions mainly due to the classical singlet-triplet-state-assisted ligand sensitization, which would be the photophysical parameters if they could be excited through direct spin-forbidden singlet → triplet transitions? Herein, we report the sensitization of Ln complexes through spin-forbidden S → T transitions in a series of homobimetallic Eu, Tb, Er, and Yb complexes with halogen-substituted benzoate ligands. As halogens and Ln atomic numbers increase, intense singlet → triplet absorption/excitation bands and relative quantum yields up to 18% were achieved due to an increased spin-orbit coupling effect. Moreover, the near-UV-shifted excitation may enable application in luminescent solar concentrators where Yb near-infrared luminescence matches the maximum efficiency of the crystalline Si photovoltaic cell. Therefore, the spin-relaxed excitation channel provides new opportunities to improve the Ln complex luminescence and potential within the energy conversion field.
镧系配合物可能在紫外-可见-近红外光谱窗口内显示发光，尽管它们主要由于经典的单重态-三重态辅助配体敏化而发出明亮的发射光，但如果它们可以通过直接的自旋禁阻单重态→三重态跃迁被激发，光物理参数会是怎样的呢？在此，我们报道了在一系列含有卤素取代苯甲酸酯配体的同双核铕、铽、铒和镱配合物中，通过自旋禁阻的单重态→三重态跃迁实现镧系配合物的敏化。随着卤素和镧系原子序数的增加，由于自旋-轨道耦合效应增强，实现了强烈的单重态→三重态吸收/激发带以及高达18%的相对量子产率。此外，近紫外位移激发可能使镧系配合物应用于发光太阳能聚光器中，其中镱的近红外发光与晶体硅光伏电池的最大效率相匹配。因此，自旋弛豫激发通道为提高镧系配合物的发光性能以及在能量转换领域的潜力提供了新的机会。
