Computational demonstration of isomer- and spin-state-dependent charge transport in molecular junctions composed of charge-neutral iron(II) spin-crossover complexes

rsc.li/dalton Dalton Transactions An international journal of inorganic chemistry rsc.li/dalton ISSN 0306-0012 COMMUNICATION Douglas W. Stephen et al. N-Heterocyclic carbene stabilized parent sulfenyl, selenenyl, and tellurenyl cations (XH+, X = S, Se, Te) Volume 46 Number 10 14 March 2017 Pages 3073-3412 Dalton Transactions An international journal of inorganic chemistry This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. Accepted Manuscript View Article Online View Journal This article can be cited before page numbers have been issued, to do this please use: N. Montenegro- Pohlhammer, S. K. Kuppusamy, G. Cardenas-Jiron, C. J. Calzado and M. Ruben, Dalton Trans., 2023, DOI: 10.1039/D2DT02598A. Computational demonstration of Isomer- and spin-state-dependent charge transport in molecular junctions composed of charge-neutral iron(II) spincrossover complexes Nicolás Montenegro-Pohlhammer,a,b* Senthil Kumar Kuppusamy,c* Gloria Cárdenas-Jirón,a Carmen J. Calzadob and Mario Rubenc,d,e aLaboratory of Theoretical Chemistry, Faculty of Chemistry and Biology, University of Santiago de Chile (USACH), 9170022, Santiago, Chile. bDepartamento de Química Física. Universidad de Sevilla. c/ Profesor García González, s/n. 41012 Sevilla. Spain. cInstitute of Quantum Materials and Technologies (IQMT), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany. dInstitute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany. eCentre Européen de Sciences Quantiques (CESQ), Institut de Science et d’Ingénierie Supramoléculaire (ISIS), Université de Strasbourg, Strasbourg, France. *Authors to whom the correspondence should be addressed Email: [email protected], [email protected]. Abstract Chemistry offers a multitude of opportunities towards harnessing functional molecular materials with application propensity. One emerging area of interest is molecular spintronics, in which charge and spin degrees of freedom are used to achieve power-efficient device architectures. Herein, we show that, with the aid of state-of-the-art quantum chemical calculations on designer molecular junctions, the conductance and spin filtering capabilities are determined by the molecular structure. As inferred from the calculations, structural control over the transport can be achieved by changing the position of the thiomethyl (SMe) anchoring groups for Au(111) electrodes in a set of isomeric 2,2`-bipyridine-based metal coordinating ligand entities L1 and L2. The computational studies on heteroleptic iron(II) coordination complexes (1 and 2) composed of L1 and L2 reveal that switching the spin-state of the iron(II) centers, from the low-spin (LS) to high-spin (HS) state, by means of an external electric field stimulus, could, in theory, be performed. Such switching, known as spin-crossover (SCO), renders charge transport through single-molecule junctions of 1 and 2 spin-state-dependent, and the HS junctions are more conductive than the LS junctions for both complexes. Additionally, the LS and HS junctions based on complex 1 are more conductive than those featuring complex 2. Moreover, it is predicted that the spin filtering efficiency (SFE) of the HS junctions strongly depends on the bridging complex geometry, with 1 showing a voltage- Page 1 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A dependent SFE, whereas 2 exhibits an SFE of practically 100% over all the studied voltage range. To be pragmatic towards applications, the ligands L1 and L2 and complex 1 have been successfully synthesized, and the spin-state switching propensity of 1 in the bulk state has been elucidated. The results shown in this study might lead to the synthesis and characterization of isomeric SCO complexes with tuneable spinstate switching and charge transport properties. Introduction Using molecules as circuit elements for fabricating realistic devices capable of performing the functions of traditional silicon-based transistors is the goal of molecular electronics and spintronics. Such a goal can only be achieved by studying how molecules respond to external triggers at the single-molecule level. In molecular electronics, the charge degree of freedom is leveraged to perform device operations, and charge transport across a molecular junction is controlled by varying the electrode-molecule coupling, which in turn can be achieved by tuning the molecular structure, as elucidated by Venkataraman and coworkers, for example.1 In molecular spintronics, the spin magnetic moment of carriers is used as a second degree of freedom along with the charge degree of freedom. Therefore, to fabricate molecular spintronics elements, control over both charge and spin degrees of freedom is necessary. Lanthanide- and transition-metal-based molecular complexes carrying magnetic spin degrees of freedom are ideally suited to serve as spintronics elements. Single-molecule magnets (SMMs) and spin-crossover (SCO) complexes are two different classes of spin-bearing molecular systems, whose utility has been demonstrated as spintronics elements.2-4 In the case of SMMs, the anisotropic nature of the magnetic spin degree of freedom has been exploited to perform spin selective operations—a remarkable example is the [TbPc2]-SMM-based molecular spin valve.5 On the other hand, the spintronics utility of the SCO complexes stems from the spin-filtering characteristic of high-spin complexes in molecular junctions. The SCO complexes undergo high-spin (HS)- to-low-spin (LS), and vice versa, spin-state switching in the bulk6-8 and