Ramya A R, Varughese Sunil, Reddy M L P
CSIR - Network of Institutes for Solar Energy, National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR), Thiruvananthapuram-695 019, India.
Dalton Trans. 2014 Jul 28;43(28):10940-6. doi: 10.1039/c4dt00871e.
Herein, we have developed a series of isostructural mixed Ln(3+)-4-(dipyridin-2-yl)aminobenzoate coordination polymers [Ln(3+) = Eu(3+) (1), Tb(3+) (2), and Gd(3+) (3)], and characterized and investigated their photophysical properties. The results demonstrated that by gently tuning the excitation wavelength of these mixed lanthanide complexes, white light emission can be realized with the Commission Internationale de I'Eclairage coordinates (0.32, 0.34). Furthermore, by changing the concentration profiles of lanthanide ions stoichiometrically in mixed-lanthanide complexes and exciting at particular wavelengths, various emission colours can also be successfully obtained. The antenna ligand, 4-(dipyridin-2-yl)aminobenzoic acid, provides an efficient energy transfer for the sensitization of Eu(3+) and Tb(3+) complexes and exhibits red and green emissions, respectively. Most importantly, due to the high energy (32,150 cm(-1)) of the Gd(3+) ion lowest-lying emission level, the corresponding Gd(3+) complex displays ligand-centered visible emission in the blue light region, and hence it acts as a blue emitter. Therefore, Eu(3+) and Tb(3+) complexes in conjunction with a Gd(3+) complex is a suitable choice to obtain tunable white-light-emission from Ln(3+) coordination polymers. The morphological analyses of the mixed lanthanide coordination polymers by transmission electron microscopy (TEM) disclose that these compounds exist as unique crystalline nano-rods with an average diameter of 200 nm. The developed mixed lanthanide complexes also exhibit high thermal stability (~420 °C).
在此，我们合成了一系列同构的混合Ln(3+)-4-(二吡啶-2-基)氨基苯甲酸配位聚合物[Ln(3+) = Eu(3+) (1)、Tb(3+) (2)和Gd(3+) (3)]，并对其进行了表征和光物理性质研究。结果表明，通过微调这些混合镧系配合物的激发波长，可以实现国际照明委员会坐标为(0.32, 0.34)的白光发射。此外，通过化学计量改变混合镧系配合物中镧系离子的浓度分布，并在特定波长下激发，也可以成功获得各种发射颜色。天线配体4-(二吡啶-2-基)氨基苯甲酸为Eu(3+)和Tb(3+)配合物的敏化提供了有效的能量转移，并分别呈现红色和绿色发射。最重要的是，由于Gd(3+)离子最低激发态能级的能量较高(32,150 cm(-1))，相应的Gd(3+)配合物在蓝光区域呈现以配体为中心的可见发射，因此它作为蓝色发射体。因此，Eu(3+)和Tb(3+)配合物与Gd(3+)配合物相结合是从Ln(3+)配位聚合物中获得可调谐白光发射的合适选择。通过透射电子显微镜(TEM)对混合镧系配位聚合物进行的形态分析表明，这些化合物以平均直径为200 nm的独特结晶纳米棒形式存在。所合成的混合镧系配合物还表现出高的热稳定性(约420 °C)。
