Control of Single-Molecule Junction Conductance of Porphyrins via a Transition-Metal Center

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• 作者：Zhen-Fei Liu ; Sujun Wei ; Hongsik Yoon ; Olgun Adak ; Ingrid Ponce ; Yivan Jiang ; Woo-Dong Jang ; Luis M. Campos ; Latha Venkataraman ; Jeffrey B. Neaton
• 刊名：Nano Letters
• 出版年：2014
• 出版时间：September 10, 2014
• 年：2014
• 卷：14
• 期：9
• 页码：5365-5370
• 全文大小：329K
• ISSN：1530-6992

文摘

Using scanning tunneling microscope break-junction experiments and a new first-principles approach to conductance calculations, we report and explain low-bias charge transport behavior of four types of metal鈥損orphyrin鈥揼old molecular junctions. A nonequilibrium Green鈥檚 function approach based on self-energy corrected density functional theory and optimally tuned range-separated hybrid functionals is developed and used to understand experimental trends quantitatively. Importantly, due to the localized d states of the porphyrin molecules, hybrid functionals are essential for explaining measurements; standard semilocal functionals yield qualitatively incorrect results. Comparing directly with experiments, we show that the conductance can change by nearly a factor of 2 when different metal cations are used, counter to trends expected from gas-phase ionization energies which are relatively unchanged with the metal center. Our work explains the sensitivity of the porphyrin conductance with the metal center via a detailed and quantitative portrait of the interface electronic structure and provides a new framework for understanding transport quantitatively in complex junctions involving molecules with localized d states of relevance to light harvesting and energy conversion.

Keywords:

Porphyrins and metalloporphyrins; single-molecule junction conductance; density functional theory; nonequilibrium Green鈥檚 function; self-energy correction; range-separated hybrid functional