Facet-Dependent Reduction Reaction of Diruthenium Metal–String Complexes by Face-to-Face Linked Gold Nanocrystals

Abstract

The facet-dependent redox reactions of diruthenium metal–string complexes by gold nanoparticles (AuNPs) are explored by using the surface-enhanced Raman scattering (SERS) technique. Gold nano-rhombic dodecahedrons (AuRDs), gold nanocubes (AuNCs), and gold octahedrons (AuOhs) with exclusive facets {110}, {100}, and {111}, respectively, were synthesized. These AuNPs linked face-to-face by metal–string complexes Ru 2 M(dpa) 4 Cl 2 (dpa = dipyridyl amino, M = Ni, Cu) with chloride axial ligands serve as both SERS substrates and reducing agents in the reactions. We employ the diruthenium core in these complexes with multiple redox states to study the reduction ability of varied AuNP facets upon plasmonic excitation. In Ru 2 Ni(dpa) 4 Cl 2 , the Ru–Ru stretching mode ν Ru–Ru str. lies at 327 cm –1 on the SERS substrate AuOh, but this band shifts to 313 cm –1 on the AuRD and AuNC. The diruthenium moiety was reduced to [Ru 2 ] 4+ by the AuRD facet {110} and the AuNC {100}. The gold nanorods in the solution prepared with metal–string complexes bridging head-to-head on {111} facets were used for the SERS substrate. The SERS curves of the complexes in these self-assembled head-to-head rods display ν Ru–Ru str. at 327 cm –1 , which is assigned to having an [Ru 2 ] 5+ core. Hence, facets {110} and {100} have a reduction reactivity greater than that of {111}. In Ru 2 Cu(dpa) 4 Cl 2 , the ν Ru–Ru str. is observed to lie at 312 cm –1 on AuRD, but shifts to 320 cm –1 on the AuNC and AuOh. In the latter cases, the diruthenium moiety was reduced to having a charge of 4+ with electronic configuration π* 2 δ* 2 , whereas the former case band at 312 cm –1 with a weaker Ru–Ru bonding is also attributed to [Ru 2 ] 4+ but with electron configuration π* 4 . π* 4 lies at an energy greater than π* 2 δ* 2 . The electrochemical SERS spectra of diruthenium complexes were recorded to verify their oxidation states. Conclusively, these results yield the reduction reactivity of the following facet: {110} > {100} > {111}. According to the results of the redox reactions, the valence states of the diruthenium metal–string complexes are verified. In the [Ru 2 ] n + core, n = 4 π* 4 , 4 π* 2 δ* 2 , 5 π* 2...

Inhibition Of Tau Protein Aggregation By a Chaperone-like β-Boswellic Acid Conjugated To Gold Nanoparticles

“…Finally, the corresponding data planes ( hkl ) were shown (Table S1). In conclusion, these findings support a crystalline phase of the synthesized GNP being composed of an inverted spinal structure. , FESEM, HR-TEM, and the EDX map confirmed the purity of elemental gold NPs (Figure a, e, i–k) …”

Thermoinduced Metal‐to‐Metal Charge Transfer in Trinuclear Metal String Complex Ru2M(dpa)4Cl2 (M=Ni, Cu, dpa=Dipyridylamido)

“…Wu et al reported that these complexes bound to metal surfaces of various shapes of gold nanoparticles, can be reduced by nanoparticles. [16,17] They obtained two different ν RuÀ Ru frequencies, i. e., 320 and 312 cm À 1 , and assigned them to a [Ru 2 ] 4 + core; the prior band had greater wavenumbers, Ru 2 possibly has an electron configuration (π*) 2 (δ*) 2 , and the latter has (π*) 4 The TD-DFT calculations on [Ru 2 Ni(dpa) 4 Cl 2 ] yielded two low-lying transitions with vertical energies of 0.1086 and 0.1685 eV to the excited states 5 B and 5 E(1), respectively. They corresponded to the transitions σ 4 !δ 2 (d z2(Ni) !δ* from the localized MO diagram) and σ 4 !π 5 (d z2(Ni) !π*), respectively.…”

“…[13][14][15] Wu et al used Raman and surface-enhanced Raman scattering (SERS) spectroscopy to study the vibrational structures of these diruthenium complexes; they assigned the RuÀ Ru stretching band ν Ru À Ru to 327/333 cm À 1 in solid phase, but this band red-shifted to 312 cm À 1 in SERS spectra for [Ru 2 Ni(dpa) 4 Cl 2 ] 0/1 + at room temperature. [16,17] They suggested that both complexes on substrate gold nanoparticles were reduced by the metal nanoparticles to having [Ru 2 ] 4 + cores. The [Ru 2 ] 4 + core has a weaker RuÀ Ru bond than that of [Ru 2 ] 5 + .…”

Advanced Large-Scale Nanofabrication Route for Ultrasensitive SERS Platforms Based on Precisely Shaped Gold Nanostructures

“…Recent studies showed that turnover rates and selectivity of catalytic reactions can be strongly influenced by the shape of the NPs since their surface structures and active sites are tailored at the molecular level. [5] By means of versatile colloidal methods, a variety of shapes have also been reported so far, including the conventional 3D shapes (cube, tetrahedron, octahedron, decahedron, and icosahedrons) and 1D or 2D shapes (rod, wire, plate, disc, triangle, hexagon, tetrapods, bi-pyramid, and highly branched structures) [6][7][8][9]. Moreover, the cubical shape is the most well-known in terms of a stable anisotropic morphology in colloidal methods.…”

“…By means of versatile colloidal methods, a variety of shapes have also been reported so far, including the conventional 3D shapes (cube, tetrahedron, octahedron, decahedron, and icosahedrons) and 1D or 2D shapes (rod, wire, plate, disc, triangle, hexagon, tetrapods, bi-pyramid, and highly branched structures) [ 6 , 7 , 8 , 9 ]. Moreover, the cubical shape is the most well-known in terms of a stable anisotropic morphology in colloidal methods.…”