Long-Range Orientational Self-Assembly, Spatially Controlled

Sep 10, 2017 - Expanded porphyrins are large-cavity macrocycles with enormous potential in coordination chemistry, anion sensing, photodynamic therapy...
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Long-Range Orientational Self-Assembly, Spatially Controlled Deprotonation, and Off-Centered Metalation of an Expanded Porphyrin Borja Cirera,† Olga Trukhina,‡ Jonas Björk,§ Giovanni Bottari,†,‡,∥ Jonathan Rodríguez-Fernández,⊥ Alberto Martin-Jimenez,† Mikhail K. Islyaikin,# Roberto Otero,†,⊥ José M. Gallego,∇ Rodolfo Miranda,†,⊥ Tomás Torres,*,†,‡,∥ and David Ecija*,† †

IMDEA Nanoscience, 28049 Madrid, Spain Department of Organic Chemistry, Universidad Autónoma de Madrid, 28049 Madrid, Spain § Department of Physics, Chemistry and Biology, IFM, Linköping University, 58183 Linköping, Sweden ∥ Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain ⊥ Department of Condensed Matter Physics, Universidad Autónoma de Madrid, 28049 Madrid, Spain # IRLoN, Research Institute of Macroheterocycles, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia ∇ Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid, Spain ‡

S Supporting Information *

ABSTRACT: Expanded porphyrins are large-cavity macrocycles with enormous potential in coordination chemistry, anion sensing, photodynamic therapy, and optoelectronics. In the last two decades, the surface science community has assessed the physicochemical properties of tetrapyrrolic-like macrocycles. However, to date, the sublimation, self-assembly and atomistic insights of expanded porphyrins on surfaces have remained elusive. Here, we show the self-assembly on Au(111) of an expanded aza-porphyrin, namely, an “expanded hemiporphyrazine”, through a unique growth mechanism based on long-range orientational self-assembly. Furthermore, a spatially controlled “writing” protocol on such self-assembled architecture is presented based on the STM tip-induced deprotonation of the inner protons of individual macrocycles. Finally, the capability of these surface-confined macrocycles to host lanthanide elements is assessed, introducing a novel off-centered coordination motif. The presented findings represent a milestone in the fields of porphyrinoid chemistry and surface science, revealing a great potential for novel surface patterning, opening new avenues for molecular level information storage, and boosting the emerging field of surface-confined coordination chemistry involving fblock elements.

1. INTRODUCTION

physicochemical characteristics of smaller porphyrinoids by augmenting the number of conjugated π electrons. Simultaneously, porphyrinoid derivatives have drawn the interest of the surface science community,3,4 which, equipped with state of the art scanning probe microscopies and complemented by photoemission spectroscopies and DFT calculations, has studied corroles,5,6 porphycenes,7−9 porphyrins,10−23 subphthalocyanines,24,25 phthalocyanines,26−29 and naphthalocyanines.30 This topic of research is currently quite broad including self-assembly,3,4 on-surface synthesis,20,31−33 electronic structure,3,4 in situ metalation,34−38 information storage and electronic switching, 9,30,36,39 nanomagnetism,18,40−42 electroluminescence,13,43,44 ligation of axial ad-

Since the beginning of the twentieth century porphyrinoids have attracted widespread attention due to their role in biological processes and their potential for applications including light harvesting, sensing and catalysis. Within this family of chemical compounds, tetrapyrrolic-like species such as porphyrins and phthalocyanines have been widely addressed. Sessler coined the term “expanded porphyrin” to refer to “macrocyclic compounds containing heterocyclic units (pyrrole, furan, or thiophene-like) linked together, either directly or through spacers, so that the internal ring pathway contains at least 17 atoms”.1,2 Steered by the enormous relevance of these compounds, an important line of research in organic chemistry and materials science has been focused in synthesizing such large macrocycles, aiming at modulating and improving the © 2017 American Chemical Society