thin-film9-11 states, and at the singlemolecule level.12-14 The spin-state switching in the thin-film15 and single-molecule16 levels are shown to involve concomitant conductance switching and spin-filtering efficiency (SFE); thereby, a reversible ONOFF switching of conductance and SFE can be achieved, assisting the progress toward the realization of switchable molecular spintronics architectures. Charge neutral iron(II) complexes composed of sulphur-based anchoring groups are suitable for studying charge and spin transport characteristics at the single-molecule level. Complexes belonging to Page 2 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A [Fe(H2Bpz2)2(L)]—H2Bpz = dihydrobis(pyrazolyl)borate, L = 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy)—family17,18 are useful candidates for developing molecular spintronics elements because the complexes can be functionalized with molecular anchoring groups for electrodes19, 20, facilitating studies at single-molecule junctions. Although computational and experimental studies demonstrating spin-state- dependent conductance switching and spin-filtering nature of single SCO molecule junctions have been reported,21-23 single-molecule level studies focusing on the [Fe(H2Bpz2)2(L)] family of complexes are limited to a handful of studies in scanning tunneling microscopy (STM) junctions.24-26 A notable example is the electron-induced SCO phenomenon demonstrated for [Fe(H2Bpz2)2(phen)] in an STM junction.27 Moreover, most of the studies relied on prototypical [Fe(H2Bpz2)2(L)] complexes first reported by Real and co-workers17, and structural diversity of [Fe(H2Bpz2)2(L)]-based complexes is rather limited, when molecular spintronics application is concerned. Crucially, reports detailing single-molecule transport characteristics of anchoring group tethered functional [Fe(H2Bpz2)2(L)] complexes are yet to be reported, to the best of our knowledge. To elucidate the utility of the [Fe(H2Bpz2)2(bipy)]-based complexes as molecular spintronics elements, we have computationally studied, using the nonequilibrium Green functions formalism combined with the density functional theory (NEGF-DFT), the transport characteristics of thiomethyl (SMe) anchoring group tethered charge neutral iron(II) complexes 1 and 2 based on ligands L1 and L2, respectively (Figure 1). Complexes 1 and 2 feature the 4-(methylhio)phenylethynyl anchoring groups at the 5,5´ and 4,4´ positions, respectively, of the 2,2’-bipyridine skeleton. The ligands and complexes featuring the same molecular formula are positional isomers, considering the different arrangements of anchoring groups on the 2,2’-bipyridine skeleton. Our studies reveal that in the junctions composed of complex 1 or 2, the HS state is more conductive than the LS state. The HS-junctions show SFEs in the low bias regime reaching values of about 80% and 100% for 1 and 2, respectively, at 0.3 V. The spin-state-dependence of conductance and differing SFEs predicted for 1 and 2 indicate that the spin transport characteristics are completely determined by the molecular structure and spin-state. Crucially, we show that applied voltage has an effect on the frontier molecular orbitals of the complexes, dramatically changing the transport properties of the junctions, suggesting that it is possible to induce spin-state switching in the junctions of 1 and 2 by applying an electric field, implying the possible utility of the complexes as spintronics elements. Finally, by comparing the transport characteristics of LS-junctions of 1 and 2 with the respective constituent ligands L1 and L2, insights into Page 3 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A the role of the iron(II) centre in mediating charge transport have been obtained. Moreover, to show how the molecular functionalization affects the electronic structure and the resultant spin-state switching characteristics, the results obtained for 1 and 2 are compared with the prototypical [Fe(II)(H2Bpz2)2(bipy)] complex, hereafter referred as complex 3 (Figure 1). To be more practical in terms of device applications, we have attempted to synthesize the ligands and complexes discussed in this study. Our attempts were successful in the cases of L1, L2, and complex 1; whereas, a satisfactory characterization of complex 2 was not achieved. Nevertheless, our DFT-based thermo-chemistry calculations show that complex 2 has a negative of formation ( G = standard Gibbs ∆𝐺 free energy), indicating that the compound is thermodynamically stable. N N S S L1 BH2 N N N N Fe N N N N H2B N N S S BH2 N N N N Fe N N N N BH2 NN S S NN S S L2 Complex 1 Complex 2 BH2 N N N N Fe N N N N H2B NN Complex 3 Figure 1. Molecular structures of the ligands (L1 and L2) and complexes (1, 2, and 3) discussed in this study. Experimental procedures Materials, experimental protocols, and instrumentation used to characterize the molecular systems are described in section S1 of the supporting information (SI). Page 4 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A Computational details Electronic structure and magnetic properties of the complexes The electronic structure and magnetic properties of complexes 1, 2, and 3 were calculated through Density Functional Theory (DFT) and Wave Function (WFT)-based methods, by means of the ORCA28 and QuantumATK29 software packages. In all the calculations performed with the QuantumATK code, all atoms were represented by a double-ζ-polarized (DZP) basis set, along with PseudoDojo norm-conserving pseudopotentials.30 We have utilized the Perdew–Burke–Ernzerhof (PBE)31 exchange-correlation (XC) functional, widely used in the determination of the transport properties of spin-crossover