Self-doping of molecular quantum-dot cellular automata: mixed valence zwitterions

Abstract

Molecular quantum-dot cellular automata (QCA) is a promising paradigm for realizing molecular electronics. In molecular QCA, binary information is encoded in the distribution of intramolecular charge, and Coulomb interactions between neighboring molecules combine to create long-range correlations in charge distribution that can be exploited for signal transfer and computation. Appropriate mixed-valence species are promising candidates for single-molecule device operation. A complication arises because many mixed-valence compounds are ions and the associated counterions can potentially disrupt the correct flow of information through the circuit. We suggest a self-doping mechanism which incorporates the counterion covalently into the structure of a neutral molecular cell, thus producing a zwitterionic mixed-valence complex. The counterion is located at the geometrical center of the QCA molecule and bound to the working dots via covalent bonds, thus avoiding counterion effects that bias the system toward one binary information state or the other. We investigate the feasibility of using multiply charged anion (MCA) boron clusters, specifically closo-borate dianion, as building blocks. A first principle calculation shows that neutral, bistable, and switchable QCA molecules are possible. The self-doping mechanism is confirmed by molecular orbital analysis, which shows that MCA counterions can be stabilized by the electrostatic interaction between negatively charged counterions and positively charged working dots.

Environmental decoherence stabilizes quantum-dot cellular automata

“…We assume that in addition to the mobile electronic charge, there are fixed neutralizing charges of þe/2 on each of the two dots. In the actual molecule, this neutralizing charge is either a donor center 13 or a counterion. 14,15 The model reflects the reality that molecular QCA cells have a nonzero dipole moment, but no net charge.…”

Synthesis of a Neutral Mixed‐Valence Diferrocenyl Carborane for Molecular Quantum‐Dot Cellular Automata Applications

“…[2,3] QCA relies on encoding binary information into quantum-dots or molecules by the location of an electron or hole ( Figure 1). [3,5] To overcome this limitation, we sought the preparation of an eutral mixed-valence compound where the counterion is incorporated as part of the ligand backbone.D espite substantial interests in electron transfer processes,v ery few neutral mixed-valence compounds have been fully studied. Proof-of-concept QCA experiments have been realized utilizing metallic nanometer-scale quantum-dots, [4] and our interest lies in extending this paradigm to the molecular realm.…”

Intra-molecular Electro-potential Circuit & ElectroNegatrode: Hypothesis, Algorithm & Implementation for universal indicative rule towards activity of biomolecules

“…Long range charge distribution for signal transfer was exploited with intramolecular charge distribution in neighboring objects. This study was concluded also into the cellular automata (Lu and Lent, 2011).…”