Received: June 20, 2017 Published: September 10, 2017 14129

DOI: 10.1021/jacs.7b06406 J. Am. Chem. Soc. 2017, 139, 14129−14136

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Journal of the American Chemical Society

Figure 1. Self-assembly and electronic structure of HTAP on Au(111). (a) Ball and stick model of HTAP in the gas phase using AM1 method within Hyperchem software package. Carbon atoms are depicted in green, nitrogen atoms in violet, sulfur atoms in yellow and hydrogen atoms in white. (b) STM image of HTAP decorating the Au(111) elbows and fcc regions (image size 500 × 500 Å2, Vbias = 1.5 V). White lines depicts the surface high symmetry directions. (c) High resolution STM image of an individual HTAP species (image size 33 × 33 Å2, Vbias = 1.5 V). (d) DFT calculated geometry (top and side view) of the adsorption of HTAP on Au(111). (e) STS measurements of clean Au(111) (gray line), an individual HTAP species (green line), and HTAP(−3H) (blue line), the latter two taken above the center of the macrocycle. (f) dI/dV map at constant height illustrating the shape of the LUMO (image size 33 × 33 Å2, Vbias = 1.5 V, Vmodulation = 30 mV). (g) Contour plot of the calculated electron density of the LUMO of an isolated HTAP molecule in the gas phase.

ducts,18,19,45−47 and catalysis.48−51 However, despite the envisioned potential of expanded porphyrinoids, all reported studies on surfaces have been limited to tetrapyrrolic-like or smaller macrocycles. Here, we present an in-depth investigation of an expanded porphyrinoid, i.e., [30]trithia-2,3,5,10,12,13,15,20,22,23,25,30dodecaazahexaphyrin,52 hereafter referred to as HTAP, deposited on a Au(111) surface. HTAP belongs to a family of macrocycles that can be considered as “expanded hemiporphyrazines” or even “expanded subphthalocyanines”52−54 and which structure was unambiguously established by some of us by X-ray analysis.55 We show here that HTAP self-assembles on Au(111), revealing a unique orientational order. In addition, it is possible to remove the three inner protons of the macrocycle in a selective fashion by applying voltage pulses with the STM tip. This process is highly localized and occurs without perturbing neighboring molecular species, thus propelling new avenues for information storage applications. Finally, the capability of HTAP to host dysprosium, a lanthanide metal element, is assessed, revealing an unprecedented off-centered coordination motif of great potential for sensing and catalysis.

ultrahigh vacuum system that hosted an Omicron scanning tunneling microscope. The base pressure was kept below 1 × 10−10 mbar. The Au(111) substrate was prepared using standard cycles of Ar+ sputtering (800 eV) and subsequent annealing to 723 K for 10 min. HTAP species were synthesized according to protocol described in ref 55 and deposited by organic molecular beam epitaxy (OMBE) from quartz crucibles held at 473 K on a pristine Au(111) substrate held at room temperature. Dysprosium atoms were deposited by means of electron-beam evaporation on the sample held at room temperature from an outgassed dysprosium rod (99.5% MaTecK GmbH), and subsequently the sample was gentle annealed to 373 K. All STM images were taken in constant-current mode with an electrochemically etched tungsten tip and at 4 K. Vbias in tunneling conditions was applied to the sample. 2.2. Computational Details. Periodic density functional theory (DFT) calculations were performed with the VASP code,56 using the projector-augmented wave method,57 and plane waves expanded to a kinetic energy cutoff of 400 eV. To treat the problem of DFT to handle f-electrons (due to self-interaction errors), a PAW potential with the f-electrons partly frozen in the core was used; nine f-electrons were kept frozen in the core, treating the dysprosium with a valence of +3. Exchange-correlation effects were described by the van der Waals density functional (vdWDF)58 using the version by Hamada denoted as rev-vdWDF2.59 The Au(111) surface was represented by a four layered slab, and a p(9 × 9) surface unit cell together with a 3 × 3 kpoint sampling. Transition states were found using the climbing image nudged elastic band60 and Dimer61 methods. All structures were optimized until the forces on all atoms, except the two bottom layers of the Au slabs, were smaller than 0.01 eV/Å. STM images were

