Zwitterionic Mixed-Valence Species for the Design of Neutral Clocked Molecular Quantum-Dot Cellular Automata

Abstract

Mixed-valence compounds can be used for the design of molecular quantum-dot cellular automata (QCA). Here, we investigate the QCA properties of a three-dot "Y"-shaped functionalized zwitterionic neutral closo-carborane model 1-(3,5-{Cp(dHpe)Fe−CC−} 2 (C 6 H 3 ))-10-Cp(dHpe)Fe−CC-closo-1-CB 9 H 8 (1) (Cp = cyclopentadienyl (η 5 -C 5 H 5 ) and dHpe = 1,2-bis(phosphino)ethane (H 2 PCH 2 CH 2 PH 2 )) as a neutral clocked molecular half-cell. DFT results clearly demonstrate that 1 can display simultaneously the two most basic properties necessary for clocked QCA operation, i.e., bistable switching behavior and clocked control. This is possible due to the three stable states (two active and one null) of 1, corresponding to occupation of each of the three iron-ethynyl groups by the positive charge. In addition, the proximal electronic bias effects can be overcome by the zwitterionic nature of 1, which could be imposed by external counterions, rendering these effects more predictable.

Unravelling of a [High Spin—Low Spin] ↔ [Low Spin—High Spin] Equilibrium in Spin‐Crossover Iron(II) Dinuclear Helicates Using Paramagnetic NMR Spectroscopy

“…[16,17] The combination of two such molecules may result in a conventional class II QCA cell of Robin-Day classification [39] for signal transmission, inversion and logic operations. [40] In contrast to molecular mixed-valence compounds, which make use of Coulomb repulsion as the driving force of the QCA bistability, [41,42] SCO-active species would instead require a careful analysis of their vibronic structure [43] and magnetic interactions between the adjacent cells. [44] Regardless of the nature of individual states of metal ions, if they are envisaged for putative double-dot QCA for information storage and processing, a fast equilibrium [HS-LS]  [LS-HS] would result in their detrimental scrambling unless it can be slowed down by external factors, which is achievable in the solid state by crystal packing effects.…”

Exploring the potential as molecular quantum-dot cellular automata of a mixed-valence Ru2 complex deposited on a Au(111) surface

“…In fact, the electric-field driven electron-transfer in mixed valence molecules has been experimentally demonstrated 18,20,33,58,59 and theoretically simulated in different MV systems. 11,21,28,[60][61][62][63] Other aspects, out of the scope of this work, have to be considered for practical applications of mQCA cells in energy gain and power dissipation, state latching, tunnelling effects, clocked QCA, etc. 57,64,65 Fig.…”

Unravelling of a [High Spin—Low Spin] ↔ [Low Spin—High Spin] Equilibrium in Spin‐Crossover Iron(II) Dinuclear Helicates Using Paramagnetic NMR Spectroscopy

“…The combination of two such molecules may result in a conventional class II QCA cell of Robin‐Day classification [39] for signal transmission, inversion and logic operations [40] . In contrast to molecular mixed‐valence compounds, which make use of Coulomb repulsion as the driving force of the QCA bistability, [41, 42] SCO‐active species would instead require a careful analysis of their vibronic structure [43] and magnetic interactions between the adjacent cells [44] . Regardless of the nature of individual states of metal ions, if they are envisaged for putative double‐dot QCA for information storage and processing, a fast equilibrium [HS‐LS] ↔ [LS‐HS] would result in their detrimental scrambling unless it can be slowed down by external factors, which is achievable in the solid state by crystal packing effects [20, 21, 24] .…”