complexes in molecular junctions,22, 23, 32 and the rPBE33 functional, which has been shown to provide more accurate values for the gap between the HS-LS states in iron(II) spin-crossover complexes than other GGA functionals as the PBE.34 The mesh cut-off energy was set to 210 Rydberg for both the real and reciprocal space grids in all calculations, with a self-consistency tolerance for the convergence of the Hamiltonian and density matrices of 1.0x10-4 eV. In both the WFT and DFT calculations using the ORCA software package, all atoms were represented with a def2-TZVP35 basis set, with the exception of the Fe ion, where a larger def2-QZVPP basis set was employed. The WFT calculations were carried out through the complete active space self-consistent field (CASSCF) methodology.36 To consider the effects of the dynamic correlation, we employed the N-Electron Valence State Perturbation Theory (NEVPT2)37 in its partially contracted formulation,38 (FIC-NEVPT2 option in ORCA code). The converged CASSCF wavefunction was utilized as the reference, and the D3tpre and D4tpre parameters were set strictly to 0. For all calculations, the resolution of the identity (RI)39 and the zeroth-order regular approximation (ZORA)40 were adopted to increase the efficiency of the calculations and treat relativistic effects, respectively. The active space utilized in the CASSCF/NEVPT2 calculations consists of 10 electrons in 12 orbitals corresponding to six electrons occupying the five 3d- type orbitals centred on the Fe ion with their corresponding five “double-shell orbitals,” and four electrons in two σ-type orbitals localized between the Fe centre and the six coordinating nitrogen atoms (Figures S2.1 and S2.2). This CAS (10,12) is commonly employed in CASSCF/PT2 studies on Fe(II) SCO complexes.41-44 Transport properties of the complexes and ligands The transport properties of the complexes, as well as all geometry optimizations involved in the construction of the junctions, were obtained using the QuantumATK software package. These calculations Page 5 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A were performed employing the PBE-XC functional, and the same basis set and convergence parameters as in the single complex studies (see above) were used. The molecular junctions (see Figure 2 for a representative example) were constructed starting with the full geometry relaxation of complexes 1 and 2, in both the HS and LS configurations, anchored to two Au(111) electrodes, by means of both terminal S groups bonded to two gold adatom in the hollow position of the surface. The unit cell was periodic in the three directions. It consisted of the complex between two 7x6 Au(111) slabs, three layers deep on one side and two layers deep on the other, thus keeping five Au layers (approximately 14 Å) between the periodic repetitions of the complex in the transport direction and a distance of about 11 Å in transverse ones. During all geometry optimizations, the unit cell size was allowed to relax in the transport direction and kept fixed in transverse ones. Finally, for the calculations of the transport properties, both Au(111) surfaces were reduced to slabs of 5x4 atoms, adding the corresponding vacuum space in the transverse directions to preserve a distance greater than 10 Å between the periodic images. The spin-resolved transport properties were computed using the combination of the DFT with the Keldysh nonequilibrium Green′s function (NEGF) formalism, known as the DFT-NEGF methodology.45-47 Figure 2. Scheme of the molecular junction architecture employed to study the spin-resolved transport properties of complex 1. Page 6 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A Under a finite bias voltage Vb, the spin-resolved current through the junction is given by the Landauer- Büttiker formula:48 𝐼 𝜎 ( 𝑉 𝑏 ) = 𝑒 ℎ 𝜇 𝑅 ∫ 𝜇 𝐿 𝑑𝐸 𝑇 𝜎 ( 𝐸 , 𝑉 𝑏 ) [ 𝑓 𝐿 ( 𝐸 , 𝜇 𝐿 ) ― 𝑓 𝑅 ( 𝐸 , 𝜇 𝑅 ) ] where σ =α, β is the spin index, and fL/R and μL/R are the Fermi distribution function and chemical potential, respectively, of the left (L) or right (R) electrode. The spin-resolved transmission coefficient is defined by: 𝑇 𝜎 (𝐸, 𝑉 𝑏 ) = 𝑇𝑟[ 𝛤 𝐿 𝐺 𝑟 𝛤 𝑅 𝐺 𝑎 ] where and are the retarded and advanced Green´s functions, and is the self-energy matrices, 𝐺 𝑟 𝐺 𝑎 𝛤 𝐿/𝑅 which describe the coupling between the electrodes and the central scattering region. The spin filtering efficiency at a given bias voltage is defined as:49,50 𝑆𝐹𝐸 ( 𝑉 ) = | 𝐼 ∝ ( 𝑉 𝐵 ) ― 𝐼 𝛽 ( 𝑉 𝐵 ) | 𝐼 ∝ ( 𝑉 𝐵 ) + 𝐼 𝛽 ( 𝑉 𝐵 ) , and at zero bias: 𝑆𝐹𝐸 ( 𝑉 = 0 ) = | 𝑇 ∝ ( V = 0 ) ― 𝑇 𝛽 ( V = 0 ) | 𝑇 ∝ ( V = 0 ) + 𝑇 𝛽 ( V = 0 ) , where and stands for the spin up (down) current and spin up (down) transmission, 𝐼 𝛼 ( 𝐼 𝛽 ) 𝑇 𝛼 ( 𝑇 𝛽 ) respectively, at zero bias. Results and Discussion Syntheses and characterization of the ligands and complexes Ligands L1 and L2 were synthesized from the corresponding diethynyl-2,2'-bipyridine precursors, as depicted in schemes S1.1 and S1.2. Treatment of L1 with the charge-neutral iron(II) precursor complex, [Fe(H2Bpz2)2(MeOH)2],51 yielded complex 1 as a greenish-yellow precipitate in a moderate yield. On the other hand, our attempts to obtain complex 2 in its pure form by treating L2 with the iron(II) precursor complex was not successful. To circumvent the issue, we propose the following. It has been reported in the literature that chemistry can be performed at the single molecular level, especially in molecular Page 7 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A junction forming experiments.52,53, 54 Based on such reports, we propose direct trapping of complex 2 in between electrodes by treating a solution containing it above an