2. METHODS 2.1. Experimental Details. The scanning tunneling microscopy (STM) experiments were performed using a custom designed 14130

DOI: 10.1021/jacs.7b06406 J. Am. Chem. Soc. 2017, 139, 14129−14136

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Figure 2. Substrate-mediated orientational growth of HTAP on Au(111). (a) Long-range and (b) high resolution STM images of low molecular coverage ((a) image size 500 × 500 Å2, Vbias = 1.5 V; (b) image size 300 × 300 Å2, Vbias = 1.5 V). (c) Long-range and (d) high resolution STM images of medium molecular coverage ((c) image size 500 × 500 Å2, Vbias = −0.5 V; (d) image size 215 × 215 Å2, Vbias = −0.5 V). In (c), blue lines highlight the edges of one domain of the herringbone reconstruction. (e) Long-range and (f) high resolution STM images of high molecular coverage ((e) image size 500 × 500 Å2, Vbias = −0.5 V; (f) image size 137 × 137 Å2, Vbias = −0.5 V). In (a), (c), and (e), green or blue triangles are superimposed on some molecules to facilitate the visualization of the two orientations adopted by the HTAP molecules. simulated with the Tersoff−Hamann approximation62 with the implementation by Lorente and Persson.63

strips, whereas the thiadiazoles appears as a bright lobes (Figure 1f). The shape of the LUMO orbital matches well to that resulting from DFT calculations of HTAP in the gas phase (Figure 1g). Next, we have inspected the growth of HTAP on Au(111) as a function of the molecular coverage (Figures 2 and S1). We start from a very low coverage regime in which HTAP species just decorate elbows and fcc regions (Figure 1b and S1a). Previous reports have assessed the affinity of fcc regions for the selective hosting of molecular species,64−68 a phenomenon attributed to a higher reactivity of these regions.69 Upon increasing the deposition of HTAP, the alignment of the macrocycles on the fcc regions into one preferred orientation is observed, together with the formation of supramolecular dimers, trimers and higher homologues (Figure 2a,b). In addition, isolated molecules are identified on the hcp regions. It is worth to note that (i) nearly all the macrocycles display the same orientation in the fcc regions and the opposite orientation in the hcp regions of the surface and (ii) this order is maintained over several length scales. These findings suggest that the specific orientation of the molecule is mainly dictated by the surface crystallographic structure (either fcc or hcp), which is qualitatively corroborated by DFT simulations (Figure S2). Further increasing the HTAP coverage leads to the formation of supramolecular rows that cover the fcc regions longitudinally with a width of one or two molecules (Figure 2c,d). In addition, the hcp regions host isolated molecules, coexisting, in few cases, with supramolecular dimers. A subsequent increase of the molecular coverage leads to the full decoration of the fcc and hcp regions by supramolecular rows with a width of two and one molecule, respectively (Figure 2e,f). Occasionally, at the elbows of the herringbone

3. RESULTS AND DISCUSSION 3.1. Long Range Orientational Order. HTAP is a 30-π electron, heteromacrocycle presenting a 27-atom internal cavity and composed by three diiminoisoindoline and 2,5-diamino1,3,4-thiadiazole moieties N-fused between them in an alternating fashion (Figure 1a). The deposition of minute amounts of this macrocycle on pristine Au(111) gives rise to the decoration of the elbows and the fcc region of the herringbone reconstruction by isolated molecules (Figure 1b). HTAP presents a triangular shape, exhibiting six bright lobes which are assigned to the three isoindole and the three thiadiazole moieties, and a cavity in its center (Figure 1c). Note that the molecular species display two different orientations with respect to the substrate related by a 60° rotation. DFT calculations of the minimum energy configuration of an isolated molecule reveal an almost flat adsorption geometry of HTAP on Au(111), with the edges of the molecule aligned with the high symmetry directions of the surface, in agreement with the experimental results (Figure 1d). Scanning tunneling spectroscopy measured above the cavity of an individual HTAP shows the presence of a strong resonance at 1.5 V, which is assigned to the HTAP LUMO orbital (Figure 1e, green line), while the deprotonated HTAP molecule (see below) reveals its LUMO shifted to +1.95 eV, and the simultaneous measurement of the surface state of Au(111) demonstrate the clean state of the STM tip. A dI/dV map taken at that voltage reveals the appearance of the LUMO frontier orbital, in which each isoindole moiety, situated at the corner of the triangular-shape macrocycle, is visualized as two oblique 14131

