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Cossaboon TA, Kazmi S, Tineo M, Hoy EP. Assessing the importance of multireference correlation in predicting reversed conductance decay. Phys Chem Chem Phys 2024; 26:6696-6707. [PMID: 38321937 DOI: 10.1039/d3cp01110k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
In a classical electronic resistor, conductance decays as the device length increases according to Ohm's Law. While most molecular series display a comparable exponential decay in conductance with increasing molecular length, a class of single-molecule device series exists where conductance instead increases with molecular/device length, a phenomenon called reversed conductance decay. While reversals of conductance decay have been repeatedly theoretically predicted, they have been far more difficult to demonstrate experimentally. Previous studies have suggested that theoretical multi-reference(static) correlation errors may be a major cause of this discrepancy, yet most single-molecule transport methods are unable to treat multireference correlation. Using our unique multireference transport method based on non-equilibrium Green's function and multiconfigurational pair-density functional theory (NEGF-MCPDFT), we examined a previously predicted case of reversed conductance decay in systems of linear chains of phenyl rings with varying lengths and electrode designs. We compare our NEGF-MCPDFT results to those of non-multireference NEGF methods to quantify the exact role of static correlation in conductance decay reversals and clarify their relative importance to geometric and electrode design/coupling considerations.
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Affiliation(s)
- Tanner A Cossaboon
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.
| | - Samir Kazmi
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.
| | - Matthew Tineo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.
| | - Erik P Hoy
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.
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Bajaj A, Ali ME. Anti-ohmic nanoconductors: myth, reality and promise. Phys Chem Chem Phys 2023; 25:9607-9616. [PMID: 36942699 DOI: 10.1039/d3cp00366c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
The recent accomplishment in the design of molecular nanowires characterized by increasing conductance with length has led to the origin of an extraordinary new family of molecular junctions referred to as "anti-ohmic" wires. Herein, this highly desirable, non-classical behavior, has been examined for molecules long-enough to exhibit pronounced diradical character in their ground state within the unrestricted DFT formalism with spin symmetry breaking. We demonstrate that highly conjugated acenes signal higher resistance in an open-shell singlet (OSS) configuration as compared to their closed-shell counterparts. This anomaly has been further proven for experimentally certified cumulene wires, which reveals phenomenal modulation in the transport characteristics such that an increasing conductance is observed in the closed-shell limit, while higher cumulenes in the OSS ground state yield regular decay of conductance.
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Affiliation(s)
- Ashima Bajaj
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab-140306, India.
| | - Md Ehesan Ali
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab-140306, India.
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Li L, Louie S, Evans AM, Meirzadeh E, Nuckolls C, Venkataraman L. Topological Radical Pairs Produce Ultrahigh Conductance in Long Molecular Wires. J Am Chem Soc 2023; 145:2492-2498. [PMID: 36689781 DOI: 10.1021/jacs.2c12059] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Molecular one-dimensional topological insulators (1D TIs), which conduct through energetically low-lying topological edge states, can be extremely highly conducting and exhibit a reversed conductance decay, affording them great potential as building blocks for nanoelectronic devices. However, these properties can only be observed at the short length limit. To extend the length at which these anomalous effects can be observed, we design topological oligo[n]emeraldine wires using short 1D TIs as building blocks. As the wire length increases, the number of topological states increases, enabling an increased electronic transmission along the wire; specifically, we show that we can drive over a microampere current through a single ∼5 nm molecular wire, appreciably more than what has been observed in other long wires reported to date. Calculations and experiments show that the longest oligo[7]emeraldine with doped topological states has over 106 enhancements in the transmission compared to its pristine form. The discovery of these highly conductive, long organic wires helps overcome a fundamental hurdle to implementing molecules in complex, nanoscale circuitry: their structures become too insulating at lengths that are useful in designing nanoscale circuits.
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Affiliation(s)
- Liang Li
- Department of Chemistry, Columbia University, New York, New York10027, United States
| | - Shayan Louie
- Department of Chemistry, Columbia University, New York, New York10027, United States
| | - Austin M Evans
- Department of Chemistry, Columbia University, New York, New York10027, United States
| | - Elena Meirzadeh
- Department of Chemistry, Columbia University, New York, New York10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, New York10027, United States
| | - Latha Venkataraman
- Department of Chemistry, Columbia University, New York, New York10027, United States.,Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York10027, United States
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Research Progress on Triarylmethyl Radical-Based High-Efficiency OLED. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27051632. [PMID: 35268732 PMCID: PMC8911689 DOI: 10.3390/molecules27051632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/17/2022]
Abstract
Perchlorotrityl radical (PTM), tris (2,4,6-trichlorophenyl) methyl radical (TTM), (3,5-dichloro-4-pyridyl) bis (2,4,6 trichlorophenyl) methyl radical (PyBTM), (N-carbazolyl) bis (2,4,6-trichlorophenyl) methyl radical (CzBTM), and their derivatives are stable organic radicals that exhibit light emissions at room temperature. Since these triarylmethyl radicals have an unpaired electron, their electron spins at the lowest excited state and ground state are both doublets, and the transition from the lowest excited state to the ground state does not pose the problem of a spin-forbidden reaction. When used as OLED layers, these triarylmethyl radicals exhibit unique light-emitting properties, which can increase the theoretical upper limit of the OLED’s internal quantum efficiency (IQE) to 100%. In recent years, research on the luminescent properties of triarylmethyl radicals has attracted increasing attention. In this review, recent developments in these triarylmethyl radicals and their derivatives in OLED devices are introduced.