electrode in a mechanically controllable break junction (MCBJ) and inducing contact formation by breaking the electrode. However, such experiment at the single-molecule level still needs to be performed; therefore, our suggestion is speculative in nature. Note, the complex formation reaction upon treatment of charge neutral iron(II) complex precursor—[Fe(H2Bpz2)2]—and ligand L2 involves a colour change of the reaction mixture from pale yellow to green, and one can safely assume the expected complex formation by monitoring the colour change. Moreover, DFT-based thermochemistry calculations performed on complex 2 (Section S1.2 of the supporting information), shows that the compound is thermodynamically stable, supporting the hypothesis presented above. For more details on the preparation and characterization of L1, L2, and complex 1 and attempted preparation of complex 2, see supporting information (sections S1.1 and S1.2). Spin-state switching characteristic of complex 1 in the bulk state Complex 1 showed gradual and incomplete spin-state switching characteristics in the bulk powder state (Figure 3). At 300 K, a χT value of 3.05 cm3 mol-1 K was observed indicating the HS state of the complex. Upon cooling at a scan rate of 3 K/min (cycle 1), the complex remained in the HS state until about 225 K. Afterwards, a gradual HS-to-LS switching started and proceeded until 60 K. Subsequently, a plateau-like region extending down to 30 K (χT = 1.92 cm3 mol-1 K) was observed indicating the stabilization of a mixed phase with 2:1 HS/LS ratio. Cooling below 25 K resulted in a sudden decrease of the χT value to 1.2 cm3 mol-1 K, attributed to the depopulation of the exited zero-field split levels of the HS term. In the heating branch, the χT versus T plot retraced the cooling branch until 64 K. After that a small lag in the LS-to-HS switching was observed in a narrow temperature range resulting in the formation of a small hysteresis loop (ΔT1/2 = about 6 K). After crossing the hysteretic region, the switching profile retraced the heating branch. The observed lag in the LS-to-HS switching in the heating branch could have arisen due to the kinetic trapping of the LS complexes in the mixed phase. To check for the role of scan rate on the spinstate switching process, a second cycle was performed at a scan rate of 1 K/min. The switching proceeded exactly the same manner as observed for the 3 K/min scan rate, indicating the scan rate independent nature of the spin-state switching process until 1 K/min. The scan rate-dependent studies also confirm the reproducibility of the switching process. On a comparative scale, stark differences in the spin-state switching characteristic of complex 1 and the parent [Fe(H2Bpz2)2(2,2´-bipyridine)] complex (complex 3) have been observed. Complex 3 undergoes nearly complete spin-state switching with a T1/2 = 160 K. On the contrary, complex 1 undergoes incomplete Page 8 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A heavily affects the transmission probability, as seen in the transmission spectra for the different voltage values. However, the form of this orbital and the corresponding transmission function produced by its resonance remain virtually unchanged (Figures S4.3 and S4.4). The decrease in the magnitude of the transmission peaks and broadening observed for complex 2 is reflected in the I versus V profiles, where the spin-down current is about an order of magnitude smaller for complex 2, and nearly three orders of magnitude smaller for the spin-up case (Figure 6b). The dramatic decrease in the spin-up current yields an SFE of almost 100% over the entire voltage range studied. It is worth mentioning that the anomaly observed in the case of complex 1, where the spin-down current drastically drops above 0.3 V, is also present in the junction composed of complex 2 (from V ˃ 0.4 V). However, in the case of complex 2, the current does not increase again, but it continues to drop until 0.6 V, exhibiting a negative differential resistance (NDR) effect. Moreover, a marked applied voltagedependent displacement of the spin-down HOMO is also observed (Figure S4.2). Several of the features present in the I versus V profiles of the complexes—for example, the strong spin-down polarization of the current, highly bias-dependent transmission spectra, and NDR effects, have been reported in previous theoretical studies detailing the spin-polarized transport properties of iron(II) SCO complexes utilizing Au(111) nanowires as electrodes.32, 71 Regarding the mechanisms underlying the NDR, a recent DFT-NEGF- based study suggests72 that the local electronic structure of the electrodes could lead to the appearance of artificial NDR effects. Without discarding an artefact of the model itself, the observed NDR effect may be associated with a physical effect related to the displacement of molecular states close to the Fermi level under the effect of bias. This displacement could take the aforementioned molecular states into energy regions where the electrodes DOS drastically drops, decreasing the coupling with the electrodes and, thus, reducing the transmission. Also, both complexes exhibit a high SFE, in line with the values obtained for other iron(II)-based single-molecule junctions,22, 23, 60, 73 in contrast to devices based on different transition metal—Co(II), Cr(II)— complexes that display much lower SFE values.74, 75 Page 15 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A Figure 6. Spin-resolved current and SFE calculated in the junctions with (a) complex 1 and (b) 2 in HS configuration. The inset in (b) shows the detail of the spin-up current. Finally, we report the results obtained