DOI: 10.1021/jacs.7b06406 J. Am. Chem. Soc. 2017, 139, 14129−14136

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Journal of the American Chemical Society reconstruction, small close-packed supramolecular islands are observed. Both supramolecular rows and islands are possibly stabilized by S···H intermolecular interactions with an experimental projected distance of 2.5 ± 0.1 Å (Figure S1b− d). Importantly, the unique orientational growth is still operative and even more pronounced at these higher molecular coverages (Figure 2c−f), affording a long-range orientational self-assembly, namely almost all (>99%) molecules at the fcc region present an opposite orientation with respect to those at the hcp region. It is worth to point out that during the growth process we observed the presence of two different HTAP species, one significantly more abundant than the other (Figure S3). The statistics reveal the preservation of the density per unit area of minority species for distinct coverages. In addition, the less abundant species could be transformed into the more abundant one by STM-tip lateral manipulation (Figure S4). Altogether, these results suggest that the observed difference in appearance arises from the location of HTAP on top of substrate defects, and that these less abundant species are protonated and have not been metalated. 3.2. Spatially Controlled Deprotonation. Once the growth features of HTAP on Au(111) were assessed, the capability of this expanded macrocycle for information storage through deprotonation was investigated. Contrary to the reported tautomerism observed on smaller porphyrinoids, which show a telegraphic current as typical fingerprint,30,39 no such effect was detected by positioning the STM tip on top of the HTAP cavity while measuring tunneling current versus time for distinct bias voltages, thus suggesting that such tautomerism is not occurring for HTAP adsorbed on Au(111). A possible explanation is the absence of unprotonated pyrrole moieties in HTAP. The macrocycle, however, could be deprotonated in its inner cavity, partially or completely, by applying voltage pulses above a threshold of +2.7 V, either by maintaining a perturbative voltage over time or by applying a voltage ramp surpassing such threshold (Figure 3). Most of the manipulation attempts ended up with the full deprotonation of the cavity of the macrocycle, i.e., the loss of three internal protons. However, in few cases, starting from HTAP (Figure 3a), and using the voltage ramp procedure, it was possible to remove one (Figure 3b), two (Figure 3c), and three (Figure 3d) protons from the macrocycle, leading to HTAP(-1H), HTAP(-2H) and HTAP(-3H) species, respectively. DFTsimulated STM images of the three deprotonated HTAP species matched well the experimental ones (Figure S5), supporting our assignment. The stepwise deprotonation of HTAP to HTAP(−3H) is also illustrated in Figure 3e in which the changes in the tunneling current as a function of the bias voltage applied at the center of HTAP species is reported. The three abrupt decreases in the tunneling current upon increasing the voltage are associated each to the loss of one proton from the inner cavity. HTAP and its fully deprotonated analog HTAP(−3H) are significantly different not only from the topographic point of view (Figure 3f,g), but also from the electronic one. As demonstrated by the STS spectra, their respective LUMOs are shifted in energy (Figure 1e) and show a clearly different spatial organization (Figure 3h,i). Remarkably, the deprotonation turned out to be a process strictly localized at the single molecule level as the removal of inner protons of adjacent species was not observed (Figure 3f,g). Thus, the deprotonation mechanism is assigned to

