<p>Molecular conductance junctions are configurations in which individual molecules facilitate electron transport between two macroscopic electrodes, with anchor groups serving as critical interfaces that modulate transmission characteristics and charge transport efficiency. Most previous studies on ferrocene-based junctions have focused on conductance switching, redox-dependent transport, or the stability and contact resistance of junctions with single anchoring groups. This work presents a theoretical investigation of the thermoelectric characteristics of a molecular junction consisting of a ferrocene pendant unit attached to a central anchoring group, which bridges two gold electrodes via anchor linkages, including pyridine (PY), thiolate (S), methyl sulfide (SMe), and thiophene (BT). The ferrocene unit (Fe sandwiched between two cyclopentadienyl rings) participates in electron transport through the molecular junction. The unique contribution of this work lies in the systematic analysis of how anchor group variation independently modulates transmission characteristics, energy level alignment, and electrode coupling strength in ferrocene-based molecular junctions. The results demonstrate that these anchors produce transmission minima with varying magnitudes depending on their connectivity. Furthermore, the Fermi energy level can be tuned to align with HOMO (highest occupied molecular orbital) or LUMO (lowest unoccupied molecular orbital) resonances based on anchor group identity, enabling the thermopower to switch between positive and negative values. In direct correspondence with these findings, the conductance magnitude exhibits a systematic ordering based on the functional linker employed, following the sequence <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$G_{S} > G_{SMe} > G_{BT} > G_{PY}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>G</mi> <mi>S</mi> </msub> <mo>></mo> <msub> <mi>G</mi> <mrow> <mi mathvariant="italic">SMe</mi> </mrow> </msub> <mo>></mo> <msub> <mi>G</mi> <mrow> <mi mathvariant="italic">BT</mi> </mrow> </msub> <mo>></mo> <msub> <mi>G</mi> <mrow> <mi mathvariant="italic">PY</mi> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation>. Conversely, the Seebeck coefficients exhibit inverse ordering <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\left| {S_{Py} } \right|$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close="|" open="|"> <msub> <mi>S</mi> <mrow> <mi mathvariant="italic">Py</mi> </mrow> </msub> </mfenced> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$> \left| {S_{BT} } \right| > \left| {S_{SMe} } \right| > \left| {S_{S} } \right|$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>></mo> <mfenced close="|" open="|"> <msub> <mi>S</mi> <mrow> <mi mathvariant="italic">BT</mi> </mrow> </msub> </mfenced> <mo>></mo> <mfenced close="|" open="|"> <msub> <mi>S</mi> <mrow> <mi mathvariant="italic">SMe</mi> </mrow> </msub> </mfenced> <mo>></mo> <mfenced close="|" open="|"> <msub> <mi>S</mi> <mi>S</mi> </msub> </mfenced> </mrow> </math></EquationSource> </InlineEquation>, consistent with the fundamental relationship between the conductance <InlineEquation ID="IEq4"> <EquationSource Format="TEX">${\text{(G}})$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>(G</mtext> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and Seebeck coefficient <InlineEquation ID="IEq5"> <EquationSource Format="TEX">${\text{(S}})$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>(S</mtext> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>.</p>

Theoretical Investigation of Anchoring Variations in Single Molecule Junctions and Their Impact on Thermoelectric Properties

期刊论文
发表日期：

2026年4月13日

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Ohood Albeydani

摘要

Molecular conductance junctions are configurations in which individual molecules facilitate electron transport between two macroscopic electrodes, with anchor groups serving as critical interfaces that modulate transmission characteristics and charge transport efficiency. Most previous studies on ferrocene-based junctions have focused on conductance switching, redox-dependent transport, or the stability and contact resistance of junctions with single anchoring groups. This work presents a theoretical investigation of the thermoelectric characteristics of a molecular junction consisting of a ferrocene pendant unit attached to a central anchoring group, which bridges two gold electrodes via anchor linkages, including pyridine (PY), thiolate (S), methyl sulfide (SMe), and thiophene (BT). The ferrocene unit (Fe sandwiched between two cyclopentadienyl rings) participates in electron transport through the molecular junction. The unique contribution of this work lies in the systematic analysis of how anchor group variation independently modulates transmission characteristics, energy level alignment, and electrode coupling strength in ferrocene-based molecular junctions. The results demonstrate that these anchors produce transmission minima with varying magnitudes depending on their connectivity. Furthermore, the Fermi energy level can be tuned to align with HOMO (highest occupied molecular orbital) or LUMO (lowest unoccupied molecular orbital) resonances based on anchor group identity, enabling the thermopower to switch between positive and negative values. In direct correspondence with these findings, the conductance magnitude exhibits a systematic ordering based on the functional linker employed, following the sequence $G_{S} > G_{SMe} > G_{BT} > G_{PY}$ $G_{S} > G_{SMe} > G_{BT} > G_{PY}$ . Conversely, the Seebeck coefficients exhibit inverse ordering $\left| {S_{Py} } \right|$ $|S_{Py}|$ $> \left| {S_{BT} } \right| > \left| {S_{SMe} } \right| > \left| {S_{S} } \right|$ $> |S_{BT}| > |S_{SMe}| > |S_{S}|$ , consistent with the fundamental relationship between the conductance ${\text{(G}})$ $(G)$ and Seebeck coefficient ${\text{(S}})$ $(S)$ .