for the ligands L1 and L2, and their respective complexes in the LS configuration. Their transmission spectra, PDOS plots, and relevant transmission functions are presented in Figure 7 and sections S5 and S6 of the SI. For both complexes and ligands, the strongest transmission signal arises from the resonance with the molecular bridge LUMO junctions. For complex 2 and ligand L2, an additional but weaker transmission peak is observed, product of the resonance with the molecule’s LUMO+1 orbital. For the complexes, the transmission functions are mainly localized on the bipyridine and the anchoring ligands, exhibiting practically the same nature as those of the corresponding ligands. It is worth mentioning that the presence of the Fe(II) ion does not increase the intensity of the signals, but it displaces them by about 0.1 eV towards the Fermi level. The similarities between the transport properties of the ligands and their respective LS complexes are also reflected in their I-V profiles (Figure 8), and the computed zero-bias conductance values, ( for complex 1 (L1), and 2.4 × 10 ― 6 𝐺 0 1.6 × 10 ― 6 𝐺 0 ) 9.1 × ( for complex 2 (L2). The calculated current values are very close for voltage values 10 ― 7 𝐺 0 5.0 × 10 ― 7 𝐺 0 ) up to 0.5 V for L1 and complex 1 and 0.4 V for L2 and complex 2. The current in the junctions featuring the complexes drastically increases at higher voltages. Note that the zero-bias conductance for complex 1 and L1 is approximately 2 orders of magnitude higher than for complex 2 and L2, and the magnitude of the total current (spin-up + spin-down) is 3 orders of magnitude higher in all the studied voltage ranges (Figure 8), confirming that the position of the anchoring groups chiefly determines the conductance of the junction. It is also instructive to compare the conductance and total current in the junctions with the complexes in the HS configuration with the ones calculated for the ligands (Figure 8). For both ligands, iron(II) complexation significantly increases the total conductance/current, especially in the cases of Page 16 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A complex 2 and L2, where the conductance increases 3 orders of magnitude, and the total current from 2 to 3 orders of magnitude as the voltage is increased. This is in contrast to the behaviour observed for the complexes in the LS configuration, where the complexation of the ligands with the iron(II) containing fragment does not significantly increase the calculated conductance or total current. The higher conductance of the HS junctions has been reported in several experimental studies featuring iron(II) SCO complexes as molecular bridges.16, 21, 76 To obtain more insight into the physical mechanism behind the drastic difference in the conductance of both complexes, we computed the pathway of the strongest peak in the transmission spectrum of the LS configuration, corresponding to the resonance with the LUMO of the complex (Figure S6.3). In this analysis, the transmission coefficient is projected into local bond contributions between pairs of atoms,77 thus giving us an idea of how the carriers traverse the scattering zone. It can be observed that in complex 1 junction, a smooth path is stablished through the bipyridine ligand, in contrast to complex 2, where a high level of reflection is observed at the plane between both pyridine moieties. Note the anticlockwise circulation at the pyridine fragments of complex 2, in contrast to the straight path followed by the carries in complex 1. As some authors have pointed out, the origin of this phenomenon could be attributed to the antiresonance produced by destructive quantum interference effects (QI).78-80 Page 17 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A Figure 7. Spin-resolved transmission spectrum and PDOS on the molecular bridge utilizing ligands 1 and 2 as the junction active elements. Page 18 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A Figure 8. Comparison of the total current (spin-up + spin-down) versus bias voltage for ligands L1, L2 and complexes 1 and 2, in (a) LS and (b) HS configurations. We would like to remark that the transport characteristics reported for complexes 1 and 2 in this study may not reflect the scenario in a realistic metal-molecule junction, where a myriad of metal-molecule bonding configurations are possible. On a comparative scale, the current values in the µA range calculated for the single-molecule junctions of complexes 1 and 2 (Figure 8) are much greater than current values in the nA 2, 21, 61, 81 or pA82 range, typically measured in the single-molecule junctions of molecules undergoing spin-state switching. We attribute such high values of predicted current to the approximations associated with the computational methods applied to model transport in the single-molecule junctions of complexes 1 and 2. Remarkably, the current values calculated for 1 and 2 are in quantitative agreement with the calculated values reported for related SCO complexes at the single-molecule level,3, 23, 83, 84 emphasizing on the role of methodology used to calculate the transport characteristics in over estimating the current values. Single-molecule transport measurements of [Fe(II)(H2Bpz2)2(L)]-based complexes in MCBJ junctions are necessary to get insights into the true conductance values of the complexes. Conclusions In this computational investigation, we have studied the spin-state dependence of the charge and spin transport characteristics of single-molecule junctions composed of isomeric charge-neutral complexes 1 and 2. The WFT calculations revealed that spin-state switching of 1 can be triggered upon application