Figure 3. Sequential and full deprotonation of HTAP inner cavity by STM tip-induced voltage pulses. (a-d) STM images (top) and associated ball-and-stick models (bottom) of (a) Au(111)-supported HTAP and deprotonated species (b) HTAP(-1H), (c) HTAP(-2H), and (d) HTAP(-3H) (Vbias = −0.5 V, voltage pulse = 2.8 V). (e), Current versus voltage plot upon applying a bias voltage ramp above the center of a HTAP macrocycle. (f,g) STM images (top) and associated ball-and-stick models (bottom) of the removal of three protons of a HTAP species after applying a voltage pulse of 2.8 V above the center of the HTAP macrocycle located at the right-hand side (f), which gives rise to the fully deprotonated HTAP(-3H) species (g). (h,i) dI/dV maps taken at 1.5 and 1.95 V, respectively, illustrating the differences in the electronic structure between the pristine HTAP macrocycle (left) and the fully deprotonated HTAP(-3H) (right).

tunneling electrons,30,39 neglecting a primary role of the electric field exerted by the STM tip to the sample. We exclude conformational changes of the isoindole moieties as the reason for the changes in the STM visualization of the molecular species observed above, which is corroborated by our STM-simulated images (Figure S5). The macrocycle is very rigid and the rotation of the isoindole moieties is not feasible, or at least not expected to be sufficient to cause such changes in their brightness. The uniqueness of the HTAP structure resides in the synthetic coupling together of six heterocycle units instead the four typical of porphyrinoids to diminish the 14132

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Figure 4. Sequential, spatially controlled full inner cavity deprotonation of HTAP. (a−d) Sequence of STM images showing the “writing” of 43 HTAP molecules within a supramolecular row realized through the controlled deprotonation of HTAP (image size 450 × 450 Å2, Vbias = −0.5 V. (e) Sequence of high resolution STM images illustrating the deprotonation of 12 HTAP molecules by applying voltage pulses of 2.8 V on top of each macrocycle (image size 123 × 123 Å2, Vbias = −0.5 V). The first and last STM images in (e) are zooms of the regions in (a) and (b) identified as a green and a blue square, respectively.

to tetrapyrrolic macrocycles. Inspired by this potential, the capability of HTAP to host lanthanide elements was investigated. In this context, we have chosen dysprosium as complexed element due to its potential for magnetism and light emission applications. To this end, a submonolayer of HTAP held at 300 K was exposed to a minute flux of dysprosium atoms, and subsequently the sample annealed to 373 K to promote the macrocycles’ metalation. STM images recorded after this procedure show the predominant presence of novel species (Figure 5a,b, gray circle), coexisting with few pristine HTAP molecules (Figure 5a,b, blue circle). While probing at Vbias = 2 V, the new species show the presence of six lobes as in the case of pristine HTAP (Figure 1c), but presenting two markedly bright thiadiazole subunits and an inner off-centered spot (Figure 5c). Furthermore, scanning these macrocycles with a molecular tip shows the presence of a protrusion located off-centered with respect to the cavity which is identified as a dysprosium atom, establishing a unique coordination motif (Figure S6). As illustrated in Figure 5a, the in situ metalation of HTAP by dysprosium is successful and very efficient on Au(111). Scanning tunneling spectroscopy with a metallic tip recorded above the isoindole moiety, the thiadiazole subunits, and the cavity of the metalated HTAP reveals specific characteristics (Figure S7). On one hand, the isoindole and the thiadiazole moieties exhibit one clear peak centered at ∼1.0 V and the emission from the surface state of Au(111) still detectable through the molecule. On the other hand, the spectrum recorded above the cavity of the metalated HTAP presents a small shoulder at ∼1.1 V and a sharp increase above 1.5 V, without defined peaks (Figure S7a, green curve). To elucidate the spatial distribution of the orbitals in such metalated species, dI/dV mapping at constant current and selected bias were carried out. Maps taken at 1.0 (Figure 5d),

