Porphyrins and porphyrinic compounds are used as building blocks in organic electronic devices, such as switches, memories, spectroscopic markers, solar cells, sensors, tailored molecular catalysts, engineered molecular nanostructures or molecular spintronics [1]. Despite this fact, much of the work reported in the literature is on large areas of porphyrinoid self-assembled monolayers, whereas few molecular- or nanoscale-level studies have been reported [1]. Recently, in view of exploiting single molecule properties, research has focused interest on the intra-molecular physicochemical processes of porphyrins, such as the tautomer mechanism [2]. Tautomerization in free base porphyrins - a process involving the exchange of two inner protons between the nitrogen atoms - has been extensively studied at very low temperatures, where this chemical reaction is not active anymore. However, the conditions needed for a stable tautomer clearly represent a severe drawback for obtaining a charge storage for electronic applications [2]. Recently we obtained a genuine single porphyrin (H2TPP) layer through an unconventional film growth [3]. Atomic force microscopy (AFM), scanning tunneling microscopy (STM) and reflectance anisotropy spectroscopy (RAS) experiments in combination with density functional theory (DFT) simulations of STM profiles and the tautomerization path prove that, even at room temperature, tautomerization is not active in this system [3]. Further studies of the optical response using more sophisticated calculations (the GWBSE approach) fully support our findings of a macroscopically anisotropic layer [4]. On this basis we are able to propose a new way of exploiting uniaxially oriented H2TPP tautomers in a first elementary logic device prototype. [1] M. Jurow, A.E. Schuckman, J.D. Batteas, C.M. Drain, Coord. Chem. Rev. 254 (2010), 19. [2] W. Auwärter et al., Nature Nanotech. 7 (2011) 41. [3] G. Bussetti, M. Campione, M. Riva, A. Picone, L. Raimondo, L. Ferraro, C. Hogan, M. Palummo, A. Brambilla, M. Finazzi, L. Duò, A. Sassella, and F. Ciccacci, Advanced Functional Materials 24 (2014) 958. [4] G. Bussetti, M. Campione, L. Ferraro, L. Raimondo, B. Bonanni, C. Goletti, M. Palummo, C. Hogan, L. Duò, M. Finazzi, A. Sassella, Journal of Physical Chemistry C (submitted) (2014)
2-D layers of porphyrin tautomers: STM, optics, and ab initio simulations
Conor Hogan
2014
Abstract
Porphyrins and porphyrinic compounds are used as building blocks in organic electronic devices, such as switches, memories, spectroscopic markers, solar cells, sensors, tailored molecular catalysts, engineered molecular nanostructures or molecular spintronics [1]. Despite this fact, much of the work reported in the literature is on large areas of porphyrinoid self-assembled monolayers, whereas few molecular- or nanoscale-level studies have been reported [1]. Recently, in view of exploiting single molecule properties, research has focused interest on the intra-molecular physicochemical processes of porphyrins, such as the tautomer mechanism [2]. Tautomerization in free base porphyrins - a process involving the exchange of two inner protons between the nitrogen atoms - has been extensively studied at very low temperatures, where this chemical reaction is not active anymore. However, the conditions needed for a stable tautomer clearly represent a severe drawback for obtaining a charge storage for electronic applications [2]. Recently we obtained a genuine single porphyrin (H2TPP) layer through an unconventional film growth [3]. Atomic force microscopy (AFM), scanning tunneling microscopy (STM) and reflectance anisotropy spectroscopy (RAS) experiments in combination with density functional theory (DFT) simulations of STM profiles and the tautomerization path prove that, even at room temperature, tautomerization is not active in this system [3]. Further studies of the optical response using more sophisticated calculations (the GWBSE approach) fully support our findings of a macroscopically anisotropic layer [4]. On this basis we are able to propose a new way of exploiting uniaxially oriented H2TPP tautomers in a first elementary logic device prototype. [1] M. Jurow, A.E. Schuckman, J.D. Batteas, C.M. Drain, Coord. Chem. Rev. 254 (2010), 19. [2] W. Auwärter et al., Nature Nanotech. 7 (2011) 41. [3] G. Bussetti, M. Campione, M. Riva, A. Picone, L. Raimondo, L. Ferraro, C. Hogan, M. Palummo, A. Brambilla, M. Finazzi, L. Duò, A. Sassella, and F. Ciccacci, Advanced Functional Materials 24 (2014) 958. [4] G. Bussetti, M. Campione, L. Ferraro, L. Raimondo, B. Bonanni, C. Goletti, M. Palummo, C. Hogan, L. Duò, M. Finazzi, A. Sassella, Journal of Physical Chemistry C (submitted) (2014)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