of external electric field. On the other hand, complex 2 showed a weak applied electric field-dependent HS- Page 19 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A LS energy variation. Remarkably, small perturbations in the electrode-molecule coupling in the singlemolecule junctions featuring complex 2 are shown to be effective in inducing electric-field-induced spinstate switching, auguring well for the experimental investigations. From the transport front, the DFT-NEGF calculations revealed the crucial role of the position of anchoring ligands in 1 and 2 in determining the total current (spin up + spin down). Both the HS and LS junctions of complex 1 showed higher conductance than the junctions of 2, and the variation of conductance is remarkably higher in the LS junctions than in the HS junctions. The isomeric nature of the complexes, culminating as different molecular orientations in the electrode gap, is also reflected on the spin-filtering efficiencies of the HS-junctions. While complex 1 exhibited voltage-dependent variation of SFE, complex 2 performed, theoretically, as an ideal spin filter ( SFE ≈ 100%) over the studied voltage range. Our unsuccessful attempts to obtain complex 2 in its pure form is a limitation of the study. However, such limitation can be overcome by designing a new set of [Fe(II)(H2Bpz2)2(bipy)]-based complexes featuring anchoring groups for metallic electrodes. We believe that the predictions presented in this study could serve as a starting point to study [Fe(II)(H2Bpz2)2(bipy)]- based isomeric complexes. Acknowledgments N.M.P thanks to the financial support of “ANID Postodoctorado FONDECYT 3210181”. This research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02) of the Universidad de Chile. C.J.C. acknowledges the financial support through grant PGC2018-101689-B-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”. The technical support of the Supercomputing Team of the Centro Informático Científico de Andalucía (CICA) and the access to the computational facilities of the “Centro de Servicios de Informática y Redes de Comunicaciones” (CSIRC, Universidad de Granada, Spain) are also acknowledged. Conflicts of interest There are no conflicts of interest to declare. References (1) Venkataraman, L.; Klare, J. E.; Nuckolls, C.; Hybertsen, M. S.; Steigerwald, M. L. Nature 2006, 442 (7105), 904-907. DOI: 10.1038/nature05037. Page 20 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A (2) Meded, V.; Bagrets, A.; Fink, K.; Chandrasekar, R.; Ruben, M.; Evers, F.; Bernand-Mantel, A.; Seldenthuis, J. S.; Beukman, A.; van der Zant, H. S. J. Physical Review B 2011, 83 (24), 245415. DOI: 10.1103/PhysRevB.83.245415. (3) Zhao, W.; Zou, D.; Yang, C.-L.; Sun, Z. Journal of Materials Chemistry C 2017, 5 (34), 8862-8868, 10.1039/C7TC02312J. DOI: 10.1039/C7TC02312J. (4) Liu, B.; Fu, H.; Guan, J.; Shao, B.; Meng, S.; Guo, J.; Wang, W. ACS Nano 2017, 11 (11), 11402-11408. DOI: 10.1021/acsnano.7b06029. (5) Godfrin, C.; Thiele, S.; Ferhat, A.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W.; Balestro, F. ACS Nano 2017, 11 (4), 3984-3989. DOI: 10.1021/acsnano.7b00451. (6) Halepoto, D. M.; Holt, D. G. L.; Larkworthy, L. F.; Leigh, G. J.; Povey, D. C.; Smith, G. W. Journal of the Chemical Society, Chemical Communications 1989, (18), 1322-1323, 10.1039/C39890001322. DOI: 10.1039/C39890001322. (7) Pandurangan, K.; Gildea, B.; Murray, C.; Harding, C. J.; Müller-Bunz, H.; Morgan, G. G. Chemistry – A European Journal 2012, 18 (7), 2021-2029. DOI: https://doi.org/10.1002/chem.201102820. (8) Gaspar, A. B.; Muñoz, M. C.; Niel, V.; Real, J. A. Inorganic Chemistry 2001, 40 (1), 9-10. DOI: 10.1021/ic000788m. (9) Naggert, H.; Rudnik, J.; Kipgen, L.; Bernien, M.; Nickel, F.; Arruda, L. M.; Kuch, W.; Näther, C.; Tuczek, F. Journal of Materials Chemistry C 2015, 3 (30), 7870-7877, 10.1039/C5TC00930H. DOI: 10.1039/C5TC00930H. (10) Gruber, M.; Miyamachi, T.; Davesne, V.; Bowen, M.; Boukari, S.; Wulfhekel, W.; Alouani, M.; Beaurepaire, E. The Journal of Chemical Physics 2017, 146 (9), 092312. DOI: 10.1063/1.4973511 (acccessed 2022/04/05). (11) Atzori, M.; Poggini, L.; Squillantini, L.; Cortigiani, B.; Gonidec, M.; Bencok, P.; Sessoli, R.; Mannini, M. Journal of Materials Chemistry C 2018, 6 (33), 8885-8889, 10.1039/C8TC02685H. DOI: 10.1039/C8TC02685H. (12) Miyamachi, T.; Gruber, M.; Davesne, V.; Bowen, M.; Boukari, S.; Joly, L.; Scheurer, F.; Rogez, G.; Yamada, T. K.; Ohresser, P.; et al. Nature Communications 2012, 3 (1), 938. DOI: 10.1038/ncomms1940. (13) Jasper-Toennies, T.; Gruber, M.; Karan, S.; Jacob, H.; Tuczek, F.; Berndt, R. Nano Letters 2017, 17 (11), 6613-6619. DOI: 10.1021/acs.nanolett.7b02481. (14) Tong, Y.; Kelaï, M.; Bairagi, K.; Repain, V.; Lagoute, J.; Girard, Y.; Rousset, S.; Boillot, M.-L.; Mallah, T.; Enachescu, C.; et al. The Journal of Physical Chemistry Letters 2021, 12 (45), 11029-11034. DOI: 10.1021/acs.jpclett.1c03271. (15) Mahfoud, T.; Molnár, G.; Cobo, S.; Salmon, L.; Thibault, C.; Vieu, C.; Demont, P.; Bousseksou, A. Applied Physics Letters 2011, 99 (5), 053307. DOI: 10.1063/1.3616147 (acccessed 2022/06/10). (16) Frisenda, R.; Harzmann, G. D.; Celis Gil, J. A.; Thijssen, J. M.; Mayor, M.; van der Zant, H. S. J. Nano Letters 2016, 16 (8), 4733-4737. DOI: 10.1021/acs.nanolett.5b04899. (17) Real, J. A.; Muñoz, M. C.; Faus, J.; Solans, X. Inorganic Chemistry 1997, 36 (14), 3008-3013. DOI: 10.1021/ic960965c. (18) Kuppusamy, S. K.; Spieker, L.; Heinrich, B.; Salamon, S.; Gruber, M.; Wende, H.; Ruben, M. ChemRxiv 2022, This content is a preprint and has not been peer-reviewed. DOI: 10.26434/chemrxiv-2022-9mtbs. (19) Kaliginedi, V.; V. Rudnev, A.; Moreno-García, P.; Baghernejad, M.; Huang, C.; Hong, W.; Wandlowski, T. Physical