Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

Abstract

The ability to use mechanical strain to steer chemical reactions creates completely new opportunities for solution‐ and solid‐phase synthesis of functional molecules and materials. However, this strategy is not readily applied in the bottom‐up on‐surface synthesis of well‐defined nanostructures. We report an internal strain‐induced skeletal rearrangement of one‐dimensional (1D) metal–organic chains (MOCs) via a concurrent atom shift and bond cleavage on Cu(111) at room temperature. The process involves Cu‐catalyzed debromination of organic monomers to generate 1,5‐dimethylnaphthalene diradicals that coordinate to Cu adatoms, forming MOCs with both homochiral and heterochiral naphthalene backbone arrangements. Bond‐resolved non‐contact atomic force microscopy imaging combined with density functional theory calculations showed that the relief of substrate‐induced internal strain drives the skeletal rearrangement of MOCs via 1,3‐H shifts and shift of Cu adatoms that enable migration of the monomer backbone toward an energetically favorable registry with the Cu(111) substrate. Our findings on this strain‐induced structural rearrangement in 1D systems will enrich the toolbox for on‐surface synthesis of novel functional materials and quantum nanostructures.

On-Surface Synthesis with Atomic Hydrogen

“…Most often, this intermediate is not stable at the reaction temperature, so that the reaction proceeds toward a nonplanar reductive elimination yielding the final carbon–carbon coupling. 25 However, in some cases, this intermediate state is stable enough to be observed or even manipulated, 26 for instance, on copper surfaces 27 or when intermolecular steric crowding is large preventing the final C–C coupling. In this work, we deposited TBPDT ( Figure 3 ) on the Au(111) surface.…”

On-Surface Synthesis of Polypyridine: Strain Enforces Extended Linear Chains

“…The close-packed Cu(111) surface was observed to steer the formation of covalent macrocycles, while Cu(110) favors the growth of extended structures [11,12]. Substrate-induced internal strain can drive the skeletal rearrangement of an extended 1D metal-organic chain, enabling the formation of an energetically favorable registry with the Cu(111) substrate [13]. Intramolecular strain relief represents another appealing approach to promote the formation of desired molecular products as the on-surface planarization of distorted polycyclic aromatic hydrocarbons [14] and the synthesis of nanographene [15,16].…”

Heterocyclic Mechanophores in Polymer Mechanochemistry

“…The weak bonds are defined as chemical bonds with a bond dissociation energy (BDE) of less than 72 kcal mol -1 ; they are generally found in acyclic structures. These include covalent bonds such as diazo, 23,47 C-S, [48][49][50] C-C (in tetraarylsuccinonitrile), 25,28,[51][52][53][54][55][56] C-O, 50,57,58 S-S, [59][60][61][62] (Figure 2a), and coordinative bonds such as Ru-, Ag-or Cu-carbene bonds, 16,63 Fe-Cp (in ferrocene), [64][65][66] Pt-acetylide, 67 Fe-pyridine, 68 Cunaphthalene, 69 Pd-phosphine, 70 and Pd-carbene (Figure 2b). 71 Covalent bonds in strained ring structures have lower BDEs than the analogous linear structures and can respond to mechanical forces.…”