Dhara Barun, Kumar Vikash, Gupta Kriti, Jha Plawan Kumar, Ballav Nirmalya
Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune 411008, India.
ACS Omega. 2017 Aug 14;2(8):4488-4493. doi: 10.1021/acsomega.7b00931. eCollection 2017 Aug 31.
Electrically conductive metal-organic coordination polymers (CPs) are promising candidates for a variety of technological applications. However, poor energetic and spatial overlap between the -electrons of organic ligands and the -electrons of metal ion often blocks an effective charge transport (mobility) across CPs. Herein, we present a bimetallic design principle for enhancing carrier mobility in CPs. Bimetallic CPs of Fe(III) and Cr(III) ions coordinated to 1,3,5-benzenetricarboxylic acid (BTC) ligand (Fe-BTC-Cr) exhibited remarkably high carrier mobility at the matching mole ratio (1:1) with enhancement factors of 10 and 10 in comparison to those of monometallic parents, Fe-BTC and Cr-BTC, respectively. The observation was substantiated by lowering of the band gap between the valence band and the conduction band upon the formation of a hybrid --type structure in the bimetallic CPs. The direct current conductivity values of the CPs measured by four-probe technique were in good agreement with the alternating current conductivity values obtained from the electrochemical impedance spectroscopy. Our flexible approach of picking and choosing the appropriate combination of metal ions from the periodic table is expected to generate various CPs with desirable semiconducting properties.
导电金属有机配位聚合物（CPs）是多种技术应用中很有前景的候选材料。然而，有机配体的π电子与金属离子的π电子之间能量和空间重叠不佳，常常阻碍电荷在CPs中有效传输（迁移率）。在此，我们提出一种用于提高CPs中载流子迁移率的双金属设计原则。与1,3,5-苯三甲酸（BTC）配体配位的Fe(III)和Cr(III)离子的双金属CPs（Fe-BTC-Cr）在匹配摩尔比（1:1）下表现出极高的载流子迁移率，与单金属母体Fe-BTC和Cr-BTC相比，增强因子分别为10倍和10倍。在双金属CPs中形成杂化π-π*型结构时，价带和导带之间的带隙降低，证实了这一观察结果。通过四探针技术测量的CPs的直流电导率值与从电化学阻抗谱获得的交流电导率值高度一致。我们从元素周期表中挑选合适金属离子组合的灵活方法，有望生成具有理想半导体性质的各种CPs。