Chemistry Chemical Physics 2014, 16 (43), 23529-23539, 10.1039/C4CP03605K. DOI: 10.1039/C4CP03605K. (20) Chen, F.; Li, X.; Hihath, J.; Huang, Z.; Tao, N. Journal of the American Chemical Society 2006, 128 (49), 15874-15881. DOI: 10.1021/ja065864k. (21) Burzuri, E.; Garcia-Fuente, A.; Garcia-Suarez, V.; Senthil Kumar, K.; Ruben, M.; Ferrer, J.; van der Zant, H. S. J. Nanoscale 2018, 10 (17), 7905-7911. DOI: 10.1039/c8nr00261d. Page 21 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A (22) Gu, Y.; Hu, Y.; Huang, J.; Li, Q.; Yang, J. The Journal of Physical Chemistry C 2019, 123 (26), 16366- 16372. DOI: 10.1021/acs.jpcc.9b02856. (23) Aravena, D.; Ruiz, E. Journal of the American Chemical Society 2012, 134 (2), 777-779. DOI: 10.1021/ja2090096. (24) Bairagi, K.; Iasco, O.; Bellec, A.; Kartsev, A.; Li, D.; Lagoute, J.; Chacon, C.; Girard, Y.; Rousset, S.; Miserque, F.; et al. Nature Communications 2016, 7 (1), 12212. DOI: 10.1038/ncomms12212. (25) Shi, S.; Schmerber, G.; Arabski, J.; Beaufrand, J. B.; Kim, D. J.; Boukari, S.; Bowen, M.; Kemp, N. T.; Viart, N.; Rogez, G.; et al. Applied Physics Letters 2009, 95 (4), 043303. DOI: 10.1063/1.3192355 (acccessed 2022/05/23). (26) Warner, B.; Oberg, J. C.; Gill, T. G.; El Hallak, F.; Hirjibehedin, C. F.; Serri, M.; Heutz, S.; Arrio, M.-A.; Sainctavit, P.; Mannini, M.; et al. The Journal of Physical Chemistry Letters 2013, 4 (9), 1546-1552. DOI: 10.1021/jz4005619. (27) Gopakumar, T. G.; Matino, F.; Naggert, H.; Bannwarth, A.; Tuczek, F.; Berndt, R. Angewandte Chemie International Edition 2012, 51 (25), 6262-6266. DOI: https://doi.org/10.1002/anie.201201203. (28) Neese, F. Wiley Interdisciplinary Reviews: Computational Molecular Science 2012, 2 (1), 73-78. DOI: 10.1002/wcms.81 (acccessed 2018/12/17). (29) Smidstrup, S.; Markussen, T.; Vancraeyveld, P.; Wellendorff, J.; Schneider, J.; Gunst, T.; Verstichel, B.; Stradi, D.; Khomyakov, P. A.; Vej-Hansen, U. G.; et al. Journal of Physics: Condensed Matter 2019, 32 (1), 015901. DOI: 10.1088/1361-648x/ab4007. (30) van Setten, M. J.; Giantomassi, M.; Bousquet, E.; Verstraete, M. J.; Hamann, D. R.; Gonze, X.; Rignanese, G. M. Computer Physics Communications 2018, 226, 39-54. DOI: https://doi.org/10.1016/j.cpc.2018.01.012. (31) Perdew, J. P.; Burke, K.; Ernzerhof, M. Physical Review Letters 1997, 78 (7), 1396-1396. DOI: 10.1103/PhysRevLett.78.1396. (32) Huang, J.; Xie, R.; Wang, W.; Li, Q.; Yang, J. Nanoscale 2016, 8 (1), 609-616, 10.1039/C5NR05601B. DOI: 10.1039/C5NR05601B. (33) Hammer, B.; Hansen, L. B.; Nørskov, J. K. Physical Review B 1999, 59 (11), 7413-7421. DOI: 10.1103/PhysRevB.59.7413. (34) Siig, O. S.; Kepp, K. P. The Journal of Physical Chemistry A 2018, 122 (16), 4208-4217. DOI: 10.1021/acs.jpca.8b02027. (35) Weigend, F. Physical Chemistry Chemical Physics 2006, 8 (9), 1057-1065, 10.1039/B515623H. DOI: 10.1039/B515623H. (36) Roos, B. O.; Taylor, P. R.; Si≐gbahn, P. E. M. Chemical Physics 1980, 48 (2), 157-173. DOI: https://doi.org/10.1016/0301-0104(80)80045-0. (37) Angeli, C.; Cimiraglia, R.; Evangelisti, S.; Leininger, T.; Malrieu, J. P. The Journal of Chemical Physics 2001, 114 (23), 10252-10264. DOI: 10.1063/1.1361246 (acccessed 2022/06/06). (38) Angeli, C.; Cimiraglia, R.; Malrieu, J.-P. The Journal of Chemical Physics 2002, 117 (20), 9138-9153. DOI: 10.1063/1.1515317 (acccessed 2022/06/06). (39) Neese, F. Journal of Computational Chemistry 2003, 24 (14), 1740-1747. DOI: https://doi.org/10.1002/jcc.10318. (40) Lenthe, E. v.; Baerends, E. J.; Snijders, J. G. The Journal of Chemical Physics 1993, 99 (6), 4597-4610. DOI: 10.1063/1.466059 (acccessed 2018/12/17). (41) Vela, S.; Fumanal, M.; Ribas-Ariño, J.; Robert, V. Journal of Computational Chemistry 2016, 37 (10), 947-953. DOI: https://doi.org/10.1002/jcc.24283. (42) Sousa, C.; de Graaf, C.; Rudavskyi, A.; Broer, R. The Journal of Physical Chemistry A 2017, 121 (51), 9720-9727. DOI: 10.1021/acs.jpca.7b10687. (43) Finney, B. A.; Chowdhury, S. R.; Kirkvold, C.; Vlaisavljevich, B. Physical Chemistry Chemical Physics 2022, 24 (3), 1390-1398, 10.1039/D1CP04885F. DOI: 10.1039/D1CP04885F. Page 22 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A (44) Rudavskyi, A.; Sousa, C.; de Graaf, C.; Havenith, R. W. A.; Broer, R. The Journal of Chemical Physics 2014, 140 (18), 184318. DOI: 10.1063/1.4875695 (acccessed 2022/05/25). (45) Taylor, J.; Guo, H.; Wang, J. Physical Review B 2001, 63 (24), 245407. DOI: 10.1103/PhysRevB.63.245407. (46) Taylor, J.; Guo, H.; Wang, J. Physical Review B 2001, 63 (12), 121104. DOI: 10.1103/PhysRevB.63.121104. (47) Brandbyge, M.; Mozos, J.-L.; Ordejón, P.; Taylor, J.; Stokbro, K. Physical Review B 2002, 65 (16), 165401. DOI: 10.1103/PhysRevB.65.165401. (48) Büttiker, M.; Imry, Y.; Landauer, R.; Pinhas, S. Physical Review B 1985, 31 (10), 6207-6215. DOI: 10.1103/PhysRevB.31.6207. (49) Tao, L. L.; Wang, J. Nanoscale 2017, 9 (34), 12684-12689. DOI: 10.1039/c7nr03532b. (50) Zhao, P.; Gao, X.-J.; Song, Y.; Li, X.