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Sand AM, Malme JT, Hoy EP. A multiconfiguration pair-density functional theory-based approach to molecular junctions. J Chem Phys 2021; 155:114115. [PMID: 34551556 DOI: 10.1063/5.0063293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Due to their small size and unique properties, single-molecule electronics have long seen research interest from experimentalists and theoreticians alike. From a theoretical standpoint, modeling these systems using electronic structure theory can be difficult due to the importance of electron correlation in the determination of molecular properties, and this electron correlation can be computationally expensive to consider, particularly multiconfigurational correlation energy. In this work, we develop a new approach for the study of single-molecule electronic systems, denoted NEGF-MCPDFT, which combines multiconfiguration pair-density functional theory (MCPDFT) with the non-equilibrium Green's function formalism (NEGF). The use of MCPDFT with NEGF allows for the efficient inclusion of both static and dynamic electron correlations in the description of the junction's electronic structure. Complete active space self-consistent field wave functions are used as references in the MCPDFT calculation, and as with any active space method, effort must be made to determine the proper orbital character to include in the active space. We perform conductance and transmission calculations on a series of alkanes (predominantly single-configurational character) and benzyne (multiconfigurational character), exploring the role that active space selection has on the computed results. For the alkane junctions explored (where dynamic electron correlation dominates), the MCPDFT-NEGF results agree well with the DFT-NEGF results. For the benzyne junction (which has a significant static correlation), we see clear differences in the MCPDFT-NEGF and DFT-NEGF results and evidence that NEGF-MCPDFT is capturing additional electron correlation effects beyond those provided by the Perdew-Burke-Ernzerhof functional.
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Affiliation(s)
- Andrew M Sand
- Department of Chemistry and Biochemistry, Butler University, Indianapolis, Indiana 46208, USA
| | - Justin T Malme
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, New Jersey 08028, USA
| | - Erik P Hoy
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, New Jersey 08028, USA
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Ortega P, Gil-Guerrero S, Veselinova A, Zanchet A, González-Sánchez L, Jambrina PG, Sanz-Sanz C. Multi- and single-reference methods for the analysis of multi-state peroxidation of enolates. J Chem Phys 2021; 154:144303. [PMID: 33858147 DOI: 10.1063/5.0046906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In spite of being spin-forbidden, some enzymes are capable of catalyzing the incorporation of O2(Σg-3) to organic substrates without needing any cofactor. It has been established that the process followed by these enzymes starts with the deprotonation of the substrate forming an enolate. In a second stage, the peroxidation of the enolate formation occurs, a process in which the system changes its spin multiplicity from a triplet state to a singlet state. In this article, we study the addition of O2 to enolates using state-of-the-art multi-reference and single-reference methods. Our results confirm that intersystem crossing is promoted by stabilization of the singlet state along the reaction path. When multi-reference methods are used, large active spaces are required, and in this situation, semistochastic heat-bath configuration interaction emerges as a powerful method to study these multi-configurational systems and is in good agreement with PNO-LCCSD(T) when the system is well-represented by a single-configuration.
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Affiliation(s)
- P Ortega
- Departamento de Química-Física, University of Salamanca, Salamanca 37008, Spain
| | - S Gil-Guerrero
- Departamento de Química-Física, University of Salamanca, Salamanca 37008, Spain
| | - A Veselinova
- Departamento de Química-Física, University of Salamanca, Salamanca 37008, Spain
| | - A Zanchet
- Instituto de Física Fundamental (CSIC), Madrid 28006, Spain
| | - L González-Sánchez
- Departamento de Química-Física, University of Salamanca, Salamanca 37008, Spain
| | - P G Jambrina
- Departamento de Química-Física, University of Salamanca, Salamanca 37008, Spain
| | - C Sanz-Sanz
- Departamento de Química Física Aplicada. Universidad Autónoma de Madrid, Madrid 28049, Spain
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