Engineering reversible isomerization at the nanoscale via intermolecular interactions

Understanding isomerization in nanoparticles at the atomic level is critical to expanding diversity of nanomaterials. In this issue Chem, Xie, Häkkinen, and co-workers describe a new approach realizing reversible isomeric transformation an atomically precise gold nanocluster by engineering intermolecular interactions between cationic surfactants anionic ligands on cluster surface. Isomers, formally defined as molecular entities with identical chemical formulae but different structures, have continued fascinate chemists since late 1820s, when they were first observed. This because even slight differences arrangement constituent atoms are found evoke profound molecule’s properties functions. As result, efforts understand relationships that exist isomers (including mechanisms isomerization) continue gather interest. This, turn, has significantly enriched chemistry small organic molecules coordination complexes scale. contrast, analogous transformations larger length scales (e.g., bulk inorganic solids) known proceed through solid-solid phase transitions via poorly understood complex pathways. context, key question how structure transforms intermediate nanometer With advent nanotechnology mid-1980s, considerable research been devoted mapping out processes involved sizes recent decades.1Chen C.-C. Herhold A.B. Johnson C.S. Alivisatos A.P. Size dependence structural metastability semiconductor nanocrystals.Science. 1997; 276: 398-401Crossref PubMed Scopus (525) Google Scholar,2Williamson C.B. Nevers D.R. Nelson A. Hadar I. Banin U. Hanrath T. Robinson R.D. Chemically clusters.Science. 2019; 363: 731-735Crossref (42) Scholar However, such endeavors severely impeded two main factors: (1) unlike small-molecule chemistry, where precision purity typical, nanochemistry continues suffer from inherent polydispersity issues, wherein highest-quality monodisperse nanocrystal samples routinely exhibit ∼5% polydispersity; (2) it difficult unravel intrinsic (especially surface ligand binding modes) using current tools. From perspective, progress over last 15 years synthesis, characterization (at single-crystal X-ray crystallography), theoretical studies ligand-protected metal nanoclusters created unique opportunities for analyzing nanoscale precision.3Jin R. Zeng C. Zhou M. Chen Y. Atomically colloidal nanoparticles: fundamentals opportunities.Chem. Rev. 2016; 116: 10346-10413Crossref (1843) Although ranging size ∼1 3 nm can be viewed nanoparticles, these strong quantum-confinement effects molecular-like properties. These characteristics, make ideal candidates investigating which transition occurs. Both stereoisomerism isomerism observed previous research, although former more common.4Knoppe S. Bürgi Chirality thiolate-protected clusters.Acc. Chem. Res. 2014; 47: 1318-1326Crossref (292) Scholar,5Kang X. Zhu M.Z. Structural nanoclusters.Chem. Mater. 2021; 33: 39-62Crossref (21) Out few reports isomerism, most typically one-way irreversible thermodynamically preferred isomers. On other hand, several “quasi-structural isomers” clusters synthesized exchange reactions, share same formula terms number total (if carbon tails ignored).5Kang decouple while quasi-isomers. Very recently, temperature- solvent-induced isomerization, involves breakage formation specific bonds structure, disclosed.6Qin Z. Zhang J. Wan Liu Abroshan H. Jin Li G. rotary nanomotors.Nat. Commun. 2020; 11: 6019Crossref (35) Scholar,7Xia N. Yuan Liao L. W. Deng Yang Wu oscillation revealed nanoparticles.J. Am. Soc. 142: 12140-12145Crossref (25) development chemically controllable widely applied induce currently lacking. introduced surfactant-mediated strategy bring about structurally resolved, well-studied Au25(p-MBA)18 (where p-MBA = para-mercaptobenzoic acid) nanocluster.8Cao Malola Matus M.F. Yao Q. Shi Häkkinen Xie Reversible induced interaction.Chem. 7: 2227-2244Abstract Full Text PDF (15) Specifically, addition removal cetylammonium cations (CTA+), their (i.e., CH…Π interactions) tailored effect forms aqueous (Figure 1). Through combination experimental computational studies, authors provide in-depth analysis kinetics mechanism transformation, well propose isomer Au25(SR)18 analog, was recently theoretically predicted9Matus Kinder Bonilla E. Barngrover B.M. Aikens C.M. A topological Au25(SR)18- nanocluster.Chem. 56: 8087-8090Crossref subsequently gas phase.10Kalenius Kazan Experimental confirmation ubiquitous phase.J. 143: 1273-1277Crossref (14) combining zeta-potential UV-visible spectroscopy, successfully identified conditions each 1A). The study reaction process initiated or CTA+ routine first-order coherent without any observable intermediates (molecular-isomerization-like)2Williamson activation energy 1.16 1.17 eV, respectively. further performed density functional theory calculations models derived diffraction patterns optical confirm occurs displacive reconfiguration icosahedral Au13 core (reminiscent transitions)1Chen breaking Au-thiolate (hence, low barriers). To gain mechanistic insights into level, 1H-NMR dynamics simulations, rigid shell triggers simple rotation 1B), resulting generation topologically related isomer. Encouraged success phase, then attempted achieve phase. case, replaced TOA+ (tetraoctylammonium) used protected 4-mercaptophenylacetic acid (p-MPA) precisely tune replicate toluene. summary, provides proof principle controlled nanocluster. investigated only one Au25 nanocluster, showcase versatility method demonstrating thiolate both phases. Application straightforward technique types mixed monolayer-protected clusters) should underlying transformations. Lastly, worthwhile emphasize realm nanoclusters, “every atom counts” (in determining properties), pioneering offers yet powerful way control “the position every atom” could greatly broaden scope class materials coming years. interactionCao et al.ChemJuly 16, 2021In BriefCao al. demonstrate tuning interaction. By coupling/decoupling interaction surface-adsorption layer external ligands, realized solution. work proposes making possible expand tunability physical various applications. Full-Text Open Archive