-X.; Chen, G. Organic Electronics 2018, 57, 104-109. DOI: https://doi.org/10.1016/j.orgel.2018.03.007. (51) Ossinger, S.; Nather, C.; Tuczek, F. IUCrData 2016, 1 (8), x161252. DOI: doi:10.1107/S2414314616012529. (52) Xie, X.; Li, P.; Xu, Y.; Zhou, L.; Yan, Y.; Xie, L.; Jia, C.; Guo, X. ACS Nano 2022, 16 (3), 3476-3505. DOI: 10.1021/acsnano.1c11433. (53) Li, X.; Hu, D.; Tan, Z.; Bai, J.; Xiao, Z.; Yang, Y.; Shi, J.; Hong, W. Topics in Current Chemistry 2017, 375 (2), 42. DOI: 10.1007/s41061-017-0123-x. (54) Cao, Y.; Dong, S.; Liu, S.; He, L.; Gan, L.; Yu, X.; Steigerwald, M. L.; Wu, X.; Liu, Z.; Guo, X. Angewandte Chemie International Edition 2012, 51 (49), 12228-12232, https://doi.org/10.1002/anie.201205607. DOI: https://doi.org/10.1002/anie.201205607 (acccessed 2022/11/29). (55) Ossinger, S.; Näther, C.; Tuczek, F. Journal of Physics: Condensed Matter 2019, 32 (9), 094001. DOI: 10.1088/1361-648x/ab5776. (56) Zhang, W.; Alonso-Mori, R.; Bergmann, U.; Bressler, C.; Chollet, M.; Galler, A.; Gawelda, W.; Hadt, R. G.; Hartsock, R. W.; Kroll, T.; et al. Nature 2014, 509 (7500), 345-348. DOI: 10.1038/nature13252. (57) Bressler, C.; Milne, C.; Pham, V. T.; ElNahhas, A.; van der Veen, R. M.; Gawelda, W.; Johnson, S.; Beaud, P.; Grolimund, D.; Kaiser, M.; et al. Science 2009, 323 (5913), 489-492. DOI: 10.1126/science.1165733 (acccessed 2022/09/28). (58) Cannizzo, A.; Milne, C. J.; Consani, C.; Gawelda, W.; Bressler, C.; van Mourik, F.; Chergui, M. Coordination Chemistry Reviews 2010, 254 (21), 2677-2686. DOI: https://doi.org/10.1016/j.ccr.2009.12.007. (59) Oppermann, M.; Zinna, F.; Lacour, J.; Chergui, M. Nature Chemistry 2022, 14 (7), 739-745. DOI: 10.1038/s41557-022-00933-0. (60) Kuppusamy, S. K.; Mizuno, A.; García-Fuente, A.; van der Poel, S.; Heinrich, B.; Ferrer, J.; van der Zant, H. S. J.; Ruben, M. ACS Omega 2022, 7 (16), 13654-13666. DOI: 10.1021/acsomega.1c07217. (61) Harzmann, G. D.; Frisenda, R.; van der Zant, H. S. J.; Mayor, M. Angewandte Chemie International Edition 2015, 54 (45), 13425-13430. DOI: https://doi.org/10.1002/anie.201505447. (62) Cirera, J.; Via-Nadal, M.; Ruiz, E. Inorganic Chemistry 2018, 57 (22), 14097-14105. DOI: 10.1021/acs.inorgchem.8b01821. (63) Reiher, M. Inorganic Chemistry 2002, 41 (25), 6928-6935. DOI: 10.1021/ic025891l. (64) Kepp, K. P. Inorganic Chemistry 2016, 55 (6), 2717-2727. DOI: 10.1021/acs.inorgchem.5b02371. (65) Karuppannan, S. K.; Martín-Rodríguez, A.; Ruiz, E.; Harding, P.; Harding, D. J.; Yu, X.; Tadich, A.; Cowie, B.; Qi, D.; Nijhuis, C. A. Chemical Science 2021, 12 (7), 2381-2388, 10.1039/D0SC04555A. DOI: 10.1039/D0SC04555A. (66) Zhang, X.; Palamarciuc, T.; Létard, J.-F.; Rosa, P.; Lozada, E. V.; Torres, F.; Rosa, L. G.; Doudin, B.; Dowben, P. A. Chemical Communications 2014, 50 (18), 2255-2257, 10.1039/C3CC46892E. DOI: 10.1039/C3CC46892E. Page 23 of 24 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A (67) Lefter, C.; Tan, R.; Dugay, J.; Tricard, S.; Molnár, G.; Salmon, L.; Carrey, J.; Nicolazzi, W.; Rotaru, A.; Bousseksou, A. Chemical Physics Letters 2016, 644, 138-141. DOI: https://doi.org/10.1016/j.cplett.2015.11.036. (68) Minakova, O. V.; Tumanov, S. V.; Fedin, M. V.; Veber, S. L. Russian Journal of Coordination Chemistry 2020, 46 (5), 326-329. DOI: 10.1134/S1070328420040041. (69) Hao, G.; Mosey, A.; Jiang, X.; Yost, A. J.; Sapkota, K. R.; Wang, G. T.; Zhang, X.; Zhang, J.; N'Diaye, A. T.; Cheng, R.; et al. Applied Physics Letters 2019, 114 (3), 032901. DOI: 10.1063/1.5054909 (acccessed 2022/06/29). (70) Sánchez-de-Armas, R.; Montenegro-Pohlhammer, N.; Develioglu, A.; Burzurí, E.; Calzado, C. J. Nanoscale 2021, 13 (44), 18702-18713, 10.1039/D1NR04577F. DOI: 10.1039/D1NR04577F. (71) Li, F.; Huang, J.; Hu, Y.; Li, Q. RSC Advances 2019, 9 (22), 12339-12345, 10.1039/C9RA01420A. DOI: 10.1039/C9RA01420A. (72) Li, D.; Tong, Y.; Bairagi, K.; Kelai, M.; Dappe, Y. J.; Lagoute, J.; Girard, Y.; Rousset, S.; Repain, V.; Barreteau, C.; et al. The Journal of Physical Chemistry Letters 2022, 13 (32), 7514-7520. DOI: 10.1021/acs.jpclett.2c01934. (73) Yan, Q.; Zhou, L.; Cheng, J.-F.; Wen, Z.; Han, Q.; Wang, X.-F. The Journal of Chemical Physics 2016, 144 (15), 154304. DOI: 10.1063/1.4946803 (acccessed 2022/06/29). (74) Niu, L.; Wang, H.; Bai, L.; Rong, X.; Liu, X.; Li, H.; Yin, H. Frontiers of Physics 2017, 12 (4), 127207. DOI: 10.1007/s11467-017-0671-0. (75) Hu, Y.; Li, X.; Li, Q.; Yang, J. Angewandte Chemie International Edition 2022, n/a (n/a), e202205036, https://doi.org/10.1002/anie.202205036. (acccessed 2022/06/29). (76) Aragonès, A. C.; Aravena, D.; Cerdá, J. I.; Acís-Castillo, Z.; Li, H.; Real, J. A.; Sanz, F.; Hihath, J.; Ruiz, E.; Díez-Pérez, I. Nano Letters 2016, 16 (1), 218-226. DOI: 10.1021/acs.nanolett.5b03571. (77) Solomon, G. C.; Herrmann, C.; Hansen, T.; Mujica, V.; Ratner, M. A. Nature Chemistry 2010, 2 (3), 223- 228. DOI: 10.1038/nchem.546. (78) Liu, J.; Huang, X.; Wang, F.; Hong, W. Accounts of Chemical Research 2019, 52 (1), 151-160. DOI: 10.1021/acs.accounts.8b00429. (79) Huang, B.; Liu, X.; Yuan, Y.; Hong, Z.-W.; Zheng, J.-F.; Pei, L.-Q.; Shao, Y.; Li, J.-F.; Zhou, X.-S.; Chen, J.- Z.; et al. Journal of the American Chemical Society 2018, 140 (50), 17685-17690. DOI: 10.1021/jacs.8b10450. (80) Jiang, F.; Trupp, D. I.; Algethami, N.; Zheng, H.; He, W.; Alqorashi, A.; Zhu, C.; Tang, C.; Li, R.; Liu, J.; et al. Angewandte Chemie International Edition 2019, 58 (52), 18987-18993, https://doi.org/10.1002/anie.201909461. (acccessed 2022/09/21). (81) Wagner, S.; Kisslinger, F.; Ballmann, S.; Schramm, F.; Chandrasekar, R.; Bodenstein, T.; Fuhr, O.; Secker, D.; Fink, K.; Ruben, M.; et al. Nature Nanotechnology 2013, 8 (8), 575-579. DOI: 10.1038/nnano.2013.133. (82) Johannsen, S.; Ossinger, S.; Markussen, T.; Tuczek, F.; Gruber, M.; Berndt, R. ACS Nano 2021, 15 (7), 11770-11778. DOI: 10.1021/acsnano.1c02698. (83) Huang, J.; Xie, R.; Hu, Y.; Lei, S.; Li, Q. Chemical Physics Letters 2020, 758, 137925. DOI: https://doi.org/10.1016/j.cplett.2020.137925. (84) Liu, M.; Han, X.; Huang, H.; Long, X.; Tan, B. Chemical Physics Letters 2022, 801, 139682. DOI: https://doi.org/10.1016/j.cplett.2022.139682. Page 24 of 24Dalton Transactions Dalton Transactions Accepted Manuscript Published on 28 December 2022. Downloaded by Gral Universidad Sevilla on 1/3/2023 5:51:24 PM. View Article Online DOI: 10.1039/D2DT02598A