macrocycle strain. The planarity and rigidity of this kind of macrocycles have been pointed out by some of us by X-ray analysis.55 Thus, a saddle-shape deformation or alike conformations involving the isoindole moieties as in the porphyrin case is not foreseen. Stimulated by the high degree of local selectivity observed for the HTAP deprotonation, a “writing” protocol was tested on a two-molecule wide supramolecular row. The process starts by positioning the STM tip on top of the cavity of a selected HTAP molecule within the supramolecular row (Figure 4a) and applying a voltage pulse of 2.8 V. As a result, the full and selective deprotonation of one single HTAP macrocycle was observed. The same process was then repeated each time moving from the deprotonated macrocycle to a vicinal and pristine HTAP molecule (Figure 4 and Supporting Information Video). The efficiency and selectivity of the presented single molecule “writing” protocol overcomes any concomitant problem associated with perturbing neighbor molecules observed in the case of smaller macrocycles,8,39 and paves new avenues for information storage. 3.3. Off-Centered Metalation by Dysprosium. Finally, the presence in HTAP of a large cavity endowed with 15 nitrogen and 12 carbon atoms prompted us to study the complexation capability of this macrocycle. In this context, a HTAP analog bearing three peripheral tert-butyl groups is capable of accommodating three d-block metal ions and suggests potential to host large metals such as rare-earths.53 Lanthanide porphyrins bear promises for light emitting materials,70−72 luminescent probes,73 optical limiting materials,71 sensitive devices,74 and radiation and photodynamic therapy.75 In addition, there is a great interest devoted to the in situ metalation of surface-confined porphyrinoids, due to their capabilities for optoelectronics, sensing and nanomagnetism,3,37,38 though up to now reported results have been limited 14133

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Figure 5. In situ metalation of HTAP species by dysprosium atoms. (a) High resolution STM image (left panel) and dI/dV maps at constant current taken at 1.5 V (middle panel) and 2.0 V (right panel) of the in situ metalation of HTAP by dysprosium atoms. Image size 205 × 205 Å2, Vbias = 2.0 V. (b,c) High resolution STM images of the in situ metalation of HTAP species. (b) Image size 118 × 118 Å2, Vbias = 2.0 V. (c) Image size 30 × 30 Å2, Vbias = 2.0 V. (d,e) dI/dV maps of (c) taken at +1.0 V (d), +1.5 V (e), and +2.0 V (f). (g) DFT-calculated asymmetric metalation reaction of HTAP by dysprosium on Au(111). Top and side views of dysprosium-centered HTAP (S0), dysprosium off-centered HTAP(-1H) (S1), dysprosium offcentered HTAP(-2H) (S2), and dysprosium off-centered HTAP(-3H) (S3), and transitions state TS1 (going from S0 to S1), TS2 (going from S1 to S2), and TS3 (going from S2 to S3). Below the three structures and the three transition states, the respective energy profiles (in eV) are represented. Peripheral hydrogen atoms are depicted in white, inner hydrogen atoms in red, carbon atoms in gray, nitrogen atoms in dark blue, sulfur atoms in dark yellow, gold atoms in light yellow, and dysprosium atoms in light blue.

1.5 (Figure 5a,e), and 2.0 V (Figure 5f) reveal the aspect of the frontier orbitals of dysprosium−metalated HTAP that are tentatively assigned to the LUMO and higher unoccupied molecular orbitals. Note that the LUMO orbital of the dysprosium-metalated molecule is downward shifted to +1.0 eV and its spatial distribution shows clearly only two protrusions instead of three as in the pristine HTAP molecule (compare with Figure 1f). The dI/dV maps at 1.5 and 2.0 V reveal a bright protrusion that is unambiguously attributed to the presence of dysprosium.

