Spontaneous Intercluster Electron Transfer X^2– + X⁰ → 2 X^– (X = PtAu₂₄(SC_nH_2n+1)₁₈) in Solution: Promotion by Long Alkyl Chains

Abstract

In this work, we systematically investigated the ligand effects on spontaneous electron transfer (ET) between alkanethiolate-protected metal clusters in solution. The donor and acceptor clusters used were [PtAu 24 (SC n H 2n+1 ) 18 ] 2− (8e(Cn)) and [PtAu 24 (SC m H 2m+1 ) 18 ] 0 (6e(Cm)) (n, m = 2−16), which have icosahedral Pt@Au 12 cores with eight and six valence electrons, respectively. The ET rate constant (k ET ) from 8e(Cn) to 6e(Cm) in benzene exhibited a novel turnover behavior as a function of the total chain length n + m: the k ET decreased with n + m in the range of 4−12, whereas it monotonically increased with n + m in the range of 12−32. Electrospray ionization mass spectrometry of the mixture of 8e(Cn) and 6e(Cm) detected the dimer complex 8e(Cn)•6e(Cm), the relative population of which increased with n + m. The activation energy (E a ), determined based on the Arrhenius plots for n = m, monotonically decreased with n (≥ 6). Based on these results, we proposed that the promotion of ET by longer alkanethiolates was ascribed to two effects on the key intermediate 8e(Cn)•6e(Cm): (1) elongation of the lifetime and (2) the contraction of the distance between 8e(Cn) and 6e(Cm) due to the stronger van der Waals interaction between the longer alkyl chains. Such alkyl-chain-promoted ET is specific to ultrasmall clusters in solution because a nonuniform ligand layer could be formed due to the large curvature of the cluster core.

Unraveling a Concerted Proton-Coupled Electron Transfer Pathway in Atomically Precise Gold Nanoclusters

“…29−31 Last, unlike traditional NPs, the truly monodispersed nature of MNCs presents a solution to a longstanding challenge in accurately assessing mass action effects (i.e., concentrations) of nanomaterials on ET events. 32 As a result, the existing comprehension of PCET reactions in NPs and molecular systems cannot be readily extrapolated to MNCs, and the experimental validation of an CEPT reaction in MNCs has remained elusive thus far.…”

“…Second, MNCs typically display a core–shell structure, wherein a metal(0) kernel is surrounded by a monolayer of metal­(I)-thiolate motifs . This molecule-like structure, combined with strong quantum confinement effects, renders the PCET reactions in MNCs highly dependent on atomic structure and gives rise to unique kinetics. − Third, in contrast to large-size NPs and bulk crystals, a change of one electron in these few-atom MNCs is no longer a negligible perturbation. , Instead, it has the ability to profoundly alter the energy landscapes and influence the coupling with charge-compensating protons in interfacial ET reactions. − Last, unlike traditional NPs, the truly monodispersed nature of MNCs presents a solution to a longstanding challenge in accurately assessing mass action effects (i.e., concentrations) of nanomaterials on ET events . As a result, the existing comprehension of PCET reactions in NPs and molecular systems cannot be readily extrapolated to MNCs, and the experimental validation of an CEPT reaction in MNCs has remained elusive thus far.…”

Bottom-Up Construction of Metal–Organic Framework Loricae on Metal Nanoclusters with Consecutive Single Nonmetal Atom Tuning for Tailored Catalysis

“…Metal nanoclusters (NCs, ultrasmall metal nanoparticles) have attracted increasing interest in recent years partly due to their tunability with atomic precision. − Metal atom doping has been widely employed for tailoring the physicochemical properties of metal NCs and enabling the composition (structure)–property correlation. − However, surface nonmetal atom introduction, especially “surgery”-like single nonmetal atom doping, replacement, or addition, is challenging owing to the control difficulties. − To the best of our knowledge, surface single nonmetal atom replacement, not to mention successive surface single nonmetal atom doping, replacement, and addition, has not been previously reported. Unlike thiols and phosphines, single nonmetal atoms such as sulfur and halogen can provide more room for access by the substrates and thus facilitate catalytic reactions; − nevertheless, single nonmetal atoms might not protect NCs from attack as well as thiols or phosphines.…”