High cross-plane thermoelectric performance of metallo-porphyrin molecular junctions

Abstract

aWe investigated the thermoelectric properties of flat-stacked 5,15-diphenylporphyrins containing divalent metal ions Ni, Co, Cu or Zn, which are strongly coordinated with the nitrogens of pyridyl coated gold electrodes. Changing metal atom has little effect on the thermal conductance due to the phonons.The room-temperature Seebeck coefficients of these junctions are rather high, ranging from 90 mV K À1for Cu, Ni and Zn-porphyrins to À16 mV K À1 for Co-porphyrin. These values could be further increased by lowering molecular energy levels relative to the DFT-predicted Fermi energy. In contrast, the phonon contribution to the thermal conductance of these junctions is rather insensitive to the choice of metal atom. The thermopower, thermal conductance and electrical conductance combined to yield the room-temperature values for the thermoelectric figure of merit ZT ranging from 1.6 for Cu porphyrin to B0.02 for Ni-porphyrin.

Molecular-scale thermoelectricity: as simple as ‘ABC’

“…To address the problem of increasing the thermoelectric performance of organic molecules, Finch et al 10 demonstrated theoretically that large values of the Seebeck coefficient could be obtained by creating transport resonances and anti-resonances within the HOMO-LUMO gap and tuning their energetic location relative to the Fermi energy. Following these pioneering works, several experimental [11][12][13][14][15][16][17][18][19][20] and theoretical studies [21][22][23][24][25][26][27][28][29][30][31][32][33][34] have attempted to probe and improve the thermoelectric performance of single molecules. However, progress has been hampered by the additional complexity of thermoelectric measurement set-ups, because unlike measurements of single-molecule conductance, Seebeck measurements require additional control and determination of temperature gradients at a molecular scale.…”

Thermal and Thermoelectric Properties of Molecular Junctions

“…They further demonstrate such transmission system can operate with large power output and efficiencies close to the Curzon–Ahlborn limit. Noori et al recently investigated the influence of metal ions on the thermoelectric properties of flat‐stacked 5,15‐diphenylporphyrins containing divalent metal ions Ni, Co, Cu or Zn. Their calculations show that changing the metal atom has little effect on the thermal conductance due to the phonons, while the room‐temperature Seebeck coefficients of these junctions are high, ranging from 90 µV K −1 for Cu, Ni, and Zn‐porphyrins to −16 µV K −1 for Co‐porphyrin.…”

Binding Mode of Cationic Porphyrin with CT-DNA: Importance of the Location and the Number of Positively Charged of Periphery Cationic Ions of Porphyrin

“…Porphyrins have been used to develop artificial receptors that are used to recognize molecules 12 and to develop new chiral catalysts for asymmetric synthesis. 13−15 They have also been used to explore biologically important response mechanisms such as photosynthesis 16 and P450 catalyst 17 oxidation–reduction reactions as well as stereochemical research. Porphyrins are also considered as attractive molecules in many respects.…”

“…Ethidium bromide, acridine orange, methylene blue, Ru­(II) complex, porphyrin, and small molecules are often used to understand the structure and properties of DNA through their interactions with drug–DNA and protein–DNA. − The study of the interaction between porphyrins and DNA is continuously gaining interest. Porphyrins have been used to develop artificial receptors that are used to recognize molecules and to develop new chiral catalysts for asymmetric synthesis. − They have also been used to explore biologically important response mechanisms such as photosynthesis and P450 catalyst oxidation–reduction reactions as well as stereochemical research. Porphyrins are also considered as attractive molecules in many respects.…”