Due to the off-centered dysprosium coordination and the variation of the molecule−substrate interaction, up to six molecular orientations of the metalated macrocycle with respect to the surface are observed. Remarkably, the off-centered coordination motif has great potential for sensing and catalysis since it will allow multimodal geometric and electronic interactions with the axial/lateral chemical adducts, thus playing an important role in regulating the involved physicochemical mechanisms. Furthermore, complexation of an additional metal ion within the large cavity 14134

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of these macrocycles could be envisioned, which would be highly desirable for building multicolor probes in which the luminescent properties of the lanthanide ion could be tailored by the presence of a second metal ion. Next, the metalation process and off-centered coordination motifs were investigated by DFT calculations, which results support our claims. Figure 5g shows a pristine HTAP macrocycle with a dysprosium atom located in its center (S0), the off-centered metalated and monodeprotonated transition state (TS1), and the final relaxed off-centered configuration (S1). The STM simulated image of this latter configuration (Figure S8) agrees well with experimental topography. The off-centered metalation process is found to be exothermic by −0.27 eV with an activation energy of 0.76 eV to go from S0 to S1. Further deprotonation steps on such dysprosium−metalated, monodeprotonated HTAP leading to S2 and S3 species are associated with significantly higher activation energies: 1.95 and 1.72 eV to remove the second and the third inner proton, respectively (Figure 5g). Furthermore, the complete dehydrogenation of the off-centered dysprosium metalated HTAP is highly endothermic with an overall reaction energy of 2.57 eV. In addition, theoretical calculations showed that a hypothetical dysprosium-centered metalated HTAP species (Figure S9, S0) relaxes into the off-centered configuration after loss of one proton (Figure S8, S1) and would be highly endothermic (3.00 eV) and even more energetically unfavorable for the full inner dehydrogenation (Figure S9). It should also be noticed that the loss of one inner proton in pristine HTAP in the absence of dysprosium has an activation energy of 1.93 eV (Figure S10), explaining why thermally activated deprotonation of HTAP was not observed on the pristine Au(111) surface. In summary, the in situ metalation of HTAP results in a dysprosium atom located off-center with respect to the macrocycles cavity, coordinated to the surface, but also protruding to the vacuum, which we envision could have potential for optoelectronics, nanomagnetism, sensing and catalysis applications.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b06406. DFT calculations, STM images, and STS data of additional results (PDF) Video showing full and selective deprotonation of several, adjacent HTAP macrocycles within a supramolecular row (AVI)



AUTHOR INFORMATION

Corresponding Authors

*[email protected] *[email protected] ORCID

Jonas Björk: 0000-0002-1345-0006 Giovanni Bottari: 0000-0001-6141-7027 David Ecija: 0000-0002-8661-8295 Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS Work supported by the Spanish Ministerio de Economia y Competitividad (MINECO) (RYC-2012-11133, FIS 201340667-P, CTQ2014-52869-P, FIS 2015-67287-P), the Comunidad de Madrid (S2013/MIT-2841, NANOFRONTMAG, FOTOCARBON; S2013/MIT-3007, MAD2D), the European Union (FP7-PEOPLE-2011-COFUND AMAROUT II program), and the Russian Science Foundation (Project No. 1423-00204-P). Computational resources were allocated at the National Supercomputer Centre, Sweden.



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4. CONCLUSIONS We report here the first example of the adsorption and selfassembly of an expanded porphyrinoid, HTAP, on surfaces. Remarkably, HTAP is able to organize on Au(111) through a unique surface-mediated growth mechanism leading to a longrange orientational self-assembly. Furthermore, we demonstrate for such surface-supported self-assembled architectures, the possibility to remove the three macrocycle’s inner protons in a sequential and selective fashion, in a process that is highly spatially controlled. Finally, we probed the efficient in situ metalation of HTAP species by dysprosium atoms, revealing the formation of an unprecedented off-centered complexation motif which was also supported by DFT calculations. We reckon that the present study represents a milestone in the study of porphyrinoids, introducing expanded porphyrins on surfaces, and opening up great opportunities in (i) the realization of novel patterned surfaces exhibiting orientational selectivity, (ii) the preparation of single-molecule “writing” architectures for information storage applications, and (iii) the study of large macrocycles complexing f-block elements and benefiting from their unique physicochemical properties. 14135

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