Stabilisation of gold nanoparticles by N-heterocyclic thiones

Abstract

Gold nanoparticles (Au-NPs) have been prepared using N-heterocyclic thiones (NHTs) as ligand stabilisers. These Au-NPs have been shown to be very stable, even in air, and have been characterized by a combination of several techniques (TEM, HR-TEM, STEM-HAADF, EDX, DLS, elemental analysis and H NMR). These nanoparticles are active in the catalytic reduction of nitroarenes to anilines.

Platinum nanoparticles stabilized by N-heterocyclic thiones. Synthesis and catalytic activity in mono- and di-hydroboration of alkynes

“…These Pt colloids are rather soluble in organic solvents such as THF and benzene, allowing recording their 1 H NMR spectra. As expected from previous results on gold-NHT NPs, 13 the very broad signals showed in these spectra are consistent with the presence of platinum nanoparticles stabilized with organic ligands (see ESI, Fig. S2, S5, S8, S11, S14 †).…”

“…Very recently, we have succeeded in introducing N-heterocyclic thiones (NHTs) as ligand stabilizers for gold NPs. 13 This success was due, in part, to the presence of a sulfur atom on the ligand that, beside forming a strong interaction with the gold surface, can adopt a resonant form with a negative charge on it that confers good coordinating properties to the NHT and a thiolate-like behavior (Fig. 1).…”

“…In addition, some of the advantages of these types of ligands are found on the simplicity of their synthesis, the easiness of tuning their steric environment and their tolerance to air and protic solvents, which facilitates considerably their handling or their use during the synthesis of the metal NPs. 13 Platinum has also an excellent affinity to sulfur based ligands, 7c-e with the paradigmatic example on the thiolate based platinum nanoparticles, 7 for which extensive utilization has been reported. Therefore, we have considered that NHTs could also be excellent ligand stabilizers for platinum nanoparticles.…”

1,1′,3,3′-Tetramesitylquinobis(imidazole)-2,2′-dithione

“…A variety of substituted imidazole-2-thiones have been synthesized and used as precursors for the generation of free N-heterocyclic carbenes (Kuhn & Kratz, 1993). Other uses for these types of molecules include the stabilization of gold nanoparticles (Moraes et al, 2017;Okamoto et al, 2006) and as ligands for metal coordination studies (Parveen et al, 2019). As part of our ongoing effort with bis(N-heterocyclic carbene) and its transitionmetal complexes (Tennyson et al, 2010), the title compound (1,1 0 ,3,3 0 -tetramesitylquinobis(imidazole)-2,2 0 -dithione) was synthesized and its single-crystal X-ray analysis is reported here.…”

Desenvolvimento de catalisadores bimetálicos de ouro e paládio para hidrogenações seletivas

“…46 Catalisadores de Au/TiO2 são muito ativos para reações de hidrogenação de anidrido succínico (SAN) para -butirolactona (GBL) um reagente importante para a síntese de pirrolidona e seus derivados, obtendo-se conversões de 99% e seletividade de 80%. 47 54 Diante destes fatos, muitos estudos têm sido relatados nos últimos anos sobre a eficácia de nanopartículas de ouro suportadas para reações de hidrogenação seletivas de moléculas orgânicas multifuncionais, tais como, na redução de compostos carbonílicos α,β-insaturados, 55,56 nitrocompostos, 57 alcadienos, 58 quinolinas, 59 semi-hidrogenação de alquinos, 60,61 70 A presença de uma camada orgânica na superfície das nanopartículas proveniente de estabilizantes utilizados na síntese, por exemplo, deve influenciar diretamente nas interações metal−substrato durante as reações catalíticas, dependendo da afinidade apresentada pelos ligantes à superfície, pode ocorrer inibição ou diminuição da atividade catalítica em função da dificuldade enfrentada pelos reagentes em adsorver nos sítios ativos da superfície. 70 Assim, quando necessário, os ligantes podem ser trocados ou removidos a fim de conferir novas propriedades e reatividades às nanopartículas.…”