On-Surface Synthesis of Na-Porphyrins Using NaCl as a Convenient Na Source

Abstract

Metallo-porphyrins with different metal centers display unique properties and are essential in various biological and chemical processes. Enormous efforts have been devoted to enriching the family of metallo-porphyrins on surfaces mainly through metalation processes within porphyrins and exogenous pure metals or intrinsic surface adatoms, which have focused on transition elements. However, less attention has been paid to the synthesis of alkali-metal-based porphyrins on a surface. Herein, by a combination of scanning tunneling microscopy (STM) imaging/manipulations and density functional theory (DFT) calculations, we report the fabrication of Na-porphyrins on Au(111) by introducing NaCl, i.e., two double-layered Na-centered porphyrins. Moreover, the interconversion between them was realized by precise STM manipulations. Our results demonstrate the feasibility of metalation by applying inorganic salt, which would serve as a promising strategy to embed intramolecular metal components into porphyrins for further functionalization and modification.

Separation of Halogen Atoms by Sodium from Dehalogenative Reactions on a Au(111) Surface

“…Based on the typical features and previous reports, , the involvement of excess Na in the assembled structure was proposed, and the corresponding DFT calculations on the structural models and STM simulations were performed (Figure S3). Accordingly, these bright dots at the junctions could be attributed to three, four, or even more Na atoms interacting with Br substituents of H-motifs in different interaction modes. The model of a typical H 3 Na 3 motif is shown in Figure c, in which each Na interacts with three Br substituents via electrostatic interactions.…”

“…It is known that halogens are able to stabilize molecular structures via electrostatic interactions, as also shown above, but are generally obstacles to further coupling processes. 11,34 Inspired by our recent studies 33,35,36 and previous reports on extrinsic metal atoms, 18−21 additional Na atoms were introduced into the above sample to test the possibility of promoting the dehalogenative reactions. Upon further deposition of Na at ∼300 K, a two-dimensional (2D) honeycomb network structure was obtained (Figure 2a).…”

Revealing the Orientation Selectivity of Tetrapyridyl-Substituted Porphyrins Constrained in Molecular “Klotski Puzzles”

“…Deposition of H 2 TPyP molecules and NaCl onto Au(111) followed by annealing at ∼510 K or above led to the formation of a close-packed chessboard structure dominantly composed of metalated Na 5 TPyP molecules . The chessboard structure is stabilized mainly by the electrostatic interactions between the peripheral pyridyl groups of H 2 TPyP-based molecules and Na derived from NaCl. ,,, In addition, with a slightly higher annealing temperature (of around 520–530 K), several dispersed cavities (with single molecules missing) naturally existed in the molecular island (cf. Figure S1).…”

“…Scheme ). Due to the intramolecular steric hindrance, the H 2 TPyP-based molecules (both intact and metalated ones) adopt a saddle-shaped adsorption geometry , on Au(111), leading to the apparently rectangular morphology in the STM images (Scheme ). Accordingly, the molecular orientations can be intuitively recognized based on the direction of the long axis of rectangles (as depicted by the blue dashed lines).…”

“…Accordingly, the molecular orientations can be intuitively recognized based on the direction of the long axis of rectangles (as depicted by the blue dashed lines). To explore the orientation selectivity of H 2 TPyP-based molecules in constrained environments, we fabricated a close-packed self-assembled chessboard structure with some naturally existing vacancies by co-deposition of H 2 TPyP molecules and sodium chloride (NaCl) onto Au(111), , in which H 2 TPyP-based molecules are aligned alternately with two orthogonal orientations (i.e., transverse and longitudinal). Interestingly, based on STM lateral manipulations, , various molecular patterns with different cavities, figuratively, the molecular “Klotski puzzles”, were artificially constructed by collecting dispersed vacancies, thus providing the possibility to investigate the orientation selectivity of H 2 TPyP-based molecules in constrained environments (Scheme ).…”